SCCA CAM-C Thread

[Dana Pants]

take aways from this weekend’s autocross: 1) it’s easy to hang yourself with rear aero. 2) with sufficient use, the passenger armrest will break into pieces.

verus wing at 12 AoA made the car miserable to drive, even in the rain. So much understeer. From the setup I liked without wing, I only changed the rear bar from soft to stiff. Next event I will try less AoA and a softer front bar.

aero was the cause and solution of every problem in this video:

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[NightmareMoon]

well at least you can feel it. When I tried my wing at it's maximum AoA, I didn't notice massive understeer that I would have expected. Just seemed maybe draggier.

I spend Saturday doing demo autocross runs for passengers at a Shelby American event. My car is still down so they loaned me a Mach 1 on Sport Cup 2s to take passengers in. Probably did 20 runs total with very little wait in between.

I also got a couple tries in a Shelby Cobra replica w/ supercharger. 400hp, like 2000 lbs. Manual brakes, manual steering. The heavy steering and awkwardly thin historical steering wheel make it kind of dangerous to try to recover from anything dramatic, and I smashed the gas trying to stomp the brakes and briefly considered my life as the brick wall straight ahead approached quickly, but I managed to sorted it out before we got too close.

 

[WItoTX]

well at least you can feel it. When I tried my wing at it's maximum AoA, I didn't notice massive understeer that I would have expected. Just seemed maybe draggier.

I spend Saturday doing demo autocross runs for passengers at a Shelby American event. My car is still down so they loaned me a Mach 1 on Sport Cup 2s to take passengers in. Probably did 20 runs total with very little wait in between.

I also got a couple tries in a Shelby Cobra replica w/ supercharger. 400hp, like 2000 lbs. Manual brakes, manual steering. The heavy steering and awkwardly thin historical steering wheel make it kind of dangerous to try to recover from anything dramatic, and I smashed the gas trying to stomp the brakes and briefly considered my life as the brick wall straight ahead approached quickly, but I managed to sorted it out before we got too close.

I was at ECR this weekend. Tires were getting greasy, but instructor and I were feeling brave. On the back stretch, I was at 130, braked at 200', and that was too much. I do recall, as I was sliding sideways around 80 mph, thinking "well this sucks"...but was able to wrangle the car in before I hit grass. After that, instructor and I decided to work on trail braking

Interestingly, I ran my AutoX tune on suspension set up, and it was lights out phenomenal. My instructor, who had a 350, an R, and a 500, said my suspension was the best set up he's ever driven in the S550 platform. So....thanks for the advice from so many on this thread!

 

[kz]

I spend Saturday doing demo autocross runs for passengers at a Shelby American event. My car is still down so they loaned me a Mach 1 on Sport Cup 2s to take passengers in. Probably did 20 runs total with very little wait in between.

How did you like Mach1 compared to your car ?

 

[Dana Pants]

well at least you can feel it. When I tried my wing at it's maximum AoA, I didn't notice massive understeer that I would have expected. Just seemed maybe draggier.

the local nerds convinced me that max AoA will stall a wing and make it useless. So I chose like 3/4 of the range.
And your Saturday sounds awesome.

 

[NightmareMoon]

the local nerds convinced me that max AoA will stall a wing and make it useless. So I chose like 3/4 of the range.
And your Saturday sounds awesome.

I did a test on my dual element Zebulon wing at the max AoA to see if it would stall. At 100mph It didn't. strings stayed attached. Waste of an evening

 

[NightmareMoon]

How did you like Mach1 compared to your car ?

Tall gearing is tall. I had to remember to shift out of 1st or I'd be 30% the way through the course before I hit the limiter. Tall gearing is also a little tall for powering out of slow corners, but it was ok.

It was a handling pack car with magnaride (of course). I drove the car in Sport or Track Mode but with the nannies turned off. I also drove another non-handling pack Mach1 for a couple runs.

It did pretty well overall, but despite the owner saying it had the maximum camber for the factory plates, they were not maxed out in the stock tower holes, and it clearly needed more front camber. Once the Cup 2s were hot, it was pretty easy to overdrive the fronts and understeer with all sorts of fuss and chatter. Anyway, definitely had terminal understeer in the 180° sections if you pushed too far. If you dialed it back and didn't overdrive it like a goon, it didn't feel unbalanced. That part was unsatisfying. I wanted more front authority.

Even in track mode the fancy electronic shocks couldn't control the body in awkward tight/fast transitional moments. My CAMC car has a lot more spring. If you're very smooth it would be fine, but if you had to chuck it around because of the course design, well, half the time it was ok, but sometimes it would get unsettled. That shouldn't be a shock to anyone (pun intended). In smoother sections it did nicely.

So pretty respectable for a pair of stock mustangs, and they were a pleasure to drive. I'll stick with my chassis/mods for CAMC though.

 

[CobaltFilly]

Tall gearing is tall. I had to remember to shift out of 1st or I'd be 30% the way through the course before I hit the limiter. Tall gearing is also a little tall for powering out of slow corners, but it was ok.

It was a handling pack car with magnaride (of course). I drove the car in Sport or Track Mode but with the nannies turned off. I also drove another non-handling pack Mach1 for a couple runs.

It did pretty well overall, but despite the owner saying it had the maximum camber for the factory plates, they were not maxed out in the stock tower holes, and it clearly needed more front camber. Once the Cup 2s were hot, it was pretty easy to overdrive the fronts and understeer with all sorts of fuss and chatter. Anyway, definitely had terminal understeer in the 180° sections if you pushed too far. If you dialed it back and didn't overdrive it like a goon, it didn't feel unbalanced. That part was unsatisfying. I wanted more front authority.

Even in track mode the fancy electronic shocks couldn't control the body in awkward tight/fast transitional moments. My CAMC car has a lot more spring. If you're very smooth it would be fine, but if you had to chuck it around because of the course design, well, half the time it was ok, but sometimes it would get unsettled. That shouldn't be a shock to anyone (pun intended). In smoother sections it did nicely.

So pretty respectable for a pair of stock mustangs, and they were a pleasure to drive. I'll stick with my chassis/mods for CAMC though.

Question on gearing. 3.15 is proobably optimal for track yes? (I already know how amazing it holds 70mph in 2nd on the autox hehe)

In other words, what is optimal gearing for track: taller or shorter gears?

 

[NightmareMoon]

Question on gearing. 3.15 is proobably optimal for track yes? (I already know how amazing it holds 70mph in 2nd on the autox hehe)

In other words, what is optimal gearing for track: taller or shorter gears?

Depends on the track. Its not the rear diff either, its the RPM limit, transmission ratios in each gear, your torque curve (to a degree) and the rear diff.

You dont care about launching or 1st gear, so you want the gearing to match up with the track’s specific corner (min) and straight (max) speeds so different tracks may want different gearing which gives you different shift points.

So depending on your track and transmission ratios you might want taller or shorter rear gears, it just depends.

Autocross OTOH is more of a known commodity. You want your 2nd gear to be around 65-68 probably. Its very very rare to need to go faster than that and anything taller geared than that is just giving up torque.

 

[shogun32]

Even in track mode the fancy electronic shocks couldn't control the body in awkward tight/fast transitional moments

That's true on *street* driving. For the life of me I don't understand why Ford is so bad at rebound damping. Esp when you have travel position and velocity data in real time. There's just no excuse. GM can do it.

 

[NightmareMoon]

For fun, here's an example of torque by gear, which is the kind of analysis you'd want to do to pick a final drive for a specific track.

What I actually have graphed here are the final wheel torques of some estimated setups (of interest to myself). As far as y'all are concerned, just assume the numbers are made up. Torque is the push force you feel. With torque you can compare different gears and make smart decisions about gearing for your needs.

The short geared cars have an advantage (against similar power curves) right up until they have to shift. After they shift, they're much lower torque due to the new higher selected gear ratio, and the taller geared cars eat their lunch until they too have to shift a few miles per hour later.

(Ignoring the red and purple lines). You can see the green and blue lines, which mostly differ in gear ratios - they're trading positions before and after the shift points. Green shifts later and has an advantage for 5 or so MPH, but blue is shorter geared overall and has a bit of an advantage right after the shift. Blue shits the bed at 160 where it has to shift into overdrive 6th gear to keep going, where green is still in 5th. You'd like to stay out of the tallest gears, but you want the shortest final diff gear ratio that will do that.

[Unrelated to track] Also you can see where my old GT++ setup was ideal for many autocross courses with it's 2nd gear shift point at 64, while my next GT350 based drivetrain would have an edge by staying in 1st longer (to 47) and then again above 55 in 2nd where it's power can shine. If I short shift 1st to second at an autocross, I'll be behind all the way to 55mph

On a track, from 35-55 in 2nd gear (not shown) the GT350 is slower than a GT. Above 55 though and its game on because its taller gear ratios (and high RPM limit) allow it to stay in a lower selected gear for longer with a more torquey shorter gear ratio at the wheels.

 

[mavisky]

well at least you can feel it. When I tried my wing at it's maximum AoA, I didn't notice massive understeer that I would have expected. Just seemed maybe draggier.

My understeer is primarily a cause of me overdriving the car and not the "massive grip from the rear wing". Oversteer is absolutely possible if I invoke it.

the local nerds convinced me that max AoA will stall a wing and make it useless. So I chose like 3/4 of the range.

I always default to test and verify. Many times "the local nerds" have told me data that turns out to be pure bullshit in actuality. I'm sure there are wings out there that will stall out within their range of adjustment. The Verus wing itself only goes to 17 degrees and that's within the range of their published testing data and at Autocross speeds I wouldn't worry about it stalling.

[Unrelated to track] Also you can see where my old GT++ setup was ideal for many autocross courses with it's 2nd gear shift point at 64, while my next GT350 based drivetrain would have an edge by staying in 1st longer (to 47) and then again above 55 in 2nd where it's power can shine. If I short shift 1st to second at an autocross, I'll be behind all the way to 55mph

On a track, from 35-55 in 2nd gear (not shown) the GT350 is slower than a GT. Above 55 though and its game on because its taller gear ratios (and high RPM limit) allow it to stay in a lower selected gear for longer with a more torquey shorter gear ratio at the wheels.

This has been my experience in general. The 350 excels in that 50-70 zone, but the gearing and torque curve isn't exactly optimal for autocross. What it does allow you to do though, is be a bit of a hoon with the throttle input as the torque curve is slower and allows you to get on the throttle early easier as there's just less power available until you get the car pointed straight and then it comes on boil.

 

[kz]

My understeer is primarily a cause of me overdriving the car and not the "massive grip from the rear wing". Oversteer is absolutely possible if I invoke it.

Do you know that by pre/post comparison ? (not questioning it just myself I find it difficult to tell without back to back testing on the same day and it would require some sort of steady state cornering, accelerometer - at least the one in Racecapture doesn't seem to have enough fidelity).
Based on our last local I could tell my car was low on front grip compared to stock FS 1/LE - with quite a bit more tire, so I am trying to figure out the reason.

 

[WItoTX]

A stock 1LE is a little better balanced car, with a 3" longer wheel base. I think that's the bulk of the additional front grip IMO. The 1LE has pretty soft springs too, so weight transfer should be better. And likely less weight ovee the wheels since pushrod vs DOHC.

IIRC, you have the dsc. I'd soften the starting mA on the shock calibration tab. That would get you more weight transfer.

 

[mavisky]

Do you know that by pre/post comparison ? (not questioning it just myself I find it difficult to tell without back to back testing on the same day and it would require some sort of steady state cornering, accelerometer - at least the one in Racecapture doesn't seem to have enough fidelity).
Based on our last local I could tell my car was low on front grip compared to stock FS 1/LE - with quite a bit more tire, so I am trying to figure out the reason.

Having run the car all last year without the wing and adding it this year, that's basically my back to back. Along with running the first event at 10 degrees and the second event at 17 degrees. It's not the most scientific, but I don't feel that at the speeds we are seeing that I'm overpowering the car's aero with this setup. That said, I do also run a massive front splitter to balance that out and if someone was running a smaller front splitter or no front splitter at all, maybe that would change things.

I'd love to do a day's worth of testing, but autocross makes it inherently difficult as surface conditions and tire temps change run to run and of course the course layout and weather change event to event. I'm more focused on getting the suspension dialed in with proper swaybar settings and shock damping than I am a few degrees of aero. For now I'm taking all the aero advantage I can get and setting the suspension up to work around that.

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