How to calculate drivetrain loss?

[focusedrage]

i was reading through the manual for my dsmlink, and they want a drivetrain loss number for thier dyno calculations. how can one acuratly calculate the loss in an auto awd dsm? cause usualy peopl just say 20% but that is not accurate.

 

[kpt4321]

There is no easy way.

Some dynos do coastdown tests to estimate the drivetrain losses.

You could pull the motor out and put it on an engine dyno.

 

[Luv2Spool]

Front wheel drives generally lose 15 percent, rear wheel drive will lose more like 30 to 33 percent. You also have to factor in the amount of mileage on the motor. Other than guessing, I would have to agree that pulling the motor and putting it on an engine dyno is your best bet.

 

[CanadianTSi]

rear wheel drive will lose more like 30 to 33 percent. You also have to factor in the amount of mileage on the motor.

Ummm it's more like 20% and how does mileage on a motor affect drivetrain loss???

 

[gsx91boy]

It's dependant on a million things and doesn't matter because so are dynos and the dyno time. Also everyone is an idiot and thinks that when a car dynos 800whp that is AWD it stil has a 20% loss or w/e so they think it's making astronomical power, when actually drivetrain loss starts to taper off for whatever reason when more and more power is made.

Use the dyno to tune, not to chase a number. If your number goes up, consider that successful.

-aaron

 

[Luv2Spool]

Ummm it's more like 20% and how does mileage on a motor affect drivetrain loss???

well I was speaking from personal experience after putting both of my cars on a dyno. Any ways the milage point was that a if you take two 4g63 motors, one with 10k on it and one with 110k on it and dyno them in the exact same conditions the motor with less mileage will put out more HP due to less wear.

There are just way too many variables to calculate.

 

[gsx91boy]

Any ways the milage point was that a if you take two 4g63 motors, one with 10k on it and one with 110k on it and dyno them in the exact same conditions the motor with less mileage will put out more HP due to less wear.

There are just way too many variables to calculate.

Exactly, there's too many variables. At 10k miles the motor will stil be green and bearings will be tight, and it's likely it'll actually dyno more power @100k if properly maintained.

-aaron

 

[Mike Licht]

It is not a percentage. It is more of a fixed amount that you have to add extra load in as power goes up for friction and wingage from lubricants. A 400 flywheel setup that puts 300 to the tire will NOT be 900 at the tire if we install a 1200HP motor. more like 1050 or so. Some dynos have a feature that will measure drivtrain losses.
Mike

 

[ahains]

It is not a percentage. It is more of a fixed amount that you have to add extra load in as power goes up for friction and wingage from lubricants. A 400 flywheel setup that puts 300 to the tire will NOT be 900 at the tire if we install a 1200HP motor. more like 1050 or so. Some dynos have a feature that will measure drivtrain losses.
Mike

IMHO it is a combination of static and dynamic losses.
You have certain losses that are simply RPM dependant, such as rotating mass of axles, gears, etc.
You have other losses that are dependant on the amount of power being put out. They may not be a linear percentage, but they are affected by power output. I believe it is a "hypoidal" gear that has kind of a cross mesh, where the friction between each gear increases as load increases. I don't know anything about DSM trannies, or much about trannies in general, but my SWAG would be that there are gears similar to this in our drivetrain.

You may very well be correct though that the static losses are much more significant than the dynamic, so that the overall drivetrain loss will be similar between a stock and highly upgraded car. I'm just throwing some ideas out there.

-Adrian

 

[Mike Licht]

Adrin,
You are exactly right. Gears bearings and such increase load and friction with more RPM and also with more power. Oil temp has an infulence as well. We had a dyno that would measure this and we did lits of testing. Bottom line there is no formula or math that will tell the tale
Mike

 

[kpt4321]

In addition, you will see losses due to the energy "wasted" to accelerate all of the rotating components in the engine and drivetrain (flywheel, clutch, gears, driveshaft, axles, wheels, and much more). The power losses of these components are diectly proportional to the rate of acceleration; if you're accelerating them more slowly, they do not sap as much power that the dyno would otherwise read.

For this reason, on an inertial dyno dynoing in higher gears will tend to lead to higher power numbers, since everything is coming up to speed more slowly. On dynos that have adjustable resistance (eddy current), the resistance and ramp rate settings can greatly effect power output.