Impreza 2.2 for FSP Autocross

[labman]

Hi All!

 

My friend and I are thinking about building an earlier Impreza Sedan into an FSP autocross toy. Why the 2.2? We have several engines available, and much practice keeping them running. We have not selected a starter car as yet, but are leaning toward one of the early ('95ish ?) 2 doors. In the end, however, it will be whatever we can get into cheaply.

Whatever, I wonder if someone on the list has been over this ground already, and would share their hard earned knowledge.

Note that this will be a dedicated autocross car, so we can do things like individual throttle bodies, or carbs, straight pipes for the exhaust, LSD rear end, and pretty much whatever we want with the suspension, wheels, and tires. What we do _not_ want to do is spend a whole lotta money on the project; if it gets too spendy, it's not gonna happen at all . . . What we do want is a fun car that is at least reasonably competitive at the regional level. (The drivers are going to be the limiting factor here, alas ;-)

Any thoughts (even if they're negative) greatly appreciated.

 

ByeBye! S.

[benebob]

Well I'm guessing since you wanna stay in street, then it will be street legal and be used to get to and from the events. Here's what I would recommend to start with

 

Buy the 4 door instead it's actually about 100lbs lighter as the 2 door had structure added to pass the crash stuff.

 

A decent set of used 200ish lbs springs (anymore and the stock struts will leak like there is no tomorrow). $50-100 on ebay.

 

Flush the brakes with Valvoline Synth dot 4 I think it is but it is as close to racing fluid without the horrible cost. Put on speed bleeders while your at it and replace your pads with a decent performance set like Hawk. Fronts only unless you have spare change lying around for the rears.

 

Ditch the seats (as I think you can for SP and get some Summit polyurethane racing seats or seat if you don't want a passanger. You'll have to keep your standard belt for inspection I'd suspect but get a 6 point harness to strap yourself down. $100 total for a seat and harness

 

Replace the 1st cat with a decent flow muffler then straight back beyond that. It'll keep you legal noise wise and provide enough back flow to keep the torque up.

 

An LSD rear is probably a waste as you'd really want the LSD front.

 

Spend money on tires and light wheels!!!

 

 

Give the car a diet- 100lbs is equal to 5hp!!! Get a rulebook and see what bolts, hangers, brackets, ac systems etc you can loose. We took about 40lbs of bolts alone off our svx! Loosing weigh below the center of gravity though isn't good so higher weight is much better!

 

Get a professional racing alignment and corner weights with you in the car then move the battery appropriately

 

For about $2000 or so (provided you get a $1000 Impreza) you should be fine to start with.

 

Get yourself a rulebook after the car and keep reading the rules until you know everything about 'em.

 

Check out Hocrest and my SVX E Prepared race car at my link below. We might have $1000 or so in it not including tires or our trailer. It weighs less than an Impreza does and in our region it took 1st and 2nd in E Prepared in 05. Not bad for a car that was a parts car in Nov of 04 and has gone through a ton of variations over that time.

 

A word though is SP is a very tough road as you have all the tuners with a ton of money and support in it. Might want to think about going all out into the prepared catagory (provided you can have axcess to a truck and trailer). Then you can go out and get yourself into real racing (hill climbs, etc without much more work.

 

I'm sure some will say that coilovers are better, my exhaust suggestion isn't the fastest, etc but bang for buck it should be pretty much dead on for ya. Then if you have spare money put it towards seat time (preferably competition classes or the like) as you said it best the driver is the limiting factor. Sure some cars are more competative and in reality no subaru is that good as an autox car from the get go but you'll have plenty of fun!

[labman]

Hi Benebob!

 

Thanx for the re, just the kinda stuff I am looking for. FWIW, I've been campaining an '85 MR2 in CSP the last few seasons; looking to go with something Subaru, as I will be getting major support from my buddies "Subaru only" salvage business. (Plus maybe then he'll come out and play with us; he's just too darn big to fit into my little Toyota.)

"Street legal" is kind of a gray area; nice, but not strictly necessary. We have numerous *SP cars in the region that don't wear license plates, and since the intake and exhaust is open for mods (right up to the port window on the head, I think), that is why I mentioned individual throttle bodies or (more likely) carbs, and the straight pipes. Don't know how much difference it'll make on the 2.2l motor, but it seems to be a popular mod for the ea81/82 engines. I plan individual pipes for each side, terminating in Supertrapps to keep the sound patrol happy (93dB for some venues we use), and to tune back pressure. Most of this stuff is already in the junk box; just needs to be properly applied.

Light wheels, and type R tires for sure; as small in diameter as possible w/o forcing a shift to 3rd on faster parts of the course. Probably V700 Kumhos on 13in alloys if I can find a set that'll fit.

The 4 door is really lighter, huh? That's counterintuitive; the 2 door version just looks _smaller_ somehow. Finest kind; there's a bent-but-probably-fixable '94 car gathering dust in the yard right now. Mine!

I was planning a real stiff (500+lb) coil-over kit, but as you note, the stock struts certainly aren't going to be able to control anything very much heavier than the OEM springs (150-160lb?), and they don't really do a "sporty" job with those. I had thought to dissect the stock cartridge and try to fit a Tokico Illumina insert (I have a spare set from my MR2) into it. Or maybe modify a (Shhhh!!) Toyota strut housing to bolt up to the Subaru hub, they're reasonably similar. Then use the coil-over to lower the car as far as practical, and more or less balance the corners. What about camber? Any idea if the camber plates available for the WRX cars will fit the earlier Imprezas? Guess I'll take a tape measure to someones Rex and find out. Crash bolts will probably serve in back. And the stiffest bars I can find to fit, seems like WhiteLine lists bars for these cars, and they're not too expensive. What do you do for the SVX? Also, do you retain the power steering, or have you swapped in an armstrong rack?

Proper autocross alignment is a given, as is stripping any and all excess weight. Probably will fit a simple roll bar so we can use a real 5 point harness, and install a light weight aluminum seat. Or seats; I think you have to retain the passenger seat in FSP. Don't know for sure about the back seats, but they're not too heavy, and I can probably chop most of the steel out of the rear seat back, as no one will be riding back there anyway.

We _have_ an LSD rear diff that'll work, so might as well use it, but a _front_ limited slip??? I thought that was a no-no; causes severe steering issues. Any details on accomplishing this?

Guess my main concern is squeezing some extra from the motor; the 2.2 is a torque monster, but flattens out pretty quickly. I can burn off clutch facing to get around lack of bottom end (I _did_ mention that I race an MR2? ;-), but that flat response curve above ~4K has me concerned. And I'm not convinced that shifting buys much time on course, especially back and forth across the 2nd-3rd gate. "Nice" would be a snappy pull to a 65-70MPH redline in 2nd. "Really nice" would be also figuring a way around the OEM 6500 RPM (I'm guessing) rev-limiter w/o buying aftermarket ECU parts. These are things dreams are made of . . .

BTW, your link didn't make it onto the posting. Give it another shot; I'd love to check out your car.

 

ByeBye! S.

 

--

Steve Jernigan KG0MB

Laboratory Manager

Microelectronics Research

University of Colorado

(719) 262-3101