random911

Hello

Long time reader, first time poster. I am looking for help figuring out how to better shift for best straight line speed coming out of corners onto straight lines, from fellow track or non-track enthusiasts

Given the fact all the 911 models are all so different, from the stock carrera to the track monsters, I am not looking for the most optimal shift points for a specific model. I drive a 991.1 (Carrera S 2016, with some mods).

I tend to think most of us shift by ear and feel, and of course watching redline.

What I am asking is how late can you shift to squeeze as much straight line performance as you can, and what are the signs to watch for that you need to shift earlier? I think I shift at too high revs. or is it really very model specific? I know the GT3's can go really high in revs.

Tips please

certz

You want to ensure you stay in your car's power band. I would recommend you look up your torque and power curves, as well as, the rpm drops for each of your gears. Typically HP will level off as you near redline, so you may think you want to shift earlier, but if the rpm drop of shifting early puts you out of your power band for the next gear, that is not good for what you are looking for. That said, if the corner leads to an uphill straight, then maybe shifting early to take advantage of your car's torque is the better option. Anyway, experiment and have fun.

Auto_Werks 3.6

Don't over think it. Just drive the car. No need to watch the revs, engines are ok to run to the red line, and if you screw up, you'll hit the rev limiter. This is also not a problem. You hit the rev limiter a couple times and you will retrain yourself to shift a little earlier. Up shifting is super easy, just drive to you personal comfort, the sky is the limit. Do not lug the engine, that's all you have to do. Downshifting is more critical to be done correctly. You can damage the engine by downshifting too soon, or into the wrong gear, causing the wheels to drive the engine faster than it's computer controlled rev limit.

For the most part, just drive and enjoy. It's your car, drive it how you want. Too much thinking will only cause stress.

random911

Thanks for the tips. Yeah, I guess I could be over complicating it. @certz you are exactly right, I feel the HP drop off close to red line and that's what been messing with me. Been looking for these ratio/rpm graphs but there aren't many around. Next track day weekend after next, going to experiment. Thank you

Auto_Werks 3.6

There's no need to push the engine past that drop off that you feel with the seat of your pants. I usually shift my GT3 around 7,800 if I'm not looking at the tach. The redline is 8400. A lot of the Porsche engines have RPM available beyond peak thrust in gear. You can use this to your advantage depending on gear ratios, how low the engine is going to drop when you select the next gear, and also there are times on track or at an autocross where a gear change doesn't make sense because you will be slowing down again too quickly for the shift to pay off. It's nice to have that over run, so you can let the engine sing and hold off on the shift. Again, just do what feels right. You will probably shift the car better if you don't pay any attention to the tachometer on the up shifts. Don't forget to be mindful of the downshift points though. I can't stress how important it is not to be over zealous when downshifting.

raspritz

I am assuming you realize this is the early 911 forum, which is supposed to be about 901 and 915 transmissions, which have nothing to do with your 991, right? That said, speaking as an avid racer (not just track day guy), why are you thinking to be shifting coming out of corners onto straights (your words)? You set up for corners at the end of the preceding straight by threshold braking and downshifting in the braking zone, into a gear that will allow you to trailbrake through the first part of the corner so as to keep the RPM in the power band through the entire corner and onto the following straight. After corner exit once the car is stable you upshift when you hit redline. To achieve all this you may need to give up speed in the first half of the corner setting up for the apex, so that you are accelerating before you hit the apex. As a general rule, think slow in, fast out.

EDIT: If any of what I said above seems unfamiliar, you might benefit from doing a PCA DE with an instructor.

random911

Thank you both. Exactly the kind of advice I was looking for. I've botched a million turns and that trail braking is definitely always a project. I think I need to put a huge sticker on my windshield that says "SLOW IN, FAST OUT". Sorry for posting in the wrong forum :| didn't realize I did that. Cheers.