Surgery Underway

I finally managed to push the paying customers aside (sorry, everybody!) to get the Mach V STI on the lift for some extensive surgery. The tasks include replacement of the turbocharger with the Tomei ARMS model; installation of the TurboXS FMIC kit (see previous post); removal of the stock exhaust system in favor of a full TurboXS turbo-back exhaust; and replacement of the fog lamp bulbs with HID units.

So far the turbo is in place, and the bumper is off in preparation for fitting of the FMIC plumbing and core. The core is a generously-sized bar-and-plate unit. Bar-and-plate is known for efficient heat transfer and low pressure drop compared to cheaper tube-and-fin designs.

The exhaust is a full 3" mandrel-bent system. Although the STI has a dual-outlet muffler in stock form, this new system is only a single-outlet. If I was in full-on marketing mode, I'd say that was for weight savings. The truth is that TurboXS hasn't yet relased their dual-outlet STI system, so for now we're going to make do with the single-outlet that fits the WRX hatchback. But hey, we are saving weight...

I also popped in some cool color-changing turn signal bulbs for the front corners of the car. The stock turn signals double as side markers. I wanted those to be pure white, but you can't have white turn signals. These bulbs solve that by being pure LED-white while they're behaving as marker lights, but when they do their blinking turn-singal duty, they turn orange! It's very cool. I took a video:

FMIC and Harness Bar In the STIzzle

FMIC stands for "Front Mounted Intercooler," for those not in the know. All turbo Subaru models have their intercoolers up on the top of the engine -- that's why there's the big hood scoop. That top-mounted location means a very short pipe routing for the charge air, but it's not ideal for cooling. For that, the front of the car is perfect. Cooler intake temperatures mean more horsepower, and that's what we're after.

We chose the TurboXS front-mounted intercooler kit because we like the guys at TurboXS and we've done business with them for a long time. They make nice intercooler kits, with proper high-strength T-bolt clamps, multi-layer silicone couplers, and polished aluminum tubing. The extra-huge intercooler core should work nicely with the larger turbo we'll be fitting.

One interesting note about this kit is that it includes TWO different piping options, so it'll fit both the 2008+ WRX as well as the 2008+ WRX STI. The STI still uses the old-style aluminum manifold, with the turbo and stock intercooler separated by some piping. The WRX uses the newer plastic intake manifold, with the turbo outlet dumping directly into the stock intercooler. You'd need different plumbing for either option, so TurboXS thoughtfully included both with the kit.

Our kit is in a box in the showroom in front of our car. As soon as we can get some spare shop hours we'll be fitting it up. Stay tuned. In the mean time, I took one last picture of the car before the surgery...

In other news, we developed a harness bar for the 2008+ WRX/STI. This will allow you to mount four- and five-point harnesses in your car without having a full roll cage. We built and delivered the prototype bar to a happy customer during our Mother's Day Meltdown Spring Open House event, and should be building some production bars in the next couple of weeks. This isn't some slapped-together kludge part, either. Just to name one detail of this thing, we machined custom spacers to allow the proper freedom of movement of the factory shoulder belt even with the harness bar installed. Sure, it might have been easier to just throw some washers in there, but that's not the way we do things. Check our web site soon for pricing and availability.

Mwah Hah Hah! The Power Mods Begin

Okay, it's a small start, but we installed some Deatschwerks 750cc fuel injectors on the STI. These are a new type that use an OEM-style Denso core. I expected that they'd act a lot like stock injectors, but larger, and I wasn't disappointed. I plugged the laptop computer in and drove around the neighborhood with the computer data logging for me. A few adjustments to the "injector scale" constant, and the car was behaving just like it did before, just with lower injector duty cycles. The car is now ready for a bigger turbo.

Sharp-eyed blog readers will notice that previously I said I'd use 850cc injectors. Well...my relatively mild power plans don't really merit that large of a fuel injector, and I'm always preaching to MY customers how they should use only as much fuel injector as their power goals require, and not larger. So I thought I'd practice what I preach.

In general, the larger the fuel injector, the tougher it is to tune low-load and idle fueling. Cars equipped with very large injectors sometimes can't trim the injector flow low enough at idle, so they'll idle very rich, smelling of extra fuel out the tailpipe.

While I'm going back on previous blog promises, you know when I said the exterior of the car was done? Well...maybe not. Besides a front lip, which I wrote about before, I think I'm going to up-size the rear wing. Stay tuned.

The photo above doesn't really have anything to do with today's topic, but I liked it. I took it at sunset back on January 28, 2009.

Power Plans, and MPG

At this point our STI is pretty nicely set up in the handling department, what with the upgraded wheels and tires, Cusco coilovers, and Whiteline sway bars. And the car is looking pretty good, too. But the horsepower is still pretty close to stock -- the only power modification we've done is a Cobb AccessPort.

Part of the reason I haven't bolted a bunch of power-increasing parts on the car has to do with the engine failures we've witnessed among our customer base. (See my notes and pics below regarding that subject.) I confess I'm not very excited to think about having to pull the block out of the car to replace the pistons. Even if the likelihood of a failure is low, the expense (in both money and time) is pretty high.

Another contributing factor is that our service business has been growing and it's been a little hard to schedule work on our own car when we're full up with paying work. (That's not a bad problem to have!) The final factor is that like many of us considering the economic downturn, I'm a little leery of spending cash that I might need if the economic climate continues to worsen.

That said, I didn't buy this car to keep in bone-stock. The reason for having is to showcase what we sell and provide some first-hand insights about the parts and how they work. So here is our plan for power production on the car:

• Mitsubishi 20G turbo or equivalent (maybe a Tomei ARMS turbo)
• Deatschwerks 850cc fuel injectors
• Walbro 255 lph fuel pump
• Turbo-back exhaust system (with cat)
• TurboXS front-mounted intercooler
• Upgraded turbo induction pipe
• TurboXS intake

This should give a healthy amount of power (figure around 350 awhp on our Dynojet dyno) but still leave the car relatively civilized for daily-driver duties.

On a completely different note, I've been noticing that the STI's miles per gallon is still improving. I noticed this looking at me from the dash the other day...

Exterior Almost Done

The Seibon hood is now painted white. We left the vents in the natural carbon fiber just to give it some variety and to reveal what the hood is made of.

Some more details about installation on the hood: It uses the factory hinges and hood struts. Ideally, we'd find some weaker struts, because the original struts are very strong in comparison to the new lighter hood. The hood has holes for the stock windshield squirters, although the holes weren't quite bit enough, so we hogged them out a bit to fit. The original hood latch is bonded into the fiberglass, so it should be secure for the life of the hood, although if I was going to race this car I'd use hood pins in addition.

We also added Subaru's rear exhaust garnish trim, which are metal bits that surround where the tailpipes exit the car. I like the look of them, although not everyone is positive about 'em.

The exterior of the car is just about done. We're debating adding a front lip. It would enhance the look and improve the aerodynamics, but it would also make the car a little harder to use in the real world -- and who likes cracking a fancy custom front lip trying to get into some driveway?

In other news, we expanded the Mach V Media Empire with the addition of a Facebook page. (I think you'll have to log in to Facebook to view it.) Check it out, write on the "wall" if you want. Is this what we do now instead of watching TV? Collecting friends on facebook has a little of the feeling of collecting the Franklin Mint Fifty States Collector Plates or something. But what do I know...

Toys 'n' the Hood

We installed a Seibon carbon fiber hood on the Mach V STI. The pictures here show it in its raw carbon form (it's finished in a clear gel coat), but it'll eventually be white like the rest of the car. We'll probably leave the side vents in carbon just to show the underlying material.

The hood fits pretty well -- it's molded underneath just like the factory hood, and it's got holes for the factory-issue windshield washer nozzles. It does come with silver aluminum mesh inserts, which we thought didn't really look good, so we removed those. The factory hood scoop doesn't have any mesh in it either...

The original purpose of carbon hoods on cars was to save weight. In recent years, a lot of carbon hoods don't actually reduce weight at all. The use of lightweight aluminum on the 02-07 WRX and STI, for example, meant that a carbon replacement weighed the same as the metal hood. But in recent years the price of aluminum has soared, and Subaru went with a steel hood for the STI. At 22 pounds, the Seibon carbon hood weighs a lot less than the 45-pound stock one. Hooray for actual weight reduction!

Note that we don't have hood pins on the car, but I've always recommended people use them with any aftermarket hood. Still, the Seibon hood is made with a metal plate imbedded in the fiberglass that holds the hood catch. Given the minimal amount of use our car gets, I may hold off on the hood pins until some future time when we're headed for the race track with the car.

Brittle Pistons on 2008 STI?

We've heard of an alarming number of 2008 STI cars that suffered piston ring land failures. Once the ring lands break, the engine loses power. Repair involves removing the engine and rebuilding it. Many of these failures were on completely unmodified cars. Subaru issued a recall on the car to reprogram the ECU in an attempt to remedy this problem, stating:

During a quality review, we discovered that under certain harsh driving patterns, specifically when repeatedly or continuously operating the engine above the “red-line” (RPM above 6,700), abnormal combustion could occur resulting in serious internal engine damage in the form of broken piston ring lands. This abnormal combustion condition is the result of an “over lean” fuel mixture caused by a combination of fuel cut activation and high turbo boost.

I'm not convinced the problem is ECU-related. Most of the failed pistons show no signs of detonation, although I admit that doesn't prove it's NOT detonation that caused the failure. Various theories have been advanced on the Subaru message forum communities, including:

• Crankcase oil is contributing to detonation which results in piston failure
• New materials used for the piston castings are more brittle than older ones
• Solid (not sodium-cooled) exhaust valves create in-cylinder hot spots which lead to detonation.

Personally, I'm leaning toward the "brittle casting" theory. It just seems like the pistons are more fragile than in the older Subaru 2.5 liter engines. Given the general trend towards cost-reduction, it would not surprise me if Subaru changed suppliers and that the new supplier used a slightly less sturdy metal formulation for the pistons. The bad news for us if the problem is caused by the actual piston construction, is that we will not be able to fix the issue just by re-tuning the car, or by any bolt-on modification. Only an engine teardown and piston replacement would solve the problem.

This problem hasn't surfaced on our shop STI (yet), but we're keeping our eyes and ears open.

Thanks to the guys at Turn-In Concepts for the picture above.