Does rear end gers affect RWHP?
Safety Car
Joined: Jul 2002
Posts: 4,174
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From: Florida
Re: Does rear end gers affect RWHP? (hubes)
quarter mile times, and spirited take-offs from stoplights ! Keeps the car in its powerband (rpms) with numerically higher gearing ratios. More effective at using the horsepower you have :thumbs:
Race Director
Joined: Jul 2002
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From: Psychizogeographic -- Knoxville and Houston
Cruise-In IV Veteran
St. Jude '03-'04-'05-'06-'07-'08
Re: Does rear end gers affect RWHP? (Killrwheels)
quarter mile times, and spirited take-offs from stoplights ! Keeps the car in its powerband (rpms) with numerically higher gearing ratios. More effective at using the horsepower you have :thumbs:
Drifting
Joined: Jul 2000
Posts: 1,818
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From: SoCal
Re: Does rear end gers affect RWHP? (Topless)
Yes, it will change RWHP reading. Higher gear ratios usually consume a little more power before it makes it to the wheels. I honestly don't know the science behind it, but I beleive its due to more friction and the fact you are spinning stuff up faster (fighting against more rotational inertia?).
I dont think its more than a few rwhp difference you're talking about so its not anything to worry about.
I dont think its more than a few rwhp difference you're talking about so its not anything to worry about.
Melting Slicks
Joined: Jun 2001
Posts: 2,743
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From: Davie Florida
Re: Does rear end gers affect RWHP? (Oyea)
I'm pretty sure it doesn't change RWHP, but does give you more RWTQ.
You don't actually loose any HP when you go to a numerically higher rear. The dyno just gives a lower reading with big gears.
Le Mans Master
Joined: Apr 2001
Posts: 8,133
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From: Ex-SF Bay Area; now happily Denver area
Re: Does rear end gers affect RWHP? (Mitch C)
No, it doesn't. From the email I got from Paul at Tazzo (the performance meter), he says that instant hp is calculated by weight x acceleration x speed. The higher gear ratio increases acceleration but it happens at a lower speed and these offset each other in the measured calculation. He has some interesting observations, especially how professional racers look at things. For instance, he said that they don't look at the maximum horsepower but instead, when tuning a car, they try to minimize the time between two rpm points. His performance meter also measures average horsepower between two points because it tells what is happening over the entire powerband, not just at one point in time.
On another post long ago there was a lot of input on this subject and I think the final conclusion was that going from 3.42 gears to 4.10 gave a 20% increase in thrust, which would give a "virtual, though unmeasured" 20% increase in horsepower. In other words, you would get the effect of 20% more horsepower but would be unable to measure.
In the end, though, the 4.10's are just a kick in the pants, and for me, that's half the fun.
Hope this helps.
On another post long ago there was a lot of input on this subject and I think the final conclusion was that going from 3.42 gears to 4.10 gave a 20% increase in thrust, which would give a "virtual, though unmeasured" 20% increase in horsepower. In other words, you would get the effect of 20% more horsepower but would be unable to measure.
In the end, though, the 4.10's are just a kick in the pants, and for me, that's half the fun.
Hope this helps.
Moderator
Joined: Jan 2001
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From: Charlotte NC
Cruise-In IV Veteran
Cruise-In V Veteran
St. Jude Donor '08-'25
Re: Does rear end gers affect RWHP? (Topless)
quarter mile times, and spirited take-offs from stoplights ! Keeps the car in its powerband (rpms) with numerically higher gearing ratios. More effective at using the horsepower you have :thumbs:
But no, it doesn't actually change the amount of horsepower. It just feels that way. :D
But no, it doesn't actually change the amount of horsepower. It just feels that way. :D
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Melting Slicks
Joined: Mar 2001
Posts: 2,369
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From: New Milford CT
Re: Does rear end gers affect RWHP? (hubes)
If the question is "Do different gear ratios affect the MEASURED rwhp on a dyno?" Then I believe that the answer is Yes they do!
If a 3.42 ratio was used for a pull on the dyno, and then the gears were quickly changed to a 4.10 ratio, then I believe the new dyno reading would be 5 to 10 rwhp LOWER than before.
The engine hp did not actually change however. It is lower only because of the way the dyno measures rwhp. The 4.10 gears allow the dyno drum to be spun up to speed in less time, and this causes the rwhp reading to be slightly wrong (lower) compared to the 3.42 reading.
So it is just like doing the dyno run in 3rd or 5th, you will not get the correct reading.
If a 3.42 ratio was used for a pull on the dyno, and then the gears were quickly changed to a 4.10 ratio, then I believe the new dyno reading would be 5 to 10 rwhp LOWER than before.
The engine hp did not actually change however. It is lower only because of the way the dyno measures rwhp. The 4.10 gears allow the dyno drum to be spun up to speed in less time, and this causes the rwhp reading to be slightly wrong (lower) compared to the 3.42 reading.
So it is just like doing the dyno run in 3rd or 5th, you will not get the correct reading.
Team Owner
Joined: Sep 1999
Posts: 20,054
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From: Swansea IL
Re: Does rear end gers affect RWHP? (CJS)
If the question is "Do different gear ratios affect the MEASURED rwhp on a dyno?" Then I believe that the answer is Yes they do!
If a 3.42 ratio was used for a pull on the dyno, and then the gears were quickly changed to a 4.10 ratio, then I believe the new dyno reading would be 5 to 10 rwhp LOWER than before.
The engine hp did not actually change however. It is lower only because of the way the dyno measures rwhp. The 4.10 gears allow the dyno drum to be spun up to speed in less time, and this causes the rwhp reading to be slightly wrong (lower) compared to the 3.42 reading.
So it is just like doing the dyno run in 3rd or 5th, you will not get the correct reading.
If a 3.42 ratio was used for a pull on the dyno, and then the gears were quickly changed to a 4.10 ratio, then I believe the new dyno reading would be 5 to 10 rwhp LOWER than before.
The engine hp did not actually change however. It is lower only because of the way the dyno measures rwhp. The 4.10 gears allow the dyno drum to be spun up to speed in less time, and this causes the rwhp reading to be slightly wrong (lower) compared to the 3.42 reading.
So it is just like doing the dyno run in 3rd or 5th, you will not get the correct reading.
Tom
Thread Starter
Burning Brakes
Joined: Jul 2002
Posts: 1,130
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From: Nova Scotia
Re: Does rear end gers affect RWHP? (CJS)
If the question is "Do different gear ratios affect the MEASURED rwhp on a dyno?" Then I believe that the answer is Yes they do!
Race Director
Joined: Aug 1999
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From: GARDENA Ca, State Of Konfusion
St. Jude Donor '05
Re: Does rear end gers affect RWHP? (hubes)
If the question is "Do different gear ratios affect the MEASURED rwhp on a dyno?" Then I believe that the answer is Yes they do!
That was the question, and that was a very good answer. It's good to know that they won't change the measured HP by very much.
That was the question, and that was a very good answer. It's good to know that they won't change the measured HP by very much.
[Modified by wallstAL, 11:19 AM 7/13/2003]
I ♥ My Corvette
Joined: Apr 2003
Posts: 556
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From: Virginia
Re: Does rear end gers affect RWHP? (Oyea)
I'm pretty sure it doesn't change RWHP, but does give you more RWTQ.
gregg "engineer"
'01 Z06 (354 rwhp)
