SundayDriver

I understand the math and the formulas etc. I understand that if you are on a particular line and on the FC then you can't change things. So this is a great description of a theroetical car that behaves like an infinitely small point acted on only be external forces and no internal dynamics, being driven on theorectically perfect tracks on theoretically perfect tires but a theoretically perfect driver with theoretically perfect brakes.

I am so far away from being a perfect driver, and my car is far from perfect and it has suspension that responds to the not perfect tracks I drive, etc, etc. This has drifted so far from any reality I have ever seen on a racetrack and unfortunately, I contributed to that drift. I will focus my efforts on my own inferior driving and inferior car and will have to live with missing the fc a bit and changing my line from time to time, and even from lap to lap.

Sorry for helping to drift this topic.

JCP911S

Lets just re-position this as a drifting competition....

Seriously, Sunday Driver is right. The realities on the track are that the car is under so many different forces, bumps, track camber, weight shift, varying surfaces etc that the car has a different fc at almost every point in the turn.

The skill of driving is constantly adjusting to all of these to keep the car at the limit, but this is an athletic excercise done with the feel of the car through your hands and the seat of your pants.

Just becasue you can mathmatically describe the trajectory of a football does not make you Brett Favre, and never will.

RedlineMan

Hey JCP;

No problem. It is so hard to write about this stuff intelligently or clearly or completely because there are so many infinite variables involved you can't hope to get them all in without crashing the server.

I tried to think of a turn where I trail brake. I mean that in the rotational sense where I need to change the direction of force to make it through. Out of 5 tracks I've driven, I couldn't think of one. Big Bend... MAYBE.

I balance brake in most EVERY turn, however. I do this because I have pretty decent entry speeds. To the extent that this happens after turn in, and is done to keep the car settled and balanced, it can be considered trail braking. I make a distinction there. Many people don't. Even while Im "trail braking" I'm almost universally on the gas as well. When LFB has settled the transition

The Inner Loop? I stay in 4th, LFB moderately on the straight, and then am back on at least 60% throttle at turn in. I'm at full throttle by the third apex!

Mitch -

I'm with you. My brain was concurrently aching as you were typing. When my head starts to hurt, it is time to drive. All this theoretical flagilation is intriguing, but it doens't mean squat if you can't also drive instinctually.

Me? Seat of the pants all the way. I already drive pretty damn well I think. Acq would help me get better, I have no doubt, and I will be pursuing Acq capability in the near future.

I would never use it to try and learn how to drive, however. Without honed instinct, you will never acheive application of that data. Skill first, then fine tuning. I don't see it working any other way.

JCP911S

Redline... sounds like you are trail braking... just doing it so instintively that you are not really aware of it... and yes Big Bend is probably the textbook case of a hard trail braking turn... at least for me.

I think Data Acq is more like a coach... telling you where you are leaving speed on the table and what setup changes work... but it can't teach you to drive. part of me wants to use it and part of me doesn;t want to spend my precious track days staring at a #$%#&# computer.

Bob Rouleau

CC - Yes I trail brake the GT2 into slow turns, fading off the brake pedal later to rotate the car - compensating for understeer in tight corners. It does require finesse because as you imply, there is a fine line between reducing understeer and provoking unwanted oversteer.

This weekend I drove a very tricked out 996TT, I trail braked it like my own car and was rewarded with a bang in the foot as yaw control kicked in. Yaw control is an element of PSM which is always active irrespective of the switch position. I suspect you might have felt it. The brake pedal comes up and hits the bottom of your brake foot quite hard.

Rgds,

ColorChange

Bob:

I am also concerned about the PSM kicking in. What I haven't done is analyze the data to see if enough yaw to kick PSM in is too much and slow driving, or if the PSM is intruding when driving fastest. I don't know yet. Your opinion?

I have been braking fairly well hooked up and then using the throttle to induce rotation during the neutral phase of the turn. You could also do it with the brake just like you indicated.

DJ

Hey Bob,

While I haven't felt the *bang* in the foot, I have felt the pulsating push-back from PSM when trying to trail brake. I hate it.

Where this bothered me the most was the entry to T5 at Willow Springs. Fast, steeply downhill right-hander on the approach to T5 (which is a left-hander at the bottom of the hill). The track straightens almost imperceptibly after kinking slightly tighter to the right in only the last 30 feet or so before turn-in for T5. Now normally, without PSM, I'd brake gently--but just hard enough while the car is still turning to the right to slightly rotate the tail to the left--which lines up the car perfectly with that tiny bit of straight so that you can brake really hard just before turn-in to T5. At turn-in, I'm easing off the brakes just slowly enough to cause the rear to start to rotate back to the right, aiming me right at the apex and allowing me to go to full throttle as soon as the car begins to turn. With PSM, this line is not possible.

Instead of allowing the tail to rotate slightly left so that you can brake hard on the tiny straight bit, PSM kicks in and keeps the car straight--and no longer on the line. Now, instead of a bearing of 0 degrees (relative to the short straight bit), the car is now on a bearing of 350 degrees or so, and too far to the left by about two feet, causing a slightly shallower entry. Then, instead of allowing the tail to swing a bit to the right at turn-in, PSM crashes the party again and keeps the car straight, forcing you to wait a beat or two for the car to turn more before going back to full throttle. The only way to do it in a PSM equipped car is to go slower. There's two tenths (or more) in that corner entry alone.

Bob Rouleau

HI DJ,

The 996TT I drove had an Autothority suspension (like PSS9) engine mods and R compounds. With this set up PSM did intrude and I agree that it costs a few tenths. I had PSM off and contrary to legend, it stays off. Yaw control is always on and it does not like braking and turning at the same time. I'm surprised that you felt only a pulsing. Maybe it's a model year thing. When yaw control kicked in (and I mean kicked!) the brake pedal was pushed up hard - lifting the pedal and my foot about two inches. I described it as "banging" my foot. At the same time, it straightened the car out (diagonal braking perhaps) and messed up the line. Better driving through electronics I guess .....

Rgds,

DJ

PSM or YC, it still messes with the car. You could be correct though that different model years bang your foot diffferently, or maybe the mods on the car you drove affected it, or maybe my feet are bigger and it couldn't push back as hard? It definitely pushed back, but less than an inch, not two inches like happened to you.

Maybe Color Change should figure out a way to disable his PSM and YC along with all his other mods. I mean... the goal is to go faster, right?

ScottMellor

DJ. Que Pasa?
Do you happen to have any video of your line around Big Willow. I had a hard time settling on a line through the 5/6 series. (I've got Marks Radical footage, but I still don't have a good mental image through there.)

DJ

Hey Scott,

Sorry, no video of me in a Porsche at Willow. In fact, all my online videos are gone, and all I have is some video of the Radical on DVD. That said, if you've got video of Mark at Willow, our lines are the same (plus or minus a foot here and there). Here's some text that might help you with the video:

The entrance to T5 is really faster than it looks, but you'll never make it fast through the entry if you hold the car to the left--you've got to let it run out wide to the right after a fairly early-ish apex. Waaay out to the right. There's lots of track out there that most people don't use. As soon as the car gets out there you need to start coaxing it back in to the left, and get to the middle of the track (or better) as you start up the hill for T6. The car wants to unweight at the apex of T6 because you're cresting the hill. The more throttle you've got on before (and at) the apex of T6, the more stable the car will be. Try short-shifting up a gear as you start up the hill, and go flat over the top. This will keep enough weight on the rear to keep the car from getting sideways at the crest. You're still going to drift down the other side, but it will be controllable, and not tail-out. Also, you don't want to be turning the car as you crest T6, you want all the turning to be done before the crest, and just sort of angle over the top with the wheels pointed mostly straight.

ScottMellor

OK. That's a help.
I just watched the video again. The text + pictures finally got through

DJ

Great.

I better go catch the mailman, as I guess the coloring books and wooden blocks I mailed to you won't be necessary...

JackOlsen

This is a good point. I remember how scary the crest of the hill seemed, early on. You definitely want your wheels pointed straight as you go over it, but it's a turn that (surprisingly) gets easier as you start going through it faster. What's more (as DJ points out), you don't need to be as far to the left at entry as you might initially think. I drive it on street tires, and am always amazed at how much the car holds as you carve through it.

ScottMellor

Ouch!

I kinda got it right on my last run of the day and absolutely launched up and over 6.