Dyno Testing ??

[RI-Matt]

I know a lot of guys have run their cars on the chassis dynos with varied results, but I'm curious if anyone has used one of the dynos that attaches right to the axles ( wheels are removed ) How accurate are they in comparison to a roller dyno?

The reason I ask is a buddy of mine just ran his supercharged 350Z on one and made some decent HP numbers (still low TQ though)

Any comments would be appreciated.

TIA

Matt

 

[2QUIK6]

A friend of mine had been trying to purchase that type of Dyno for his shop because they are more accurate especially for the manual shift cars. When you slam thru the gears it is possible to have the tires break loose from the drum on the roller dyno's and thus alter the readings. Also, you don't have the rolling weight of the wheels to lower the numbers slightly, as well as varying tire height which would effect the overall gear ratio.
He could never get any of the manufactures to respond to him, so he has ended up purchasing a roller dyno afterall.
Also, its not uncommon to get slightly varying results from dyno to dyno due to calibration differences and air conditions.

 

[RI-Matt]

Rob, thanks for the reply. I was thinking the same thing about the rolling weight of the wheels but my buddy was told if he took his car to a roller dyno it would show higher numbers.

Matt

 

[2QUIK6]

Could be true, the changed overall ratio may work in his favor. Again, the numbers will be different from dyno to dyno because of calibration and the different ways the machine measures hp and torque. To truely tell if you are producing more hp after certain mods, you should use the same dyno each time for measurements...at least according to the guy I know that's just purchased one, and he has over 24 years experience tuning cars.