Two pics of the cool air intake I built for the new engine.
Two design goals. First to draw in cool air from in front of the radiator. Second was to create a Ram Air inertia effect from the long runners on the intake. First impressions are that both goals are achieved. It idles smoother, runs much smoother and more responsive off the bottom end. The runners are 2 inch, same as the throttle valve. Bending the PVC pipe was done by heating it with a turbo heater. I discovered if you want to bend PVC and not have it kink, you only heat the outside radius. This way the outside stretches and the inside just bends. Can't tell if I've lost any off the top end as the engine doesn't run right wide open yet. Still needs tweaking. That and I broke a throttle cable on my test drive. Little tricky driving with Visegrips on the throttle shaft and a string tied to the end of the handle. Fortunately, I was only about 5 miles from home.
Dave
FMCA F298817
'83 Revcon Prince 31' FWD
502 w/Howell/Edelbrock MPFI, Thorley's & Magnaflows,
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Thanks Dave for the pictures. I was just thinking about this subject today as how to get more air into my stock 1992 454. The question I had will the stock filter be my limiting factor?
I first thought your throttle plate adapter would limit your air flow volume then I realize you had a much opening as the stock air intake could pass. I do have a safety question about PVC in that hot of an environment but as I type I realize they are "air cooler".
Perhaps I will make a short run ( a few miles ) without an air filter some rainy and bug free day to see if I can "feel" any difference.
PVC doesn't bend until it hits ~600 degrees. (IR gauge reading when bending) Even then it just acts like rubber. There is quite a bit of air flow even at idle. I would be concerned doing it to TBI because you have fuel so close to the PVC. With multiport, the fuel is farther down. Sure it could backfire, but typically that is just a quick flash. Flexible exhaust tubing might work, although not real smooth inside. The trick with this setup is not removing restriction do to filtering, but the long tube inlets kind of do the same thing as long tube headers do on the exhaust.
BTW: If you think the filter is a limiting factor, double stack two filters for a test. The only drawback is you are pulling in hot air, but for a test, it will keep the dirt out.
Nice work. Many folks use corrugated flex tubing, but the air flow through that is terrible.
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Does it matter much if they are not equally matched in flow?
I see the left is a little more kinked at the bend than the right.
I understand 4" pipe would need a bigger passage, but would it work better than 2- 2"er ?
TopFlight, I've thought of that and may very well do it since the concept appears to improve performance as planned. Not sure how tight of a bend they can make feeding the throttle valve, but it may be worth the inquire.
Pokiii, if you see them in real person, I don't think they are as kinked as they appear. And below the throttle plate is wide open to both sides, so even if the flow is slightly different, it wouldn't matter in this case.
As far as going to a larger tube, that would defeat the purpose. Yes it will pass more air, but that will only help above 4500 RPM. The heads aren't big enough to flow well at that RPM anyway, so I really will not see any significant improvement. The purpose of the small long tubes is that they are tunned around 3K RPM. 4K RPM is about where the improved torque curve crosses the stock torque curve. So the small long tubes break even at 4K and loose some power above that. According to the computer simulation, the tubes are good for around 40 ft-lbs of torque at 3K rpm.
When I started messing around with a computer simulation, it really was a wakeup call to how critical the intake tuning is. I've read comments on RV.net about guys that have increased the tubing size to the air box and lost power. That makes sense, after playing with the computer simulator. I don't doubt that one can improve things over stock, but it is also possible to make it too big and loose power as well. Notice how all new engines have really long intake runners. There is good reason for that.
I see, thanks for the info. I put a K&N cold air intake on my 05 Tahoe, I noticed more torque and better throttle response on the low end after I put it on, specially when I’m pulling a trailer. Can’t say I noticed as much gain on the top end, than again, I rarely go much faster than 65 with a trailer and the newer and fuel injected motor makes a difference, too.
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