997 C2S with higher transient rating than 981 CS...

 

oops!

Not sure how that crept in. Should be fixed now.

 

Yes. The rear-engined cars turn faster (respond to a step-steer input faster) than the mid-engined cars.

Polar moment of inertia about the CG is not the droid we've all be trained convinced to think it is.

See this: https://wordpress.com/post/edfishjr.com/4283

 

True, but going back the other way quickly more tricky. Slaloms definitely trickier with that rearward CG. That's gotta be a knock against transient response with respect to autocross given how slalom or offset gate-heavy most courses are.

 

I'll have to think on that.

 

Not exactly apples to apples with 60s suspension design, but my air cooled 911 slaloms horribly. Tail-wagging-dog, it takes all day for the signal sent from the front rudders to reach the rear of the car.

Summoning corner entry rotation with a lift and then pinning the rear end down with throttle is really fun though. I'd pay money to sit shotgun with Yom driving a GT3 as I bet everything he does to make the car work is so different compared to traditional FR car driving it would be mind blowing.

 

Nah, I think you were right the first time when you put 987.2S in BS. We'll let Burglar fix it.

 

I almost mentioned you in my other post this morning, but then I was like, naaah, he's going to STU, not going to rub it in.

 

Certainly the cars of the last 10-15 years are much better in this regard, but it's definitely still a thing.

 

My friend's 993 with the multi-link rear was always quick to turn but easy to lose control in a slalom due to the yaw pendulum. Now that he has gone to BSP with stiffer springs & sways the car is a total beast and changes direction extremely fast. He still has to be careful of inducing oversteer in a slalom, however.

Thinking out loud:
-Upon turning the steering wheel (most) cars initially rotate about a point behind the rear bumper. The closer the CG is to the rear the less rotational inertia at the very start of any turn, including reversing the turn in a slalom. This is what my TR is based upon.
-As all 4 tires start producing slip angle the point of rotation moves forward. If the point of rotation is near the CG, then the car can rotate faster (and will rotate faster in a spin) due to the overall lower polar moment.
-When you reverse the steering wheel (in a slalom) the first thing that has to happen is to stop the existing rotation about the CG and then the point of rotation moves rearward again. (Followed by moving back forward.) Having a more central CG (mid-engined design) would be advantageous because 1) the total rotational inertia (polar moment) to be reversed is less, and 2) all 4 tires are better used to produce the anti-rotational forces than with either front or rear-engined cars. For a rear-engined car rotating about it's rearward CG more of the work to change the rotational direction falls to the rear tires. Of course, that's one reason the rears are usually much wider.

If I artificially reduce the TR of the 997 from the calculated 104.7 down to 100 the Total Rating for the car drops from 90.95 to 90.17.

 

Just wanted to say a big thanks to Ed for putting this list together (and for your excellent emails)! In the fall I decided to sell the 996 to get off ASP island and into a competitively classed car. Did a lot of hand wringing trying to pick between the M2 vs M2C or even biting the bullet and getting the Supra despite being automatic... This list helped me tip the scales (and save me a decent amount of $$). There's an 18' M2 in the driveway now. Not as exciting or involving as the 996... but there's something to be said for being in a competitive class with a car that's capable of being in the mix.

 

Modern BMW

 

Good luck!

By all accounts you will need to learn to anticipate the need for throttle to overcome turbo lag.

 

In my 1.5L Civic I'm back to WOT at corner entry often, the sweet sweet boost will usually give me torque at about the right time if I do so.

 

Which still seems enough to be reasonably competitive, and yet they're absent from competitive circles.