transmission losses

[Guest]

some simple differentiation equations

 

There's no such thing! :lol:

[boost monkey 0]

lol, yeah sure there is!

 

try this one:

 

dy

dx x

[jezzaG60 0]

Rolling road results do seem to vary a great deal from one set of rollers to another. The most important thing from a rolling road is consistancy.

If you are looking to see what gains mods have given you, always use the same rolling road.

The losses vary between different types of rolling road as some are single roller, others are twin, i.e your tyre has 2 contact patches. this will clearly effect the rolling losses.

Don't by any means think that "wheel horsepower" figures are the be all and end all. You will see variations in the results by changing your tyre pressures, wheel size, tyre size or even the amount of tread on the tyre.

Some rolling roads perform a purely inertia run where the vehicle accelerates the mass of the rollers and then a simple calculation is performed to calculate the torque. Other rolling roads apply a load to the rollers to slow the rate of acceleration to give a better resolution to the test.

This is where another flaw with a rolling road test can arise. The engine is having to accelerate the flywheel, transmission, driveshafts, wheels and rollers. If you can remove mass from any of these then the acceleration will be faster and hence the result will be higher. I think this is where people can be mislead in to thinking that a lightened flywheel adds power.

 

If you want an exact figure for you engines output, put it on an engine dyno.

If you want to compare your car with your mates, take it to the same rolling road, better still, take it there on the same day.

If you want to keep track of how your mods are effecting your performance, pick a rolling road and stick with it. If your being fussy, keep a note of your tyre pressures. Keep the same size wheels and tyres, same transmission etc.

[boost monkey 0]

Very good points.

 

at the end of the day, the micron thick layer of film on a particularmain bearing would come into play, albeit the differences would be infintesimally small.

 

We're modelling this kind of thing at the moment in Finite Element Analysis.