2.5 N/A to Turbo

I'm a little late to the fire, but here's my take.

Two options...buy a standard turbo motor and run piggy back engine management to stay obd compliant.

put a turbo on the motor you have now, and run piggy back engine management.

For engine management, I'd buy (or build if you know how to solder and can follow directions) MegaSquirt. Wire it up to control fuel and spark, leave all the sensors hooked up to the stock ecm. You'll need a wideband o2, so get the LC-1, adjust the voltage on the narrow band output within the parameters for the stock ECM to avoid a fault code. People make engine management out to be a black art. Its very easy to install, even when running parallel to a factory ecm.


I run megasquirt in my miata stand alone. www.msefi.com

Re: Re: 2.5 N/A to Turbo

jellisii said:

My boss has an 03 (I think) Forester with the XT 2.5 in it, with a 4AT.

The turbo lag is PAINFUL for city driving. The engine's great above ~3k, but before then, the car can't get out of its own way. It really turned me off to the factory turbo setup, as I do far too much city driving. Perhaps with a slightly smaller aftermarket turbo that would spool quicker, it may be different story.

An H6 (which was an option on the OBs, so another "should be fairly simple swap for those so inclined") looks like a better idea to me, but then again, I like the broad, fat torque bands.

Let us know how it goes! If you can deal with the lag in the setup, I think you'll be impressed. After 3k, my boss' car seems to really speak with some authority. I think it could be fun as a track car, just not as a daily for me.

Click to expand...

boost threshold =! lag drive an old 911 turbo, and you'll understand.

Its also not a bad idea to consider the same turbo, but a lower stage turbine, or a smaller a/r. The perceived boost threshold deficiency could also be tuned into the ignition map. The old audi tt225 had roughly 9-12* too much retard in timing off boost. Spark was bumped up and we scored 9psi 1300rpm sooner.

I agree with you though. If I ever put a turbo on my 2k0bw, it would be a tiny little gt2554, while my little 1.9l miata has a gt2860rs. If he has an automatic trans, there is no reason to ***** about power off boost.