Question:
What's the difference between:

A)
1. depress clutch
2. blip gas
3. downshift
4. release clutch/press gas

B)
1. depress clutch
2. shift to neutral
3. release clutch
4. blip
5. depress clutch
6. downshift
7. release clutch/press gas

I've seen people refer to "A" as double clutching, but... you're not REALLY double clutching, are you? Are there any significant differences between the two? I would think that "A" can potentially cause more wear on your clutch/transmission.


Part two - I've asked this elsewhere on the forum without a clear answer. My 1-2 shift is much more notchy and significantly less smoother than any other shifts. I've read that it's a characteristic of a 997 and nothing can reallly be done. Is this really true?

Thanks!

 

"A" is not double clutching...it is heal toe but steps 2 and 3 are reversed ...you shift, then blip, then release

i think in "B" you missed might have a blip?

with the synchro trannies I don't think you need to double clutch......but I'm not an expert...just what I have been told.

My shifts in my 997.1 are perfect and much better than the boxster. ( I did add a short shifter in the boxster to improve the shifitng which were way too long and loose,)

 

I double clutch - as in B. Maybe I'm the only old school guy out there. 3-2 downshifts are definitely smoother double clutching. But, heel and toe downshifting while double clutch downshifting is really an art. I mostly slow the car downshifting without using the brakes. Using the brakes after coasting down. Obviously not in the context of real hard driving - just love to hear the engine rev on the way down.

The syncros in 2nd are always the notchiest. I've felt this in most every manual car I've owned, it's not atypical. You can't do anything about it. I'm not sure if people have really worn out the synchro in 2nd gear. Haven't read about people replacing trannies very often. It will shift better when warm and if you learn to take 1st up a little higher and then wait just the right amount of time before dropping it into 2nd. I guess if the condition is really bad and you have a lot of miles, the synchro could be in bad shape, but I haven't read any instances of toasted synchros. Perhaps others will share that experience. The car is also balky going into 1st, especially when cold. Also happened to me in other manual cars. The 997 is a bit stiffer than sum, but it's probably not the worst out there.
Oh, a short shift kit will most certainly make the notchy situation worse.

 

Double clutching is mainly for older non synchro transmissions. A) is close to double clutching but is simply referred to as rev matching (which is part of double clutching).

 

I find that sometimes double clutching, especially while upshifting in the lower gears, give the engine just the right time to rev down to speed match the next gear, providing a smother transition.

 

I heel-toe, but just go directly to the gear I'll ultimately be in instead of going through all the gears.

 

I consider "B" to be double clutching. When I first learned to drive a manual, it was an old truck and "B" was the only way to downshift without making a noise similar to dropping silverware into your garbage disposal. Now it is second nature to double clutch/rev match. Have not noticed the 1-2 upshift to be problematic except on my '98 BMW 540i. My 996 and 997.2 gear boxes have been perfect!

 

Thanks for all the great info guys.

So this ultimately begs the question, why double clutch at all (on cars with synchros) when you can heel-toe shift in less steps? Seems like it doesn't provide any advantages.

Bummed to hear that a short shifter makes the notchiness worse... had been considering installing one

 

When doing a reltively extreme ( e.g. ending up with >5000 rpm in when downshifting to 2nd) downshift, I always double clutch ( without thinking about it). Sure, you can do it with out double clutching but you will put more wear on the synchros. Even a simple rev match helps, though, and also reduce synchro wear. Any quick shift ( up or down) increases wear.

 

Wow, a bunch of old school guys here. I have never had to double clutch, and rev match (heel toe) on every down shift (track or street). I couldn't imagine how much it would slow me down to have to double clutch on the track. I am full throttle, then heavy on the brakes and let off coming into the corner. I think the same thing every time under braking 10, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1. In between there I will drop down to the necessary gear with rev matching.

 

As long as the transmission has synchros (and all recent automotive transmissions do), it isn't necessary to double clutch.

That said, every time you down shift and don't double clutch, you are putting wear on the synchros---and also putting the particles of the worn synchros into the transmission fluid -- which wears out the bearings, etc.

This just translates to money you will spend on repairs.

Under normal circumstances, I always double clutch.

However:
1. Don't use your clutch to slow the car. That is, as you slow, just use the engine vacuum and brakes until you get to the speed you want, then downshift. (or just go to neutral as you reach a stop) Down shifting through each gear (double clutching or not) may be entertaining, but puts a lot of wear on an expensive piece of equipment. Don't lug the engine. But if you are slowing to a stop and put the clutch in by the time the engine reaches 1,500 rpm or so -- that's not lugging.

2. There are times when it really isn't necessary to double clutch. Suppose you've been driving on a city street at 35mph in 3rd, the traffic slows and now you're going 20 mph or so. There's not a lot of engine rpm difference -- so double clutching at slow engine speeds (where the engine won't change much from gear to gear) is unnecessary.

Don't use racing techniques as your model for street driving. Race drivers may do things to their cars to gain a tenth of a second that you'd never want to do to your car, but they plan on rebuilding the transmission regularly.

 

I agree. Also real racing car components are designed to last only a few thousand miles with relatively ( considering the use) lightweight components and are being rebuilt very often.

 

Rev Matching isn't just a racing technique, it is also a safer way to drive. Have you ever tried to down shift and in the wet without rev matching, the compression will have your back end all over the place. Nissan now sells there 370Z with a auto rev matching with the manual tranny. Besides rev matching on the street is great practice, and it quickly becomes second nature.

 

The purpose of rev matching is to prevent an abrupt downshift from upsetting the rear of the car in a turn, disrupting traction at the rear. This is especially true w a rear engine car. Downshift before entering the turn and you can prevent most problems here. I find it (matching revs/blipping) difficult to do successfully 100% of the time with the standard, non sport, setting; partly lack of practice and partly a throttle response issue. At this point I feel that the missed rev matches (early or late engagement) cause more clutch/syncro wear then the normal process of downshifting so generally don't bother. One exception is the 3-2 downshift at speed which as has been pointed out creates a large rpm increase. Under those conditions I try to do as Walter does (lol). Downshifting and braking before entering the turn in your porsche is good/mandatory practice and is probably more important than the blip. Btw, if you are going to rev match, driving shoes or the like are a must. Those great old sneaks won't cut it. Too little feel.

 

I found some great videos on you-tube showing double-clutch, heel-toe, rev-matching - these guys were so smooth and fast with dc shifts, very impressive technique - had to watch in slo-mo to even see how they did it. I can't imagine how much practice that would take to get down.

Those guys seemed pretty much of the same opinion - not need for synchro trannys, but less wear and tear if you can master it.