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Old 05-18-2020, 11:20 PM   #8
Scooby Newbie
Member#: 498606
Join Date: Mar 2019
Chapter/Region: MWSOC
2013 Impreza WRX STi


When I said full boost by 4k rpms, I guess I was pretty damn spot on

If you ask me, for a build like this, these are conservative estimates.
The compressor map is what it is -- it won't be flowing any more air, but the VE and turbine efficiency numbers I estimated are definitely on the low side.
With higher VE estimates, the boost numbers should go down.
I wouldn't be surprised if the final build doesn't crack 40psi at 680 crank.

I have a 500CFM donaldson 4" air filter (AKA the BHAF for my diesel friends).
This is a semi truck, high service interval filter with a low micron rating.
My exhaust is pretty free-flowing as well -- oversized valves with high lift cams and mildly ported/polished heads flowing to full-race headers and a full-race up-pipe, then to a 3" catless downpipe and a 3" Invidia N1 catback.

According to the Borg Warner calculator,

at 3,000 RPM, 10psi of boost, 160hp and 280lb-ft of torque
at 3,500 RPM, 15psi of boost, 225hp and 335lb-ft of torque
at 4,000 RPM, 53psi of boost, 565hp and 745lb-ft of torque

38psi is quite a lot to build over 500RPM.

The hell do I need to do to keep 53psi of boost contained with Darton sleeves and 14mm head bolts???

Pretty stoked I'm not going to need to rev this build out past 7k, sticking with that lower redline will help reduce internal fatigue in the long run.
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Last edited by a0d; 05-20-2020 at 02:19 PM.
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