Alright, I have asked these questions of my friends in the US, but in reality, they just don't know. So I come to you guys begging for any information you have.

I *AM* going to install an STI Version 4-6 motor and tranny into my Impreza RS. I wish to modify the motor to a mild 350hp. It seems that this mark is very obtainable with the STI motor with very few modifications.

The big question is, can the tranny handle it? I have a history of drive train problems in my weak 180hp RS, so I don't want to be plagued with those same problems in a non-warranty transmission that will cost me thousands of US Dollars to fix.

So please, if you have any experience at all with the STI motor, modified or not modified, post it here. I want hear if you think the drive train is tough as nails, or has been leaving pieces of itself at the race track.

Thanks for your time!

-Dan

 

Nobody has any comments on their tranny? I did searches, and the only interesting thing I found was people having problems with the 5th gear synchro in version IV trannys.

I just read an article about the 10.5 second WRX that had custom dog gears in the tranny so he can spin street tires through 1st, 2nd, and part of 3rd...

But I am not looking for that much power! Ideally I want an STI motor, with upgraded turbo, IC, ECU, exhaust, Downpipe, and filter. But I need to know if I am going to have to modify the stock transmission to handle the boost in power. If I do, then I will have to do that instead of some of my planned engine modifications.

Thank you for any help you can shed on this matter.

-Dan

 

I don't know that much about the differences in transmission between the WRX/STi units and the RS, but as far as I know, you seem to get the odd syncro problem on all the units. My 3rd gear is just a little notchy (STi4) but fine other than that (touching wood quickly!).
The only comment I do have is that 350BHP is not THAT easy to obtain from these engines. I think you will need access to 100RON fuel and large turbo's and front I/Cs can just give you a whole load of lag. Downpipes also tend to give a better release of the available power leading to the impression of an increase without increasing it as such. I'm not saying you're wrong and won't get 350BHP, but be careful you don't lose the driveability in the process.

Neil.

 

You will be no were near 350hp with the mods you mention!

Though this depends on whose rollers you use.

I have an sti with:

Link ECU
vf22
Full BPM twin dump exhaust
Forge dump valve (necessity)
Blitz air filter

This only produced 277 hp at just under 1.3 bar with 262 lbs torque at Powerstation (it produced 299hp and 287lbs torque in standrad form a Well Lane Turbo!) depends whose you believe is correct?

Deeper intercooler 'will' allow me to run slightly higher boost without knocking - but is not a necessity at present.

To get to 350 hp I will need to spend about another £8k! (including labour)

Steel Crank
Group A Conrods/bolts
Uprated head gasket
Equal length manifold headers
Cam follower kit
Cosworth/Omega Pistons
Uprated fuelling
Anti surge plates, etc, etc

Then I'll need an uprated clutch

The gearbox can withstand up to about 360hp, 360lbs torque - so I'm told by those who have modified above this level

Re what you mention - gearbox synchro problems are far, far more common on the Type R gearboxes, that,it would appear have an inherent manufacturing defect - especially 5th gear synchro - I have not heard of any problems with the normal saloon