1kw/m difference by changing driving style

[BourboNole]

The Rivian is basically a brick with bad aerodynamics which hurts efficiency badly. Seven times a year I take multiple 1,800+ mile round trips, when ever I can find a truck going 70-75 I draft them. Going up to 75 drafting trucks is the equivalent of going 60-65 solo for the most part. It definitely makes a huge difference for peak efficiency on long trips especially in the cost of charging overall. Its drives like that which make me miss my diesel truck with a 52 gallon tank and cruise set to 77, (diesel would cost roughly $400 round trip, Rivian came out to $280). Going to take my first one with the new EV in 2 weeks.... It will be interesting to see how something much more aerodynamic does with a 35KW smaller battery and the same range estimate.

The R1 actually has phenomenal aerodynamics. That doesn't make up for the fact it has a large frontal area, but its Cd is well below most other similar vehicle.

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[SadHill]

The R1 actually has phenomenal aerodynamics. That doesn't make up for the fact it has a large frontal area, but its Cd is well below most other similar vehicle.

Yes. The CD is 0.3 which for a pickup is low.
https://insideevs.com/news/611642/rivian-r1t-aerodynamics-drag-coefficient-simulatiion/

 

[LMI - R1T]

Drafting definitely worked for me. I wasn't going downhill but was going rather slow. I wonder what the mi/kwh would have been up to if it didn't max out at 4.

 

[rhumbliner]

So if I don't think the person in front of me can see either, I slow WAY down, use flashers, and take 100% responsibility for making sure I can see what I'm doing. Or just get off the road completely, including the shoulder.

I guess I should have qualified that by saying when in heavy fog I will follow a semi. Then I’m putting my trust in a professional driver who is sitting up a lot higher (with maybe better visibility) and I’m assuming I can stop a lot quicker than the semi. And, oh yes, flashers on. ?

 

[usulio]

Just some extremely rough numbers regarding wind to show how big a difference it makes. Let's say you're going 70mph. With a steady 12mph headwind, that's aerodynamically like going 82. When you turn around, it's like going 58. That is a 1.4x difference which means the drag is literally twice as high in one direction as the other. Given that drag is the main use of power at highway speeds, that's a massive difference, and 12mph is not even that high of a sustained wind speed.

 

[mudito]

Just some extremely rough numbers regarding wind to show how big a difference it makes. Let's say you're going 70mph. With a steady 12mph headwind, that's aerodynamically like going 82. When you turn around, it's like going 58. That is a 1.4x difference which means the drag is literally twice as high in one direction as the other. Given that drag is the main use of power at highway speeds, that's a massive difference, and 12mph is not even that high of a sustained wind speed.

... And it's a quadratic mathematic function so it's exponentially lower on the way back.

 

[usulio]

... And it's a quadratic mathematic function so it's exponentially lower on the way back.

Right, what I meant was that 82 = 58 * 1.4, so the difference between the way out and the way back is 1.4 squared = 2, so twice as much drag on the way back as the way out.

 

[Keith Stevenson]

I am sure there are plenty of people who know this. I have been doing this for some time but I never really spoke about it before.
Today I went for a 240 mile drive (120 each way) to pick up some things. It was 95% highway, 65mph limit, upstate NY so not flat but no mountains.
The way there I did 73, had the heat set at 66 and it was 35 outside. There was a headwind of about 10-20 with 30 mph gusts. When I arrived my efficiency was 2.01.
On the way home I set cruise at 70, turned off the heat (still was 35 outside) and found a tractor trailer driving 70 and parked behind them. I had driver plus on and when he sped up going down hills i would speed up and then obviously would slow down going up hills. I stayed about 2 car lengths behind. I also had that tailwind (which does help a lot). When I got home i was pleasantly surprised to see my efficiency was 3.06. That is a huge difference. I have drafted trucks in the past but it is tough to find one not going too slow. 70 was a good speed and I was behind them almost the whole way.
Just a bit of info in case you wanted it. Drafting works amazing. Not sure if turning off the heat did a lot but it didn't hurt.
Thanks!

I drafted a semi once while crossing Nebraska in the Winter in an ICE vehicle. It was the only way my vehicle would warm up. And the mpg went up accordingly to what you experienced. Almost a free ride.

 

[HyperionMark]

30 mph headwind on a -10 degree day. Drafting can literally double your efficiency. All you southern boys don't need to learn stuff like this.

 

[dleepnw]

lots of variables between there and back. hard to say which had the most impact. you'd need to do it again multiple times with one changed variable to really assess that. what does seem clear is the combination of changes had a big effect.

you should also look at battery temps each way. with it being cold outside, if the battery was a lot warmer on the way back, your efficiency will be better.

 

[ElGuano]

Not sure if you mentioned it, but was there any net elevation change there and back? If you end up doing that drive again, try hypermiling techniques on the way out, and driving normally on the way back, and see if the data holds!

 

[SadHill]

Not sure if you mentioned it, but was there any net elevation change there and back? If you end up doing that drive again, try hypermiling techniques on the way out, and driving normally on the way back, and see if the data holds!

Let’s see

batteries were about the same temp there and back. I have a heated garage so they were in their mid 40’s.
as far as elevation change. Again, about the same. Maybe the way there had an extra 100’ but that would be the extent of it.
def going to do it multiple times. Next trip will be next week when we go skiing which is 120 miles away. Although it will def be a difference in elevation on the way back so tough to judge that one.

 

[Woo]

... a new drum set for my son for Xmas.

Very cool. What was it?

 

[SadHill]

Very cool. What was it?

Got him a Tama Superstar Maple set. 9 piece and tons of extras for a great deal. It is like new shape so he will be psyched!!
Took our kids to a Green Day concert last summer and now he is so into punk and heavy rock. It is awesome

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