Official Tesla Model 3 thread

[NeilBlanchard]

...Why do you think that a lower Cd equals less crash safety? That is simply not related - the structure and crumple zones are designed and built within the chassis, and the Cd is merely the shape of the outside of the car. Is a pickup truck safer than a car of equal size? Is the difference in safety due to the difference in Cd? Please explain ...

A lot of really low drag cars are shaped in such a way that I think it would be more difficult — read: expensive — to make them crash-worthy. I'm thinking about Elio or Aptera-style vehicles that have very low CdA figures but don't figure to be very crash-worthy (in my view). Which likely isn't fair to your point. If you are talking about a moderate CdA at the Prius level, say 5.8 (quite a big drop from the LEAF 6.9, as you well know) or even 5.0, then I agree with you that safety isn't an issue and concede your point.

My main concern for very low CdA cars is that they would tend to lose their utility, due to shape (Cd) or size (related to A). As an example, very low drag cars generally seem to use rear wheel fairings. Those would be extremely impractical in snow country. A teardrop shape makes for awkward rear seat and trunk/hatch dimensions. A low car is more difficult to enter and exit (less of an issue when one is young and flexible but a significant factor for those who are older). The height of the LEAF is one of the things I like about it: easy to enter and plenty of headroom.


If the Model 3 ended up being a scaled down version of the Model S (or X for the CUV version of the 3) that would be ok with me. But Tesla apparently intends for the Model 3 to be something quite different from a scaled down S, so I have no idea what we will get.

The Model S has virtually the SAME CdA as the gen 3 Prius. Think about that for a second.

Actually, lower drag can be safer - take the Edison2 VLC for example. The shape of the car deflects away from the object it hits, rather than wrapping around it and engaging with it. By deflecting away, it has a much longer period of time to decelerate - which means the peak G forces are much lower. The Edison2 VLC was crash tested, and it only had 17G peak on the driver, while the safe maximum is 70G.

 

[evnow]

The point is, a lower Cd is a very good thing, because you have the same size car that drives much farther.

You seem to think this is some kind of a secret that has escaped everyone else.

Designers are not stupid - this is basic, basic stuff.

What you apparently don't understand is that there is no free lunch. Trying to lower CdA compromises other things (utility, cost, looks etc). So real car designers and engineers have to grapple with this and make the right compromises.

Afteral, nobody wants a car that looks like a boeing jet and costs as much.

 

[TomT]

I dunno... I'd kind of like some winglets!

Afteral, nobody wants a car that looks like a boeing jet

 

[dgpcolorado]

The Model S has virtually the SAME CdA as the gen 3 Prius. Think about that for a second...

If that's the case, I agree that it is impressive. And I certainly hope that the Model 3 will have the same or lower Cd as the Model S, with a reduced A, due to the somewhat smaller size ("80%").

I do hope that they won't make it lower than the Model S. Besides the disadvantages in utility, when a car gets too low the risk is that it will slip under the bumper of a truck/SUV in a collision. A crumple zone doesn't do much good if that happens. And deer, the most common cause of collisions here, might come through the windshield, as happens with elk already. [Yes, local concerns!]

 

[Moof]

The point is, a lower Cd is a very good thing, because you have the same size car that drives much farther.

You seem to think this is some kind of a secret that has escaped everyone else.

Designers are not stupid - this is basic, basic stuff.

What you apparently don't understand is that there is no free lunch. Trying to lower CdA compromises other things (utility, cost, looks etc). So real car designers and engineers have to grapple with this and make the right compromises.

After all, nobody wants a car that looks like a boeing jet and costs as much.

This.

Wheel fairings on the back wheels are a no brainer from an engineering point of view to lower drag, but are suicidal from a sales perspective, so even on efficient cars they are absent. For each geek they win over, they would lose a dozen people who just don't like how it looks.

Big burly grills sell trucks and cars, but are way overkill for modern efficient cars. They add drag, so engineers have put a lot of pseudo grills on recent cars to make them look red blooded and impressive, while they are merely black plastic that is closed off in the rear to be close the drag they would have otherwise. To the trained eye it is ridiculous and laughable, but it sells cars. Same story on piping in artificial engine noise (they that is just a cost adder, and doesn't do much to performance). Same with putting alloy wheels with low profile tires on cars, it is all form over function.

You can tilt at these windmills all you want, but car sales are as much about impression as anything else. Car companies run on profits, not good will and butterflies. Even on cars that they lose money on, they will try and minimize the loss (compliance cars, and CAFE standard econobox cars) by making the cars as attractive as they can.

 

[dgpcolorado]

...Big burly grills sell trucks and cars, but are way overkill for modern efficient cars. They add drag, so engineers have put a lot of pseudo grills on recent cars to make them look red blooded and impressive, while they are merely black plastic that is closed off in the rear to be close the drag they would have otherwise. To the trained eye it is ridiculous and laughable, but it sells cars. Same story on piping in artificial engine noise (they that is just a cost adder, and doesn't do much to performance). Same with putting alloy wheels with low profile tires on cars, it is all form over function...

Sad, but true. At least the Model S is fairly good on aerodynamics and is also generally viewed as an attractive car. But I have to laugh when I see the styling cues on trucks, such as the Dodge Ram. Not subtle!

 

[GRA]

...Big burly grills sell trucks and cars, but are way overkill for modern efficient cars. They add drag, so engineers have put a lot of pseudo grills on recent cars to make them look red blooded and impressive, while they are merely black plastic that is closed off in the rear to be close the drag they would have otherwise. To the trained eye it is ridiculous and laughable, but it sells cars. Same story on piping in artificial engine noise (they that is just a cost adder, and doesn't do much to performance). Same with putting alloy wheels with low profile tires on cars, it is all form over function...

Sad, but true. At least the Model S is fairly good on aerodynamics and is also generally viewed as an attractive car. But I have to laugh when I see the styling cues on trucks, such as the Dodge Ram. Not subtle!

But, but, if pickups didn't look so aggressive, what good would they be if you suddenly had a need to tow a space shuttle? Got to be ready for that! :lol:

 

[TonyWilliams]

... somewhat less efficient induction motor — that the Model S gets relatively poor mileage compared to a LEAF. I'd be surprised and pleased if the Model 3 managed 0.25 kWh/mile at, say, 100 km/hr. I'm hoping for a more modest 0.3 kWh/mile.

Where I take issue with your numbers is the $200/kWh battery price. My assumption is that the "Gigafactory" will get that below $150/kWh when it opens and that it will drop from there. Just guessing, though.

The new motor that is in my Model 70D is likely the what will go in Model 3. It is somewhat more efficient than the original, plus smaller and lighter. No, it likely isn't as efficient as the LEAF motor.

The 70D can go 250 miles at 65mph (EPA 240... with two motors / All-Wheel Drive), compared to a Model S-60 with the old motor at 208 EPA.

The battery price is "what it is". I know what all the goals are, and the last quasi-official cost for batteries that I'm aware of is $275 right now. Anywhere between $150 and $200 will be a HUGE improvement.

So, again, 45-50kWh usable, 50-55kWh advertised. At $150/kWh, that's still about $8000 for the battery cells alone.

EPA 200 miles. Optional EPA 250 miles, while the Model S/X are over 300 miles.

 

[evnow]

$35,000 at 20% margin leaves 28,000 for all costs. With an $11,000 battery, that leaves $17,000 for the entire car less battery. That is going to be very difficult, and that's WITHOUT Supercharger costs.

I think the base, base $35k car will not have 20% margin - but they'll sell very few of them. High margins come from upgrades - just like other car manufacturers. That gives them $24,000 for the car - which I think is fairly decent.

But I do think people who are expecting S like performance on the base 3 will be sorely disappointed.

 

[DaveinOlyWA]

with any car, there is likely to be various trim options. usually the lowest trim gets 5-15% of the market, medium 15-25%, high 35-50% then Deluxe 10-25%.

so basically medium (which can be as nice as a "high" with options) and high could be as much as 2/3rds of the market. So Musk is ok with trumpeting the cost of the "entry level" trim and I am ok with trumpeting what most people will buy and that is

about $42,879

Betcha I get closer than Elon

 

[NeilBlanchard]

The Model S has virtually the SAME CdA as the gen 3 Prius. Think about that for a second...

If that's the case, I agree that it is impressive. And I certainly hope that the Model 3 will have the same or lower Cd as the Model S, with a reduced A, due to the somewhat smaller size ("80%").

I do hope that they won't make it lower than the Model S. Besides the disadvantages in utility, when a car gets too low the risk is that it will slip under the bumper of a truck/SUV in a collision. A crumple zone doesn't do much good if that happens. And deer, the most common cause of collisions here, might come through the windshield, as happens with elk already. [Yes, local concerns!]

I don't make things up:

http://www.caranddriver.com/features/drag-queens-aerodynamics-compared-comparison-test

Low ground clearance is not necessarily better for drag. The air gets turbulent and pressurized, and so there is a sweet spot at about 6". This was figured out way back with the 1938 Schlörwagen:



Cd is ~0.18 and it seats seven people.

Another example of a very low drag car, from the same era:



And here is a (hopefully) very low drag car, that I have designed and am now building, called CarBEN:



CarBEN should seat five people, and with the right engineering, it would be safer than most cars (all else being equal) - because the driver sits in the center, and therefore has more structure to absorb the energy.

 

[evnow]

Neil, do you think any of the cars could ever get sold in volumes ?

No.

That is the point we are making - not that you can't design a weird mobile with low cd.

 

[DaveinOlyWA]

The Model S has virtually the SAME CdA as the gen 3 Prius. Think about that for a second...

If that's the case, I agree that it is impressive. And I certainly hope that the Model 3 will have the same or lower Cd as the Model S, with a reduced A, due to the somewhat smaller size ("80%").

I do hope that they won't make it lower than the Model S. Besides the disadvantages in utility, when a car gets too low the risk is that it will slip under the bumper of a truck/SUV in a collision. A crumple zone doesn't do much good if that happens. And deer, the most common cause of collisions here, might come through the windshield, as happens with elk already. [Yes, local concerns!]

I don't make things up:

http://www.caranddriver.com/features/drag-queens-aerodynamics-compared-comparison-test

Low ground clearance is not necessarily better for drag. The air gets turbulent and pressurized, and so there is a sweet spot at about 6". This was figured out way back with the 1938 Schlörwagen:



Cd is ~0.18 and it seats seven people.

Another example of a very low drag car, from the same era:



And here is a (hopefully) very low drag car, that I have designed and am now building, called CarBEN:



CarBEN should seat five people, and with the right engineering, it would be safer than most cars (all else being equal) - because the driver sits in the center, and therefore has more structure to absorb the energy.

cars would never pass crash tests. where is the crumple zone?

 

[minispeed]

cars would never pass crash tests. where is the crumple zone?

http://www.aerocivic.com/

Started with a stock car so it will still have the crumple zones. Yes it's possible that some of the add on's would change how it crash tests but I doubt it would cause it to fail. All the add on's could be done to a 2015 ie Fiesta, Mirage or even a leaf and achieve similar results so it could pass current crash standards. If it was done by someone with the same recourses as the OEM's it could even improve crash standards.

I won't try to argue that it's got mass appeal and that anyone would buy it but they did calculate the cd to be somewhere around a 0.17. Even if they made error's in testing it's still well below anything ever sold to the public.

 

[evnow]

I won't try to argue that it's got mass appeal and that anyone would buy it but ...

Then, why is this in this thread. It is OT.

 

[NeilBlanchard]

Neil, do you think any of the cars could ever get sold in volumes ?

No.

That is the point we are making - not that you can't design a weird mobile with low cd.

You are changing the question; which was that low Cd cars can have plenty of practical interior space, just like the Model S.

And low drag cars - EV's in particular, can be very safe. Like the Model S.

 

[GetOffYourGas]

with any car, there is likely to be various trim options. usually the lowest trim gets 5-15% of the market, medium 15-25%, high 35-50% then Deluxe 10-25%.

so basically medium (which can be as nice as a "high" with options) and high could be as much as 2/3rds of the market. So Musk is ok with trumpeting the cost of the "entry level" trim and I am ok with trumpeting what most people will buy and that is

about $42,879

Betcha I get closer than Elon

Frankly, I suspect you are both right. And I too am OK with Musk trumpeting the cost of the "entry level" trim. That's what gets people's attention. Then they look at the car, make the necessary additions, convince themselves that $8k is "worth it" for all of these extras, and viola - you have a sale!

Personally, I don't need all the bells and whistles. I tend to get bored with "features". What keeps me coming back to a car is how well it drives. And you cannot beat electric drive! So I would be one of those 5-15% happy with the low trim. The only option I need is supercharger access.

 

[evnow]

You are changing the question; which was that low Cd cars can have plenty of practical interior space, just like the Model S.

And low drag cars - EV's in particular, can be very safe. Like the Model S.

Not changing the question. Just making sure people understand this is a thread about Model 3 - not some esoteric garage experiment weird mobile discussion.

I'll reiterate - low cd compact cars (like Model 3) can't have very low cd and have good interior space (and not be a weirdmobile).

 

[dgpcolorado]

Personally, I don't need all the bells and whistles. I tend to get bored with "features". What keeps me coming back to a car is how well it drives. And you cannot beat electric drive! So I would be one of those 5-15% happy with the low trim. The only option I need is supercharger access.

I agree. Supercharger access is a must, since being able to make long trips, in addition to easy local/regional driving, is the whole point.

I'd also get AWD if it was less than $3k, but I presume that it will be part of a package or performance model that will be too expensive. If so, the base Model 3 plus Supercharger access would be enough for me, assuming that the EPA range is really over 200 miles, as seems very likely.

 

[GRA]

You are changing the question; which was that low Cd cars can have plenty of practical interior space, just like the Model S.

And low drag cars - EV's in particular, can be very safe. Like the Model S.

Not changing the question. Just making sure people understand this is a thread about Model 3 - not some esoteric garage experiment weird mobile discussion.

I'll reiterate - low cd compact cars (like Model 3) can't have very low cd and have good interior space (and not be a weirdmobile).

Indeed - they wind up looking like an Insight, EV1 or XL1, holding two people. Lower Cd, sure, but it's always going to be a tradeoff against interior space/utility versus outside dimensions, safety, reasonably 'normal' looks etc. The most easily achievable technical gain for lower Cd is through replacing the side mirrors with cameras, but that's a regulatory hurdle.