cloud

ok, if the purpose of a tranny is to keep the engine at peak torque. what's the calculation for choosing gear ratio's based on X torque between say 4-5k? I have a low boost setup on a stock sohc zc and I'm trying to figure out the best tranny. I've never taken this thing to the dyno, so I have no idea when it's actually making max toque, but if I did. I've seen a lot of calculators that tell you the mph, but I don't see the relevance, if your not adding your torque curve to the equation?
I'm not sure what's even available as of gears for singles if you knew this, but there's a couple FD's and of course tires to mess with it.

hell, some engineers came up with the numbers on stock engines......

0b00st0

There are a lot of considerations that go into choosing gear ratios. Traction and other dynamics go into as well.

For a purely output based calculation though It's based on the horsepower production, not torque.

The calculations involve integrating the horsepower curve and finding the rpm range that produces the largest integral, which is simply the area under the curve.

miss-piggy

Zuh? If you look at torque or look at horsepower, your conclusions will be exactly the same. Everything else I agree with, but I don't see why you can't get a valid analysis looking at torque over an rpm range.

Bone1

CRX Si has the best 1-4 ratios, maybe add a 3.083 1st.

FD does NOT effect the rpm gear split between shifts.

You whill find most NA motors have a 2000 rpm powerband, you want the 2-3-4 gears to keep it in that powerband.

0b00st0

No they will not. Torque is not a unit of energy. The area under the horsepower curve will show maximum energy production.

For lower torque made at higher rpms, if the horsepower is higher, then you can always take advantage of gearing to make more torque at the output.

Bone1

MADMAX, you'd better reread your post

t_cel_t

you are gonna want to look at your torque and figure out where you make, say 90% of peak, and if that is an acceptable range to have a gear last. find out how long that lasts and then get the gears that will split that much.

hp dont mean jack ----, 200ftlbs at 4000 has the same acceleration as 200ftlbs at 6000

0b00st0

100% wrong and only assumes the same gear ratios. This conversation is about ideal gear ratios.

Let assume a 1:1 gear ratio on the 200ftlbs @ 4000 (152hp). That's 200ftlbs to the wheel at speed Xmph. For the 200ftlbs at 6000 (228hp) at the same speed Xmph you are going to have a 1.5:1 gear ratio, which now translates into 350ftlbs at speed Xmph. F=ma buddy. Simple physics. Higher force (torque) equates to faster acceleration.

See why horsepower is what matters in this type of calculation? You can always have a better gear ratio with higher rpms. The whole premise to revving higher and making torque at higher rpms.




Quit being a moron bone. I know exactly what I said.

t_cel_t

what i was saying is that if your motor puts out a flat 200ftlb curve from 4000 to 6000, your rate of acceleration is going to be the same (actually goes down with increased air drag). so if you got a solid 2000rpm of flat torque and its your peak then you would get gears that do a 2000rpm split and shift at 6000 every time.

Bone1

2000 rpm powerband.........I wonder.......maybe........a D15.......will it?




Now couple that with my "perfect" 1-5 gearing, look at the gear splits
1st 0000 7000 35.39
2nd 4801 7000 51.60
3rd 4959 7000 72.84
4th 5544 7000 91.97
5th 5766 7000 111.66