HP/Torque Multiplication/Gearing Question

Paolo Castellano

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Hello all,I am seeking the answer to a question I have been pondering for a long time now. Let's take the 3.73 gear and divide it by 3.07. This yields a 21.5% HP and Torque multiplication for any gear at any given RPM. Now will a car with a 3.73 gear that is relatively stock, maybe 440 RWHP and 480 RW LBS/FT, accelerate like a car with 21.5% more power(With the stock 3.07) like 535 RWHP and 583 RW LBS/FT? Has anyone ever put two cars with these gearings and power levels side by side? Mathematically these cars should have similar rates af acceleration and tire spin through the gears even though the 3.73 car's gears would be shorter. What do you all think? Paolo
 

treynor

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Paolo,
Actually, gears multiply torque and divide velocity. They do not directly affect HP. Comparing a car with 20% higher gearing, you would find that it from the same starting speed it accelerates 20% more quickly but has to shift to the next higher gear 20% earlier. Consider an analogous case: you race two cars from a dead stop, but one is in 1st gear and one is starting out in 2nd. The car starting in 1st will accelerate more quickly out of the hole (better gearing) but will need to shift at about 50 MPH, while the car starting in 2nd won't need to shift until about 80 MPH.
Once you're out of 1st gear, taller rear gears change your shift points but do not otherwise affect accleration. For example, at 65 mph a Viper with 3.73 rears will be in 3rd gear, while with stock 3.07s it would still be in 2nd. The stock car will outaccelerate the modified car from 65 - 83 mph, then lose ground from 83 - 90 (or so), then gain ground from 90 - 110 (3rd vs modified in 4th) etc.

Clear?
 
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Paolo Castellano

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Ben I have done all the HP/Torque multiplication calculations for exactly what you are describing and I understand what you are saying, but with the additional gear, just like the concept of the integral in calculus, with an extra gear on the way up through the gears, you would hypothetically spend more time/MPH in the maximum HP and Torque band of the motor, No?
I Ran Chuck '97 GTS when I had an aftermarket trans that had a 2.21 1st gear, 1.43 2nd,1.17 3rd, 1.0 4th. My car was making 467 RWHP at the time and his car was stock making about 417 RWHP at the time(Even though he had not dynoed his car yet at the time). He pulled me through 1st,2nd and 3rd. I just thought his car was fast at that time until a stock 1999 RT/10 spanked me at the light. I ordered the gears to match the stock trans ratios the very next day(Which also hapened to be the ones I originally wanted with the trans but mysteriously never were put in there). Fast foreward to several months in the after I had the proper gears put in the trans and Chucky got Belanger headers/no cats and 3" cat back exhaust=> now his car was definitely faster than it was with the stock exhaust, right? But when we raced, now I was faster every single time with the gears that were very similar to the stock T-56 gears. The conclusion I had drawn at the time was that there is definitely something to the whole HP/Torque multiplication concept which is what led to the original question of this post. I think the only way to tell would be a real world application where someone with a relatively stock car with a 3.73 rear end gear runs against a 540 RWHP car with the 3.07 Gear. Can someone do this practical application and let us all know what happens? Paolo
 

treynor

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Consider -- if this were really the case, then (for example) you could get higher trap speeds in the 1/4 mile by switching to a 3.73 rear end. I've never heard of anyone picking up significant MPH through a rear-end swap, all though they can lower their ET because they are accelerating more quickly through that crucial first 60'. On the other hand my RT, back when it had a mere 515 RWHP, trapped at 124 MPH in the 1/4 -- faster than ANY stock Viper has ever trapped, regardless of gearing.
 
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Paolo Castellano

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by treynor:
Consider -- if this were really the case, then (for example) you could get higher trap speeds in the 1/4 mile by switching to a 3.73 rear end. I've never heard of anyone picking up significant MPH through a rear-end swap, all though they can lower their ET because they are accelerating more quickly through that crucial first 60'. On the other hand my RT, back when it had a mere 515 RWHP, trapped at 124 MPH in the 1/4 -- faster than ANY stock Viper has ever trapped, regardless of gearing.

<HR></BLOCKQUOTE>

Ben, I think that the 1/4 mile is really too short with all of the variables of who hooks up better, who has a better reaction time/etc... What I was thinking of was a 50-60 MPH rolling start all the way up to top speed so all of the variables would be removed and we could have the answer to mt question. Do you know of any two people with cars like I am describing that could run the rolling start? Paolo
 
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Paolo Castellano

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Tom, F&L GoR:
Good reading here:

SoCal VCA gear article

<HR></BLOCKQUOTE>

Tom, that is a great article! The reason I am considering this 3.73 is because there is now the prospect of STILL having the top end speed with the higher torque multiplication through the stock 1st-4th gears. Paolo
 

YellowSnake

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What's up Paolo. The question I think you really want to ask is, "How do I get my car to do more than 200 MPH?"

I have your answer. Strap this onto the back of your car...

You must be registered for see images
 

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