Anir

After reading Ross Bentley's book on driving techniques, I'm now onto Carl Lopez's excellent Skip Barber book. I noticed a paragraph in which he discusses heel-and-toeing his way down through the gears (e.g. instead of going from directly from 5th to 3rd, he goes from 5th to 4th to 3rd).

My question: Is this sort of sequential downshifting necessary, if you double declutch, on our 993s? At DEs, I will often be in 5th at the end of a straight, and heel-and-toe (with double declutching) directly from 5th to 3rd before entering the turn. The revs are matched, so does it matter that I skipped 4th?

Of course, the M3 with SMG-II requires you to row through all the gears, so it's making me wonder.

Thanks.

B-Line

Hey Anir..

Keep reading.. There is a section on Dump Shifting.

To paraphrase or sum up.. It's ok to dump shift (I did it all weekend in skippy's car's )
as long as your blip is big enough to accomodate the skip in gears. So, if you dump from 4th to 1st..HUGE HUGE BLIP,
4th to second Huge Blip,
4th to third, big blip..

So, the size of your blip should match the scale of your dump..
and double clutching is for weenies
(no offense 993RS )

also, Anir keep in mind they are talking about non sycronized gearboxes. They teach double clutching not because it's neccessary to do but because if every student came to skip barber and didn't double clutch, they would constantly have to rebuild the tranny. Your car is syncornized so forget about double clutching..
and also, read the section on double cluthing with Danny Sullivan. He specifically says he has never double clutched any car he has driven ever..
He just uses really big blips..


B-line

Greg Fishman

[quote]Originally posted by Anir:
<strong>
My question: Is this sort of sequential downshifting necessary, if you double declutch, on our 993s? </strong><hr></blockquote>

Anir,
It doesn't really have anything to do with double clutching, which is something you don't need to do in our cars anyway. You can skip gears and it won't affect your car or make a difference in performance, or the life of your tranny. I don't skip gears because it throws my rhythm off, and it is better for me to do the same thing each time I down shift (what if i went to 3rd but meant to go to fourth).
I have been at Road America and going into turn 5 (I think downhill slow left hander) and had to go from 6th to 2nd and went through each gear. I don't think i could have blipped big enough to do a 6th to 2nd shift . You need to get to the track where you can actually practice doing this instead of just reading it in the book , why aren't you going to Sebring with us?

I think B-Line meant to say non-synchronized gear box. Right b-line?
Greg

B-Line

Oops!

Thanks Greg.
post edited.

Me no much into that fancy book learning stuff

B-Line

Oh yeah,

Wanted to add one more thing.

going through the gears 4,3,2, etc. might be helpful if you are engine braking. You can use the clutch to help slow the car between gears..

But, and a BIG BUT.. as we have discussed in some earlier posts, we know that engine braking is bad..
Use the brakes to slow the car, not the engine!
If I remember the term correctly, TCO (Trailing Clutch Oversteer) is not something you want to do.

B-Line

Greg Fishman

[quote]Originally posted by B-Line:
<strong> TCO (Trailing Clutch Oversteer) is not something you want to do.

</strong><hr></blockquote>

I had a student this past summer in a Mid 90's Corvette, he was not bad for a beginner, good, smooth turn-in but as he would begin to accelerate out of the first turn I would feel and hear this loud bang. Happened the next lap. I asked him if he needed new motor mounts as their seemed to be a lot of driveline lash. He said there was no problem with the car, he was just letting off the clutch. (as we exited the turn) We stopped that nonsense real quick. Thankfully we weren't going very fast or we would have experience the TCO you referred to.
Greg

Anir

Thanks, guys! B-line, I haven't reached Sullivan's double de-clutching section yet, but I've also heard from several sources that it's not necessary with modern synchronized gearboxes.

I alternate between double de-clutching and just holding the clutch in during the entire downshift just because I want to learn both techniques. Want to get the basics down.

I wasn't sure if the whole double de-clutching technique might carry more importance if skipping gears, but I see that it's probably irrelevant.

It's pretty easy in my car to match revs when going directly from 5th to 3rd (admittedly takes a pretty good stab of the go pedal), so I'll assume it's OK.

Greg, I'll make Sebring next year - I promise.

DJ

On skipping gears: I very, very, very, rarely skip gears during a downshift. If have have to go 6th to 2nd, I'll go 6-5-4-3-2. The only place I can think of that I skip gears is turn 2 at SoW. Turn one is flat out in 4th, climbing uphill, and the braking area for 2 is uphill, so you can get a lot of braking done in a really short space (115mph downto 40mph). Also, there really is no straight between the exit of 1, and the entrance of 2, so the car is still turning a bit while you're on the brakes. Without really thinking about it, I started skipping from 4th to 2nd. After a few laps, I realized that I was breaking one of my cardinal rules ("don't skip gears"). I tried it both ways (skipping and not-skipping), and for that ONE PARTICULAR CORNER, it was quicker to skip.

Now, therefore, excepting therefrom that one particular corner, on that one particular track, I never skip gears whilst downshifting. I used to skip gears all the time, until that one time that I got the clutch out a leetle-tiny-bit early, when the car was still travelling a leetle-tiny-bit too fast. Over-revved the motor in my dad's 1984 Carrera Cabriolet, and bent all the valves.

Skip the skip. It don't gain you nothin'.