Is this a 106 chassis from Freightliner or a larger size chassis? And does anyone know what the HP maximum is on this particular chassis? Dynamax shows (on their website) 350 Cummins diesel as being the most HP one can get on this chassis set-up. I wonder if commerial trucks on this chassis can get more HP vs recreational units?
For a given engine size, engines in the commercial chassis are usually down-rated from the ratings used for RV applications. For Cummins particularly, engines sold for RV chassis get the highest ratings offered, because anticipated duty cycle is lighter. This may not be the case for the M2 going to Dynaquest, they could be getting the lower ratings offered for highway trucks.
However, commercial customers, particularly fleet operators, may have an option to order a yet LARGER engine in the M2, without upsizing the chassis. I know this was the case 10 years ago, when one could buy a Series 55 for the M chassis, but things may have changed with so many fewer engine choices having EPA ratings for highway use.
Did some checking for you. The Dynaquest is using the M2-106. Engine offerings on the M2-106 are currently Cummins ISB and ISB, as Daimler is no longer offering any of their own engines in that size range (they formerly used a small MBE in the lighter M chassis). Dynamax is using a lighter version of the 106 on the Dynaquest ST, with ISB rated at 325 HP. The heavier Dynaquest XL gets a heavier M2-106, with ISC rated at 350 HP. That's the largest engine now offered in the M2-106.
The M2-112, next class up, uses a DD-13, which is a descendent of the MBE that became DD Series 55. That's a huge step up in size.
Those ISB (325) and ISC (350)ratings are just slightly lower than Freightliner's highest rated offerings for M2-106, and yet a bit more lower than Cummins' highest ratings for motorhomes and emergency vehicles (400) in the case of the ISC, and for motorhomes and pickup trucks (350) in the case of the ISB. Motorhome, pickup truck, and emergency vehicle ratings assume intermittent/emergency use of maximum rated power, and the ECM will scale back power as needed to protect the engine. Cummins MDT ratings are for maximum continuous output. Even lower ratings are applied to the engines for 24/7 running at full power.
* This post was
edited 08/21/11 03:50pm by tatest *
I think the "why doesn't" is not a Dynamax issue, rather a Daimler issue, because it is the chassis manufacturer who chooses the engines, the house manufacturer can only choose the chassis. The reason Freightliner offers any Cummins engines is because Daimler doesn't currently have EPA highway-certified engines in a given size.
Currently, in the M-2 (106 or 112) the diesel offerings jump from the ISC to the DD13, a gap of a couple sizes that could be filled with Cummins engines (ISL, ISM) but Freightliner chooses not to. The only ISL offering from Freightliner is a CNG engine.
My whole point in asking for HP possibilities on the M-2 Business Class 106 chassis is I'm looking into a possible purchase/order of a Dynaquest. If you view Cummins diesel website section you'll see there isn't much in the way of weight differences between the ISC8.3 350 HP engine and the more powerful ISL9 400 HP engine. So why doesn't Dynamax offer the ISL9 on their heavy duty M-2 chassis? They didn't really answer my question when asked. To me, more HP in a recreational vehicle is a no brainier if at all possible. We like the NW part of the US as well as Western Canada. Where hills/mountains abound. And after reading many Dynamax satisfied owners (many of them here) I decided that this version of an RV was right one for the two of us. I have some consternation with their engine choices.
4 whopping cylinders on Toyota RV's. Talk about great getting good MPG. Also I have a very light foot on the pedal. I followed some MPG advice on Livingpress.com and I now get 22 MPG! Not bad for a home on wheels.