EVDRIVER
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An experiment comparing energy losses from "thick" vs. "thin" transmission oils
Written by Roger - electric Forsa owner.
http://tech.groups.yahoo.com/group/ev/message/35167
Apr 12, 2007
RE: Sprint/Metro Drivetrain losses
I had written:
> The tranny is full of fresh 75W90 gear oil, per the manual,
> however, I've been advised that the manual is wrong and a GM
> semi-synthetic lube is what should be in there. I'm
> skeptical that the lube alone could be responsible for this
> sort of loss, but since an oil change is easier than
> rebuilding the tranny, I'll try that first ;^>
As it turns out, it seems (from checking a partial bottle remaining in
the garage) that the tranny is actually full of 80W90, not 75W90 as I
originally wrote.
I put the car on stands again (under the frame with the suspension at
full droop since the suspension angle didn't seem to affect energy
consumption in my earlier tests and I feel better with the stands under
the frame when I'm going to be getting under the car).
All following energy consumption observations are based on battery pack
voltage and current as reported by my E-Meter.
I spun the wheels in 2nd for a few minutes to warm things up first, then
measured energy use in each gear at 40kph (except 1st, which was
measured at 30kph):
5th 23.4A @ 123.5V (116.3Wh/mi or 72.2Wh/km)
4th 22.9A @ 123.0V (113.4Wh/mi or 70.4Wh/km)
3rd 25.5A @ 123.0V (126.2Wh/mi or 78.4Wh/km)
2nd 30.8A @ 121.5V (150.6Wh/mi or 93.6Wh/km)
1st 37.5A @ 121.5V (244.5Wh/mi or 151.9Wh/km)
After draining the old fluid, I poured in a half litre or so of Varsol
and spun the wheels for a minute or two to flush things out:
2nd 22.5A @ 123.0V (111.4Wh/mi or 69.2Wh/km)
This was then drained, and the tranny filled with 2.5 litres of the
recommended AC Delco Synchromesh fluid (p/n 89021808, IIRC):
5th 16.1A @ 123.0V (42kph, 75.9Wh/mi or 47.2Wh/km) (34.7% lower)
4th 17.0A @ 122.5V (42kph, 79.8Wh/mi or 49.6Wh/km) (29.6% lower)
3rd 19.7A @ 120.0V (42.5-43kph, 89.6Wh/mi or 55.6Wh/km) (29.0% lower)
2nd 22.4A @ 120.0V (39.5-40kph, 108.2Wh/mi or 67.2Wh/km) (28.9% lower)
1st 37.7A @ 118.0V (39kph, 183.7Wh/mi or 114.1Wh/km) (24.9% lower)
So, going to the [GM Synchrmesh] fluid definitely seems like a step in the
right direction, however, not nearly as large a step as is required
On the plus side, the 3rd-2nd downshift "crunch" is gone, which had been
one of the touted benefits of using this tranny fluid.
So, some progress, but the hunt for better efficiency continues...
Cheers,
Roger.
---
Just a note: the energy savings seen from the less viscous gear oil doesn't translate directly to an equal decrease in total fuel consumption (or electricity use, in this case). Only the energy difference required to spin the wheels on jack stands was measured - not the total difference to actually drive the vehicle (with all its other associated losses factored in).
Written by Roger - electric Forsa owner.
http://tech.groups.yahoo.com/group/ev/message/35167
Apr 12, 2007
RE: Sprint/Metro Drivetrain losses
I had written:
> The tranny is full of fresh 75W90 gear oil, per the manual,
> however, I've been advised that the manual is wrong and a GM
> semi-synthetic lube is what should be in there. I'm
> skeptical that the lube alone could be responsible for this
> sort of loss, but since an oil change is easier than
> rebuilding the tranny, I'll try that first ;^>
As it turns out, it seems (from checking a partial bottle remaining in
the garage) that the tranny is actually full of 80W90, not 75W90 as I
originally wrote.
I put the car on stands again (under the frame with the suspension at
full droop since the suspension angle didn't seem to affect energy
consumption in my earlier tests and I feel better with the stands under
the frame when I'm going to be getting under the car).
All following energy consumption observations are based on battery pack
voltage and current as reported by my E-Meter.
I spun the wheels in 2nd for a few minutes to warm things up first, then
measured energy use in each gear at 40kph (except 1st, which was
measured at 30kph):
5th 23.4A @ 123.5V (116.3Wh/mi or 72.2Wh/km)
4th 22.9A @ 123.0V (113.4Wh/mi or 70.4Wh/km)
3rd 25.5A @ 123.0V (126.2Wh/mi or 78.4Wh/km)
2nd 30.8A @ 121.5V (150.6Wh/mi or 93.6Wh/km)
1st 37.5A @ 121.5V (244.5Wh/mi or 151.9Wh/km)
After draining the old fluid, I poured in a half litre or so of Varsol
and spun the wheels for a minute or two to flush things out:
2nd 22.5A @ 123.0V (111.4Wh/mi or 69.2Wh/km)
This was then drained, and the tranny filled with 2.5 litres of the
recommended AC Delco Synchromesh fluid (p/n 89021808, IIRC):
5th 16.1A @ 123.0V (42kph, 75.9Wh/mi or 47.2Wh/km) (34.7% lower)
4th 17.0A @ 122.5V (42kph, 79.8Wh/mi or 49.6Wh/km) (29.6% lower)
3rd 19.7A @ 120.0V (42.5-43kph, 89.6Wh/mi or 55.6Wh/km) (29.0% lower)
2nd 22.4A @ 120.0V (39.5-40kph, 108.2Wh/mi or 67.2Wh/km) (28.9% lower)
1st 37.7A @ 118.0V (39kph, 183.7Wh/mi or 114.1Wh/km) (24.9% lower)
So, going to the [GM Synchrmesh] fluid definitely seems like a step in the
right direction, however, not nearly as large a step as is required
On the plus side, the 3rd-2nd downshift "crunch" is gone, which had been
one of the touted benefits of using this tranny fluid.
So, some progress, but the hunt for better efficiency continues...
Cheers,
Roger.
---
Just a note: the energy savings seen from the less viscous gear oil doesn't translate directly to an equal decrease in total fuel consumption (or electricity use, in this case). Only the energy difference required to spin the wheels on jack stands was measured - not the total difference to actually drive the vehicle (with all its other associated losses factored in).