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Old Dec 21, 2007 | 09:25 AM
  #11  
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Originally Posted by mikegarrison,Dec 21 2007, 10:13 AM
No, it is not.

At any given speed, your acceleration is determined by your available power, your weight, and the drag. Gearing directly affects none of those.

Keep the engine in the powerband and you'll get about the same acceleration no matter what your final drive ratio is.
doesnt sound like you've ever played wiht gearing.


look on youtube for stock s2000 races against 4.77 final drive s2000's. the 477's a;lways pull. tehy hit their powerband sooner and stay there, but its about getting there sooner
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Old Dec 21, 2007 | 09:33 AM
  #12  
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Originally Posted by street_ruler,Dec 21 2007, 10:25 AM
doesnt sound like you've ever played wiht gearing.
Sure I have. I call it "shifting".
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Old Dec 21, 2007 | 09:38 AM
  #13  
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[QUOTE=street_ruler,Dec 21 2007, 10:24 AM] yes it does have more tq.
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Old Dec 21, 2007 | 09:42 AM
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while awaiting a physics lesson...


fltsfshr
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Old Dec 21, 2007 | 09:47 AM
  #15  
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Originally Posted by fltsfshr,Dec 21 2007, 10:42 AM
while awaiting a physics lesson...
I've given the physics lesson before. Not planning to do it again, since it never gets through.

For some people mechanical advantage is just a big chunk of mysterious magic.

But in case anybody wonders how much acceleration the gears really give them, try the gears with the engine turned off....

The way to correctly choose the gearing of a car is described very well in Paul Van Valkenburgh's Race Car Engineering. You can have a final drive gear that is too tall for optimum. You can have one that is too short for optimum. But the reasons behind it are not the reasons generally given in these "how sweet would gears be?" threads.
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Old Dec 21, 2007 | 10:00 AM
  #16  
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Fred is the man. I still have his old Racecar engineering articles.
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Old Dec 21, 2007 | 10:36 AM
  #17  
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Originally Posted by mikegarrison,Dec 21 2007, 10:33 AM
Sure I have. I call it "shifting".
i meant like the difference in acceloration between a 4.10 rear end and a 2.83 rear end. the 410 is much quicker.

as a bit of proof, i did that very swap in my mustang, i went to a 4.1 rear end and it was worlds faster than the old tired gasmileage rearend that was in there it was a 2.8X (i think it was 2.83 i just cant remember off the top of my head)


and even with the shifting comment you should agree that acceloration in 1st gear is faster than while in 6th gear
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Old Dec 21, 2007 | 10:48 AM
  #18  
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Originally Posted by street_ruler,Dec 21 2007, 11:36 AM
and even with the shifting comment you should agree that acceloration in 1st gear is faster than while in 6th gear
It is if you are going 15 mph. It's not so good if you are going 125.
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Old Dec 21, 2007 | 11:38 AM
  #19  
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Originally Posted by street_ruler,Dec 21 2007, 10:24 AM
yes it does have more tq. the nubers on a dyno are adjusted to take into account gearing. when it comes to physical power at the wheels the tq is actually like 1400lbs due to gearing. thus why tractors are like 14:1 gear ratios
no...i think you are incorrect.

the engine produces a certain amount of torque, irregardless of gearing...

you can't change the amount of torque an engine produces by changing the gears.
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Old Dec 21, 2007 | 11:41 AM
  #20  
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Originally Posted by mikegarrison,Dec 21 2007, 11:48 AM
It is if you are going 15 mph. It's not so good if you are going 125.
acceleration can be compared amongst different velocities (rates of speed), ie. 15mph vs. 125mph.

and the acceleration in first gear would be higher than the acceleration in sixth gear, given that you're comparing the same power band (6k rpm through 9k rpm)...in 1st versus 6th gear comparison.
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