voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Mon May 03, 2021 5:22 pm

LeftieBiker wrote:
Mon May 03, 2021 4:36 pm
I'm guessing that the other reason the Tesla drive is so much more robust is that the Model S is a substantially heavier car than either the Leaf or the Bolt. It has to push against all that additional mass whenever you step on the accelerator, and the harder you step the more force is being applied to it...
You would still need the same Tesla heavy-duty transmission in a customized Leaf fitted with a Tesla motor. The way it works, a powerful electric motor will still reach high torque levels up to the back-EMF dominated higher RPM area, regardless of the body mass attached to it. The variable here is acceleration only. Accel = Thrust / mass

And that would be a Rocket Leaf ! F = MA means the lighter body Leaf would accelerate even faster than a heavier Tesla body. Wider stickier tires like a Tesla has, means it's possible to stuff a Tesla motor in Leaf. You might need some extra battery to supply full amps though. Teslas have 85 to 100 kWH ginormous go-boxes down under with wide parallel banks for high amps.

I wonder if anybody has tried to install a Tesla Model S battery, motor, etc. on the back wheels of a Chevy Silverado, that would be nice. No need for an ICE engine up front either. Big frunk there. Off topic.
I have heard of a Leaf powertrain in a Miata, which produced a fun hot-rod.
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Nubo
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Re: Reduction Gear Oil Change - Benefits for Range

Tue May 04, 2021 12:11 am

voltamps wrote:
Mon May 03, 2021 3:00 pm
...
I like the part where John Kelly mentions the Silicon Nitride ceramic motor shaft support bearings.
Nubo mentioned the "milling noises" some early Teslas were vexed with, & the ceramic bearings prevent micropitting from the induced current off the motor's fields (or maybe ground current), solving the problem. They are sealed grease bearings on the Tesla and don't share the Dexron VI fluid like the gearbox is bathed in.
Interesting. Iirc, it's common to use shaft brushes to try and make sure the bearings aren't the best "path" for current but maybe that wasn't sufficient.
I noticed you're still working with polymers.

knightmb
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Re: Reduction Gear Oil Change - Benefits for Range

Wed May 05, 2021 12:45 pm

I'm over +3,000 miles in my current gear oil change experiment, so at this rate, I should have a good amount of mileage by summer when I do the change. Will be able to inspect the magnets and send in another sample to Blackstone Lab to see if an abnormal bits of metal are floating around inside the changed oil. So far so good, my weekly efficiency keeps increasing as the weather gets warmer, starting to hit the 270's range on the GOM :mrgreen:
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voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Wed May 05, 2021 4:33 pm

knightmb wrote:
Wed May 05, 2021 12:45 pm
efficiency keeps increasing as the weather gets warmer
It's possible to put in an adjustment due to temperature, accounting for hot or cold temps affecting mile/kWH usage. Approx, but close enough. .....
Average Energy Economy figure gets reduced by 0.05 miles/kWH "Energy Economy" per degree F. That way you can account for the different temperatures.

The perfect max economy driving temperature, assuming your thermostat is set at 70F for automatic cabin heating or cooling, is about 69F to 73F outside ambient or so. Outside of that ambient, adjust by 0.05 for every degree F deviation, either hotter or colder, to be approximate, based on an Idaho National Labs paper I read.

Instead of 0.05, could be 0.03 is more like what our 2020 models do. 'Splaining below:

Example: Say outside ambient temp is 60F, so that's about 9F from "ideal". 9 x 0.05 = 0.45 miles/kWH Energy Economy reduction.
If it's 30F outside, take 39 x 0.05 = 2 miles/kWH decrease adjustment. That almost sounds excessive, so let's look at the reference source:
From the paper at https://avt.inl.gov/sites/default/files ... ne2016.pdf for a 2015 Leaf S with a resistance (toaster oven) heater, so maybe our 2020 models with heat pumps are more like 0.03 for every degree F. So 39 x 0.03 = 1.2 miles/kWH Energy Economy reduction when driving in 30F ambient, delta 39F from the ideal 69F.

This would basically work for driving in hotter temperatures too, higher than the ideal 69f-73F range. If driving around with 85F outside, that would be 12 degrees higher than ideal, so 12 x 0.03 adjustment to account for air conditioner usage & a little less battery efficiency, people have found from experience.
2020 Leaf SV - sold - I'll get another EV later...Reserved the irresistible Maverick Hybrid, here in a few months
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voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Wed May 05, 2021 5:01 pm

Just to clarify the results from that Idaho National Labs paper, here is the procedure in a nut-shell:

Say you're out in TN driving and it's 83F out, and your climate control setting is at 70F, which means the AC is on most of the time.
Take 0.03, multiply that by the diff between 83F and the ideal 73F, which is 10F, to get 0.03 x 10 = 0.3 miles/kWH adjustment to ideal conditions. Adjust all readings back to ideal conditions to compare apples to apples going forward.

Of course you also want to have your tires set to whatever the placard on the door jamb cold psi (my '20 SV tires are a different size as yours, and mine is for 36 psi cold. I don't know what it says on the '20 SL Plus models with diff tires..)
Last edited by voltamps on Thu May 06, 2021 5:41 am, edited 1 time in total.
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LeftieBiker
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Re: Reduction Gear Oil Change - Benefits for Range

Wed May 05, 2021 5:49 pm

The recommended tire pressures for the Leaf (any generation) are an automatic handicap. If I wanted to compare several EVs for range and/or efficiency, I'd inflate all of the tires to 90% of the tire manufacturers' maximum recommended sidewall pressure.
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voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Thu May 13, 2021 5:05 am

The benefits of going from a Nissan Matic S to a thinner Valvoline ULV fluid in ye ole gearbox can't be more than 1%, maybe 4% on very cold days.

Some carefully measured evidence found:
I found a paper at https://www.sae.org/publications/techni ... 6/preview/
and Figure 7 in particular shows a comparison in transmission efficiency (planetary gearsets & bearings, with a torque convertor locked up so no losses there) between 2 different fluids, one a ULV thin one, and the other with a typical Nissan Matic S slightly thicker viscosity, at a typical Leaf gearbox temperature of 100F. At 100F there would be a signficant viscosity spread between those two fluids. In colder weather with city driving cycles, you could get a bigger spread, so in winter time the differences might balloon to 4% I'd say.

The planetary gearsets spinning on bearings resemble our setup close enough, and may even amplify the effects of viscosity a little, especially when you take into account the pumping losses in a typical locked-up automatic tranny compared to our Leaf's pure gears & bearings.

This may explain why, only now, is Ford going to Mercon ULV thin goo in the new Mustang Mach E. A small gain can be found, but small, ignored for durability concerns up to now.

There should be a small benefit in Range going from an old used fluid to a new fluid. Small metal particles could be raising friction in the ball & roller bearings a little. Can't be that much since the gearbox would overheat with too much friction.
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SageBrush
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Re: Reduction Gear Oil Change - Benefits for Range

Thu May 13, 2021 5:43 am

^^
I'd like to convert the reported friction into work to have an idea of the oil heating kinetics and drivetrain efficiency loss. How do you convert friction into work where gears are involved ?

What is the distance ? I'm inclined to say it is the same as the distance the car traveled but I am not sure. If that is correct then the energy savings are trivial -- on the order of 500 joules/km or ~ 0.22 Wh/mile per gear
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03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
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voltamps
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Re: Reduction Gear Oil Change - Benefits for Range

Thu May 13, 2021 7:06 am

The paper is nice because it isolates a Range loss due to just the change in gearbox fluid viscosity alone.

Torque x Rotation Degrees is energy expended, and also Force x Distance at the tire interface to the road is energy expended, basically.
Energy Units can be kWH, joules, calories, all the same energy but in different units, like feet & meters r diff units for the same thing.

Power is the rate of change of energy (time derivative of energy) per time unit. If you integrate Power over time you get Energy expended.
All basic physics.

In our gearbox, the energy wasted is the integral of Power over time needed to overcome viscous (hydrodynamic) friction & boundary "metal-on-metal" friction inside, producing waste heat. A good analogy is a leaky garden hose: Some water leaks out, lost water, which reduces the water flow you get at the important nozzle.

When you integrate Power losses to compute Energy loss, the percent loss get preserved in the total Energy lost over time. So the lab results FEV ran for Ford, GM, & Chrysler (Stallantis) in the paper I cited above really is the Range percent lost due to gearbox friction from all sources.
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Re: Reduction Gear Oil Change - Benefits for Range

Thu May 13, 2021 7:32 am

voltamps wrote:
Thu May 13, 2021 7:06 am
The paper is nice because it isolates a Range loss due to just the change in gearbox fluid viscosity alone.
Spell it out for the dummies like me, please.

Am I wrong in my ~ 0.22 Wh/mile traveled per gear estimate ? **


**
Rather than multiple force by angular velocity, I multiplied force by the car travel distance
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
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2018 Tesla Model 3 LR, Delivered 6/2018

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