A fellow GTS2 competitor messaged me the weekend before our end-of-summer race weekend at VIR. “Hey man, how would you feel pulling your restrictor plate and running ST4?” Looking at attendance numbers, GTS2 was only going to have three or four of us instead of the usual 6+, and ST4 had another two registered. Our E36 BMWs fit well enough into Super Touring, and thus, the decision was made to change classing for the sake of contingency winnings, as most companies require five or more “starters” to pay out any sort of prizes to the top finishers. Another competitor bumped his car up from ST5 to ST4, which meant we had a total of seven starters for the races.
I towed down to VIR on Friday afternoon, stopping halfway to meet my friend Ryan at our typical Wawa rendezvous. With one iced coffee in the cupholder and the adaptive cruise of my F-150 set to 65, we caravanned the rest of the way to Virginia International Raceway. Our arrival saw us waiting for the gates to open (a different group had the track rented through 6 PM), so we enjoyed some “Miller Lattes” with a few other friends in line.
Once we had paddocked and unloaded our cars, I set about transforming my BMW from “GTS2 mode” to “ST4 mode.” Thankfully, there wasn’t much to do. GTS2 requires our cars to weigh 14.5 pounds per horsepower. Most of our cars started life as M3s, and make enough power that we’d have to be very heavy in race trim. The solution is a “restrictor plate,” which goes between the throttle body and intake manifold to limit how much air gets fed to the engine, in turn reducing its power output. No matter the power output, most of us still end up running some steel plates or weights throughout the car to add a hundred pounds or so.
ST4’s target ratio is just 12.1 pounds per horsepower. The first step in transforming the car is to remove the restrictor plate. Four bolts allow the throttle body to pop off, and the plate slides off. Boom, now the car makes about 235-240 wheel horsepower, up from 210-220. Although there is a calculator on the NASA website, basic math made with some assumptions will provide a vague target weight. In my case, I assumed 240 horsepower, which may be optimistic for my particular car. 240*12.1 comes out to 2,904 pounds as a target weight.
When running GTS2, I must be 3140 pounds (with driver) and run about 80 pounds of steel plate in the trunk to help achieve that goal. Moving to ST4 meant I could remove all of that weight. Two bolts later, the steel plates were in my trailer and the car was lighter. If I were to truly compete in ST4, I’d have to continue “gutting” the car to reach the real target weight. As it stood, for this weekend, I was able to come across the scales at 3100 pounds with half a tank of fuel. There is a lot of weight still in the car that can be pulled, for sure.
Saturday’s practice and qualifying saw all of us pick up some time compared to our GTS2 “bests.” I started running consistent 2:11 laps, which were about a second or so faster than before. My friend DJ helped work on my new suspension setup, adjusting the rebound of the MCS shock absorbers to help with overall grip. We also removed an end link on the rear sway bar, effectively disconnecting it from the car. This helped the car put power down to both rear wheels when exiting tighter turns.
Saturday’s 25-minute race started off well, but unfortunately ended behind a pace car. Someone in a different class spun their Porsche in the flat esses, impacting a tire wall. While the driver was okay, the cleanup required was substantial enough that it was safer to end our race early. So, we were checkered under yellow. I finished Saturday’s race in fourth place.
Sunday’s race was longer, at 40 minutes, and was amazingly a green-flag race the entire session! I struggled to get by an out-of-class racer in the first two laps, and by the time I did pass him, my competition was a bit too far ahead to truly catch. Working through traffic is a goal of mine for October’s “rematch” back at VIR. Regardless, I kept my nose clean and turned some consistent laps, ultimately finishing fourth again. Two competitors were disqualified for coming in underweight at the end of the race, which moved my overall finish up to second.
We lucked out – massively – with the weather this weekend. VIR in August is traditionally very hot and very humid, and every event there this year has involved rain or snow. The track stayed dry all weekend, with very tolerable temperatures and only mild humidity. It was a really pleasant surprise and lent itself to some new track records. Matt, in ST4, laid down an incredibly fast 2:01.9! His car is the most “ST4-ready” of all of ours, as he actually raced in ST4 in the past, with other NASA regions. The rest of us, coming from GTS2, could stand to lose a few hundred pounds.
I suspect we will all go back to GTS2 for the October event, but the extra speed and more nimble handling of a lighter car was a new kind of fun. I am curious to see what the group will decide to do for 2019, given the cars can fit in either class relatively well.
Looking ahead to October, I’ll be more comfortable with my MCS suspension and continue pushing. Some 2:10 (or less) laps should be possible with relative ease, and more aggression on the starts will hopefully keep me even closer to the pointy end of the field. Looking at data has shown which sections of the track are my strengths and weaknesses, and the answer to most of the weaknesses is simply “brake later.”
October at VIR is always a favorite event of mine, so while I am eagerly anticipating celebrating several birthdays, moving to a new apartment, a work retreat, two good friends’ wedding, and a week at the beach, I’m also already pumped for NASA’s return to “Heaven on Earth” with some crisp fall air and lots of fast cars.