Porsche Club AutoX - Saturday, Aug 30th

AllanJ wrote: Hey Patrick, I know you want to learn so that's why the peanut gallery spoke up.  Kudos to you.

Wow, lots there to take in! Let me come back tonight after I've had a chance to digest it all. Thanks Al.

 

No problem.

This is all general "performance" driving knowledge that
I've been mentioning to Gary over time but it still takes
a while for everything to gel in your head. It took me a
while!

One more example from when I was there last time:

Rich drove the 914 and felt it understeered. He couldn't
get it to turn in without plowing. Gary felt the same
way. I was a bit surprised because I thought the car was
fairly balanced.

So I adjusted the shocks to move the balance a bit so the
front had more grip (and the rear had less grip).

When I drove the car at lunch, the car sucked! It was
oversteering horribly in linked turns. So I undid my
change and put the car back the way it was.

What was going on between me and Rich? Rich asked me how
I got the car to turn in nicely when all he dealt with
was understeer.

I'll go back to my previous post about weight transfer
and grip levels front to rear.

When Rich drives the car, he has a tendency to get all
the braking done in a straight line before the turn, and
then gets off the brakes quite quickly and is back on the
gas. So what's going to happen is he enters the turn
either neutral weight or even rear-weighted. What are the
tires doing? You will have less than desired grip up
front and with a light front end (on a mid-engined car),
you will often get understeer. Not much weight on those
front tires and it's hard to turn.

What do I do? I "trailbrake" into the turn. I'll dive
into a turn, braking fairly late. By the time I'm ready
to begin my turn, I'm still going too fast to make the
turn without sliding, so I need to keep applying the
brakes. Applying the brakes moves the weight to the
front, giving more pressure to the front tires, giving
them more grip. No understeer for me and the car is
rotating just fine! But as I increase the steering input,
I'm taking away from my overall grip levels because the
car needs tire grip to turn. So as I feed in more
steering, I'm REDUCING the brake level.

Simplified summary of tire grip distribution:

Braking in a straight line: 100%
Turning: 0%

Starting turn with 10% steering
90% braking

Getting into turn with 25% steering
75% braking

Mid-turn 50% steering:
50% braking

Max turn angle 100%
0% braking - completely off brakes now because I'm using
all my potential grip to turn

Time to accelerate out of the turn, reverse of the above

Unwind wheel to 90% turn level:
10% gas

Unwind wheel to 50% steering
50% gas

Out of turn at 0% steering input
100% gas

That kind of thing.

For Gary's car, I'd rather it be set up the way I drive
it because I believe (and so does every car manufacturer
that sells cars in countries that have lawyers) an
understeering car is safer. You don't want to make an
emergency maneuver on the highway to avoid some debris
and end up in a spin! Also, if you have to make an
emergency turn to avoid something, chances are you'll
instinctively lift off the throttle or get on the brakes
and then turn the wheel - an understeering car responds
perfectly to this situation.

One other thing: when I first autocrossed my GT3 I was
understeering everywhere because I drove it wrong. I was
overslowing for a turn and then back on the gas at the
start of a turn, when I wanted to rotate the car. It's
very hard to turn a 911 when only 1/3 of the overall
weight is at the front and you are artificially making
that be even less because you're on the gas at turn
entry. So I'd be plowing through cones all the time. Race
like crazy to the next turn - and mow down more cones. It
was brutal. It wasn't until I understood weight transfer
and how it affects grip levels that I finally drove the
car better.

Weight transfer is key. Understand how that works and how
it affects grip levels and you're well on your way.


Edited by AllanJ

ya.. sorry about the noise. I promise I will work on that


Rich was keenly interested in how I was driving and carefully watched what I was doing. when it was his turn, he performed maneuvers with the car I did not seem were do-able. by the end of the day, I had applied some bits here and there. he drove it well.
the mid engine design car (Fieros, etc..), I believe can be set up well but the driver is indeed the biggest variable. we all need to get out there and apply what we know and be observant.

we had old American muscle, all wheel drive, and even an old Volvo there, all swaying to those cones in their own ways. they all were impressive in their own ways. (and if you are still reading this and it does not sound like Bla, Bla, Bla.. then please consider coming to the next event. all these words can be boiled down to some simple things that will help anybody drive more soundly) it is fun stuff!

AllanJ wrote: The other key benefit is that the average speed of autocross is about 60km/h...

...which is why the BCCC autocross a few weeks ago was rather invigorating when we were entering the stop box at 115 km/h!

Al, you've gone over a ton of helpful stuff. Thanks so much.  I often wish there was a way of having a sweeper set up at a track and then just do that one sweeper over and over and over again until it feels just right. The UBCSCC Autocross 101 which I've taken a couple of times sort of does that, but I'd love to find an abandoned parking lot somewhere out the middle of nowhere and just turn up there with a number of cones. I think that's what it'll take for all this information to actually sink in.

Gary commented that Rich seems to plays tricks with his feet while driving the course. He uses his left foot to brake so as to reserve his right foot for GO duty. Is there some value to learning this technique, or is there a danger of over-complicating things?

One thing I haven't mentioned during any of this discussion of my handling issues is the fact that I've never had the wheels properly aligned on my Formula at a shop.  You may now wonder.. "What the heck!" Keep in mind that Colby and I did a rough alignment (to the best of our ability), but the reason why I didn't take it to a shop is that I wanted to finalize my choice of suspension components first. Among other things (ball joints/struts/shocks/zero-lash end links/sway bar poly bushings) I put lowering springs in, which are a heck of a lot better the factory springs, but as I've mentioned previously, I'm not 100% satisfied with them. Call me thifty/cheap/frugal, but I didn't want to be spending $100+ for alignment more times than necessary. Once I decide for sure what I want to stick with, I'll take the car to a shop and have everything set to specs. That just might improve the handling.

Edited by Patrick

I have kept quite in these autocross threads, but thought this to be slightly funny. If you grew up driving in the 60's/70's or just had older cars in the 80s you probably got experience with left foot braking when you came to a stop on a cold day. Fighting to keep that carb'ed car from stalling at stop lights. One foot slightly on the gas and left food modulating the brake as you came to a stop.

      I also read on another autocross group of some of the problems with left foot braking, can be loss of engine vacuum. If your right foot never comes off the gas, especially in turbo cars, (yes even with boost check valves) you may not close the throttle enough for the engine to make enough vacuum to replenish the brake boosters vacuum supply. Then losing your brakes. IIRC a number of years ago there was a woman in a Corvette at the Boundary Bay area lost control of her car and lost braking, either went into the crowd or staging area, I can't completely remember the details.   

So just a few things to think about when it comes to left foot braking.

AllanJ wrote: I do have about 20 cones....

Gary and I will keep our eyes open for a large abandoned paved area.  I'm sure Colby would be delighted to suggest some locations as well, but Saskatchewan is a bit far to go for autocross practice.

 

I was doing it in the Fiero. I LFB in any car that I'm
racing. (no need in street car..)

And the newer cars respond quite well to it - as long as
you're not trying to overlap too much throttle w/ gas. I
LFB in the new corvettes and 911s and it doesn't upset
the computers at all.

Welcome Rich!
as you can see, your run made the best video for quality, although not your fastest run by far, but does show a nice line and driving skill. i enjoyed watching the car go around.

i really had a great time!