most mechanical loses?
philleh_83
03-21-2005, 03:56 PM
where do most mechanical loses occure between the transmission and the wheels? Why?
curtis73
03-21-2005, 04:25 PM
I would say the ring gear on a RWD car. Why? using gears to change directions. I'm sure a notable amount is lost in the U-joints overcoming the inertia of the rotating caps as well as friction.
On a FWD car, definitely the CV joints. Large amount of friction there especially since they move with the steering AND articulation.
On a FWD car, definitely the CV joints. Large amount of friction there especially since they move with the steering AND articulation.
MagicRat
03-21-2005, 09:12 PM
Power losses create heat. By far the biggest loss is in a torque converter (auto trans only), hence the need for a transmission cooler in all auto trans cars. This loss is greatly reduced at highway speed when the converter locks up.
Auto trans also have another power loss in the oil pump. This pump is driven off the crankshaft and generaltes pressure to keep the various clutch packs and actuators engaged. The sucks a fair amount of power from the engine.
Manual transmissions and rear ends consume a fair amount of power in sloshing lubricating fluid around and in spinning bearings.
Also tires consume power as they flex when rolling. This is why your tires get hot, especially if inflation is low.
Auto trans also have another power loss in the oil pump. This pump is driven off the crankshaft and generaltes pressure to keep the various clutch packs and actuators engaged. The sucks a fair amount of power from the engine.
Manual transmissions and rear ends consume a fair amount of power in sloshing lubricating fluid around and in spinning bearings.
Also tires consume power as they flex when rolling. This is why your tires get hot, especially if inflation is low.
curtis73
03-21-2005, 10:59 PM
I thought he meant after the trans... easily taken both ways. Philleh.. care to clear that up?
SaabJohan
03-24-2005, 10:56 AM
The main losses in a transmission is caused by the torque going from one cogwheel to another. In most cars these are usually of helical type for soft and quiet operation, that type of wheel robs more power than straight cut found on for example racing cars.
In a typical transmission we have perhaps 4 torque transfers, each being say 97-98% efficient results in a total efficiency of 88 to 92 percent. The rest of the losses is mainly bearing drag and oil splash losses.
These torque transfers can be within the gearbox, but with a RWD, front mounted engine one is typically placed after the gearbox (the differetial).
So if the question is what does take most power after the gearbox but before the wheels it's the diff. But the differential is a part of the transmission, infact all parts before the wheels can be considered to be a part of the tranmission.
As for CV joints they can become hot on a powerful car, but that's probably more due to the lack of cooling than the power they rob.
In a typical transmission we have perhaps 4 torque transfers, each being say 97-98% efficient results in a total efficiency of 88 to 92 percent. The rest of the losses is mainly bearing drag and oil splash losses.
These torque transfers can be within the gearbox, but with a RWD, front mounted engine one is typically placed after the gearbox (the differetial).
So if the question is what does take most power after the gearbox but before the wheels it's the diff. But the differential is a part of the transmission, infact all parts before the wheels can be considered to be a part of the tranmission.
As for CV joints they can become hot on a powerful car, but that's probably more due to the lack of cooling than the power they rob.
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