drivetrain losses?
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drivetrain losses?
posted from "tib in cb"
::edit::
ok, i think i have this figured out.
if
QUOTE
Shadohh, turbulence and Agarwal, I would love to continue the driveline loss in another forum as this is not the place for it.
posted by me smile.gif QUOTE
for those of you that are having a hard time understanding the drivetrain losses, think of it this way: the mass of the parts in the drivetrain that need to be turned (gears, driveshafts, etc...) is fixed. for the sake of arguement, let's assume that there are 4 kilograms of mass to turn in the drivetrain, whether you're making 140 or 300 hp at the crank, the same amount of energy is needed to turn the 4 kg. i'll look through my phisics notes later today and post the heat difference between the tranny eating 20hp and 40hp...we just went over energy and heat.
as i said, a fixed amount of mass, under the same conditions, will require a fixed amount of force to move it.::edit::
ok, i think i have this figured out.
if
- [*]energy = work (hp OR kw) = heat, then...[*]suppose:[*]we have 10kg of drivetrain mass...[*]that takes 14% of our stock 140hp to move[*]now i have a turbo, and have 300 crank hp[*]i'm applying 300 hp to the 10kg, rather than 140hp[*]therefore, the net force is greater, causing a greater acceleration (acceleration also means a direction change, not just a change in velocity)[*]but some of the excess work is lost as heat, but not necessarily from friction, but just because it's work[/list]
i guess to really measure this (if it's true), one would need a calorimeter or some heat measuring device. hmm...stick a thermometer in your tranny and run your car on a dyno
tongue.gif i'm gonna run this by my physics professor. i'll keep you all posted.
[ March 01, 2003, 05:52 PM: Message edited by: turbulence ]
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To a very limited extent, drivetrain losses do increase as force increase, but not in a linear fashion. A tranny that "absorbs" 30% of force at say 200 HP would not "absorb" the same 30% at 1000 HP. It would be down to about 10-15%, (assuming the transmission lived through the test). The actual "force" absorbed by the tranny would be 60 HP at 200 ENGINE(30%), but only 100 or 150 HP at 1000 HP(10-15%).
Trying to calculate the lost "force" by tempature increase would be very, very, very, very, very intensive. Just the vast number of things you would have to measure/quantify.
You would have to measure the tempature of each individual gear, it's mass, and it's thermal absorption properties, same for the fluid, and also somehow measure any lost mass (gear shavings, if any). Calculate the temp increase at the bearings, and their mass/thermal absorption properties...etc..etc..etc..
It would be much easier to just hook the engine up to an engine dyno, obtain readings, then dyno the engine/transmission on a chassis dyno.
Trying to calculate the lost "force" by tempature increase would be very, very, very, very, very intensive. Just the vast number of things you would have to measure/quantify.
You would have to measure the tempature of each individual gear, it's mass, and it's thermal absorption properties, same for the fluid, and also somehow measure any lost mass (gear shavings, if any). Calculate the temp increase at the bearings, and their mass/thermal absorption properties...etc..etc..etc..
It would be much easier to just hook the engine up to an engine dyno, obtain readings, then dyno the engine/transmission on a chassis dyno.
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yes, but random, i'm like you...or at least i am (unless i'm misinterpreting your sig), in that i needlessly complicate things. come on, it's much more fun to think of how to measure drivetrain losses through heat than the cut-and-dry engine vs. chassis dyno tongue.gif however, random, can you explain the increase in drivetrain loss from the hypthetical 200 vs. 1000hp engines? i mean, if the drivetrain has the same mass, then what's the explanation for the increase? i'm just missing the part about how it "absorbs" more power.
::edit::
yeah, my 600th post! i'm hoping it's another one like my torque vs. hp post wink
[ March 03, 2003, 08:35 AM: Message edited by: turbulence ]
::edit::
yeah, my 600th post! i'm hoping it's another one like my torque vs. hp post wink
[ March 03, 2003, 08:35 AM: Message edited by: turbulence ]
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More force = more friction. The forces applied (load) to gear mating surfaces, bearings, thrust washers..etc..etc..etc... all goes up when force increases. Thus friction increases.
If you take 2 surfaces, and apply 200 FT LBs of force to them, measure the heat generated, then apply 1000 ft lbs of force, you'll see an increase in friction (via increased heat).
Bearings that only show marginal heat increases at 200 FT lbs, may show unbeliveable heat increases with the force factor increased by 5 (1000 Ft lbs).
Again, it WOULD be possible to quantify the losses via temp increase, but it would be ungodly hard.
If you take 2 surfaces, and apply 200 FT LBs of force to them, measure the heat generated, then apply 1000 ft lbs of force, you'll see an increase in friction (via increased heat).
Bearings that only show marginal heat increases at 200 FT lbs, may show unbeliveable heat increases with the force factor increased by 5 (1000 Ft lbs).
Again, it WOULD be possible to quantify the losses via temp increase, but it would be ungodly hard.
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Random, I think that you are trying to express that if you do the same amount of work (moving the internals to a certain RPM) over a shorter amount of time (greater amount of HP), the losses will increase. If you input more energy to do the same amount of work, more energy will be wasted (heat). That is where the inertial losses due to the transmission increase.