G
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·One for Droid and others. How do we calculate power loss from flywheel to the driven wheels? This must be difficult to work out on an EVO. Here are the things I believe affect it, but not sure if it makes them better or worse.
1) Flywheel - it has mass, so takes energy to move it. Lighter flywheel, less loss?
2) Clutch - this must create a loss which must depend on how well it engages (slipping clutch|EQU|power loss). What about multi-plate clutches? Better or worse?
3) Gearbox - helical gears feature drag, so losses here. Does a dog box (which has less drag) mean less power loss?
4) Front diff - if you have one, like I do, would that mean more loss from an LSD? Do open diffs (standard) mean less loss?
5) Centre diff /transfer unit - proportions power front/rear, but probably loses some of the power in doing so. The ACD in the 7 is a multiplate clutch, so that must feature slightly bigger losses.
6) Rear diff - as front diff. AYC presumably would have a higher loss than a mechanical diff in the RS/RSX?
7) Driveshafts.
8) Wheel and tyre weight - These have mass and are rotated, so are a load - cause of aloss?
9) Tyre friction - power has to overcome tyre friction, so that must have an effect on loss.
Idea behind this thread is to understand the science of drivetrain power loss, why 4WD is higher than 2WD and what effect drivetrain changes have on power losses.
As a side issue, although RR measurements can only be taken seriously by looking at the power-at-the-wheels figure, it can be very difficult to get accurate power-at-the-wheels figures as it:-
1) Depends on grip and how well cut the rollers are. Cars with big power can slip, hence why they are strapped and have bodies inside them often. My car on it's last RR session had 3 people in it and 6 straps tieing it down and it was still slipping!
2) Ambient temperature and lack of real airflow will stifle power outputs, and give lower readings. It will affect highly tuned engines more than standard ones, as induction kits, cooling kits etc. only really work properly on the move.
3) Gearing - depending on what gear it is done in, need to be close to 1.0 - or recalculate according to the gear ratio
Anything I missed?
1) Flywheel - it has mass, so takes energy to move it. Lighter flywheel, less loss?
2) Clutch - this must create a loss which must depend on how well it engages (slipping clutch|EQU|power loss). What about multi-plate clutches? Better or worse?
3) Gearbox - helical gears feature drag, so losses here. Does a dog box (which has less drag) mean less power loss?
4) Front diff - if you have one, like I do, would that mean more loss from an LSD? Do open diffs (standard) mean less loss?
5) Centre diff /transfer unit - proportions power front/rear, but probably loses some of the power in doing so. The ACD in the 7 is a multiplate clutch, so that must feature slightly bigger losses.
6) Rear diff - as front diff. AYC presumably would have a higher loss than a mechanical diff in the RS/RSX?
7) Driveshafts.
8) Wheel and tyre weight - These have mass and are rotated, so are a load - cause of aloss?
9) Tyre friction - power has to overcome tyre friction, so that must have an effect on loss.
Idea behind this thread is to understand the science of drivetrain power loss, why 4WD is higher than 2WD and what effect drivetrain changes have on power losses.
As a side issue, although RR measurements can only be taken seriously by looking at the power-at-the-wheels figure, it can be very difficult to get accurate power-at-the-wheels figures as it:-
1) Depends on grip and how well cut the rollers are. Cars with big power can slip, hence why they are strapped and have bodies inside them often. My car on it's last RR session had 3 people in it and 6 straps tieing it down and it was still slipping!
2) Ambient temperature and lack of real airflow will stifle power outputs, and give lower readings. It will affect highly tuned engines more than standard ones, as induction kits, cooling kits etc. only really work properly on the move.
3) Gearing - depending on what gear it is done in, need to be close to 1.0 - or recalculate according to the gear ratio
Anything I missed?