Dyno vs. Overall GEAR?
Thread Starter
Melting Slicks
Joined: Dec 1999
Posts: 2,049
Likes: 701
From: Tulsa, Ok
Dyno vs. Overall GEAR?
I assume the dyno has algorithms to compensate for the overall gear differences. If not, then how do we get a true reading using the wide range of gearing? For example, ANY manual has a huge gear advantage over the A8 (3.42 vs 2.41). Even if you ran the base A8 in 5th gear, the Manual has a big advantage to spin the dyno up quicker.
If my assumption is correct, then should we dyno base cars in 5th?
If my assumption is correct, then should we dyno base cars in 5th?
Thread Starter
Melting Slicks
Joined: Dec 1999
Posts: 2,049
Likes: 701
From: Tulsa, Ok
Yet more confusion comes cuz the 4.10 will run out of rpm around 100mph. Anyone own or set up various dynos know the real scoop on how it knows the difference?
Intermediate
Joined: Nov 2013
Posts: 32
Likes: 1
Inertia dynos read rate of change in roller speed over time.
They use the rotational mass of the roller to calculate horsepower. Then it back calculates torque using the RPM signal it receives.
So by adding a gear, you spin the rollers with greater acceleration over a shorter time, but with less roller speed.
I believe some dynos read actual torque to the tire, and back calculate horsepower and use that info with RPM and gear ratios.
Most dynos read via inertia.
They use the rotational mass of the roller to calculate horsepower. Then it back calculates torque using the RPM signal it receives.
So by adding a gear, you spin the rollers with greater acceleration over a shorter time, but with less roller speed.
I believe some dynos read actual torque to the tire, and back calculate horsepower and use that info with RPM and gear ratios.
Most dynos read via inertia.
Thread Starter
Melting Slicks
Joined: Dec 1999
Posts: 2,049
Likes: 701
From: Tulsa, Ok
Thanks Proxses! I understand now... Duration of the pull is only a factor in comparing amount of work done. Engine RPM to duration over drum accumulative revolutions start to end.
That makes me want to experiment with different mid-range gears to see the net effects on various cars. Something I'm sure every dyno owner has played with.
That makes me want to experiment with different mid-range gears to see the net effects on various cars. Something I'm sure every dyno owner has played with.
Inertia dynos read rate of change in roller speed over time.
They use the rotational mass of the roller to calculate horsepower. Then it back calculates torque using the RPM signal it receives.
So by adding a gear, you spin the rollers with greater acceleration over a shorter time, but with less roller speed.
I believe some dynos read actual torque to the tire, and back calculate horsepower and use that info with RPM and gear ratios.
Most dynos read via inertia.
They use the rotational mass of the roller to calculate horsepower. Then it back calculates torque using the RPM signal it receives.
So by adding a gear, you spin the rollers with greater acceleration over a shorter time, but with less roller speed.
I believe some dynos read actual torque to the tire, and back calculate horsepower and use that info with RPM and gear ratios.
Most dynos read via inertia.
Le Mans Master
Joined: Nov 2005
Posts: 7,059
Likes: 366
From: Kendall Park NJ
We observed approximately 4% lower HP reading on Tune Time's Mustang Dyno when using 4.10s vs. 3.42s.
As for 4.10s running out of RPM, a manual C7 could pull up to 130 mph @ 6600 rpm on OEM tires in 4th gear.
As for 4.10s running out of RPM, a manual C7 could pull up to 130 mph @ 6600 rpm on OEM tires in 4th gear.
Safety Car
Joined: May 2000
Posts: 4,827
Likes: 351
From: Albuquerque NM
We changed from 3.42's to 3.73's on a C5, saw a few percent loss on a Dynojet.
Changed from 3.73's on a Ford Lightning truck to 4.11's, again saw a small loss.
This is even though both were quicker accelerating after the change, the dyno because of how it calculates hp/tq, saw a loss.
Racer
Joined: Aug 2014
Posts: 250
Likes: 57
Now all we need is a company to develop those shorter rear gears for the C7!
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Dig
Joined: Jan 2006
Posts: 5,475
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From: Port Saint Lucie FLORIDA & HONDURAS
Dyno vs ET...
Then slip in a converter and should be quicker. Maybe not on these C7's. Or maybe ?!? Look at the 60' on stock C7's on stock tires on a prepped track. Pretty awesome !!
I started a thread here a while ago asking or wondering about a stall on a C7. Between the post and PM's... Why go aftermarket..
Then slip in a converter and should be quicker. Maybe not on these C7's. Or maybe ?!? Look at the 60' on stock C7's on stock tires on a prepped track. Pretty awesome !!
I started a thread here a while ago asking or wondering about a stall on a C7. Between the post and PM's... Why go aftermarket..
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
If you are trying to win a dyno war with a C7 --you bought the wrong car-----It is a sports car---Yes similar Ford and Dodge's brag about dyno HP but on the 1/4 mile and on the track--they are slower--You have to take the complete package into account-----The dyno does not measure the weight of the car--or the response thru the gears--
To make it even more confusing---The 2014 A6 both Z51 and Base models have no trans gear ratio of 1:1 !!!! In 4th gear they are both 1.15 :1----Both under driven--
As a Corvette owner since 1975 I never worried about dyno numbers---Pretty for some---but not the true measure of how quick or fast a car can be-------JMHO-----
To make it even more confusing---The 2014 A6 both Z51 and Base models have no trans gear ratio of 1:1 !!!! In 4th gear they are both 1.15 :1----Both under driven--
As a Corvette owner since 1975 I never worried about dyno numbers---Pretty for some---but not the true measure of how quick or fast a car can be-------JMHO-----
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From: Providing the most proven supercharger kits for your C5/6/7 609-752-0321
Just one of the reasons why we spent the extra money for a Dyno Pack dyno, it reads correctly regardless of gear ratio. Assuming you tell it the correct ratio of course.