Downshifting after a long straight... which way is best?
05-05-2017, 06:00 PM
#18
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As I understand from college physics, as long as torque is rising, so is acceleration. Once you pass the peak of the torque curve, acceleration slows down. You are still speeding up as you approach redline, but less so.
If downshifting puts you in a better place on the torque curve, you would accelerate faster...
Hypothetically...
If downshifting puts you in a better place on the torque curve, you would accelerate faster...
Hypothetically...
05-05-2017, 06:02 PM
#19
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That is awesome!
What I do and what I find works well for most people.
I think it's a matter of personal preference, as there are other pros who skip gears. But I go up and down through each gear. Going down I blip and release the clutch each time. I downshift at the latter half of the brake zone. And...in a slower shifting car like a 930, what's the rush? Take your time.
05-05-2017, 06:38 PM
#20
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There's an awesome Leh Keen video where he is rowing through all the gears like superman.
I prefer 4-3-2 but will got 4-2 if it matters in a race!
I prefer 4-3-2 but will got 4-2 if it matters in a race!
05-05-2017, 06:47 PM
#21
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Hmm. My foot-cam paid off, as I didn't really know, but I blip for each shift but I don't release the clutch in between. Here is coming into T11 and T12 at COTA last year:
Rowing down the gears at COTA
Since I'm the financier, driver, crew chief, head mechanic, gofer, and bottlewasher for my race team, I have a lot of mechanical empathy I don't speed shift or mash anything.
-Mike
Rowing down the gears at COTA
Since I'm the financier, driver, crew chief, head mechanic, gofer, and bottlewasher for my race team, I have a lot of mechanical empathy I don't speed shift or mash anything.
-Mike
05-05-2017, 06:58 PM
#22
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I don't see the need to blip between shifts if clutch is in. You only need to blip before releasing clutch to match engine speed and transmission speed.
I think to save synchros though you want to do downshifts as the speed allows. I find that rowing just naturally kinda gets you there.
To OP - on upshifts, do you have your thumb pointed down or up when you grab shifter? I started doing 3-4 upshifts with thumb pointed down and it seems to help protect against 3-2 shift.
I'll take a slight nibble at your comment of shortshifting at max torque vs max hp. Please remember that HP = mass x velocity x acceleration. Max acceleration therefore occurs at the point that maximizes hp under the curve given that velocity is the same for both gears at the point of the upshift. If your car is making increasing hp to redline, the optimal shift point is at redline, not necessarily at max torque.
I think to save synchros though you want to do downshifts as the speed allows. I find that rowing just naturally kinda gets you there.
To OP - on upshifts, do you have your thumb pointed down or up when you grab shifter? I started doing 3-4 upshifts with thumb pointed down and it seems to help protect against 3-2 shift.
I'll take a slight nibble at your comment of shortshifting at max torque vs max hp. Please remember that HP = mass x velocity x acceleration. Max acceleration therefore occurs at the point that maximizes hp under the curve given that velocity is the same for both gears at the point of the upshift. If your car is making increasing hp to redline, the optimal shift point is at redline, not necessarily at max torque.
no, when the clutch is depressed, all you do is disconnect the engine from the driveline. the transmission and gears, shafts, etc are all spinning relative to the speed of the wheels and gear you are in. you want to match layshaft speeds, the clutch has to be out, iparting the right RPM to the driveline to match the next gear RPM requirements... thats why were were talking about "dipping " the clutch so much before. it gives enough separation to get the car out of gear, use the blip as you pass through neutral and spin up the driveline and also allow for any speed differences then to be handled by the synchros, which will be less. skipping a gear might put 3-5x (estimated) the forces on the synchros if the clutch isnt dippped or let out for each gear change.
I'm probably overthinking it...
I get 4 bar of oil pressure when warm, max. That's 60psi or so...
I had heard the old rule of thumb of 10 psi per 1000, so figured 6000rpm was a safe place to be...
As an aside, I have been in other folks older 911's... that seems to be about what they all show at under hot use. I almost never see 5 bar in my car or anyone elses when hot...
Overthinking it?
I get 4 bar of oil pressure when warm, max. That's 60psi or so...
I had heard the old rule of thumb of 10 psi per 1000, so figured 6000rpm was a safe place to be...
As an aside, I have been in other folks older 911's... that seems to be about what they all show at under hot use. I almost never see 5 bar in my car or anyone elses when hot...
Overthinking it?
05-05-2017, 07:39 PM
#23
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Originally Posted by CosmosMpower
When I read this all I could think of was this...
05-06-2017, 12:31 AM
#25
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05-06-2017, 06:16 PM
#27
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you have good experience with your car, and a couple of rare turns where you skip a downshift. for you that is working and it might work for others if they have the same conditions. generally, there is a little misunderstanding of the gear box and how it works, as been admitted already by some here. the discussion helps to understand what might work best for anyone in any particular situation.
05-06-2017, 07:36 PM
#28
If i coached like that, there would be no improvement, well , not for a very long time. The reason there is the question, is to ask those with experience to help them shorten the learning curve. (and save themselves premature repair jobs)
you have good experience with your car, and a couple of rare turns where you skip a downshift. for you that is working and it might work for others if they have the same conditions. generally, there is a little misunderstanding of the gear box and how it works, as been admitted already by some here. the discussion helps to understand what might work best for anyone in any particular situation.
you have good experience with your car, and a couple of rare turns where you skip a downshift. for you that is working and it might work for others if they have the same conditions. generally, there is a little misunderstanding of the gear box and how it works, as been admitted already by some here. the discussion helps to understand what might work best for anyone in any particular situation.
05-06-2017, 08:04 PM
#29
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Lol! 
05-06-2017, 08:23 PM
#30
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