Mach V STI Goes Drag Racing

My good friend Tom lives near Capitol Raceway, a quarter mile drag strip in Crofton, MD. He invited me out for the Friday Night "Test and Tune" drag races. Two hours of rush-hour traffic later, I was there at the strip. An eclectic mix of cars showed up to run, including: A Chevy van; a BMW 745i; a 2009 Dodge Challenger (which ran a 13.2); a bunch of 350Zs; a couple of Lancer Evolutions; one or two other Subarus; and a good selection of loud American muscle cars. There was also a VW Golf with an STI hood scoop on it. The big scoop, the one that looks like a snow shovel. It wasn't functional yet, but the owner promised that it would be. He said he always liked Subarus.

My timing was bad, so although I was at the track for about three hours, I only got to make two passes. (Various pro classes and motorcycles were being run between street car runs. And then various cars broke, requiring clean-up.)

On my first pass, I was so nervous I forgot to switch the throttle map to "S#" and to turn off traction control. I revved the engine to 4000 rpm, dumped the clutch and peeled tires for a split second...and then the revs dropped to about 500 as the tires hooked up and/or the traction control kicked in. Worst. Launch. Ever. The elapsed time was a shameful 14.645, with a 2.275 60-foot time.

After that I had almost three hours of idle time in the staging lanes to think about my second pass, so I had it together and switched the traction control off, and toggled over to "S#," which would deliver maximum power above 6000 rpm. I was relieved that the temperature dropped a bit as the evening wore on. It had been almost 100 degrees earlier in the day. By 11:00 pm it was only 80.

I staged next to a clapped-out Honda CRX with fat wrinkle-walled slicks sticking 4" out from the front fenders. The second stage light came on. I revved to 6000 ("Must not bog!") and held it there while the Honda did a loud burnout. He staged. The tree lit up and I released the clutch. I heard lots of tire peeling noise as the STI launched forward, and I briefly saw the Honda in my rear view mirror. I shifted to second, and about then the Honda blew past like it was going into orbit. I struggled a little with the next shift, but managed to get into third, then fourth. The speedo showed around 100 mph as the car went through the traps at the finish.

Final time: 13.667 at 100.32 mph. Not bad! The mph was a little lower than I expected, but a decent 1.758 60-foot time allowed me to knock a full second off my first pass. With a little more practice I think I could get another couple of tenths from the car.

Oh, and the Honda posted a 10.682 at 142.40 mph.

Stiff Stuff

Since increased chassis rigidity is always good -- especially considering we have greatly increased the suspension loads with the stiffer coilovers -- we applied Cusco chassis braces to the front of the STI. Underneath the engine, we bolted up a Lower Arm Bar, which ties together some of the front subframe bits, and replaces a thin steel reinforcement plate (that's the triangle shaped part) with one that's made from material that's twice as thick. If you know Cusco parts, you might notice that the Lower Arm Bar is gold -- this particular part was sold under Cusco's now-retired "Vacanza" brand. All the parts in that line were finished in gold instead of the usual Cusco metallic blue.

Up under the hood, we applied a Cusco OS upper strut bar. It only took a few minutes to install it. It looks like the bar leaves plenty of room for a larger intercooler, should we choose to add one later.

Cusco has not yet released rear chassis bracing for the 2008+ STI, but when they do, we'll be installing those, too.

First Dyno Results

We put the STI on the dyno and did some baseline passes. The car made a respectable 244 hp and 245 lb-ft of torque to the wheels. This is about what I'd expect from a car rated at 305 hp at the crank -- I use a rule of thumb of 20% drivetrain loss for an AWD car on our dyno. Hmm...305 times 80% equals...hey, it's exactly 244! (I guess I'll keep using the 20% rule...)

Then we switched to the Stage 1 map on our Cobb AccessPort, and ran the car again. The change was dramatic: 264 hp and 289 lb-ft! That's a gain of 20 hp and a whopping 44 lb-ft of torque. We did all these pulls within about a half hour of each other.

For the record, the weather was pretty hot -- the temp at the dyno was 98 degrees F, and 25% ambient humidity. This isn't ideal turbo-car weather, but at least both sets of runs were under the same conditions. If you are interested, that SAE correction mentioned on the graph means the numbers are scaled up by 2-3% to try to normalize for the heat.

I did notice that below about 3000 RPM, the car actually LOST a little power, and I've heard some other people complaining about that on the off-the-shelf Cobb Stage 1 map. We'll be doing some additional custom tuning on the car, so stay tuned for more gains, and (I hope) recovering that lost low-end power.

HyperFest 2008

On June 21, we took the STI to HyperFest. We didn't actually put the car ON the track, but we had it on display at our Mach V booth, and got a lot of nice feedback about the car. Many non-Subaru owners recognized that it was an STI, and knew about the car. "This is the new STI, right?" We continue to get HUGE positive response about the wheels, so it looks like those will stay, despite the slightly-too-low offset.

The drive to and from Summit Point was pleasant. Good weather, nice roads. The early morning light was good, and we got a few rolling shots of the car.

The HyperFest turnout seemed really big -- we had a lot of booth traffic all day long. Organizer Chris Cobetto said he suspected this was the highest turnout they've had.

Our booth was next to the Grassroots Motorsports magazine booth, and we got to chat with associate publisher Greg Voth. My not-so-humble opinion is that GM is a great publication, with some of the best technical content of any of the sports car magazines currently offered. Greg was clearly an enthusiast, and knew a lot about a ton of different cars. We talked about participating in one of their Subaru projects. If that happens we'll post here about it.

Photo Shoot!

We assembled a crack team of photographers and assistants -- okay, okay, it was just me -- to shoot the Mach V STI on a summer evening. Many mosquito bites later, we had a few shots we liked.

If you're interested, I was using a Canon 30D digital camera, with a couple of different lenses, and a tripod.

In my experience, it's MUCH easier to get good car shots during the "golden hour" right after sunset, or right before sunrise. Not only do you get nice sky colors, but the car details are also softened up a lot, and little flaws -- chips or small bits of dirt -- are less obvious. But it's tough because there's only about an hour, and setting up shots and moving the car and equipment around is time-consuming.

You can view more pictures -- and mega-sized versions of them -- over at this thread on NASIOC.

New Shoes!

Sorry, I promised dyno testing news, but I'm going to discuss wheels and tires first. The dyno stuff will come later.

Although the stock wheels and tires on this car are pretty huge (18x8.5" wheels, 245/40R18 tires), the fenders are simply gargantuan, and there's a LOT of room in there for bigger rubber. So, not being the type to leave well enough alone, I got out the calculator. Lessee...there's probably an inch of extra clearance...That'd be around a 275mm tire width. A wheel that was one inch wider would be 9.5" wide...might as well go up a size in diameter, mostly for appearances...So that means a 19x9.5" wheel, 275/30R19 tire.

Scouring our various suppliers didn't result in many choices. Most mondo-huge wheels are in lower offsets than will work on the STI. And some that would fit are boat anchors weight-wise, or wouldn't clear the brakes.

One promising wheel was the Rays G-Games 99B. It's really light at 21 pounds. (Trust me, for this large of a wheel, that's light!) It comes in the right bolt pattern and size. But the highest offset is +40. Still, I couldn't pass up the look -- it's like the stock five-spoke, but bigger and more sculpted.

For tires, the choices were again limited. 275/30R19 just isn't something you're going to find at the local Tires 'R' Us. Cooper Tire came to the rescue with their Zeon 2XS. Some of you tire snobs might be asking, "Why not Pirelli or Michelin or some other fancy-pants tire?" Well, to be honest, I didn't want to spend $300+ per tire, and I find that our customers don't either. So I thought I'd try this brand. Plus, Cooper sponsors our friends at CSI Racing, and the team has had good results with the Cooper product.

Here's the result. It looks awesome! To me, the car looks more to scale with the wheels -- the larger wheels reduce the car's bulky appearance, especially at the back.

But there's some sad news, too -- the +40 offset is too far outward, so both front and rear tires are sticking out from the fenders just a bit. We haven't done full testing yet, but it looks like the fenders and tires are going to come into contact at full suspension travel. In theory we could have the pad (the center mounting surface of the wheel) machined down, but I don't think there's enough material on the wheel to allow that. So it's back to the drawing board, looking for an even higher offset.

Check Engine Light Resolution

When we last left our heroes, they were struggling to diagnose a mysterious "Check Engine" light that showed up after the installation of an electronic suspension controller. As I mentioned earlier, I was studying the wiring layout of the car. Had we somehow nicked a ground, causing several sensors to go offline? Was something left unplugged? We went back over all the connectors -- everything was plugged in.

The other weird thing was when the ignition was switched to on, stuff started clicking under the hood. The radiator fan went on and off. I said, "It's almost like it's in pre-delivery test mode." Someone else exclaimed, "The test connector!" I had been looking for that earlier -- turns out it's over in the passenger footwell, not in the driver's footwell like on earlier WRX cars. Well, one of our well-meaning junior mechanics had been putting the interior back together after the suspension install, and seeing a connector unplugged...he plugged it in!

This test mode connector is only intended to be used at the pre-delivery inspection, to make sure all the systems are working. After that it's unplugged. And going back to the wiring diagram, sure enough, the test mode connector plugs into a junction that also attaches to the neutral position switch, which was one of the trouble codes the ECU was telling us about. So we unplugged it on our car, cleared the stored ECU trouble codes, and poof, it's a working car again.

Next up: Dyno testing.