I was wondering if lighter wheels would give you better dyno numbers because of the decreased resistance. It seems to me that it would. Anybody know?

Ivory Coupe 5AT
Z tube, K&N drop in.
Fujitsubo Catback

 

Yes it will. Smaller diameter, lighter and lower inertia rims/wheels will make a big difference. Also, the more sticky a wheel is, the less slipping on the dyno drum, hence a better reading.

<font color=blue>The above statements are only my take on the issue. If you disagree with anything I typed then you are 100% right!</font color=blue>

 

Wow i was actually thinking about this but i never thought it would be true, dam im going to go back to the dyno with my stock wheels!


Martin
2003.5 BS G35
Nismo Aero/Sport Package
0-60 5.4 - 1/4 Mile 14.16 *GTech* and on 19's!!

 

I asked my dyno operator the same ? .25 to 30 years of dynoing and tuning race cars . He's answer.....No....could tell if it would be wheels or just the 1 to 4whp in different dyno runs

Couldnt afford it when young...gonna play when Im old

 

Wrong. The weight of the wheel does change the way the Dyno shows your readings. I have been doing dynos since 1996. And have seen people actually swap out 18inch wheels with 15" wheels just for the dyno, and the hp difference can be as high as 10 hp.

Your buddy doesn't know what he is talking about. Just like how a ASE mechanic says that dino oil is the best to use in a engine and not synthetic.

2004 Infiniti G35S, 6MT, Premium, Sport, DP
Mods: JDM Clears, 20% tint, Z-tube, Stilen CAI
Track: 14.32 at 98.79 mph 2.2032 60ft
Dyno 07-07-04 - 234.2 hp & 233.8 tq
http://www.g35world.com

 

Also, brake rotor diam. affects HP readings on the dyno. Larger brakes, lower HP.

-------------------------------------------
2004 6MT DG/G Coupe | Premium | Aero Kit | ClearBra | See profile for pix

 

Dynos work by measuring the acceleration of the drum. Gear ratios have to be programed in but anything else that lets the wheels spin up faster will show as increased horsepower. Smaller diameter tires will in effect change the final gear ratio and should be accounted for in the set up. But lighter wheels, tires and rotors will accelerate quicker without effecting the gear ratio and will show as higher HP numbers.

Mark

2003 Sedan AT. Ivory Pearl/ Willow
20% tint. Z-tube. Clear Corners w/ PIAA.
Aluminum Pedals

 

Unfortunately Dynojets don't reflect the real world acceleration because the drum weights less than the vehicle and the lack of wind resistance which slows the engine acceleration significantly...........the two things plus the higher friction from tire being deformed on the smaller diameter drum makes for some crazy error prone numbers.

Vehicle weight on each rear tire has lots to do with tire friction against roller.............you can add trunk weight and many times get a HP increase or change rear tire inflation pressures. To get a faked up graph to display to your friends.

 

On a mustang dyno you will see a bigger wheel hp loss factor than you would on a dynojet since the mustang is weighted to your car. My tuner said my 19's are costing me about 20hp or roughly 5%.

 

Actually the 19s aren't costing you horsepower. the motor is still making the same horsepower with 19" wheels and tires as you are with the stock 17s. The unsprung rolling mass is greater causing slower acceleration. Not an actual loss of power.

Mark

2003 Sedan AT. Ivory Pearl/ Willow
20% tint. Z-tube. Clear Corners w/ PIAA.
Aluminum Pedals

 

Mark,

I believe what you are saying is contradicting, sure crank hp is the same, but you car doesn't accelerate on the crank. Rear wheel hp is what's going to move your car.

 

Having more inertia on the wheels only affects the rate of change of RPM. Changing wheel inertia can affect 0-60 times and 1/4 miles times less so, but steady state HP and terminal velocity will be unaffected.

HP is the ability to do work. You can give the engine more work to do by increasing momentum and/or inertia but the engines ability to do work is unchanged. You can put three passengers in your car to decrease the acceleration rate, but carrying three passengers in the car won't change the wheel HP.


In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust

 

"but carrying three passengers in the car won't change the wheel HP. " ? other than changing the [tire to road] friction coefficient by increasing the load on the rear wheels/tires......the rear wheel power won't change but the measurement will. So will the acceleration be decrease by some factors for each 100 pounds [~~0.1 second in quarter mile time].

 

"the rear wheel power won't change but the measurement will. So will the acceleration be decrease by some factors for each 100 pounds [~~0.1 second in quarter mile time].
"
Correct! ;-)

In Theory, practice and theory are the same.
In Practice, practice and theory are not the same.

2004 G35 6MT Blk/Blk Sedan Stillen Air, Stillen Exhaust