changing gears

[esbolico]

hello
yesterday i had to accelerate hard ( i didd no see a car) and i changed when i hit the rev limiter.is this the best moment to change? or when i arrive at max power. if you drive a diesel when do you have to change gears?
in conclusion: if accelerating hard: when is the best rev range to change gear?
thanks

[ARMAN]

What car do you have? I think it depends on the specific car

[esbolico]

i usually drive a passat 115 diesel. but the other day i was driving an honda type r. ( my girlfriends car)

[Blip]

There is a specific engine speed (RPM) at which the engine produces maximum Brake Horse Power. There is also another different point where the peak torque is produced.

My understanding is that in terms of shifting it will depend on the gear ratios of you car.
If you shift later you will get more performance BUT it will stress your engine. If you plan on always shifting at the rev limiter then your car's engine will not last very long :|

[GTO]

Hell no, shifting at redline you'll hit the rev limiter and it'll cut fuel/air to the engine to stop the engine from blowning.

EVery engine, short shift unless you want to accelerate hard then shift 1k before redline, most engine will have its tourque/power peak before redline. The only exception I can think of at the moment is Honda V-tec engine, even so redline bad idea.

[graywolf624]

Depends largely on the engine.

First for fuel economy and reliability your always going to want to short shift.

That being said for performance you want to run the car through its power band. There is a point, which youll just have to determine by driving the car where theres a range of maye 2000 rpm where most of your power occurs. Youd have to drive the car and just observe how it acts. You want to keep the car in that range for best performance.

[ViperASR]

They are all right, it depends on the engine.
On Hondas, you want to rev it almost untill the limiter, because they are engines that love to rev and make all their HP at the top end.
With larger displacement engines (like my 944) they make max HP a little above mid RPM. With these engines, it is best to keep them in the powe band. On my 944, the power band is between 4,000-5,000 RPM. It becomes pointless to push it to its 6500 redline, because the power begins to bleed off after about 5500.
On diesels, i have heard that it is really bad to rev them very high. I really dont know much about them though, have never owned one, so sorry about that.

All the other guys are right, it normally depends on the engine that you are driving.

With the Honda Type-R (nice ass car, i must say first) more revs=more power. For the fastest runs, keep it in VTEC. About 4grand for the launch, and then plant your foot on the floor board. Shirt at the indicated red-line on the tach, normally the fuel cut-off is 200 revs above that, so be careful, if u hit the cut-off, ur run is screwed. My bro has a Honda Civic SI, and we race it at auo-x, that is the reason that i know soo much about Honda engines. :fadein:

[T-Bird]

944 large displacement :lol:

This is where the mighty muscle car comes into play, you just pound that shit until redline through every gear and you'll never have a problem. The Ford 4.6 (because I'm VERY familiar with it) you can redline it in every gear and have NO problem the car makes power all the way to redline especially the '03+ Cobra motors your powerband is idle to redline.

[ViperASR]

dude, its a 2.5L in-line 4. And its not tuned to be high-revving. Most of the high-revving engines are 1.6s and 2.0s

[esbolico]

and if i want to accelerate hard from 0-100 making a little burnout.i have to accelerate until max torque and then depress cluch or i have to accelerate until max power.thanks.

[graywolf624]

The Ford 4.6 (because I'm VERY familiar with it) you can redline it in every gear and have NO problem the car makes power all the way to redline especially the '03+ Cobra motors your powerband is idle to redline.
Not to correct you tbird, but wrong.
It does have a wide powerband (the benefit of big displacemnt or even variable valve timing) and does make alot more the most outside of the band but youd be best to keep it between (I think) 3000 rpm and about 5500. Id need to look at a dino of your variation of the 4.6 to be sure.
Theoretically in a gas engine your not going to find a perfectly linear curve, some are more linear then others but there will always be a range where you get best performance.

Even you, who gets power all through the rpm range, would benefit from holding it in about a 2000 rpm range.

[Wutputt]

and if i want to accelerate hard from 0-100 making a little burnout.i have to accelerate until max torque and then depress cluch or i have to accelerate until max power.thanks.
Defenitely not at the rpm where the torque peaks.
The ideal point of shifting up depends of the engine and gear ratio's. But it will somewhere around the rpm of max power. You have to shift so you'll start at the beginning of the high torque range of your engine in the next gear.

[T-Bird]

The Ford 4.6 (because I'm VERY familiar with it) you can redline it in every gear and have NO problem the car makes power all the way to redline especially the '03+ Cobra motors your powerband is idle to redline.
Not to correct you tbird, but wrong.
It does have a wide powerband (the benefit of big displacemnt or even variable valve timing) and does make alot more the most outside of the band but youd be best to keep it between (I think) 3000 rpm and about 5500. Id need to look at a dino of your variation of the 4.6 to be sure.
Theoretically in a gas engine your not going to find a perfectly linear curve, some are more linear then others but there will always be a range where you get best performance.

Even you, who gets power all through the rpm range, would benefit from holding it in about a 2000 rpm range.

5500 is my redline :wink:

[na2o]

does anyone here know the max torque comes in exactly what RPM for the 2001 porsche carrera plz?... i shift just b4 the redline at 7000

[graywolf624]

5500 is my redline
Yes but 3000 isnt idle ;)

[Blip]

does anyone here know the max torque comes in exactly what RPM for the 2001 porsche carrera plz?... i shift just b4 the redline at 7000

Check your the specifications page in your owners manual. It will say something like < "maximum torque xxx lb/ft or Nm @ 6000 RPM" >

[gottacatchup]

You also have to take into consideration the gear ratios themselves.

Sometimes being at you're power peak in 2nd gear you will still be accelerating slow than if you remained in 1st until redline. The mechanical advantage that a lower gear gives you can sometimes overcome the fact taht the engine is not producing its maximum power.

[DeMoN]

the manual should say at what RPM you get more torque, what RPM to use for fast driving or something like that, at least thats what I read on my manual and a friends car's manual too.

[nthfinity]

5500 is my redline
Yes but 3000 isnt idle ;)
its also an automatic gearbox (im fairly sure htey didnt offer any t-birds with a manuel) anyway, in any N/A 4.6 ohc ive driven, the rev limiter is hit fairly hard... but not as hard as other cars ive driven. in my more limited experience to T-bird's... my memory sais that 3000-5000 was great, and quickly tapered off above 5000, but still pulled well enough to shift at the redline.

[T-Bird]

5500 is my redline
Yes but 3000 isnt idle ;)
its also an automatic gearbox (im fairly sure htey didnt offer any t-birds with a manuel) anyway, in any N/A 4.6 ohc ive driven, the rev limiter is hit fairly hard... but not as hard as other cars ive driven. in my more limited experience to T-bird's... my memory sais that 3000-5000 was great, and quickly tapered off above 5000, but still pulled well enough to shift at the redline.
yes sadly the Manual was only available on the V6 models but if my money situation works they way it's going now it will be swapped once the engine is taken care of. Mine seems to do great from idle to about 2000 then dies off until you hit 3000 then it hits really hard and pulls to redline. when just cruising in D with O/D on under normal acceleration the thing will shift before you hit 3500.

Also my engine has seen 100,000 beaten and mistreated miles (my dad rebuilt it at 100,000 for the hell of it.) so there could be a reason for the 700-1000 rpm lifelessness around 2grand...

[nthfinity]

5500 is my redline
Yes but 3000 isnt idle ;)
its also an automatic gearbox (im fairly sure htey didnt offer any t-birds with a manuel) anyway, in any N/A 4.6 ohc ive driven, the rev limiter is hit fairly hard... but not as hard as other cars ive driven. in my more limited experience to T-bird's... my memory sais that 3000-5000 was great, and quickly tapered off above 5000, but still pulled well enough to shift at the redline.
yes sadly the Manual was only available on the V6 models but if my money situation works they way it's going now it will be swapped once the engine is taken care of. Mine seems to do great from idle to about 2000 then dies off until you hit 3000 then it hits really hard and pulls to redline. when just cruising in D with O/D on under normal acceleration the thing will shift before you hit 3500.

Also my engine has seen 100,000 beaten and mistreated miles (my dad rebuilt it at 100,000 for the hell of it.) so there could be a reason for the 700-1000 rpm lifelessness around 2grand...

i wouldn't blame that on the engine, but rather the torque converter, its the same story in many automatics, mine included.

[basy]

For the diesels is better to change at 4000rpm, but for the Type-R is not recomended to change below redline for maximum performance. At a drag race if you change at the maximum rpm you obtain maximum performances.