Optimum Point to change Gear

Whens the best time to change gear in a manual car? Is it at just after your peak power (if you're lucky enough to have a dyno graph for your engine) or is it somewhere a bit later on? I need to settle an argument with my friends..

[FYRHWK1]

the best time to shift is when the force of the gear your in becomes lower then the force you would get by moving up a gear. if you have a 6500 redline but at 6000 in say 2nd gear, your force would be less then say 4000 in 3rd, then you should shift, its got alot to do with gear ratios redline and powerband. also just because your power starts to drop off doesnt mean you should shift then, the mechanical advantage of the taller (lower # gear, 2nd instead of 3rd) can still make you accelerate faster then the nex gear up even if you're in its powerband.

[BeEfCaKe]

Really depends on your car.

[gustavo]

you should up gears before peak power, why would you like to stress your engine and waste gas ? Tell me please your thread has intrigued me a lot...

Gustavo.-

[Grendel]

Originally posted by gustavo
you should up gears before peak power, why would you like to stress your engine and waste gas ? Tell me please your thread has intrigued me a lot...

Gustavo.-

Because by stressing your engine and wasting gas, you get to go faster... and have more fun... :P

I just shift when it sounds like the engine is making more noise than power... my tach is a really funky digital one, so I just shift by sound...

Last night I did find out that I was shifting from 4th to 5th way too soon... I was shifting into 5th when my speedo topped out (85mph), I looked at the tach and realized i still had another 1k or so rpms before the redline

-Grendel

[higgimonster]

I am assuming you are looking to go fast and this isn't for casual shifting. For one, i absolutly hate this question. I have had to teach all of my friends and 2 of my girl friends. each one asks when they should shift and my only answer is when you damn well please. If you want acceleration, keep it in gear to very near redline (you don't want to shift too early and end up with the next gear starting before the power). Just learn your car and it's gear ratrios and you will know when to shift. There is no rule for when to shift, so don't ask about it.
Sorry if i sound like i am ranting, i just hear this question too damn much.

Grendel, you seem to have hit the nail on the head.. I don't mind stressing my engine (in fact the only way to get decent performance out of my car is to wind it up to 7000rpm in every gear cos it doesn't really wake up 'til 5000) and I don't mind wasting petrol. I wanna go fast. Which makes me wanna ask another question but I'll leave that for now..

FYRHWK1's answer pretty much confirms what I thought. You don't wanna change 'til the imaginary line drawn across your power curve (or some clever amalgamation of power and torque in one curve if thats possible ) would be horizontal..

I will arm myself with this information and go get that beer they owe me now..

Cheers guys..

[Holyterror]

I'm not sure how much precision you need or how much work you're willing to go to, but something in the next few paragraphs will probably get you as close as you'd want to be.

The first thing you should do is ask this same question in a forum dedicated to your car. The guys there will have the best idea of when you should shift.

Use a program like CarTest to find your optimal shift points (not to mention your approximate 0-60 and 1/4 mile ET). If you are not planning on racing, go no further. This is good enough for you.

If you are more serious about it, then go do a few dyno runs and input the exact hp and torque @ RPM into CarTest so it'll have more accurate power and torque curve to use. You can even do stuff like time how fast your engine decelerates and put that in. Once you're satisfied with the level of accuracy, you can either stop there or move on to the final step.

Go to a 1/4 mile track, use the CarTest shift points, and see what happens. Now vary the shift points a little, based on instinct. See if your times get better or worse as you alter the shift points. Ask the other guys at the track what they think. It will take a lot of trial and error to get it perfect, but this is how the pros do it.

[Steel]

goodbye, synchros..

[|Banchi1O5|]

Actually It depends on your car

If the company that produced your car were aiming it as a performance orianted car they absolutely make sure that going all the way to redline before shifting will produce the fastest acceleration.

On the other hand (more than likely) - your car's gearing wasnt spent a massive amount of time on - and it prolly will require different shift points depending on what gear you are in

ie
1st to 2nd
6500

2nd to 3rd
5900

3rd to 4th
6750
....
and so on

You will really just have to go find what feels right
Sorry those engineers dont spend more time making things simpler

[Holyterror]

Totally OT, but where did you find the picture in your sig? That's hilarious!

[|Banchi1O5|]

OT - do you mean off topic?

i got my sig from Beaterz.com i believe