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Old 02-07-2010, 02:25 PM   #409
Scooby Newbie
Member#: 116814
Join Date: Jun 2006
Location: Colorado Springs
2003 wrx wagon


Originally Posted by xsnapshot View Post
What I'm interested in seeing is how the larger wheel performs in the small housing.

You'll have less turbine area not being occupied by the blades, so less ex. gas can pass by the blades without hitting them. Now this will obviously make your spool up very quick, but I'm worried about your top end. That's part of the reason people clip the turbine blades, to provide more top end flow. So in theory, if your on the stock diameter IWG, this problem should be even worse for you.

Think of a turbine wheel spinning at exactly the RPM needed to achieve your boost target. Now extra unneeded EGBP previously would have slipped by between the housing and the blades and IWG, but now more is being forced under higher pressure out of the IWG and against the blades of the turbine.

I completely agree with you on this point. A much larger WG will be required to control this turbo and prevent overboost in general and boost creep at higher rpms. An EWG would be the safest bet, but if ForesterWTI's modified IWG will flow enough, he may be able to control it adequately.

In anycase, i urge caution when tuning this. Start out with low WGDCs and slowly move them up as you get a better feel for how the turbo will react.

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