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Topic: LPG Conversion for Gensets using small air cooled engines

Posted By: professor95 on 04/27/08 06:40pm

A few days ago, I was asked how I accomplished converting my Champion 40008 gasoline genset to run off of LPG, or propane. Rather than post this information on the existing 3,000 Watt Chinese Generator Info thread, it was agreed a new thread specifically covering LPG conversion should be started. Since the “Granddaddy Thread” had become so larger and diverse, containing literally hundreds of modification details, it is extremely cumbersome to find specific information within the three-yearlong running archives.

What we are attempting to do here is keep the topic strictly to LPG conversion and not deviate into sound abatement enclosures, rewiring or who has what sale going on. By keeping it specific, we will have an archival reference source that can be easily accessed by both present and future members.

My comments and experiences will hopefully be interspersed with questions and contributions from others detailing their own experiences with LPG conversion.

I’m going to get my part started with several separate postings, each detailing some aspect of the conversion. To get the ball rolling, here is posting #1:

The following article describes my method of converting a 6.5 HP, GX200 class gasoline engine, a GX390 class, and 10 HP Briggs & Stratton air cooled engine to run on propane (LPG). The methods in this article do not in any way imply compliance of the engine with EPA or CARB regulations after conversion. I cannot and do not warranty the safety, durability or success of the conversion. This article is intended ONLY to serve as a description of my steps to make a conversion on personally owned equipment and IS NOT intended as a step-by-step construction method for others to follow.

Any and all alteration that may be performed to equipment owned by individuals reading this article is strictly performed at their own risk with no liability associated with the author. Now that my lawyer is happier with my disclaimer, let's get to the real "stuff".

The common Chinese genset produces around 3,000 watts from a gasoline fueled engine that is basically identical to the popular Honda GX200. Gasoline carburetors used on the entire crop of Chinese gensets built around this engine are similar or the same in design.
I am of the opinion that all of these engines are easily and inexpensively capable of being converted to run on LPG and still produce the same horsepower and wattage as they did on gasoline.

For those who want a “turn key” system, US Carburetion, offers both low and high pressure kits to completely accomplish the conversion. They have overseen and/or preformed thousands of conversions and may be considered the "experts". Do not hesitate to consult their web pages for info as well.

I was not afraid to do a little work myself and reused a regulaqtor cast off from an old burned out gas Bar-B-Q grill. I also outsourced/built some of my valves and connectors and modified, in some of my conversions, the existing gas carb into a LPG mixer. By doing so I cut my cost over purchasing a complete conversion kit by as much as 75%.

I believe a little understanding of LPG is needed to safely accomplish the conversion.

LPG is commonly stored in metal cylinders under pressure. Since LPG (propane) turns from a liquid to a gas at 44 degrees below zero (boiling temperature) the pressure in the tank is necessary to keep the gas in liquid form.

The pressure right out of a propane cylinder will vary between 25 psi and 180 psi depending on ambient temperature. Some gas appliances are called “high pressure”.
These may include portable propane camp stoves, ovens, grills lanterns and the common propane torch used to solder and heat metals. These systems do not use a regulator between the propane tank and appliance.

Recreational vehicles use a low pressure propane system. To accomplish this pressure in the propane tanks is lowered via a regulator, usually attached at the tank, to no more than 10 psi. This pressure is consistent no matter what the outside temperature is.

Internal combustion engines such as the ones on the Chinese gensets need an even lower LPG pressure system supplying around ½ psi. These engines also need a variable volume of fuel and air, depending on the speed and load of the engine. To control this variable load, a vacuum demand regulator is required between the system’s low pressure regulator and the engine. These secondary lower pressure regulators are available from sources such as US Carburetion for around $60 in US funds. The tank regulator from a defunct LPG grill may be recycled, or the gas line currently on the RV may be tapped for the low pressure (7 to 10 psi) source of fuel. If the RV gas supply is tapped, a cut-off valve between the supply and the demand regulator is needed.

The OEM gasoline carburetor on the engine needs to be converted, or drilled, to work with LPG. While dual fuel methods are possible, the simplest method is to just simply adapt the current carburetor. I decided to acquire a second carburetor to accomplish the conversion, leaving the original intact should I ever want to restore the engine to the original fuel. The second carburetor need not be from the same type of engine so long as the carburetor will fit the mounting studs.

To accomplish the evolution from gasoline carburetor to propane mixer, the float bowl, float and needle are removed. The main jet in the center of the carburetor is also removed. These parts are discarded.

I needed to make what is known as a “load block”. This is nothing more than a valve between the output of the demand regulator and the mixer. The load block may be a regular gas ball valve (about $8 for a 3/8” gas rated brass ball valve at Home Depot) or a home made adjustable restrictor using a brass “T”. Stay away from valves made for water. Water valves can easily leak a gas like propane. I selected to make the adjustable restrictor with a brass “T”.

So far, this is what we have: A propane tank, a low pressure regulator attached to the propane tank (or the RV’s low pressure gas source), a “demand” regulator after the low pressure regulator. An adjustable “load block” coming out of the demand regulator which attaches via a hose to the input to the mixer.

This photo is for "show only". The actual conversion uses LPG rated hoses and clamps.

[image]

* This post was edited 04/27/08 06:50pm by professor95 *


Professor Randy T. Agee & Nancy Agee. Also Oscar, the totally ruined Dachshund.
2009 Cedar Creek 5th Wheel - 2004 Volvo VNL670 class 8 MotorHome conversion as toter.
Turbocharged, 12L, 465 HP and 1,800 ft. Lbs. of torque.



Posted By: professor95 on 04/27/08 07:53pm

Why consider a LPG Conversion?

So, you have a perfectly good, gasoline fueled, air cooled portable genset. Why in the world would you want to hack it up (relatively speaking) to run off of Propane?

These are some of the reasons that have recently been cited for making such a conversion.
  • Unlike gasoline, LPG does not degrade over time. Therefore, you always have a fresh, clean, water free fuel source – even after months or years of storage.
  • LPG will not evaporate from the carburetor fuel bowl and leave gummy residues to clog fuel jets like liquid gasoline.
  • LPG burns cleaner – supposedly better for the environment.
  • We do not pay high road or motor fuel taxes on LPG. Therefore, the cost per gallon is often lower than gasoline.
  • If dedicating the genset to a 5th wheel or travel trailer, you do not need a new fuel source. The genset gas tank can be removed and the RV LPG supply used.
  • When traveling, extra containers of gasoline are not needed. No slosh, spillage or evaporation. Also lower risk of fire compared to an atmospherically vented gas tank/container.
  • The LPG fuel source can easily be 30 or more feet from the genset allowing diverse installation opportunities.
  • For home back-up power use, large LPG tanks are available for long term power outages (my home tank is 300 gallons and buried in the back yard – my last fill up was $2.16 per gallon).
  • LPG converted engines will also run off of natural gas, making them great for areas with gas mains in a power outage.
  • Five gallon LPG exchange tanks are available at most home stores, convenience markets, Wal-Mart and gasoline stations. Most all larger campgrounds offer filling of larger LPG tanks.
  • Converted gensets are easily externally readjusted to compensate for altitude variations.
  • Contrary to some info, converted gensets DO NOT produce any less power than they did when burning gasoline.
  • Many of the small air cooled engines can be easily and inexpensively converted to tri-fuel. These conversions will run off of gasoline, LPG or NG. My GX390 home backup genset is converted in this manner as was my previous B&S genset.
  • A 5 gallon OPD style LPG tank will hold 4 gallons of liquid propane (now that’s a real oxymoron!). Enough fuel to run a typical GX200 class engine for over 24 continuous hours.


Go here for more info on LPG.


Posted By: professor95 on 04/28/08 04:47pm

In Part 2 we are going to discuss converting a GX200 class air cooled gasoline engine to run exclusively on low pressure propane, as available from a RV supply line or a conventional Bar-B-Q propane tank using a tank regulator. Keep in mind as we explore this part of the conversion that there are actually two regulators used in this system. There is one at the propane tank that drops the tank pressure to 7-10 psi of line pressure that supplies a second regulator. The second regulator is often referred to as the intermediate regulator or vacuum feed regulator. It is this regulator that controls the amount of propane being fed to the engine.

Unlike LPG tank pressure regulators, intermediate regulators are not easily found lying around and must be ordered from an authorized supplier.

US Carburetion is one source for the Garretson KN Series Regulators (Woodward manufactures an almost identical regulator). You can purchase from them just the regulator for slightly less than $50, or order what is called the type "A" Kit with clamps, hose, load block and fittings for around $157. If you select just the regulator, you can locally outsource the other parts and perhaps save a significant amount of money without comprimising safety.

These regulators are designed to work on engines that do not idle. Since the majority of Chinese built 3,000 watt class generators based on the GX200 engine are designed to maintain 3,600 RPM, these regulators are ideal. The KN regulator will follow varying load conditions from the engine and respond with the appropriate amount of LPG vapor. This would NOT be a good regulator for an engine that has an “eco-throttle” designed to bring the engine down to an idle when the load on the generator drops or ceases.

Taking a quick look at a conventional gasoline GX200 carburetor, we recognize that liquid fuel is retained in a float bowl at the bottom of the carburetor.

[image]

As air is drawn into the carburetor by the vacuum created inside the engine from an open intake valve and descending piston, a small amount of gasoline is siphoned out of the float bowl, through a main jet and into the engine. This siphoning is a result of the Venturi Effect associated with air flowing over a small tube inserted into the liquid gasoline bowl. The photo below shows a carburetor venturi after modification for LPG, but the tube position is still in the same location as it was for gasoline.

[image]

As air flow increases by opening the throttle butterfly, the lower pressure in the venturi increases the amount of gasoline drawn into the engine.

Propane, unlike gasoline, is released to an engine’s fuel system in vapor form. Therefore, the conventional float bowl found on gasoline carburetors is not needed. Additionally, the flow of LPG vapors into the engine in this conversion must be externally regulated. This flow is controlled by the KN regulator as a result of the pressure differential in the venturi of a modified carburetor.

The basic KN regulator comes with a ¾” pipe thread input fitting and a 3/8” thread output fitting. Adapters to fit the size of hose used can be made-up from black iron, nylon or brass fittings found in the plumbing section of a home store such as Lowe’s. Conventional fuel line gear clamps are used to secure the hoses (more on hoses later). The regulator needs to be mounted close to the existing carburetor and once again some simple brackets will need to be constructed from aluminum angle or flat bar stock.

At the input of the regulator you will need a valve known as a load block.

[image]

A simple in-line gas ball valve works well. Again, these are available at home stores for about $6.00. The one pictured was made from a brass “T” and stud to create a restrictor valve.

The KN regulator will have a button in the center called a primer.

[image]

Pressing the button supplies LPG vapor to the carburetor (actually, mixer in LPG systems) so the engine may be started. Think of it as the choke for LPG.

When I am able to write part 3, I will detail how to modify an existing GX200 gasoline carburetor into a mixer for LPG.

Even though this thread is starting off more like a blog than a forum group, please feel free to post any questions or comments as needed.

I, or some one else with similar interest and experience, will do our best to give answers.

* This post was edited 04/28/08 04:54pm by professor95 *


Posted By: huskyhauler on 09/13/08 01:00am

I have a Zongshen 13hp 9kw that we bought at Pep-Boys as a back up unit for the house. As we are very rural, it is not uncommon for us to lose power for 12-14 hours at a time. This is a bummer in -10 nights.

We did the Conversion, and noticed it ran quiter, used less fuel, and the exhaust EGT's dropped. To top it off, the oil stays clean, and the valves seem to hold adjustment longer. We can run off a 100lb tank for over 30 hours now. We always have our tanks filled to 24 gallons to avoid issues when the temp drops or rises. That works out to .8 gallons an hour vs the 1.1 on gasoline. Plus propane is 2.49 a gallon vs 3.69 for gas, and it stores easier. I figured I am able to dial the mixture in better to compensate for our altitude (6280').

Why manufactures dont offer morepropane gennies I will never understand. I would have gladly paid $100 more for the Propane genny vs the Gasser..

GREAT write up. Reminds me of all the fun I had when I did ours.. Takes the fear out of anyone who is intrested in doing it!!


Posted By: mowermech on 09/13/08 06:30am

Very well done write up, and nice job on the conversion.
However, Onan states that their 4.0 genset is derated to 3.8 KW when fueled by propane. General rule of thumb, they say, is a 10% reduction in maximum output.


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Posted By: professor95 on 04/29/08 10:26am

Part 3

Tools and materials need:

  • 7, 8, & 10 mm sockets and drivers
  • Narrow blade small standard screwdriver
  • 3/16” to 1/4" outside diameter aluminum, plastic or copper tube about 3” long
  • WD-40
  • Electric drill
  • Drill bit matching OD of tubing
  • File and fine sandpaper
  • JB Weld Quick Epoxy
  • Spray can of carburetor cleaner with “straw” on nozzle
  • Safety glasses
  • Appropriate barbed fitting as described in text
  • Possibly a small hack saw or tubing cutter


To begin the process of converting the existing gasoline carburetor from a small GX200 class Chinese genset engine, we first need to totally remove the carb from the engine.

  1. Start by removing the four bolts that hold on the gasoline fuel tank.
  2. Turn off the fuel petcock and completely remove the tank.
  3. Completely remove the air filter assembly.
  4. Closely note how the throttle linkage is attached to the carburetor and make a note of the placement of the throttle rod spring. These items will need to be returned to their exact original positions.
  5. Remove the two retaining nuts on the end of the carburetor, leaving the studs in the engine block.
  6. Slide the carburetor off the studs being careful not to tear the gaskets. If the gaskets stick, spray a little WD-40 to heavily coat them, wait a few minutes and they should gently release without damage.
  7. Lay the carburetor on an old towel or rag that you do not mind getting a little gasoline on.
  8. Remove the plastic choke lever
  9. Completely disassemble the carburetor. This includes using a small screwdriver to take the main jet out of the main jet seat.

[image]

All of the parts you removed will not be reused. Put them in a plastic bag for a friend – he may need them one day [emoticon].

The main jet seat now needs to be drilled out to accept the new fuel tube. I found a neat piece of aluminum tubing that was 3/16” OD. In searching my junk boxes I also found plated brass sections from a broken rabbit ear antenna, a stainless steel probe from a broken electronic meat thermometer, and pieces of hard plastic tubing from an old car’s vacuum lines that were the perfect size. 1/4" tubing can be used, but I prefer to keep it to 3/16”

Carefully drill out the main jet tube. Carefully means keep your drilling slow and straight.

[image]

Use the spray carb cleaner to wash out the tube after drilling. Be sure to wear safety glasses when spraying.

The end of your tube will need to be shaped so there is a 45 degree angle. Use your file and sandpaper to form the tube and clean off any rough edges. Clean the tube with spray carb cleaner after shaping.

[image]

The tube is inserted into the drilled hole. Position the 45 degree slope so the lower part is facing the intake and the higher part is facing the engine. The lower part should just barely rise above the bottom of the venture of the carb.

[image]

Mix up some JB Quick epoxy and glue the base of the tube to the main jet housing. DO NOT CUT OFF THE TUBE AS SHOWN IN THE PHOTO. Let it extend beyond the main jet housing until after the glue completely hardens. The glue will set in 10 minutes, but complete cure will take an additional several hours. Let it sit until the epoxy has cured.

[image]

Fill the remaining low speed jet hole in the carb with epoxy.

[image]

You have numerous options for the attachment of the LPG vapor tube that runs from the intermediate regulator. Two are shown below.

[image]

[image]

You will note in the photos I am using a clear plastic tubing. We will talk more about supply lines and hoses in PART 4 so hold off on making any final connections.

Reassemble the now converted carburetor-to-LPG mixer to the engine. The final product will look something like this:

[image]

[image]

In PART 4 I will discuss the tank regulator selection, gas supply tubing selection, testing for leaks and starting the engine on LPG for the first time.

I hope someone is reading this and finding it beneficial. It is sort of odd not to have any feedback or comments as the article develops.

Anyway, one more part left to write for the GX200 dedicated conversion and if intrest is there, we can expand to tri-fuel options and different engines.

If all of this do-it-yourslf stuff is too much, remember US Carb will sell a complete kit - even drill and convert your gas carb if you send it to them. They are the true pros, not me. I'm just a teacher and writer. Remember, just because it may seem like I know what I am talking about doesn't necessarily mean that I do! [emoticon]

- Randy, "Professor95"


Posted By: professor95 on 05/02/08 08:55pm

PART 4


About the only thing left to accomplish with our conversion of a GX200 class air cooled, gasoline engine to run off of LPG is the hose and high pressure regulator.

High pressure regulators attach to the bulk LPG or propane tank. These tanks are usually 5 gallon, or 20# portable and refillable tanks commonly called “gas grill tanks”. Of course, larger tanks such as the 7.5 gallon, 30# size are often found on recreation vehicles. Unfortunately, these tanks are not readily available as “exchange” tanks.

Some LPG appliances are known as high pressure and do not use a regulator at the tank. Small portable gas grills, lanterns, catalytic heaters, and camp stoves are all examples of appliances that work directly off of high pressure LPG supplies.

All of the appliances inside of a RV are LOW PRESSURE. Additionally, larger propane gas grills that are often used at home are most likely to be low pressure. These appliances will have a high pressure regulator that attaches directly to the tank. (The output from the regulator will be low pressure.) The exception is the RV that usually has double bulk tanks and uses a short pigtail hose to attach the tank(s) to a single regulator. Motor homes may have non-removable LPG tanks with a different style of regulator.

Bar-B-Q gas grill regulators are universally single stage regulators. They are factory adjusted to supply no more that 12 PSI of vapor at the output of the regulator – no matter how high the tank pressure may be.

RV regulators are often two stage regulators and may even have an automatic tank switch over that will exchange tanks when the pressure in one drops below a predetermined level. Even with the extra regulation stage and automatic switch over, these regulators still supply no more than 12 PSI of vapor to the output.

Most new regulators have an OPD (overfill protection device) fitting attached to the tank end. These fittings screw onto the outside threads of the tank valve. Older style regulators have POL (put-on-left) brass fittings that screw inside the threads of the tank valve. These fittings are tightened with a 7/8” wrench.

New mandated OPD tanks will accept either OPD or POL fillings, making the older style regulators useable (but not as convenient).

High pressure regulators recycled from cast off propane gas grills will work well for a small engine LPG conversion. The type that offers the best versatility will have a removable hose fitting on the outlet side. Those that have a pressed fitting will be more difficult to work with. Avoid repurposed regulators that have two outlets..

Of course, new regulators with tank fittings can be purchased for approximately $25 at home stores or Wal-Mart. You may need to purchase the hose as a separate item.

Regulators shown in the following photo:

[image]

#1 – OPD tank fitting, 8 foot long 5/16” LPG rated hose with ¼” NPT female fitting on hose end. This is a good regulator but you cannot easily change hoses due to the crimp connection at the regulator and a fitting that is not removable.

#2 – This regulator needs a tank fitting. It also has a “T” screwed into the output with two hoses. Cost of a new tank fitting and a single output fitting with a supply hose make this regulator undesirable – keep looking.

#3 – Has the old style POL tank fitting, but it will attach to new OPD tanks so this is OK. 6 foot 5/16” LPG rated hose with ¼” NPT female on end. A good regulator for a LPG conversion.

#4 – Another good regulator. Has OPD tank fitting and a barbed fitting for a hose connection at the outlet. This would be nice for making up a longer feed hose.

Feed hoses from the high pressure regulator longer than 8 feet really should be ½” inside diameter rather than 5/16” – which is standard on Bar-B-Q grills. The following web site will give you detail for hose sizes per kW of generator output.
http://www.engineeringtoolbox.com/propane-gas-pipe-sizing-d_830.html

LPG supply hose can be purchased from US Carb (as can regulators) made up with fittings or in bulk lengths that you must add fittings to. Check them out at http://www.propane-generators.com/hook-up_hoses.htm

Brass fittings, gear clamps and adapters can often be sourced locally at Lowe’s or Northern Tools.

You are possibly wondering if you really need LPG rated hose. I cannot tell you yes or no, but I can give you some info that will possibly help with your decision.

LPG is captured in the refining process from crude oil. You can find out all kinds of technical info about LPG vapor and tanks by spending some time at http://www.propane101.com/propanetanks.htm

LPG is less corrosive or prone to damaging the delivery hose than regular unleaded gasoline.

LPG pressures after the high pressure regulator are under 15 PSI. Hoses designed for unleaded gas on fuel injection vehicles typically operate at 60 PSI.

So does this imply that less expensive and readily available fuel hose designed for unleaded gasoline and fuel injection is a safe substitute for LPG certified hose?

I gave this question to an associate who recently retired as a chemical engineer with a major oil company. At first he just shook his head, opting for the safest and easiest answer. After he found out why I was asking the question his reply was, “You can basically use any hose you want, rubber or vinyl, as long as you can inspect the hose, protect it from damage and excess heat and check all fittings with a soap solution for leaks.” He went on to say, “Personally, I would spend the extra money for LPG certified hose since we have a tendency to neglect inspection and proper care of hoses – they should give an extra margin of safety.”

I elected to use UL certified LPG hose for my applications, even if it was considerably more expensive. I did use some lesser rated hose while testing different systems and set-ups.

Once all your connections are made from the tank to the high pressure regulator, and from the output of the high pressure regulator to the demand regulator, and from the output of the demand regulator to the modified carburetor (LPG Mixer), you are ready to conduct your pre-flight test.

SLOWLY turn on the LPG tank valve. Why slowly? Well, OPD tanks have a valve inside that will close off the vapor supply if the flow exceeds a specified level. On a dry hose start up, if you quickly open the tank valve, you run the risk of no flow. This is true for any OPD tank and appliance – including your RV.

Check carefully for leaks. You can use a 50:50 solution of dishwashing detergent and water in a spray bottle or you can go to the dollar store and get a big bottle of kid’s bubble blowing soap. Spray all connections and fittings and watch for bubbles to form. If you have a leak, fix it. If not, the next step is “take- off”.

With the load block about ½ open, press the prime valve on the regulator for about 2 seconds. You can hear the gas flow.

[image]

Try to start the engine (you do not need the choke). This may take several tries as there is air in the dry lines and we need to purge the system so you have pure LPG vapor. (Sort of like trying to get a water heater running after a tank exchange on your RV.)

When the engine starts, it may run rough or stall. Adjust the load block until the engine runs smoothly. If you change altitude, you may need to readjust the load block – otherwise there is no need to readjust.

To shut down the engine, the preferred method is to cut off the LPG gas supply rather than flip the kill switch. You can do this at the tank, or an optional cut off valve. For the LPG generator I have on my RV, which draws fuel from the RV’s LPG high pressure regulator and supply lines, I have a 12 VDC gas solenoid valve that shuts off the vapor supply to the demand regulator.

[image]

You should now have a clean(er) burning engine with no wet fuel to wash oil from the cylinders, cleaner crankcase oil and a fuel with a long term storage ability that is always ready to go when you need it.

I guess our next discussion will be how to convert engines other than the GX200 class and options for tri-fuel operation. I currently have the tri-fuel option on my GX390 class engine spinning a 7,500 watt generator for my home back-up system.

* This post was edited 05/02/08 09:11pm by professor95 *


Posted By: professor95 on 05/02/08 08:58pm

Todd Barney wrote:

Your students learn what you teach them, don't they?


The ones that take the time to come to class do. Unfortunately, too many believe attendance is not necessary.

Thanks for the kind comments.


Posted By: 'nawlins on 09/12/08 05:57pm

Thank you for your time and effort on your conversion article!

I have a real GX200. Due to a very poor experience with US Carbs, I ran my generator with natural gas, thru a ball valve no regulator, for 36 hours during Hurricane Gustov.
I fired up on gasoline then switched over to NG after load stabilized for two freezers and lights / fans. This worked fine but must be attended to for obvious safety violations.

The GX200 loves NG but with far lower BTU than propane/gasoline, I would think that de-rating of maximum wattage would be in order. When I acquire a proper set up I’ll load test NG/gasoline.

Anyone wanting a Type C Tri-Fuel Natural Gas, Propane, and Gasoline Kit $187.00 for the (genuine) GX200, save your money. The kit will not allow you to re-fit stock air cleaner with choke keeper assembly. I ate nearly $30 in shipping cost which I could have put to a second carburetor. Of course, the kit may (?) work fine for the clones as your air filter appears to be a different configuration.

I found a source for $36 carburetors, clones; http://www.psep.biz/store/honda_small_engine_carburetor_complete.htm#S520718 that will allow me to set up a carburetor along the lines of your article.

I would love to go a tri-fuel set up but don't want to give up the stock air cleaner/gas carburetor. A retrofit venturi adapter may end up costing as much as a clone carburetor?

Again, thanks for your article!

Mike


Posted By: 'nawlins on 09/13/08 05:43pm

Hurricaner wrote:

Ya, whats the deal with the power reduction? Obviously there is less BTU content in a gallon of propane but the manufactures I have seen all derate there propane gens but the conversion guys say you don't have too. The truth is????

Sam


I would have to go with the manufactures. The Kholer whole house dual fuel generator from Lowes plainly state this. I always thought that the generator used more fuel to make up the BTU difference.

Anyone load test?


Posted By: HedoTravelers on 09/13/08 06:36pm

Propane will give you longer range and needs less space for fuel storage tanks. But, it has a lower energy content (it has lower octane, less power) compared to gas so more fuel is required to go the same distance.


Respect,
Brent


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"Wherever you go, there you are"



Posted By: mike4947 on 09/13/08 06:52pm

Hurricaner wrote:

Ya, whats the deal with the power reduction? Obviously there is less BTU content in a gallon of propane but the manufactures I have seen all derate there propane gens but the conversion guys say you don't have too. The truth is????

Sam


It actually depends on the engine/generator combination. Some genset builders use one engine for several different ratings of gensets. Say 1000, 1200, and 1500 watts. Run on propane this engine will have less power but would only effect the gensets where the reduced power is less than the generator needs to produce it's maximum power.

In the majority of gensets though the engine's output is designed to the needs of the generator/inverter and converting to propane does have an effect on the output amperage/wattage.


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Posted By: joe b. on 09/13/08 09:00am

Propane conversions can produce the same power as with gasoline. However there is no free lunch, as they say. To get the same max output, I find I have to burn slightly more propane than I would gasoline. For a given period of time at a given load, if it takes 100 gallons of gasoline, with propane I will use approx 110 gallons. Still by far cheaper to buy 110 gal of propane than to buy 100 gal of gasoline. Here in Stuart Florida, currently, 110 gal of propane costs $247.50 and 100 gal of gasoline is about $365, a saving of over $100.
During the last 3 hurricanes here in south Florida, Francis, Jean and Wilma, we were without power for about 10 days each. I put about 240 hours on my generators with each storm, so for me, propane is the best way to go. I find it easy to store and have available to use.
I am looking forward to the next "Prof" article on how to convert over to using either propane or gasoline. On my current generators I bought the kit from US Carb but would like to do more of a "self mod" of my new 8 KW continues max, B & S generator that I have yet to convert. Prof, a great write up that is easy to understand. Thanks,
On the ranch in Oklahoma where I grew up much of our equipment, trucks, tractors, pumps, etc. were propane fueled, mainly due to the price difference with gasoline or diesel. It is a great all around fuel IMHO.


joe b.
Stuart Florida
Formerly of Colorado and Alaska
2016 Fleetwood Flair 31 B Class A w/bunks
www.picturetrail.com/jbpacooper
Alaska-Colorado and other Trips posted
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Posted By: Hurricaner on 09/13/08 09:34am

Ya, whats the deal with the power reduction? Obviously there is less BTU content in a gallon of propane but the manufactures I have seen all derate there propane gens but the conversion guys say you don't have too. The truth is????

Sam


Sam & Kari
Hurricane, Utah


2019 Winnebago Sightseer 33C


Posted By: wwest on 09/13/08 10:22am

Mill the head to get a slightly higher compression ratio with LPG.


Posted By: professor95 on 09/15/08 06:47am

It is nice to see some renewed interest and commentary on this thread. I am glad to know it did not fall to the bottom of the pile.

Anyway, about the gennys that produce less power on LPG.....

Back on the 3,000 Watt Chinese Genny forum I have written many, many times the reminder that "You can neither create nor destroy energy, only convert it."

In a bi-fuel or tri-fuel genny it is true that if you introduce the same amount of a fuel that has a lower BTU/HR than gasoline you will produce less power at the output - provided the efficiency of the engine remains constant. Note the two italized terms same and efficiency.

Ironically, LPG and LNG allow for a higher efficiency in a small engine for the same reason electronic fuel injection increases efficiency in a larger automobile engine. Carburetors are not known for extreme efficiency since they must vaporize a liquid in a rather precarious air/fuel ratio. When using LPG or LNG the fuel does not change to vapor in the carburetor - it is introduced to the fuel system as a vapor. Thus, efficiency increases.

Small engines are capable of utilizing higher volumes of air and vapor than they typically use with liquid gasoline. Therefore we can and do generate the same (maybe more) power from the engine on LPG as we did on gasoline.

Then why does an Onan, Kohler, etc. advertise less power on LPG? Simple - they provide less air/fuel on LPG.

Next question. Why don't they increase the air/fuel on LPG to get the same power? Answer - EPA certification. In the mess that defines EPA requirements for these engines there is some language that restricts the pounds per hour of fuel introduced for a specific displacement and air/fuel ratio regardless of the type of fuel being used. Thus, if 4 lbs per hour is the max for a 200cc engine using gasoline, the same is true if the same engine is using LPG.

But those restrictions apply only to the manufacturing end. On the consumer end we are bound by sniffer test that measure what is in the exhaust. Therefore, we can increase the amount of LPG/air for a given displacement engine so it will produce identical power as gasoline and still NOT exceed EPA (even CARB) sniffer levels.

Bottom line - Doing your own conversion can = identical power.

Several months back I said I would share how to make a tri-fuel set-up. Guess I need to do that!

Method one is to purchase a add-on ventrui that is placed between the carburetor and intake (in some cases before the carburetor works as well). Here are some photos of a typical ventrui that I used on a 10HP Briggs & Stratton engine - both assembled and disassembled so you can see how they are made.

[image]

[image]

[image]

The other option is to add a LPG input to the ported vacuum side of the carburetor by carefully drilling a hole in the side of the carburetor so that you can insert a brass tube, epoxy it on securely and run a hose to the LPG/vacuum regulator. The latter method is the one I am currently using on my 13 HP GX390 engine to allow it to run on gasoline or LPG. Owning a mini-metal lathe helped to create the required brass tube of an appropriate diameter for both the intake and hose diameters.

[image]

Each of these systems use the same demand regulator that was used in the aforementioned articles.

[image]

The only real problem with drilling into the carburetor to add an additional input is avoiding damage to other parts of the carburetor or compromising the movement of the throttle plate. The smaller the carburetor, the more difficult it becomes. It can be done on the small carb used on the GX200 engines, but extreme care is needed. I have NOT drilled a port into one of these carburetors but feel the side shown below would be the best drilling point.

[image]

As previously described, I am currently running two tri-fuel gennys. One with a GX390 engine the other with a GX200 engine. Both perform flawlessly and there is absolutely NO observed reduction in power produced. When Hanna came to town a few weeks ago we lost power. With a 300 gallon in-ground LPG tank close by I did not even stop to think about how much fuel I had or when I might need to refill.

Nice!


Posted By: 'nawlins on 09/15/08 07:50am

Thanks again for your time. As for the threads for less power using vapor fuel..WOW! Searching the "net" and blank statements from manufactures has had me wanting.

May I ask if your air cleaner was the same on your GX390 as the Honda GX200? If so, then you rolled your own air filter? I would like to keep my stock air filter/choke keeper but don't have a mini lathe [emoticon]
At this point the $36 dollar clone carburetor is looking like a good option until you get your, lol, kits ready for sale?

When time permits please post your details on where and what size tube you used for your tri-fuel option. I'm using a GX-200 and plan on using Natural Gas unless using the pop-up with propane.

Regards, Mike

professor95 wrote:

It is nice to see some renewed interest and commentary on this thread. I am glad to know it did not fall to the bottom of the pile.

Anyway, about the gennys that produce less power on LPG.....

Back on the 3,000 Watt Chinese Genny forum I have written many, many times the reminder that "You can neither create nor destroy energy, only convert it."

SNIP to save sapace

As previously described, I am currently running two tri-fuel gennys. One with a GX390 engine the other with a GX200 engine. Both perform flawlessly and there is absolutely NO observed reduction in power produced. When Hanna came to town a few weeks ago we lost power. With a 300 gallon in-ground LPG tank close by I did not even stop to think about how much fuel I had or when I might need to refill.

Nice!



Posted By: professor95 on 09/15/08 08:20pm

'nawlins wrote:

Thanks again for your time. As for the threads for less power using vapor fuel..WOW! Searching the "net" and blank statements from manufactures has had me wanting.

May I ask if your air cleaner was the same on your GX390 as the Honda GX200? If so, then you rolled your own air filter? I would like to keep my stock air filter/choke keeper but don't have a mini lathe [emoticon]
At this point the $36 dollar clone carburetor is looking like a good option until you get your, lol, kits ready for sale?

When time permits please post your details on where and what size tube you used for your tri-fuel option. I'm using a GX-200 and plan on using Natural Gas unless using the pop-up with propane.

Regards, Mike



No kits will be forthcoming. US Carb has most anything you will ever need for LPG conversion.

Trying to remember..... I had a brass fitting with barbs for a 1/4" ID hose. I believe it had a 3/16" ID. I turned the 1/4" NPT end down to 1/4" OD and drilled a 1/4" ID hole in the GX390 carb. Same thing could be accomplished with a piece of 1/4" OD copper tube or brass pipe. US Carb will insert a similar port for tri-fuel if you send them your carb. I believe the price is around $50 and also includes a new ported vacuum port for a vac fuel switch.

I only reused the stock air filters - never needed to make anything different. The one on the GX390 is a larger version of the GX200 filter.

If you are drilling a port on the GX200 carb, go as large as space allows. You can always compensate for too large of a tube by adjusting the load block on the demand regulator. I have NOT added a tube to the smaller carb so can't tell you for sure if 1/8" ID would get enough vapor into the engine. It would be right on the edge if it does.

All of this is amazingly simple to accomplish if one just follows common sense rules for safety to avoid fire and explosions outside of the engine. Just remember, unlike gasoline, LPG is under pressure and all tubes, joints and fittings need to be leak proof. Additionally, do NOT even think about using the high pressure side of a LPG tank as a fuel source. Even when working with the low pressure side, absolutely NOTHING higher than 1 PSI should be introduced into the engine.

The people who get hurt using LPG are the same folks who light a match to see how much gasoline is in the tank or hold a flame over a charging battery to see if the electrolyte is boiling.


Posted By: ElectricMayhem on 09/22/08 08:37pm

Thank you so much, Professor, for your informative posts. I bought a Champion 40015 generator as a result of reading the other thread, and now I plan to convert it to run off my house's NG barbeque connection for use during emergencies. Is the method the same for such a setup, or is the regulator different?


Posted By: ElectricMayhem on 09/26/08 08:24pm

It seems that the regulator is the same given the existence of LP/NG kits at US Carb. I am afraid that an amateur homemade epoxy seal on the carb might not hold in such a high vibration environment so I think I might order a US Carb kit.


Posted By: Airmaxx23 on 09/30/08 07:56am

I have a Champion 3000 watt (model 40026) generator and I'm thinking of doing the US carburetion type "c" conversion but I'm concerned about the stock air filter being in the way. Has anyone done a conversion with any of the Champion 3000 watt generators who can chime in on this? Thanks


Posted By: tom1984 on 09/30/08 03:49pm

Quote:

Bottom line - Doing your own conversion can = identical power.


The reason for less power on propane is, the compression is set up for gasoline. If you increase the compression to take advantage of propanes 104 octane... you could get as much or maybe a little more power out of the engine... but then it would not run well on gasoline. But unless you are running the gen at max wattage, you would never notice the difference.


Posted By: professor95 on 09/30/08 06:35pm

tom1984 wrote:

Quote:

Bottom line - Doing your own conversion can = identical power.


The reason for less power on propane is, the compression is set up for gasoline. If you increase the compression to take advantage of propanes 104 octane... you could get as much or maybe a little more power out of the engine... but then it would not run well on gasoline. But unless you are running the gen at max wattage, you would never notice the difference.


Interesting analysis. Something else that is interesting; the trend now is to NOT rate small engines by horsepower. Displacement, torque or KW are the new ratings. I imagine it will take a while to catch on across the industry, but it is starting. If displacement shakes out to be the rating standard, it will not make a flip what fuel an engine uses as far as giving an advertised power. A 200cc engine will be a 200cc engine - period.


Posted By: professor95 on 09/30/08 06:56pm

Airmaxx23 wrote:

JB Weld is amazing...I've actually used it on an ATV engine that ended up with a small crack from having the chain come off and hitting the crank case. It never leaked oil again.


OK - This is not about propane conversion, but I gotta share this:

Back in '88 I had a '72 VW Super Beetle. In my haste one night I managed to get a spark plug cockeyed into the left front cylinder head and stripped out the threads. The next day on the way to work, the plug blew out of the engine.

Back home I was faced with having to drop the engine, pull the head and put in a helicoil; a rather time consuming task I prefered not to do.

So, I said, "What the heck - I'll just put a blob of JB Weld (not JB Quick) on the threads of a new plug, shove it in and let it sit for 24 hours".

I guess I put another 10,000 miles on the engine with the spark plug glued in.

I sold the car to a kid who was a buddy of my youngest son. He drove it another two years before he ran it into a tree. The spark plug never came out.

What would I do if I had needed to change the plug? Well, I guess I would have just put a wrench on it and cranked it loose, then JB Welded in a new one.

Amazing stuff!

A true story.

We now return to our regularly scheduled propane conversion programing........


Posted By: sjhanksaz on 09/30/08 08:04am

My Honda EB 3000 has a "similar problem" it think. Right now the cage is about 2" from the air filter cover. I wonder if I put on one of those kits if I would be able to get the cover off.

I think one guy mentioned that I could cut and modify the cage but it would be nice not to have to do that


Posted By: professor95 on 09/30/08 08:41am

ElectricMayhem wrote:

Thank you so much, Professor, for your informative posts. I bought a Champion 40015 generator as a result of reading the other thread, and now I plan to convert it to run off my house's NG barbeque connection for use during emergencies. Is the method the same for such a setup, or is the regulator different?


I believe it is the same. Just be sure you have a low pressure regulator in your NG system. If there are any questions about the regulator, call one of the techs at US Carb, they are extremely knowledgeable.


Posted By: professor95 on 09/30/08 08:52am

Airmaxx23 wrote:

I have a Champion 3000 watt (model 40026) generator and I'm thinking of doing the US carburetion type "c" conversion but I'm concerned about the stock air filter being in the way. Has anyone done a conversion with any of the Champion 3000 watt generators who can chime in on this? Thanks


It will be close with the type "c" kit using the ventui add on. You will not be able to easily get the cover off the air filter due to it being right against the frame tubing. You put just the inside stud into the engine block, slip on the carb, ventrui and air filter, turn the entire unit upward so you can get the outside stud in and squeeze real hard. The longer studs needed are metric, not SAE, so grabing some threaded rod stock at HD doesn't work. When I tried it this way I had to make studs by brazing some threaded stock onto an existing stud and then clean it up in a metal lathe. Not something most folks have the tools to accomplish.

IMHO, buy an extra carb and drill it as in my posting. If you ever need to go back to gasoline, it is a 10 minute job to swap the carbs.


Posted By: professor95 on 09/30/08 09:00am

ElectricMayhem wrote:

It seems that the regulator is the same given the existence of LP/NG kits at US Carb. I am afraid that an amateur homemade epoxy seal on the carb might not hold in such a high vibration environment so I think I might order a US Carb kit.


Well, I guess it could. But consider this: I am a JB Weld beliver. I have used the stuff to repair cracked rototiller engine blocks, glue a spark plug into an old VW cylinder head, patch a leak in a gas tank, and fix a hole in my tractor's radiator. It held up in all of those situations. I would not be without the stuff - I always keep it on hand. Other brands of epoxy glues and fillers I have tried did not hold up as well.


Posted By: Airmaxx23 on 09/30/08 10:41am

JB Weld is amazing...I've actually used it on an ATV engine that ended up with a small crack from having the chain come off and hitting the crank case. It never leaked oil again.


Posted By: 'nawlins on 10/06/08 09:18am

I would second the extra carb which is the way I went. The GX200 clone carb was $36. The US Carbs Venturi adapter was more expensive and did not allow for stock air cleaner/choke on my GX200/Pramac genset. I want to use natural gas as well, modding the small GX200 carb for Tri-fuel would be tricky, if done as prof95's GX mod.

http://www.rv.net/Forum/index.cfm/fuseaction/thread/tid/21337191/gotomsg/21892060.cfm#21892060

professor95 wrote:

Airmaxx23 wrote:

I have a Champion 3000 watt (model 40026) generator and I'm thinking of doing the US carburetion type "c" conversion but I'm concerned about the stock air filter being in the way. Has anyone done a conversion with any of the Champion 3000 watt generators who can chime in on this? Thanks


snip

IMHO, buy an extra carb and drill it as in my posting. If you ever need to go back to gasoline, it is a 10 minute job to swap the carbs.



Posted By: tom1984 on 10/06/08 05:23pm

Quote:

Interesting analysis. Something else that is interesting; the trend now is to NOT rate small engines by horsepower. Displacement, torque or KW are the new ratings. I imagine it will take a while to catch on across the industry, but it is starting. If displacement shakes out to be the rating standard, it will not make a flip what fuel an engine uses as far as giving an advertised power. A 200cc engine will be a 200cc engine - period.


Motors have always been measured in torque, that's what dynamometers measure ...horsepower is just a math formula...HP = rpm x T(torque)
5252(constant)

KW is a European thing like the metric system ...they have always done it that way 1 HP = .7456 KW

I do not believe any quality engine maker will ever get away from some sort of power rating...because they want you to know that their 200cc motor puts out more power than brand x 200cc motor


Posted By: professor95 on 10/06/08 07:05pm

tom1984 wrote:



I do not believe any quality engine maker will ever get away from some sort of power rating...because they want you to know that their 200cc motor puts out more power than brand x 200cc motor


They already have dropped HP ratings. Pick up a power equipment catalog like Northern Tool and Equipment. You will find most small engines, including Honda, no longer have HP ratings. Northern adds the statement "historically rated" for HP.

Briggs & Stratton has also dropped HP ratings and is now exclusively using torque.

This is a major change from what we have become accustomed to.


Posted By: Old & Slow on 10/07/08 06:49am

tom1984 wrote:

Quote:

Interesting analysis. Something else that is interesting; the trend now is to NOT rate small engines by horsepower. Displacement, torque or KW are the new ratings. I imagine it will take a while to catch on across the industry, but it is starting. If displacement shakes out to be the rating standard, it will not make a flip what fuel an engine uses as far as giving an advertised power. A 200cc engine will be a 200cc engine - period.


Motors have always been measured in torque, that's what dynamometers measure ...horsepower is just a math formula...HP = rpm x T(torque)
5252(constant)

KW is a European thing like the metric system ...they have always done it that way 1 HP = .7456 KW

I do not believe any quality engine maker will ever get away from some sort of power rating...because they want you to know that their 200cc motor puts out more power than brand x 200cc motor


From a novice point of view the idea of 'one size fits all' is crazy.
For a Champion rated at 6.5 hp (rightly or wrongly) equals 4846 watts. Based on what standard or quality of genhead? Maybe as a novice I am completly out of my league. Guess I'll have to go with Prof'...The proof is in the pudding. 2800 watts? for a Champion C46540 or 40008. Even on the use of LPG for fuel.


Posted By: professor95 on 10/07/08 07:27am

Old & Slow wrote:

From a novice point of view the idea of 'one size fits all' is crazy.
For a Champion rated at 6.5 hp (rightly or wrongly) equals 4846 watts. Based on what standard or quality of genhead? Maybe as a novice I am completly out of my league. Guess I'll have to go with Prof'...The proof is in the pudding. 2800 watts? for a Champion C46540 or 40008. Even on the use of LPG for fuel.


It would be easy to get confused on common ratings like KW if used for both engines and generator output. You see, they would actually be two different things with the same name!

A "traditional rating" of 6.5 HP would equal 4846 KW at the output shaft of the engine. It would NOT indicate the output of an attached generator.

While the power or work an engine can accomplish is significant in generator output, the efficiency and design of the generator is what will determine just how much of the power generated by the engine can be converted to usable electrical energy.

Let's use the "old" numbers a minute to explain:

If the engine is (correctly) rated 6.5 HP and is driving a generator head that is (correctly) rated for 3,000 watts continious output. The formula tells us 746 watts is equal to 1 HP related to the actual amount of work that can be done by a machine. Thus, 3,000 watts / 746 watts = 4.02 HP.

Where did the difference of almost 2.5 HP go? Mostly into heat energy that was not used to produce electricity.

You may have noted I added the word "correctly" in parens to my above statement. My belief is that these so called 6.5 HP engines are not truly 6.5 HP. It is all part of an advertising game.....


Posted By: 'nawlins on 10/26/08 06:45pm

I noticed my neighbor using the new Torque ratings, used by Briggs, trying to get lawn mower to start. I would venture he was really torqued after twenty minutes.

"Familiar Horsepower Rating No Longer Standard" by the washingtonpost.com

http://www.washingtonpost.com/wp-dyn/content/article/2008/02/15/AR2008021501732.html


Posted By: 'nawlins on 10/26/08 09:00pm

ElectricMayhem wrote:

It seems that the regulator is the same given the existence of LP/NG kits at US Carb. I am afraid that an amateur homemade epoxy seal on the carb might not hold in such a high vibration environment so I think I might order a US Carb kit.


I've been short of time with work so I ordered the $156 type A to use with a clone carb to keep original for gas.

For the second time I'm rather disappointed with the "kit". The load block was really homemade looking, not at all as pictured. The fuel tube was glued(!) to the re-tapped brass center jet tube adapter. This had broken loose so I just brazed it to the fitting. This has to be cut to length for the 1/3 to 1/4 height suggested. A tube of RTV silicone is included to glue all this stuff together and stop vacuum leaks. So, silicone or JB weld, your choice[emoticon]

All in all the Professor's direct feed tube hook up would have been the way I should have gone if time allowed, which at this point, HAS cost me more time.

A note on the angled fuel spud tubes; if it has to be cut, to adjust length, instructions say to just cut straight! "It makes no difference in fuel delivery" So why send kits with the angled fuel tube? Mine was sent straight cut.


Posted By: Old & Slow on 10/27/08 06:46am

'nawlins wrote:

ElectricMayhem wrote:

It seems that the regulator is the same given the existence of LP/NG kits at US Carb. I am afraid that an amateur homemade epoxy seal on the carb might not hold in such a high vibration environment so I think I might order a US Carb kit.


I've been short of time with work so I ordered the $156 type A to use with a clone carb to keep original for gas.

For the second time I'm rather disappointed with the "kit". The load block was really homemade looking, not at all as pictured. The fuel tube was glued(!) to the re-tapped brass center jet tube adapter. This had broken loose so I just brazed it to the fitting. This has to be cut to length for the 1/3 to 1/4 height suggested. A tube of RTV silicone is included to glue all this stuff together and stop vacuum leaks. So, silicone or JB weld, your choice[emoticon]

All in all the Professor's direct feed tube hook up would have been the way I should have gone if time allowed, which at this point, HAS cost me more time.

A note on the angled fuel spud tubes; if it has to be cut, to adjust length, instructions say to just cut straight! "It makes no difference in fuel delivery" So why send kits with the angled fuel tube? Mine was sent straight cut.



Thanks for the post.
I'm on to this LPG thing like white on rice. The "Boon Plan" let's go. I hope Prof' or someone will give us a lead to finding ALL the necessary fixin's to retro our genny to LPG. Just where do we find the 'load block'? with primer?


Posted By: 'nawlins on 10/27/08 08:46am

Old & Slow wrote:



SNIP


Thanks for the post.
I'm on to this LPG thing like white on rice. The "Boon Plan" let's go. I hope Prof' or someone will give us a lead to finding ALL the necessary fixin's to retro our genny to LPG. Just where do we find the 'load block'? with primer?


US Carbs sells the Garretson FN regulator for around $50, check the site. The "load block" can be a 3/8" gas rated gate valve as per the Professor's text. US Carb may sell their load blocks on special order, call them. I ordered a second carb, $36, from Pat's engines on line.

Or, you can order the kit from US Carb, as you know. Everything revolves around how handy you may be with tools. US Carb will do the conversion for you if you send them a carburetor. I think they quoted me around $40 labor, again, please check their site.


Posted By: 'nawlins on 10/30/08 06:23pm

I found time today to run my newly converted NG GX-200 generator with our 13.5 BTU Duo-Therm as load. No problems, runs great, 124vac@61hz.

Operation is much easier now that I have a regulator and load block than earlier post using suicide hose and none of the above. When load changes, GX200 quickly adjusts without the faint puff of smoke when running gasoline. Spark screen and plug look very clean after the 4 hour load test.

I’ll cobble my propane hoses in order when time permits to log the dual fuel load block changes for any future hurricane usage.

I would love to get my hands on a thermal meter and exhaust analyzer to double check my “toward” lean run settings with the load block as per US Carb instructions.

Question;

If 10245.54 BTUs equals 3KW, the cooler running engine comments over burning gasoline has me a bit puzzled. My generator, under load, felt to be running just as hot as when running gasoline. How does a heat engine put out same power with less heat?

Cheers


Posted By: Old & Slow on 10/31/08 05:23pm

It's great you took the time to report on the LPG conversion. For me, this conversion has been on my mind for a long time. Failure to follow through and learn all the parts and how they work together is evident from my past posts. Several questions. Is it your finding then, no loss of power? Is it easy to start? Do you need to always re-adjust the load bank? From what I understand the choke is no longer needed? If I use a unit with electric start, will it need the electric primer as reported? Any other info' will be appreciated.

* This post was edited 10/31/08 05:30pm by Old & Slow *


Posted By: 'nawlins on 11/03/08 02:39pm

Old & Slow wrote:

It's great you took the time to report on the LPG conversion. For me, this conversion has been on my mind for a long time. Failure to follow through and learn all the parts and how they work together is evident from my past posts. Several questions. Is it your finding then, no loss of power? Is it easy to start? Do you need to always re-adjust the load bank? From what I understand the choke is no longer needed? If I use a unit with electric start, will it need the electric primer as reported? Any other info' will be appreciated.


I have not noticed any loss off power using NG which has the lowest BTU of the common gaseous fuels, no? It runs the Duo-Therm without any signs of overload.

Getting started, the first time, was a chore with rope start. As stated, "all engines are different" in the US Carb manual. The initial load block was right, 3 turns out, but my regulator was a bit stiff so my GX-200 wants 3/4 choke. This starts it hot or cold first pull.

Your electric start should be no problem. The regulator has a primer button that may work fine for you along with choke if needed. I'm sorry, the electric primer I'm not familiar with. However, you may want to call US Carbs tech number to get a quote and kit that fits your engine and to ask about what is required.

Good Luck!


Posted By: Old & Slow on 11/03/08 04:11pm

Thanks 'nawlins,

Your report supports all the findings of Prof' on 'no loss of power'~ Many want to disagree because of the lower BTU rating of NG/LPG. Prof' says, the proof is in the pudding. No loss of power. The load block info' is helpful. On the question of the choke being needed, that was pretty clear as Prof' has a retro electro choke used with electric starting. I was hoping it could be started without the choke. Nice to know after the first start you had no problem. On the first start did you use the primer?


Posted By: Old & Slow on 01/12/09 11:54am

'nawlins wrote:

ElectricMayhem wrote:

It seems that the regulator is the same given the existence of LP/NG kits at US Carb. I am afraid that an amateur homemade epoxy seal on the carb might not hold in such a high vibration environment so I think I might order a US Carb kit.


I've been short of time with work so I ordered the $156 type A to use with a clone carb to keep original for gas.

For the second time I'm rather disappointed with the "kit". The load block was really homemade looking, not at all as pictured. The fuel tube was glued(!) to the re-tapped brass center jet tube adapter. This had broken loose so I just brazed it to the fitting. This has to be cut to length for the 1/3 to 1/4 height suggested. A tube of RTV silicone is included to glue all this stuff together and stop vacuum leaks. So, silicone or JB weld, your choice[emoticon]

All in all the Professor's direct feed tube hook up would have been the way I should have gone if time allowed, which at this point, HAS cost me more time.

A note on the angled fuel spud tubes; if it has to be cut, to adjust length, instructions say to just cut straight! "It makes no difference in fuel delivery" So why send kits with the angled fuel tube? Mine was sent straight cut.



Still have a desire to retro to LPG but from the sound of Sal, I da know. Don't think USCARB tells the complete story? Using a genny in a factory genset compartment almost demands using LGP only, for safety reasons.


Posted By: Old & Slow on 06/15/09 05:54am

Update,

After my conversion with the KN from US Carb and the home brew fuel block designed by the Professor (before the carb) all is well that ends well. With the Electric Start added to me C46540, just the primmer button held down and the twist of the key start, she is up and running. No loss of power that I know about.

Floyd


Posted By: Snowman9000 on 12/16/09 07:55pm

Some propane conversion highlights of the giant thread on Chinese gensets, that are not previously mentioned here:

Update on DIY conversion parts

Next update: Carb adapter & load block

Or maybe not...

Youtube tri-fuel Yammie 4500

Youtube tri fuel Honda 2000

Youtube Honda 1000, maybe the most informative look at the hookup.

* This post was last edited 12/16/09 08:51pm by Snowman9000 *


2014 Sunseeker 2300 Class C (Chevy 4500)



Posted By: olephart on 06/25/11 07:40pm

Thanks Professor. Ya know there is nothing really new anymore. I saw a carb for a Honda 2000 that was drilled in the top by a conversion company and went from there.

Initially, I was looking at the side that has the CPE lettering cast in the carb body. I believe you speculated that it would be possible to drill in that area. I think that would work, too. Mostly a matter of which location provides the best hose routing.


Posted By: professor95 on 06/25/11 06:12pm

It looks fantastic! A job well done for sure. Drilling from the top is a new option. I really like it.

- Prof95


Posted By: Old & Slow on 02/04/11 11:02am

Old & Slow wrote:

Update,

After my conversion with the KN from US Carb and the home brew fuel block designed by the Professor (before the carb) all is well that ends well. With the Electric Start added to my C46540, just the primmer button held down and the twist of the key start, she is up and running. No loss of power that I know about.

Floyd



Update to the update. The fuel block designed by the Professor worked like a charm. Using this method for the retro made it easy to return to mogas. Easy way (but more exspensive) would be to buy the complete kit from USCARB.com For ES & remote control you can get the solenoid primer KN valve from uscarb , just a little more cost. This makes one sweet genny. In yellow and black[emoticon]



Hmmm, Start with first page and follow the story from the beginning.

* This post was edited 02/04/11 11:17am by Old & Slow *


Posted By: westivanhoe on 03/06/10 12:35pm

This is for Professor 95 or any one who can answer my questions.
I have two Gensets that I want to convert/adapt for LPG. One is a
EQT 3000 Watt, 5 HP. The other is a KingCraft 6000 Watt 13 HP, and
maybe a 'knockoff' of a Honda of similar specs. After reading all of
the conversion posts on the threads, I like the Professor's post
about cutting a proper size hole in a plate made from bread board plastic and drilling the hole for feeding propane, 3/16" for the
3KW and 3/8" for the 6KW (ARE THESE HOLE SIZES CORRECT ?). I have some scrap aluminum to make the 6KW plate that will accommodate the
3/8" feed hole. This method seems safer than 'free hand' drilling the
carb. On the subject of Vacuum. It is my understanding that the addition of a vacuum hose to a drilled spot on the carb is only necessary if there is to be an external fuel pump. Both of my sets have gravity feed for gasoline. So, my carb can remain un-drilled.
(IS THIS CORRECT ?) When switching from LPG back to gasoline is it
necessary to remove the 'bread board' plate? And the plate does go on the downstream side of the carb. (CORRECT?) I want to thank and
congratulate all of those who post to these threads. good work and
super pictures. Thanks millions. Fred


Posted By: professor95 on 03/06/10 06:34pm

westivanhoe wrote:

This is for Professor 95 or any one who can answer my questions.
I have two Gensets that I want to convert/adapt for LPG. One is a
EQT 3000 Watt, 5 HP. The other is a KingCraft 6000 Watt 13 HP, and
maybe a 'knockoff' of a Honda of similar specs. After reading all of
the conversion posts on the threads, I like the Professor's post
about cutting a proper size hole in a plate made from bread board plastic and drilling the hole for feeding propane, 3/16" for the
3KW and 3/8" for the 6KW (ARE THESE HOLE SIZES CORRECT ?).


A 6" piece of 1/4" copper tubing will provide the final LPG fuel feed for either engine. The 6000 watt will probably need a larger diameter LPG gas hose to and from the regulators.

Quote:

I have some scrap aluminum to make the 6KW plate that will accommodate the
3/8" feed hole. This method seems safer than 'free hand' drilling the
carb. On the subject of Vacuum. It is my understanding that the addition of a vacuum hose to a drilled spot on the carb is only necessary if there is to be an external fuel pump. Both of my sets have gravity feed for gasoline. So, my carb can remain un-drilled.
(IS THIS CORRECT ?)


If I follow your question correctly, you are referring to the vacuum port for a Walbro vacuum fuel pump for non-gravity fed gasoline engines. So, yes, since your units are gravity fed gasoline it is not needed. But, on the 13 HP engine you have a different requirement for for converting to LPG that you do not have on the 3500 watt genny. On any engine using LPG that is OVER 12 HP you are required by Fed regulations to have a vacuum operated cut off switch that works a LPG gas line solenoid valve. This switch must run from ported vacuum so the switch & solenoid closes when the engine is not running. Check with US Carb if needed for complete regulations. What you do with your engine that is 1 HP over the mark for this added safety feature is not my business. But, you should know the law.

Quote:

When switching from LPG back to gasoline is it
necessary to remove the 'bread board' plate? And the plate does go on the downstream side of the carb. (CORRECT?) I want to thank and
congratulate all of those who post to these threads. good work and
super pictures. Thanks millions. Fred


For an engine running at a constant speed (3600 RPM)the fuel feed block (breadboard) goes in FRONT of the carburetor - before the throttle butterfly. Your generator does not have "eco-throttle" that reduces speed like some inverter gensets. Those need two blocks - one before and one after. Put your block on the front or it will constantly surge.

When changing to gasoline you do NOT have to remove anything.

BE CAREFUL, PLEASE!



* This post was edited 03/06/10 06:41pm by professor95 *


Posted By: westivanhoe on 03/08/10 10:16am

Professor 95, many thanks for answering my questions. You
are perfoming a great service for all "tinkering" people-,
it is greatly appreciated. Fred


Posted By: olephart on 06/25/11 04:29pm

I've been pestering the Professor over on the Chinese Generator thread about converting my Champion 3500W to LP gas. Finally got around to doing it and wanted to share a few things.

I wanted tri-fuel and didn't like the problems with the air filter bracket and clearance issues that come with the adapter method. I decided to drill into the venturi area as the Professor mentioned in the other thread.

About the only thing different from the Professors parts list is the copper feed tube. It's 5/16" O.D instead of the typical 1/4". Why? Because I had it and it fit. I also used a 3/8" "T" for the load block instead of 1/4". Why? I had one on hand. I would recommend the 1/4" block because you can easily thread it for the 1/2" bolt. The 3/8" block requires a good bit more machine work to use.

Here's a picture of the hole I drilled in the carb:

[image]

Some tips. It's much easier to use a mill or drill press with an X-Y table to line things up, but you can use a drill press if you take your time. Clamp the carb in the vise and rotate it till the cutter is pointing at the center of the venturi and the edge of the cutter is as close to the edge of the venturi as possible while maintaining clearance for the plastic throttle thingy and choke.

You will notice I took a little material off of the cylindrical boss at the bottom of the hole. This made an extra place to put some JB Weld and adds to strength. I ran the shop vac while drilling to keep chips out of the carb.

If there is minor interference with the plastic throttle thingy, You can trim it a little with no harm. I had to do this. Remember, my tube was 5/16", yours will probably be 1/4" and have more clearance.

Bend the copper tubing before you drill. Make sure it will clear everything and have a straight section on each end. I had to put a slight dog leg in it to equalize clearance between the air cleaner and the starter housing.

A center cutting mill is necessary. They can be found for cheap and will allow you to cut through the irregular shapes at the desired location. A regular drill bit could cause problems.

Here's a picture with everything hooked up:

[image]

The parts wound up where they are because it is the only place I could find that met all my criteria. I wanted 12" or less for the fuel line. Wanted the generator cover to fit. Wanted to protect the primer button on the regulator. I didn't want the long snout of the quick connect poking out into traffic.

Many thanks to the Professor making this easy for the rest of us.


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