Em updated you on how we finally got our Boise bugs nailed and ran better in Bremerton (but not quite well enough to get a win light…). I thought I’d tell you how we did that. It’s really a testament to what good friends we have, and I love to talk about them.
We had several problems in Boise. The first, and probably easiest to fix was a stumbling problem, where the car would stall after the burnout or even on the launch. Em recounted how embarrassing that was, so I don’t need to reiterate that. However, we fixed that problem by realizing that Boise is at a very high altitude, and that we were probably pushing too much fuel through to match the thinner air.
Bob Johnson, our engine builder, and I had debated on the dyno whether to leave the size 96 jets in the carburetor or to go back to 95 (smaller means less fuel). Since it made just about the same amount of horsepower with either, we decided to stick with the 96s. But Boise seemed to need the 95s. Bob was pitted next to us and helped us figure that out. Less fuel works better with the thin air, so that fixed the stalling problem.
The other problem, however, was much more confusing. The issue was that the car wouldn’t stay “on the stop”. And that requires some explanation.
When we leave the line, the car launches and then immediately goes on the throttle stop. The throttle stop is a device between the carb and the intake, and its job is to slow down the car for just a couple of seconds, then get out of the way. It does two things: it slows a really fast car down to the 8.90 seconds we need to run, and it provides us the ability to tune the car to within the thousandths of a second we need to run in this incredibly competitive class. We run a Dedenbear TS6 stop, and it’s a wonderful, top-of-the-line device — very consistent and very tunable.
The problem we were having in Boise is that the car wouldn’t stay “on the stop”. That is, it would drop to the RPM we had set, but instead of staying there for the duration that we had chosen, the car would continue to accelerate. Fortunately, we have a Racepak data logger on the car and could tell that this was happening. Without the logger, the car would just look very fast, and we wouldn’t known what was happening. In a future post, I’ll show you some output from this wonderful device and walk you through the myriad things it tells us.
The question then became, why? Why would it not stay where we set it? Was the stop broken? We tested it, and it appeared to be working. But working in the pits is not the same as on the track. Maybe something was broken inside the stop? I didn’t know. But with Bremerton just a few days away, I couldn’t take a chance. So I ordered another throttle stop from our friends at Jegs just in case, and had it shipped in by air so I’d have a spare.
But I didn’t think that was it. Something else was going on. As a “hail Mary pass”, I tossed a quick email to our friend Jack Beckman, the consummate professional racer who sold us the car and has been the source of much wisdom. I explained the problem, and pressed “send”. Within 30 seconds, my phone rang. It was Jack. We discussed the problem, and he came up with a half-dozen ideas, from loose intake manifold bolts to a flaky carburetor. Then I casually mentioned that we’d changed the way the car shifted… and all heck broke loose.
You see, after our test session in Seattle, Bob the Builder had suggested that, rather than shifting at a specific time down the track (like 1.2 seconds) we should shift when the car reaches a specific RPM (say 7400). It made complete sense, that’s the way you shift your car by hand – crank it up, shift when the revs get so high, and so on. It’s also the way to get the most horsepower out of the engine, it would be operating in the peak horsepower range longer. The car would go faster because we were running in the engine’s sweet spot, and because we’d be shifting out past the time on the stop, it would be more consistent. So I changed the car to shift on RPM before we got to Boise. (My winter re-wiring job had made this an easy change.)
When I mentioned this to Jack, he went bonkers. Why would I do such a thing? Who suggested it? Has that person won the Super Comp world title, like he had? And so on… But, I said, it seems to make sense. Well, it’s wrong, he said. Why? That’s where it got interesting.
It’s because the car is just too darn powerful, and the changes we made to get more horsepower over the winter had made it even more so. With the car in first gear, the engine is too strong, and just continues to accelerate, even though the throttle stop is restricting the fuel intake. It’s like a wild horse, just striving to be free. The huge engine just needs to run, and if you give it muscle (by leaving it in first gear), run it will. The trick is to shift into second really quickly. He even suggested that, with all our additional horsepower, we should move from last year’s setting of shifting at 1.2 seconds, down to shifting at 1.0 seconds. Our buddy Ed Hauter (the PNSCA president) said that some people who run the really big engines (the 632s and such) don’t even shift, they run in second gear the whole way.
This seemed a little “out there” to me. Why would what gear we’re in change how the throttle worked? But hey, as Jack said, he’s won the world championship, so it was worth a shot. And again, the re-wiring I had done over the winter made the change easy. I even made it so that we could switch back and forth at the track with just a chip change. And off to Bremerton we went.
The change was almost miraculous. From our very first run in Bremerton, the car stayed on the stop just like it was supposed to. Our only problem was that it was still too fast. But that was solved by slowing down on the stop and staying there longer. Soon we were back in the game, and ready to compete in this ultra-competitive class. Thanks, Jack!
Funny thing, the next Monday, my new Drag Racer magazine showed up and there was a tech question to the editor about this same issue. And the answer was just the same. Shift on time, and shift early when running on a throttle stop. Counter-intuitive yes, but it works. Oh, and on that same Monday, I sent back the new throttle stop I ordered, because we clearly didn’t need it.
So thanks to Jack for his help. I even called Jack on Saturday at Bremerton with another small problem, and he always took my call, and dispensed great wisdom. Bob, too, has always been there to help, even when I’m being stupid. Thank you, Bob, for always taking my call, and for not laughing (at least to my face) when I ask a stupid question. It’s friends like you who make racing so rewarding.