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hi, guys
not sure if you'll believe me, but I was the guy who designed this puppy for GM quite a few years ago. I googled it just to see if they are still using it...and bumped into this thread.
lots of truth, lots of well-intentioned nonsense in this thread. fwiw...the manifold is molded in 33% glass fiber filled nylon (which is technically a composite, but usually called a filled polymer). It is good for 350 def F continuous duty. The reason it is plastic is twofold...super cheap to make with a funky "lost metal" style used by Freudenberg in Germany (who makes them for GM) and because they add several hp from being so darn smooth inside, better than even "flowing" an aluminum head. also, obviously they are incredibly light and because of the advanced molding it was possible to incorporate other typically separate parts like the fuel rail and internal cooling runners, although I don't know if they are still doing that (hell I didn't even know they were still using it, although they predicted it would be in use for at least 30 years back in about 1992-3 when it was designed. As for the guy who said they don't flow as well...no way, that should be obvious on its face. If it didn't flow as well as metal, it's gotta be that somewhat dissimilar shapes were used, not the material...cause the difference is night and day. also, the manifold won't break down or explode with backfire, it will last beyond your lifetime without doubt...it was designed extra strong because of the imbalances in the early motors without counter-rotating shafts (I am assuming they must have counter-rotaters by now, but don't know). And even if it did get overstressed, it would simply swell microscopically, uniformly...strain, in other words. Also, GM didn't design it, Dupont did (who makes the material)...GM only designed the flow path of the tubes.
hope that wasn't too boring...pretty cool they are still using it IMO...oh, and no doubt they should be considered a performance mod...reverting to metal for performance reasons even for NO2 is backwards. The original design had a heavy throttle body hung on it...so this should handle any extra weight since I assume they must be individually fuel injected by now.
cheers
John
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