At highway speeds, most of the energy is used for overcoming air resistance. Does anyone have experience in how much the range changes when drafting another car, or in heavy traffic where everyone is drafting? You could easily do this by just enabling adaptive cruise control with a following distance of 1 car length, and following another car.
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range when drafting?
- Thread starter cstork
- Start date
eye.surgeon
Active Member
Don't draft. The interstate isn't a Nascar race. It's not safe, it promotes road rage, it's brutal to the paint on the front of your car, and the amount you save is literally pocket change.
israndy
Supercharger Hunter
What a great car to draft in, if you are not paying attention, the car is. And from all the mentions in other threads, it seems everyone puts a film on the front to protect it from debris.
I have been drafting as my version of hypermiling for decades in my 2000 Honda Insight. It's really my cruise control as the car doesn't come with any. I get that is must be annoying for the truck to have me on their tail, but I have never had an issue where the truck stopped fast and I was in danger. Those things are huge and my Honda is less than a ton.
-Randy
I have been drafting as my version of hypermiling for decades in my 2000 Honda Insight. It's really my cruise control as the car doesn't come with any. I get that is must be annoying for the truck to have me on their tail, but I have never had an issue where the truck stopped fast and I was in danger. Those things are huge and my Honda is less than a ton.
-Randy
The Cd is low and the car is very efficient. it wound not make much (if even noticeable at all) of a range difference at <70 mph. If you are worried about range going 55-60 mph would be much more of a “range saver”.
And yes that slight gain would be at the cost of your entire front facing paint, windshield, and possibly glass roof. And as per the comment PPF isn’t a “save all”. You still need to have some sense about things.
And yes that slight gain would be at the cost of your entire front facing paint, windshield, and possibly glass roof. And as per the comment PPF isn’t a “save all”. You still need to have some sense about things.
Wooloomooloo
Member
I completely agree.
But...
On a recent very long road trip, I did once sit behind a truck with EAP on for about 110 miles to see if I got any benefits. I set to follow at six car-lengths, which for a human is far too close, but for the Tesla it seems OK (unless the truck hits something very solid) and probably close enough to get some partial drafting given the size of the truck.
Anyway, the difference between 70mph with nothing in front Vs that truck might ( driving 65 - 74mph depending on inclines) was about 320 wHr/mi for the former and 275 wHr/mi for the latter. This was during a cold dark evening with light rain. That's a pretty significant range improvement (40 miles or so).
How much of that was due to drafting and how much was due to varying speed based on incline, I couldn't tell you.
I thought I was seeing some OK drafting results following at setting 7, then I realized I was going as slow as a truck. Since speed is a huge factor in consumption, I figured that was probably as much a factor as anything. In other words, not worth it.
I would guess that if there was a strong headwind, it might make enough difference to matter.
I would guess that if there was a strong headwind, it might make enough difference to matter.
israndy
Supercharger Hunter
I believe my Honda Insight has a CDi that is bested ONLY by the Model 3. I was able to take my 10-gallon tank and draft almost 400 miles down to LA and a TINY bit of city driving AND back to SF. So my normally 58 MPG car was getting ~93 MPG on those trips.
Yes, you are going a slower and consistent speed, so it's not ALL the truck pushing the air aside, but that's a lot of it. You really don't get the efficiency until you get past the buffeting zone, you feel the car smooth out as you get super close to the back end of the truck. I don't think the Tesla can be set to follow as close as that.
Mythbusters: drafting 10 feet behind a big rig will improve mileage 39 percent
-Randy
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I routinely draft on the highway and agree that drafting can stretch mileage and even allow you to drive faster. Note I never draft one vehicle more than 10 miles and will leave a semi doing the limit if a big suv passes You get enough of a draft to allow you to drive faster with no increase in normal mileage. Also, driving on a busy highway is the equivalent of drafting a suv. Of course if there is a strong tailwind, drafting is meaningless.
I did the (rough) math a while ago on a different thread. From what I remember up to 55 mph the force of drag was very minimal Since the force of drag is a function of velocity^2, Velocity is the largest factor. In perfect conditions in a wind tunnel follow at 100’ drag is reduced by 40% that is with no wind, no cross flow. Just head on air. So just for argument sake in a perfect environment your savings: 55 mph 24 Wh/mi, 65 mph 34wh/mi, 75 mph 46 Wh/mi. So real world traveling 60 mph up to 10% More efficient?
Now here is the kicker. Not drafting the savings between 55mph and 75 mph is 22 Wh/mi so almost as much as drafting (under theoretical perfect conditions) saves at 55 mph. So if your worried about range, slow down. Now if you were willing to travel 2’ from the trucks bumper you could double those Wh/mi saved.
Now here is the kicker. Not drafting the savings between 55mph and 75 mph is 22 Wh/mi so almost as much as drafting (under theoretical perfect conditions) saves at 55 mph. So if your worried about range, slow down. Now if you were willing to travel 2’ from the trucks bumper you could double those Wh/mi saved.
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You wouldn't sound like such a jerk if we weren't comparing chump change and people's lives.
I have drafted before in situations where I need to get a little extra range to avoid a supercharger stop. My rule of thumb is to set following distance to 2 cars, which in reality is more like 3 or 4 at highway speeds. I get that following semis has an increased risk of debris but I don't think I'm following the trucks any closer than average drivers, the difference is that I'm following them for a longer period of time. The ability to gain 10-20 miles of range is sometimes worth it for me.
My experience with my S85:
On 2.5 hr legs with AP engaged, fairly level ground
At 70-80 mph
I see increase my SuC arrival percentage by 10% on the nav.
That is about 25 miles gained
Wh/mi drops to 287
The biggest hazards are road debris, including tire rubber retreads coming off of 18 wheelers at high speed, or other objects that just appear out from under the truck.
Be safe out there!
On 2.5 hr legs with AP engaged, fairly level ground
At 70-80 mph
I see increase my SuC arrival percentage by 10% on the nav.
That is about 25 miles gained
Wh/mi drops to 287
The biggest hazards are road debris, including tire rubber retreads coming off of 18 wheelers at high speed, or other objects that just appear out from under the truck.
Be safe out there!
omgwtfbyobbq
Active Member
What lives are endangered by a < 2000lb Honda Insight driving behind a tractor trailer?
omgwtfbyobbq
Active Member
From personal experience, enabling EAP with a 2-3 car following distance tends to reduce energy consumption by 10-20% or so compared to driving the same speed while staying away from traffic.
On a road trip in November through North Dakota & Canadian prairies (no superchargers anywhere) drafting was essential to getting anywhere without driving too slowly. When I followed a semi at distance 2, energy usage dropped from ~350Wh/mi to ~275Wh/mi AND my speed increased from 55mph to 70mph or whatever speed limit the semi was going.
At follow distance 1 some trucks weaved to get me off their tail, but at 2 it was fine.
[Edit: mi / km]
At follow distance 1 some trucks weaved to get me off their tail, but at 2 it was fine.
[Edit: mi / km]
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