When to shift?


Ridenour
12-29-2004, 01:17 PM
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
12-31-2004, 05:50 PM
PLEASE!!! ANSWER MEE!!!!!!!!!
RAGGGGGGHHHHHHHHH!!!!!!!!!!!!! lol

drdisque
01-01-2005, 12:50 PM
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
01-01-2005, 03:45 PM
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
01-04-2005, 08:41 PM
Check out http://www.cyberstangs.com/autocalc/calc_ShiftPoints.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
01-04-2005, 10:03 PM
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
01-08-2005, 12:55 PM
Ok all these replies sound good. Thanks guys.

AlienEvolution
01-12-2005, 11:01 PM
Hey, how can you find out the Torque peak for your car?

buymeabmwm3
01-13-2005, 11:09 AM
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
01-15-2005, 03:17 PM
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
01-15-2005, 06:25 PM
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
01-16-2005, 07:22 PM
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
01-17-2005, 11:31 AM
civic?!?!?!!? dude, that hurts. :eek7: :crying:
not all hondas are civics. look at the sig :D

CBFryman
02-01-2005, 05:33 PM
drive, do a couple pulls in each gear, find where you engine begins to sit down and shift right before that.

op012503
02-20-2005, 10:55 PM
how can an auto tranny allow you to hit the rev limit????

Ridenour
02-21-2005, 11:37 AM
In lots of autos, when you floor it and hold it there at WOT, it will bounce of the rev limiter on each shift.

T38
02-22-2005, 02:51 AM
Where to shift also depends upon what you are trying to do, I think. For example, if you are only trying to get to highway speeds and smoke the guy next to you while doing it, it may be worth holding the shift past peak because the shift comes a few MPH before your target speed, and coming off the gas for those few seconds isn't worth the shift. On the other hand, if you are on the quarter mile and the skies the limit, then, yeah, you probably want to make the shift.

Case in point, one of the guys I work with was comparing the car made by one mfg and a car made by another. They were geared radically differently because in the US, the dealers talk 0-60 times, but the other car (European...I think) was geared for better 1/4 mile times. In the US car, even though the gearing restricted acceleration, you got better 0-60 times because there was only one shift in that range. With the other car, you had to shift twice between 0 and 60 (like my Talon), so 0-60 times suffered a little, but in the 1/4 mile, the European car would smoke the US car because the gearing maximized torque.

In my car, peak HP is 6200 RPM, redline is 7000. On my way to work, there is a road where I top at 55MPH (State Troopers *AND* local PD are located on this road, so I keep it slow, lol). If I run to redline on this road, I only have to shift twice, then into 5th at 55MPH, and my time to 55MPH is optimized, even though a mostly stock non-turbo Talon gets a little doggy above 6200 RPM (no comments about a NT being doggy at all RPMs from you turbo guys! :nono: ).

ssjohnson98
02-25-2005, 03:14 PM
its still a fr car, vtec, a lilmore horsies and a little reshaping dont make it a sports car. its a sporty coupe, just like a civic :smokin:

alphaboo
06-02-2008, 12:01 AM
I honestly don't know the best way to shift an automatic. I usually out it in drive an let the auto do it's job and when I need some extra speed I shove the trottle to the floor to push it into a down shift.

However I do assume it is similar to a manual. Listen to the engine. Ignore the tach after you get use to the way the engine sounds and then after that listen to the engine. The engine will always tell you when it wants to shift up.

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