Project Toyota Matrix: Part 3

In our last installment, we did the unlikely. We turbocharged the 11.5:1 2ZZ-GE engine in our Toyota Matrix.

Using XS Engineering hardware to make boost, an Electromotive TEC II to make fuel and sparks, and Vishnu Performance's tuning to tell them when to get there, we created a flexible, very powerful, and ridiculously mean- sounding ballistic minivan. The Matrix was running well, even on California's pathetic 91-octane gas.

In July, we took off for Texas and put the turbo Matrix to the ultimate 2,400-mile durability test. In the cold New Mexico night, with 93-octane gas pulsing through its fuel lines, we enjoyed honest third-gear wheelspin. Life was good.

From Texas the car was picked up by a transport company, trucked to Daytona Beach, Fla., and displayed at some big Spring Break bash loaded with scantily clad drunk college girls, then loaded back in the truck and dragged all the way home. Still sporting a thin layer of Florida beach sand, our favorite little car/truck/van/wagon/hauling appliance looked good back in our garage. The patina of hard use lent some much needed honesty to our former carpet queen. There's something about a show car which actually gets driven that just makes you smile.

So we were grinning when we grabbed the keys, clambered into the Sparco seats, and cranked it over. It wouldn't start. Undeterred, we remembered we had sent the car on its journey with a minor cold start glitch. If you paused for a second with the key in the "on" position before cranking it over, the engine would fire immediately and run fine. If you cranked the key directly from "off" to "start," however, it would often fire for half a second and immediately stall. It would then act as if it was flooded and would be difficult to restart. The problem, we theorized, might have been related to the returnless fuel system building pressure relatively slowly, so it might not be fully pressurized when the engine first cranked to life.

Whatever trickery the stock ECU used to ensure clean starts under these conditions was beyond what the TEC II could do or at least what we could figure out. The Matrix's Florida caretakers had probably run into this problem and flooded it so thoroughly, it still wouldn't start.

Eager to take our long-lost turbo trucklet for a drive, we scrounged up some tools, pulled the spark plugs, cleaned them with a used napkin we found under the driver's seat and the car started immediately.

The idle was a bit rougher than we remembered and the exhaust was so ripe with unburned hydrocarbons, it made our eyes water. Clearly the plugs needed to be cleaned better. Maybe boost would clean them. We hit the highway, carefully dipping into boost just to make sure everything was all right. The Matrix ran great--healthy, smooth and torquey on the low-rpm cam, and really pissed off at 6000 rpm and up. Mix the sounds of a Suzuki Hayabusa, a Group B Turbo Quattro and a UPS truck and you'll get close.

The local riceboys all recognized it. They all wanted to race. They all lost. Life was good again.

Our hearts were filled with turbocharged satisfaction. We were happy. We tried really hard not to notice the fact the idle was getting worse; the exhaust note was slowly changing, getting less like the Hayabusa and more like the UPS truck. Over the next few days it got worse, harder to start, rougher idling, stranger sounding. We considered painting the car brown.

Then we noticed the oil. The intercooler pipe had a big splat of oil on it. The splat was directly across from the blow-off valve's discharge port. The turbo was pumping oil. A blown turbo seal? Already? On a brand-new IHI turbo?

We took it back to XS Engineering where the guys listened to the exhaust and immediately doubted our turbo seal theory. Pulling the oil cap revealed the unfortunate truth. At idle, a thundering hurricane of wind came pumping out the oil filler. Blowby, and lots of it, was pumping oily air out the crankcase vent and into the turbo inlet. That much blowby could mean only one thing and a leakdown test confirmed it. Cylinder #3 had 70 percent leakdown. The Matrix was broken. Our best guess is that something happened in Florida. A bad tank of gas or a few careless gallons of 87 would be enough to cause a few hard pings. Or maybe a bunch of hard pings. Enough to barely crack a ring land, probably. Take that damaged piston for a night on the town and you end up where we were. Done. Being a Japanese-built prototype, The United States Customs Service would only allow our Matrix to stay in the country for 12 months. It had already been 10. Project Matrix was finished.

Before its unceremonious demise, we did get to play with the brakes and suspension. We never got it completely dialed, of course, but we still learned a lot. If you're feeling sketchy on the basic principals of hydraulic brakes, piston sizes, brake torque and all that, go read this month's "Technobabble" on page 16 before reading any further. We're about to use numbers.

For the 2001 SEMA show, the Matrix was equipped with a ridiculously large four-wheel Stoptech brake kit. After doing its time on the carpet, Project Matrix went to Stoptech to test a front-wheel only brake upgrade and compare it to the four-wheel SEMA kit and the stock brakes. The four-wheel kit was great for carpet racing, but according to Stoptech's Steve Ruiz, most cars don't stop as well with a four-wheel kit as they do with a front-wheel upgrade and stock rear brakes. We tagged along during testing, hoping to see this point proven.

The Tests
Stoptech's brake testing is far more intensive than our own, probing not only ultimate stopping power, but fade resistance and brake balance as well. Ruiz asked us not to reveal how it tests brake balance, and since doing so would involve lots of math to explain anyway, we gladly obliged.

Stopping power and fade resistance were tested by simply going fast and then stopping. Over, and over, and over and over. Distances are measured with a Stalker radar gun, just like we use, and front and rear rotor temperatures are recorded on every stop, using an Omega surface pyrometer. Infrared pyrometers can give different readings depending on the surface finish of the object you're measuring. All the ridges and valleys, polished spots, blue areas and even glowing rotors can throw off the reading. A surface pyrometer that actually touches the rotor is far more consistent.

You'll notice each of our stopping distance charts has at least one run where the radar gun malfunctioned. The tests were performed on an active runway and, every now and then, a plane would land in front of the radar gun, throwing off the reading.

The first set of stops is from 60 mph to 0. Since the time needed to turn around, drive past the braking zone, turn around again and accelerate to 60 mph cools the rotors too much to be a useful fade resistance test, a second 60 to 5 deceleration run is performed on the return road just to keep the brakes hot. That braking run is not shown in our data. For some stock systems, a few passes are enough to produce longer stopping distances. If not, the speed is increased to 80 mph and the stop on the return road is no longer performed. If 80 mph still isn't enough, the 100 to 0 runs begin. The number of runs at each speed varies depending on the car and how the results are coming up.

This is not a scientific test, it's an engineering test. A scientific test is searching for hard, repeatable data, but an engineering test is just looking for the solution. If the brakes get too hot, for example, a scientific test would determine exactly how hot, then test the new brakes in the exact same way to measure exactly how much cooler they ran. For an engineering test, the fact they're too hot is enough. Now go make something that isn't so damn hot.

The Brakes
We tested three distinct setups. The stock brakes were perfectly stock, but we kept the 225/40ZR-18 BF Goodrich G-Force KD tires on the car. The brake balance, based on a simple brake torque reaction calculation that doesn't account for pad material, proportioning valves or caliper flex, is approximately 73 percent front, 27 percent rear.

The two-wheel kit used 328mm (12.9-inch) rotors and four-piston calipers up front. To shift some braking effort to the underutilized rear brakes, small, staggered 30 and 34mm pistons are used. For a given pressure, this front brake setup offers only 78 percent of the brake torque reaction of the front. Combined with stiffer calipers and stiffer brake lines, this gives a heavier, firmer brake pedal and a calculated brake balance of 68/32.

The four-wheel kit used for the SEMA show has rear rotors as big as the fronts on the two-wheel kit. The smallest pistons Stoptech can put in its two-piston sliding caliper are staggered 28 and 30mm pistons. This rear brake setup is way too strong, 173 percent as powerful as the stock rear brakes.

To achieve any kind of balance, the fronts have to be quite a bit stronger than those used on the two-wheel kit. Larger 332mm (13.1 inch) rotors are used and the calipers are fitted with larger 42 and 44mm staggered pistons. The resulting brake balance is theoretically 67/33.

But brakes this powerful have a downside. They feel overboosted, touchy and are difficult to modulate. It takes very little fluid pressure to bring the car to a screeching halt, so careful modulation of the brakes coming into a corner means tickling the pedal with a feather. The large volume of fluid needed to move all those large pistons also makes the pedal feel soft and sloppy compared to the two-wheel kit.

The Data
Toyota makes really good brakes. We've seen surprisingly short braking distances on the MR2 Spyder and Celica, and the Matrix continued to impress by showing excellent fade resistance. In eight stops from 60 mph, which, remember, involved 16 stops worth of heat because of the stop on the return road, stopping distances actually dropped from 122 feet to 116 feet. Kicking the speed to 80 mph, the distances stayed short (Stoptech doesn't use the return road stop on 80 mph runs, so the rotor temperature actually drops for the first few runs), and even after four 100 to 0 stops, the brakes were still as effective. The pedal had gotten very spongy, but the brakes were stopping the car just as well. Surprisingly, the stock brake pads survived the 900-degree rotor temperatures.

The two-wheel kit braking distances were surprisingly similar, though the front rotors were running much cooler, 200 degrees cooler by the 15th stop. The rear rotors ran only 10 to 20 degrees warmer than they did with the stock brakes, which shows the effect of the slightly more rearward brake bias and suggests rear caliper flex was not making the best use of the fluid pressure being delivered. Pedal feel stayed consistently firm throughout the test.

The four-wheel kit, which we didn't expect to perform all that well, was brilliant. Initial stopping distances were similar to the first two tests, but 80 to 0 and 100 to 0 distances were shorter. After 22 stops, the front brakes were still cooler than the stock ones had been after 15. The rear brakes were cooler after 22 stops than the stock rears were after 3. The rears ran so cool, in fact, the pads were barely up to their proper operating temperature by the end of the test.

The most likely explanation for the four-wheel kit's superior performance is that the ABS liked it best. The more rigid rear caliper translates the fluctuating brake fluid pressure into fluctuating brake torque more quickly, knocking milliseconds off the ABS's response time every time it pulsed the pedal.

So, in a pedal-mashing frenzy, the four-wheel kit was best, but is that worth the soft, touchy pedal? We didn't think so. With all the data in front of us, we still drove off with the front-wheel only kit on the car. The firm, consistent pedal gave us the control we wanted, and as hard as we could imagine driving the Matrix, we didn't expect to notice the difference in 100 to 0 stopping distance.

Suspension
The Matrix almost shares its front suspension with the Celica. Though most of the parts look interchangeable, the bolts mounting the strut to the upright are larger on the Matrix and the strut itself is longer. Drilling the mounting holes on a Celica strut should make it fit, and the shorter strut would help with the lowered ride height.

Of course, in the rear, things aren't quite as easy. The upper spring and shock mount is the same as a Celica, and the shock design is, again, very similar; but in this case, the larger lower mount is in the middle of a rubber bushing, so you can't drill it out. The spring perch also sits a little higher on the shock body to clear the Matrix's inferior twist beam suspension. No Celica shocks back here. Sorry.

No problem for us, though. We had the only Matrix in town, and Progress wanted to see it. We made a deal. It would make a prototype suspension and then we'd have a suspension. Simple.

While Progress designed a set of coil-overs, we poked around for camber plates. The upper strut mounts are the same as a Celica, so we got a set of Hotchkis camber plates. The Hotchkis plates sit above the strut tower, making the camber plate itself a natural mount for a strut tower brace. Not ones to miss an opportunity, Hotchkis includes a brace with the camber plates.

The Matrix turns out to be slightly wider than the Celica, however, so the strut tower brace doesn't reach. Tell them it's a Matrix when you order the camber plates and Hotchkis should be able to supply you with the right length brace by now. If it did reach, the brace would have been very close to the brake fluid reservoir, possibly even touching it.

Getting any useful camber adjustment out of the Hotchkis plates requires some trimming of the hole in the top of the strut tower, which we were going to do as soon as the car came back from Florida. Oops. Without the trimming, you can get just more than 1 degree of camber--about the same as stock.

We had also planned to test, tweak, and re-test the Progress coil-overs, but again, that's difficult to do with a broken piston. Luckily, we had taken the Matrix to the track once before the Trek to Texas just to see how good Progress' first guess was.

The Matrix has a very simple rear anti-roll bar that bolts into the beam of the twist beam rear suspension, and Progress gave us two replacement bars--one was 7/8 of an inch, the other was 1 inch. On the slalom, we found the Matrix surprisingly tail happy, thanks, no doubt, to its tall hindquarters. With the Matrix's slow steering, staying on top of its wagging tail was a challenge, so we never installed the 1-inch bar. Progress agreed and is now producing the 7/8 bar, which also fits the new Corolla.

Despite the tail chasing, the Matrix was shockingly fast through the slalom, posting 71 mph, a dramatic increase from the 66.7 mph of the stock car.

On the skidpad, the larger bar would have been welcome, but for a more realistic picture of its performance, we left the suspension the same. Punishing its front tires, we managed 0.91 g. Given more front camber, it probably could have pulled a lot more, but again, that piston.