Originally posted by FFgeoff i would like to see your proof on that statement. There is a reason no one really is using them anymore, and everyone runs a 4 into 1 collector these days. The last couple of years most people were trying all sorts of different collector styles but if you see the majority of race car manifolds theyre all open 4-1s. I do agree that for the most part the split housings will work better, but that is usually on engines with 6 or more cylinders...
its just the same old 4-2-1 vs 4-1 argument.
Garrett and other OEM turbo manufactures did some testing and found that. Its actualy a common engineering fact about that sort of style manifold, just that import drag racers have not caught on to it yet. It is pretty common on WRC cars.
Its the most effective on 4 cylinder motors, or V-8's with 180 degree cranks. It is very common in the diesel world as well. Its called a pulse converter manifold. When taken firther and combined with a divided housing turbine housing, a pulse converter can bump turbine effiecncy over 20%. This is marked because a 3% bump in efficiency can overcome a 20% gain in roatating assebly inertia. A divided housing also improves VE because it makes reversion and croiss cylinder contamination on overlap almost imposible. It can allow a biger cam to be used.
The charts and stuff that I have from a major OEM turbo supplier is propriatary and I promised my sourse that I would not let it out in public. If you want to read some engineering text stuff on pulse conversion, I recomend the book, Turbocharging the High Speed Internal Combustion Engine by Watson and Genoda. They have a whole chapter on the subject and modeling equations.
Thanks for the tip. I have spent the better part of 3 hours looking for that book and cant find any trace of it anywhere. Got any clues?? thanks tho i love finding good books
As for the theory, i understand the idea of pulse converter manifolds, but maybe the manifolds we have dealt with were somehow not properly functioning or who knows but we have yet to really see any power gains using one on the ecko drag car. It made 943 whp with the open housing and a 4-1 merge collector, but with a similar equal length manifold and the split housing it made 917 and similar torque. This was on methanol, but it should seemingly work better witht he pulse converter... ive seen simliar results on a number of other cars, look at venom they are running a shorty style manifold 8.63 and 1040 hp, jotech same thing and 890 hp, no one is running a divided housing and most everyone has tried them out.
Any ideas?
Oh and as far as camshaft choice goes, heres a weird one. Jotech goes 172mph and 8.59 on stock GSR camshafts.
on the ecko car, they are running the BIGGEST cam they can (its not vtec) and the valves are dropping so far down in the hole that they are as big as possible so that when the motor is clayed its off the clay by about 10 thousandths. After you reply to this post ill be deleting this because its not really my place to let all this info out, but this is a slow board.
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Last edited by FFgeoff : Nov 4th, 2002 at 02:28 PM.
Geoff, Just curious, what Size cup are you using on your torch as well as type of tungston you used when you made that manifold? Also what was your flow rate, and travel speed? Do you utilize a turn table? How far was your tungston sticking out beyond the cup?
Originally posted by FFgeoff Thanks for the tip. I have spent the better part of 3 hours looking for that book and cant find any trace of it anywhere. Got any clues?? thanks tho i love finding good books
As for the theory, i understand the idea of pulse converter manifolds, but maybe the manifolds we have dealt with were somehow not properly functioning or who knows but we have yet to really see any power gains using one on the ecko drag car. It made 943 whp with the open housing and a 4-1 merge collector, but with a similar equal length manifold and the split housing it made 917 and similar torque. This was on methanol, but it should seemingly work better witht he pulse converter... ive seen simliar results on a number of other cars, look at venom they are running a shorty style manifold 8.63 and 1040 hp, jotech same thing and 890 hp, no one is running a divided housing and most everyone has tried them out.
Any ideas?
Oh and as far as camshaft choice goes, heres a weird one. Jotech goes 172mph and 8.59 on stock GSR camshafts.
on the ecko car, they are running the BIGGEST cam they can (its not vtec) and the valves are dropping so far down in the hole that they are as big as possible so that when the motor is clayed its off the clay by about 10 thousandths. After you reply to this post ill be deleting this because its not really my place to let all this info out, but this is a slow board.
I got the book from SAE publicatins a long time ago, it's proably out of print by now perhaps.
Maybe its other factors like the turbo choice?
Turbo selection has a lot to do with how well a cam works, in my opinion if the engine runs into crossover then you can run close to the same cam that works well naturaly asperated with just spreading the lobe centers a bit more. I usualy spread the centers more towards the exhaust side so the extra blowdown helps spool the turbo quicker.
I always check pre turbine backpressure when trying to figure this stuff out. Lots of backpressure, especialy if more than the boost pressure likes short duration less overlap.
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