Last night was ultimately successful, with the usual amount of driving mishaps thrown in. I almost didn’t go due to high temperatures and predicted thunderstorms. The clincher was Motive DVD scheduled to attend to film. The drive down was stupidly hot, I think it was about 36 degrees. No air con really sucks sometimes. The LCD read temperatures in the mid to high 80s for water and oil temp on the motorway.
As soon as we arrived, some thick, dark clouds appeared, along with a gusting breeze. This dropped the temperature dramatically, although it looked like it might rain. Fortunately, the rain never came, and it slowly cooled as the night progressed. The Motive DVD thing seemed to be a non event as far as I could tell. We’ll see what appears on YouTube. It was dry and quiet enough to get 5 runs so glad I attended.
Run 1 was pretty good. A semi decent launch and cleanly through the gears yielded a 13.211 @ 110.15 mph. Temperature was still 30 degrees despite the change, so probably as good as can be expected. Being down 1 mph on my best run last time was a good indicator of the tough conditions.
Run 2 was ruined by bogging down off the line. I ran a 13.556 @ 109.76 mph. A bit frustrating but the night was quieter than the week before and I had only waited 21 minutes between runs.
Before run 3 I added 1 degree of timing in the upper rpm range. I also did this last week but apparently I didn’t burn the changes to the board. The run was ruined by enormous wheel spin. I spun in first and then plenty into second. 13.739 @ 113.00 mph. The 113 mph trap speed was my best yet, especially considering how hot it was. My runs last September were with a track temp of only 13 degrees versus 25 at the coolest last night. The car was definitely performing well once it had traction, but launching was proving to be an issue and I had wasted yet another run.
I decided to let some air out of the rear tyres before run 4. I didn’t have a gauge, so counted seconds to keep each side even. I was then loaned a gauge and found that after my blind guess, the rear pressure was still at 36 psi. I lowered it to 30 psi and waited for my next run.
The launch was my best ever. I guess I was lucky that I didn’t bog down with the extra grip. My 60 ft time was 2.000 seconds, over a tenth better than ever before. I still had a bit of wheel spin into second but the run was pretty smooth overall and I crossed the line in 12.844 @ 114.31 mph. My wife gave me a big smile and thumbs up as I drove back on the return road. Finally the goal was achieved! You can see in the purple trace below that once the clutch is let out, the rpm is horizontal, then builds nicely.You can also see where I briefly lift off the throttle (orange trace) after changing into second to limit wheel spin.
I had been whipping out my phone and snapping the LCD to see the AFR and boost traces after each run. Run 4 is below. Note that the air temperature post turbo is at 0, which means it is above the maximum 150 degrees of the probe. In that case, you can argue the intercooler is doing a superb job to cool the air to 41 degrees. The probe is mounted just near the throttle body and would likely have a slightly inflated reading due to heat soak in the piping. Boost pressure is just over 20 psi, increasing a smidgen in each gear. Air fuel ratios are somewhere around 11.5, with a rich spike after each change that the ECU adds as quick throttle movement enrichment.
With no pressure for run 5, I removed a bit more air from the tyres, then butchered it. The launch was reasonable, with some more wheel spin into second gear. The disaster came when I missed the shift to third, and on second attempt, engaged fifth instead. It was a very relaxed ride to line from that point onward. I still ran a 14.033 @ 103.39 mph. I even outpaced the WRX next to me who ran a 14.107.
I’m done with drag racing for a while but I think the car still has a lot more left. My 12.8 run was still average in places and was completed on a hot night. I’d like to go back with better street tyres on a cool night and run a low 12 second pass. If I tweak the power and weight numbers in a drag racing calculator to match my 114 mph trap speed, it predicts an ET of 11.64. This is an ideal scenario with slick tyres and a perfect launch. Realistically, with a better launch on good semi-slicks, I should still find a heap of time.
Another thing that I will continue to do is look for ways to lighten the car. It’s definitely the cheapest way to improve performance. The side skirts will be removed in the near future, and the front lip will becoming off too. This will clean up the looks of the car and allow me to lower it back down without dipping to illegal levels. To remove the front lip, some work will need to take place to lift the intercooler up and patch up the butchered front bar beneath.