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+--- Thread: Manual VNT control with std wastegate pod. (/showthread.php?tid=1518)
Manual VNT control with std wastegate pod. - winmutt - 07-22-2010
Stolen from peachparts.
http://www.youtube.com/watch?v=BnHGbN67PIM
Thoughts?
RE: Manual VNT control with std wastegate pod. - muuris - 07-22-2010
Not good that way. If the guy put an EMP gauge on that, he'd be careful with the throttle. First of all, should be controlled with EMP rather than boost. Secondly, a wastegate actuator has kinda narrow operating range, it's widely open rather quickly after cracking pressure. Should be more constant adjustment rather than typical wastegate operation (on-off).
Besides that there will be horribly high EMP before boost rises, also boost will build actually slower than with a system where vane ring starts to open as EMP rises, before you can even see anything at boost gauge.
This is with big VNT/VGTs, same thing with both GT37v and He351V as I've tested. Will not boost nicely if EMP goes too high too early. With a small VNT and in a smaller motor (GT20v and BMW 2,4L) it worked better with a wastegate actuator and boost control, although that would also have been better with EMP control.
RE: Manual VNT control with std wastegate pod. - ForcedInduction - 07-22-2010
Ditto. That guy has sky-high EMP from idle until maximum boost. The Holset VGTs aren't designed to be fully closed all the time like Garrett VNTs, the first 25% movement is the exhaust brake and high EGR flow range.
I can trick the ISL and ISM engines at work into running 98% closed from idle instead of the normal 70%. Boost builds slower and the engine becomes a dog off the line from the extreme exhaust pressure. I can't make it go 100% closed except during actuator calibration with the engine off.
From 700rpm to 1400rpm the ECM varies vane position from 81-98% closed producing 50-75psi of exhaust manifold pressure with only 1.5-16psi of boost. Plus it surges badly if you lift off the throttle.
Accelerating normally at 1400rpm produces 15psi EMP, 25psi IMP