Please explain the correct way to shift for max acceleration
 

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!

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.

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.

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.:D

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

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!

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.

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

:)

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

what's speed shifting?

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. ;)

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

good lord...

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

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.

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?

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

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:D

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!!

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.

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

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.

My temperature needle only makes it to the top of the lowest white box. Am I not driving fast enough - (230kph at the weekend), or is it just cold in england?

Your car is most certainly hotter than that at 230kph. There's something wrong here.

My .02....
 

Most of the Pcars that I have driven have had G50's. However i just bought an SC with the 915. At first I was a little frustrated and found the tranny disappointing. After about a week I really like the 915. No it is not as slick as the G50, but the SC is a drivers car. The tranny as well as the rest of the car commands your attention and skill all the time. Do things properly and you are infintely rewarded. Screw up and you know it.
With that being said, the orginal post taked about the technical aspect. Go ahead and wind it out to at least 4000. The car is most fun that way, and as earlier of course you are paying attention to your car. Then, and this may be specific to my 915 (but I doubt it), shift into 2nd by pulling down out of 1st, slight hesitation, pull down into the 2nd gate with a little bit of pressure toword 4th. Then 3rd and 4th normally. On down shifts use heel toe all the time. It may sound silly, but IMHO I think the car just runs more smoothly that way. Plus you'll be in better shape for your next DE.

Nap, good point on the slight hesitation thing. I used that technique on my 5.0 5spds and they lasted well, even the one with a bad third gear (got it that way). I kind of liken the T-5's to our 915 in that they will last a long time at high power, but they don't take much violence(speed shifting)!

The p-car trans has some other stuff going against it though, like a multi-jointed shift rod and shift bushings that are nylon in some cases and flex alot. Also when a V-8 rwd car launches and the engine and trans torque over, the shifter is right there with it. On the other hand, in the 911 the engine and trans still torque(move around) back there but the shift likage is mounted solid to the tunnel at one end. All that must cause some temporary bindage issues now and again, and the faster you try to shift it, the worse it can become.

Consider how tough it is to properly adjust the shift linkage to get all the gears easily! and thats done in your driveway. Then you add that engine/trans moving around and its no wonder that a 915 could be tough to shift when your really on it and take no prisoners.

oopps its lunch time, or pre lunch break time or something!... Just drive the friggin thing:D

When I first got my car I shifted way to early. After a short while, however, I realized the error in my ways. Now I shift at about 4k for routine driving and up around 6-7k for "spirited" driving. My only real question is how to best launch the beast from a dead stop. I am not looking for drag racing starts, but I do wonder how you get this car to pull 5.5sec 0-60. I am not one to rev it up and just dump the clutch. These turbos are slow as molasses off the line(but they more than make up for it later!). Any suggestions?

What about if you have a light flywheel and it spools down faster than you can shift? blip the throttle? just wondering if there are any tricks the pros use.

930's are notoriously slow off the line (w/o dumping the clutch as you mention) since as you've probably noticed by now that boost doesn't kick in until 3 grand or so under WOT (which surprises a lot of new owners when they get into a turn). I've looked into this issue somewhat and the consensus on the upgrades that can help lower the boost point are:

- Euro exhaust ($)
- Headers ($$$)
- 964 cams ($$$)
- K27 turbo ($$)
- Twin turbo ($$$$)
- Long neck intercooler to eliminate the pop-off valve ($?)

The Euro exhaust seems to be the best bang for the buck, followed by the headers. With the exhaust and header mods you can get the boost point down to 2.2 grand or so from what I've read which is great for street drivability.


-Wade
'88 930 Slant Coupe

Where is Kurt B on this? He is the spirited street shifter with the low 0-60 times! :-)

When I'm doing a 0-60 run, I will do a fast 1 -> 2 shift, but I still pause ever-so-slightly in-between.

http://www.vintagebus.com/porsche/g-tech.jpg

I never shift below 4,000. For normal driving I shift in the 4,000-4,500 range. For spirited driving 6,000-6,500 (at least once per day).

Part of mechanics' tune up procedure is to take a car out to redline. I can do that part of the tune up myself on a daily basis, thank you very much!

Before my '83 SC reaches operating temps, I'm at 4,000 RPM at shifts . . . once warm, 4,500-5,000 for street. Once a week I get it to spirited driving spots, where I can rev to 6,000 for shifts.

The 915 transmission is quirky between 1st - 2nd, and a joy afterwards.

Cheers!

C.

I am completely shocked!
 

How can you shift below 4,000? The motor is just waking up!!!

Thats like driving to Disneyland, but never going in!!!

Thats like hours of foreplay, but no....(nevermind)

My Porsche's life BEGINS at 4,000 RPM. On an open road, I shift at 5-6,000.

'87 w/ a G50 here:

Until the car is warm (out of the fat white strip), I limit RPM's to about 3-4K. I am especially careful about lugging the engine (load under 2K) - that's a no no.

When car is at operating temp (1st white line - geez, I've got to get a numerical gauge), I routinely shift over 5K, and up to 6.5K+ for the on-ramp grand prix, letting out frustrations, beating up ricers. Nothing sounds like a air-cooled Porsche motor above 5K!!

For shifting technique, the 1-2 shift is a bit more deliberate. No preload on the shifter, clutch all the way in, then back, pause back. 2-3 and 3-4 are a bit faster, but still with a very brief pause in neutral.

This may not be the very "fastest" way to shift, but for me it balances max accelleration with acceptable wear on the machinery.

Vroom Vroom Das Zoom!