What's up,
I just rode in my friend's WRX today, he just installed an SR40 turbo. His current list of mods are as follows: Unichip, downpipe, intake, up-pipe, APS TMIC, SR40, STi injectors, and Walbro fuel pump. All I have to say is, WOW. It has a decent amount of lag, but beyond 4000 rpm this thing is crazy. Pulls 100 times harder than the stock WRX in 3rd and 4th (didn't get into 5th). It's a great turbo and I'd recommend it to anyone who can afford the thing. Personally I think it's a bit overpriced and I'm prolly gonna end up with a VF34 in a couple of weeks.


-Kevin.

 

Mine's pretty similar, except with the SR30 instead of SR40. The SR40 is basicly too large for moderately-modded WRX engines. Our stock heads ports and valves peak at 5500 rpm, then start falling off efficiency above that. Further, we're rev limited to 7k or so. To make an SR40 sing on a 2.0: really requires reworked heads and valvetrain to raise the peak volumetric efficiency rpm and higher rev limit.

The SR30 is closer to the VF34 in sizing.In design and theory, the SR turbos are a lot more modern than the 'basic' IHI turbo designs. In practice, the differences are just matters of degree. Tthe SR30 has a wider and taller sweet-spot. It comes-on a little faster than a VF34 and produces an output a little cooler and dense.

The cost/price difference between IHI designs and APS / Garrett SR designs is probably justified on the basis on the technology, but its pretty questionable from a bang for the buck standpoint.

That's what I think, anyway......