Aerodynamics of electric vehicles ...

[OVERKILL]

the new Rivan Truck (almost HALF the drag of a similar-sized Dodge Ram) are just a couple more examples.

Do you happen to have a source for that? Only things I can find is some forum blabber, which I'm not going to bother posting, and this statement from elektrek.co:
https://electrek.co/2021/12/17/rivian-r1t-electrek-vehicle-of-the-year-2021/

The Rivian R1T isn’t just an electric pickup truck, it’s the future of the pickup truck. Rivian executives brag about its ultra-low .3 coefficient of drag that is more slippery than many sports cars and gives the vehicle an impressive 314-mile range.

The current DT RAM 1500 has a drag coefficient of 0.36 (0.357):
https://www.motor1.com/news/226890/2019-ram-1500-detroit-debut/

Another big area of improvement concerns aerodynamic performance, with the truck’s drag coefficient falling nine percent to 0.357. Big facilitators of that include the standard active grille shutters, a subtle “Venturi” design at the rear of the cab’s roof, higher bed side rails, and the fact that the 2019 Ram 1500 is about an inch lower than before.

So not far off from your Volvo XC40 example, but this is a full-sized truck.

 

[ZeeOSix]

Even if trucks have a "relatively low Cd", they typically still have a lot of frontal area - way more than a sports car. Aerodrag force is a funtion of Cd x A (drag coefficient times frontal area), and velocity squared.

 

[OVERKILL]

Even if trucks have a "relatively low Cd", they typically still have a lot of frontal area - way more than a sports car. Aerodrag force is a funtion of Cd x A (drag coefficient times frontal area), and velocity squared.

Yup, same with the larger SUV's that North America loves.

 

[1000MPH]

I’m a bit out of the loop on modern automobile aerodynamics, but when Model S Plaid came out, I was wondering if there was enough downforce in the design.
I seem to remember an anecdote about the Lamborghini Countach being a brick due to the wings and other aerodynamic devices required to keep it on the pavement.

 

[odie]

Seen that the 2022 Maverick / Escape hybrid have shutters , not sure of the regular ones .

 

[Jack Watts]

Do you happen to have a source for that? Only things I can find is some forum blabber, which I'm not going to bother posting, and this statement from elektrek.co:
https://electrek.co/2021/12/17/rivian-r1t-electrek-vehicle-of-the-year-2021/


The current DT RAM 1500 has a drag coefficient of 0.36 (0.357):
https://www.motor1.com/news/226890/2019-ram-1500-detroit-debut/

So not far off from your Volvo XC40 example, but this is a full-sized truck.

The RAM info was very estimated form an older video from a guy who did a pretty rudimentary CFD analysis on it:

Note that the drag numbers on that era RAM were so bad that the mfg never published them. I'm glad to see they've improved it (which I think all mfg's are doing these days).

Regarding the Rivan, my info is pretty 3rd hand--a friend of mind who's an aerodynamicist I've worked with in a different industry knows some of the guys working on the project. Actual numbers will be posted by the end of this year, evidently, and supposedly they will be even lower than suspected. We'll see...

Bigger point though is that aerodynamic in EV's is pretty key, and the eyeball windtunnel doesn't really tell all.

 

[OVERKILL]

The RAM info was very estimated form an older video from a guy who did a pretty rudimentary CFD analysis on it:

Note that the drag numbers on that era RAM were so bad that the mfg never published them. I'm glad to see they've improved it (which I think all mfg's are doing these days).

Regarding the Rivan, my info is pretty 3rd hand--a friend of mind who's an aerodynamicist I've worked with in a different industry knows some of the guys working on the project. Actual numbers will be posted by the end of this year, evidently, and supposedly they will be even lower than suspected. We'll see...

Bigger point though is that aerodynamic in EV's is pretty key, and the eyeball windtunnel doesn't really tell all.

Thanks. I do think it's interesting how close the current RAM 1500 and the Volvo example are, don't you?

I'm also interested to see some official Rivian numbers. Have you seen if BMW has posted anything on the i4 or iX? I know they claim it is far more aerodynamic than it looks, but I haven't seen any actual numbers presented in those claims, though I haven't done any deep digging either.

 

[Jake_J]

Due to the SUV or cross over nature of many vehicles on that list many of the drag coefficient numbers are not very impressive. For example the 2022 Ford Mustang Mach-E has a Cd of 0.30 and a generic 25 year old Mercedes E Class has a Cd of 0.29.

 

[Jack Watts]

Thanks. I do think it's interesting how close the current RAM 1500 and the Volvo example are, don't you?

I'm also interested to see some official Rivian numbers. Have you seen if BMW has posted anything on the i4 or iX? I know they claim it is far more aerodynamic than it looks, but I haven't seen any actual numbers presented in those claims, though I haven't done any deep digging either.

Interesting--but honestly, not surprising. The XC40 looks like a legacy product through and through to me, akin the the E-Golf ("hey, let's stick a motor and batteries in a gas car!"). That's the result... The new RAM is clearly designed with an eye towards aerodynamics. And of course, we're talking Cd vs CdA. Also, the newer RAM trucks do appear to be pretty sleek and eyeball windtunnel-approved!

The one thing I wonder is if they're publishing Cd w/a tonneau cover installed (do these come w/the vehicle as standard?). That is one sure way to lower drag on an open bed pickup truck (the other is to drive around w/the tailgate lowered, but probably not a great idea for other reasons...)

 

[meep]

Seems like it’s been verified that tailgate up is better than tailgate down. ”up” creates a rotating ball of air in the bed which acts like a cushion, preventing cavitation in front of the tailgate. In my truck, which has a full 6’ bed, I saw a very slight increase in my mpg once adding a camper shell.

dad had a crx, which scored at 0.29. My 2005 s60 had the same. Both had rather small cooling intakes. i loved that Volvo - i want to say my first s60 had a rather large fuel tank… somewhere around 18 gallons and over 30mpg hwy … 450+ miles to the tank was not unusual.

 

[Jack Watts]

Seems like it’s been verified that tailgate up is better than tailgate down. ”up” creates a rotating ball of air in the bed which acts like a cushion, preventing cavitation in front of the tailgate. In my truck, which has a full 6’ bed, I saw a very slight increase in my mpg once adding a camper shell.

dad had a crx, which scored at 0.29. My 2005 s60 had the same. Both had rather small cooling intakes. i loved that Volvo - i want to say my first s60 had a rather large fuel tank… somewhere around 18 gallons and over 30mpg hwy … 450+ miles to the tank was not unusual.

While it may depend a bit on the truck, I can't see how that's possible, since lowering the tailgate is going to encourage at least some laminar flow (unless the bed is impossibly short). Removing it entirely seems to hinder aerodynamics, but based on this research lowering it seems to help:

https://ecomodder.com/forum/showthr...racteristics-dodge-ram-pickup-truck-1228.html

Interesting thing about that kid's paper: does "new cap design" remind you anything???

 

[meep]

LoL. That’s funny.

yeah I think mythbusters did a decent episode including truck tailgates a while back. They tried hard with several different approaches. In the end, tailgate up was slightly more efficient. After a wind study, seems like they corroborated the study results with styrofoam peanuts in the bed, showing the same circulation…. Or I could be getting my wires crossed between different sources there. it’s been a while, fwiw, tire types make as big of a difference in my experience, as the bed/tailgate/camper shell differences seem to be 0.5 mpg either way from “stock.”

 

[vavavroom]

The Schlörwagen had a drag coefficient of 0.113 in 1939! That thing had a teardrop shape and must have looked insanely futuristic at its time. Not an electric vehicle, it got about 30 mpg.

https://en.wikipedia.org/wiki/Schlörwagen

 

[PandaBear]

The Schlörwagen had a drag coefficient of 0.113 in 1939! That thing had a teardrop shape and must have looked insanely futuristic at its time. Not an electric vehicle, it got about 30 mpg.

https://en.wikipedia.org/wiki/Schlörwagen

Bear in mind that while the lower the speed and the smaller the engine bring the better mpg, there is a tolerance on how slow you want to go and accelerate.

You probably can go 200mpg if you are going 15 mph on a 50cc engine that has 40% efficiency running 247. It will probably take you 5x as long to go somewhere you want to. Maybe ok for driverless trucking on UPS epic ground or USPS media mail, but not for most of the things we do in this civilization. I'd probably go back to sailboat before that (and that's infinite mpg as you never burn fuel and wind powered).

 

[Cujet]

The Schlörwagen had a drag coefficient of 0.113 in 1939! That thing had a teardrop shape and must have looked insanely futuristic at its time. Not an electric vehicle, it got about 30 mpg.

https://en.wikipedia.org/wiki/Schlörwagen

We learned a bit about these ultra sleek cars in Aero 101 at ERAU.

Subsequent testing of the design showed a higher Cd than initially claimed, roughly the same as the 0.19 of the VW XL-1. Sometimes, when things are too good to be true.... We must remember that some of the tricks to achieve such low wind tunnel numbers are impossible on a road driven vehicle (such as non rotating wheels). Also way back when, they did not account for the road velocity under the vehicle during testing.

Aero drag remains an important aspect of EV range, of that there is no question. However, we do reach a point where the work being performed, to accelerate and maintain speed with a 5000+ pound vehicle in varied conditions, requires a certain amount of power. Rain, snow, hills, pax/cargo loading, tire wear, HVAC, TOWING, and so on. We are going to need considerably more battery capacity to get something other than fair-weather improvements.

 

[ZeeOSix]

The Schlörwagen had a drag coefficient of 0.113 in 1939! That thing had a teardrop shape and must have looked insanely futuristic at its time. Not an electric vehicle, it got about 30 mpg.

https://en.wikipedia.org/wiki/Schlörwagen

Low Cd x A .... the reason why slip streamers go so fast with less HP on the salt flats.

 

[930.engineering]

.
Make that car longer along with a smooth underside (if it hasn't already) and it'll be even better.
.

 

[pezzy84]

Interesting--but honestly, not surprising. The XC40 looks like a legacy product through and through to me, akin the the E-Golf ("hey, let's stick a motor and batteries in a gas car!"). That's the result... The new RAM is clearly designed with an eye towards aerodynamics. And of course, we're talking Cd vs CdA. Also, the newer RAM trucks do appear to be pretty sleek and eyeball windtunnel-approved!

In defense of the E-Golf it was designed from the ground up to be ICE, PHEV and EV so its still a compromise but they didn't just stuff EV hardware into an ICE chassis. My E-Golf trades zero cargo space or usable interior space for the batteries - it lost its spare tire well and some room under the front seats but that is about it, the battery is packaged quite nicely without sacrificing any interior room.

Had to look at Golf vs E-Golf specs as the E-Golf wasn't in the above test. E-Golf is .28 so about mid-pack and VW literature shows it is 10% better than ICE Golf so that is about .31. Seems VW left quite a bit on the table for aero on the ICE Golf as most of the mods for the 10% improvement would be ok on the ICE, yeah maybe the underbody cladding would not be 100% due to accommodating a hot exhaust and the grill shutters might not be able to stay closed as long/often but the rest is really just aero treatment.

One thing I have noticed and wondered about my E-Golf is it has the vents for the front wheel air curtains but I cannot for the life of me figure out where it gathers the air as the LED bumper running lights are pretty much flush mount with no air openings. I haven't poked around but thinking there is something within the grill area where it gathers air.

 

[Kiwi_ME]

I lifted this graphic out of a very detailed analysis of the VW ID.3. The takeaway here is how important aerodynamics still are, especially compared with battery losses.

 

[JohnnyG]

1986 Merkur, Drag coefficient 0.26.