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Old 05-14-2013, 04:22 PM   #17
dertobi
 
Drives: none
Join Date: Nov 2011
Location: germany
Posts: 14
Hi guys, just to let you know, I am Arno's second engineer @EDS...


Quote:
Originally Posted by KMPrenger
Just showing you what we are used to seeing here. It has been said that as a rule of thumb, manuals tend to show 15% loss and autos tend to show 20%.
Correct, it is a rule of thumb...nothing less or more... pub science in my eyes...that's what it is.

if you want to have a proper measurement, you cannot estimate half of it, and than state that the result is correct...thats complete guessing nothing else.

but that is the mayor problem with your dyno charst in the US, you cannot compare them and in every gear you will see different results.
the only thing you can use this measuring for, is the compare one single cars gains (e.g. for the benefit of a tuning), when you look at the difference between before and after


what leads to your next question:

Quote:
Originally Posted by KMPrenger
So are you saying that much of the loss shown on these graphs is due to the dyno rollers themselves, and NOT because of drivetrain loss??
No it is NOT, with different rollers you would see a different drivetrain loss value, but also different wheel power, because the flywheel power is always the same.

if the drivetrain loss is higher, the wheelpower would be lower and vice versa... it is an easy equation:

Flywheel_pwr = Wheel_pwr + loss

[edit]: and: loss = cars secific drivetrain loss + "roller loss"(most friction)

so its easy to see what has to happen when the left side is always constant , and the values from the right side differ

hope U understand what we want to say

best regards

Tobi
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