SCCA CAM-C Thread

[TeeLew]

...That's why, with our current power mods, we were looking to shift into 3rd gear to get more grunt down low.

By running those short tires, it only compounds our problem with 2nd gear the lack of usable power after 5,500 RPM. Bumping to 3.73s, we can shift into 3rd sooner, stay in it longer, AND have more low-end grunt coming out of slower corners that [hopefully] don't require us to downshift back into 2nd. Hope this helps!

At first I read that the shorter tires were hurting you in 3rd gear and that was what confused me. The shorter tires *help* if you're running 3rd gear, which was your point.

Being able to run the taller gear also has the advantage of encouraging you to carry more entry speed, particularly in faster corners like you had at the FIRM. If the engine is buzzing and making all sorts of racket in the shorter gear it's easy to get in the habit of slowing the car to suit the gear as opposed to being on the limit of the tires. The taller gear makes you drive it a little more like a direct drive kart and you don't feel like you're driving with your hair on fire.

My problem is that I'm between 2nd & 3rd gears. 2nd is good in slow corners and 3rd is good in faster ones, but neither is good in the opposite. I think your experiment was a good one for all of us. Now if we could just get a company to cut some R&P's at about a 3.10 ratio for the Super 8.8.

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[Norm Peterson]

Being able to run the taller gear also has the advantage of encouraging you to carry more entry speed, particularly in faster corners like you had at the FIRM. If the engine is buzzing and making all sorts of racket in the shorter gear it's easy to get in the habit of slowing the car to suit the gear as opposed to being on the limit of the tires. The taller gear makes you drive it a little more like a direct drive kart and you don't feel like you're driving with your hair on fire.

I wonder if this means you need to drive the EB more like a 'momentum car' . . .


Norm

 

[shogun32]

I wonder if this means you need to drive the EB more like a 'momentum car' . . .

I would. But I try to drive my car like a motorcycle regardless if it has a V8 up front.

 

[TeeLew]

I wonder if this means you need to drive the EB more like a 'momentum car' . . .

Norm

I've struggled to figure this out. My natural inclination is to chuck it into the corner with a lot of entry speed, but, in general, if I do that, I just over-run the front tires and create understeer. If I take the same approach while get the front loaded enough, then I just sort of drift the car sideways and slow the car into the corner with side slip. In both scenarios, I've created a situation where I have to wait for what seems like forever before I can get the car pointed toward the exit and can actually get to throttle. If I got to throttle while in that side-slip phase, then it's just drifting. I'm sure it makes good pictures, but it also makes slow laps.

To this point, I've split the corners up into 2nd and 3rd gear varieties. The 2nd gear corners I treat as stop-point-go corners. I basically take the same approach as you would in a V8 car. Remember, this thing is actually pretty strong on the bottom end, so it gets out of these types of corners well. The 3rd gear corners, I treat more like a momentum corner. The taller gear takes the edge off the torque enough that I can carry a lot of speed into the corner, but still go to throttle relatively early and aggressively. The honest truth is that I really don't have it figured out, yet. I'm still experimenting.

Another thing to factor in is that my car is different every time out. To this point, I've been trying to find rear grip/traction as opposed to steady-state balance, so my chassis tuning is pointing me more in the point & squirt direction. Again, I don't know if this is correct, but it's the logical direction based on my balance reads (which are suspect). My rear spring and rear ARB is _way_ softer than what others around here are running, but I run on a dirty, sandy, bumpy, back-lot which has a cheese-grater surface that never picks up rubber. So I'm sure this is influencing my approach to some extent.

 

[TeeLew]

So here's a question for you all that I've been considering for a while.

Has anyone tried the Ford Performance ABS controller? https://performanceparts.ford.com/part/M-2353-D

I have seen (very good) ABS systems tuned for street car applications which severely limit the driver on track. In these situations, the ABS is tuned to assume you're crashing any time you're near the handling limits. Because it assumes you're crashing, it wants you to crash in a straight line to make sure the air bags are effective as possible. If you overcook the entry of a corner just a bit and need to drag the brakes to scrub a little excess speed, it tries to keep the rear wheels at the same rotational speed (even though they're on different radius paths). This means applying a lot of brake pressure to the outside rear wheel and not so much to the inside rear. Doing this produces an understeering moment on the car which makes the whole thing want to go straight.

At the exact time you're trying to keep the weight forward in the car to make the front turn, the brake system is telling the car to go straight. I've found myself in these situations tapping the brake multiple times. Each tap shifts weight forward, but makes an artificial understeer. Each release of the brake allows the car to turn just a touch. If you tap, tap, tap, then you might be able to get the car to turn. If you touch and hold, good luck...it's not going to turn.

Maybe I'm blaming something I shouldn't, but this is what I'm feeling. Does anyone else feel the same or has anyone else tried the alternate ABS box to evaluate the differences?

 

[Brian@BMVK]

I've struggled to figure this out. My natural inclination is to chuck it into the corner with a lot of entry speed, but, in general, if I do that, I just over-run the front tires and create understeer. If I take the same approach while get the front loaded enough, then I just sort of drift the car sideways and slow the car into the corner with side slip. In both scenarios, I've created a situation where I have to wait for what seems like forever before I can get the car pointed toward the exit and can actually get to throttle. If I got to throttle while in that side-slip phase, then it's just drifting. I'm sure it makes good pictures, but it also makes slow laps.

To this point, I've split the corners up into 2nd and 3rd gear varieties. The 2nd gear corners I treat as stop-point-go corners. I basically take the same approach as you would in a V8 car. Remember, this thing is actually pretty strong on the bottom end, so it gets out of these types of corners well. The 3rd gear corners, I treat more like a momentum corner. The taller gear takes the edge off the torque enough that I can carry a lot of speed into the corner, but still go to throttle relatively early and aggressively. The honest truth is that I really don't have it figured out, yet. I'm still experimenting.

Another thing to factor in is that my car is different every time out. To this point, I've been trying to find rear grip/traction as opposed to steady-state balance, so my chassis tuning is pointing me more in the point & squirt direction. Again, I don't know if this is correct, but it's the logical direction based on my balance reads (which are suspect). My rear spring and rear ARB is _way_ softer than what others around here are running, but I run on a dirty, sandy, bumpy, back-lot which has a cheese-grater surface that never picks up rubber. So I'm sure this is influencing my approach to some extent.

This hurts a lot from experience. At some point you just need to drive the car that you know.

The other aspect is that if you go too soft on rear spring, you in effect get roll steer as the camber and toe changes significantly while also slowly loading the tire. I personally would not go below 1000# rears even with a bumpier surface. 1200-1400 seems to be the sweet spot for 200tw tires and an appropriately stiff front spring to match. 1000-1100 with your current setup is probably about right.

What is your rear alignment setup?

 

[shogun32]

touch and hold also keeps the weight on the tire and exceeds grip. By releasing you let the carcass recover and restore grip. though the ABS logic is an interesting possibility.

 

[NightmareMoon]

I used to have trouble with understeer on corner entry, but I think my technique has evolved because its just not a problem anymore (GT not an Ecoboost). I'd love to try that FP ABS controller, but I guess what I'm saying is don't trip the ABS as much and it won't be a big problem?

Maybe brake a bit earlier/softer and don't try so hard to extract every last hundredth of a second in the braking or corner entry zones. Its not worth it if it causes you to understeer and push wide instead of tracking down to a tight apex. IMHO there's a way to throw the weight forward and release the brake which allows the front end to grip and stick and not slide, but car setup is definitely a factor. My S550 GT drives very differently in slow corners from my friend's CAMC S550 GT.

 

[strengthrehab]

Perfect trailbraking takes time to learn. My last event, I was able to get the car to rotate under braking very easily with my trailbraking technique. I brake a little earlier than some and that allows me to come off the brakes and rotate the car while keeping grip on the front. I'm then able to ease onto the throttle at the appropriate point.

These pigs need to be very slow (almost feels like too slow) in the slow stuff for sure.

 

[TeeLew]

I used to have trouble with understeer on corner entry, but I think my technique has evolved because its just not a problem anymore (GT not an Ecoboost). I'd love to try that FP ABS controller, but I guess what I'm saying is don't trip the ABS as much and it won't be a big problem?

Maybe brake a bit earlier/softer and don't try so hard to extract every last hundredth of a second in the braking or corner entry zones. Its not worth it if it causes you to understeer and push wide instead of tracking down to a tight apex. IMHO there's a way to throw the weight forward and release the brake which allows the front end to grip and stick and not slide, but car setup is definitely a factor. My S550 GT drives very differently in slow corners from my friend's CAMC S550 GT.

Braking sooner and releasing earlier is the approach I've adopted, but I don't feel as if I'm driving the car correctly. I feel as if I should be able to trail the brake about 30% of the way into the corner, which would delay my application point somewhat. As it is, I feel I'm overslowing my turn-in speed because I'm releasing the brake as I turn in. That's unusual for any front engine GT car. My car is less nose-heavy than a GT, but it's still nose heavy enough that it needs some help to turn, especially since I'm tuning the chassis to keep the rear under me (my preference).

The ABS is active all the time; it's not just about eliminating lock-ups. It's controlling bias and moving pressures around even when we're just going to the grocery store. In limit conditions, I think it has a pronounced effect, but on this point, my thoughts are really just conjecture. I'll be logging all 4 wheelspeeds next time out and get a better idea of what's going on.

This hurts a lot from experience. At some point you just need to drive the car that you know.

The other aspect is that if you go too soft on rear spring, you in effect get roll steer as the camber and toe changes significantly while also slowly loading the tire. I personally would not go below 1000# rears even with a bumpier surface. 1200-1400 seems to be the sweet spot for 200tw tires and an appropriately stiff front spring to match. 1000-1100 with your current setup is probably about right.

What is your rear alignment setup?

The ever evolving car process is slowing. Recent work has been more on the engine. I didn't just take my car to a shop and tell them to do X, Y & Z. I've done it all solo in my driveway and that has taken about a year to get it where I have.

I may very well be off-base with my spring choice. Time will tell. What I will share is that I've found in the past competitors running the same car will end up with wildly different setups on the same car and be running side-by-side on the time sheet. It's interesting to talk to old rivals over a beer to see what they were doing 'back then'.

I run the rear with camber at -2.0* and rear toe at 2.5mm in per side on a 19" rim, so whatever that works out to in degrees. Rear spring is 850#/in and the rear bar is 20mm. The last time out was on a 950# rear spring and was lacking rear grip. I haven't gotten a good ride height measure on the new rear spring, yet, but it's somewhat lower than stock.

While you were gone, I tested a spring rubber in the front spring (raises rate and ride height). I'm guessing my front rate is about 275 #/in. It was a time gain straight away and felt significantly better. I need go further down this path. FWIW, I do not think it hurt ride at all.

touch and hold also keeps the weight on the tire and exceeds grip. By releasing you let the carcass recover and restore grip. though the ABS logic is an interesting possibility.

Ya, I do get that, but I really feel there's something else going on. What's happening doesn't feel organic.

 

[Brian@BMVK]

While you were gone, I tested a spring rubber in the front spring (raises rate and ride height). I'm guessing my front rate is about 275 #/in. It was a time gain straight away and felt significantly better. I need go further down this path. FWIW, I do not think it hurt ride at all.

I saw that. My guess is you probably increased it to more than 300# if you can feel that big of a difference. Only one way to find out though. The move from 240# front to 300# was noticeable but not huge. The move from 300# to 475# was a very significant change in front-end response and grip (the same improvements you felt).

 

[shogun32]

and rear toe at 2.5mm in per side on a 19" rim, so whatever that works out to in degrees

0.6deg each side. Seems like a lot?

 

[NightmareMoon]

Toe in on the rear causes some under-rotation at the limit, which is often nice when you're putting power down on corner exit, but IDK what it will do if you have a lot of toe in during the mid-corner phase.

Toe out on the front causes under-rotation as well (after initial turnin), which people tend to forget. The classic advice is front toe out to increase turn in, but its the opposite after the initial turnin. I guess it might vary by the corner radius, that would be some fun math to work out.

 

[Brian@BMVK]

0.6deg each side. Seems like a lot?

How so? I get 0.21 deg per side, which is also a lot, but not crazy.

 

[shogun32]

How so? I get 0.21 deg per side, which is also a lot, but not crazy.

Sin^-1(2.5/19*25.4/2) no?

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