Project Matrix: Part 1

"That kicks ass!"

Hmm, do go on.

"I could take one of those, dump it on some 18s, turbocharge it, pick up a bunch of friends and...I don't know what."

Without knowing it, our impromptu one-man focus group answers the question that's been puzzling us for weeks: What do you do with a project car like the Matrix? The raw material is something we've never seen before: part sports car, part station wagon, part truck. In a way, it's what an SUV would be if it didn't suck--stylish, surprisingly utilitarian and still not a pain in the ass to drive. But which way do you go when you modify it?

In a simple, 10-second fantasy session, our man on the street makes the whole question seem stupid. Do the obvious. Accentuate the sports car side, leave the utilitarian side alone and hope your friends have some idea what to do next.

Why turbocharge it?

It's not as dumb a question as it first appears. We could, after all, supercharge it, throw some nitrous on it or even push the naturally aspirated envelope further. Looking at the Matrix as it will come from the factory helps point us in the right direction, though.

It's light for what it is, but the Matrix is still 268 lbs heavier than the Celica with which it shares drivetrains. Where the gearing is a tad too tall and the powerband too narrow on the Celica, the Matrix's extra weight and taller tires--which effectively make the gearing even taller--exaggerate both problems. The Matrix needs more grunt when the VVTL-i system is still on the small cam, but most naturally aspirated mods will only make the powerband more peaky.

Supercharging seems like the obvious answer to our quest for torque, but any positive-displacement supercharger will require complex mounting and belt drive mechanisms and will be difficult to intercool. With 11.5:1 compression, forced induction is already a pretty crazy idea; forced induction without intercooling is certain death.

Turbochargers have a reputation for being peaky, but with a properly sized turbo, making boost--and torque--at low rpm is easy. A compression ratio of 11.5:1 provides plenty of exhaust energy to get the turbo going, and since turbos mount and breathe through easy-to-fabricate pipes, intercooling is relatively easy. And it doesn't hurt that we already know where to get a turbo kit for the Celica, either. XS Engineering built the first turbocharged Celica GT-S about a year ago and has all the hardware and experience to do it again.

All the intake and intercooler plumbing will be different to fit the Matrix engine compartment, but the exhaust manifold and downpipe--the two most difficult parts to fabricate, can come straight from XS' Celica kit. The rest of the plumbing can be fabricated in about a day.

The Fuel System
As with any turbo kit, tuning is the key to success. Since the Matrix is only making about 7 psi of boost, XS simply uses a rising rate fuel pressure regulator to toss in some extra fuel when boost comes on. Problem is, this seemingly simple solution requires a complete redesign of the stock fuel system.

The Celica, the Matrix and most cars introduced in the last two or three years use constant-pressure returnless fuel systems. A few years ago, all fuel systems had a return line, so a bunch of fuel was pumped up into the fuel rail, some was injected into the engine, and the rest was sent back to the tank to try again.

Fuel pressure in these systems was simply regulated by restricting the flow of the return line. The more you restrict the return, the more pressure builds up in the rail. Fuel pressure would also change as you drove, always staying constant relative to the pressure or vacuum inside the intake manifold. This design makes it easy to increase fuel flow through the injectors by adding another restriction to the return line--the rising rate fuel pressure regulator--which would increase fuel pressure even more when the manifold was boosted.

With the new, returnless systems, however, there's no return line to restrict and fuel pressure doesn't change with manifold pressure any more. The regulator controlling fuel pressure is all the way back in the fuel tank, and there's no easy way to make it change with boost. In order to use a rising rate regulator, XS had to convert to an old-style manifold referenced return line system. The complications don't stop there, either. Even with a re-routed fuel system, the ECU still thinks the fuel pressure will be constant, so the entire fuel calibration, even off boost, is wrong with the new system.

XS Engineering made it work despite these difficulties--its Celica makes more than 250 hp at the wheels (up about 90 hp from stock) on pump gas with only 7 psi of boost. We still think more precise engine management will get us even more power with superior driveability and reliability. Our plan? Stand-alone engine management, of course.

Of the many engine management systems we could've used, we're using the Electromotive TEC-II for entirely pragamatic reasons. Our own Shiv Pathak is damn good at tuning the TEC. Good enough, we hope, to make big power without blowing up the only Matrix onthe road.

Before our Matrix even arrived, we sent Project Celica to Vishnu Performance, Pathak's new company specializing in TEC-II installation kits, to have an Electomotive TEC-II engine management system test fit. The custom bracketry needed to hold the crank trigger, the injector sizing and fitment, and the design of the spark plug wires (the stock Celica and Matrix use direct coil-on-plug ignition, so there are no wires) was finalized before the Matrix even arrived in the country.

The TEC-II's biggest limitation is the inability to fully control the VVTL-i variable valve timing system. VVTL-i consists of two separate systems: one varying intake cam timing and one switching between low- and high-rpm cams. The TEC-II has only one general purpose output, however, so we're planning to disable the variable intake cam timing. This might not be such a bad thing, as the stock cam timing strategy is not ideal for a turbocharged engine.

Suspension
The Matrix is tall--you don't need an engineer to tell you that--so we're lowering it like crazy. Much like a VW Golf, the Matrix uses MacPherson struts up front and a twist beam with trailing arms in the back. The front struts are almost identical to the Celica's, only slightly longer and with slightly larger bolts holding them to the front hubs.

Despite the fact the rear suspension is an entirely different design from the Celica's, the Matrix rear spring/shock assembly is also a near-perfect match for the Celica's. Again, the shock body is longer, the mounting bolts larger and the spring perch is slightly higher on the shock body to clear the trailing arm. This all means Celica suspension bits almost fit.

Almost isn't close enough. Since we want the Matrix to sit about 2.5 inches lower, handle like a sports car and still haul all our friends, the Progress Group is building a set of coil-overs specifically for the Matrix. Shortened bodies and shafts will allow the extreme lowering we want without losing all our compression travel. Hotchkiss camber plates for a Celica will also go on, so we can get some aggressive, handling-oriented alignment settings.

We're also replacing the comfortable but very flat stock seats with some far more supportive Sparco Torino sport seats. You might not think seats are part of the suspension, but as both a critical handling aid and the last bit of spring and damping between you and the road, we certainly do.

With our aggressive handling goals in mind, we're lucky the Matrix has massive wheel wells to accommodate very large wheels and tires. We've fit 225/40ZR-18 BF Goodrich g-Force KDs and still have room to spare. We saw some impressive grip from these tires in our G-games a month ago, and we expect the same here. So much so that we're setting a goal of 0.95g on the skidpad.

Brakes
For once, the brakes are easy. The Matrix uses rotors and calipers lifted directly from the Celica GT-S. Given the direct crossover, we called Stoptech, expecting to use its 12.9-inch Celica front brake kit. Of course, Stoptech wouldn't have it. Given the greater weight and higher center of gravity, they insisted the front rotors on the Matrix needed to be even bigger.

A Matrix-specific front brake kit is on the way, but meanwhile we're using a four-wheel kit for the Celica. Surprisingly, the four-wheel kit is just for show. Stoptech's Steve Ruiz insists using the stock rear brakes not only saves money and weight, but works better as well. We'll test his assertion with an exhaustive back-to-back test as soon as the Matrix front brake kit is ready.

Stoptech's Celica brake kit uses a 332mm (12.9-inch) rotor with 28mm thickness. The upcoming Matrix kit and the show kit we're using currently both use 332mm (13.0-in) rotors with 32mm thickness. The reason this matters is that the thicker rotor pushes the caliper 4mm closer to the wheel spokes.

Finding a wheel to clear such massive brakes is not trivial, but Stoptech has gone to great lengths to take the guesswork out of wheel fitment. Most brake kits come with vague fitment guidelines like "fits most 17-inch wheels," but Stoptech was actually able to fax us a properly scaled schematic of the thickest part of the rotor and caliper. By cutting this out and placing it inside various wheels, we're able to see exactly which wheels would fit, and which wouldn't.

As if to prove all 18-inch wheels are not created equal, our brake cutout smashed into the back of the spokes on the first wheel we tried, a Volk SE37A. Using the classic TE37 in the same size and offset, however, we found about 4mm of clearance. These brake caliper templates will be available as PDF files from Stoptech's Web site soon.

Next Time
Lots of talk, not a lot of action, you say? Our photos say otherwise. In reality, the engine, suspension and brake upgrades are all happening simultaneously, but since all the parts are being developed on this car, none of them are finalized. In the next few installments, we'll actually install and test the final parts. We have high expectations for our Matrix's performance; let's hope our friends know what to do next.