Drivetrain loss...
Thread Starter
Teching In
Joined: Jul 2002
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From: Southwick,MA
Drivetrain loss... I tried searching but no luck... but anyways my question is this. Is the drivetrain loss (in a stock tranny/rearend situation, I don't want to complicate this with ford 9inch vs. 12 bolt vs. stock scenarious) indeed a percentage or a fixed value. I know the old rule of thumb 15% for manuals and 20% for autos. But it seems to me that why would the transmission and rearend take more power at higher power levels?
For example say you had 350 at the crank and put down 300 to the wheels with a six speed. There is your 15% loss which is 50HP.
Now say you were making 600 at the crank. Is your rearwheel gonna be 510HP and lose 90HP? or is it gonna be a fixed value and lose that same 50hp?
<small>[ February 28, 2003, 02:11 PM: Message edited by: BlakCamZ28 ]</small>
For example say you had 350 at the crank and put down 300 to the wheels with a six speed. There is your 15% loss which is 50HP.
Now say you were making 600 at the crank. Is your rearwheel gonna be 510HP and lose 90HP? or is it gonna be a fixed value and lose that same 50hp?
<small>[ February 28, 2003, 02:11 PM: Message edited by: BlakCamZ28 ]</small>
Thread Starter
Teching In
Joined: Jul 2002
Posts: 45
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From: Southwick,MA
Re: Drivetrain loss... Basically I was looking for the physics type reason why it's a percentage and someone recently sent this to me, which makes sense.
http://www.superstang.com/horsepower.htm
http://www.superstang.com/horsepower.htm
TECH Senior Member
Joined: Nov 2001
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From: Chi-Town, IL
Re: Drivetrain loss... The more power you make, the more thats going to get sucked up by the drivetrain...
Especially with my TH400... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Especially with my TH400... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Re: Drivetrain loss... I don't agree with a lot of what's said here.
Pump / housekeeping losses: pump work is
pressure * flow, flow ~ RPM. Pressure is
fixed by blowoff regulator, point in RPM
band where this becomes fixed value is
unknown. Not power output dependent, RPM
dependent.
Gearing Losses: I believe these are also
mostly viscous / frictional losses. Some
RPM dependent (viscous drag), some speed
independent (plain friction). Again I say
this is more like speed proportional, not
power proportional. How much does torque
affect gearbox friction? Should be no torque
dependence of viscous losses?
Torque Converter: Now here, slip is dependent
on torque, as well as speed, this loss will
go up with power.
Some trans mods made for purposes of handling
more input torque (like raising line pressure)
will produce higher parasitic losses (power =
flow * pressure)
Pump / housekeeping losses: pump work is
pressure * flow, flow ~ RPM. Pressure is
fixed by blowoff regulator, point in RPM
band where this becomes fixed value is
unknown. Not power output dependent, RPM
dependent.
Gearing Losses: I believe these are also
mostly viscous / frictional losses. Some
RPM dependent (viscous drag), some speed
independent (plain friction). Again I say
this is more like speed proportional, not
power proportional. How much does torque
affect gearbox friction? Should be no torque
dependence of viscous losses?
Torque Converter: Now here, slip is dependent
on torque, as well as speed, this loss will
go up with power.
Some trans mods made for purposes of handling
more input torque (like raising line pressure)
will produce higher parasitic losses (power =
flow * pressure)
Re: Drivetrain loss... i really dont beleive a th400 takes more(if any)power than a 4l60e,ill agree on a th350,but not the o/d unit.the o/d has more internal parts to turn.i made 335rwhp with m6,with a few bolt-ons.i changed to a th400 with a loose 4000 converter(only change).i lost exactley 30rwhp(on same dyno).ive seen 4l60es loose 25-30hp just by adding a converter.id love to see some dyno post of these swaps,id be very curious.i say a th350 would be worth about 5-10 more hp than a th400.and a 4l60e robs about the same as a th400.just my opinion.on a side note,my 99z went from 302rwhp to 283-285 rwhp just by adding a vig2800.so thats about right ,nearly 30hp.
