2000 2.5RS BRP
Youtube channel: ImprezaRSC
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Blog: Tinkerfreak's Tech & Adventure Blog | Shenanigans of a Rabid Inventor
Welcome to my budget rebuild of the original E85 powered 2.5RS. It has been my trusty steed for 17 years and was due for a rebuild. After 100,000 miles on E85--and picking on turbo cars --I wanted to top that on a reasonable build budget. What fun is just another turbo swapped Subaru? Box 6s? Been done. I love developing new stuff as much as turning old stuff into new stuff. I also love autocross. There's room for both to make a fun and reliable daily that doubles as a weekend track car. What every hobbyist loves are the stories we hear and make for ourselves.
I am using a classic Impreza and making it look even older, like a "what-if" mashup. What if Subaru had entered the GC chassis into SCCA's heyday to duke it out with the Datsun 510 and BMW 2002 and scrap with the Camaros and Mustangs? It would be styled a little older. You'd see a lot of hand fabricated parts and some battle scars. It wouldn't be turbocharged, likely on a dual carb-like arrangement. It would be stripped for weight. You'd see labor that adds up to less being more. I also love the Harley-like N/A voice that this has. It grunts and snorts like a V-twin bike with pipes. You see and hear that nasty idle. It sounds like it should be a more raw kind of vehicle and ****ing own it at the same time.
Fast. Reliable. Cheap. Pick Two...
With any good project it is a good idea to define the parameters and the scope. Reliability was the primary goal. Speed and power were less of a priority. $4k was the financial ballpark to do the entire thing, a relative shoestring budget with some wiggle room. The end result is part junk yard dog, part sleeper, part freakish experiment, part OEM rock, and part troll car :monkey:. This was an incredible amount of labor, too. That was the trade-off of the lower cost; doing or knowing who was doing the labor. Because race car? No. Because I can.
Some of you are probably asking "so why no boost"? It was a matter of reliability and cost containment, again. Pesky issues, but manageable. This build was stuck on a 4:11 5spd. We know this gearbox doesn't hold up for very long under boost. But, is fun to drive being shorter geared. That meant following other routes to get the speed, like weight reduction. Weight reduction also improves reliability, the other more important goal.
How can we coax more power out of this n/a engine arrangement? Well...there's using the same bolt-ons as everyone else for the last 20 or so years. What fun is that? The same problems. The same limits. The same character. Meh. I'd rather start over with fresh paper and color in all of the details. That can be a badge of honor as much as a cross to bear. I dare to help reinvent the genre, on a small budget. Challenge accepted! Let's start by letting more air and fuel in with multiple throttlebodies. Compress it a little more, and then let it out more easily. Along the way, we'll rev it a lot higher and give it enough air and fuel while it's there. The trade-off is using a slightly smaller stock engine to get it all done. An upshot is 250lbs less of turbo equipment. That's also weight to lose by never installing it to begin with.
Despite the cost constraints, we're aiming for as much power as the 5-8psi intercooled turbo kits from back in the day. 260-280hp from a smaller 2.0L is actually a pretty reasonable goal while n/a, but not with the same off the shelf parts. We've known for a while that these n/a engines can make as much power as stock turbo cars or the bolt-on turbo n/a cars. This build is to push that envelope a little, while still on stock parts. The trade-off is less torque for being able to spin the smaller motor higher. It definitely drives differently, but not unpleasant underfoot. This build was very much a game of compromise.
The rest of the car is still getting some TLC and fab along the way. The bullet mirrors were an homage to 60s SCCA cars. In respect to that, I'm "adding lightness". The interior panels are getting stripped and replaced with aluminum skin where needed. The carpet is gone. The sound deadening still needs to come up. The floor will be smoothed and painted over the summer. The sunroof will be treated to a targa-style mod for manual use and removal, a bit more like a Jeep top. I love the roadster feel of this car and the rest of the build is meant to enhance that.
Suspension & Brakes
The modded suspension is unchanged, with Prodrive P1 springs on gr2 struts, 20mm STI rear bar, and your typical anti-lift kit, upgraded mounts and bushings. With the interior stripped, it sits at stock height. The power isn't there to need huge brakes and big tires. It might need some stronger braking after getting the power dialed in, but it should not need Brembos or anything too pricey.
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