22 March 2006
Regularly I get people coming in with the question of “Nick what do you charge for a Dyno run”. Further probing results in a desire to see how many horsepower their vehicle actually makes, but what they want to do with those figures is beyond me.
Firstly every car is different. Jake Venter published a long article about this in CAR magazine. So your vehicle might even exceed the published figures.
Secondly there are different ways of measuring power and norms. There is British and American BHP, SAE HP German Din etc. Some manufacturers also use their own norm.
Thirdly how accurate is the Dyno and when was it last calibrated and certified ?
The most important fact is, that you need consistency. So use the same Dyno without leaving too much time difference in-between runs. There is wear and tear too.
I can measure in corrected (for Temperature and Barometric efficiency) DIN KW and SAE HP as well as a few others. Furthermore I can run your Car against a constant load (acceleration measurement) or hold it at specific RPM points for a specific time.
I use the latter for development, as I can check the differences in power, exhaust temperature, pressures and vacuum at different throttle openings and make that work for me.
Have you not heard “Your car made 100 kw on our Dyno and afterward 125”. Car magazine might even list it at 90 Din Kw standard. So it is all relative, isn’t it ?
Furthermore unscrupulous Dyno operators can skew their figures in their favour. I.e. before run at 90 % throttle, after at full throttle in a cooler environment.
Remember a Dynamometer is a precision instrument like a Micrometer. The results only mean something to the person using that tool. They should be used for their scientific purpose and not for Advertising !
Since your vehicle gets tested under the most strenuous conditions, if something can go wrong it will. So make sure your Baby is pampered beforehand and the Dyno operator is informed !
You use an Engine Dyno for research purposes while a rolling road (such as I have) is more useful for mapping, tuning and general faultfinding.
There is plenty more to be said but I’ll leave that for an in-depth Article at a later stage.
Points to remember about rolling road testing: -
Please ensure your vehicle is in good mechanical condition. If you are unsure we can service/check your vehicle prior to testing.
"Whoever admits that he is too busy to improve his methods, has acknowledged himself to be at the end of his rope. And that is always the saddest predicament which anyone can get into." J. Ogden Armour