Scratcher Spins the Rollers (and spun ON the rollers, etc)!
03 March, 2008
Pics courtesy of my iPhone since I forgot my real camera...
With the SCCA Double National less than a week away it was time to make sure I wasn't too far off the tuning mark with Scratcher's motor. I wanted to ensure we had timing where it should be and that the jets in the carb were at least close. While I didn't have a ton of time, I took the morning off and loaded her in the trailer Sunday night for the Monday morning dyno session. It had been gorgeous weather over the weekend and Frank and I got a lot of things done on the car and she is just about ready for her first GT1 race. Already there are 6 GT1s pre-registered and another 3 in GT2. I left the main bodywork off to make loading/unloading/working on easier.
Monday (early...6 am) morning gets here and the temp is a nice 70 degrees and then it went to heck. Winds picked up, clouds rolled in and by 8am as I was pulling out of the neighborhood it was already in the low 60s and falling. Falling like rain. So, of course, it rained. All the way to the dyno shop. Great.
I sat there for a bit and it eased off as a dyno employee showed and and just as it stopped raining I dropped the tailgate and we hurriedly put the car in the shop. I hate cold. All of you who know me know that I hate cold. It was cold. I hated it. Thankfully as I walked out the door I threw on a sweatshirt thinking 'I'll take it off when I warm up'. I never took it off. Hate. Cold. totally. Hate. Cold.
So we get her on the rollers and strapped down and fire her up and get some temp in the engine. The car bucks trying to get the rollers going and then when I lay into the gas to warm up the trans and diff sparks FLY off the rears as the little rocks buried in the slicks get turned into glowing embers shooting back 15'. It was still cold. 59 and still falling. I hate the cold.
Run 1. This was a cruel joke. I laid into the gas and as the tach hit 4500 or so it INSTANTLY hit the limiter before I could do anything. The dyno guy was shaking his head. Spinning the tires on the dyno.
Run 2. See run 1. The dyno plot shows 4XXhp and then the rear tires spin on the rollers again. Tighten straps. Drop rear air psi from 28 down to 22. Slight oil leak, attempted fix.
Run 3. See runs 1. We did find the rev limit pill in the MSD that is labeled '8000' actually cuts out at 5500. It goes on the floorboard. Still slight oil leak, fix again. it holds this time.
Run 4. Snug straps further then immediately see run 1. See the pic below? That's what happens when you spin slicks on a dyno at over 100mph.
Run 5. The dyno guy gets another guy (a big guy, who...presumably has insurance) to STAND on the seatbelt bar just over the rear axle. Actually, as I drop it into first and the car lurches a bit he very quickly kneels down and hangs onto the upper cage bar and peers over my shoulders. I get her into third (third, for me, is 1:1 and fourth is OD) and as the dyno guy pushes the 'record' button, I floor it at about 3000. It smoothly picks up and really wakes up at 4500 and pulls quick and clean to 7500 where I lift and clutch and the dyno guy hits the dyno brake. Clean run. Big power. Rich, with peak AF in the 12s. I'd really like to step down a jet all the way around and retest, but we need to do the timing sweeps first.
Run 6. Reset timing from 34 to 32. Lose a few hp. Guy still standing on harness bar.
Run 7. Reset timing to 30. Lose big hp. Guy is now getting good at hopping off and on the back of the car.
Run 8. Reset to 34. Clean run, big power, nearly identical to 5. Guy just stays on the car at this point as I'm not even shutting the car off to make changes between runs.
Run 9. Reset to 36. Clean run, lose 15hp over 5/8. Guy jumps off car as we shut down after this run. Slight oil leak and t-stat housing leak. No biggie, just a pain.
Run 10. Reset to 34. Clean run, big power, nearly identical to 5/8. Now, the moment she fires up the guy comes over and hops on the back of the car like a pro in one smooth movement. At this point I've also talked to my boss a few times and we are slammed at work. We un-strap, push her in the trailer, I pay my bill and boogie. I'd have loved to play with jets, but maybe next time.