Thread: Best gear for 1/4 mile

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I was kinda making a joke, unless I'm over looking something, you are right about the gears, but the hp and the speed don't match. 350- 400 hp will go 120 mph in the 1/4 mile, @6000 rpm's with a 4:10 gear, so all I was saying is if I had 700 hp and only running 120 mph id be probably looking a new driver. here is a few cal., see if they help. i dont believe the example you gave could ever happen. the idea is getting the right gear for the rpm range of you cam. you get the max. hp out of your motor the mph will fall in place.

"As an example a 71 nova with 700hp, 6500rpm chip, 350 trans, 4.11 gear and 28 inch tire. At the quarter he is at 6500 rpm. People (that don't know) say he needs some 4.56 gears, but that would slow him from 132mph (or so) to around 119 mph. But i don't think it will be any faster would it?"
http://home.tampabay.rr.com/1bking/c....htm#calc_disp

http://www.richmondgear.com/101032.html

Originally posted by techinspector1
Mike, you're a day late and a dollar short buddy.....he's running 132 mph now and if he changed to a shorter gear while running the same rpm, he'd slow down to 119.

In order to go quicker/faster with a stiffer gear, he'd have to change the engine rpm's through the lights.

im always a day late and a dollar short, but if that 700 hp motor isn't running but 119 mph in the 1/4 mile, im gonna out run it.

"the car" is 350 twin turbo 10psi, 350 trans, 4.11 gear, 6500RPM chip, 28 inch slicks, and about 9.8 @134 1/4. If It had 4.56 gears then 6500 rpm the car would only be 119 mph, with 5.88 gear at 6500 rpm it would only be at 92 mph. 3.50 gear if he could get up to 6500 rpm would be 155 mph. A 10,000HP motor in that setup would be the same MPH.

Originally posted by chevydrivin
"the car" is 350 twin turbo 10psi, 350 trans, 4.11 gear, 6500RPM chip, 28 inch slicks, and about 9.8 @134 1/4. If It had 4.56 gears then 6500 rpm the car would only be 119 mph, with 5.88 gear at 6500 rpm it would only be at 92 mph. 3.50 gear if he could get up to 6500 rpm would be 155 mph. A 10,000HP motor in that setup would be the same MPH.

I understand that, but they are not realists(sp) #'s. there is a ball park that you should be in. the starting place is what ever the cam co. says the rpm range is, and after that you would have to go to the track and try it. if I was doing it id know what the cam called for, then I'd use the cal, I gave you and pick the tire size and the gear ratio I thought I needed and that's what id start with, if you cam is calling for 6000 rpm in the 1/4 and you're with in 3-400 rpm's of that, that's about all you can do. if you're in your cam setting, then it would only hurt you to change it either way.

What numbers are not realistic?

10,000 hp motor running 92 mph. in the 1/4 mile. i must be missing something. there are certain expectations of that a motor with a certain amount of hp turning a certain rpm's should be able to do in a 1/4 mile. there is a standard that we all go by, and try to beat. if you have a 200 hp motor you will need a dif. gear to get it to 6000 rpm's in a 1/4 mi. than a motor with 700 hp, if you're trying to get the max. out of the motor.

Originally posted by lt1s10
10,000 hp motor running 92 mph. in the 1/4 mile. i must be missing something. there are certain expectations of that a motor with a certain amount of hp turning a certain rpm's should be able to do in a 1/4 mile. there is a standard that we all go by, and try to beat. if you have a 200 hp motor you will need a dif. gear to get it to 6000 rpm's in a 1/4 mi. than a motor with 700 hp, if you're trying to get the max. out of the motor.

I think we are both missing somthing. You said the numbers I metioned were not realistic numbers and I was wondering what you ment. I am saying that i think his setup is the best he can do, because his cam is for 6500 and that is what he is at at the quarter. I am aware that less power needs more gear, thats not what I was getting at.

if i was looking at the # you gave, id have to say something is wrong with the over all pic. if its a 700 hp motor, in a 3000 lb. car, turning 6000 rpm's and if is not running 150 mph, you got to find out why. changing gears won't fix it. 700 hp, 6000 rpm's and 150 mph, now you got sometyhing to work with. you start messing with the gears now and you can tell where you are gaining or loosing, but if you're turning the rpm's you want then its no need to chande it.

The numbers I gave you are actual numbers. The motor is around 700 hp setup for 6500 RPM. SO the motor and drive shaft turn 6500 RPM. The Pinion turns 6500RPM so the 4.11 gear means the axle turns 1581.5 RPM which means the wheel turns 1581.5 times. A 28 inch tire covers 695,231 ft in a minute divided by 5280 ft/mile equals 132 MPH. No matter what the horsepower is. A 6500 rpm motor/28"tire/4.11gear/will only go 132 mph in the quarter is what I am saying. If the 700 Hp motor should be around 150MPH then he needs to try a higher gear right? around a 3.50 gear maybe, but then will he get to 6500rpm.

. . . around a 3.50 gear maybe, but then will he get to 6500rpm?

Good question. You're correct in one way. If the motor is limited to 6500 RPM, it will never go faster than 132 in the quarter. Lower the gearset to 4.56 AND keep the limiter at 6500 RPM, the car may rush to about 120 and flatten out. However, it's not impossible for the ET to drop when the MPH drops. That's where horsepower comes in.

Minimizing the ET in a car with this configuration takes a combination of things, and horsepower does matter. You need to minimize ET, then take the top speed that goes with it. If you want to go 150 and keep the rev limiter - and you have the horsepower (which seems to be the case) you do need a higher gear. However, you may have to "fiddle" with other stuff also. For example, if it's an automatic car, you can work with the converter to provide a little more slip to avoid bogging. If it's a four-speed car, you can go to work with the lowest gear and the spacing between the gears or go to a five-speed.

You've just painted a good picture of why many people go with a higher revving motor.

.

how does your wheel turn the same speed as the rear end, should be a lower number, tires are the final ratio, they won't spin at the same RPM as the axles, that is why they can effect a cars performance,

Matt,

You better re-think that one. The tires are bolted to the axles (lug nuts, remember?). If the tires don't rotate at the same speed (RPM) as the axles, you just broke something.

The diameter of the tire does affect the acceleration and top speed, but only because a small tire travels less distance per rotation than a larger one.

Originally posted by Henry Rifle
Matt,

You better re-think that one. The tires are bolted to the axles (lug nuts, remember?). If the tires don't rotate at the same speed (RPM) as the axles, you just broke something.

The diameter of the tire does affect the acceleration and top speed, but only because a small tire travels less distance per rotation than a larger one.

yeah, that makes sense

Originally posted by Matt167
yeah, that makes sense

Unless you got dimm spinnin rims. LOL

Originally posted by chevydrivin
Unless you got dimm spinnin rims. LOL

or a broken axle