Hello folks,

I have a 2004 WRX with a few mods and have about 6800 miles on the car. I have a question about rev matching and double clutching. When I first started to try and refine my driving technique, I wanted to smooth out the down shifts, so I read up about rev matching. I quickly realized that the best way under hard driving would be to heel toe it, but its hard to practice and since I'm about 5'8 I think I would have to put the seat real close to do it...not too good for daily driving. So I adopted the following technique for down shifting into turns....say a highway off ramp. It goes

1) Brake
2)Clutch in.
3)Down shift (select gear)
4)Hit the throttle to rev match.
5)Let the clutch out...quickly.

I can do this fairly quickly with what seems like a flurry of feet movememt....lol. I can do it so the car doesn't jerk, or anything. Although when I was learning this I let the clutch out fast once when the rpms were too low and it was not pleasant...plus it was on the way to work...So I was happy with this until I read about double clutching. So I've been practicing that with the sequence:

1)Brake
2)Clutch in.
3)Neutral
4)clutch out
5)blip gas
6)clutch in
7) Select gear (down shift)
8)rev match
9) clutch out.

When I do this quickly it results in a vroom VROOOM from my Greddy Exhaust and about the same feeling as when I use the first technique...no jerking....you really can't even feel the shift anywhere in the car, almost like you put it in neutral. I still screw this up sometimes, but it is almost routine now. I know double clutching is good for the synchros and I can feel that, but is this whole procedure worth it? I mean I can just rev match with clutch in initially a lot faster. The friends I have who drive stick aren't exactly performance minded...so they have no idea about any of it. So my question is...is the first method OK? Is one better than the other? Is it bad to rev it with clutch in? Sometimes I really have to "goose" it to do this whole thing smoothly. Thanks for your input and I look forward to discussing this with the group.

just rev match, double clutching is pointless unless you're on the track

I was wondering the same thing. I did the reverse though; when I got my rex I learned how to double clutch, heal toe, and blip rev match all at the same time. Then I got lazy and started just heal toe and rev matching. Like you said, I can tell the difference getting the car in gear (much smoother with double clutch). But I also don't like kicking my clutch that much and I'm sorta lazy. So now I double clutch only if there's a huge difference in my down shift (like if I have to slow down a lot quickly, from 4th to 2nd, I'll double it). Also, I double clutch getting into first because other wise I usually grind.

just rev match, double clutching is pointless unless you're on the track

That doesn't make sense to me. Double clutching is slower (it has to be, it takes more time to hit the clutch twice than it does to hit it once), and the reason racers do it is because a lot of them don't have syncros so they have to double clutch in order to get the car in gear.

when you're in the middle of a turn it can help you. There's a technical thread somewhere on here about it. The only time double clutching makes sense on the street is when reverse is being a *****

when you're in the middle of a turn it can help you. There's a technical thread somewhere on here about it. The only time double clutching makes sense on the street is when reverse is being a *****


When you're in the middle of a turn, rev matching and toe heeling can help. Noone's ever given me a good explanation for why they think double clutching is faster in a car with syncros(in a turn or not, either way it's slower...). The double clutching is to get the flywheel and tranny spinning the same speed so it slips into gear (neccesary if you have a dog box). But if you can get it into gear without double clutching, it MUST be faster without the double clutch. Double clutching can only possibly limit some wear on the syncros (and like you said, make it so it's possible to get into that damned reverse gear).

Double clutching is more of a syncro issue than a speed issue. Double clutching is required on race trannys that have no syncros in order to allow the tranny input shaft to catch up to the engine rpm (which revving with just the clutch in won't do.) Even if you have syncros, double clutching will save wear on those syncros, which is a big concern with our sh1tty grind prone Subaru units. Double clutching done right can be just as fast as no double clutching. As proof, watch the footbox video on Gary Sheehan's website. You try and tell me that you can do a standard rev match any faster than that.

-Chris

http://www.teamsmr.com/html/videos.html it's the second vid down.

Double clutching is more of a syncro issue than a speed issue. Double clutching is required on race trannys that have no syncros in order to allow the tranny input shaft to catch up to the engine rpm (which revving with just the clutch in won't do.) Even if you have syncros, double clutching will save wear on those syncros, which is a big concern with our sh1tty grind prone Subaru units. Double clutching done right can be just as fast as no double clutching. As proof, watch the footbox video on Gary Sheehan's website. You try and tell me that you can do a standard rev match any faster than that.

-Chris

http://www.teamsmr.com/html/videos.html it's the second vid down.


I agree completely...I wasn't trying to say I can rev match w/o double clutching faster than everyone who double clutches...I was just saying that, for example, Gary Sheehan can probably single clutch rev match faster than he can double clutch. Not much of a difference in time probably, but physics and common sense say that pushing the clutch twice HAS to take a longer time than hitting it once.

Double clutching is more of a syncro issue than a speed issue. Double clutching is required on race trannys that have no syncros in order to allow the tranny input shaft to catch up to the engine rpm (which revving with just the clutch in won't do.) Even if you have syncros, double clutching will save wear on those syncros, which is a big concern with our sh1tty grind prone Subaru units. Double clutching done right can be just as fast as no double clutching. As proof, watch the footbox video on Gary Sheehan's website. You try and tell me that you can do a standard rev match any faster than that.

-Chris

http://www.teamsmr.com/html/videos.html it's the second vid down.
That was nice.....I just do the simple heel toe stuff on the street. No where near skilled enuff to do that. SWEET :D

I agree completely...I wasn't trying to say I can rev match w/o double clutching faster than everyone who double clutches...I was just saying that, for example, Gary Sheehan can probably single clutch rev match faster than he can double clutch. Not much of a difference in time probably, but physics and common sense say that pushing the clutch twice HAS to take a longer time than hitting it once.


Yeah, sorry... I was replying to an earlier post, not yours. I agree that single clutching is always faster than double clutching done by the same person, but the amount of wear you save on the ghetto syncros IMO is worth it. I do it whenever possible. Nuts to the OEM subaru syncros.

-Chris

I agree completely...I wasn't trying to say I can rev match w/o double clutching faster than everyone who double clutches...I was just saying that, for example, Gary Sheehan can probably single clutch rev match faster than he can double clutch. Not much of a difference in time probably, but physics and common sense say that pushing the clutch twice HAS to take a longer time than hitting it once.

Yes, a double-clutch does take longer than a single clutch, but what's the rush? I'm just going to be sitting there waiting for the car to slow down anyway, so why not save some wear on the car?

Gary
Sheehan Motor Racing
www.teamSMR.com

Yes, a double-clutch does take longer than a single clutch, but what's the rush? I'm just going to be sitting there waiting for the car to slow down anyway, so why not save some wear on the car?

Gary
Sheehan Motor Racing
www.teamSMR.com


Good point (of course). Thanks for the response! I never expected to get a reply from someone that knows as much first-hand about this as you!

my t2 cents on this: Double clutching is more necessary in lower gears because the difference in gear ratio is greater. As the gear ratios get closer, (i.e. 5th to 4th or 4th to 3rd shifts) double clutching may not be as necessary because the difference in rotational speed of the gears is less. The decision is really up to the driver's personal preference. I try to always double clutch when going from 1st to reverse or vice versa. I also double clutch to downshift to 2nd. Rev matching onlyl affects engine speed, but double clutching helps to match the speeds of both shafts in the transmission.

the heel toe method on the streets is a bit overkill ya think? if you are just downshifting to slow your car you can revmatch with one foot on the gas and one on the clutch to give you a smooth downshift.

hell toe method is when you want that extra stopping power and you NEED to accellerate out of a turn with absolutely minimal delay. (LIKE AT A TRACK) no need on the streets my friend.

if you understand the basics of a convential manual transmission you will understand double clutching has absolutely NO PURPOSE AT ALL. double clutching IS in-fact necessary on very stout trannys on tractors or heavy duty machinery without syncronizers that you would see in a construction yard. NOT YOUR 05 STI.

I'd submit all of it is a collassal waste of time...neither gets you around a track or to the grocery store any quicker, and as Gary said, you stand a bigger chance of breaking something

Adam

if you understand the basics of a convential manual transmission you will understand double clutching has absolutely NO PURPOSE AT ALL. double clutching IS in-fact necessary on very stout trannys on tractors or heavy duty machinery without syncronizers that you would see in a construction yard. NOT YOUR 05 STI.

Apparently you haven't been PAYING ATTENTION. Go back and read again. Double clutching may not be necessary for sychro gearboxes, but double clutching does make it easier on the sychros. EVEN IN YOUR 05 STI.

By the way, WHY DO YOU YELL TO MAKE YOUR POINT? ;)

I'd submit all of it is a collassal waste of time...neither gets you around a track or to the grocery store any quicker, and as Gary said, you stand a bigger chance of breaking something.

Adam, how can it be a colossal waste of time when you have loads of time in the braking zones? I never feel rushed when double-clutching because there is so much time in braking.

I don't think I ever said there is a bigger chance of breaking something using double-clutching. I looked but couldn't find any reference to that.

Gary
Sheehan Motor Racing
www.teamSMR.com

I misread your post Gary..sorry..it was early ;) I'll have to try it in a WRX next time we are at the track. I suppose it matters what track you are at as well

Adam

Double clutching is mainly used in racing so that the weight balance of the car is not disrupted during a downshift. Slamming into a lower a gear puts more weight on the rear of the car and can cause a loss of control. Double clutching allows the flywheel and drivetrain to spin at the same rpm maintaining the balance of the car.

Double clutching is mainly used in racing so that the weight balance of the car is not disrupted during a downshift.

No, heel-toe is used to keep the car balanced during a downshift. Double-clutching is a technique that can be incorporated into a heel-toe downshift.

Slamming into a lower a gear puts more weight on the rear of the car and can cause a loss of control.

No, slamming into a lower gear without rev-matching (using heel-toe) transfers more weight to the front due to the additional engine braking, whether it's front, rear or awd. This can cause a loss of control if the traction at the driven wheels is exceeded.

Double clutching allows the flywheel and drivetrain to spin at the same rpm maintaining the balance of the car.

No, double-clutching allows the flywheel and input shaft of the drivetrain to spin at the same rpm as the rest of the gears in the transmission, reducing synchro wear or allowing the dogs to line up in a sychro or non-synchro gearbox, respectively. You can maintain balance of the car in a downshift with simple heel-toe. Double-clutching does nothing to maintain balance.

Gary
Sheehan Motor Racing
www.teamSMR.com

Weight transfers to the front of the car when the clutch is depressed, and then transfers to the rear when the clutch is engaged. This will happen regardless of what technique you use. You can control the weight transfer with double clutching and heel toe. Double clutching helps to eliminate the rapid weight transfer to rear wheels, and heel toe can be used to transfer weight to the front wheels.

Weight transfers to the front of the car when the clutch is depressed, and then transfers to the rear when the clutch is engaged. This will happen regardless of what technique you use. You can control the weight transfer with double clutching and heel toe. Double clutching helps to eliminate the rapid weight transfer to rear wheels, and heel toe can be used to transfer weight to the front wheels.

What are you talking about?!

Are you talking about a braking situation? If so, while the clutch is engaged, the driven wheels are doing a very small fraction of the deceleration of the car due to engine compression, which transfers weight to the front of the car (i.e.-nose dives during deceleration). When you depress the clutch, that small portion of the decelerative force from engine compression is removed and a miniscule amount of weight is transferred rearward. If you are in a hard braking situation, this is negligible, since the brakes are doing 99.9% of deceleration and are the sole factor in weight transfer.

The only thing double clutching does is match the transmission input shaft rpm to layshaft rpm.

Where are you getting weight transfer from?

Gary
Sheehan Motor Racing
www.teamSMR.com

Weight transfer comes from slamming gears on a downshift. When you shift without matching revs the car lurches forward and weight is transfered to the rear wheels. You have to agree with this.

Like I said before revmatching or double clutching eliminates the lurch, hench it eliminates most of the weight transfer, thus it is controling weight transfer. I realize that this is not the only reason to revmatch or double clutch, but it is a factor.

I think we are on the same page, but for some reason we aren't seeing eye to eye on this.

Weight transfer comes from slamming gears on a downshift. When you shift without matching revs the car lurches forward and weight is transfered to the rear wheels. You have to agree with this.

AAHHHHH!!! I'm typing this one handed because my other one is busy keeping my head from exploding!

When you slam gears in a downshift without rev matching, the car does not lurch forward, YOU do. The car's sudden deceleration that results from instantaneous engine compression forces a weight transfer to the FRONT. That is why YOU (your body) lurches forward. That's why the tissue box flys off the rear deck and hits you in the head. That's why the nose of your car dips closer to the ground. Weight transfer to the front makes the springs compress. Please, take a minute, breath, and think this through.

Like I said before revmatching or double clutching eliminates the lurch, hench it eliminates most of the weight transfer, thus it is controling weight transfer. I realize that this is not the only reason to revmatch or double clutch, but it is a factor.

REVMATCHING eliminates the sudden engine compression caused by the drivetrain bringing engine rpm up to roadspeed. Double-clutching does not. Understand that double-clutching does not have to involve the gas pedal (i.e.-double-clutching a truck gearbox on an upshift does not use throttle). Double-clutching is a layer that can be used on top of a revmatching technique (like heel-toe braking/downshifting). Double-clutching is not a revmatching technique, but that is what you are implying.

I think we are on the same page, but for some reason we aren't seeing eye to eye on this.

If you stop saying that there is a weight transfer to the rear during any type of deceleration, we will be getting closer to seeing eye to eye ;)

Gary
Sheehan Motor Racing
www.teamSMR.com

wow . . .

If you stop saying that there is a weight transfer to the rear during any type of deceleration, we will be getting closer to seeing eye to eye ;)


I never said that. It seems like I write something and you are responding about something else. I am going to have bail out of this thread...pulls ripcord.

btw no offense to you, but we aren't able to communicate on this for some reason.

I never said that. It seems like I write something and you are responding about something else. I am going to have bail out of this thread...pulls ripcord.

mbquarts, you said it right here...

Weight transfer comes from slamming gears on a downshift. When you shift without matching revs the car lurches forward and weight is transfered to the rear wheels. You have to agree with this.

Don't bail. This is a fun and lighthearted conversation, at least from my side. Let's get to the end.

Gary
Sheehan Motor Racing
www.teamSMR.com

mbquarts seems to have his speakers wired out of phase. All the right noise is coming out of them, but it just doesn't quite sound right :D

I think the confussion in this thread comes from the fact that I was talking about accelerating and Gary was talking about decelerating.

I was talking about accelerating out of a turn, and I think Gary was talking about decelerating into a turn.

I think the confussion in this thread comes from the fact that I was talking about accelerating and Gary was talking about decelerating.

I was talking about accelerating out of a turn, and I think Gary was talking about decelerating into a turn.

Ahhh...in that case, forget about double clutching, rev matching or any of that. That's only for braking. Transfer of weight to the rear is good.

Gary
Sheehan Motor Racing
www.teamSMR.com

I read though this entire thread and I now know way more then I ever wanted about heel-toe and double-clutching. I did a few more searches and found this. Might be a good laugh for those of you who are the real gurus of the technique...

Warning: Fast and the Furious references up ahead!

http://www.automotiveforums.com/t116979.html