Subaru WRX Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
73 Posts
Discussion Starter · #1 ·
How much boost can a stock WRX engine safely handile? I am currently running .12 mpa. Is this safe?

Also, how much boost do the WRXs in Japan and UK run stock?
 

·
Registered
Joined
·
416 Posts
I think the fuel cut off is around 17-18 psi.

But in addition to this, how do the STI version get more horsepower? Is it simply by increasing the boost on the stock turbo or do they replace it with a bigger turbo?
 

·
Registered
Joined
·
1,843 Posts
i think its set at like 18.5 or 19...but who knows it sometimes takes a few seconds of running that high for the ecu to throw a cel. ive spiked to like 20 pounds accidentily cuase i screwed my mbc in the wrong way
 

·
Registered
Joined
·
208 Posts
STi run higher boost but their engines are thoroughly built up for higher levels of boost, they can easily take 17-18 psi. Our cars usually cut out around there and we lack the forged internals and block modifications necessary to run higher boost all the time.
I wouldn't run above 16 psi for very long on a stock wrx engine, they just aren't strong enough to run much more than that for extended periods. Several people have blown their engines with just a couple of extra psi at the track.
Running more boost can lead to knocking which in turn causes the ecu to pull timing. Some people claim their cars run best with around 15.5 psi, anything above that was causing them to pull timing with an otherwise stock engine.
Raise your boost, but be very careful about the level you choose. It's not something trivial you can set and forget.

.12 mpa seems kinda high, that's like 17.4 psi.
 

·
Registered
Joined
·
208 Posts
campbell said:
I think the fuel cut off is around 17-18 psi.

But in addition to this, how do the STI version get more horsepower? Is it simply by increasing the boost on the stock turbo or do they replace it with a bigger turbo?
STi turbos range from the VF30 in the older version 7, to the VF34 in the newer ones. I believe they also put the VF35 in the STi RA Spec C. These are all bigger than the stock WRX turbo, but the STi engines are much stronger than ours.
 

·
Registered User
Joined
·
1,911 Posts
Well the boost cut is at around 18-19 PSi BUT the motors can handle 22 PSI no problem on bigger turbos. Boost is irrelevant, power is the determining factor on when the car breaks. If you strap a HUGE turbo on the car I'jm sure you can break it at 12 PSI.
 
1 - 6 of 6 Posts
Top