Steam STX 71 + 2015 Subaru STI PREracing Dyno Session

I spent the day a few weeks back at PRE.  I was getting our shop I had originally booked our 2001 RS with the EJ207 swap to get tuned, but we ended up having a double feature.

SteamSpeed's 2001 RS w/ JDM EJ207 + STX Power
SteamSpeed’s 2001 RS w/ JDM EJ207 + STX Power

Anyway, way back at the BNW meet, we told Jason that the STX 71 is a 400+ WHP turbo.  Frankly he did not believe it simply because no turbo on his dyno has been able to make 400+ WHP with a stock sized inlet.  We now our turbo is not any other turbo and can make more power than competing turbos from Tomei, Blouch, Tomioka Racing, etc.  So, we gave him a STX 71 to verify our claims for himself on his own dyno.

He found a willing customer with a 2015 Subaru WRX STI with a stock block and a number of COBB parts like their exhaust system for example.  COBB makes fine parts, but they, for the most part, are not designed to make over 400 WHP.  For example both their so called 3″ down pipe and cat back have a 2.5″ taper.  I guess that is great for mating to the stock exhaust system, but not great if you want to make more than 350 WHP.

Luckily their customer was on board on swapping out the power limiting parts with exhaust and intercooler components from ETS and GrimmSpeed.  I worried that they kept the COBB intake since it isn’t a “big MAF” style intake and all of our turbos will max a stock sized intake, but Erich , their tuner, said it is larger than stock and should be ok.

2015 STI with a Steam STX 71 turbo
2015 STI with a Steam STX 71 turbo

With all of the supporting mods, Erich when after it, and laid down a great tune.  With consideration for the stock motor, this is where he left it.  Note: they don’t do any correction on their dyno numbers.

PRE's 71 Test tune on a 2015 STI
PRE’s 71 Test tune on a 2015 STI


Anyway, Erich calculated that corrected atmospheric conditions the peak power that was measured was actually 395 whp.  He expected that it would probably have made another 40 whp and likely maxed out the MAF on the larger diameter COBB intake.  More importantly, no other turbo had made similar power on a stock sized inlet with pump gas.

Nice work guys at PRE!


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