Please explain the correct way to shift for max acceleration

[JonT]

Is there a certain way to shift to maximize acceleration? How are the guys at R & T and Car & Driver doing it when they test 0 to 60? How do the track guys do it? Thanks!

[Efrain68912]

Just shift smoothly and deliberately. Do not "speed shift" or "power shift" or whatever it is called. It is not any faster and only beats up the car.

[GSpreeman]

Since you brought up the topic, I just got my first 911 (1987). The seller explained that he liked to rev up to about 4,000 rpm before shifting into 2nd. Yeah, it sounds incredible but am I going to destroy the engine/clutch? The manual says to shift from 2,000-2,500.

[k9handler]

2000 seems too low unless you are driving Miss Daisy! I shift from 1st to 2nd in the 3000-4000 range...might even push a little above that once in a while.

[ZAMIRZ]

Umm, I've been accused of beating the car but I"ve speedshifted before. I've only done it about 3 or 4 times, and my dad's never done it......my conclusion; stupid idea especially in a porsche. When you speedshift you are deliberately disrespecting the car, and although the shift is a bit quicker (i don't care who says what, my car was quicker when i speedshifted it.....depressing clutch rowing 915 and engaging clutch takes a while even for the fastest people) but the benefits are marginal and when your clutch is f***ed you'll curse yourself for it....been there done that. I recommend just making smooth, quick shifts with good synchronization of gas and clutch......the latter perhaps the most important in making a quick change. Either way, don't be afraid to experiment a little bit just don't do anything stupid. And before anyone asks, I knew how to speed shift before I did it on the 911 so I didn't teach it to myself on this car.

later,

amir

[radcon]

You will not, I repeat will not, damage the engine by shifting at 4K rpm. That is where the engine is starting to make most of it's power. If you take the engine up to the redline, you will see that the engine will really start to take off once it hits 4k. At least that's how my SC responds. Maybe earlier and later cars are different. The 911 is a performance car, it's made to be revved. Now maybe taking the car up to redline for every shift is another matter. Shifting the car at 2000 - 2500 may be good for gas mileage but little else. A friend of my wife's has it engrained in her head that it's better to shift at as low of revs as possible. She shifts her little mitsubishi at 1500 - 2K. You can probably guess what the engine sounds like after every shift - chug, chug, chug. Lugging the engine like that puts a lot of stress on the engine, not to mention destroying the fuel mileage. Don't worry, just rev it!

[Zeke]

The question here seems a bit in contradiction of terms. Correct shifting IMHO is not necessarily going to get the best acceleration times. If you are going to abuse it a little, then you are going to abuse it. You can't pretend that you are not wearing things out earlier driving and shifting at the red line.

Just don't miss the gear! That can result in some significant damage.

[Jack Olsen]

3-4K Street.
5-6K Track.
5-6K when emulating Track mode on a Street.

[CamB]

And add +1k for early S (or more) engines

[smarjoram]

what's speed shifting?

[speeder]

As to the question of where in the RPM band to shift for maximum accelleration, on any vehicle the answer(but not necessarily the RPM), is the same: the object is to shift at the point where you catch the next gear in the peak torque range. If this range is say 4000-5500RPM, (my SC), you want to accellerate as hard as possible, making quick shifts always staying in this range. If any of your shifts result in the engine speed dropping below 'torque band', there will be a slight loss of maximum velocity in the moment it takes for engine to climb back into this range. This practice requires quick shifting to avoid dropping out of torque band, but you do not have to 'speed shift'. On transmissions that tolerate speed shifting, (not the 901/915 trans), it is the fastest way to accellerate, but not worth doing on our cars.

We catch them in the corners anyways.

[speeder]

Speed shifting= Accellerator pedal on the floor, (it stays there), and "stab & grab" the next gear.

[smarjoram]

Accellerator pedal on the floor, (it stays there), and "stab & grab"

good lord...

I can see why this wouldn't be wise with a 915

[A Quiet Boom]

Believe it or not on some (I doubt 915 and 901) transmissions powershifting a high HP engine is actually easier on the tranny than quickshifting. Ford Toploaders are this way when coupled to a lot of torque. Keep your foot in it, kick the clutch and change gears at the same time. As opposed to allowing the tranny internals to "spin down" with full clutch disengagement. However 911's are not drag cars, and every 10th doesn't count but finishing the race or getting home does so a good fast shift will do it. As far as when to shift for best acceleration you need to shift just before the motor "noses over" (goes past it's HP peak) if you're good you can feel this point if not refer to the factory HP specs as a guideline. I frequently shift my 2.0E at 6500 just before it "noses over" and the difference between that and say a 5000 shift is night and day. Remember 911's are made to be revved, think of the gearing in our cars and the rpms these motors must take for hours on end at speed on the autobahn. Ever notice that topspeed is about equal to redline in highgear? Try a few standing starts like I described and tell me it doesn't feel like you've added 50+hp to the motor. 911=small motor with big intake and exhaust ports which equates to high rpm power not 2500rpm granny shifting unless you like carbon buildup. Just don't let the clutch slam the next gear like you would in a muscle car and your p-car will be happy. In other words driven the way it was meant to be.

[Jgordon]

Hmm. So if I depress the clutch while letting up on the gas, as opposed to releasing the gas fully before declutching, am I subjecting the engine to abuse? I can understand not wanting the full pressure of acceleration on the clutch while depressing it, but should I be practicing the "gas up, clutch in, shift gears, clutch out, gas back on" maneuver?

[billwagnon]

so from first to second - shift at over 4000 rpms?

[gr8fl4porsche]

As long as there is no one right in front of me - I shift my 87 routinely at around 5500. 6500 when the smile starts to wear down a little

I shift my wifes Subaru near 5800 just to get the valves working a bit. She only drives 2 miles to work each day so it is up to me to give the Legacy GT a little excercise.

Bottom line - drive it like you stole it - its a Porsche for Gods sake!!

[billwagnon]

I drove my 81 Toyota Tercel like I stole it (60 hp on tap!*) - I want my 911 to last a little longer!




*I think the "horses" involved were simply large dogs.

[724doorE]

7000 RPM plus......wouldn't want to foul those plugs now would we

[Rick Lee]

It's perhaps worth mentioning that you shouldn't rev it too high until the car is at operating temp. I wait until the oil temp gauge is outside the lowest white box before I take it above about 3500 rpms. Once it's plenty hot, I make a concerted effort to take her to 6200 rpms every chance I get. Why have a Porsche if you're gonna drive it like a Mazda truck? My 911 really comes to life at the higher rpms. They are made for it.