Good wastegate size??
05-04-08, 03:59 PM
#27
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Sorry if I sound like a noob, but would a boost controller take care of boost creep. I'm talking about on the stock turbo trying to maintain 9-10 PSI. And, can you put an external on a stock turbo?
12-13-08, 11:20 AM
#29
no, you dont have to have a custome manifold. Just drill into the bugger, and weld an extrernal waste gate to it, and weld the internal shut.
or, if you want, you can do this
I started out with a BNR stage 4 that was a 60-1 HiFi compressor section and a T04 "O" trim exhaust wheel in a S5 turbo housing/manifold w/ mild ported wastegates.
It had boost creep by 3,000rpm, so I ported the wastegates some more and the exhaust wheel got a clip. Still had boost creep.
I open air vented the stock wastegates through the backplate and had it built w/ a larger "P" trim wheel as well as grinding the scroll slots wider and shaped more toward the turbine wheel. It still had boost creep above ~5,000rpm.
Clipped the "P" trim 15 deg and ported out the wastegates as far as the housing would allow and put a HKS 60mm external wastegate on it. Still had boost creep after 6,000rpm.
Finally, I ported the velocity stacks down quite a bit in the exhaust manifold and ported the turbine housing to match up to the wastegate runners to reduce the velocity so the exhaust favored wastegate flow over turbine flow. This fixed the boost creep, though it made 1,000-3,000rpm boost response a little more sluggish.
Still gets boost off idle, ~2psi by 2,000rpm, ~7psi till 3,000rpm and full 14psi boost ~ 3,400rpm in 5th. Spins street tires through 4th gear had to switch to race tires on the street. 720cc primary and 1600cc 2ndary injectors at high duty clycle...
That wastegate divider to keep the manifold truely pulse divided didn't work out. The exhaust energy tore the thick stainless in half twice.
First time (after ~3,000mile) I though it was from thermal expansion and breaking the welds so I welded it at the back plate and made that ring at the end so it could slide as it expanded. It tore the even thicker stainless sheet in half again (after ~12,000? Miles and lots of racing) right where it bends in the elbow section and the "tang" was left welded to the backplate.
It lacks the divider now, but the difference is barely noticeable.
It had boost creep by 3,000rpm, so I ported the wastegates some more and the exhaust wheel got a clip. Still had boost creep.
I open air vented the stock wastegates through the backplate and had it built w/ a larger "P" trim wheel as well as grinding the scroll slots wider and shaped more toward the turbine wheel. It still had boost creep above ~5,000rpm.
Clipped the "P" trim 15 deg and ported out the wastegates as far as the housing would allow and put a HKS 60mm external wastegate on it. Still had boost creep after 6,000rpm.
Finally, I ported the velocity stacks down quite a bit in the exhaust manifold and ported the turbine housing to match up to the wastegate runners to reduce the velocity so the exhaust favored wastegate flow over turbine flow. This fixed the boost creep, though it made 1,000-3,000rpm boost response a little more sluggish.
Still gets boost off idle, ~2psi by 2,000rpm, ~7psi till 3,000rpm and full 14psi boost ~ 3,400rpm in 5th. Spins street tires through 4th gear had to switch to race tires on the street. 720cc primary and 1600cc 2ndary injectors at high duty clycle...
That wastegate divider to keep the manifold truely pulse divided didn't work out. The exhaust energy tore the thick stainless in half twice.
First time (after ~3,000mile) I though it was from thermal expansion and breaking the welds so I welded it at the back plate and made that ring at the end so it could slide as it expanded. It tore the even thicker stainless sheet in half again (after ~12,000? Miles and lots of racing) right where it bends in the elbow section and the "tang" was left welded to the backplate.
It lacks the divider now, but the difference is barely noticeable.
see... tadaaaaa!!!!
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