Do you match revs on the upshift?

holtjv · 12-21-2006, 10:05 AM

I confess this notion is new to me-I've matched (or tried to) on the downshift because it seems the stress on the clutch is, or can be, greater.

Do you match going up, or just down?

And a general rev matching question (from a rookie, be nice) is this: how do you get it close, even if you know the target rpm? I've got some amount of unpredictable variability on the up rev from my foot, then also I have the unpredictability of the decel mechanism on the way down. And I'm supposing that, unless you time the whole thing just right and the revs are in the 'target zone' as the gear is re-engaging, you're either not doing anything good for the clutch or possibly making it worse?

Thanks--this topic has been nagging me for some time.

pmajka · 12-21-2006, 10:21 AM

match on the downshift. practice, practice practice.

once you get it right, you will be smooth. Took me a year of daily driving to master blip matching and heel toe braking (or toe heel as it seems to me)

MASTER = only you know when you're a little off.

pmajka · 12-21-2006, 10:22 AM

Oh, and a couple hundred RPM is better than being a 1000 rpm off.

dd74 · 12-21-2006, 10:25 AM

I try on the downshift. Have done it on the upshift, but only on the track. As said, "practice, practice, practice."

911pcars · 12-21-2006, 11:37 AM

Upshift is easy - the engine speed normally drops anyway. Shift into gear at the same rpm you would be in that gear.

Downshifting requires a different technique. Scan the archives please as this has been discussed at length.

Sherwood

rmurph · rmurph's Garage

As said "practice, practice, practice" on the downshift. I also will blip the throttle on upshifts to match revs, especially when the engine and trans are cold. And sometimes during leisure drives when I am not under hard acceleration. Allows for a very smooth shift to the next higher gear.

holtjv · 12-21-2006, 12:47 PM

Quote:

Originally posted by 911pcars
Upshift is easy - the engine speed normally drops anyway. Shift into gear at the same rpm you would be in that gear.

Downshifting requires a different technique. Scan the archives please as this has been discussed at length.

Sherwood

As to your 'upshift is easy', if engine speed drops to 2k, and I'm upshifting at 65mph, I suspect my gear will be engaging at higher than 2k rpm, no? And I'm not talking clutchless shifting.

I obviously looked through search results--however like most questions with nuance (not 'how to drop an engine' or 'HELP! WHERE'S MY DIPSTICK!!"), my questions were not answered.

My new year's resolution is not to answer questions with, "do a search".

Zeke · 12-21-2006, 01:12 PM

High compression, light flywheel motors are hard to drive smoothly on the street at street speeds. Matching revs on the upshift is necessary to keep from knocking your passenger's head on the windshield each time you let out the clutch. I know too many people who do this and are not smooth in a normal car, but one doesn't feel it as much as one would with the high compression light setup. Decel valves help a lot, too, in keeping the revs from falling off too fast on an upshift.

Watch your passenger's head as you go through the gears. If you're smooth, they won't as much as move. You have to have revs on or very near the trans speed on any shift. Your clutch will love you and your passengers will love you even more.

911pcars · 12-21-2006, 01:22 PM

"As to your 'upshift is easy', if engine speed drops to 2k, and I'm upshifting at 65mph, I suspect my gear will be engaging at higher than 2k rpm, no? And I'm not talking clutchless shifting."

Your foot controls engine speed. For example, when shifting from 3d to 4th the engine speed will drop. Shift and engage the clutch before the rpms drop below what it would be in the next higher gear. If needed, use your foot to adjust the engine speed.

As for downshifting, merely blipping the throttle before shifting into gear isn't the complete answer. You must double-clutch in order to match all rotating shaft speeds - no other way around it, with or without synchromesh.

Sorry. The search avoids duplicating several pages of the same discussion. If you have more questions after that, be happy to describe more.

Sherwood

dfink · 12-21-2006, 01:27 PM

Maybe someone said this already but you aren't usually braking when doing an upshift so coordination level is maybe a little less than the downshift while braking. But to answer your question I don't try to speed match but I don't think it is the problem a downshift is.

dd74 · 12-21-2006, 01:32 PM

Quote:

Originally posted by dfink
Maybe someone said this already but you aren't usually braking when doing an upshift so coordination level is maybe a little less than the downshift while braking. But to answer your question I don't try to speed match but I don't think it is the problem a downshift is.

Yes, doing this while accelerating is never nearly as difficult. While braking, four things are happening: 1) steering; 2) braking; 3) shifting and 4) blipping.

No easy task for the novice.

TargaFlorio · 12-21-2006, 02:04 PM

I do it out of habit. I think it helps a bit on the first to 2nd gear shift on the 901 transmission.

I always double clutch on downshifts, even when I have to heel 'n toe brake.

Get yourself a pair of decent shoes (like Piloti), they'll make it easier.

Cheers,
n.
_
http:nicolashunziker.com

T77911S · 12-22-2006, 06:09 AM

i may go from 3rd to 5th or 2nd to 4th or 5th to 2nd both up and down. my tranny is too slopppy to try and hit every gear on the downshift, plus i dont shift it fast and i dont want to cramb it into gear. to 5th-4th-3rd...i may pass the speed for each gear before i have time to get into that gear. 5th to 3rd, 4th-2nd, sure. i usually slip it into 1st just before i stop.

dweymer · dweymer's Garage

I never tried until I hot lapped with a pro driver in a 2004 911 "s".
Even under full acceleration my head did not move much at all forward during the shifts, it was amazing to me the difference.

rick-l · 12-22-2006, 06:51 AM

What???? you sit and wait and let friction slow the engine down on the track??? Why not let the clutch slip a little and convert the energy stored in the spinning mass into acceleration? It slows down real fast.

Gunter · Gunter's Garage

Apples and oranges!
Track-driving is different from street-driving.
For a transmission with good syncros, and a properly adjusted clutch, "double-clutching" is not necessary, it just wears out the Shifter mechanism, PP, release bearing, fork and cable 3 times faster.

When on the street, "double clutching" is just a show-off for Wannabe-Race-Drivers.
You see them all the time buzzing around with loud mufflers doing the macho-thing: vroommm, vrooomm..............

"Gee I look good revving between shifts"

Adjust your clutch properly, shift normally and don't rip through the gears, especially with a 915.

In any of the Porsche manuals for street cars, there is no mention of the necessity for RPM-matching.

O.K. go ahead and look cool by working the pedals.

911pcars · 12-22-2006, 11:35 AM

"For a transmission with good syncros, and a properly adjusted clutch, "double-clutching" is not necessary, it just wears out the Shifter mechanism, PP, release bearing, fork and cable 3 times faster."

Gunter,
I agree. Double-clutching is not necessary, just like reving to redline isn't necessary. You do it for a specific purpose. Otherwise, I must respectfully disagree. Which of the above items would anyone like to repair/replace first? I'd guess it wouldn't be the gearbox.

Wear on the shift housing is negligible (I've seen plenty). In addition, since there is less speed differential between clutch disk and flywheel during a DC downshift, there is less friction produced. Less friction = less wear (clutch facing and flywheel surface).

I'll grant you there's some wear on the other parts since they're used more, but I'd rather rebuild the shifter, the pedal assy. or replace the clutch assembly before rebuilding the gearbox. Does your second gear give you any problems yet? If not, good. However, plenty of others have a second gear issue..... despite their pristine throwout bearings.

As for PAG's lack of a recommendation; I don't think they're too interested in requiring potential customers to double-clutch as a condition for purchasing their product. The manner in which one uses or abuses their newly-purchased product is beyond the scope of most manufacturer's realm of control. That's why they also make a ton of $$ with departments called "Service" and "Body & Paint".

What's cool is not necessarily making excess noises or drawing attention to yourself, but being able to drive a car smoothly and efficiently - fast or slow. It's easier if there's just have one method for both situations.

Sherwood

masraum · 12:39 PM

Quote:

Originally posted by holtjv
As to your 'upshift is easy', if engine speed drops to 2k, and I'm upshifting at 65mph, I suspect my gear will be engaging at higher than 2k rpm, no?

Then you are shifting too slow. You should be able to move the shifter to the correct gear and the clutch should be on the way out in the time it takes your car to drop the required rpm for the next gear.

At what rpm are you upshifting? Once the engine is warm I'd expect you to be shifting somewhere between 3500 and 5500 with the occasional burst above that. The higher you rev the more the rpms will drop so you should have more time, but at lower rpms you should still be able to manage.

masraum · 12-22-2006, 12:41 PM

Oh, and to your other question, of getting the revs right when you are downshifting. With enough practice you'll be able to do it instinctively. The key isn't watching the tach closely, the key is concentrating on how far and how long you blip the throttle.

holtjv · 12-22-2006, 01:44 PM

Quote:

Originally posted by 911pcars
"For a transmission with good syncros, and a properly adjusted clutch, "double-clutching" is not necessary, it just wears out the Shifter mechanism, PP, release bearing, fork and cable 3 times faster."

Gunter,
I agree. Double-clutching is not necessary, just like reving to redline isn't necessary. You do it for a specific purpose. Otherwise, I must respectfully disagree. Which of the above items would anyone like to repair/replace first? I'd guess it wouldn't be the gearbox.

Wear on the shift housing is negligible (I've seen plenty). In addition, since there is less speed differential between clutch disk and flywheel during a DC downshift, there is less friction produced. Less friction = less wear (clutch facing and flywheel surface).

I'll grant you there's some wear on the other parts since they're used more, but I'd rather rebuild the shifter, the pedal assy. or replace the clutch assembly before rebuilding the gearbox. Does your second gear give you any problems yet? If not, good. However, plenty of others have a second gear issue..... despite their pristine throwout bearings.

As for PAG's lack of a recommendation; I don't think they're too interested in requiring potential customers to double-clutch as a condition for purchasing their product. The manner in which one uses or abuses their newly-purchased product is beyond the scope of most manufacturer's realm of control. That's why they also make a ton of $$ with departments called "Service" and "Body & Paint".

What's cool is not necessarily making excess noises or drawing attention to yourself, but being able to drive a car smoothly and efficiently - fast or slow. It's easier if there's just have one method for both situations.

Thanks for all the good advice..Sherwood, I've officially commenced my double-clutching career. Pretty damn slow, for now.

As to upshifting too slowly, I'm sure I do--while 2d isn't giving me any trouble yet, it is balky when cold, so shifting is slower. Higher gears are pretty fast for me.

Jack
Sherwood