Model 3 wheel aerodynamics

[surfdabbler]

I've been looking at the model 3 wheels and covers, and wondering about how the aerodynamics are meant to work. I've heard that the covers add an extra 5% of range. Presumably there is some similar effect from the design of the performance wheels.

The performance wheels, and the aero covers on the SR+ are not symmetric. The fins are designed like a turbine, as if during rotation, they are designed to blow air out (or maybe in?).

So, here's my question - are they meant to blow air out or in, or just stop air passing through?

If they are designed to blow air in or out, then they should be different on opposite sides of the car, and would have to be kept that way when the wheels are rotated. However, I am seeing that all the wheels are the same design, meaning they would blow out on one side of the car, and in on the other. There are some pictures on the net of wheels going the opposite way, but I wonder whether they might be just mirrored images.

My model 3 has the aero covers, and they are all the same design, no inverted for the other side of the car. So, perhaps the 'turbine' look of the wheels is for looks only, and all it really does is block air from going in/out of the wheel?

 

[Clivew]

The turbine wheels are all the same design to keep costs down, and to prevent wheels being fitted on the wrong side, or mismatched etc.

All aero style wheels are designed to reduce aerodynamic and ventilation drag. Aerodynamic drag is the drag caused by the air flowing across the wheel and tyre face, and ventilation drag is caused by the high pressure air in the wheel well flowing out past the wheel spokes. The turbine design has been tested and is fairly efficient compared to other designs, although all being the same design increases the drag penalty.

The more efficient the spoke design, the lower the ventilation drag, and a smaller diameter wheel of the same design also produces less drag. This and tyre type are the main factors that effect the efficiency of the wheel/tyre package.

 

[holmgang]

It's less to do with bladed/turbine "effect" than simply presenting a flat'ish surface for air to flow across.

If you look at the low drag wheels for other efficiency-centric vehicles, they all tend to be closed surfaces.

 

[Clivew]

It's less to do with bladed/turbine "effect" than simply presenting a flat'ish surface for air to flow across.

If you look at the low drag wheels for other efficiency-centric vehicles, they all tend to be closed surfaces.

For aerodynamic drag, yes, a flat cover is most efficient, but with a performance car like the Tesla, the wheel well is an area of high pressure which creates lift, so there must be openings in the wheel to help promote airflow through the wheel. Also, there is a lot more airflow required through the brake disc for cooling, and this also flows through the wheel. All this airflow is called ventilation drag and is a major contributor to total aerodynamic wheel drag.

The turbine spoke design is a good compromise between ventilation drag efficiency and cosmetic appearance, thus why Tesla chose it.

 

[holmgang]

For aerodynamic drag, yes, a flat cover is most efficient, but with a performance car like the Tesla, the wheel well is an area of high pressure which creates lift, so there must be openings in the wheel to help promote airflow through the wheel. Also, there is a lot more airflow required through the brake disc for cooling, and this also flows through the wheel. All this airflow is called ventilation drag and is a major contributor to total aerodynamic wheel drag.

The turbine spoke design is a good compromise between ventilation drag efficiency and cosmetic appearance, thus why Tesla chose it.

The aero covers are specced on the smallest wheel on the base spec model 3 with smaller brakes and the most economic tires

I doubt reducing front end lift or enhanced brake cooling was the primary design target (vs merely reducing drag)

If the purpose of the blades were to serve those purposes, they would be incorporated into design of the 19s and 20s.

 

[surfdabbler]

Thanks for all your thoughts on this. Makes sense.

 

[Gasaraki]

Yeah the aero caps are designed to allow as little air to get to the wheels as possible and tehy are designed with the turbine design to "cut through" the air when they spin forward.

 

[Clivew]

The aero covers are specced on the smallest wheel on the base spec model 3 with smaller brakes and the most economic tires

I doubt reducing front end lift or enhanced brake cooling was the primary design target (vs merely reducing drag)

If the purpose of the blades were to serve those purposes, they would be incorporated into design of the 19s and 20s.

I’m talking about the turbine wheels that are fitted to the 165mph performance model. High pressure air from the wheel well flowing though the wheel is a big factor of aero drag.

No where did I state reducing lift and brake cooling was the primary design of the wheel.

Regardless of that, the 18” aero wheel also reduces ventilation drag due to the high pressure wheel well air flowing through the wheel. If that wasn’t the case, the cover would be a flat smooth disc with no openings.

 

[holmgang]

I’m talking about the turbine wheels that are fitted to the 165mph performance model. High pressure air from the wheel well flowing though the wheel is a big factor of aero drag.

No where did I state reducing lift and brake cooling was the primary design of the wheel.

Regardless of that, the 18” aero wheel also reduces ventilation drag due to the high pressure wheel well air flowing through the wheel. If that wasn’t the case, the cover would be a flat smooth disc with no openings.

this is the model 3 forum and every post has referred to the model 3, which was never stocked with any "turbine" wheels. the only one in the model line with any turbo blade/vane-like feature are the aero covers on the 18s

 

[Clivew]

this is the model 3 forum and every post has referred to the model 3, which was never stocked with any "turbine" wheels. the only one in the model line with any turbo blade/vane-like feature are the aero covers on the 18s

The M3P 20" wheels are shaped exactly like turbine blades, I'm not interested in their official name, and it makes absolutely no difference to this discussion.

Regardless of what the wheels are called, all the Model 3 wheels either with aero covers, 19" or 20" are designed to allow airflow through the wheel, with as little ventilation drag as possible. If brake cooling wasn't needed (which it is on all Model 3 cars) the wheel covers would be smooth covers, with no vents.

Airflow is always from the wheel well outwards, not inwards.

 

[holmgang]

The M3P 20" wheels are shaped exactly like turbine blades, I'm not interested in their official name, and it makes absolutely no difference to this discussion.

The M3P 20" are NOTHING like turbine blades. you realize on the INBOARD side of the wheel, the surface is essentially FLAT? i.e. no bladed effect.

Airflow is always from the wheel well outwards, not inwards.

you also realize, IF the spokes were meant to act as functional vanes, one side of the car would have air scooped INTO the wheel (blue car), and the other side of the car would have air vented OUT from the wheel (white car)?

If brake cooling wasn't needed (which it is on all Model 3 cars) the wheel covers would be smooth covers, with no vents.

SOME brake cooling and pressure relief is needed, thats why almost no covers are solid discs.


the design parameter with first order effect for low drag is large surface area. there are hundreds of data points to support this. look at the wheels of an insight or prius or peugeot 208 or vw insight or any other eco-centric to inform you.

the "BLADED" effect is a quinary effect at best, completely trumped by aesthetics element. there are thousands of data points to support this. do you see any turbines or vanes in the wheels of a veyron or gt2 rs or 458 or aston martin or any car that goes 200?



the bladed effect is. non. existent.

here's the easiest proof of all: if the blades on tesla wheels were a functional element, why arent a set of them unidirectional?

 

[Clivew]

The M3P 20" are NOTHING like turbine blades. you realize on the INBOARD side of the wheel, the surface is essentially FLAT? i.e. no bladed effect.

Looking at the wheel and spoke design visually, they look like turbine blades, and it’s the outer surface shape that is important in regards to ventilation drag. I wasn’t carrying out an in depth design analysis of the spoke cross section compared to an actual turbine blade, it was a simple term to identify the wheel spoke design.

you also realize, IF the spokes were meant to act as functional vanes, one side of the car would have air scooped INTO the wheel (blue car), and the other side of the car would have air vented OUT from the wheel (white car)

Nowhere did I state they were designed as functioning blades to move airflow. (why do you keep implying things that were not written?)

I stated they were designed to reduce ventilation drag. The inner surface isn’t important for reducing ventilation drag, and yes, the fan blade ‘out’ design is more efficient, but as I stated in my initial post, Tesla used the same wheel for cost and simplicity of fitment.

SOME brake cooling and pressure relief is needed, thats why almost no covers are solid discs.

Why are you repeating what I already wrote?

the design parameter with first order effect for low drag is large surface area. there are hundreds of data points to support this. look at the wheels of an insight or prius or peugeot 208 or vw insight or any other eco-centric to inform you.

And what has this got to do with the OP’s question? I’ve already stated the facts. The wheel and tyre create aerodynamic and ventilation drag. A flat cover produces the least aerodynamic drag, but this can’t be used due to brake cooling and reduction of wheel well pressure, so a turbine blade design was used by Tesla, as this is an efficient design in reducing ventilation drag. (There are plenty of studies to support this)

the "BLADED" effect is a quinary effect at best, completely trumped by aesthetics element. there are thousands of data points to support this. do you see any turbines or vanes in the wheels of a veyron or gt2 rs or 458 or aston martin or any car that goes 200?

So, you’re comparing a Veyron, GT2, 458 etc to a Tesla M3 in regards to reducing wheel drag to maximise efficiency?

Please post ONE date point showing the fan blade design as being inefficient in regards to ventilation drag?

the bladed effect is. non. existent.

Really, this study disagrees - https://core.ac.uk/download/pdf/70600281.pdf

here's the easiest proof of all: if the blades on tesla wheels were a functional element, why arent a set of them unidirectional?

I highly recommend you read and understand what is actually written, instead of making things up in your head that you THINK has been written. The spokes are not designed to suck, blow or move airflow like a fan blade, and that hasn’t been written by me anywhere. They are designed to reduce ventilation drag, and the reason they are all the same is due to cost and simplicity of fitment, as I’ve stated multiple times before.

 

[holmgang]

The turbine wheels are all the same design to keep costs down, and to prevent wheels being fitted on the wrong side, or mismatched etc.
.

We've established they don't function as turbines. They also dont look anything like turbines.

And how could they possibly ever be "fitted on the wrong side" or "mismatched", that these design help prevent?

 

[qingshan]

It's less to do with bladed/turbine "effect" than simply presenting a flat'ish surface for air to flow across.

If you look at the low drag wheels for other efficiency-centric vehicles, they all tend to be closed surfaces.

Think of the spun aluminum covers on land speed cars. The difference being brake cooling and the ducting discussed.

 

[holmgang]

Think of the spun aluminum covers on land speed cars. The difference being brake cooling and the ducting discussed.

singularly-focused vehicles vs road-going passenger cars. not just classes apart, but worlds apart

 

[Clivew]

We've established they don't function as turbines. They also dont look anything like turbines.

I never, ever said they function liked turbine blades, that was something you made up in your own head due to your inability to read and understand what I had actually written.

Whether they look like turbine blades is obviously subjective, and not in any way the main focus of the discussion. But I suppose when you have got everything else wrong, you need to clutch at straws.

Anyway, I have posted a picture of a fan blade I own (from an Airbus A320 CFM56-7) and a picture of one of the spokes from my car (which are handed differently). I think normal people can see the similarity.

There are other companies that think they look like turbine blades also - EVT Wheel for Tesla Model 3 - 19" & 20" ("Turbine" Style)

Funny that, eh.

And how could they possibly ever be "fitted on the wrong side" or "mismatched", that these design help prevent?

That is exactly the point I was making, with the design they are, they cannot be fitted wrong and are also cheaper to manufacture than if they were handed.

If they were handed, like directional tyres, they could be fitted incorrectly.

 

[qingshan]

singularly-focused vehicles vs road-going passenger cars. not just classes apart, but worlds apart

Of course, it was only suggested as an analogy not a suggestion.

I put m3 oem covers on, for longdrives, for efficiency. I take them off the rest of the time for aesthetics (when I figure a way to make them look like flowers that get my wife's approval they can stay on)