rev matching

[Porsche]

Originally Posted by Eurasianman

Hmm... I could have sworn I tried that before. In fact, one time, I somehow shifted into 3rd going too fast (Coming out of 4th and was trying to shift into 5th... don't ask). Got zero grind.... but the rear wheels locked up and left a nice cloud of tire smoke/marks.

"Here lies @Eurasianman. He went for fifth … and grabbed third instead. May he rest in peace."

It's possible that you over-revved your engine with a mechanical over-rev. Do you know how fast you were going, or what your rpms were in 4th gear when you went to shift to 5th and inadvertently grabbed 3rd instead?

For example, if you are at 6200 in 4th (88.6 mph) and then mistakenly change down to 3rd, that would zing your engine up to 7876 rpm. That could bend things internally.

Glad you're still with us. Now, try to never do that again.

[Porsche]

Originally Posted by mitosis

I've always been under the impression that if your car is currently in neutral and still travelling forward that you can throw it into whatever gear you want...

Yes, you can; however, some gearboxes such as my S2000, for instance, dislike skip-shifting when shifting up. This can lead to early repairs. I would guess that most gearboxes can tolerate it without undue wear leading to trouble. Waiting a bit longer in neutral, mid shift, will allow the two shafts within the gearbox to be closer in speed and thus minimize wear when skip-shifting.

some gears might need a bit of rev matching to get past the lockout but other than that I thought choosing your proper gear was fair game among all choices and part of the challenge of driving a stick.

What "lockout?"

The only lockout I'm aware of on any modern automobile gearbox is the one preventing accidental engagement of reverse gear.

[Eurasianman]

Originally Posted by Porsche

"Here lies @Eurasianman. He went for fifth … and grabbed third instead. May he rest in peace."

It's possible that you over-revved your engine with a mechanical over-rev. Do you know how fast you were going, or what your rpms were in 4th gear when you went to shift to 5th and inadvertently grabbed 3rd instead?

For example, if you are at 6200 in 4th (88.6 mph) and then mistakenly change down to 3rd, that would zing your engine up to 7876 rpm. That could bend things internally.

Glad you're still with us. Now, try to never do that again.

I was going over 80 MPH in 4th when accidentally going into 3rd gear. I had my eyes on the RPM and it just stayed at red line when the rear wheels locked up until I disengaged the clutch real quick.

Trust me, I do not want to ever do that again. That is the second time I have done that in my life. The first time was when I was 17 and was driving my dad's 97 Toyota Tacoma and was going 70 MPH in 4th and shifted into 3rd instead of 5th and left a nice line of tire marks on the road... along with a cloud of smoke

[Porsche]

Originally Posted by Eurasianman

I was going over 80 MPH in 4th when accidentally going into 3rd gear. I had my eyes on the RPM and it just stayed at red line when the rear wheels locked up until I disengaged the clutch real quick.

Okay. You DO understand that the engine rev limiter only works when changing up under power, right? The rev limiter cannot keep your engine from over-revving when changing down and engaging the clutch in either the wrong gear or at too high an rpm.

Others need to understand this even if you already do. It is quite possible to over-rev and BLOW UP AN ENGINE when making a mistake changing down through the gearbox. The rev limiter DOES NOT WORK in this case.

Trust me, I do not want to ever do that again. That is the second time I have done that in my life.

Weelll... that's two strikes now. You know what happens after THREE strikes, right?

[Stryker]

Originally Posted by Dalers08

First off, rev-matching is only used on downshifts not upshifts.

False.

Rev-matching is actually done going both ways...except when you're accelerating the desired effect happens on it's own.

Just saying...

[Lauren]

I admit, I haven't read all the replies in this thread, but here's an article I wrote on Heel and Toeing ten years ago.

Hopefully it will be of some help.

Driving Techniques 2: Heel and Toeing

When driving on-track and equally on the road there are always tips and tricks you can learn. Often mentioned but not always well understood is that of heel and toeing. Before I explain what it is I am going to mention the benefits and the reasons behind it. This technique is aimed at keeping the car on the smoothest possible transition from braking before the corner onto corner entry. It’s main aim is to help maintain the balance of the car whilst simultaneously allowing maximum braking.

What heel and toeing is, is essentially a ‘blip’ of the throttle to match engine revs whilst changing down a gear and braking. All at the same time of course! Sounds difficult, but with a bit of practice, not only do you get round corners more quickly, but you are also much kinder to your car’s gearbox, clutch and engine.

Probably the easiest way to explain it is to take you through a virtual corner. So here I am approaching Redgate at Donington. I’m in 4th gear at around 105mph or so. To take the corner I need to reduce my speed to 60mph and be in 3rd gear. I am still accelerating as I am approaching the corner. At the braking point I put the brakes on very hard to slow down in as short a time as possible. Now, timing is key to doing this well. As my speed drops just below 75mph I push the clutch down and change into 3rd. before I let the clutch up, I roll my right foot (which is still on the brake) and turn it slightly anti-clockwise to ‘blip’ the throttle. This sends the engine revs up and as I let the clutch out the engine speed matches the road speed in that gear. Next I turn-in to the corner and get back on the power easing the throttle on to balance the car for the exit of the corner. Two main advantages here; firstly the car hasn’t been unbalanced by me changing gear and braking. Secondly the net result is that I’m on the power earlier and everything is that much smoother.

So what happens if I don’t heel and toe? Well I enter the braking zone, brake hard, then as the speed drops I change down and as I let the clutch up the engine revs suddenly soar, which in turn unbalances the car as the rear goes light and I have to deal with all this before I turn into the corner!

A year ago at Bentwaters I experimented with not heel and toeing at a tight left hand corner. It was a second gear corner and I found that if I didn’t heel and toe I actually locked the rear wheels as the clutch came up!

So in effect when you heel and toe you are pressing the brake and accelerator at the same time. This is the trickiest bit by far, how to maintain consistent even braking and in the middle of it blip the throttle? As I described earlier, I like to roll the outside of my right foot onto the throttle. This is certainly the way to do it with the most feel. But if you have standard pedals then you may find they are too far apart to do this easily. I have a Sparco pedal set in my car for good reason and that is to put the accelerator and brake closer together so that I can roll my (narrow) feet more easily.

If I’m driving a friend’s car I use the ‘other’ way. Literally use the ball of your feet to press the brake and kick the accelerator with your heel. It’s less easy to keep a constant pressure on the brake doing it this way, but it gives the same results as rolling your foot. It may be less exact but it works just as well.

One of the best things about heel and toeing is that you can practice it every time you drive your car on the road. Please remember though that the first few times you try it make sure no-one is in front of you. Try it at slow speeds on a quiet road. Cruise along in 4th then try the technique going into 3rd. Better still simply sit in your car and look at your right foot on the brake pedal see how you can push the brake and hit the throttle as you do it. Make sure that your foot is in no danger of slipping off the brake. I was practising this a few years ago and tried it approaching a roundabout. I wasn’t going overly fast but my foot slipped right off the brake and I had to get on the brakes pretty quick to stop in time! So be careful!

Lastly, in order to help heel and toeing, think about getting a pedal set. You can buy a funky Sparco Aluminium set for under £20. Make sure it is a ‘bolt on’ set and not one that clamps over the existing pedals. What you need to do is to take the rubbers off the brake and clutch and drill through the remaining metal pedal. Then it’s a matter of bolting the pedal cover to the pedal. Make sure that the brake pedal cover is absolutely secure. You don’t want this to come loose! By law there is supposed to be 50mm between the brake and accelerator. It’s very much up to you if you keep to this. You’re unlikely to get prosecuted if they are closer than this distance and you would be pretty unlucky to fail an MOT because of it.

To heel and toe well and to drive well, you need to have the maximum feel through the pedals as possible. A lot of people drive in trainers and while this may be comfortable, because of the thickness of the sole it literally robs you of feel and feedback through the pedals. Okay the clutch isn’t all that important but the accelerator and brake certainly are. Try to wear as thin soled shoes as possible. Best is of course racing boots as they are designed solely for this purpose. They do cost, but in my opinion they are worth it. Expect to pay around £30 or so for ‘clubman style boots’. FIA approved nomex boots start around £60 plus.

[Porsche]

Originally Posted by Eurasianman

I was going over 80 MPH in 4th when accidentally going into 3rd gear.

BTW, you can be going 83 mph in the BRZ and change down into 3rd gear; that would put you at 7400, redline, in 3rd.

Your experience locking up the wheels is a cautionary tale of WHY one must rev-match when changing down at speed, especially when rapidly engaging the clutch. Fortunately, you did not fly off into the trees. (Or, you failed to mention that part. )

For those who may be wondering how to avoid this problem, here's what I do: When changing up from 4th to 5th, I place strong sideways pressure to the right (as well as forward pressure) against the shift lever from the beginning of the shift. This way the lever will be forced to follow the "dogleg" turn to the right and up and go into 5th, not straight forward into 3rd, which could prove to be a fatal mistake in the wrong circumstances.

[brianhj]

Originally Posted by Sciby

As other people mentioned, double clutching is out of date thanks to modern gearboxes, but for an example of it, you can hear Mr. McQueen double-clutching through this clip:

When you hear it, keep in mind he's putting the clutch in, shifting to neutral, clutch out, blip throttle, clutch in, next gear, clutch out, throttle open. All in under a second.

At 2:06.. What a glorious sound

[chrisl]

Originally Posted by Porsche

For those who may be wondering how to avoid this problem, here's what I do: When changing up from 4th to 5th, I place strong sideways pressure to the right (as well as forward pressure) against the shift lever from the beginning of the shift. This way the lever will be forced to follow the "dogleg" turn to the right and up and go into 5th, not straight forward into 3rd, which could prove to be a fatal mistake in the wrong circumstances.

Ahh, but what if you get a new Corvette or 911, with the 7-speed manual gearbox?

[Porsche]

Originally Posted by chrisl

Ahh, but what if you get a new Corvette or 911, with the 7-speed manual gearbox?

LOL!

I'd be inclined to continue to employ my current method. While it is possible that I might grab 7th instead of 5th, that would be a mere inconvenience, whereas grabbing 3rd can be catastrophic for both man and machine.

I'm always willing to learn something better. What method do you suggest?

In fact, Chris, I'm way ahead of you. I recently sat in a 2014 Corvette Z51 and played with the shift mechanism expressly to explore this very issue. The way the engineers set it up, with the spacing between gates and the spring pressure resisting going into the 7th-Reverse gate, I don't see it being much of a problem. But, of course it's always possible to make a mistake with that extra gate.

Now, in practice I'd be unlikely to need more than the first four gears in the Z51 out on the roads. At 6500 rpm (redline) in 4th, I'm going 145 mph. (5th = 185 mph). I'd just treat it like an old 4-speed box when engaging in "spirited driving," aka go-straight-to-jail.

Those last two gears on the Z51 are staggeringly tall; 6th=0.57:1, and 7th=0.48:1. They're for improved fuel economy of course, not performance, and the car cannot pull redline in those gears. The car's still limited to 185 mph top speed; drag limited, I assume.

Seventh gear is just for leisurely cruising and one would have the time to carefully steer the lever into 7th.

Anyway, we've strayed from the topic.

[Hanni_0176]

Originally Posted by Porsche

LOL!

I'd be inclined to continue to employ my current method. While it is possible that I might grab 7th instead of 5th, that would be a mere inconvenience, whereas grabbing 3rd can be catastrophic for both man and machine.

I'm always willing to learn something better. What method do you suggest?

In fact, Chris, I'm way ahead of you. I recently sat in a 2014 Corvette Z51 and played with the shift mechanism expressly to explore this very issue. The way the engineers set it up, with the spacing between gates and the spring pressure resisting going into the 7th-Reverse gate, I don't see it being much of a problem. But, of course it's always possible to make a mistake with that extra gate.

Now, in practice I'd be unlikely to need more than the first four gears in the Z51 out on the roads. At 6500 rpm (redline) in 4th, I'm going 145 mph. (5th = 185 mph). I'd just treat it like an old 4-speed box when engaging in "spirited driving," aka go-straight-to-jail.

Those last two gears on the Z51 are staggeringly tall; 6th=0.57:1, and 7th=0.48:1. They're for improved fuel economy of course, not performance, and the car cannot pull redline in those gears. The car's still limited to 185 mph top speed; drag limited, I assume.

Seventh gear is just for leisurely cruising and one would have the time to carefully steer the lever into 7th.

Anyway, we've strayed from the topic.

Wow, those are some tall gears. If I could afford one, one of the first things I'd be looking into for it would be shorter gears, lol.

[Porsche]

Originally Posted by Hanni_0176

Wow, those are some tall gears.

Aren't they?

If the Z51 were capable of pulling redline in that tall 7th gear, it would be going 303 mph!

I don't think the GM engineer, whose Z51 loaner I was sitting in at Road America, realized that.

[DrDuquette]

Rev matching is so much easier with a nice loud exhaust. I was having a hell of a time rev matching on my BRZ. Never had a problem on my other cars. Thought something was wrong with me. Then I put the Berk muffler delete dual exhaust on. MAN, was it easy again to blip and rev match and heel toe!!!! So FUN!!!
Speaking of loud exhaust. Anyone want my Berk. It's just not for me. Bay Area pick up.

[qqzj]

Anybody can give a table between gears and rpm's? I read the whole discussion and I am still at a loss. (suppose we downshift by 1 or 2 gear each time).