Hi all,


Just bought a 1998 STI V4, now looking at safe ways to up the power.
The engine has recently been rebuilt with new STI crank, mahle forged pistons/rings but still has the standard STI rods. Standard 5 speed gear box, exedy clutch.


I have found this guide on Andy Forrest's website which should take the power to around the 370-400 mark.


Level 3 370-400 bhp

Full Decat turbo back 3” bore exhaust system.
Tubular exhaust headers and flow matched uppipe
Walbro 255 l/hr uprated fuel pump
Fuel Lab turbo specification fuel pressure regulator with fitting kit & gauge
High Flow multi spray fuel injectors 550cc (440cc std)
STI V7/8 TMIC & matching undertray
0r
Front mount intercooler
AFP 05-20G custom ported turbocharger
Apexi Induction System
Standalone Apexi Power FC Fully Mappable ECU with 4 x Boost/Power settings in-car adjustable
NGK PFR 7B uprated spark plugs



Does anyone agree with this or any changes to the list that will keep the car running safe enough?


thanks

 

Don't push the std rods much over 300, they are not that strong. FYI all the rods in the classics are the same, wrx/sti. Only new age cars have better rods in the STI 2.0 and all 2.5's.

 

this seems rather an odd build. conrods in classics are thin and weak, and when i had the engine build, changing the conrods to uprated ones, regardless of the condition of my existing ones was a must have or the engine builder would not take the job...

And above 350 bhp, you better start saving for the 6 speed box because it wont last long. you are better off settle for 350, and spend the rest of the money on brakes, coilovers and make the car shine IMO.

 

Indeed. It's very odd not up rating the rods especially with it being a classic. As above I'd be wary of going above 350 on standard classic rods and gearbox.

 

It's not so much the rods but the rod bolts that are the problem, they are the press stud type and can fail at around the 300/ 350 mark, luck of the draw as to how much they will take, if they have been pressed out and changed for ARP's (not sure if it's possible) then it's a different kettle of fish and they should be good for 400 ish.

As for the gearbox, I caned my V3 Type R box at 330bhp and it took everything I threw at it, and still going, they can take more if you're sensible about it, I think the late great Harvey Smith(rip) ran one upto 450bhp, but added a word of caution about launching and ragging the **** off it, personally I'd go with the braces that people have started fitting beyond 330/350bhp. 6 Speeds are no guarantee as more and more of them are showing signs of age and wear as time goes on.

 

I thought it was odd myself as if I was going to the hassle of getting all that work done I would have spent that bit more or updated rods and gaskets. Thanks for the advice, time for a re-think!

 

I have got in touch with the company that did the rebuild, just incase the info I got from the last owner wasn't quite right. Can you explain the braces you mentioned??

 

braces are some metal plates which are bolted on the outer case of the gearbox. Idea is that the 5 speed gearbox strips the 3rd gear due to flexing of the gearbox case under torque which then increases the gap between gears and therefore it strips the gear you are into.

now that's all good, but 1 company who tested sayd they take "400 bhp" called MOORE(or so) and is just expensive. about $500 i remember. some other UK sellers claim to copy this design and sell them plates i saw on facebook one time for £180 a pair or a bit more not sure. Still a rip off IMO for literarly 2 flat steel pieces to bolt on your box....

i`m an engineer myself, and them things could not cost more than £50 each in materials when produced in batches of 10 sets. And that's lasercut...