powdrhound

Matt, dumb question. I always thought that rev matching was primarily what preserved your synchros. Also, if you shift into 1st just prior to coming to a full stop, wouldn't bliping the throttle to rev match protect the 1st gear synchro?

mooty

most pro's no longer do that.
just treat syncro as wear tear item.
my tech, REALLY fast. does'nt do it. just replace it. i am too old to learn anything new.

montoya

Yeah, slow and only for old British cars...

mooty

old british cars?
you mean sculptures. DB2 sexy, as long as you dont drive it.

KaiB

Hereya, in the second corner I go from fourth to second very quickly. In all corners of this nature, I perform a double clutch. This occurs for two reasons: I skip third (although you'll see I "feel" the gate) and I shift quicker than the syncros would like me to.

Two blips are necessary in my car - with the 5.5" flywheel the revs drop off so quickly that after I've affected rev matching (with the clutch out) to spin the rings, I have to blip again to insure road speed revs are met.

Difficult to see, but here it is:

GTgears

Watch the master at work...

KaiB

Why - THANK YOU, Matt!

GTgears

Remember, when you are doing your usual rev match, your clutch pedal is to the floor. This means that the only thing your rev is spinning up is the engine/flywheel. Your input shaft and gear stack is disconnected from the rev at this point.

Then, your next step is to push the gear lever into gear, with the clutch pedal still to the floor. What allows you to make that shift and adjusts the speed of the gears for engagement? The synchros.

When you double clutch (declutch as some like to say) the release of the pedal with the shifter in neutral is when you are making the rev stab. What this now does is spin up the input shaft because it is connected to the engine this time. No gear is engaged, but what you are doing is accelerating the loose gear up closer to the same speed as the fixed gear (which is tied to the ring and pinion/road speed). Now since there is less difference in speed between the two parts, the synchros work less (if at all).

Don't try this at home... But let's say that your clutch goes out, like mine did last year. The tines on my pressure plate got tired and wouldn't fully release the clutch. I was pretty much permanently engaged. Didn't have time for a clutch job and just had to keep driving for about a month until I could deal with it.

On every shift, I would just pull it out of gear and rev until I felt it synchronized and then pushed it into gear. On upshifts it is a lot easier if you rev it up a bit before you yank to neutral, but you can shift clutchless up and down if you have do.

Same thing happened to the BGB Cayman at the end of Daytona this year. The TO bearing broke. Last few hours of the race Eversley was driving without any clutch and rev matching every up and down shift from the neutral position with the clutch always engaged.

Asquared

Yup, sorry, was typing on my iPhone while waiting in line and I missed that step. The clutch is released (engaged) when you blip throttle. Matt described it best just above. I usually blip, clutch in, and shift into the lower gear as revs are falling off the peak, but I'm still a newb at this, so I might get better. As I said earlier, it was no where near as hard as I expected it to be, but it was out of necessity as second was grinding pretty bad if I didn't do, so I lost some speed on a few laps until I figured it out.

As for speed, you are typically doing this in a braking zone, so speed is not critical. The biggest problem I had was keeping constant brake pressure, for some reason, this is harder for me when I'm double clutching than when I'm not, but I'm sure that will come with experience. Maybe my new Guards internals will help (Thanks Matt).

This isn't a great video, but you can see my left knee double clutching. I didn't watch the whole thing again, but best place might be at 2:05 as I go into Canada Corner. I go down two gears and you can see my knee go down and back up four times.

tasman

On my S2000 and some times on my mustang I will/did drive without using the clutch for shifting gears. Have not tried it in GT3. In some cars it is very doable. You can kind of feel your way into and out of gear. Kind of cool at times. I guess I never really understood what I was doing until now.

dawgdog

I attended the BMW DE at Pacific Raceways today and asked Bill Bauer (former chief driving instructor for PCA NW) about double clutching. To my amazement he said this is second nature for him and he does it on all his downshifts.

montoya

Thanks for the videos guys! When you see it in action and break it down, it's something that seems doable. I always thought the double clutch downshift was: clutch-neutral-blip-declutch-clutch-shift-declutch, but with a LWFW it's really:clutch-neutral-blip-declutch-clutch-shift-blip-declutch. So other rather than a different rhythm of leg and feet movements its really like stringing two single clutch downshifts together, with one being the shift into neutral. Thanks guys!

KaiB

I had to read this five times, but you've got it!

Timing is everything. If you think about the reason we might want to DC, you'll see that the rev-match in neutral is the trick. Too early, and gear matching does not occur.

The 2d blip may or may not be necessary. In my car (extreme LWFW) it certainly is. In the RSR example above, he was able to be quick enough that most of the time, he was able to accomplish the road speed blip without much effort.

Go borrow a big farm truck with bad brakes, an idle problem, crapped out transmission and slippery clutch and practice up. You'll get good in no time.