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SCCA CAM-C Thread

TeeLew

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As far as the DSC is concerned, I'm going to be a dealer and have a business tuning cars(any type) on mag dampers. I have quite a bit of experience working with passive dampers, but my car will be the first I tune electronically. There are some unique things that can be done and it's going to be an interesting learning opportunity.

I probably need to watch how much discuss it. I haven't really read the site regs on the subject.
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TeeLew

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MUCH better at the autocross today. The 950's were a good choice for rate, but the biggest difference was getting the rear lower. It was way more stable, particularly in slalom transitions. The loose nut behind the wheel didn't make quite as many mistakes, either.

P6 of 15 runners in CAM-C.
 

strengthrehab

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Good Job.

As for me, I realized after killing a rear shock mount (again) on the way to the Texas tour (and having to find a replacement and fix it before first runs of the day in heat 1), I was basically riding on my rear bumpstops since going back to stock shock mounts.

I adjusted the length of my rear shocks (Pedders) to allow for 1.75" of travel before hitting bumpstops.

Car now feels a lot better since I essentially dropped rear spring rate from we (@Brian@BMVK and I )think 1600# plus down to the actual 1300#.

I'll see how the car responds to actual compression damping next weekend.
 

TeeLew

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I'm considering a 3.08 R&P for gearing which would allow me to stay in 2nd gear at pretty much any autocross. I have a 3.55 right now, and it's just too short. I don't think a 3.31 is enough of a difference to justify the effort. Has anyone else done something similar? It's not a Mustang option, but it's one on other platforms which use the 8.8 IRS. Are there any immediate red flags which I should be aware?
 

strengthrehab

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3.08 may be too tall? What size tires? I'd be afraid of killing any kind of exit out of low speed elements with a 3.08.
 

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I'm considering a 3.08 R&P for gearing which would allow me to stay in 2nd gear at pretty much any autocross. I have a 3.55 right now, and it's just too short. I don't think a 3.31 is enough of a difference to justify the effort. Has anyone else done something similar? It's not a Mustang option, but it's one on other platforms which use the 8.8 IRS. Are there any immediate red flags which I should be aware?
3.08 won't work with this platform - the 3.15 OEM-sized diff is a one-off and only works with that R&P - the OEM, OSG and other diffs only work with >3.31, due to space available in the diff case combined with the thickness of taller R&Ps.
 

Dana Pants

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Typically it’s preferred to raise redline and adjust tire diameter rather than change gears. If the occasional SCCA event requires 3rd gear, so what. Rev limits for a second here or there is regular and customarily. Almost certainly if you change gears it should be 1 step
 

Brian@BMVK

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I'm considering a 3.08 R&P for gearing which would allow me to stay in 2nd gear at pretty much any autocross. I have a 3.55 right now, and it's just too short. I don't think a 3.31 is enough of a difference to justify the effort. Has anyone else done something similar? It's not a Mustang option, but it's one on other platforms which use the 8.8 IRS. Are there any immediate red flags which I should be aware?
I'd go the opposite with your powertrain...shorter gears and then use the low-end torque you have and stay in 3rd for most of the course.
 

TeeLew

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Well, bollocks! There goes that idea.

I can shift easily enough, but it can get a little busy. I feel like spending the first 2 runs trying to figure out the best up/down places on the course isn't the best use of those runs.

Tires are BS 305/30-19 with 793 rot./mile (unti I have to change). This works out to a max of 65.8 mph, but my engine runs out of steam about 1000 revs below redline, so ~55 mph. The turbo has really good low-rpm grunt and it comes on a little pipey, to the point where putting power down out of slower corners can be a challenge...maybe even moreso than the V8 cars at times, which tend to be a touch soft at lower RPM and have a more linear delivery. I would have no trouble running a somewhat (~10%) taller gear ratio.

I'm sure everyone is aware the 4-cyl is fragile. I really don't want to give it extra revs. Besides the fact that it's not making any power up top, I don't want to scatter the thing for entertainment purposes alone. As it is, I'm on the rev-limiter a couple times a lap and often for what feels like too long. It's not just a touch, I ride it.

The Rival S 1.5 the same size as the BS is 792 rot/mile. Changing to the 315-18 Yokohama takes me to 813 rot/mile, so shorter.

This is a car I drive a lot, so going with a 4.10 or something gear and running 3rd is not really in the cards. I don't want those extra revs on the freeway and I still don't think it would work well in the Miata-tight stuff (although with 18's, it's possible).

Maybe the 3.31 is the best option. It gives me 5 mph and is a relatively easy swap.

Thanks for the feedback, everyone. I appreciate having a bunch of informed people to bounce ideas off.
 

Brian@BMVK

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The Rival S 1.5 the same size as the BS is 792 rot/mile. Changing to the 315-18 Yokohama takes me to 813 rot/mile, so shorter.

This is a car I drive a lot, so going with a 4.10 or something gear and running 3rd is not really in the cards. I don't want those extra revs on the freeway and I still don't think it would work well in the Miata-tight stuff (although with 18's, it's possible).
What about 3.73s and the 315/30R18 yoks? That would be a fairly significant shortening (just about 7.5%). With that shortening and 3rd, you'd have a ~25% increase in top end speed, but I think just as important, you may stay in the meat of the EB torque curve better.

Cruising and driving around town is perfectly acceptable with 3.73s, ESPECIALLY with the MT82 D4 ratios. With ~7500 rpm and 3.73, the 15-17 2nd gear is fine, but I'd like another ~4 mph or so. With the D4 2nd gear and 6500, it's almost exactly the same as what I have (63 mph at 7500 vs. 63 mph at 6500).

Overall, 3.31 is probably the easiest solution though.

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Dana Pants

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No one I know shifts anything unless they know they will be on the limiter for a few seconds including the eco boost owners I know. I recommend you take the same strategy. It doesn’t really matter if the motor is out of wind after 5500 rpm.
 

TeeLew

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Dana, you tend to have a lot of recommendations I choose to ignore.
 

TeeLew

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Honestly, piss off.
 

TeeLew

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Here we go...
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