Increasing speed from 70 to 80 probably costs you ~25% of your range/efficiency

[ChasingCoral]

Tom Moloughney just released a second range test on the Cadillac Lyriq. Lots of folks wanted to know what the efficiency/range would be at their usual 80 mph speed rather than his range test speed of 70 mph. He decided to accommodate that request. The video dropped last night:




Here's the punchline in one graphic:

That's ~25% less range/efficiency at 80 mph than at 70 mph. As he repeats in the video, when driving an EV you can go fast or you can go far but you can't do both.

Now before you type "that's just the Lyriq" in all caps, I suggest the Mach E is probably similar. The Mach E has a Drag Coefficient (Cd) of 0.29. I can't find the Cd of the Lyriq but estimates put it between 0.25 and 0.3. I'd guess the two are pretty close. The Lyriq is about 1,000 pounds heavier but that is unlikely to make a big difference in this comparison. I doubt if RWD vs AWD makes much difference in the comparative efficiencies at these two speeds either.

So next time you're road tripping, this will hopefully inform you of the tradeoff in range and money when you choose between pushing BlueCruise to it's speed limit or keeping it down around 70.

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[HuntingPudel]

Since aerodynamic drag increases with the square of the increase in speed, the number of pounds of drag going from 70 to 80 is ~1.306 times higher at 80 than at 70. 30.6% more drag for 25% hit in fuel efficiency. ??

 

[Mach-Lee]

80^2/70^2 = 131% drag, so yes 25-30% more consumption makes perfect sense.

If you slow down from 80 MPH to 60 MPH it's 44% less drag, which is a huge saver if you're running low on range.

 

[yubbie2]

That’s a bummer for road tripping in TX where the between city speed limits are often 75

 

[AZBill]

His air density had to be lower than when he ran the previous test, by 4%. It does not matter what the Cd is, the equation is independent of that for a delta V.

 

[AZBill]

That’s a bummer for road tripping in TX where the between city speed limits are often 75

I drive 75 all the time in AZ and still get about 300 miles on the highway. Unless I am going uphill, such as to Sedona or Flagstaff.

 

[Mach1E]

Since aerodynamic drag increases with the square of the increase in speed, the number of pounds of drag going from 70 to 80 is ~1.306 times higher at 80 than at 70. 30.6% more drag for 25% hit in fuel efficiency. ??

Sounds right.

It’s not 1:1 math since air resistance isn’t the only thing that uses energy.

I wish it was! With a 25 mph tail wind I could drive 25 mph using no energy!

 

[Jimrpa]

Since aerodynamic drag increases with the square of the increase in speed, the number of pounds of drag going from 70 to 80 is ~1.306 times higher at 80 than at 70. 30.6% more drag for 25% hit in fuel efficiency. ??

So, you’re saying I’d I go fast enough, I won’t go anywhere? ???

 

[Blue highway]

hmmm maybe this is why I see so many people going 64 in the passing lane here in Oregon...

 

[HuntingPudel]

So, you’re saying I’d I go fast enough, I won’t go anywhere? ???

Your frunk button would certainly not be going anywhere! ??

 

[bp99]

hmmm maybe this is why I see so many people going 64 in the passing lane here in Oregon...

Those are the Subaru wagons angrily trying to pass the Prius going 50 in the right lane. They'll be back under 60 once they've passed (and will likely not move back to the right).

 

[GreaseMonkey]

I find 75 mph to be a nice compromise and (depending where you’re at) flows well with right / middle lane traffic. I would have jumped out of my skin driving this slowly in an ICE, but range optimization taught me patience.

 

[jeffvick2005]

Yes, In Utah we have 80 MPH for a good part of the interstate. I definitely noticed a massive hit in range driving 80-85...combined with the hills/mountains. The ford navigation did a poor job anticipating this when it recommended upcoming charging stations for my route.

 

[JohnnyForensic]

Y’all talking about 80 like it’s your daily commute, and in Virginia it’s an automatic reckless driving ticket. ?

 

[BMT1071]

Y’all talking about 80 like it’s your daily commute, and in Virginia it’s an automatic reckless driving ticket. ?

In AZ you get 20 over before they have the option of citing you for criminal speeding. They don't have to check that box, but they can. Don't ask how I know this. ??

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