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YimiSport Tuning Subaru STI - Driver Training

Driving The Doors Off This Subaru At The '09 Modified Tuner Shootout

Mike Speck
Jul 13, 2009

It's weird how things work out sometimes. For instance, you'd think that when you assemble some of the best tuners in the country for an all-out performance shootout-with all the variables that are entailed in such an undertaking-you would end up with a completely different set of results each year. That's what you would think, or least that's what I thought. But if you just look at the results from this year's and last year's Modified Tuner Shootout at Firebird Raceway in Arizona, you couldn't be faulted for doing a bit of a double take. Last year's Modified cover shot of the event showed the GST Subaru Impreza up front, the Full-Race supported Subaru STI just behind and a brand-new Nissan GT-R completing the picture. You'll see the same thing on this year's cover as well because the results ended up the same. The results are only a small part of what took place this April in Phoenix, though, and the real story is how we all ended up where we did.

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For me, it was another podium runner-up finish in a Full-Race turbo-powered car, this time built, supplied and street-driven out from California by the great guys at YimiSport Tuning. YimiSport is a Subaru/Mitsubishi performance company based in Santa Clarita that offers services ranging from simply putting on the go-fast goodies all the way through to doing complete build and tunes of reliable street/track monsters. They were kind enough, through a little coaxing from Geoff Racier at Full-Race in Phoenix, to bring their new '08 silver Subaru STI down for a crack at the tuner competition.

We knew that as a full-weight street car on used rubber we would be at a disadvantage in some respects, but as it turned out, power would not be a problem. To make sure the car would run on track without reliability issues, we shook the Subie down at the Bondurant circuit a couple days before the shootout. Right from the get go, it was obvious that the Yimi guys had built a nice piece. Not a race car by any means, but certainly something that could potentially turn a decent lap or two.

We decided that for the shakedown run we would let the car loose a bit and run what we felt to be maximum boost that would allow the best possible power-producing induction without doing damage. It would be better to find any potential problems during the test as opposed to having something break during the actual competition. Despite an intermittent smoke cloud of burned oil that we traced to a relatively easy-to-fix oil pressure and seal issue, we had no problems with the car.

The first day of the competition was April 10, and YimiSport owner Paul Yim along with lead tuner Paul Leung decided to run the same boost during the dyno pull, which was the first element of the four-element shootout program. At 30 psi from the Full-Race rotated twin-scroll BorgWarner S300X83-75 turbo, the '08 STI put out a ground-pounding 550 whp! For a car intended to turn multiple laps on a race course and then be able to drive all the way back to California, that was an amazing number. And believe me, during our short test the day before, the car felt incredibly strong. It would later go on to turn an 11.5 at 124 mph on cold tires on the dragstrip at Firebird Raceway, and at the Bondurant circuit it reached 123 mph on the longest straight.

Just to put that into perspective, a Carrera GT on the same road course reaches 125 mph before the braking zone and an Enzo just touches 128 mph. Don't get me wrong here, I'm not saying that the YimiSport Full-Race Subie is a million-dollar Ferrari or the world's best Porsche, all I'm saying is that in a straight line with 30 lbs of boost, it was bloody fast!

Just adding a blower with monster boost doesn't make for a reliable car, though, so there needed to be some beefing up of the internals. The fast-thinking, quick-speaking and immensely capable Mr. Leung addressed the potential reliability pitfalls of running category 5 hurricane-force winds through a stock motor by using a YimiSport Stage 1 short-block. Additional YimiSport parts and pieces used to ensure that the Subie boxer didn't explode in a mass of smoke and fire at 8000 rpm included 1mm oversized valves, a set of ported heads and a YimiSport air-oil separator.

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To handle the staggering amount of air that the Full-Race twin-scroll turbo forced through the flat-four, YimiSport fabbed a custom front-mount intercooler along with a custom 4-inch intake. The post-combustion release of air was vented out through a set of Full-Race custom-fabbed headers and down a YimiSport twin-catted race exhaust with what appeared to be stock exhaust tips. The sound at idle was raspy and very Subie in its lopey rhythm, but it turned into a sharp, ripping pitch of fury at full throttle and full boost.

Finally, and perhaps most importantly to both performance and reliability, YimiSport looked closely at the engine management side of the equation. The guys ultimately decided on a Cosworth ECPro stand-alone unit. Perhaps Leung put it best when he said, "The Cosworth ECPro allowed me ample control in mapping out a tune that gave us plenty of power but with a wide margin of safety for circuit racing." Indeed, despite several laps running in testing, we had no engine management issues, and I really did run the car as hard as I could.

Although it was clearly very important to make the '08 sliver missile a streetable machine, YimiSport still thankfully felt compelled to address the suspension tuning to help the car in track use. They used a combination of KW Clubsport coilovers with a gaggle of Whiteline bushings, sway bars, anti-lift kits, end links and various chassis-stiffening braces. Hoping to make the most of the suspension upgrades, we decided to roll on a set of the same super-sticky Hankook autocross slicks that we had used the previous year, except that they were well used (what do you expect for $25 a tire?). In the end, even though our budget may not have allowed for it, a new set of the Kooks probably would've been a far better choice, but we still made the best of it.

Race day for the shootout dawned cloudy but dry, and we were all pretty excited about seeing what we could do in the driving portion of the event. The strong dyno pull put us just behind the GST car that cranked out an absurd 600-something whp, and we all sensed that we might have another shot at the top three again! The weather decided not to cooperate, however, and just before the autocross portion of the event, the heavens opened up and turned the autocross into a full skating rink.

We went full soft on the suspension all the way around and popped on a set of used rains and decided to just go for it. I basically just did what I could on the tight and twisty autocross, but to be honest, I struggled in almost every respect. I found it difficult to put power down, I missed my braking points a couple times and even flat-out got lost when the windshield fogged up on me. I could tell the two Pauls at YimiSport were a bit disappointed in my lackluster performance, and frankly, I was a bit bummed out myself. You learn pretty quickly in this sport that a) you can never quit, and b) you have to roll with good and the bad-it's just part of how it all works. While I think I probably could have done better on the first driving event, I was eagerly looking forward to the time attack

Once the points got tallied, however, we were still solidly in second, making us all feel quite a bit better. Our runner-up position was partly due to Crawford not running its car in the atrocious rainy conditions and as such Tarzan Yamada took a big points hit.

Next came the dragstrip, which luckily ended up being held during a brief break in the rain and on a dry but dusty dragstrip. Brady Dohrmann jumped aboard, just like last year, and turned a neck-snapping, 11-second run on his first sitting in the car!

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The uncharacteristic April weather continued to throw us a few curveballs, though, and there was continued sporadic on-and-off rain. Unfortunately, we never got any dry time on the Firebird circuit before the evening time attack and final portion of the event. I did get to run a short wet session just to try and get some type of wet-weather handling package under the car in the event that we had to run the time attack in the rain. It turned out that the setup was harder to nail down than a shingle roof in a tornado, and although we ran some pretty competitive times, I was taking some big chances to get us there.

Finally, the evening time attack event came up and conditions were dry and predictable. We immediately went back to the Hankook slicks and stiffened up the shocks and bars. We knew that we weren't going to catch Gary Sheehan in the GST Subaru unless it broke, but we also knew that we had a healthy lead over the Third Place Nissan GT-R and Fourth Place SOS Honda NSX. Even though I really wanted to turn a good lap for bragging rights, I'm nowhere near cocky enough to think that I can go quicker than Tarzan or Sheehan with me in a street car and them in more properly built race cars. And on top of that, we had Second Place secured as long as we didn't blow up or have me crash us out of the running. So we turned down the boost from 30 to about 22-23 and set off to see what we could do.

The YimiSport Full-Race power was still strong, but nothing like it had been during the full-boost test, and I still found myself waiting for the boost to build longer than I would have liked. I drove as hard as I could, pushing the limits in all the braking zones, especially turn 1. With an indicated 142 mph at the end of the Firebird straight, I knew we were giving up a bit to some of the other cars and I tried to make it up by braking as late as I dared. Of the three timed laps that we were allowed, I was pretty sure I was going to kill myself in a couple of the corners on at least two of those laps. I was pushing so hard that the brakes glowed cherry red long after the car came out onto the straight, and one of the photogs said he actually saw the Brembo Grand Turismo brakes on fire once! Stopping power was decent, however, although there is only so much that one can expect in terms of slowing a 3,400-lb car from triple-digit speeds, but as always, I knew that the Brembos would be up to the task.

When it was all said and done, we turned a 1.05.4, good for the third-quickest lap overall and a little more than 3 seconds off Tarzan in the Crawford car and the GST Subie with Sheehan at the wheel. Our lap increased the gap to Third Place, made me feel better about my driving for the day and gave me something cool to write about for the column. Plus, and perhaps most importantly when you look at this whole process from a business standpoint-and believe me, this sport is about business-it made the trip for the YimiSport guys worth the effort.

I was content as we lined the top-three cars up for the cover shot at the end of the event. There were well-deserved congratulations to Sheehan and the whole GST crew with more than a little champagne spray in the air. As I told Sheehan later, they earned that win all the way down the wire. It would have been exciting to have Tarzan run the whole competition, but I guess we'll have to wait for another time.

Watching the two Pauls that are the brains behind YimiSport driving the 500hp, '08 STI back to the hotel after a very long day, it dawned on me again that this car was proof that with some good thought processes and some solid equipment, a street car can be made to do some amazing things. I'm looking forward to what we might be able to do next year.

By Mike Speck
15 Articles

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