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      05-20-2018, 10:08 AM   #1
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AWD vs RWD Drivetrain Loss

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The M5 is the perfect car to test drivetrain loss as it has both and has ecaxtly the same weight.

Of course the M5 in AWD mode is much faster than RWD but that’s only because of traction.

Anybody tried comparing both modes after 60 MPH for examle 60 MPH to 125 MPH ?

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      05-20-2018, 03:39 PM   #2
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So are you asking us to break the law and speed? Not on this forum buddy. No one here ever exceeds the posted speed limit. Even if being chased in NJ.

Mike.

PS. I'll give it a try tomorrow and let you know.
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      05-20-2018, 04:08 PM   #3
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Quote:
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So are you asking us to break the law and speed? Not on this forum buddy. No one here ever exceeds the posted speed limit. Even if being chased in NJ.

Mike.

PS. I'll give it a try tomorrow and let you know.
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      05-20-2018, 04:44 PM   #4
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Dry: AWD is much better on most cars over 500hp at anything below insane speeds

Wet: AWD
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      05-20-2018, 05:12 PM   #5
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I’ve been under the assumption that 60mph+ would be faster in RWD because of drivetrain loss. Please correct me if I’m wrong?
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      05-20-2018, 06:51 PM   #6
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I thought the car is rear wheel drive until front wheel traction is needed. In a straight line once at speed, when would awd ever kick in unless in wet or snow? I think there would be essentially no difference in either mode once at speed.
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      05-20-2018, 10:51 PM   #7
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Quote:
Originally Posted by GAM5OVR View Post
I’ve been under the assumption that 60mph+ would be faster in RWD because of drivetrain loss. Please correct me if I’m wrong?
Awd won't engage unless there is traction issue, so result must be the same.
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      05-21-2018, 01:08 PM   #8
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The question of drivetrain loss is interesting in this kind of setup where the front wheels drive is disconnected electronically. I guess it depends on where the disconnection occurs. There is still the 'drivetrain' loss associated with the two drive axels going into the front differential and the rotating mass associated with those shafts. So it depends on where the disconnection occurs. And how that is accomplished.

So I suspect the differences in "drivetrain" loss at speed (i.e. going from 60 to 120) probably is not that different from AWD mode to RWD mode.

I'd like to see what the actual anatomy of the AWD system is before trying to determine if much drivetrain loss is recaptured in RWD mode. The Audi AWD systems are 100% mechanical and can move all torque to one wheel (front or back) based on traction. The powertrain loss in the Audi's is always the comparison issue when comparing "power at the wheels" in pissing contests but the fact remains, the Audi RS6 was able to put down the power better then the same year M5 because of AWD. And in that year 2003, the RS6 was the king of the hill. What happened since then? Mercedes and BMW adopted two things: AWD and Turbo's. .... Old tech for Audi (and even Subaru).

I suspect there is not much difference in powertrain loss in the M5 system with the AWD off, even from starting at zero. AWD rocks.

Mike
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