When you are heel toe downshifting multiple gears (from 4 to 2), I know some people prefer to go directly from 4th to 2nd while others go from 4 to 3 to 2. For those that row through the intermediate gears, do you release the clutch while you are in an intermediate gear (for example, in shifting from 4th to 2nd, do you release the clutch when you are in third)? Is the purpose of rowing through the intermediate gears to take advantage of engine braking? Are there any other advantages of this particular heel toe technique?

 

Modern cars don't require "engine braking". The brakes should be adequate enough to do their job to slow the car. If they cant, you need to improve the system (pads, fluid -often enough, worst case then increasing the performance of the package through rotor, caliper, etc...).

You will see arguements on both sides for rowing vs. skipping.

Rowing = less wear on sychros, harder to do.

Skipping = modern synchros are good enough, easier to do, not as hard on clutch, blah blah blah.

In reality its not going to be the end of the world either way. Rowing is probably better, but its a harder technique and you will probably find faster lap times and easeir to drive by skiping gears and being more efficient under brakes (one of the biggest problems for HPDE/club racers).


Billy

 

I row if the braking zone is dead straight, and skip if there's some curvature that takes extra finessing of the brake pedal.

 

I've been clutch-in, right ball (of foot) on brake and heel-blipping as I row down sequentially, then clutch out on the target gear.

But I have no idea if I'm wasting effort. I think it just helps each synchro decel, but not sure if I'm missing the point completely. I've been wanting to ask the same question.

 

I skip gears on the way down every time. It doesn't seem to have any ill effect on synchros (~80+ track days in the 240Z, only 16 in the S). Eliminating a downshift eliminates the possibility of botching said downshift. I feel more comfortable braking a smidge later and feel I can threshold brake better (my ABS isn't functioning) without worrying about having to get 2 downshifts in.

[edit] Maybe worth mentioning that I delay downshifting as late as possible to minimize rpm drop and to smooth things over if/when there is hamfootedness (new word?) in executing the downshift.

 

http://www.trackhq.com/forums/showthread.php?t=1889

this is a long thread at Trackhq. it turns out there are 4-5 variations of downshifting multiple gears.

in the end, I would listen to Billy. he is the fastest and smoothest at shifting that I know of.

 

Thanks William.

Definately read through it if you have time, my SN is STUNTMAN on that forum.


Another cliff note:

For many people and especially for those who need to work on their footwork, a lot of time can be had by focusing on threshold braking efficiently (dosnt mean stomping on the abs as hard as as late as possible, but working up to finding the limit consistently where you are braking at 100%).

Blipping the throttle creates uneven brake pressure which leads to inconsistent brake zones. It takes A LOT of time and practice to be able to effectively blip the throttle on downshifts while not only maintaining consistent brake pressure, but to properly modulate the brakes and trail off the pressure during the brake zone (less brake pressure is required the slower you go because 800psi of brake pressure at 140mph probably wont lock the tire or kick in abs, but it will at 60mph).

The best rule of thumb again is to work on braking consistently and just skip gears. Practice your heel-toe downshifting on the street. You dont have to drive like a jackass and put people at risk on the street by thrshold braking, what you should do everytime you are getting off a freeway offramp or coming up to a stop light, practice a downshift or two WHILE you are braking. You DO NOT have to be braking hard atall, actually decelerating like a normal human being (very lightly on the brakes) while on the street is great practice to work on modulating hte brakes on your heel-toe downshifts. -Work on blipping the throttle while not affecting the brake pressure (not making a jerky movement on the brakes while you downshift). Do this every day on every stop and you will get better.

Edited below:

Ckit: your technique has been discussed. The short: rowing thru the gears with the clutch in the entire time slightly helps the synchros, but blipping each time (with the clutch in) doesn't really do anything since the clutch is engaged. Either way it would be better to just work on your braking and skip gears and go from 5-2nd with one big blip rather than 5-4-3-2 with the clutch in the whole time while. The downshifting technique that is easiest on the sychros is:

Clutch in
Clutch out in neutral/blip
Clutch in
Downshift
Clutch out

This process can be done just as fast as threshold braking and skiping gears BUT IT IS A LOT HARDER and takes a lot of practice. Skipping gears with one blip and one downshift movement simplifies things and enables you to focus on your braking/applying proper brake pressure.


Everyone should practice on the street, but again you should be driving like every other car out there, and modulating very light brake pessure (braking like a normal person) while practicing your blipping is great practice.


Billy

 

good write up !!

 

Humbly confused here.

Billy,
I understand the synchros to be responsible for spooling up the input shaft on downshifts through drag, with the clutch depressed, of course. The following AP1 numbers are from this calculator

http://www.turnzero.com/technical_resource...gear_calculator



They may be off a bit, I am just using them to illustrate my thought process.

Jumping straight from 5th to 2nd at 60 mph requires the input shaft to go from roughly 4,000 RPM to 9,000 RPM. If the shift is instantaneous, it is a 5,000 RPM workload for the 2nd gear synchros.

Comparatively, rowing through 5-4-3-2 with the clutch depressed results in steps of 4,000 - 4,600 - 6,000 - 9,000, distributed over 3 sets of synchros. Of course there are many variables. Sans flappy-paddles, the shifts are not even close to instantaneous, and under hard braking the final drive is decelerating rapidly, etc. . .

I do understand your description of double-clutching (not that I want to open that can for the 1,000th time) and how it saves wear even further by spinning up the input shaft via the engine/flywheel, leaving little left for the synchros.

Regardless of whether or not the clutch is released between gears, the synchros are loaded every time a different gear is selected, yes?

My confusion aside, thanks for your continuous participation in the forums. You patiently offer up a lot of great information and the community is damn lucky to have you.

 

See Bill's comment a few posts earlier -- where he says that going through all the gears results in less wear on the synchros. In his response to CKit, I believe he means that it won't reduce your lap time. You only let the clutch out once, and that's the point where your downshifting technique can affect your track performance.