What if... the Aptera 2e had a EESU?

[NeilBlanchard]

Hi,

I found this image of the underside of the rear of the Nissan Leaf:

...so, I'll lower my estimate of the Cd of the Leaf to 0.26-0.27. And this meets the criteria of "one of the lowest drag production cars": the Mercedes is 0.24, the 3rd gen Prius is 0.25, and the new Insight is 0.28.

FYI, I have lowered the Cd of my own Scion xA from ~0.31 to ~0.27 by doing a large grill block (only a 15"x4" opening), removing the stock optical mirrors and installing two video mirrors, adding partial front wheel skirts, nearly full rear wheel skirts, adding Kamm "panels", and adding smooth wheel covers, and covering various edges and gaps with "zigzag" tape. I got the estimate of 0.27 by doing a coastdown test, using a video camera to record speed data and a spread sheet I got from here: http://www.instructables.com/id/Meas...t-of-your-car/ And here's my thread on all the mods I've done: http://ecomodder.com/forum/showthrea...mods-2969.html

Also, here's a very informative post about an interview with an aerodynamics engineer who works for BMW: http://ecomodder.com/forum/showthrea...aum-10481.html. He talks about the relative drag contributions of the parts of the car that are à propos to this thread.

[evho]

You folks all seem to have too much time on your hands....insert smiley face here.

[KarenRei]

I certainly wouldn't go as far as 0.26. We've got a planar vortex generator on the top and spike vortex generator on the bottom, as well as a reasonable-looking front. But this is having to compensate for having only 10-20% rear taper of a low enough slope to avoid flow separation. To get down to 0.26, you need a lot more rear taper before truncation. Either that, or some more radical measures, such as covering up the wheel wells.

In other words, if you could show me a single 0.26 or lower drag coeff car that has only 10-20% rear taper and no covered wheels, that *might* be different. Barring that, logic dictates going no lower than 0.28

[jstdadd]

In the great Gas/Hybrid/Electric mpg/mptank debate, Ford has quietly sneaked up on the world with the Fusion Hybrid - over 700 miles per tank of gas.
http://tinyurl.com/6fc6jp

Somebody in April drove one of the things over 1400 miles on one tank of gas as a hypermiling challenge. I am happy to see the world in general move to super-high-mileage gasoline powered vehicles as we enter into the fully EV Aptera early adopters. In 15 years, should Aptera still be around, they will have proven the EV concept, and maybe there will even be 1/2 as many EV charging stations as there currently are gas stations around the US.

[mmalc]

Originally Posted by jstdadd

In the great Gas/Hybrid/Electric mpg/mptank debate, Ford has quietly sneaked up on the world with the Fusion Hybrid - over 700 miles per tank of gas.
http://tinyurl.com/6fc6jp

Whilst I like my Fusion Hybrid a lot, the article confuses one extremely important point:

An ability to run on pure electric power for the first 47 miles.

This is wrong: the Fusion is able to drive up to 47MPH in all-electric. The maximum range in pure EV mode is usually given at around 2 miles. I've managed to get considerably further than that on (unsurprisingly) long slow downward slopes (such as from a winery at the top of a hill...).

Ford is, though, working hard both on its own EVs and on vehicle to grid technology.

[esmith]

Originally Posted by KarenRei

I certainly wouldn't go as far as 0.26. We've got a planar vortex generator on the top and spike vortex generator on the bottom, as well as a reasonable-looking front. But this is having to compensate for having only 10-20% rear taper of a low enough slope to avoid flow separation. To get down to 0.26, you need a lot more rear taper before truncation. Either that, or some more radical measures, such as covering up the wheel wells.

In other words, if you could show me a single 0.26 or lower drag coeff car that has only 10-20% rear taper and no covered wheels, that *might* be different. Barring that, logic dictates going no lower than 0.28

BMW E90 wagon has none of the features you mentioned, it's as plain-looking boxy wagon as it gets, and it is 0.27.

There is only *one* EPA cycle used for CAFE measurement of EVs and PHEVs.

First of all, there are no fewer than six different EPA cycles. CAFE standard does prescribe to use some specific cycles. But there's no evidence that any of the three companies (with the possible exception of Nissan) used the CAFE methodology. Volt used a new development version of SAE J1711, which has nothing to do with CAFE whatsoever. Second of all, you need to convert kwh into gallons of gasoline. Even within the constraints of CAFE standard, there are two different conversion factors, one for EVs, the other for PHEVs.

No, an ellipse has 78.5% of the area of its circumscribing rectangle.

I'm glad that you're still able to accept undeniable facts. I was losing hope.

calculations done by not me -- the total cross section of the 2e at TED was only 2,800 square inches.

All right, let's go with that! The TED prototype was 2,800 square inches, say 500 in2 of pods and 2300 in2 of the main body. Multiply the body by 1.21 to reflect production changes, and that gives us 3,300 square inches, on par with Leaf. Which proves my point.

Which, incidentally, means that the production vehicle will spend 80-100 wh/mile just to overcome aerodynamic drag at freeway speeds. Throw in some rolling resistance losses and auxiliary losses. I'd like to see how you're going to reconcile that with the 851 mpg claim.

It's really, really easy. There are three options here:

1) Aptera's executives are delusional
2) Aptera's executives are deliberately lying
3) The Leaf uses 2.3 times as much energy per mile.

It's not like they never lied to us before. But I wouldn't go as far as to accuse them of lying here. More like embellishing the facts. Maybe there is in fact an EPA test cycle (something city-like where the vehicle never goes above 30 mph) where 2e can average 100 wh/mile. And if they use the most optimistic conversion factor, 80+ kwh/gallon, they can claim 850 mpg. But there's no reason to think that the resulting number is in any way comparable with Leaf's 367.

[KarenRei]

Originally Posted by esmith

BMW E90 wagon has none of the features you mentioned, it's as plain-looking boxy wagon as it gets, and it is 0.27.

Yes it does:




Looks like a ~40% taper, and there's still lips to create vortices. Less space on the wheel wells, too, although the front isn't as good (hood is too long, and there are sharper curves at the windshield and A-pillars). But the rear and wheel wells look much better.

[esmith]

That's not a wagon. That's a sedan. Modded, at that. This is wagon:

[KarenRei]

I just searched for BMW E90; didn't know I needed to include the "wagon" keyword. By the way, where is your 0.27 number coming from? Searching, I keep coming across the number 0.30, although they're nonspecific as to whether it's the sedan or wagon.

Anyway, they both have a pretty similar rear, although the Leaf's is more stylized. Let's look at them side-by-side:


http://www.e90post.com/forums/attach...d=111739736 7

Quick observations:
* Again, the Leaf's front appears better.
* Again, the Leaf's wheel wells appears worse
* The two look to have similar taper

[esmith]

I just searched for BMW E90; didn't know I needed to include the "wagon" keyword.

E90 can either refer to the sedan specifically, or to the entire family (post-2006 3-series sedan=E90, wagon=E91, coupe=E92, and convertible=E93). I guess I could've been more explicit.

By the way, where is your 0.27 number coming from?

http://www.bmw.com/com/en/newvehicle...ical_data.html