Drivetrain loss vs converter slip ?

434nova

Active Member
Sep 30, 2013
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What would be a good safe number for our cars on the drivetrain loss on a dyno. 10% 15% 20% ? Also if your car has a converter slip of 8% is that what’s being loss through the drivetrain or is that something different.
 

No disintegrations

Active Member
Dec 27, 2015
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I'm of the opinion that the rear axle soaks up the most, unless a poor performing torque converter is in place.
For me:
1 rear axle
2 transmission pump
3 possibly under performing torque converter. ( Could be # 1 or 2 depending how bad.)
 

Nigel

Active Member
Jun 16, 2001
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Nassau, NY
Some decent info is on the web and the board about torque converters, you have to search and dig for it though. Dragzine has some decent articles.

This is not going to answer the question, but to really answer that question you would need a dyno rig for testing torque converters to answer the torque converter part. This is probably going off track on my part if you are only looking to compare a peak engine dyno figure to a peak chassis dyno figure.

The rig would have to be able to simulate what is happening down the quarter, and have factors for all of the variables, ie power and torque curves, gearing, weight, fluid temperature, ability to test starting line, launch, and acceleration through the run.

Torque converters can convert engine power to torque when the conditions produce a reaction at the stator. This happens with large differences between the impeller and the turbine speeds. It really acts like a gear reduction, it can only take what the engine is producing and convert power to torque, so if you are driving the impeller at a speed that is outside of the meat of the engines power you are losing output regardless of how well it is converting power to torque at a given condition. This is not necessarily a loss of efficiency, but a less than optimal arrangement.

Once the turbine speed approaches the impeller speed, it is highly likely that all of the slip is a loss of efficiency. This will show up as heat in the fluid. (You will also generate a great deal of heat staging because you have a ton of power going in, but no power going out until you release the break. All of the engine power is heating the fluid.)

In all cases, and this would be difficult to measure, efficiency will equal power out divided by power in.

Guys put a lot of effort into setting up a car, and while a lot of science may go into trying to figure out what is happening, a lot experimenting goes into to. I don’t think it is easy to pick a driveline loss number given the variation in components and the variation in measuring equipment.

Given the fact that a converter has to make compromises and what is good for the launch vs the back half, ascribing an efficiency number could be difficult or misleading.

If somebody has some numbers I would be curious how they arrived at those numbers. For the most part, some general thumb rules I am sure will provide OK estimates, but depending what the number is going to be used for it may not be useful.
 
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Jerryl

Tall Chinese Guy
Dec 14, 2004
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Houston, Texas
Some decent info is on the web and the board about torque converters, you have to search and dig for it though. Dragzine has some decent articles.

This is not going to answer the question, but to really answer that question you would need a dyno rig for testing torque converters to answer the torque converter part. This is probably going off track on my part if you are only looking to compare a peak engine dyno figure to a peak chassis dyno figure.

The rig would have to be able to simulate what is happening down the quarter, and have factors for all of the variables, ie power and torque curves, gearing, weight, fluid temperature, ability to test starting line, launch, and acceleration through the run.

Torque converters can convert engine power to torque when the conditions produce a reaction at the stator. This happens with large differences between the impeller and the turbine speeds. It really acts like a gear reduction, it can only take what the engine is producing and convert power to torque, so if you are driving the impeller at a speed that is outside of the meat of the engines power you are losing output regardless of how well it is converting power to torque at a given condition. This is not necessarily a loss of efficiency, but a less than optimal arrangement.

Once the turbine speed approaches the impeller speed, it is highly likely that all of the slip is a loss of efficiency. This will show up as heat in the fluid. (You will also generate a great deal of heat staging because you have a ton of power going in, but no power going out until you release the break. All of the engine power is heating the fluid.)

In all cases, and this would be difficult to measure, efficiency will equal power out divided by power in.

Guys put a lot of effort into setting up a car, and while a lot of science may go into trying to figure out what is happening, a lot experimenting goes into to. I don’t think it is easy to pick a driveline loss number given the variation in components and the variation in measuring equipment.

Given the fact that a converter has to make compromises and what is good for the launch vs the back half, ascribing an efficiency number could be difficult or misleading.

If somebody has some numbers I would be curious how they arrived at those numbers. For the most part, some general thumb rules I am sure will provide OK estimates, but depending what the number is going to be used for it may not be useful.
As stated, and I fully agree: It depends!
 

turbocamino1

turboholic
Jul 7, 2007
328
14
18
quote > "What would be a good safe number for our cars on the drivetrain loss on a dyno. 10% 15% 20% " Parasitic lose is a good search too.... the mass of all the components that need to move/turn (freely) a 200 4R vs. a th400 vs. a4L80 vs. ... the type diff type and even steel wheels vs. ?? converter lose is another animal.
 

Mr.Spool

Well-Known Member
Nov 6, 2006
4,564
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you would need a dyno rig for testing torque converters to answer the torque converter part.
nope,testing in your envirionment is the critical part.knowing your surroundings is huge.ex:its like hunting in a forest where you know the terrain and have kill zones setup,then being forced to hunt for fish in an ocean,that hunter will never be as effective right away.
 

Mr.Spool

Well-Known Member
Nov 6, 2006
4,564
650
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What would be a good safe number for our cars on the drivetrain loss on a dyno.
well if your racing a dyno the number will be x if your racing on the track the number will be x,and if your racing on the street the number may be x,there all going to be different.your never going to get all 3 to run there fastest with the same number
 

Nigel

Active Member
Jun 16, 2001
647
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Nassau, NY
what would you like to know?
Since I am of the belief that the losses from the converter will change through the entire operating range, if some one was going to try and quantify them, I would like to see an explanation of how they came by the number. The explanation would go a long way in understanding whether it was any good and what use it may be.
 

Nigel

Active Member
Jun 16, 2001
647
114
43
51
Nassau, NY
nope,testing in your envirionment is the critical part.knowing your surroundings is huge.ex:its like hunting in a forest where you know the terrain and have kill zones setup,then being forced to hunt for fish in an ocean,that hunter will never be as effective right away.
That wasn't a yes or no, it is simply a fact. If you want to know the efficiency through out the operating range you have to be able to measure power in and power out. It is not a statement about whether it works best on a certain car.
 

Mr.Spool

Well-Known Member
Nov 6, 2006
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650
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Since I am of the belief that the losses from the converter will change through the entire operating range,
define operating range?are we talking distance/et/mph or operating range of the motor?