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      10-25-2011, 04:07 AM   #1
Merked M3
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!!!! More Advanced Autocross Techniques...



I am looking to start developing some more advanced autocross techniques. After getting my track rims, I am now noticing that "I" am now the part of the car that needs the most improvement. With my new wheel and tire setup I have LOADS of grip, no understeer (used to have too much), and the M3 performs like a monster.

With a 2-month build time on my wheels, I was unable to make the last track day of the year as Laguna doesn't have any events after August. So I have been autocrossing alot since I could use stock tires there (this will be my 2nd full year of autoX). I have dialed in some stuff on the M3 and tried to get the basics down, but I know this car has more.

* I have dialed in cold and hot tire pressures using chalk and constant adjustment. I have even found at what point they are too high, causing premature break away.

* I trail brake for most of the course and understand how this concept works. Still a good amount of room for improvement here though.

* I really try to monitor traction at all times and add as much gas as possible without slipping.

* On course I am looking ahead to plan apex's properly. I even bought a bike rack for the E90 so I get 5x the course-walks than everyone else!

Things I want to try:

* late apexing corners to give me longer straits
* choosing which corners to take wide (big ones) and which to take tight (small corners)
* still need to improve my launch, what RPM range is everyone using?

I was also really wondering what the perfect balance of acceleration and turning would be. I have found now that I have a ton of traction up front and in the rear, I can turn very easily and always be on the throttle. Neither is a limiting factor (no understeer or oversteer). Ideally what should the car's balance be in tight corners as well as wide corners? If I am on the gas in most of the corners, would that be shifting weight to the rear and reducing cornering (but again I have zero understeer).

My car has a decent setup now, I feel that the biggest gains will be driving now. So if any veteran auto-X / track guys could add something, I'd love to hear it. I am consistently about a second behind a Lotus in my class and that is my first goal to pass.

Please get as technical as you like!!! THANKS!


My car in case you want to see it:
(it is a stock 6-speed, with shaved front RA-1s 275/35/18, full tread 305/35/18 in the rear, pulled pins, maxed alignment, and 95.5 octane fuel)

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      10-26-2011, 09:08 PM   #2
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No one? I feel like a nerd now, haha. Dcstep? No other auto-x regulars here?

I guess the M3 is more at home on a track anyway. Don't get me wrong, I will be running a track setup too, but damn Laguna isn't running till next March! I have to get my motorsport on somehow!
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      10-26-2011, 09:58 PM   #3
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Yeah, once you go track, you never go back
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      11-01-2011, 11:52 AM   #4
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The answer is simple. At all times you need to maximize the available grip for either cornering, accelerating, or decelerating. Keeping in mind that your typical street tire can generate ~0.9 G of grip, while the brakes mated to super sticky tires can generate up to 4-5 G of deceleration force (in F1 cars), the ultimate goal to going fast, is to spend as little time braking as possible and as much time accelerating as possible through each turn.

The way our chapter's autocross is set up, those of us who offer our services to instruct gets about half a dozen laps before anyone else gets to drive. I usually take about 3 laps to get myself acclimated to the layout of the course, then I'll take one to two laps through WITHOUT USING MY BRAKES to give me a sense of the maximum speed attainable through each turn, and where and when I truly need to brake. Then the last lap I will fine-tune my brake point and accelerating point so that I'm either on the brake or on the throttle (no coasting through turns) while maximizing my time on the throttle.

One mistake that I see a lot of rookies, as well as more experienced auto-crossers make, is that you don't always have to brake late. You will be surprised at how much faster you can potentially be if you actually brake EARLY. It's counter intuitive, but I picked this up one time while doing a ride-n-drive event sponsored by a tire company. They have a few "pro" drivers there giving rides in between our sessions, and I picked the brains of one of the pros there, and he showed me that by braking late and nearly on top of the apex on a couple of the turns during my run, I'm actually giving up speed through the turns and the time-slips shows it.
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      11-01-2011, 12:35 PM   #5
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Sounds like you're thinking too much. Start with reducing your brain speed.
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      11-01-2011, 04:19 PM   #6
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Quote:
Originally Posted by The HACK View Post
The answer is simple. At all times you need to maximize the available grip for either cornering, accelerating, or decelerating.....
AWESOME!!!! Thank you!

So that does basically answer my question. So it doesn't make sense to coast through a corner if I could just brake, get to the speed I need to corner at, and then accelerate through & out of the corner.

What else you got!?

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Originally Posted by Richbot View Post
Sounds like you're thinking too much. Start with reducing your brain speed.
Haha perfect quote and hilarius; if you look at the answer it is the simplest explaination that makes the most sense!!! And yes, most of driving is feel and I use that when I'm driving, but I can't help to be nerdy about the "why" behind it!!
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      11-01-2011, 04:29 PM   #7
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Quote:
Originally Posted by Merked M3 View Post
What else you got!?
Go karting. It makes a HUGE difference. Every little mistake gets magnified 10X in a kart, you quickly learn what mistakes are and learn to recognize where, when and how much to brake.
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      11-01-2011, 06:21 PM   #8
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Two days ago, at the last PCA skills day event, my afternoon mentor (I'm an instructor candidate for PCA skills days) gave me some tips for autox. He said that as you approach a cone to go around it, blip the throttle a little to rotate the back, then to get ready for the next cone, lift off a little to improve turn-in.. I thought that was a good advise, hope it helps..

Also, try left foot braking.
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      11-01-2011, 06:27 PM   #9
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It's really true.

There are many things that factor in to driving as fast as possible around an autocross course, but few matter more than minimizing distance. When you're going ~45 mph average, an extra 10 feet is a big chunk of time, so perfect arcs with the biggest radius through the corners is not necessarily the goal like it is on a racetrack where you need to take as much speed as possible onto each straightaway.
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      11-15-2011, 01:02 PM   #10
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Quote:
Originally Posted by Merked M3 View Post
No one? I feel like a nerd now, haha. Dcstep? No other auto-x regulars here?

I guess the M3 is more at home on a track anyway. Don't get me wrong, I will be running a track setup too, but damn Laguna isn't running till next March! I have to get my motorsport on somehow!
Sorry, I was travelling when you first posted and then missed it when I got back.

Seat time is the thing, but here are a couple of questions that might help.

Do you know the most important corner on any course? It's the one leading to the longest straight. Take it so that you can start the straight as soon as possible.

Are you patient in neutral corners? The biggest mistake that I see over and over with students is they jump on the gas too soon and push at the end of neutral corners. I can be sitting right next to them and say, "Wait, wait, wait..." and they'll jump the gas on the last "wait" and push out and screw up the line for the next corner. It's a time killer.

When you trail brake around tight, 180-degree corners, does the car rotate for you at the apex? With those 305 on the rear, you may need to go to the E93 sway bar to get more rotation. Also, I'm assuming that you have 10" or 11" wide rims in the rear, are you running lower pressure in back? I run around 35 psi in front and 28 psi, cold, in the back to help with both traction on acceleration and rotation in corners. You should be getting the feeling that I believe that rotation is critical on most tight AX courses. (Not so much on road courses).

When there's a U-turn, can you carry enough momentum to trail-brake all the way to the apex? I love these corners because few competitors get them right and they're real time makers. Ideally, I'm braking really late and the car is on its nose and the front tires really turning with very little slip and the rear will rotate right at the apex. That's often good for half a second in a lap.

Do you left-foot-brake? I drive a 6-MT and still LFB. Taking your foot all the way off the gas to move to the brake unbalances the car and slows throttle response. (On turbo cars it's even more critical). Roll off the throttle and onto the brake simultaneously and the car will stay balanced. In a slalom this is particularly important, so you can make slight adjustments in speed without loosening the rear. Also, in big, neutral sweepers, if you give a little too much throttle and induce push, then touch the brake with the left foot to transfer just the right amount of weight up front and restore grip without loosening the rear.

That's almost my whole bag of tricks.

Oh, I've got a 4.10 final drive and 275 rears and lauch around 1800 rpm. You want the tires to spin just a time or two or three and be grabbing pretty quickly.

Oh, if you hit the top of second gear in a 6-MT, don't shift up unless it's a least a couple of seonds, then consider short-shifting earlier. Most times you should just stay on the rev limiter for a second or two.

Dave
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      11-15-2011, 03:41 PM   #11
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Try and work the track if possible. You'll be able to get a close up view of what others are doing right and wrong. It's amazing how different things look when you're standing 25' away from the cones. You'll start to almost predict each car's results.
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