build diary

August 1, 2009: Is it bad when you can't even finish two laps of the track without two things going wrong with your car? At the track day today, I had the hood come almost completely free.
Three of the four latches undid themselves, and the hood started to fly once I got over 60 mph or so. Quite eye-opening. Because of this, I aborted my first session in order. When I came into the pits, it became obvious that my quickie repair to the front fender stay (remember that from the Open House last year?) had come undone. Whoops.
So, off came the otherwise-undamaged fender and stay. No problem, it's two bolts. I'll fix that at home. A bit of tape over the latches solved that. So it was back out.

I was back up to speed pretty quickly. Remember, last August I turned a 1:01.893. Well, today I managed a 1:01.960. And if I'm reading the time sheets correctly, I managed to do it twice! Weird. So a year ago, that would have been a new lap record. But it's not a year ago. I was playing with some higher tire pressures and it's possible that improved grip was masking some rustiness on my part.

Bill didn't show up with the turbo Westie, so it wasn't a concern. Brandon, on the other hand, had been building a nice fibreglass airbox for his lightweight beast. Between that and a more aggressive driving style that was apparently modeled after mine (his girlfriend, being used for ballast, called it "terrifying") he was going faster than he'd ever gone. Not quite enough to beat the lap record, but very close. His 1:01.652 is only a tenth behind, and there's still more left in the car.
I got a chance to tuck in behind him on one session after he did a little half-spin. It was very interesting. There certainly isn't much between us. A small mistake in braking into turn 4 and he picked up a car length, but overall it was a close match. Until, while screaming down the back straight, the back of the Seven stepped out. The next braking zone - the hairiest part of the track in any lap - was quite exciting. And it wasn't a one-time thing, it was as if the right rear tire had deflated or got covered in oil. There was just no grip back there. The left rear wasn't feeling so good either.
Since it was the last timed lap, I was on my way in anyhow. I cooled the car and then pitted. Tire pressure was good. I think I simply overheated it. Hard to believe with such a light car, but I do get a fair bit of wheelspin at times. Everyone was complaining about their tires getting greasy.
Unfortunately, I never got a chance to find out if that was the case, as the photographer reported that my car appeared to have thrown a belt. It was still running cool, but a peek underhood revealed that this was true. It had thrown the alternator/water pump belt again! That's the second time, and I'd just tensioned it the day before. The pulley setup is stock Miata, and they don't usually throw belts. They don't usually turn over 8000 rpm regularly either, but still. The car never did it before. An eyeball alignment check showed that the front crank pulley seemed a bit cockeyed. Starting the engine up confirmed it - fairly serious pulley wobble.

Uhoh. If you know Miata engines, you know the 1990-91 models had a crank nose that could break. Has the Seven fallen prey to the dreaded crank nose problem? Or is it something else, like a heavily abused 20-year-old harmonic damper that's failed internally? I don't know yet, but some disassembly will tell. The belt was retrieved undamaged, but I parked the car for the rest of the day. With the belt back on, it drove home happily enough. Even if it is the crankshaft, one of the other Miata drivers at the event happens to have a spare 1992 bottom end at his house. I could probably replace it in an evening. So it's not a big problem overall.

So that's it for a while. Time to do some real work on the car before it comes out of hibernation again.

entry 1436 of 1439
<< | random | >>
back to entry listing