JP66

Just wondering if anyone here has data on a heel-toe downshift. My data shows a blip but then the RPM falls below optimum before settling so it looks like I'm slow releasing the clutch. I didn't notice any unsettling of the car when I was at the track, but again the data hints that maybe I'm off slightly.

Anyways, just curious.


Obviously I'll keep practicing and hopefully get better and faster


The picture below is a blow up of the first blip you see on the second graph. That's the downshift at the end of the front straight at Lime Rock Park where I'm going from 4th to 3rd. The red line on the first graph is RPM.

ProCoach

Too early, too big a blip, perhaps? Need to see the file.

linzman

I think it would be much easier to compare these if you used a separate graph for each variable instead of having them all on one graph, but that's my opinion. . Double clicking on the y-axis to auto scale everything would help tremendously, although the second graph is better

ProCoach

To do this, click on the separate graphs button, top right, next to the wrench icon button.

JP66

How's this? Any more useful? Does anyone have an example of a professional blip?

ProCoach

Double click on the "bar" numbers on the left side of the pressure trace.

I see ONE blip, WAY too early, almost immediately after you begin braking for Big Bend.

Maybe the remnants of an attempted second blip at the 400 ft mark, but not good enough.

First one needs to occur at or around the 375 ft mark, second at 550-600 ft mark.

40-50% is plenty of throttle for the blip, don't need 80% plus...

JP66

Fixed the braking graph

I could always be mistaken, but I am pretty sure I did not ever 2 blip (at least not intentionally) so I was thinking that the second RPM blip is occurring because I am holding the clutch in too long and the engine RPMs fall below what they need to be at for 3rd gear so when I release the clutch the RPMs jump to match the engine. It seems odd to me because I never noticed the car becoming unsettled by a jerky downshift, but this double blip pattern is in almost all my runs.

ProCoach

Got more work to do than you thought!

JP66

So now looking at the data and reading what you are saying, I think I'm learning that right now I'm braking and hitting the clutch at the same time then blipping then releasing and what I should be doing is just braking for a few hundred feet then downshifting with a heel-toe, but in either case staying off the clutch until I'm ready to shift.

Could that be it or something similar?

JP66

Oh no I always knew there'd be tons of work for these slow reflexes of mine, but I did hope . . .

ProCoach

Yep. I think the greatest value of data is to review and discover opportunities for performance improvement. In this case, the purpose of the downshift is merely to select the proper gear for most efficient delivery of power entering, progressing through and out of the corner.

Prioritize braking first, then coordinate clutch actuation, throttle blip and release to be tightly integrated.

JP66

Here's something else that catches my eye and is somewhat related to my recent math surrounding acceleration in different gears.

There is a long time spent in 3rd gear that could be spent in 2nd gear.

Any thoughts?

ProCoach

And I'll tell you the same thing.

Try several laps in one strategy, several in the other and compare segment (or sector) times.

pmiranda

Definitely leave the clutch engaged until you are actually shifting. You generally want the brake bias set up assuming engine braking at the rear. (Forgive my ignorance but I don't think caymans are AWD?) If you put the clutch in too early, then you are both asking the fronts to do more work and making it more likely you'll lock up the rears. ABS will keep the car under control but at the cost of longer braking distance.

You should only need a short time on the clutch and a stab of the throttle to make the shift. With modern light flywheels you lose revs fast so you don't want to start off "on the wrong foot" (pun intended) by losing revs with the transmission coasting.

Find an empty road or long run of driveway or parking lot to practice, without the distraction of needing to make a corner. You can get your heel and toe nailed down for free instead of during costly track time. And be sure to practice with both high and medium revs in a few different gears so you can get a feel for how fast you lose revs at different points, as will happen with different speed corner entries.

IMO it's better to err on the side of being low on revs since a little tug from the rears will usually be more stable and easier on the clutch than being high and having the brakes fight the engine, but that is possibly bad advice if your car is set up very neutral.

Matt Romanowski

It sounds like you have a handle on what to work on. This is also a time when video with data on it helps a lot. You can review your video to see where you are doing things and how much. It will also help you with reference points and markers to use while in the car, which will help with all of this.