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Dear Dave

Geek-At-Large

Dave Coleman
Jan 1, 2008
0709_sccp_01_z+dear_dave+funny_pic Photo 1/2   |   Dear Dave

Direct 'Dear Dave' tech letters to: dave@eyesoreracing.com
Coleman will share mind-numbing details, earth-shattering revelations, and technical nerdisms in this space each month.

Q. Ballistic Toaster

I have a 2004 Subaru Forester XT (2.5-liter turbo) with a manual transmission. I've been told that this is a WRX platform and was wondering where I should spend my money in modding it. It won't see much, if any, track use and it's still my daily driver. I've heard there is a Forester STi suspension set-up to improve handling, but I'm not too sure where I should go with power.

I'm trying to mod something a little different and make some of the VW and Nissan drivers think a little before messing with me. The plan is for an all-round sleeper wagon with light-to-moderate snow duty in the winter.

Bunmi Aremu
Manassas, VA

Answer

I did a day-after-Christmas drive from San Francisco to LA in a Forester XT and my life has never been the same since. The day started dreary, staring down the barrel of a 400-mile traffic jam but, about 75 miles in, the Forester opened up a whole new world.

Interstate 5 is a straight, featureless four-lane hell stretching across the vast, arid plains east of San Francisco, made incomprehensibly worse by thousands of restless, angry vacationers brake-checking each other. After 10 miles of this, I was ready to shoot myself. After 50, I was ready to shoot everyone else.

At mile 75, I got off at the only exit for 15 miles in either direction. There were no paved roads here, only a quartet of packed gas stations with lines of pee-pee dancing kids. Unable to face the crowds and unwilling to rejoin the southbound conga-line of rage, I pointed the Forester west and mashed the gas. Destination be damned, I needed out.

The road devolved to a pair of tire tracks skirting the edge of a dirt farm. The Forester devoured the rutted trail at 70mph. When I finally came to a fence, I turned left, on the logic that south is the direction of LA, and at least I could get lost in the right direction.

I did get lost. Fantastically lost. The roads went from dry dirt, to pot-holed pavement, to deep mud to snow. I stumbled upon New Idria, an abandoned mining town that once survived by digging lead and asbestos out of the ground and poisoning the world with it. I passed slack-jawed ATV riders whose sense of isolation was shattered by the sight of a suburban brat-fetcher powersliding past them in axle-deep mud. The stress of holiday traffic was forgotten, replaced with an unparalleled sense of freedom and invincibility.

When the dirt ended, I found myself on Highway 25, not only one of the best back roads in California, but also decidedly in the right direction to get me home. Here, the very same vehicle that just carried me through the slickest and thickest stuff nature can concoct out of mere dirt and water turned into a sports car. A tall, boxy, kinda sloppy sports car, but pretty capable nonetheless. I attacked the road with triple-digit pace, hurling the big wagon into lurid drifts and leaving four skidmarks out of every corner. There is no other car, I'm convinced, that combines back-road joy and off-road agility so effectively.

What I'm trying to say is: be careful how you tune this thing. If you follow the standard bumpstop-thumping tuning process, all you'll end up with is the world's dumbest-looking lowrider. If you don't maintain the Forester's any-surface flexibility, why are you tolerating its cardboard-box styling?

I've never driven a Forester STi. It's probably good, but I'm a cheap bastard, so here's what I would do: prowl the forums for someone upgrading the suspension on their WRX STi and buy their stock suspension on the cheap. Mounting points are the same, but the WRX's shorter struts will drop the car over two inches.

0801_sccp_02_z+subaru_forester_xt+front_view Photo 2/2   |   Dear Dave

The rear will probably sit slightly low when you do this, thanks to the weight of all that SUV back there, so cut the front springs. No, seriously. The STi suspension has plenty of travel to spare and trimming just a quarter to a half inch of ride height off your front spring should work with few side effects.

You should also install the STi's rear bar. It almost bolts in (the bushings are slightly different) and will make it a lot easier to get the tail rowdy when you want.

The brakes are easily improved by swapping to a 1-1/16-inch master cylinder from an Outback VST (part number 26401AC220S1) and the sloppy steering can either be improved with a WRX rack or completely revolutionized with a quicker STi rack (for the STi rack to fit, you need one from a pre-2006 car). Upgrade to polyurethane steering rack bushings, the stock ones loosen up quickly and make the sloppy steering even worse.

For power, I'd continue my cheapness by simply upgrading to a used STi turbo and intercooler, which will get you 95 percent of the way to having an STi engine. You still want flexible low-rev torque for getting up muddy hills without igniting the tires.

And stay modest with your tire sizes. Run snow tires in the winter. Use a summer tire with a tall sidewall and an M+S tread pattern that might be able to handle the occasional off-pavement adventure.

If those Volkswagens or Nissans start messing with you, just drive off the side of the road and hit the gas. I bet they won't have the balls to follow.

Q. Light Or Balanced?

I'm 'restoring' a 1990 Eclipse GSX for light track use. The car doesn't have the greatest front-to-rear weight balance in stock form. Is it more important to try to shift weight to the rear, in an effort to get a 50/50 balance, or to lighten the car overall? If I pull out the back seats and rear hatch trim, I lighten the car, but more weight bias is shifted to the front.

Mike McDermott
Downers Grove, IL

Answer

An excellent question. Do you want to go fast, or have fun? A nose-heavy car handles poorly because the front tires are more burdened than the rears. In virtually any kind of cornering situation, the fronts will run out of grip first, giving relentless understeer.

Removing weight from the rear will help both ends slightly (the front tires don't have to work so hard at slowing your heavy rear seats and hatch as you brake into a corner), but the rear will gain more from the transaction, giving the back of the car proportionally more grip and possibly causing even more relentless understeer.

Thing is, it'll be going faster as it understeers, so the joyless lapping session will end slightly sooner. Remember, the load on the front tires is the factor that limits cornering speed. And you haven't done anything to increase that load. There may be some corners where trail braking is less effective at making the car rotate, so there is a possibility that you'll give up a little in a few places. But ultimately, your lap times should be faster no matter where the weight is removed.

As you start shifting weight around, this question will come back time and again. What if the battery is moved to the back? Taking 25 pounds off the front wheels and put it on the rear will help even things out, but two or three pounds of battery cable will be added. Is the extra weight worth it? On a nose-heavy car like yours, it is. But on a rear-driver already nearly 50/50, maybe not. Either way, consider a lighter battery.

What about location? Should the battery go all the way to the back of the car trunk, or just behind the seats? Here, the answer is more complicated. The various mounting options are usually at different heights. Lower is always better, as it will reduce the amount of weight shifted to the outside tire.

Tempting as it may be to move the battery to the back of the trunk to maximize the impact on weight balance, this effectively creates a pendulum. If you are successful at finally making an Eclipse oversteer, the extra yaw inertia of that lead and acid swinging around in the tail will make it harder to catch the slide, and harder to bring the tail back in line without overshooting into a demoralizing tank-slapper.

On front-drive street cars, I prefer to use the front of the trunk, as low as possible. On front-drive track cars, I'll move it to the rear passenger's floor, which is lower and causes less yaw inertia. My Silvia is fairly well balanced already, so I dropped to a 13-pound Odyssey battery and mounted it to the passenger's floorboard, under the passenger's knees. This put the weight low, nearly at the center of the car, and kept the battery cable under six feet long.

By Dave Coleman
94 Articles

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