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Track Testing

Feb 20, 2003 SHARE
0303_17zoom+1995_bmw_m3_coupe+front_left Photo 1/3   |   Doing laps at the Driving Concepts event.

The last time I took Project M3 to Willow Springs was over a year ago. This was during a small window of time when the car had a fat rear Eibach anti-roll bar and, due to intercooler piping clearance issues at the time, nothing in the front, giving the car an obscene amount of oversteer. This time things were better.

Since then I'd also attended another driving school offered by Driving Concepts, which offers driving schools for all levels--racing and competition and even a teenage car-control clinic. During the summer, Driving Concepts also takes a group on a European dream vacation, racetrack-hopping through several countries. Log on to its Web site for its 2003 schedule.

0303ec_projm3_15zoom Photo 2/3   |   Pirelli P Zero C competition tires, size 245/35-18, were mounted on Forgeline WC3 track wheels for the Euro Tunerfest event. Notice how the outside of the tread resembles a slick tire. By the end of the day the car was turning in consecutive 1:34 lap times without pushing it or the tires to the limits, running over 70 hp under its safe maximum power output. This was good enough for a first-place time-trial finish. The tires also showed excellent resistance to wear and should be good for several track days, as rotating them is possible.

I've always enjoyed Driving Concepts events--they're first class and the instruction is top-notch. This particular event was during the week, which maximized track time. As a matter of fact, by early afternoon I was so tired I called it quits after 2 1/2 hours of track time, even though there still were a couple more sessions to go. (I was glad to be quitting while I and the car were still in one piece.)

To be honest, driving Project M3 around the "big track" is more scary than it is fun. Even with the rear wing, front-straight speeds were exceeding 140 mph, and the car hit 130 mph entering turn 8. Keep in mind this is only at 11 psi, and the turbo is good for over 16 psi. But everything seemed to hold up. The brakes performed flawlessly with the same pads I use on the street, and the suspension felt really tight. Since I didn't have the oil cooler installed for the event, oil temperature was still a concern. But as long as I didn't push the car for more than three hard laps at a time, the oil temperature stayed within reason, under 250*F.

Fortunately, with the stock radiator water temp was not an issue that day. The engine also didn't reveal any signs of detonation and pulled cleanly all day. I used Sunoco 112 octane fuel with an actual "motor" octane of 110. Compare that to Sunoco's GT 104-octane fuel, which is 99, and you've got a difference of 11 points, not 8, as you would expect.

0303_16zoom+1995_bmw_m3_coupe+front Photo 3/3   |   Track Testing

The reason behind Sunoco 112's octane rating is the lead content. As Project M3 had its catalytic converter swapped for a racing exhaust just prior to the event, the only component suffering a little was the oxygen sensor. Down's Commercial Fueling, which supplied the gas, also offers Sunoco 104 octane, which is an oxygenated, unleaded gasoline for cars and motorcycles. (For a comparison of Sunoco 104 vs. pump 91 octane, check out Part 9, 05/02.)

The primary reason I was at this Driving Concepts event was to get reacquainted with Willow Springs and make sure everything was working well. Just 10 days later the car would run at the 2002 Euro Tunerfest GT time-trials.

For Euro Tunerfest I needed a wider set of tires. The Forgeline WC3 track wheels I had were 8.5-in. wide for a specific reason--there's a company that makes R-compound tires in the rare 18-in. size I needed to fit the car perfectly and stay close to the overall diameter of the stock tire. Thus, Pirelli P-Zero C competition tires, size 245/35-18, went on all four corners.

The first couple of sessions were used to adjust the Ground Control camber adjustment to maximize tire contact patch and tire life. By using the infrared pyrometer from Griot's Garage, I monitored tire temperatures to achieve even distribution of contact pressure. To do this, I pointed the pyrometer at the tire grooves after a hot run, taking three different readings--from the outside, the middle and the inside of each tire. According to Pirelli's Douglas Matthews, maintaining no more than a 20*F difference between the outside and inside is optimal. This led me to about 2.8 degrees negative camber left front and 1.8 degrees negative camber right front. Thankfully, it seemed I didn't need to change the rear camber with the BMP Design adjustable control arms at all. I also tried to keep all four tires between 38 and 40 psi hot.

Once the tires heated up, the grip was intoxicating. Braking power felt stronger now that I wasn't getting into the ABS, and speeds through turn 2's sweeper were over 9 mph faster than when I was first here with the car on hard Pirelli P7000 Supersport street tires (01/02). Even so, I'm convinced these P Zero C tires weren't pushed to the limit.

This new grip, in turn, caused me to bring the car into the pits any time I got down to three-quarters of a tank of gas because of hesitations from fuel starvation around turn 2. Add to that the fact the car was burning up fuel at a rate of 4 to 6 mpg, due in part to the six 47-lb/hr hoses firing fuel into the combustion chambers, and you've got a car that would have to pit at least once in an eight-lap race! So much for club racing Project M3--I'll just have to stick with two- to five-lap time trials for now.

Thanks to Big O Tires in Colton, Calif., for mounting the Pirelli P Zero Cs onto the Forgeline WC3 wheels. --PM

Sources
Forgeline Wheels
(888) 643-6051
www.forgeline.com

Big O Tires
(909) 824-9395

Downs Commercial Fueling Inc.
(888) 810-3835
www.downs4fuel.com

Driving Concepts Int'l.
(949) 489-0500
www.drivingconcepts.com

Pirelli
www.us.pirelli.com

Sunoco Performance Products
(800) RACE GAS (722-3427)
www.racegas.com

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