SCCA CAM-C Thread

[kz]

Also found out Lund tune has a raised limiter to 8k rpm (since it appeared I was going faster on top of 2nd that I thought I would and looked at data how was that possible. Anyway, clearly lost time in that drag race not having a good idea what to do or try downshifting. Other side's time that was little slower was right there with fastest C and and T cars.
I'm generally glad engine appears to have survived this event so far.

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[strengthrehab]

Yeah my Lund tune is set to 7.9 or 8k.

 

[shogun32]

Also found out Lund tune has a raised limiter to 8k rpm

and apparently they didn't bother to tell you? Does Lund have documentation on the longevity and valvetrain "safety" of such a move? Or are they just playing fast and loose with customer equipment?

 

[kz]

and apparently they didn't bother to tell you? Does Lund have documentation on the longevity and valvetrain "safety" of such a move? Or are they just playing fast and loose with customer equipment?

They've said nothing (I didn't ask but fair point - when I asked yesterday about how safe it is, got asked why didn't I shift at 7500 (just to downshift 3 secs later and upset the car by either botching rev match or not rev matching at all) and I shouldn't be laying on the limiter as "engine damage may occur". Duh.

But - I have a new tune with 7,500 rpm limiter with spark cut in my inbox two hours after I asked for it. It's has been a learning experience. Nonetheless got have a plan for a course that's basically a drag race...

 

[TeeLew]

I find that if I'm every questioning which gear to use for a certain corner, the answer is almost always to be in the taller gear. Sometimes, it's just too boggy to work, but often I find that if I run the lower gear, then I tend to match my corner speed to the engine revs as opposed to the actual speed of the corner. It's difficult to float speed through a corner if you're revving the nuts off the engine in the process, but much easier if you go to a higher gear and lower RPM.

 

[NightmareMoon]

I find that if I'm every questioning which gear to use for a certain corner, the answer is almost always to be in the taller gear. Sometimes, it's just too boggy to work, but often I find that if I run the lower gear, then I tend to match my corner speed to the engine revs as opposed to the actual speed of the corner. It's difficult to float speed through a corner if you're revving the nuts off the engine in the process, but much easier if you go to a higher gear and lower RPM.

my thoughts exactly. People tend to drive just under their rev limiter, even if the element is really like +5 over the rev limiter.

Lucky for me, most autocrossers can't shift / won't shift, even if their lives depended on it.

 

[strengthrehab]

Swapped gears...haven't touched the rev limiter once since. Engine is probably happier.

 

[kz]

I grabbed 3rd today on .490 red light run - after that straight and slalom was a tight sweeper. Getting out of that corner in 3rd was super slow (so staying in 3rd was most definitely not an answer even though going into the finish was again close to top of 2nd). In a hindsight should have tried a downshift but it's always 20/20. Rarely see those kind of speeds. Robert Clark was at 81 mph in a C8 and I'm not sure how many of you were in Bristol but it is real bumpy...

 

[TeeLew]

Swapped gears...haven't touched the rev limiter once since. Engine is probably happier.

Ultimately, this is my path, I just haven't gotten there, but I'm working on it.

My project creep is pretty silly, but it goes something like this:

I'm running a 3.55 gear with a torsen diff. I like the diff, but the gear is too short.

The 3.15 gear is what looks to be the best for my car (remember, Eco, so ~1k+ fewer revs available than the Coyote).

The Torsen diff doesn't fit in the 3.15 gear. The Trac-Lok is the only available LSD.

I don't want to run a stock Trac-Lok, because even if brand new, they burn up almost immediately losing preload and most lock function. I think this is mostly due to the wear of the phenolic friction surfaces.

In an attempt to increase locking and have better wear characteristics, I'm remaking the differential plates using tool steel. The OE plates are made from stampings of what looks like hot-rolled steel. They are 2.5mm (drive) and 2.7mm (floater) thick. I'm using hardened and ground tool steel which is 1.5mm thick. This allows me to install 2 extra plates in each side for additional locking. The tool steel is a hell of a lot harder than the stock stuff, so I don't think wear will be an issue. I'm a little concerned about everything welding itself together. I'll fight that problem if it becomes one. I've got some ideas there.

For pre-load, I'm ditching the 'S' spring and putting bellevilles on either end of the clutch packs.

Will it work? I don't know. I'm a little worried about being able to install the bellevilles. That might be a trick. Will it be a lot better than stock if it does? I think it will, so away I go.

But it's a hell of a lot of work just to change the bloody gear ratio!

 

[SteveW]

Ultimately, this is my path, I just haven't gotten there, but I'm working on it.

snip

But it's a hell of a lot of work just to change the bloody gear ratio!

Have you examined going the other direction with standard diff carrier and lowering the gear ratio (3.73 or 4.10) to put EB 3rd gear speeds in the sweet spot for autox?

I want to say I looked at that when I was torn between EB and GT back in 2015. I can't remember how that looked on paper.

 

[shogun32]

But it's a hell of a lot of work just to change the bloody gear ratio!

the gear and Torsen should fit in the same housing the 3.55 came in, no?

 

[shogun32]

Have you examined going the other direction with standard diff carrier and lowering the gear ratio (3.73 or 4.10)

granted I don't auto-x but my standard EB came with 3.31 and I bought a complete 3.73 pumpkin for the purpose of raising the RPMs in every gear since it was crazy tall, stock. I might regret it in 1st/2nd but it should make 3-5th a bit more sensible at bombing around a circuit...

 

[kz]

Have you examined going the other direction with standard diff carrier and lowering the gear ratio (3.73 or 4.10) to put EB 3rd gear speeds in the sweet spot for autox?

I want to say I looked at that when I was torn between EB and GT back in 2015. I can't remember how that looked on paper.

Steve - I think Steeda tried that (they even posted about it somewhere here) thinking 3rd gear for Ecoboost was the right answer - I am not sure it worked out for them - it could be if you don't ever have to downshift into 2nd.

 

[TeeLew]

Have you examined going the other direction with standard diff carrier and lowering the gear ratio (3.73 or 4.10) to put EB 3rd gear speeds in the sweet spot for autox?

I want to say I looked at that when I was torn between EB and GT back in 2015. I can't remember how that looked on paper.

So the issue isn't the housing. Those are all the same (except some are AL and others are Fe) dimensionally. The issue is the I.D. of the ring gear itself. The 3.15 is a physically smaller gear than the 3.31 and up ratios. The torsen (& OS Giken, etc) are all meant to be used with the 3.31+ ratios.

The 3.15 puts lets 2nd gear run up to 76.5 mph. To get a similar speed out of 3rd gear, I'd have to use a 4.88 rear gear. I spend a lot of time on the freeway. That would put me at 2900 rpm for 75mph, which is a higher RPM than I want to run for hours at a time. The 3.15 is right at 2k rpm on the freeway, which is more along the lines of the RPM range I'd like to cruise.

These numbers are all with the 295/18 Yoke tire.

 

[shogun32]

The issue is the I.D. of the ring gear itself. The 3.15 is a physically smaller gear than the 3.31 and up ratios

ahhh. surely you can have a machinist indicate onto center and re-bore it to size?

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