I put a 2.5 sti short block in a legacy GT2.5, used sti gaskets, but stock heads.

 

I'm getting ok power (comparable to what you'd expect from a healthy ej22),

low compression, & HORRIBLE mileage) the engine runs PERFECT, so I'm leery about major changes, but need to figure this out.

I drive over 11,000 ft twice a day, so the gas is killing me.

 

any suggestions?

 

I've got a weaponR intake & lightened flywheel, other than that no extras.

Did you make sure that using this shortblock would not cause a change in the compression ratio?

Well the good news is it might run forever. I believe the 2.5 STI is turbo isn't it? In this case you have about the same compression ratio as a Briggs and Stratton. I thought of doing this myself to make the ultimate tough 2.5. The bad news is that you would lose power and gas mileage most likely. It really should be just a bit better that a good 2.2 but will be running when you are dead.

it went down to 8.5 because of the increase in thickness to sti gaskets (I think) obviously at my altitude, a loss of compression was the last thing that I wanted, but the shop that did the work didn't mention that I would lose t with this setup (I guess it should have been obvious, but it didn't cross either of our minds)

 

would 1/2 lb loss cause this huge change in efficiency?

it is NOT turbo btw

There's the problem, asuming they left the STI pistons in that shortblock.

I meant was the STI shortblock meant to be turbo? It sounds to me that you have exactly what you ordered.

If you want to drive to CA I will be happy to trade engines with you. According to the STI I just looked up it should be a shortblock for a 300 hp intercooled turbo. If you put that together with no turbo and a stock set of 2.5 heads waht you have is exactly the result. Congratulations! You have just built an excellent non-performance motor.

If you found the right set of 2.2 heads you might be able to get usable horsepower for your altitude. I suggest you check with NASIOC to see if anyone knows which heads have less ccs in the chamber.