Mechanical Advantage and Acceleration.

Tech questions that don't fit above forums

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Racer Roy
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Mechanical Advantage and Acceleration.

Post by Racer Roy » Mon Jul 18, 2005 8:23 pm

Hey guys:
I have been pondering something that I hope I can find an answer to here.
Some background... I race a 84 Grand Prix stock car, with 2.73 rear gears and use first gear (2.52) in a TH350, for a 6.87 overall ratio.
This is competitive, but I started wondering if switching gears would get me better acceleration off the corners.
Would I see better acceleration by switching to, for example, a 4.10 rear gear and used a Saginaw three speed in second gear (1.68 )?
This gives me the same 6.87 overall ratio, but the mechanical advantage is higher in the rear end, and less in the transmission.
Is this valid, or does the final, overall gear ratio determine acceleration regardless how I come to it?

Any opinions?

Thanks

RR

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BillyShope
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Post by BillyShope » Mon Jul 25, 2005 8:25 am

When I was a kid, back in the fifties, I worked 8 hours a day making performance calculations for Chrysler. All the gear efficiency numbers I saw then would force me to the conclusion that you're far better off getting all your gearing with the ring and pinion. While the change you're suggesting would be an improvement over your present setup, I strongly recommend an axle ratio that will allow you to run your transmission at 1:1. Yes, I realize 6.87:1 is pushing the limits on availability, but I'd look into it. If you can't get there, try combinations using 3rd gear in a close ratio four speed.

Realize, of course, that any performance gain is not going to be substantial and that it might be advisable to direct your financial resources elsewhere.

jlw
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Post by jlw » Fri Dec 09, 2005 2:04 pm

Take a look at this software - Might be of use.

http://www.enginemanagementsystems.com/gearsplit.html
ECTA

Racer Roy
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Post by Racer Roy » Fri Dec 09, 2005 7:33 pm

Interesting...

T RICK
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Post by T RICK » Mon Dec 19, 2005 9:48 pm

The problem with using any gear except high gear with a three speed is the load to the cluster and case. This may cause transmission failure or shorten the life span. It also is case of loss power due to drag of more gears involved. Best bet is to change the rear gears.

Rick

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