Monday, August 18, 2014

Mission Report: TnT 3 and the Tri-Pod Challenge

With the diff in the car and the test miles on, the day I'd been looking forward too had finally come: the TnT.

I actually wasn't the first person to take it out with the new diff. It was actually Steve M, who had driven the car a few weeks prior at MOWOG 4. Steve started the day on a down note when his FMod car wouldn't move under it's own power so I offered him a drive to make sure it wasn't a wasted day.

He came back with a grin. "it's better. But.. weird" To sum up his description, it now has everywhere oversteer. Lift off? yup. On power? yup. Off power? yup. It'll pretty much rotate everywhere. Hmm.. sounds tricky.

I took it out myself, and agreed. it does want to oversteer just about everywhere. It's fun, but definitely a handful. I found if you drive it on throttle or on brakes.. as little costing as possible it's fairly controllable.

A few other people took it for some runs, and all came back with a smile. Even with the handling difficulties, it's a crazy fun car to drive.

Then, just this last weekend is Milwaukee's not-at-all-famous Tri-Pod challenge. A two day event at Miller park, a gorgeous site with surface conditions very similar to Lincoln and higher speed elements than we generally see in MN.

Miller Park

A few runs in and it was clear, the car was too loose now to effectively put power down. The sentiment of a few was that the rake in the suspension setup may be leading to the instabilities of the rear. We'd discussed lowering the car, but being I'd have to put about 350 miles on it getting back home to Minneapolis, I didn't want to risk getting the settings wrong and destroying what's left of the Z2s, tires that are not at all obtainable anymore.

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So after day one, I was emailing Jeff about available shop time this week. It's time to revise things again and fingers crossed that I don't make it worse with only one event and no adjustment time left before nats.

One interesting thing Mike brought up co-driving the car was that he kept hitting the rev limiter. Huh? this thing is geared so it shouldn't be possible on this site or just about any autox site out there. Looking at the data logs it was easily confirmed he definitely wasn't getting to the 67mph top speed of the car.. but I had a suspicion.

Neal on his last run at the TnT mentioned that he thought the clutch was slipping. The ol' 6th gear pull still held strong so I thought it was just a restrictor pill slowing the clutch out causing some slippage. After both complaints, I ran another test.

Heading home from Milwaukee, I found a good straight on ramp and laid into it. Damn. it is hitting the rev limiter around 60mph. I found a similar on ramp after a dinner stop, and decided this time I was going to feather it more. it got to 65 before hitting the rev limiter. The clutch is definitely slipping. Not enough that it won't hold the power in the lower RPMs, but when it hit's it's power peak it just lets go.

There's no time to even think about swapping it before nats, so I'll just have to settle this year with being at roughly the same output and top speed as the DE guys with a weight penalty. Chock another one onto the "winter projects" list. Damn.