Where Do You Set Your Rev Limiter?

[DarkSunrise]

Originally Posted by paulca

Remember that torque does nothing unless it "operates over rotation".

Throwing units out of it for simplicity.

Power output = Torque * RPM.

So DarkSunrise your method needs to take account of the drop in RPM the torque is applied at. (As above if you just forget the units and multiply torque directly by RPM is easiest). If you actually want "Watts" or "Horsepower" there are a few more complexities.

Examples....

200Nm torque @ 3,000rpm == 100Nm torque @ 6,000rpm.
200Mn torque @ 6,000rpm > 220Nm torque @ 4,500rpm.

In terms of power output, which is the energy transferred to the car in the form of momentum. aka Speed.

In terms of calcuating power, that's correct. Power is greater when a given amount of torque is applied at a higher RPM.

Maybe I'm mis-understanding you, but I'm not trying to calculate power, I want to compare torque to the ground in two different gears at the same vehicle speed (i.e., shift point).

If 1st gear is putting down 2400 lbs-ft of torque at 7000 RPM, and 2nd gear would put down 1700 lbs-ft of torque at 4500 RPM, you would want to ride out 1st gear for as long as that torque value is above that in 2nd for the given vehicle speed.

[Roadcone]

Originally Posted by LavosTRD

And people wonder why their transmissions grind....

huh?

[chrisl]

Originally Posted by DarkSunrise

The way I had always calculated it is, you have to compare torque to the ground (i.e., multiplied through the gearing) in the two gears. So to determine the shift point for the 1-2 shift, you would compare torque to the ground in 1st gear at 7000 rpm vs. torque in 2nd gear at 4500 rpm. Then 7100 rpm vs. 4600 rpm. Etc.

When torque to the ground in 2nd gear exceeds the same in 1st, that is your optimal shift point. If 2nd never exceeds 1st, then you should shift at redline.

Because of the way gearing is setup in most cars, it ends up that the optimal shift point is at/near readline in the lower gears, but gets lower as you go up the gears.

This should give you the exact same results as the power method I described - torque to the ground will be the same at a given speed if power is the same.

[bkblitzed]

7400

[Chicken Patty]

I think a lot of it has to do with where you make the power. If you make power All the way to 7400-7500, then around there is where you'll want it. Mine is 7500 and shift light at 7300.

[DarkSunrise]

Originally Posted by chrisl

This should give you the exact same results as the power method I described - torque to the ground will be the same at a given speed if power is the same.

Interesting. I sort of suspected this (and it makes for a much easier method of calculating shift points than I had been doing), but good to hear confirmation on this.

[Davey]

Originally Posted by Roadcone

huh?

If I understand correctly he bought a budget sport coupe so he could set the shift light at 3,000 RPM for the best possible gas mileage and to keep from exceeding the 55 mph speed limit while he pretends he's driving a Corolla.

[Roadcone]

Originally Posted by Davey

If I understand correctly he bought a budget sport coupe so he could set the shift light at 3,000 RPM for the best possible gas mileage and to keep from exceeding the 55 mph speed limit while he pretends he's driving a Corolla.

i was referring to the grinding transmissions issue. these things seem to have a pretty decent feeling gearbox.

[Davey]

Originally Posted by Roadcone

i was referring to the grinding transmissions issue. these things seem to have a pretty decent feeling gearbox.

*Some* people have had issues with grinding into 2nd and 5th (maybe other gears but those are the ones I see the most.

Mine works great so far. I agree, best trans I've shifted since my S2000.

[Roadcone]

2nd gear on mine has had a light grind since about 50 miles in. i think i made about 10 2nd gear shifts in that time. i had a 89 mile drive home after my initial test drive... you can powershift it fine with zero issues and high rpms are fine but normal around town shifting seems to be an issue for it somewhat... i just double clutch it and its fine usually

[Fortis]

6500. I find myself going way too fast shifting at redline in any gear over second