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Old 11-14-2012, 12:39 PM   #1115
Scooby Specialist
Member#: 179846
Join Date: May 2008
Chapter/Region: NWIC
Location: Renton, WA
07 STi Limited
EFR 7670 TS


Originally Posted by kellygnsd View Post
I don't know what egbp #'s you've seen but the ideal ratio is 1:1 boost to egbp so for 20 psi boost you would want about 20 psi egbp. The ratio is higher during spool up too. Subarus never acheive this 1:1 ratio and in reality more in the realm of 1.5 to 2.0.

Think about this then, a turbo running 20 psi with a 1.5:1 boost/egbp ratio would have 30 psi egbp steady state, but much higher egbp during spool up.

While its not crazy pressure I could easily see 30-50 psi forcing open the wastegate against a weak spring.
I did the test on back pressure about 1 month ago and it was 1:1 all round. at 25 psi to id get 25 psi of back pressure.
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