Why do numerically higher gears lower your dyno #'s?
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 2,375
Likes: 39
From: Charlotte NC
Why do numerically higher gears lower your dyno #'s?
I'm probably asking for a complicated explanation that I won't understand.. but why is that true?
I would think that a car with 4.11's as opposed to 3.73's (example) would have more torque (?) to turn the rollers on a dyno, thereby producing higher hp/tq numbers? :confused:
[Modified by MyFirstCorvette, 8:00 PM 8/7/2003]
I would think that a car with 4.11's as opposed to 3.73's (example) would have more torque (?) to turn the rollers on a dyno, thereby producing higher hp/tq numbers? :confused:
[Modified by MyFirstCorvette, 8:00 PM 8/7/2003]
Race Director
Joined: Sep 1999
Posts: 12,437
Likes: 919
From: CONCORD NC
Re: Why do numerically higher gears lower your dyno #'s? (MyFirstCorvette)
it's not that complicated. Any time you accelerate faster (as you would with a higher ratio) you have more centrifugal losses. That is one of the reasons you use 4th gear instead of 3rd or 2nd on the dyno. It should be a rather small difference, however.
Burning Brakes
Joined: Feb 1999
Posts: 1,165
Likes: 1
From: San Jose CA
Re: Why do numerically higher gears lower your dyno #'s? (MyFirstCorvette)
I'm probably asking for a complicated explanation that I won't understand.. but why is that true?
I would think that a car with 4.11's as opposed to 3.73's (example) would have more torque (?) to turn the rollers on a dyno, thereby producing higher hp/tq numbers? :confused:
[Modified by MyFirstCorvette, 8:00 PM 8/7/2003]
I would think that a car with 4.11's as opposed to 3.73's (example) would have more torque (?) to turn the rollers on a dyno, thereby producing higher hp/tq numbers? :confused:
[Modified by MyFirstCorvette, 8:00 PM 8/7/2003]
Since the formula for hp = torque x rpm/5252 there should be no difference.
But here it is where davidfarmer's response comes in plus the increased friction of the higher gears = less hp.
Hope this helps
Roger
:cheers:
Drifting
Joined: Sep 2001
Posts: 1,421
Likes: 3
From: Memphis Tn
Re: Why do numerically higher gears lower your dyno #'s? (MyFirstCorvette)
:iagree: Real simply, the smaller rearend gear(higher numerically) gets you a quicker launch and into your powerband faster. There are alot factors that can only be measured at the track such as clutch slip/stall and such that will help a lesser powered car win. :steering:
Thread Starter
Melting Slicks
Joined: Jul 2002
Posts: 2,375
Likes: 39
From: Charlotte NC
Re: Why do numerically higher gears lower your dyno #'s? (MyFirstCorvette)
Thanks GUYS! :cheers:
As someone else on the forum said
"It's as clear as mud", for me anyway.
If the car is making more torque because of numerically higher gears, wouldn't that make it easier for it to rev up faster? I know better gearing helps off of the line, but I think it may help when your moving also (perhaps even top speed)
:confused: :confused: :confused: :confused:
Confused, but I'll live! :lol: :lol:
[Modified by MyFirstCorvette, 9:12 AM 8/8/2003]
As someone else on the forum said
"It's as clear as mud", for me anyway.
If the car is making more torque because of numerically higher gears, wouldn't that make it easier for it to rev up faster? I know better gearing helps off of the line, but I think it may help when your moving also (perhaps even top speed)
:confused: :confused: :confused: :confused:
Confused, but I'll live! :lol: :lol:
[Modified by MyFirstCorvette, 9:12 AM 8/8/2003]
Instructor
Joined: Jul 2003
Posts: 194
Likes: 0
From: Torrington CT
Re: Why do numerically higher gears lower your dyno #'s? (MyFirstCorvette)
Let me chime in....
Yes, a lower gear ratio (higher numerical) will produce more torque at the rear wheels than a higher ratio. That is why lower gears are preferred for drag racing, where maximum acceleration is the goal.
However, the lower ratio also has a slightly greater frictional (not centrifugal) loss, hence the horsepower and torque numbers will be slightly lower.
Torque and horsepower are corrected to engine speed, as noted above in another post, so as to make comparisons from car to car valid.
To get maximum readings, the dyno run should be done with the tranmission in the gear whose ratio is closest to 1:1, therefore minimizing friction losses within the tranmission.
Yes, a lower gear ratio (higher numerical) will produce more torque at the rear wheels than a higher ratio. That is why lower gears are preferred for drag racing, where maximum acceleration is the goal.
However, the lower ratio also has a slightly greater frictional (not centrifugal) loss, hence the horsepower and torque numbers will be slightly lower.
Torque and horsepower are corrected to engine speed, as noted above in another post, so as to make comparisons from car to car valid.
To get maximum readings, the dyno run should be done with the tranmission in the gear whose ratio is closest to 1:1, therefore minimizing friction losses within the tranmission.
