Dynamometer Testing and Modern BMW Engine

[Whisky_Tango]

This is a very interesting and knowledgeable 4 pages article!!

I only cut and paste the conclusion here, but every page or paragraph u will learn something about engine performance!!

Happy reading....

http://dinancars.com/whitepapersFile.asp?ID=9
Conclusion
If you decide to test your car on a dyno, whether in stock or modified form, be advised that you will not see the same results as BMW or Dinan. Putting the time consuming and tedious procedures aside, any number of things can cause your measurements to be different from those published. Even in a best case scenario, assuming that there is no need to be concerned about calibrations because the performance software has been supplied, it still takes the better part of three days to go through the proper testing procedure and collect the necessary data.

If the engine is detonating or in the "savior mode" because of excessive temperatures, gains can not be measured. In fact if the car sits and heat soaks or cools for an excessive period of time between runs, enough variance can be created that the performance component enhanced car may show less power than the stock car, or even a very exaggerated gain.

By way of summary, following are some of the more significant factors that you should keep in mind when considering dyno testing in general terms, as well as what to look for in the facility itself.

1) Each dyno will produce different results (even with the same brand of dyno).

2) The octane rating of fuel varies in different parts of the country (you must have a controlled fuel supply).

3) Cold weather increases the gains and hot weather decreases them, even with temperature corrections.

4) Lack of oxygen from exhaust in a dyno room will cause a loss in power.

5) Slipping tires on the rollers will reduce the measured gains.

6) Inertia type dynos have a lighter load than the car will see on the road. This is especially true for cars with heavy drive trains because some of the power will get absorbed spinning the masses faster. The inertia correction programs employed in these types of dyno's are not completely accurate.

7) Fixed load dynos have a higher load than what the car sees on the road. This excessive load will result in a large mixture shift and the detonation sensor will be activated prematurely.

No dyno can accurately simulate wind resistance, the ram air effect into the airbox or cooling of the intake tract under the hood.

9) The size of the fan used during testing will change the power output.

10) Oil temperatures will affect output due to changes in friction.

11) The air intake temperature sensor will trigger adjustments to fuel mixture and ignition timing.

[ryan]

Sticky'd this.

[rodders]

Thanks for sharing dude. Very informative.

[Whisky_Tango]

You are most welcome Rodney...

[Viper Warrior]

Originally Posted by Whisky_Tango

This is a very interesting and knowledgeable 4 pages article!!

I only cut and paste the conclusion here, but every page or paragraph u will learn something about engine performance!!

Happy reading....

DINAN - BMW Specialist Tuner Parts Setup Performance horsepower torque
Conclusion
If you decide to test your car on a dyno, whether in stock or modified form, be advised that you will not see the same results as BMW or Dinan. Putting the time consuming and tedious procedures aside, any number of things can cause your measurements to be different from those published. Even in a best case scenario, assuming that there is no need to be concerned about calibrations because the performance software has been supplied, it still takes the better part of three days to go through the proper testing procedure and collect the necessary data.

If the engine is detonating or in the "savior mode" because of excessive temperatures, gains can not be measured. In fact if the car sits and heat soaks or cools for an excessive period of time between runs, enough variance can be created that the performance component enhanced car may show less power than the stock car, or even a very exaggerated gain.

By way of summary, following are some of the more significant factors that you should keep in mind when considering dyno testing in general terms, as well as what to look for in the facility itself.

1) Each dyno will produce different results (even with the same brand of dyno).

2) The octane rating of fuel varies in different parts of the country (you must have a controlled fuel supply).

3) Cold weather increases the gains and hot weather decreases them, even with temperature corrections.

4) Lack of oxygen from exhaust in a dyno room will cause a loss in power.

5) Slipping tires on the rollers will reduce the measured gains.

6) Inertia type dynos have a lighter load than the car will see on the road. This is especially true for cars with heavy drive trains because some of the power will get absorbed spinning the masses faster. The inertia correction programs employed in these types of dyno's are not completely accurate.

7) Fixed load dynos have a higher load than what the car sees on the road. This excessive load will result in a large mixture shift and the detonation sensor will be activated prematurely.

No dyno can accurately simulate wind resistance, the ram air effect into the airbox or cooling of the intake tract under the hood.

9) The size of the fan used during testing will change the power output.

10) Oil temperatures will affect output due to changes in friction.

11) The air intake temperature sensor will trigger adjustments to fuel mixture and ignition timing.

Wow, by just reading the conclusion, I feel that doing the Dyno is like a waste of time as each dyno always produce a different results ...... Sorry, I'm no expert on this, just my personal view

[TheNew7]

Well, the thing is, if you do your dyno twice, for example once before and another after you have done some modifications, then I guess if the environment is similar, then the results should be quite accurate, measuring the gains. However, if you expect your car to show catalogue figures, that might be a little more difficult.

just my 2 cents....