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DrunkenBoxer 2.0

29K views 142 replies 22 participants last post by  ImprezaRSC 
#1 · (Edited)

40-80 5.0s. 93 octane. No boost. No exotic fuels.



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Overview

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.

Goal

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.

Parameters

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.

Engine

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.

Exterior

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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#34 · (Edited)
I can't believe how much timing this engine likes on 93 octane. Holy crap. You'd never get away with this in boost. Between that and tuning the injector timing, I found the "handful" of torque that the old motor had. Revs get more and more snappy as I figure out the combination. The torque also feels chunky again, like the 2.5L did. It's fun to drive even without AVCS hooked up. I can roll into the throttle and screw with people in gear like the old motor did :monkey:.

It's a lot easier to drive on 93 than E85, but I hadn't rolled these new tricks into the E85 mapping. The adjustability provided with the software is letting me dial things in to a very fine degree and clean up the fuel mapping. The twin throttles are still very forgiving. I have to set them right and then they're happy, instead of constantly having to sync them like ITBs. I have to find what the engine likes since this all completely new. There's a mix of radical and conservative in it. The mechanical compromises are there to maximize the fun and ensure longevity. The ECU tuning lets me smooth it all out. I've put about 2,000 very forgiving miles on the combination. Mileage hasn't been too sharp, but I'm working on that.
 
#37 ·
Here's some mile acceleration testing. Crank up the sound :). I think you can see the potential with the combination. Once the redline is raised, all that shifting becomes unnecessary. It's still a little mismatched without a higher redline.

My latest 93 tune is the 2nd mini clip with a little more midrange timing and better fuelling. I'll make an E85 clip sometime soon. There are a few tricks in this tune that aren't in the E85 tunes.

 
#39 ·
One of the bugs I have been chasing is this bog at low-mid rpm and high load. I was a pansy and not adding timing due to higher compression. Man, was I wrong. This combo likes a stupid level of timing on 93. This map has more spark timing than it did on E85. It's a bad, bad girl. I was keeping timing out of it in high load situations and it just wants more.

Naughty...
 
#51 ·
Sup G,
I've been busy and completely forgot about checking this out.

In regards to "this bog at low-mid rpm and high load"
Is this the same bog all RS'es have? When still NA I sorted mine by correcting my car's grounding. Never had that dip again.

Stop by the shop (610 Pratt Ave. NW) sometime.
 
#53 ·
Bumpdate.

I'm making some interesting headway with further tuning.

The twin intake allows very high MAP readings at very part throttle. It can hit 96kpa at 20% throttle. This is a common theme among ITBs and is nothing new or shocking. I'm working on using this fact of life to my advantage with tuning. The advantage over ITBs with this setup is having longer runner length, a stable MAP signal for all cylinders, and relative mechanical simplicity. This makes tuning a little easier for me. However, the combination is so new, that there are no base maps for me with start with other than a stock map. The bugs are new, too.

I admit to fumbling through the dark just a little bit to find the right settings. I'm happy with the car, but perfection in the tune has been a little hard to come by. Compromise keeps rearing its ugly head. I have to drive the car like a complete wuss in traffic to avoid tickets. What works in lower gears doesn't work so well in higher gears. I have to work the throttle to get the most out of it. My friends and I agree it is like playing an acoustic Subaru instead of an electric Subaru.

N/A's are forgiving of mistakes but demanding of precision (until you run crazy compression, big cams, nitromethane, etc.) I've been hunting for that precision a little bit at a time, whittling away unnecessary bits. I've chased down a thermal bug that causes the idle to change with different weather. Mike has provided a few new tables for me to work with, like programming the IAC. I was working with the IAC tables before figuring out the thermal issue and addressing it physically.

So far so good. The noise gets to be a bit much at times, but I'm sleeping in the bed I made. It does make a quiet daily sound very, very nice. I would not have signed up for this if I thought it wouldn't work or wouldn't love it. I spend more time under the hood making improvements as opposed to mistakes or fixing problems. Less seasoned people would be bugging the hell out of a tuner over every little thing that I accept as simply part of life with this choice. The car would not even be running if I had not stayed on top of things and applied myself to finding the solutions needed.
 
#56 ·
I think the biggest detriment to performance is the inactive AVCS. No real cam overlap kinda kills the fun. If I could raise the redline, then it would be a lot better, but I digress. The whole combination is an experiment and is as reliable as one could expect. My next motor will have static cam gears. AVCS when not hooked up will still move around a little with oil pressure, but not enough to really help or hurt. They really need to be degreed correctly.

I can switch up between 93 and E85 pretty easily. It takes a little driving to let the car relearn, but it adjusts fairly quickly on the change up. Mixing fuels doesn't hurt either way, so I can change up at 1/4 tank and it runs fine. I still have not tried 104 unleaded. That should be fun.

Sorting the mundane details have kept me busy. I am still stripping weight out here and there, whittling a piece at a time.
 
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