Heel/Toe

I know there have been other threads relating to this subject, but I need to know if it's possible to raise my gas pedal. My '85 Carrera (euro) is set up such that I would need to pull my foot off and screw it on backwards to have any chance of heel/toeing.

Can the pedal be raised? And by how much? I'm really not interested in adding any blocks.

Thanks for your help.

Don't take this as insulting please, but are you sure you are doing it right? Remember that heel-toe comes to play usially under HARD braking... (Because if you aren't braking that hard, you don't need the extra braking from downshifts, why wear the tranny)...

It is adjustable, there is a threaded rod with a ball joint. Pull the pedal forward to expose the rod and lengthen it.

Thank you..no I'm not insulted at all.but even on extremely hard breaking the pedals just do not line up.

I don't want to insult anyone either, but you don't use heel-and-toe downshifting for the additional braking that downshifting can provide -- you use it to avoid the additional braking that downshifting can provide. Using the transaxle and engine to slow the car down is not only hard on the clutch and tranny, it also is much more difficult to control than the brakes. If you're braking at the limit already, and then you throw in the inertial resistance of the drivetrain, you're likely to upset the weight transfer and balance of the car, unpredictably, just as you should be increasing the engine speed to exit from the turn in the correct gear. What you don't want is any time lost bringing the revs back up once you've finished braking -- you want a seamless transition between hard braking and acceleration, with the engine providing the acceleration immediately on the heels of the brakes doing their job.

At least, that's how I understand it. Now, anyone can feel free to correct me. I won't be insulted.

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Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

Jack,
You're absolutely correct. This is my first 911. I grew up on a 2002 tii and I could heel the gas pedal or tap it with the right side of the ball of my foot; I'm having great difficulty doing such in this car, because of the discrepancy in the 2 pedals.

Jack, Well yes and no. Heel-toe IS designed to match revs and therefore not stress the engine and trans. as well as to be in the right gear as you try and accelerate... However downshifting while braking DOES provide additional braking through simple enregy absorbtion.

So... You do use it for additional braking, but not during the clutch release phase. If you are at the braking limit, you still get additional braking. If you are absorbing that energy back into the engine (via compression) then you will slow down faster. It took me a while to bend my mind around this, but it is true and I have verified it at the track.

I'm not trying to sound condescending here, It's just what I have experienced...

[This message has been edited by cstreit (edited 03-08-2001).]

When I was at the 1999 California Challege autocross, rally, and concourse I had a chance to ride with Professional driver Bob Garretson. He told me not to use heel toe to help slow the car down. He said to let the brakes do the work. However, as several people have stated you DO use heel toe to match the revs when entering the corner.

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Joshua Harrison
1968 912 Coupe

I don't want to make a big deal out of a small point, but...

Downshifting while braking does provide additional braking force from the drivetrain, it's true. But think about it: that's exactly the reason you use heel-and-toeing in the first place -- to minimize that inertial braking. Why else would you be doing it? If you don't heel and toe, you get a massive lurch of engine braking when you release the clutch (because the revs of the engine are insufficient to match the speed of the now-engaged drivetrain). To say that the additional braking provided by the mismatched engine revs is helping you stop better is really missing the point. There isn't a Porsche manufactured brake setup that isn't capable of locking up the wheels of a 911 at virtually any speed the car is capable of going. So long as they're kept cool, the brakes are always more than adequate for the job of stopping the wheels from moving. But as anyone with a couple of flat spots on their Dunlops can tell you: stopping the wheels isn't necessarily stopping the car. The trick is maximize the ability of the brakes and the tires to stop the car, and that means eliminating as many of the factors that would interfere with the tires ability to grab the track (specifically: unesttling lurches and changes in deceleration) as possible.

Physics majors will split hairs on this point, and I'm not saying it's the only factor, but the most important reason you go with larger rotors and calipers is for heat dissipation -- you just can't stop very well when your brake fluid is boiling. That the larger calipers and rotors also increase your degree of control over stopping is nice, but -- like I said -- the brakes off a 912 can lock up a twin turbo's wheels pretty consistently.

Now, I'll be the first to admit that I'm simplifying some things here, but it's to make this point: the most limiting factor in stopping or slowing a car is tire adhesion, and that's why you use the heel-and-toe technique. It minimizes the lurching caused by the drivetrain's inertial braking. It allows you to make the transition from fast to slow to fast again as smoothly as possible, which allows the tires to grip the track consistently and effectively. Outside of steep hills, using the brakes is the most effective way to lower a car's speed smoothly. Adding the engine's inertial drag to the process only increases the likelihood of the car braking too much, or too unevenly, and the tires consequently losing their adhesion. Again, the goal isn't simply to maximize braking -- that's easy -- it's to maximize braking within the limits of your tires' ability to grip the track.

There is incidental braking force provided by everything from the inertia of the drivetrain to the drag from the tires to the gas sloshing around in the tank. All of that is "used" in the course of driving the car, but all of that needs to be minimized so that the brakes can do their job in as uninterrupted a fashion as possible -- so that the driver can control and maintain the braking force so that it is smooth, and consequently able to be kept just inside of the limits of the tire's ability to hold onto the track.

I'm no scientist, and I'm only an amateur when it comes to driving, but the point of the heel and toe technique seems to be clear enough. It is there to relieve the engine of as much braking work as is possible, so that the driver can brake with the brakes, and then proceed to accelerate with the drivetrain.

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Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

[This message has been edited by JackOlsen (edited 03-08-2001).]

I had to raise my gas pedal about 2cm to easily heel and toe. I used one of the aftermarket pedal kits that attach to the stock pedal, also extends the gas pedal closer to the brake pedal. Heel and toe is now easy

I don't know how to put this, but heel & toe has nothing to do with "additional braking" as some of you put it...

Heel and toe is used simply so you can downshift, while braking! This way you won't waste time when it's time to accelerate. A SIDE effect is that when the clutch is released the car doesn't jerk much, kind of like Jack says, but I'm not sure I agree with all of that post...

Engine braking is not the intent of downshifting, midway through a corner, (specially if you use heel&toe) it's for saving time, by being in the right gear at the exit of the turn. Matching the engine rpms keep the rears from locking up, it's easier on your transaxle, but NOT to provide braking with your engine. Not a little bit, not smooth extra braking, that's NOT the purpose!

A lot of people, (including me on occasion) keep on the gas VERY lightly, as the clutch is being released, to not have any additional drag on the rears, if required.

Hope I didn't offend anybody with this post.
Ahmet

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It's all the driver...

I agree with Jack! Enter the corner slow and exit fast!
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I have been taught, when approaching a corner, to threshold brake to reduce speed for entering the corner, downshift at the last moment prior to turn-in, make your turn in, and then ACCELERATE through the entire corner.
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When making the downshift, "roll" your foot quickly on the gas for a "blip" to bring the rpms up to match the wheel speed - when you release the clutch, the car remains "neutral", that is, NO braking action from releasing the clutch. At that point, you are mashing the gas pedal at turn-in. This provides the downforce you need to take the corner faster. - You want to be accelerating through the corner, not braking or "coasting" through it. To accelerate, you need to be in the correct gear, BEFORE the turn in.
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Let me climb down off my soap box before I fall and hurt myself.
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Chuck
83SC
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ps, I use "the Third Foot" from Wings Engineering - the aluminum gas pedal that slides over the existing one - It raises the level of the gas pedal so that under threashold breaking, the gas and brake pedals are nearly on the same level. Helps people like me with short stubby legs that don't bend well at the ankle.


[This message has been edited by patalive (edited 03-09-2001).]

[This message has been edited by patalive (edited 03-09-2001).]

Someone mentioned that if you are on the braking limit you could use the engine for extra braking power. That is not true. If you are on the braking limit – that’s it. Braking depends on the laws of friction that depends on the tires and the surface and not if you are using brakes and engine.
I definitely agree with those of you who say that you should not use the engine for braking, cause that’s what your brakes are there for. Also you can overrev if you use your engine that way and the rev limiter can not prevent it.

just my thoughts, Bjorn

The gas pedal *is* a little low in relation to the brake pedal for optimum heel and toeing, at least on the SC and Carreras.

It can still be done, but it is far more difficult than on most other cars. If one is an experienced heel and toer, its not a big deal, but a 911 would be a pretty difficult car to learn on, in my opinion.

Once you learn it, it can become as natural as regular shifting. I heel and toe on almost all of my downshifts in regular street driving, without conciously thinking about it anymore.

Heh Chuck
Where did you get this 3rd foot, wings engineering, have heard of it mentioned before but have not heard a source.
Does it change the shape of the Gas pedal as well?.
thanks in advance
Ben

Ben,
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Wings Engineering advertises in Excellence magazine - - but you can reach them at 203-438-2222 - they are located in Ridgefield, CT. (no web site indicated) $99 for the standard version and $105 for the Xwide version. The owner talked me out of the Xwide version - said the standard is fine for most people. I was doubious, but he turned out to be correct. They are attractive bright aluminum with aircraft-type holes to make it appear high-tech, minimum weight - quality is high. I am very pleased.
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Chuck
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Ben, just re-read your post - - no, it does not change the shape of the gas pedal - it results in the pedal being higher - The height off the original pedal is adjustable.

[This message has been edited by patalive (edited 03-09-2001).]

Sorry guys, but if you are at the limit of tire adhesion, you WILL STILL get more braking from downshifting....

Now, I agree with Jack in that one of the reasons of heel-toe is to match engine revs so as to remove the stress of the downshift from the engine. This allows you to be in the proper gear when exiting the corner.

But, once you release the clutch, the cars intertial energy is being burned up by the drive-train as well as the brakes.

How can I put it simply?

It is a simple law of energy transference. The car traveling has a certain amount of intertial energy. If you are threshold braking you are transferring that intertial energy into heat with the brakes (and perhaps some fear behind the wheel )

If you use the engine braking, you are removing some of the intertial energy that would have to be absorbed by the brakes and ultimately the tires back into the engine. That is energy that does not get transferred to the adhesion coefficient of the tires.

Why do I believe this? LOTS of laps on the track made me a believer. I brake a LOT later going into turn 5 a Road America if I use engine braking...

Still not convinced? I'll see you at the track

FWIW, I barely passed physics so I tried the patience of a number of people trying to bend my rather besotted mind around this and only believed it after experiencing it.

Could I be wrong? Sure! Maybe I threshold brake better when I am downshifting... ...but I doubt it. It's a lot easier to threshold brake when you aren't double-clutch down-shifting at the same time!



[This message has been edited by cstreit (edited 03-09-2001).]

But a follow up note to some other posts I read. You aren't attempting to brake by using the clutch, but rather, once the clutch is engaged by letting the engine compression eat up energy.

THere really isn't any point to doing this on the street except to impress chicks, brake pads are a lot cheaper than clutch kits

...and to agree with one other guy, after my Nth Guiness tonight, I better get off this soapbox before I really do hurt myself...

[This message has been edited by cstreit (edited 03-09-2001).]

I always enjoy reading The correct heel and toe methods from all the former F1 and Indy drivers here. I think it might take more then a few DE courses to be giving advice, No? Michael Schumacher, where are you?

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8 9 9 1 1, The last of the line.

Originally posted by cstreit:
Sorry guys, but if you are at the limit of tire adhesion, you WILL STILL get more braking from downshifting....

[This message has been edited by cstreit (edited 03-09-2001).]

How?? The limiting factor in slowing a car down will be the grip from the tyres. If you are at the limits of the grip then that is it unless you have a parachute to deploy.

The SOLE PURPOSE of heel and toe is to match revs on downshift. Rev matching is desirable because it results longer engine and trans life as well as making the whole process smoother so no jerks to upset the attitude of the car when you are braking at the limit on the track.

Engine braking is a relic from the early days of motoring when you had gigantic heavy cars with feeble bake systems. The only use for them now would be when descending long mountain roads at a moderate pace where prolonged use of the brake will result in fade.

Think about it, brakes can slow a car MUCH better than the engine so at max braking while in gear, the brakes have to do double duty by slowing the car and the engine down. That is why when car mags do brake tests from 60 or 80 mph, the clutch pedal is fully depressed as this method gets the shortest stopping distance.

Read Patalive's description how to on h/t as it sums the procedure up perfectly. It's done just before turn in and you are on the gas the moment it's complete (whether feathering it or flooring it). If you are still on the brakes after the downshift is done then it's not being done correctly- either too soon or you are entering the corner too fast which results in lower corner speed, lower exit speed and higher lap times.