Edit Tune

[Adam]

I thought it was about 17% for a manual and 20% for an auto.

[CnC]

I thought it was about 17% for a manual and 20% for an auto.

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The loss seen between the flywheel figures and the rear wheel figures seen on chassis dynomometers varies for several reasons between automatic and manual cars of the same type, and even cars of the same type with the same transmission due to the large number of variables that must be controlled to get a consistent run, these include:

- Barometric pressure

- Ambient temperature

- Relative humidity

- Dynomometer ramp rate

- Tyre pressure, temperature, compound, size and wear condition

- Vehicle transmission type, oil temperature and wear condition

- Engine oil temperature and wear condition

- Water temperature

- Vehicle Inlet Air Temperature Sensor Placement Position (very often used to fudge readings..)

- Throttle position

- Other correction & fudge factors controllable by the dyno operator

- Dynomometer brand, model, software and hardware revisions

and more..

As you can see there are quite a large number of variables to control in order to make a run comparable from one car to the next, or even from your same car on different days.

While most dynometer software packages allow the tuner to input most of these variables I suspect that a lot of them wouldnt spend the required amount of time to enter all the required variables that have an impact on the end result.

All that being said you will generally however you will see a higher 'loss' with an automatic transmission than a manual due to the convertor slip and other factors.

Hopefully that's helpfull for a few people.

Kris