gnosis

If your car is set up correctly in terms of balance for the theoretical ideal corner, you will be able to use maximum throttle, so long as your car has enough lateral adhesion to stop you simply drifting sideways until you run out of tarmac on the outside of the turn.

In reality, all corners are different, all surfaces are different, and your tyres have changeable levels of grip according to wear and how you treat them while driving on them. So in most cases being able to use full throttle while going around corners simply means you could do with more horsepower!

This is where creative racing lines and "power exits" come into play. Positioning the car so the driving force from the wheels moves the car in opposition to the natural tendency of the well balanced car to slide sideways. The exteme example is dirt track racing, or rallying. These sliding techniques are used extensively to set up cars on entry and exit to corners.

I always want more horsepower than I can use. This means enough to break traction under acceleration regardless of speed or conditions, and enough to break lateral grip on all four wheels at the same time.

Of course, if I had this much horsepower, I'd want more grip.

And if I had more grip, I'd want even more horsepower.

Clayton

Luis de Prat

Interesting thread. What about hills? Do rallye drivers ever "engine brake" at all? They sure make a heck of a lot of noise coming down hills.

gnosis

In the case of the World Rally Cars that compete in the World Rally Championship (you know, McRae, Kankkunen, Grönholm, Sainz, and that lot) they have sequential gearboxes. They're always in a gear unless their foot is on the clutch, which is seldom.

The presence of sequential gearboxes in most top level categories shows that engine braking isn't a choice of the driver. It's there by default, whenever they don't have their foot on the brake or accelerator. This doesn't mean it's essential to good driving. In fact it means the opposite. It means that it's irrelevant.

Clayton

FSAEracer03

Well, I agree and disagree with you at the same time, lol... yeah, it's irrelevant, but for cars with sequentials, it IS very good and usefull. The Formula SAE cars use sequentials very effectively, as do Formula One and others. IMO they are wonderful for the pure purpose to go faster. But for fun, they'd get damn old on the road to me. For example, if I ever bought an E46 M3, I'd be damn sure to buy a 6-speed over the SMG! But I digress... the only real time a driver with sequential uses the clutch is for starts and stops. Rarely is it ever used. But wow... heel-and-toe?? No, hand-push-forward

Friendan

This may seem like a really dumb or newbie question, but does foot size matter when heel-to-toe braking? I'm 6'5" with size 14's, I've never used the technique but I would sure like to learn. Clayton maybe you can help, you seem to be quite knowledgable!

iloveporsches

Having an overly large foot might make it hard to get the proper position, and having an overly small foot might make it hard to push booth pedals. Other than that I don't think so.

gnosis

I don't think it's a good idea to agree and disagree simultaneously. Engine braking is good and useful for what? It has no value to the mechanics of a sequential gearbox at all. It just happens as a by-product.

If it's not a requirement of drivers in the highest levels of motorsport to use engine braking at their option (since it happens by default with sequential dog boxes and therefore cannot be chosen strategically), what possible use does it have? If it had value, it would designed into the drivetrain so it could be used at the driver's option.

This thread is titled "Driving misconceptions". I maintain that the notion of engine braking being of any use in high performance driving is a misconception. I have yet to see any proof (i.e. physics) that shows otherwise.

On the contrary, myself and others have put forward arguments that it has no value at all, being easily superceded by braking with real brakes. And the fact that the highest categories have gearboxes that do not give you the option proves that engine braking isn't something drivers want or need.

Do it on the street? Sure. But don't try to pass it off as a driver aid.

Is there anyone reading this thread who has decided to adopt engine braking and seen a drop in their lap times? I doubt it. If there is, step up now and explain how you did it.

Clayton

gnosis

Brendan,

There tends to be two popular ways to heel-toe. One is to use your heel for the accelerator while keeping your toes on the brake. The other is to use the left side of your foot for the brake and the right side for the accelerator. It's a matter of personal preference. Do it any way you can to ensure you do it smoothly, and if your pedals don't feel right, change them so they give you better feel. There are aftermarket pedals available that have extensions on them to help with heel-toe action.

I don't have a problem with Porsche pedals, but I have a hell of a time in my friend's Audi trying to find the accelerator. I always end up stabbing the brake at the same time, which wouldn't be nice at all if I was trying to brake on the limit.

Clayton

iloveporsches

The only problem I seem to have with the second method is that it may be too easy to slip your foot off the brake. Hasn't happened to me yet, but I only do it on the street, no auto-x or track driving yet.

mpw

Having only ever driven on the track in my S4, I've been basically forced to learn heel-toe on it. On the street, I prefer to use the second method you mention and roll my foot onto the throttle, this is a lot smoother when I'm not hard on the brakes. On the track though, I find that things are happening so fast that finessing the throttle with the side of my foot isn't possible and it's easier to twist my foot and brake with my toes (the crazy bite of Cobalt VR pads help a lot with this) and stab the throttle with my heel to bring the revs up. I'll agree that the Audi does make it pretty tough and it took me a little while to get (I'm definitely still working on it), modifying my gas pedal helped a ton:



- Matt

gnosis

For anyone that's interested, here's a short video clip of me doing some heel-toe downshifts before a double apex corner. You can't see my feet too well, but you can listen to the shifts. Note that I go from 4th, through 3rd, into 2nd. I could just as easily have skipped 3rd, but I tend to come down all the gears to keep the engine and gearbox revving somewhere near where I need it, rather than having it fall off to idle while I'm braking, which would require a larger stab on the throttle to heel-toe before accelerating. This is the only value I can see in "engine braking", but I wouldn't consider it braking since it does bugger all to slow me down. Besides, I'm hard on the brakes the whole time I'm shifting down anyway.

There's also some "typical" production car racing action a little later in the clip provided for entertainment value :-)

http://members.optusnet.com.au/~clay...tp1998r2r4.asf

Clayton

Friendan

Cool thanks guys...I'll give those methods a shot.

Friendan

Wow nice recovery! That was close..btw what car is that youre driving??
I see what you mean when you keep the revs up like that...

gnosis

It's a Toyota MR2, normally aspirated. Those lumps in front of me are a V6 Mitsubishi Magna (overseas it's a Galant, I think) and an Australian V8 Ford Falcon XR8 (no overseas equivalent).

The category is Australian GT Production, which is basically the same as Group N production car racing worldwide.

By the way, there was a Porsche 911 RSCS right up my butt while that evasive action was going on. He was catching me to lap me while I was catching them.

The 911s would take about 8 laps of a typical circuit to lap cars in my class. They normally went past in a lead pack containing two or three Porsches, a Ferrari 355, and a Dodge Viper, exchanging paint with each other while they did it. It was good advice to always watch your mirrors every 7 laps or so!

Clayton

FSAEracer03

Clayton, I'm not trying to **** you off at all, but you seem to really get agitated by disagreement! Do you really think that Mario Andretti, one of the greatest driver's this world has seen, doesn't know what he's talking about? When he says that he feels the car is more stable that he doesn't know what he's talking about, or when Carroll Smith says that while he doesn't prefer it, it is just one of those things that comes down to preference... that he doesn't know the physics behind it?? You can brake just as effectively with both methods... you have shown zero proof as well... why? There is none! You maintain that is shouldn't be used, I mantain that it sure as hell can be used but is a preferencial subject. Why does that make you so mad?

That being said, nice video clip... that near miss was almost as if it was set in slow-motion! Good footage, Clay

Brendon, if it's of any use, I were a size 12 myself... it's a non-issue. Foot size only becomes a hasstle when the pedals are too closely spaced (I'm recalling memories of a Spec Miata that I should never have fit into, lol).