AutoX tips

[Greg Phillips]

[The short version is if your max speed through corner is 55 mph, you would use full cornering grip and not be able to accelerate until you have tracked out and your exit speed would be 55. If you are slower (53) in the beginning and take a late apex approach instead of a single arc you can start accelerating sooner and would have a higher exit speed (57) which will give you an advantage over the entire straight (assuming Type 1). This is the flip side of trail braking into a corner.

and interestingly enough, this makes no mention of horsepower or weight of the car. This is what confuses me about the momentum vs high hp car question. It seems it should not matter if you assume the above to be true. There are no momentum cars. Or every car is a momentum car. You try to enter as fast as you can and exit as fast as you can no matter the car. The way to do that is to late apex.

What am I missing here?

You have to go on to Chapter 3 (The Real World Line) and pages 40-43

Here he discusses the acceleration potential of different cars, Indy vs Formula Vee. The Indy car can give up speed mid-corner and then accelerate fast enough to gain it back and have a faster exit speed, but the FV does not have enough power and can't accelerate enough to gain back the speed it lost and would benefit more from carrying its speed through the corner and exit (momentum). You have to have enough power (and traction) along with distance to overcome the lost momentum (mid-corner speed) and to come out of the corner with a higher exit speed.
The distance part of the equation may be why it is less applicable to tighter and slower autocross speeds.
It takes some time and lots of figures in the book to try and make sense of this issue.

Greg

[pecivil]

Here he discusses the acceleration potential of different cars, Indy vs Formula Vee. The Indy car can give up speed mid-corner and then accelerate fast enough to gain it back and have a faster exit speed, but the FV does not have enough power and can't accelerate enough to gain back the speed it lost and would benefit more from carrying its speed through the corner and exit (momentum). You have to have enough power (and traction) along with distance to overcome the lost momentum (mid-corner speed) and to come out of the corner with a higher exit speed.
The distance part of the equation may be why it is less applicable to tighter and slower autocross speeds.
It takes some time and lots of figures in the book to try and make sense of this issue.

ok this makes it clear. It ties in with what TT said about cars differing ability to get to max. grip under acceleration.
Essentially cars with enough torque to exceed the available grip under acceleration need a different technique during cornering
than cars without the torque to exceed maximum grip under accel.

The difference between the cars is the amount to torque available relative to grip available.

Under trail braking, In the momentum car or high torque car, you try to keep on the edge of the traction circle under braking and turning.
In the momentum car, you turn with a larger radius at a higher speed, in the torque car, you turn with a smaller radius at a lower speed. But with both you try to keep at the edge of the circle regardless of the speed high or low because BOTH cars are capable of getting to the edge of the circle under braking and turning.

[Jad]

This is also why it is good to have numerous different instructors and talk to different people. Each person explains things and approaches things differently and you have to decide what makes sense and works for your style. There is no absolute right way to do things as everything is a give and take. Do you want to go the slow, short path, or the long, fast path - well it depends....

[Niraj]

Wow. What a great discussion! Here I thought I was asking a "stupid" question.

You guys =>

[ttweed]

There is no absolute right way to do things as everything is a give and take. Do you want to go the slow, short path, or the long, fast path - well it depends....

And if you take into account that we are talking about the "ideal line" for a given car in an autox setting, the advice might change in a time trial setting on a big track, where the greater distances involved between corners (longer straights) changes the equation, as Greg pointed out. When you then move to W2W racing conditions, where you are no longer doing just one, two or three laps with a clear track, the "ideal line" may not always even be available, due to other cars vying for the same spot on the track you might want to place your car! Then race craft and passing strategies come into the picture, and you must choose lines based not on what is fastest but on what will help you achieve your immediate goal in whatever situation you find yourself during the race. This may change from lap to lap throughout the race, and may include trying to get around someone in front of you, or keeping someone behind from passing you, both of which may require ignoring the "ideal" line and using different braking points and techniques, different apexes and lines, etc., on each lap, depending on traffic and changing track conditions.

In other words, besides "It depends," you may also get an answer of "It's complicated...."

TT

[Jad]

Gee thanks Tom, just when people were starting to get it, you threw THAT at them

[LUCKY DAVE]

- If beyond all expectations you find yourself in the lead...........GET IN THE WAY!
- Protecting your position often involves taking strange.....and slow....lines. Only do this in the lead or on the last lap.
- Your "secret" fast line already has two riders occupying it.......improvise......
- Don't slow to the speed of the rider in front of you before passing......pass him wherever you are on the track when you catch him........if you slow to his speed it's twice as hard to pass him.
- PASS WITH AUTHORITY! Passing an inch from another rider in the track's fastest/scariest section will make him think twice about trying to pass you back.