Best n/a engine configuration for autocross?

[turbodan]

Trying to work out the best setup for racing on gravel where top speed is under 100 km'h.
Used a Gen 1 ej22 fwd legacy last season stock except for exhaust and rally tyres and got outstanding results...... 6'th outright out of 80 cars and first in my class on the last round!
top runners are n/a 2 litres pushing over 200 hp (galant and mach2 escort) and others down from that like 2.5 strokers, 20 valve supercharged 1600's etc etc some of which I'm beating! :-) also my brother in law has the same model legacy with exhaust, extractors, head work suspension etc is getting third outright on many rounds (GO THE LEGACY!!)

My plan to fly the flag for Subaru next season is use my 83 Leone coupe with legacy or similar running gear.
I have no idea on my budget until I've secured good sponsorship and after scouring the net for threads that generally end up hijacked by turbo suggestionsI'm still studying.

The Frankenstein 2.5 with 2.2 definitely has good torque and power for less outlay but I require a package that can breathe at high revs as it gets caned and from what I've read the Frankenstein had problems there.

I was considering a turbo engine with a suitable turbo or a low preassure higher compression set up but my thoughts are to use legacy running gear and do the five stud conversion and brakes with a ej22e with port and polish maybe bigger valves, shave heads and thinner gasket, cams, extractors, exhaust, cold air induction, chip and 100+ run fuel.

Probably only net 160 hp or so which would kick ass but I wanna win and that might not be enough? For a chance.


Also need a front LSD, does STI box hook up to ej22e or can one be fitted to legacy five speed box?


Any educated info would be appreciated ;-)

Cheers Dan

[turbodan]

http://forums.nasioc.com/forums/showthr ... ?t=1022154 (http://forums.nasioc.com/forums/showthread.php?t=1022154)
This was one of the more helpful threads I found, not gospel but gives you a Good idea on n/a builds.

I've driven offroad a legacy turbo auto running a switch to go four or front wheel drive and it was pointless until I'd put it in four then it was a wild ride!
The turbo didn't come on boost until 4000 rpm which made me wonder if a smaller turbo would be more tractable with good throttle response?

The Stroker engined cars don't seem to have much traction either making me think a peaky motor (revvy) would be better to.


I'll post pics when I start the project and get links up of the legacy's videos as well......

[Huffer]

autox is typically on asphalt, not gravel. I think you're referring to rallyx?

A friend of mine has a ridiculous setup in his 96L Impreza, look him up on RS25.com under the name "Storm". He's chirping wheels through 3rd gear and destroying WRXs.

You're wanting a wide throttle response because on gravel you're going to spin the wheels more often. You'll want good turn in because you're likely to be hanging the rear end out a lot.

There's absolutely no reason why you couldn't use an EJ25 SOHC block with a 5MT and an rear diff from a 2000 Impreza RS as your basic setup. The idea of having high RPMs = lot of torque is not totally true, because it's WHERE the torque is generated that makes the difference, not making sure your engine can rev high.

[rougeben83]

2.5L with 4.11 or 4.44 FD. You need a flat torque curve and relatively short gearing, preferably you'd only need to ride 2nd through most of the course.

[turbodan]

It's called autocross in Australia and it's usually tarmac but this one i just did a round in is two cars at a time racing on a gravel track where you both take off from a set of lights then one car his the short track and one car the long track then there's a crossover where you cross from one track the other and end up flying past the finish neck and neck if your the same time around the track.

They only allow 2 wheel dive cars to make it more interesting and the quickest front wheel drive cars there understeer to get around quick but i just throw in sideways and settler into understeer and still got up there.

I've seen some awesome 2.5 Rs subys on that site and the torque curve and power is pretty awesome without getting overly expensive.

Thanks for the tips i accidently logged out or something and didn't get emailed about responses ;-)

[lord flashheart]

i built a EJ251 for a guy i go to the track with. it was 12.5:1 pistons and delta cams and it had a fantastic powerband. altho he had the rev limiter raised to 7500, and the cam profile was set up to breath best above 4500. i think it would have been more fun if the cam and tune was set up for a 3000-6500 rpm power band. at the track his car does absolutely awesome.