When to shift?

[Ridenour]

I've never really figuired this one out.

I'm not sure exactly when to let my automatic shift. I've heard you're suppose to let it wind up as far as possible in each gear. But then I've also heard that anything revving past torque peak is lost power. So which is it?

My Grand Am's rev limiter is @ 5800 rpm. The torque peak is 4800 rpm.

So, when racing, should I just put it to the floor and let it bounce off of the rev limiter every time?

or

Ease up on the gas at about 5000 rpm so it shifts and then give it more gas when it shifts so it ends up staying around the torque peak?

So which is it - floor it, or try to keep it around the torque peak?

Thanks guys

[Ridenour]

PLEASE!!! ANSWER MEE!!!!!!!!!
RAGGGGGGHHHHHHHHH!!!!!!!!!!!!! lol

[drdisque]

letting it bounce off the rev limiter is just slowing you down and horrible for the engine. Through very thorough testing, its been determined that the fastest way to drag race an automatic is to just leave it in Drive with Overdrive off, even on automatics with "sport shift" features.

[Ridenour]

Ok good that's kind of what I was leaning towards.
And yeh you're right about the second part - I always put it in 3rd gear in order to lock out overdrive and it does a lot better.

[buymeabmwm3]

Check out http://www.cyberstangs.com/autocalc/...hiftPoints.asp

Pretty sure that fastest acceleration is achieved by running from torque peak to horsepower peak, and I think most cars' gear ratios are designed to reflect that fact. My car has the gear ratios spaced such that upshifting from the horspower peak drops the revs right onto the torque peak in the next gear.

[RVMAN]

You're on the right track locking out OD. Next step is to have a shop "tweek" your tranny for more positive(i.e "hard") gear changes...also look into converter stall speed etc.

[Ridenour]

Ok all these replies sound good. Thanks guys.

[AlienEvolution]

Hey, how can you find out the Torque peak for your car?

[buymeabmwm3]

Usually listed anywhere you can find info on your engine. Do a google on your truck specs. Engines are described as having, for example, 200 hp@4000 RPM and 250 lb-ft@3000 RPM. The lb-ft # is the torque peak.

[crzyCollegeKid]

i'm gonna talk as a honda guy cuz thats what i drive. i get my best times when i rev into the red line and shift right before i hit the limiter. but why? cuz even tho i'm not making much more power in the redline, when i shift, the engine still lands in the vtec powerband and doesn't bog down. you can't go by factory specs and numbers, unless you sit on a dyno in your own car, and then do some trial and error on the track. i know your question was about an auto tranny, but hopefully this will give you some insight. you have to try land as close as possible to your peak torque and horsepower when you shift, even if it means slightly overreving

[AWP9521]

Some engines are like that, you should be able to feel it in the seat of your pants when the engine is beyond it's powerband, you know you have revved it too far when you feel the motor start to "lay down" and the trick is to get the shift off before that happens. It just depends on the design of the engine, some you can rev them right up to the redline and they feel like they will pull well beyond it and others will lay down before the tach gets close to redline and it seems like it takes longer for it to wind up that last 500 RPM or so.

I own 2 examples of what I'm talking about, I got an 89 Daytona Shelby with a 2.5L Turbo I engine in it, Redline is 6000 RPM but the engine feels like it starts to peter out at a little over 5000 RPM but yet has gobs of torque down low so if you shift at 4500-4800 the RPM drop is still in the meat of the torque band and the acceleration doesn't suffer. I also own a 94 Chrysler LHS with a 3.5L 24V engine, this engine has decent torque down low enough to spin the rubber but really doesn't come on strong til the tach hits between 4000-4500 (Probably like crzy's Civic) and then pulls real hard right up to it's 6500 RPM redline and even then it feels like it can go another 500 RPM or more but the tranny (Auto) electronics will not let it as you can have it locked in "L" and it will still shift right at redline on 1-2 and 2-3 upshifts then lowers the shift point to 5000 at 3-4 if you stay in it.

[Ridenour]

Hmm yeah more good replies. Yeah, from what you said AWP, I'd say my power band is definately about 4500 to 5500. I've been experimenting lots now, and If I let off at about 5500, and then gun it while it's shifting, I can effectively keep it in the power band. But if I let it wind past 5500, it's goes from "BWAAHHHHHHH!!!" to "waaahhhhh......" lol
and all the pull goes down the drain.

thanks again for all the good input guys.

[crzyCollegeKid]

civic?!?!?!!? dude, that hurts.
not all hondas are civics. look at the sig

[CBFryman]

drive, do a couple pulls in each gear, find where you engine begins to sit down and shift right before that.

[op012503]

how can an auto tranny allow you to hit the rev limit????