Deep Singh

I know this will sound a little stupid to some.
On the classic STi can you buy a 2.5 short motor and basically plumb it into the engine,ie retain original pistons,rods,turbo etc etc.
If the answer is yes,how much extra power does this safely give? Any down sides?
Many thanks

Mark A

iTrader: (1)

Do a search for more details, but yes it does just plug in.

Upto 400 bhp depending on the supporting mods

john banks

Downsides - most don't rev them over 7500 RPM, so if you have an STi with short gearing your road speed in each gear will be lower and it could be a bit manic. The short motor comes installed with crank, bearings, rods, pistons, all you need to do is get gaskets, coolant, oil and swap everything over. You need to remap the ECU as well, and the torque may trash the clutch and gearbox. Power is related to turbo/intercooler/induction/exhaust/fuel system, not capacity. My attempts at pushing substantially over 450 BHP (using 25 PSI on turbos that are too small for the job) has resulted in failures. At 400 BHP at about 1.2 bar it seems pretty solid and very driveable with a sensible sized turbo - eg 20G is a peach, 1 bar at 2500 RPM, 400lbft it quite easy at about 1.4 bar. It may get the better of an STi 5 speed over time though - debated.

Deep Singh

Hi JB/ Mark
Does that mean not really suited to Type Rs?
JB are you doing 450 BHP on the std pistons/rods that come with the 2.5?
How many hours labour approx for the install?
If power not related to capacity then why go for 2.5?

Sorry, presume this has been done to death before!

Cheers,Deep.

john banks

They are not unreasonable for a Type R, but they could be a little manic. Trouble is all the tougher gearboxes (5 speed STi or 6 speed) are all short geared at least in the first four gears.

Yes I'm running std pistons/rods that come with the 2.5, so a bit of a bargain if they hold as the short block is about £1100-1300.

Install - usual cost of swapping a short block, couple of days labour? Use a Subaru specialist.

Power - it does improve power in the sense that you can run a bigger turbo at lower boost and make more power and torque with less heat and less lag. You get a nice phat power band - TD04 style spool up with a 400 BHP hit

Deep Singh

Thanks.
So IF I had a STi4/5 with uprated APS tmic, exhaust,induction,headers,fuel pump/reg,injectors,mappable ECU I could bang in a 2.5 and appropriate turbo and run 375+ BHP everyday as a fast road car?

I c'ant believe I'm being sucked back into the world of modded Scoobs!

Deep

alanbell

iTrader: (6)

Yes ,

heple1983

Dont forget about the £2.5k 6 speed box your gonna need!!!

FASTER MIKE!!

to use the full 8-8250rpm is it nessasey to have uprated internals? or are there people that are using the std 2.5 bottom end and running a higher revlimit?

Deep Singh

Aha,always a catch. Why do you need a 6 speed?
Cheers

heple1983

The 6 Speed is a stronger box much more capable of dealing with the increased torque.

Deep Singh

Thank you. I've done the search and benefits/issues apparent