Drivetrain Dyno Question
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Coordinator :: Dynamic MiNi Collective
Joined: Jul 2002
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From: Chandler, AZ
Dyno Question
I will be getting my Mini S dynoed in a few weeks.
Will it make any difference if I use my stock 17" S Lites (heavy) with 205/45 "24.2 diam." or my Kosei K1's (light) "with shorter 23.5" 215/45-16's?
I know my smaller tires help my acceleration, but will they affect horsepower readings on the Dyno?
Will it make any difference if I use my stock 17" S Lites (heavy) with 205/45 "24.2 diam." or my Kosei K1's (light) "with shorter 23.5" 215/45-16's?
I know my smaller tires help my acceleration, but will they affect horsepower readings on the Dyno?
The dyno should be calibrated to wheel diameter and vehicle weight....but they're usually not. Whatever you do - keep the same tires for all your dyno runs to maintain consistency.
5th Gear
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From: Back IN Chicopee
Heavier should be a drain on HP. They did a dyno on a show, they did it at baseline line and after different additions. After a brake upgrade they lost hp to increased rotational mass of the bigger rotors.
Paul
Paul
4th Gear
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From: McHenry County, Northern Illinois
rotating Mass
Last year I won some dyno time and took my MCS in. The tech told me that he had seen one car show 18 hp difference on the dyno by changing to Lighter wheels.
I have no Idea if the before and after runs were done the same day, or corrected for conditions each run.
JD
I have no Idea if the before and after runs were done the same day, or corrected for conditions each run.
JD
Turbius Maximus
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From: Infinity and beyond
Hey buddy, Logically it will free up power relative to your stock wheels due to changing the dyamater....like changing the gears in your trans...
unsprung weight is not a big a deal on a dyno...cause you are strped down.... curious to find out now...GOOD QUESTION!!!
unsprung weight is not a big a deal on a dyno...cause you are strped down.... curious to find out now...GOOD QUESTION!!!
5th Gear
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From: Back IN Chicopee
Do a google search and use these words: rotational mass horsepower.
You will get a brain cramp. You will also see that it was a show on Speed channel that did the dyno and loss 12hp with the increased rotational mass of bigger rotors.
I donot see how make the additional mass wheel and tire would alter the resulting loss of HP.
Paul
You will get a brain cramp. You will also see that it was a show on Speed channel that did the dyno and loss 12hp with the increased rotational mass of bigger rotors.
I donot see how make the additional mass wheel and tire would alter the resulting loss of HP.
Paul
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3rd Gear
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"I just called him and he said only diameter will change it..."
That might be true. However I saw the TV show mentioned above. They explained that even though they maintaned or reduced the overall weight and outside diameter of their wheel and brake package, that by moving the weight farther away from the center of the hub, (bigger although lighter brakes and larger lighter wheels with lower profile tires) they measured about a 8 hp loss on a Acura TSX.
As stated above though, just make sure all your pulls use the same wheels. That way any mods you do in the future will be measurable.
On the TV show, they did a base pull. Then changed wheels, brakes and exhaust. Did another pull, came up short, blamed the exhaust, removed the exhaust, came up shorter, made some phone calls, put the exhaust back on .... The joys of spending other peoples money !!
That might be true. However I saw the TV show mentioned above. They explained that even though they maintaned or reduced the overall weight and outside diameter of their wheel and brake package, that by moving the weight farther away from the center of the hub, (bigger although lighter brakes and larger lighter wheels with lower profile tires) they measured about a 8 hp loss on a Acura TSX.
As stated above though, just make sure all your pulls use the same wheels. That way any mods you do in the future will be measurable.
On the TV show, they did a base pull. Then changed wheels, brakes and exhaust. Did another pull, came up short, blamed the exhaust, removed the exhaust, came up shorter, made some phone calls, put the exhaust back on .... The joys of spending other peoples money !!
Turbius Maximus
Joined: Mar 2004
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From: Infinity and beyond
They are most likely calculating for the street difference though...as in the over all #s would not change but how it effects "REAL WORLD" performance is different...
and changing wheels will show a diffence...due to diameter
and changing wheels will show a diffence...due to diameter
Originally Posted by gmack
"I just called him and he said only diameter will change it..."
That might be true. However I saw the TV show mentioned above. They explained that even though they maintaned or reduced the overall weight and outside diameter of their wheel and brake package, that by moving the weight farther away from the center of the hub, (bigger although lighter brakes and larger lighter wheels with lower profile tires) they measured about a 8 hp loss on a Acura TSX.
As stated above though, just make sure all your pulls use the same wheels. That way any mods you do in the future will be measurable.
On the TV show, they did a base pull. Then changed wheels, brakes and exhaust. Did another pull, came up short, blamed the exhaust, removed the exhaust, came up shorter, made some phone calls, put the exhaust back on .... The joys of spending other peoples money !!
That might be true. However I saw the TV show mentioned above. They explained that even though they maintaned or reduced the overall weight and outside diameter of their wheel and brake package, that by moving the weight farther away from the center of the hub, (bigger although lighter brakes and larger lighter wheels with lower profile tires) they measured about a 8 hp loss on a Acura TSX.
As stated above though, just make sure all your pulls use the same wheels. That way any mods you do in the future will be measurable.
On the TV show, they did a base pull. Then changed wheels, brakes and exhaust. Did another pull, came up short, blamed the exhaust, removed the exhaust, came up shorter, made some phone calls, put the exhaust back on .... The joys of spending other peoples money !!
6th Gear
Joined: Oct 2002
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From: Lansdale, PA
http://www.nissanperformancemag.com/may01/dyno.shtml
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
Turbius Maximus
Joined: Mar 2004
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From: Infinity and beyond
Originally Posted by andy@ross-tech.com
http://www.nissanperformancemag.com/may01/dyno.shtml
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
5th Gear
Joined: Jan 2004
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From: Back IN Chicopee
Originally Posted by andy@ross-tech.com
http://www.nissanperformancemag.com/may01/dyno.shtml
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
Less than 1 hp difference between the very light and fairly heavy wheels at most rpm:
I wonder how they got more of diff with the new rotors on the show?
Paul
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From: Back IN Chicopee
5th Gear
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From: Indianapolis
Some chassis dynos, Dynajet being a prime example and very common, measure whp by seeing how quickly a car can accelerate a heavy roller of known mass. F=MA Thus the results are subject to the same influence of rotational mass that the car is on the street since the tire/wheel/brake mass must be accelerated along with the roller.
Other dynos use various methods of providing known resistance to the engine and measuring horsepower that way. Load style dynos will allow you to maintain a constant rpm and load, and are both more sophisticated in their capabilities and expensive. Since you can maintain a constant rpm against a known resistance on these dynos the rotational mass of the wheels and tires isn't a factor as they are not being accelerated.
We use various models of eddycurrent dynos at work (test cells are engine dynos, not chassis) and can basically duplicate any speed, load and temperature conditions I want. Ideal for testing and tuning, but unfortunately I can't put the MINI engine on one. Of course the 15L engines my group tests every day weigh more than the MINI (the whole car) and make REAL torque.
Scott
90STX/SM
Other dynos use various methods of providing known resistance to the engine and measuring horsepower that way. Load style dynos will allow you to maintain a constant rpm and load, and are both more sophisticated in their capabilities and expensive. Since you can maintain a constant rpm against a known resistance on these dynos the rotational mass of the wheels and tires isn't a factor as they are not being accelerated.
We use various models of eddycurrent dynos at work (test cells are engine dynos, not chassis) and can basically duplicate any speed, load and temperature conditions I want. Ideal for testing and tuning, but unfortunately I can't put the MINI engine on one. Of course the 15L engines my group tests every day weigh more than the MINI (the whole car) and make REAL torque.
Scott
90STX/SM
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