Could someone please detail the H2T technique?

My how this thread has diverged...

How about H2T while DC?

You need to do that for a 180 degree autox turn in a car with no torque and bad synchros.

I hear the Skip Barber school makes you learn/use HTDC in their formula fords.

This seems like a good description:

http://www.edmunds.com/ownership/howto/articles/45792/article.html

<----- waiting for someone to post that heel/toe on a modern car actually involves putting one's heel on one pedal and toe on another....

you mean heel/toe is with your right foot?!

and here I was always doing it with my left foot on the clutch and brake. :confused:













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Yes, and I believe the gearbox in those racers are straight with no syncros.

Double clutching (actually, the more appropriate term is "Double Declutching") is not really necessary on our modern Porsches. That's why we have syncros in our cars!

Now heel-and-toe downshifting IS a necessary thing when downshifting in a performance venue like at AX or on the track.

Note that if a heel and toe downshift is done properly, the change to the lower gear should have ZERO effect on the braking attitude of the car. Many, many folk will downshift without heel/toe and use the compression of the motor to slow the car down. Sounds cool - feels cool, but it's not the right tool for the job - use the brakes to slow the car - not the tranny and motor!

Ok, so what the heck is heel-toe downshifting and what is it used for? In a nutshell, it is used for getting your car into a lower gear while under braking without upsetting the balance of the car. This requires the use of the clutch pedal, brake pedal and throttle all at the same time. Problem is, we only have two feet, and there are three pedals that need to be worked simutaneously!

So, here's the technique as best as I can describe it:

1. You're tooling down the front straight of your favorite race track, and approach the braking zone. You fly past the marker you've chosen to start your braking. You move your right foot off the throttle, and onto the brake pedal.

2. After you've started to get the car slowing down, and weight transfer is occuring, you now need to shift the car into a lower gear. While 4th gear was good on the straight at 120mph, you'd be better of in 3rd for taking the corner at 70mph. Otherwise, in 4th you just won't be able to accelerate out of the turn as swiftly.

3. While you're still braking, you want to switch to a lower gear. You can simply put the clutch in, switch to a lower gear and pop out the clutch. But that is NOT advised. You see, as you push in the clutch, the revs of the motor will drop, and as you release the clutch and you're in a lower gear, the motor will rev up suddently, and upset the balance of the car - you may even momentarily lock up your rear wheels due to the sudden engagement of the lower gear. Remember - you're already balancing the car and trying to smoothly transfer the weight to the front of the car. Popping the clutch in such a manner will not result in a smooth transition.

4. So, instead of just popping the clutch out once you've selected the lower gear, you do the following: while your right foot is still on the brakes, you pivot or rotate your foot on the ball of your foot towards the right - catching the throttle with the right edge of your foot. You give the throttle a good blip, causing the revs to go up.

5. As the revs start to drop again, you disengage the clutch and as the lower gear 'grabs' the revs of the motor are in synce with the speed of the car and the balance of the car is not effected.

6. In all this time, you're still travelling down the track - and you should be nearing the end of your braking zone, and the start of your turn in. So, you're still on the brakes, but now, you're in a lower gear, and when the time comes, you can roll your foot off the brakes and transition onto the throttle and squeeze-squeeze-squeeze on the throttle as you approach the apex, trackout and proceeding straight.

Note: if the corner requires a technique called 'trail braking' you should be done with the heel toe downshift prior to getting into the section where the braking and the turning overlap (ie trail braking). If the corner does not require trail braking, you'll be done with the heel-toe-downshift prior to the turn-in-point.

This technique is essential for track driving. While not essential for street driving, many track drivers use this technique on the street to stay in practise. It doesn't harm anything - and it is a good technique to be familiar with.

Now go forth and heel-and-toes!
-Z-man.

double clutching is fancy schmancy but pointless on a synchro car

if you really want to be different , try left foot braking...

Yes, trail and left foot braking- as (I think) J.Stewart once said -the last thing he learnt was how to come OFF the brakes. (ie, speed is about grip, and grip is about weight transfer) Left footing is great thing to learn. Funny tho, the advent of cameras all placed all over racing cars, many pros dont do it.

I wonder about trail braking in 911s...the nature of the car is that its very hard to upset once it pointed in the right direction, and the weight settled over the rear wheels-then you can use (almost) as much grunt as is available to drive out of the corner. As it was put to me once, to go faster...brake harder, concentrate on line and get on the power earlier and earlier....its all about exit speed.

rail braking is handbrake work.. left foot braking is all fours...let's not lock up the brakes... that's the tricky part... left foot is not delicate...

Thats not correct. Trail braking is using, often the left foot, to carry braking deeper into the corner so as to keep weight (and therefore grip) and susension load on the outside front tyre to aid turn in. And hence Mr Stewart's remarks about how to come off the brakes, so as not to unbalance the car with abrupt weight transfer.

The left foot can be very delicate, it just requires, as always, practice and patience.

Been trying to read up on some of the DC and H2T threads the last few days. I have also been reading Elford's book. Man, I have SOOOOOOOOOOOOOOOOOOO much to learn about driving this car...

One thing I am still sorting out in my brain: the blip or rev points? Meaning, is there an actual RPM you are revving to before declutching? I would think if that is the case, it might be different for each shift. I have yet to read on any of these threads what those RPM's might be for each shift though. Is it more of just getting the revs up in general before the declutch?

Thanks... And here I thought I was a pretty smooth shifter...

Not necessary, but not really pointless; saves the synchros, if that happens to be a concern (the double clutching process is a synchronizing process - you must do it to shift a crash box - except, see below) and with some trannies is quicker than forcing the synchros, which ain't good for the synchros).

Or, if you want to save the synchros and the clutch, shift without using the clutch (up and down the gears) - do it right and it's smooth as butter (can be quick too), do it wrong and blow the tranny :). Of course you do have to use the clutch starting from a dead stop.

Like you pointed out, the answer is "depends." It'll vary depending on your vehicle speed, and the spacing between the gears. I think most people who do it would say they do it more by feel/sound/experience than anything else. You're certainly not taking the time and attention to look at the tachometer while doing all this.

I have Elford's book on performance driving. I am going to find Bondurant's book as well and try to read them both sometime this summer.

[QUOTE=v8_ranch;3989551]...is there an actual RPM you are revving to before declutching?

Yup.

I would think if that is the case, it might be different for each shift.

Yup; and different for every MPH also :).

I have yet to read on any of these threads what those RPM's might be for each shift though.

The RPM is determined by the gear AND the MPH when shifting.

Seems it's more difficult to 'splain double clutching than it is to double clutch :).

This will hopefully answer your question.

1) Drive at any steady speed you choose in, say 3rd gear.
2) Note your RPM at that speed - let's use 4500 RPM here.
3) Shift into 4th gear, and maintain that SAME speed. Your RPM will, of course, drop.

Now:

4) Double clutch back down into 3rd gear, i.e.,
a. depress the clutch,
b. put the lever in neutral,
c. release the clutch,
d. rev the engine to the RPM that it would be turning if 3rd gear were engaged,
which is...4500 RPM!
e. with the RPM at 4500, depress the clutch,
f. move the lever into 3rd gear,
g. release the clutch - if you've executed everything perfectly (not likely, 'cept
maybe occasionally) you could side step the clutch, letting it fly up with its full
force, and there'd be nary a jerk or a shudder because everything is
perfectly synchronized,
h. Apply the same principle to all the other gears ya got.

Upshift double clutching is exactly the same, if you choose to do it, except for blipping the throttle to bring the revs up - when upshifting you wait for the revs to drop.

It ain't mysterious or hard to do. All it requires is tuning your ears to your exhaust note. You won't even need a tach (the old Chevy I learned on didn't have one). Once you get the hang of it you don't even think about it (like you don't think about how far to turn the steering wheel when you're driving :)).

Oh yeah...fuggedabowdit on the track if you wanna win./QUOTE]
..

Is this really all that complicated? Release clutch = push pedal down. Declutch = BS, it's not even a word. What about unclutch, reclutch, pre clutch, post clutch, post clutch partum depression? Find something to do. Maybe go through the transmission of whatever is this hard to shift. My 928 is the slickest shifting stick I've ever driven. The only way I'm double clutching is if my foot slips off the pedal.

If you applied this same type of analysis to walking, you'd be on all fours with your knees busted.

Check out this video

http://www.blancomedia.com/shell/heel_toe.html

See Walter Rohrl video.....

http://www.youtube.com/watch?v=yyVHj3sHVHQ