Mark in Baltimore

Mitch,

I've become so comfortable with LFBing on the street and the track that it is exactly those surprise situations you speak of where it can be really helpful to be able to apply power and also to take away just a bit of speed to precisely thread the needle. I feel more in control with my left foot over the brake and, consequently, feel a bit naked when I don't do it. Who knows, maybe I feel better because I'm braking more and, therefore, going slower.

Mike in Chi

Mark

"Who knows, maybe I feel better because I'm braking more and, therefore, going slower. "

You make it sound so dirty...

ColorChange

John:

Yes I am opinionated … guilty as charged. But, I usually try to separate my opinions from my statements of fact (and yes, if I blow a statement of fact, I will admit it and change my viewpoint).

John, if I understood you, this is wrong for any normal turn, even in an extremely underpowered car. If you don’t drive like I have described for normal turns, you aren’t closest to the fc. Let me explain.

If you approach a turn that requires threshold braking, you hit the hooks at your braking point (maximize – long g’s). You decell until you hit your trail braking (tb) corner entry speed (higher than non tb corner entry speed). You lighten up on the brake pressure and turn in, while trading - long g’s for increasing lateral g’s (keeping your g sum as high as possible during the transitions, whether a fast or slow transition). At some point you hit max lat g’s where you have 0 long g’s (usually in the ballpark of the apex, earlier on momentum cars, later on high powered cars). Then, you trade lateral g’s for + long g’s (accell) on through track out. During the whole turning process, your goal is to maximize g sum.

If you are on the gas before the turn in, you have simply over braked significantly. A DAS would show you this conclusively. What you should do only brake to amount necessary to hit your turn in speed. Trade – long g’s for lat g’s, then trade lat g’s for + ong g’s.

Now, what you described could be correct for high speed sweepers in an over steering car but this is not normal.

All right, you certainly implied you downshifted twice but OK. The only time I can see that it is advantageous, to double downshift, is when you are having braking problems. Are there any other times? If so, please explain.

Mark in Baltimore

Mike,

I'm only dirty when I "feel naked and don't do it."

Whatever the hell that means.

wch

"I started left-foot braking in 1994, and soon worked out that it was the only way to be really smooth. Right-foot brakers have to get involved in a hell of a lot of extra footwell movement; every time they take their right foot off the accelerator to hit the brake, the car is unsettled. Left-foot brakers can keep a little bit of throttle applied even under quite heavy braking; that way, they're quicker onto the power as they apex, and the car is better 'set' to accept that power."

Mike Hakkinen in F1, March 2004


I personally LFB full time in a car with a sequential, but am living proof that one can LFB and still find the slow way through a corner. Cheers!

RedlineMan

Well Color;

We could go around and around forever, I'm sure. It usually doesn't take too long before I lose interest or can't see through the brain smoke. Suffice it to say that my emphasis is on driving.

There are as many ways to get right spot on the FC as there are permutations of throttle & steering positions, and entry speed. As such, then theoretically EVERY combination that puts one on the FC is a perfect combination if you live by this model heart and soul. I don't.

I know that there are good ways, and then there are better ways. Those change by the day, and sometimes even the lap. All the theory and acq in the world can't drive the car for you. It is merely a tool, and can interpreted as wrong as it can be right if the data is misapplied.

All I can say is come for a ride where the rubber meets the road. I won't thrill you with hyper top speed, and I'm certainly not the next coming of Senna, but I guarantee your neck will get tired before I do, and NOT because I'm not smooth!!

Bob Rouleau

Great thread guys. Hi Pete, while you;re in Latham I'll be with Ellen - becoming a disciple.

Here's a couple of thoughts on LFB. I like it myself - it's easier to balance the car - I think this has been explained. On a turbo car it also keeps boost up which pays dividends at the exit.

The bummer is that new cars with PSM won't let you LFB for more than a few seconds. Those drive-by- wire systems (like the one on your TT Color) cut the throttle if you apply power while braking. I had a nasty experience in my Audi 2.7 TT because of it. Right at the apex the power cuts out - instant yaw! Fortunately my GT2 has no such thing and LFB is a useful technique.

I read the article in F1 which compared Reubens and Michael - the latter would pick up a tenth here and there with LFB. Also interesting is that Michael was not using LFB for better braking (less lag between release of gas and applying brakes) rather he was using it to balance the car. After seeing the article I wondered how long it would take Reubens to adopt the same technique.

Best,

Chris Campbell

So.....

Can I blame you guys if I rear-end an Expedition or ML430 on the way to work tomorrow morning


Good stuff. I definitely need to work on my braking and turn-in technique and this may be the ticket.

Steve in FL

Bob: The throttle cutoff isn't necessarily a PSM feature but part of the EGas system as the GT3 reportedly has the same behavior.

Bob Rouleau

Steve - you're right it is a "safety feature of the e-gas system which assumes that a demand for power and brakes is probably a run-away engine caused by a computer failure. E-gas is required for PSM and is on all the new Porsches. I guess my LFB episodes on the GT2 are within the time limits of the egas system but I am going to experiment since exceeding the time limit would cause a very unpleasant outcome in a high speed corner!
Regards,

mitch236

Isn't there a way to permanently disable PSM on newer Porsches? I can't believe they would have it on their GT-3, which is touted as a race care for the street.

DERSIX

Mitch,
Turn one or the Carousel..Turn 3 and around the turn...I would be nervous using LFB in turn five. I go from fifth to second for that turn...
I have been to Sebring twice now in the last 3 months...now that the warmer weather is returning in the North, I am staying closer to home....except for Texas in July, I will see you guys next Feb...
Pete

mitch236

Pete, thurn 5 is the end of the carousel, you might mean the safety pin which is turn 7.

Steve in FL

Bob: Apparently the EGas throttle cutoff threshold in the GT3 is 1.5 seconds. Here's the thread discussing the topic on Renntech: http://www.renntech.org/forums/index.php?showtopic=548

Bob Rouleau

Tch - I am sure it is possible - if I knew which signal to the ECU monitored brake application I could fake it out. Maybe someone knows but probably for liability reasons, Porsche did not make it easy to do. If the computer or software screws up there is no connection between the gas pedal and the engine except via the brain box. Same a fly-by-wire on some airplanes. Scary when you think of it. I'm grateful that they don't use Windows for the task!