silentsnow31802
Member
Im seeing about a 4% difference between aero covers and no aero covers over the span of 1800 miles so far. Have not quite hit the end of my testing yet though.
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Aero Efficiency
- Thread starter stuckintraffic
- Start date
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- Tags
- Model 3
insaneoctane
Well-Known Member
insaneoctane
Well-Known Member
I watched the inital video that thread was based on. Excellent first shot to capture and share a relatively simple comparison. My question for those here is this: If we are only talking about ~4% difference, that is relatively small. How much would having Tesla logo caps have here? I'd agree it's very small, but when you're talking about 4%, I'm beginning to wonder!
silentsnow31802
Member
Oh I should mention the test im doing had lug caps and center caps installed onto the factory wheels.
My test is also not very controlled. I am just driving like I normally do to and from work at 80MPH and at the same times of the day. I am however doing it over a much longer period of time. My commute is 72 miles one way and im doing roughly 2500 miles per full test.
Syclone
Member
It would be interesting to see the real world difference between 18" wheels and tires with Aero covers vs the 19" wheels and tires. I'd assume the total weight of the 19" setup is a bit more and I believe the 18" come with Michelin Primacy mxm4 low rolling resistance tires. Probably at least 8-10% better running the 18" wheels and tires with aero covers installed.
Tire Rack link to 18" Tesla OE tires: Michelin Primacy MXM4
Tire Rack link to 18" Tesla OE tires: Michelin Primacy MXM4
T34ME
Active Member
SageBrush
REJECT Fascism
Yes, but 10% of what ?
People are I think jumping to the conclusion that the reduction is in energy/mile for the car,
when IIRC he was talking about Aero friction.
T34ME
Active Member
I don't think I know the difference between energy/mi and aero friction. Too esoteric for me. The other thing is, how was the LR tested by the EPA. Is the purported 310 mile range with 19" Sportwheels or 18" Aero wheels? Should the 10% be added to the 310 mile range or deducted from that range?
Hank101
Go Tigers!
Gotta paint those Aero covers silver/aluminum, especially on a white car - whew, there, I said it.
SageBrush
REJECT Fascism
Energy/mile is proportional to ALL the forces acting on the car, of which aero is only one -- albeit a very important one.
As a rule of thumb, aero is about half of the total losses at highway speeds.
So a 10% reduction in aero translates into a ~ 5% reduction in overall losses per mile (or a 5% gain in range.)
T34ME
Active Member
RED FLAG ALERT! Whose rule and whose thumb?
The data that Tesla submitted to the EPA indicated that energy consumption of the 18" Aero wheels was 10% less than the 19" Sport wheels. The Road Load HP at 50mph was 9.95 for the 18" and 11.13 for the 19", see table below.
The EPA test indicated the 3 LR has a range of 334 mi, however Tesla choose to lower the 3 LR EPA range to 310 mi. The 334 mi range is based on the 18" Aero wheel configuration. I haven't looked at it closely, but I think the 3 LR with 19" Sport wheels would get about 300 mi following the EPA test.
Source: Model 3 epa | Battery Charger | Dangerous Goods
"aero is about half of the total losses at highway speeds" is a good roll of thumb. My current model of the 3 LR, with Aero wheels, shows the aero drag at 65mph is 50% of the total. At 70mph it's 54% of the total:
So the 18" wheels use 10.6% less energy than the 19" wheels. But that also means that the 19" Sport wheels use 11.9% more energy. So if the covers are only responsible for 4% of that, that means the wheel size/tire combo is responsible for the other 7.9%. (And since that is only at 50 MPH, the difference is likely to widen as speed go up.)
suwaneedad
Member
I'd love to see @Zoomit graph the difference in Wh/mi total consumption at various speeds between the 18s w covers, and the 19s, so that we can all see the efficiency delta where it really matters: 70-80mph on the highway. Any chance you have what's needed, and the time, to map that out @Zoomit? I really prefer the look of the 19s, but would like to know what I'm sacrificing in highway range by buying them. The "10%" answer may be materially wrong, since 70-80mph is the relevant range for (my) highway driving speed. Cheers.
I built a set of simple models based on the three dyno coefficients that Tesla provided to the EPA and shown in post #33 above. These models are approximate and should be considered skeptically until validated with empirical data, but show a minor trend I didn't expect.
The 19" wheel/tire combination appears to have an increasingly detrimental effect at lower speeds. This trend is not obvious looking at the second graph just showing Range Lost and Consumption Increase, but is obvious when the percentages are plotted in the third graph.
If this is trend is real, I suspect it is caused by the higher rolling resistance of the 19" tires, which appears to be more dominant at slower speeds. These models assume constant speeds, no acceleration/deceleration, so the effects from the different wheel/tire rotational inertias isn't a factor. In total, this trend is a very minor, being only a few percentage points different over this range of speeds.
Again, I wouldn't focus on the specific values. They could easily be off, but I think the big trends are real.
insaneoctane
Well-Known Member
ElecFan
Member
Thanks Zoomit. So you're model suggests between 9-10.4% range loss. Since we've seen reports of -4% in (preliminary) real world tests, I guess the real range loss should be between 4 to 4.7% @85-55mph. A .7 percent point increase. Like you wrote: 'very minor'.
Every little bit helps, I guess.
