c32b

Hi folks, would like a discussion on rev matching on a downshift. i usually rev match by giving a short sharp blip on the throttle and release the clutch at the same time while getting back on the throttle right away so i can drop gears without any discernable pullback from engine braking. its buttery smooth and i've used that on a previous car (with a notoriously glass gearbox) with no problems for >2 yrs. i've also not had any problems with traction loss when downshifting (if i get it right) and it seems to help me get on the throttle quick. i like to turn the car with the throttle and "point the car with the tail" feel which is why i my s2k .

i dont double clutch but use the backing off of the throttle and braking to release pressure enough for me to snick it into neutral, give a blip in neutral and clutch out with a half dip of clutch to get into the lower gear. i was doing this by feel and after i read "Going Faster" realised i fall into the category of shifters who blip just once but give bigger blips than usual. the effect is that a blip sends my rpms up and the throttle i give holds the rpms up high. my clutch is out by the time i'm on the gas.

recently i popped into the shops with some clutch queries and was asked to drive to allow the mech to assess some problems. he saw my driving and told me i was too "hardcore" a driver with "no mechanical sympathy". he then told me that blipping was right but i blipped far too much and i only needed to blip just enough to match.

he then proceeded to demonstrate by driving and dropping a gear on the move. what he did was basically something i view as improper technique as he blipped it when the clutch was dipped fully and proceeded to ease out of the clutch once he was in gear (he did it fast though). the net effect is that he seemed to be slipping the clutch to engage the gear smoothly on the downshift.

the difference from me was that where he was slipping clutch to engage the drive to the gear, i would have been out of the clutch on the gas already. this mech has experience with endurance driving and told me my style would basically be too aggressive to last an entire race.

i admit that i'm not the best driver and i dont get every blip 100% creamy smooth however, the less mismatch there is, the better in my mind so i blip and heel toe always. i know many drivers have differing techniques (like 2 blips per shift or 1 blip) but is my technique wrong? i dont have access to the Skip Barber's training so its a bit tough for me to know.

your input is extremely valuable and i hope the seasoned racers can help me.

DER MotorSports

My perspective is he was favouring motor life over clutch life. Real racers can manage an auto (even with synchros) without a clutch save dead stop starts and clutch life is not as important to them as motor and tranny life (UNTIL they spin out on course). Further bear in mind real race gear boxes don't have synchros making the prospect of a a missing clutch even less daunting. I don't see anything wrong with your technique and it is better than 99,5% of sportscar street drivers. Perhaps be a little slower with your movements with bigger throttle bites - biggest err I encounter amongst drivers. Funny thing is that heel toe double declutching gets far easier and smoother with speed versus slow driving. If you're smooth at slow speeds, you got the idea pretty well done!

c32b

Thank you for your feedback, i've been experimenting over the weekend and i'll try out your suggestion

S2Kretard

If you're doing it right there is no compromise between clutch life, gear life, and motor life; unless you're trying to go fast in which case you use the synchros a bit but that's not really an issue worth losing time over.

Personally, I double-clutch my street car pretty often just because I like feeling the gearshift lever slip into gear so easily. But, if I'm trying to go fast at all, I don't bother with it; that's what synchro teeth are for. If I'm going fast on the track, definitely single-clutch.

Also, I don't think the guy who wrote the Skippy book (Carl Lopez) really understands how a gearbox works. He states that if you don't double-clutch, you need to blip to a higher RPM. That makes no sense... you need to blip to the same rpm whether you double-clutch or single-clutch.

I also don't think the OP understands how a gearbox works

driftintherain

when i slow down I heel-toe to rev match.... but what is double clutching?

c32b

hi, if you single clutch when u go down a gear on the car, how do u do that?

a blip when you're have the clutch dipped and clutch out?

in the book, i believe that he is saying the rpm that you double clutch to might be lower than the one that a single blip works for. i dont double clutch so i dunno if its any higher were i to do so. logically, i dont see why it should be any higher.

anyone to share why it might be higher?

c32b

http://en.wikipedia.org/wiki/Double_declutch
chk it out dude.

although sadly, there isnt much on the single clutch variation.

FormulaRedline

By single clutch he just means rev matvhing while the clutch is in instead of letting it out in nuetral like double clutching.

driftintherain

so since we have synchro double clutching is unnecessary right?

S2Kretard

Single-clutch =
Brake
- Clutch in
- Blip
- Downshift
-Clutch out
-Repeat rapidly, once for each gear


In this video, the first downshift is a "single-clutch" and the second downshift is a "double-clutch":
http://youtube.com/watch?v=IuoZeuSgEj4

Here's an example of what I would call close to "proper" single-clutch downshifting:
http://youtube.com/watch?v=klMur6TPkrM&feature=related