JustinL

It sounds like the goals are to be safe and have fun, not so much on learning new techniques or going fast. That's cool, so just back your brake point up far enough that you aren't dumping the clutch with low RPM while you are heavy on the brakes. Like Peter said, that's when you are going to get yourself in trouble. It's going to be harder on the equipment, slower and more unsettling to the car, but you can mitigate that somewhat by giving yourself more time in the braking zone to get it done and done in a straight line. Make absolutely sure you never dump that clutch after turn-in.

mark kibort

Blip is to not only prepare the engine to match wheel speed in the changed gear, but to also speed up the transmission lay shaft as you pass through neutral. some call this "dipping " the clutch. blipping the throttle while moving through 2 or more gears and not releasing the clutch, has no effect, other than the final resting spot of the RPM as you release the clutch. the synchros spin up the layshaft and the torque tube if you have on like a front engine car would. if you skip gears, as we all talked about on an earlier thread, you pose much higher wear on the synchros as the speed at which the layshaft , clutch discs, etc, will be much higher.

actually, downshifting is a major factor in braking . i was at ACS this past weekend and when i couldnt get my gear selected due to heat on a downshift, it destroyed my braking zone, primarily the trial brake which was a big problem. downshifting on approach has several effects. the diff works for you in turn in and it also has a lot to do with the amount of braking force developed at the rear wheels the engine acts as a sort of ABS system for the rear brakes, even if you dont have it. . at 1:54 you can see the very valuable forces the downshift apply

Greg Phillips

Option A and let the clutch out slowly to minimize the braking effect

Greg

Thundermoose

I don't dip clutch between multiple downshifts so I admittedly beat up on the synchros a bit.

mark kibort

uh oh... then what do you do then? skip gears? the "dipping " comes kind of naturally..especialy when you are hurrying a downshift. it happens so fast that the flywheel never is fullly disengaged , as to always just drag a little on the driveline. this is just enough so that when you blip and put the clutch in, it spins up the driveline as you pass through neutral, AND allows for the synchros do to their job. its a win win.
the control forces of downshifting should never be underestimated. i got a firm reminder when i hit that turn at ACS when i couldnt get it into 2nd. way over shot the turn, and lost a lot of time. ill see if i can find the vidoe of the PCA festival weekend where this happened.
blip and shift is something everyone should do, or learn to do. its a primary skill in my book.

Thundermoose

Clutch in, 5-4-3 as speed declines., blip and release. There's some braking in there somewhere.

ace37

bpu699

Interesting that there are variations on how its done...

Downshifting one gear and blipping isn't too bad... Downshifting **TWO** gears, while trying to blip on each gear and then also lifting a bit on the clutch for each gear might take way too much mental thought while going 100mp into a corner... If you second guess yourself even for a microsecond, you will screw up and go off track, no? Isn't that basically almost double clutching? Mark, is there a secret to doing that? Ever had a moment when you try to "think" about something as you enter a corner? Your brain enters some kind of slow down freeze loop as you divert from pure muscle memory to actual thought...

I did watch a bunch of you-tube videos, didn't see pro's doing all that footwork. But perhaps their gearboxes don't have synchros?

I have come to think and realize that the guys with PDK transmissions, or even just an old fashioned automatic, have a huge advantage on the track in turns, even at HPDE events. I suspect the pros on this board could easily clutch/double clutch close to what a PDK/auto does. For an intermittent weekend enthusiast rowing through the gears smoothly and trying to double blip/double clutch at each turn seems to zap up a lot of valuable time. The alternative is to just put it in gear, and let the synchro do its job... but that causes lots of wear...

Seeing the newer cars with PDK/ASC/DSC/ANTILOCK/COMPUETR ADJUSTABLE YAW/ADJUSTABLE TORQUE/ADJUSTABLE SPRING RATES fly in and out of corners seems heroic... but probably less fun than old school .

911ted

Awesome momentum driving video, thanks for sharing
Last caveat, thus my initial whining, If you end up sticking a 993 3.6 Liter into one of those "air cooled relics" you are PCA classed with the ALL the Cayman types. With the 3.6, the air cooled relics tend to do more track out grunting than the video shows with the 3.0L. Its all good

mark kibort

that can be a little harsh for a 928 tranmission, as all the work is done by the synchros. perfectly fine for street use, but on the track which the sycnros having to bring the drive shaft and clutch discs, and any rotating mass like a intermediate plate , from 4000rpm up to 6000rpm , is a lot of force . but you can relieve this force by blp between gears and an almost totally depressed clutch. total depression forces all the speed changes to be caused by synchros, partial and blip, allows for MOST of the force to come from the engine and not the synchros. they are used for a very small speed true up.

when i discoverer this, it was a godsend and a lot safer and actualy, allowed for better concentration going into the turn , along with a LOT more control. (in my early days of racign, before, you could hear a lot of crunching later on in races.. and the transmissions would just wear out) However, you dont think about it, its not like double clutching at all. its just blip and downshift, while either braking or maybe not braking (some turns i brake and blip, and a second later, just blip and shift to get to 2nd gear before the turn entrance like, turn 2 laguna or the 2nd turn after the main straight (like laguna, hairpin left) at auto club speedway. what can mess me up , is if the transmission is real hot, near the end of a race and it gets harder to get it in gear. the blips have to be very accurate (deliberate and high enough on the RPM) so that the shift is successful.. if i dont, i wont be able to get 2nd engaged smoothly, or it might not go in at all an then the turn is blown.
the hardest gear shift , with blip because of the rate of decel from a pretty high speed to a very slow speed (130+ to 40) is that little kink at ACS before the lead up to the main straight. Go to 1:50 on this video. it looks smooth there and gives me a LOT of control through the slow turn, but if the gear is missed, its a messy event.

bpu699

Mark, cool video...

Ahem...is that a cd player/radio in your race car ? Pretty cool if you get a chance to play it...

mark kibort

Hahaaha! Funny short story... for many many years, even during world challenge races, i would drive to the races with the CD player in the dash and, remove it before race time. (and the sub woofer , and amp, etc, all connected with multipin connectors for quick release) then, i finally pulled everything out and used a headset and iphone, and now, its 75% on the trailer, so no more... BUT, the deck is a photograph of the deck, put in the plastic trim frame.

9114609048

You've been explaining the technique very well. Driving those 70s Porsche race cars was so much fun, but challenging if you screwed up. The cars were great, however the 915 gearbox was sloppy, had a long throw and not precise...reason for some blown engines.
I had a chance to test in a modern Porsche Super Cup car and it was no fun compared to the "old relics".

Video of the pedals, that would really tell the story.

Thundermoose

Not disagreeing with you but just not a technique that I have mastered. My ZF has held up pretty well though I am only doing time trials.

mark kibort

Im sure you are fine!
when i look at video of my shifting back in the early 2000s , i have to cringe a little. after working on them and taking them apart, i want to be as nice as possble to these little street boxes that are being demaned to perform on the race track! Im sure you will be fine. actually , one of the reasons i started to do more blipping was i was getting really jealous of the sounds the new (at the time ) cup car was making, so i started making my own V8 blipping noises that actually sounded pretty good. and , it made shifting and driving in critical areas of the track a little easier.