is this a better or worse place to start for best torque / £ than 05 2 ltre STi - conversion cost must be sensible and can assume a PPP base car if preferred

I believe the 2 litre tops out at c 350 lb ft without going to cost of turbo change etc

Can 2.5 get near 400 lb ft for similar modest changes?

 

With exhaust , headers , RCM induction kit and a remap you should be nudging very close to 400lbft on a 2.5 Sti...

 

Typical figures from a full exhaust system, fuel pump, air filter and a remap are in the region of 350bhp and 390lb/ft on a 2.5L STi.

 

what would be the next low cost upgrade to get more torque and ideally earlier in rev band?

 

After these power figures it would be time to upgrade the internals for a start, I believe this is around the safe linit at which a 2.5L Sti can take.

After these initial modifications, I don't think anything is low cost mate.

Most people chasing power figures go for a change of turbo after this.

G

 

You say ideally earlier but have you driven a well mapped 2.5 STi?
The standard car once remapped will hit peak torque around 3500rpm and with a fairly conservative tune will hit 370ftlbs. Decatting, etc etc will achieve higher figures (circa 400ftlbs) but ultimately the turbo is just too small to produce power much above 350bhp - expect peak power to be produced around 5500rpm.
Larger turbo is the way to go and if chosen well will produce as much torque as the standard turbo low down, but will continue to hold this torque to produce the power to match

 

A remap/pump/filter/exhaust is as cheap as you get for the hawkeye STi and is the biggest bang for bucks I've seen on a car.
Trying to cut out parts of that package is just a compromise.
Take a visit onto the NASIOC website and see the problems caused by modding the 06/07 STi without any sort of remap. A decat seems to be sure fire piston killer.

The next step is a turbo and injcetors to get into the 420/420 region, but this will need internal engine work.

Nick

 

How much difference do headers and induction kit make to the 06 Sti in addition to decat and remap ? I note spool is low on the 2.5 anyway, so assume the idea would be to obtain more torque and power ? How much are the headers and induction kit ? Was thinking they might reduce the "bang to buck" ratio.

 

thanks for advice guys

 

IMHO.... stick with the standard headers and just get them ported (by someone that knows what they are doing) & stick with the standard airbox with an uprated panel filter. It's all about cost vs performance gains in your scenario.