vehicle speed may not be the only/best thing to look at. drag will start to slow you down when you get off the gas/step on the clutch, but acceleration momentum might skew that a little. i think you should also look at the rpm drop point. whether caused by lifting or clutch, it may show up a little sooner than speed drop, although this is affected by flywheel a little.

on the drag strip, the worry about shift time may be a big thing, but on a road circuit, being in the right gear, corner entry/exit speed and smoothness will gain you more time than a fast shift down the straights. and of course, a missed shift anywhere will cost you more than fast shifts will gain.

 

Sorry, but such a creature does not exist.

 

This is the point of the exercise. You should not try to be slow, but you should only be as fast as you can be smooth and consistant. If you are too fast you start risking misshifts. You also start crunching things, which is fine for a single hot lap but not so good overall.

 

I was about to call foul as well...

 

And I was about to file that next to 'perpetual motion'...

 

My point was that every 10th of a second you can pick up contributes to lap time. There is nothing to concentrate on the straight other than your shifting!!! You don't need to concentrate on your line. Assuming you're braking in the same spot every time and getting the same launch off of the corner leading onto the straight, getting your shifting done most efficiently is free time!


Anyway... remember that when you look at the data, the width of the decel pulse is from when you clutch-in to clutch-out not how fast you're shifting the transmission. Concentrating on timing the gear engagement and clutch-out/throttle pick-up as well as clutch-in may prove to be where some of your time is made up. And this is done without actually speeding up the syncro engagement!

 

This (incorrect) correlation between an increase in shift speeds and the decrease in lap times is often made.

The thing to note is that while person A may be shifting more quickly than person B, person B is not stopped while they are shifting - they are still moving along at their pre-shift speed. What they're missing out on is that much extra moment of acceleration.

In most all cases, spending .x less time on shifts will not result in a .x quicker laptime, it will in fact be something smaller.

This often comes up as an argument against shorter gears, the argument being that the extra time spent shifting will negate the extra thrust, which usually isn't the case.

 

And I was about to file that next to 'perpetual motion'...

A useful training tool to incorporate along side the datalogger would be video of the inside of the cabin. Specifically the driver. While you are otherwise occupied operating the car on the track you may be making several piloting errors that you are unaware of. I tried this once and found a bazzilion little errors... forgetting to check the gauges on some straights, resting hand on shifter, working the wheel hand over hand, etc.

It was a great tool to break some bad habits.

 

Yeah, that's probably my next investment -- a video camera to help me understand the data that I am logging.

I also think a throttle/brake/steering sensor package would be much more useful than a suspension travel sensor package as a first addition. [Well, thinking it over, I guess it depends on whether you are trying to tune your car or tune your driving.]

 

Well, to be even more precise, you are losing some of that pre-shift speed, esp. for higher gears, since you're decelerating during a shift. My datalogger says I lose about 1.5mph during my 4-5 shift because I have to double-clutch (worn 5th gear synchro); it takes a good 1/2-3/4 sec. If I could do it quicker, maybe I could carry an extra 0.5-1mph down the remainder of the straight.

Point taken, though, and an another argument in favor of not trying to force every shift....Line, vision, smoothness.