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Motorsports & Track Forum
From Auto-X to Trackday to Racing and Professional Motorsports this is the place to discuss making BMWs fast

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Old 02-27-2006, 12:04 PM   #1
323iT
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Taking the "right line" autox

So I havent autoxed in almost 5 months. and before that I did about a season of autoxing. Most of the time I just do fun runs. Since I was using autox to learn the limits of my car and my ability to control the car.
So I've been improving my driving style. And I came across a situation that I dont know how to deal with last weekend I went autoxing.
Near the end of the course, there's a sweeping left turn with a sharper right turn right after. and a slight left after that. Out of all of my 3 runs, I always end up going too fast into the 2nd turn (right). And I end up understeering through that turn and the turn after that -.-
So I was wondering if it would be better to braked more and slowed down more to make the turn, or do what I did which is enter the corner faster and understeer and come out slower? The way I see it, the time would be about the same?
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Old 02-27-2006, 04:45 PM   #2
TwoE46s
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This almost sounds like turns 2-3-4 at Road Atlanta, minus about 40 or 50 mph.

From what I am reading, the sharp right is the limiting corner of the sequence that is much slower than the previous and following sweepers

It would appear to me that you need to have a very late apex on the sweeper, creating a straighter line through the end of the corner while trail braking for the tight right (the sweeper is faster than the tight right, so you'll have to be under your optimum corner speed on the sweeper to trail brake - if you don't trail brake, you'll be either way to slow through the sweeper in preparation for the tight right, or too fast for the tight right as you have found out already)- at turn in to the tight right, you'd try to be on the far left at the end of the sweeper (although with the trail braking at the limit, you may comproise being as far left at the turn in as you would like, opening up the end of the sweeper to complete your braking), with a late turn in / apex for the tight right. You would then move out to the entrance to the final left sweeper takeing the inside line until your appropriate exit point.

At least that's the line that I see from at track perspective where you have a little more room to operate than autoX........
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Old 02-27-2006, 07:16 PM   #3
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It might help to post up a quick Microsoft Paint diagram of the general shape of the turns you're refering to.

The shape of the turns will have alot to do with positioning both of your car and brake points. Nice thing about autox is that you're never really worrying about shifting whereas on the track, you have have to do some quick downshifting action.

In any event, if I'm visualizing it right, TwoE46s has it right. But you left out one key fact. The third and final turn after the sharp right. I assume its a left. But in any event, you're going to want to set up as far to the right entering the first left with a late apex and come across the left turning sweeper's typical apex very late. The speed should be lower than a typical left-turn sweeper because you have the sharper right to contend with. Trail braking can be tricky and I'm marginal at it so slower travel through the sweeper might be easier and safer. Then again, if you got the cahones, trail brake right after you've hit the apex and are travelling to the left most part of the track. Then begin your turn in. Apex the sharper right turn and accelerate to make up lost speed. Depending on the final turn, you may need to hold back a bit on the throttle to set yourself up correctly again.

I'm no expert by any stretch of the imagination but thats what I'd do if I'm picturing the turn series correctly.

Enjoy!!
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Old 02-28-2006, 08:57 AM   #4
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I keep thinking about this line............... and yes a diagram would be helpful, and / or a description of what comes before the first left sweeper.

But here is a revision of my thought....... which is kind of a mix between what I first said, and JC's comments. Racing is as much of an art as a science, so there may not actually be one perfect right answer.....

With the first left sweeper, you are going to have to trail brake to set up for the much slower tight right as noted earler. However, I'm now thinking that you'll have more of a constant radius turn in to keep speed up on entry, then as you trail brake, you'll be slowing faster than the max speed for the raduis of the left sweeper, allowing you to keep the car more to the left longer, giving you a better late turn in to the tight right. What is so odd with this, is that you are braking at the apex of the sweeper instead of accelerating.

When you come off the tight right, you will be under the max corning speed for the raduis of the following left sweeper, so you'll want to take the shortest line (inside) until you reach max for the turn radius, or you unwind at the exit.

Just a note of what's different on this line than my first thought based on Road Atl, is that for the turn in on 2, the left sweeper, you're still actually accerating (not braking) because you're slower off the exit of 1 going up hill than max for the turn in radius of 2 so you can pinch the turn in creating a very late apex point and really making from the turn in point to 2 to the turn in point to 3 much less of a turn radius making the trail braking a bit easier. You actuall trail brake well after turn in for 2, as you prepare for the tight right turn 3. And what makes this all the more fun, even though the turn through 2 isnt' very sharp is as you brake, your cresting the hill which unloads the rear even more as you brake for 3.
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Last edited by TwoE46s; 02-28-2006 at 09:01 AM.
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Old 03-01-2006, 02:38 PM   #5
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I guess what I'm really asking is that if the way i took those turns are the "fastest" way. They set up the last turns of the course to slow everyone down. even tho most people dont. I'm pretty sure that my understeering could've been fixed by braking harder. But is slowing down to a speed that I wont under steer be faster than just going and under steering through those turns?
I did enter the sharp right turn from the inside but coming out of it i under steer
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Old 03-02-2006, 12:05 AM   #6
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oh wow...that IS nuts


imma cross post over to bimmerforums in hope of faster replies...since they have an awesome motorsports subforum
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Old 03-02-2006, 07:22 AM   #7
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Hard to tell but if it actually looks like the drawing, stay tight in the LH sweeper, brake sufficiently so you don't push way wide on the exit of the RH hairpin. You want an EARLY apex for the last LH turn. There is no straightaway after the LH turn before the finish - the early apex will get you to the finish lights quicker.

Sounds like you're trying to carry too much speed into the RH hairpin. BMWs are big fat heavy cars with poor suspensions - they don't work particularly well in low speed corners.
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Old 03-02-2006, 09:26 AM   #8
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That picture does help alot. I would go with what Solo said. Instead make a very LATE apex for the left hand sweeper. Basically start your turn on the right side of the track when the track veers left, keep it tight and then go into the tight right to set up for an early turn in and apex for the final turn.

Tough set up though!!
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Old 03-02-2006, 11:47 AM   #9
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There are a couple of reasons I dont' autoX anymore, and set ups like this are one of them!!!! However, I must say I have a lot of respect for autoX people, with one reason being that they can figure out the lines for a set of corners like this!

I think the one thing you have to keep in mind, is as you said origially, this set up is to slow you down for the finish........

I do still belive that you treat the first left as a traditional decreasing radius turn, trail braking through corner entry, and have a very late turn in, allowing you to basically drive straight down the left side of the track at corner exit, braking again for the right.

The turn in for the right however, I think is determined by where the finish line is with respect to the last turn which I can't tell from your picture. You really need to work backward from there. In any case, you have a late (or very late) apex on the right, (the later the turn in actually gives you a longer braking line for the right), with your exit line determined on how far to the right you need to stay for the final left turn and he appropriate exit for the finish.

With regards to your question about speed vs driving though an understeer, I think there is no question that you are very slow when you are dragging your front tires sideways, so you need to slow appopriately and let your tires roll....
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Old 03-02-2006, 11:15 PM   #10
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e-brake.. i duno.. im in a 330ci, so i just abuse the big brakes and power and i just brake harder and later, and then get on the gas hard again.. i've learned that the racing line is good in auto-x, but sometimes the shortest distance is the best.. and a corner like that .. i'd say just power over and slide ur tail around that..
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Old 03-03-2006, 03:46 AM   #11
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Quote:
Originally Posted by valenti
and a corner like that .. i'd say just power over and slide ur tail around that..
pretty much everyone had their rear out after that last turn. I did it a couple times myself
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Old 03-29-2006, 01:24 PM   #12
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