Das Beast, 3.0T Conversion Update. Dawn of Darkness Draws Near; Something Wicked This Way Comes...
10-10-2007, 01:48 PM
#112
AudiWorld Super User
Join Date: May 2001
Posts: 5,944
Likes: 0
Received 0 Likes
on
0 Posts
The extra heat comes from the engine which is absorbed by the engine cooling system and also goes
out the exhaust. I don't see how the extra heat is put into the drivetrain?
The heat loss from the engine won't show up on either a chassis or engine dyno.
The heat loss from the engine won't show up on either a chassis or engine dyno.
10-10-2007, 01:50 PM
#113
AudiWorld Super User
Join Date: Feb 2003
Posts: 16,402
Likes: 0
Received 0 Likes
on
0 Posts
You've just answered the question. Think for a second...why does the fluid get hot?
Where does the energy that is making the fluid hot come from?
The energy used to heat the transmission case, gears, and fluid is energy from your engine that never makes it to the wheels. Instead, it's wasted energy that becomes driveline loss.
If you spun a transmission with your hand, it would never get above room temp. Put a load through it, and it will heat up very quickly.
The energy used to heat the transmission case, gears, and fluid is energy from your engine that never makes it to the wheels. Instead, it's wasted energy that becomes driveline loss.
If you spun a transmission with your hand, it would never get above room temp. Put a load through it, and it will heat up very quickly.
10-10-2007, 01:59 PM
#114
AudiWorld Expert
Join Date: Jan 2005
Posts: 34,704
Likes: 0
Received 0 Likes
on
0 Posts
if loss stays at a static percentage...
say 25%... 25% of 200 is only 50, whereas 25% of 400 is 100...
even though the percentage is the same, the amount of energy being lost (to heat) doubles, so you need the extra cooling.
I'm not arguing that it doesn't change, just playing devil's advocate to your "cooling" argument.
even though the percentage is the same, the amount of energy being lost (to heat) doubles, so you need the extra cooling.
I'm not arguing that it doesn't change, just playing devil's advocate to your "cooling" argument.
10-10-2007, 02:01 PM
#115
I thought they were talking about Drivetrain loss/heat. Not engine.
Drivetrain energy loss = Drivetrain heat and noise.
as we have discussed before, I think all of the above (Drivetrain energy loss/heat) will increase as you transfer more power through the gears. However (as you have said), a 50% increase in power doesn't equals anything close to a 50% increase in drivetrain loss.
as we have discussed before, I think all of the above (Drivetrain energy loss/heat) will increase as you transfer more power through the gears. However (as you have said), a 50% increase in power doesn't equals anything close to a 50% increase in drivetrain loss.
10-10-2007, 02:01 PM
#116
AudiWorld Expert
Join Date: Jan 2005
Posts: 34,704
Likes: 0
Received 0 Likes
on
0 Posts
I'll volunteer to shoot and cut some HD video of it when it gets back to SD...
If sarge is willing, of course.
something along the lines of <a href="http://www.youtube.com/watch?v=y9ksr6XksZc">this</a>, maybe?
something along the lines of <a href="http://www.youtube.com/watch?v=y9ksr6XksZc">this</a>, maybe?
10-10-2007, 02:02 PM
#117
AudiWorld Super User
Join Date: Feb 2003
Posts: 16,402
Likes: 0
Received 0 Likes
on
0 Posts
He's talking about driveline coolers, meaning transmission or differential...
As I said, the more load you put through a transmission, the more the transmission will heat up. Heat is wasted energy...it's energy the engine produces that never makes it to the wheels. It's a loss.
Just as System_S4k said, high powered cars (and trucks to tow heavy loads) all need heat exchangers and coolers to keep their drivelines from overheating. All this heat is wasted energy that increases the driveline loss. Yet, you can spin a transmission easily with your bare hand. If you hooked up a bicycle with the proper gearing, you could even spin a transmission to highway speeds, putting out less than 1 hp in the process.
You have to consider why a transmission heats up under load. Gear teeth actually slide against each other. When you put your hands together and lightly rub, you don't feel anything. If you press your hands together and rub, you'll feel heat forming. The same principle applies to driveline gears. The more force you put through them, the harder the teeth slide against each other creating more friction, and the more heat is produced which is nothing more than wasted energy and drivetrain loss.
Now, this doesn't say a percentage is the most accurate method of calculating driveline loss. It isn't...although it is more accurate than assuming a fixed value that doesn't change. You have three frictional conditions to contend with (asperity, hydrodynamic, and mixed) as well as friction from all the seals. It's complicated to say the least.
One thing is for sure though, the first law of Thermodynamics guarantees that driveline loss cannot be fixed as the system will heat up when power input is increased.
Just as System_S4k said, high powered cars (and trucks to tow heavy loads) all need heat exchangers and coolers to keep their drivelines from overheating. All this heat is wasted energy that increases the driveline loss. Yet, you can spin a transmission easily with your bare hand. If you hooked up a bicycle with the proper gearing, you could even spin a transmission to highway speeds, putting out less than 1 hp in the process.
You have to consider why a transmission heats up under load. Gear teeth actually slide against each other. When you put your hands together and lightly rub, you don't feel anything. If you press your hands together and rub, you'll feel heat forming. The same principle applies to driveline gears. The more force you put through them, the harder the teeth slide against each other creating more friction, and the more heat is produced which is nothing more than wasted energy and drivetrain loss.
Now, this doesn't say a percentage is the most accurate method of calculating driveline loss. It isn't...although it is more accurate than assuming a fixed value that doesn't change. You have three frictional conditions to contend with (asperity, hydrodynamic, and mixed) as well as friction from all the seals. It's complicated to say the least.
One thing is for sure though, the first law of Thermodynamics guarantees that driveline loss cannot be fixed as the system will heat up when power input is increased.
10-10-2007, 02:06 PM
#120
AudiWorld Expert
Join Date: Jan 2005
Posts: 34,704
Likes: 0
Received 0 Likes
on
0 Posts
no, the cooler just gets the heat away from the components that it's trying to cool
it doesn't mean that less heat (friction) is being generated, just that it's being diverted elsewhere.
take, for instance, the exhaust fan above your stove. Cook your meal with it off and your kitchen will get hot.
Turn it on, and your kitchen will cool off... but the temperature that your stove or oven is cooking your food at does not change.
Not the most accurate analogy, but it's a start.
take, for instance, the exhaust fan above your stove. Cook your meal with it off and your kitchen will get hot.
Turn it on, and your kitchen will cool off... but the temperature that your stove or oven is cooking your food at does not change.
Not the most accurate analogy, but it's a start.