gnosis

I'm not agitated. I just don't believe you. I am a little frustrated that you're not seeing the light, though!

The day I see someone beat me with engine braking, I'll adopt it. Just like I adopted left foot braking as soon as I saw it improve my lap times. I'm open to new ideas, but this one isn't flying as far as I can see. Feel free to prove your position, though. I'm all ears.

Mario Andretti only won the World F1 Championship because he had the first ground effects car. If he stopped all this engine braking nonsense, maybe he would have won earlier!

That comment should get a few people angry hehe

You know what? It felt like slow motion while it was happening too. I had ample time to decide where I was going to go, have a good look at the dummies in front, think about what was going on behind me, etc. It's a strange feeling, but it tends to happen in situations like that.

Clayton

FSAEracer03

It's true, I've been in plenty of near misses on the road that did that... and a few other times in my life as well. Adrenaline is a wonderful thing

I'm not trying to "beat you" with engine breaking or even say such-and-such is better... it's preference.

That's an interesting opinion you have of Andretti there! So the fact that he's the only driver to win the Daytona 500, Indy 500, plus 1 CART, 4 IRL and a Formula One world title doesn't make him a decent enough driver to win the F1 chamionship with skill?? The fact that he was one of only 3 drivers to win races on paved ovals, road courses and dirt tracks in one season doesn't kinda show why he's argued to be the best of the best, easily up there with Fangio, Senna and Schumacher, if not above?? He was a driver of Formula 5000, Can-Am (considered to be the wildest racecars of all time) and the numerous others mentioned above, and more. By the way, his Lotus 79 wasn't the first ground-effects car, it's predescesor was, the 78.

...do you have any clips from the 968?? I'm anxious to see that thing in action

Rich Sandor

You're nuts to even consider putting Andretti next to, let alone above, Senna or Schumacher.

gnosis

Andretti above Schumacher? No comment.

<edit: removed my remarks about Senna because I really don't want to start a "Senna is God" retribution flame war>

No clips from the 968 since I don't have a place to mount a camera. Maybe once I put a rollbar in it later this year.

Interestingly, the MR2 in Group N spec did identical lap times to the 968 in road going spec. Of course, do the same mods to the 968 and it'll go about 6 seconds a lap faster again.

We're kinda drifting off topic here. Where's Z-Man when we need his guidance?

Clayton

M758

Clayton,
Racing a 944-spec car I have also had few close encounters with spinning cars and just as you said things seem to happen much more slowly that they might appear. It always seems like I can watch the car spining in slow motion and this gives me time to pick my spot and get around without effort. I have only had 1 instance where a car surpised me when it spun. Every other time I was able to see it moving and felt I had time to react to avoid it. In this one case however the car spun and I reacted. Then I felt like I did not react enough and had to make VERY quick move avoid. It was really the only time I have been spooked when a car lost it in front of me. For some reason I did not have the "ample time" that you spoke of and that I typically have. It could have been because the car spun a distance in front me rather than as a I car I was following. I also had another directly in front that I was looking to pass when we came upon the spun car.

Z-man

Hehe...I take a night off from rennlist to watch a movie with my wife, and look what happens!!
I suppose your "Other Side of the Coin" quote is your 'proof' that Andretti and Smith use engine braking. Weak proof, at best, IMHO. Besides, for every Andretti/Smith quote you have, I can show you 5 quotes that counter that opinion.
1. Maybe the Andrettis and Carroll Smiths can use engine braking effectively, but: they are professionals, and they have unlimited resources (read: lots of dollars). At your level and mine, engine braking just complicates things, and costs us unnecessary $$. So, NO: WE (ie non-pros) CANNOT effectively use both methods. You know that jerky motion you get with you downshift without a heel-and-toe blip? Well, THAT'S NOT AN EFFECTIVE METHOD!

2. We have shown you proof about this! (Just read the last, oh, 4-5 pages of proof!) You just don't accept our arguments as fact. Again, let me point out to you that you have NO track experience: ZERO, ZIP NADDA! Others that have added to this thread have varied degrees of track driving. What you read, and what others have been telling you about track, and what you have formulated in your mind to be the best braking technique is simply not correct! Things in theory can only go so far. In practise, it is often a different story.

3. Remember, much of these theories bear no account for real world applications. Some examples: Is my wallet big enough to pay for a new clutch and tranny every season? Am I expert enough to balance the right amount of brake pedal braking AND engine braking to get around a corner? Am I consistent enough to apply the same amount of braking force corner after corner, lap after lap? The answer for all of us here is a resounding NO! Otherwise, we'd be running with Schumacher and company, and not spending time here! I'm lucky if I can get consistency with just using the brake pedal to slow down: adding the engine braking effect just squares the opportunities for inconsistency!

Kevin: you seem to be an intelligent guy. You're interest in motorsport is great. BUT: you really should listen to what's being said here. So far, no one but you, your text books, and your racing friends are on your side of the argument. Everyone else here seems to disagree with you: perhaps you should revisit your beliefs and make some adjustments. Again, I urge you to go back to your racing friends at your shop and revisit the whole concept of engine braking: perhaps you've misunderstood what they were saying.

Ok, I'll get off my soapbox now.
-Z-man.

Z-man

If you have a wide enough a foot, heel and toe could be accomplished by rolling your foot to the rigth while on the brakes with the ball of your foot. My foot is quite narrow, so I bought a pedal extention: this reduced the space between the brake and throttle, and allowed for easier rolling of the foot to blip the throttle.

I am not a big fan of the 'other' heel-toe method, where the toes are on the brakes and the heel is on the throttle: I find using the ball of your foot gives you more consistent, stable pressure on the brake pedal. I'd rather have consistent pressure on the brakes than on the throttle: if your toes are on the brakes, it is easier for you to slip off the brake pedal all together! With my method, if you don't blip effectively, you may over-rev or under-rev your engine, and the downshift won't be as smooth, but you'll still have plenty of braking pressure.

Hope this helps,
-Z-man.

Oddjob

Someone please stop this madness.

Clayton and others have a lot more patience than I would trying to explain basic logic.

FSAEracer03, are you sure you understand your own quote on Mario? Is he really talking about down shifting to use the engine to help brake in the braking zone? The topic is discussing down shifting through each gear instead of skipping gears on a downshift. What kind of cars/racing is he referring to? There is a big difference between Mini Coopers and Formula 1. Lets stick with what we know, modern sports/GT cars.

Some drivers prefer going through each gear and letting the clutch out (engaging each gear) because they feel it is a smoother transition than doing a straight multi-gear downshift. For example, turn 5 at Road America. Depending on what type of car you have, it can be a 5th to 2nd gear down shift. Some guys will go into the brake zone about 130mph in 5th (for a 944T), get on the brakes bring the speed down, push in the clutch, shift from 5th to 2nd, let the clutch out (heel/toe), finish braking and turn in. Because you are going from 5th to 2nd, you have to match the revs pretty good on the heel/toe or you either get a big over-rev or chirp the rear tires when you let the clutch out.

To avoid that, some drivers prefer to down shift through each gear. I’m not talking about just running the stick through the H pattern going from 5 to 2, but to actually down shift into each gear, letting the clutch out and engaging 5-4, 4-3, 3-2. By only dropping one gear at a time, it is much easier to match the revs and you are less likely to over-rev the motor, or chirp the rear tires (which makes the back end unstable). All this down shifting is done under full brakes by heel/toe, and is a lot of very skilled footwork. This is not using the engine to slow the car at all, its done solely to maintain engine/transmission speeds so the shift transitions are smooth and do not unsettle the car.

Another problem this technique avoids is damage to the clutch. If in the same example, you come into the brake zone, hit the brakes and immediately push in the clutch and shift into 2nd (even keeping the clutch in), you can destroy the clutch. Because the clutch disc itself just went from 5000rpm to about 13000rpm, and it can and probably will fly apart. I’ve seen inexperienced drivers do exactly this to 2 different 944 series cars.

If your rear end is so under-braked that your car can even remotely benefit by engine braking: get new brakes, change your rear brake bias proportioning valve, or buy a better car for the track. No Porsches have these problems. However, I did have a student at a track/DE event with a 67 Mustang that had original brakes (rear drum brakes and little tiny cray fish claw sized calipers on the front). That car actually did benefit from engine braking for two reasons, the brakes were terrible, and it had a huge, junk American V8 (lots of compression and lots of friction).

And if you don’t think compression is a major contributor to engine braking (whatever application): disconnect your ignition coil and hit the starter, how many times does the engine turn over after you disengage the starter? Now pull the spark plugs out and see how freely the engine spins.

Forget the idea of engine braking. It has no place on any racetrack with sports cars and really no point or purpose on the street in modern cars.

Waterguy

This discussion reminds me of the older days of superbike racing (that I read about, not participated in.) Motorcycles have far more forward-back weight transfer than cars do. The 2-stroke superbikes were driven by opening the throttle until the front wheel came of the ground (up to 100-125 mph anyway), then pulling on the front brake handle until the rear wheel just started to come off the ground. In other words, they were using all available traction for both accelerating and braking.

Apparently, when they tried to introduce four stroke superbikes, the riders hated them! The four stroke engines had way more engine braking than the two-strokes, which upset the bike, required traction on the rear wheel during braking and made them much more difficult to ride. You certainly didn't hear them talking about the positive effects of engine braking; their braking was already limited by tire traction.

I think M758 made the point that, with the stock braking set-up a Porsche does not use all available traction for braking. Engine braking can probably help a tiny bit for a stock car by adding to the rear wheel braking. If you have revised the brake proportioning valve to utilise all the available braking traction (more braking by rear wheels) then it doesn't help.

Z-man

A modest proposal:
Can we shelf the engine braking debate? Most people here agree it's not good practise. Now let's move on to some other misconceptions of performance driving.

Here's one: hand position: while it looks really, really 'cool,' driving with one hand on top of the steering wheel, it is very unstable.

-Zoltan.

PS: For those of you who continue to use the engine for braking, be sure to tell us:
- when your clutch and tranny finally blew
- how must the repairs cost.

-Sorry, couldn't resist one last jab!

mpw

It's also nice if your airbag inflates and you get the back of your hand in your face at 300 mph.

M758

Let me add that the very small effect of engine braking that does occur can act to change the balance and feel of the car. What some call stability. It does not really have much impact on braking distances.

Someone made the point about limited slips having impact on braking. They do and that fact is well documented. They don't reduce stopping distances, but do impact the balance or stability of the car underbraking. This is same type of effect as engine braking.

No. In NO CASE should you ever use the CLUTCH to slow the car down. When you do down shift the engine speed (flywheel speed) should exaclty match that of the rear wheel speed (clutch speed). And difference in speed is taken out at the clutch which is actually very simliar to the brakes with a friction material (clutch disk) and metal rotating disk (flywheel and pressure plate).

Anyway having a mis-match speed will result in greater clutch wear and is not good. Once you have matched speeds and engaged the clutch if you are slowing with no throttle the engine providing minimal drag at the rear wheels and this a force similar to braking.

Persoally I have learned to always have the car in gear and clutch engaged when on the track. This applies for all areas of acceleration, cornering and braking. The only time the clutch is no engaged is during the actual gear change. Elsewhere the cars in gear and any lift off the throttle does provide some engine braking. In many cases where little to no speed loss is requried a slight lift of the throttle is used to adjust the stability of the car. When this is done is very similar to very light brake application.

So my take is that engine should never used to subsitute the brakes, but can be used to influence the balance or stability of the car either by applying more power, reduction of power, or minimal drag effect from lifting.

Chris Prack

I am going to jump in with my 2 cents but only briefly.

I do not claim to be an expert at anything but from my own experience engine brakeing at the track serves no purpose but to beat up on the engine. The brakes will stop the car MUCH more efficiently than the engine ever will, period.

Go out and try to slow your car 60-30 with the brakes and then with the engine and tell me the difference. It won't even be close.

turbo944

Well, I'll chime back in here on a couple of points. Carroll Shelby and Mario Andretti both raced back when brakes were pretty poor and have driven up through times when brakes got much better. I doubt that Mario used engine braking in CART, there wouldn't be enough time to take advantage of the engine braking in a hard stop. Now, in lesser cars that both raced back in the 60s, yes they probably did use engine braking some. If they learned that then, they may have carried the habit over somewhat toward newer stuff, but make sure of this: Get a current quote from them or something that can be dated. I have some racing books that I bought new and have early 70s technique taught in them. A lot hasn't changed in that time, but a lot has. I've not read or heard of anyone advocating engine braking that is teaching in the modern era. Not in Senna's how to race book, not in the Porsche High Performance Driving Handbook, not in Alain Prost's or many of the others that I've read. It's not taught in racing schools (which Mikey went to several of) and I wasn't taught it either. I have seen people telling about using it and mentioning the terrible brakes they had at the time and the need for any extra help they can get.

While the stock Porsche setup may not cause rear wheel lockup, there is a reason why. If you lock the rear tires, especially in a corner, you will spin or get into that situation and have to give up your braking to try and control the car. If setup right, the fronts should lock just before the rears do so that you can modulate to keep the fronts as close to lockup as possible (when you are at maximum braking your tires can be rolling as much as 15% slower than your car is moving). I'm not sure how different that point is between the work on the front and rear wheels, but I'm not sure I'd want to do anything that might exceed that threshold and lock the rear tires first. Rear wheel lockup got to be a big problem on pickup trucks and for several years before they had all wheel ABS, many came with rear wheel ABS as once they got the weight transfer onto the front tires the rear tires were so lightly loaded that they would lock up which increases braking distance and can cause loss of control/spins.

Ken

Another interesting point regarding motorcycles and engine braking is that a recent invention on most race bikes(and some high end street) have what is called a "slipper clutch". Basically, under hard braking/decelleration the clutch "slips" so that the engine braking does not effect the rear wheel. On a motorcycle the problems are magnified because the rear wheel will lockup. The most serious consequence is severe loss of control. Plus a locked wheel provides less braking force. Just more proof that engine braking is not a good tactic on the track as they choose to live without it.