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Drafting.. range effect
- Thread starter Steve3008
- Start date
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- Driving Dynamics Model S
Joe F
Disruption is hard.
Pray the trailer being drafted doesn't have a retread blowout. Happens quite often. TACC, AP, quick reflexes (you'll be too busy ducking when you hear the explosion) will not help at all...
That will be interesting. Might work in California and areas where trucks are at limited speed. Other areas, the trucks might not be going slow enough, but then, maybe you can get the same range, but at a higher speed.
You are properly set up -- others should be careful of trying this without the proper rig balancing and equipment to handle the erratic winds you will likely encounter.
KidDoc
Member
I drove from College Station to Dallas and back yesterday with a strong south wind about 20 mph. On the 75 MPH I 35 I drafted a big box rig between 65-80 mph and it made a HUGE difference. I was hitting 380-450 wh/mi prior and it dropped to 280-300 wh/mi. Made the stretch from Italy TX to College Station much less of a strain.
According to Wikipedia (and my personal experience is pretty much the same)
"On the show MythBusters, drafting behind an 18-wheeler truck was tested and results showed that traveling 100 feet (30 m) behind the truck increased overall mpg efficiency by 11%.Traveling 10 feet (3.0 m) behind the truck produced a 39% gain in efficiency. Additionally, on the same episode, Mythbusters demonstrated that it can be very dangerous for the following car if one of the truck's tires (or their recaps) delaminate, as the chunks of ejected rubber can be large enough to cause serious harm, even death, to a driver following too closely."
"On the show MythBusters, drafting behind an 18-wheeler truck was tested and results showed that traveling 100 feet (30 m) behind the truck increased overall mpg efficiency by 11%.Traveling 10 feet (3.0 m) behind the truck produced a 39% gain in efficiency. Additionally, on the same episode, Mythbusters demonstrated that it can be very dangerous for the following car if one of the truck's tires (or their recaps) delaminate, as the chunks of ejected rubber can be large enough to cause serious harm, even death, to a driver following too closely."
As the proud owner of a brand new $1050 replacement windshield, I'll be doing better planning and less drafting. Or even following at a distance. Or even driving on the same road as a truck! (honestly, I was not near a truck when the rock was hurled at me. It was a smallish one like countless others I have had, but hit right on the edge of the glass on the passenger side. Just bad luck. Or bad design? When did they stop putting a rubber or metal frame around the windshield? I guess for aerodynamics or wind noise abatement...)
That Mythbusters episode was flawed in many ways as far as drafting goes. I wouldn't take anything they concluded on there as being useful information for the most part. They needed to get someone familiar with drafting to do the actual tests. Drafting in a Tesla makes a huge difference, way more than 10%, even at 30 - 50 feet. Seeing as a Tesla has one of the best CDs of any production car, the amount of improvement on other cars should be correspondingly larger as well. So something was very wrong with the Mythbusters tests.
roblab
Active Member
??? I don't understand what you're trying to say here. First of all, who else has even done ANY testing, flawed or otherwise, on drafting? Second of all, their tests agree precisely with what you're saying: Drafting saves you over 10%. And thirdly, Mythbusters weren't testing Tesla drafting, so I don't see how that could be "very wrong".
It is probably good to note that drafting with a more aerodynamic vehicle would save less energy, but I can just charge up ten percent higher and get the same range, without driving under the back of some semi trailer. I don't need to draft. That's driving 150,000 miles in two Model Ses over 6 years. It's not like driving some gas car.
I've
Always wondered if they fudged the results to discourage the attempt. I get great results drafting. Like, 20%+.
If you will look at the post immediately above yours, I corrected myself. I misread the post when I wrote that. As far as being very wrong, I have drafted in a number of vehicles and my fuel mileage results (kept detailed logs in my 2003 Jetta for 240,000 miles worth) exceed anything that Mythbusters claimed at any distance, except the extremely close ones - I would never attempt to draft at 10 or 20 feet off a bumper for any length of time.
You can't charge past 100%, so you can't really charge an extra 10% to get the same range, unfortunately. It would be great if we could overcharge for emergency use or something, though. Drafting in a Tesla is typically for emergencies anyway - you use up too much power to get to your next charging stop (sudden rainstorm, lots of ice, snow, traffic jam earlier, etc...), so you must draft or get stranded on the side of the road. I've had that happen to me a couple times (mostly in the early days... now with 119,000 + 54,000 + 42,000 miles on my Teslas respectively, I don't have that issue anymore really, as I know exactly how far my cars can go on a zero charge. I'm sure that's going to bite me someday, but today is not that day!), and if I didn't draft the trucks, I would have been stranded in the mountains, at night, while it was raining. As it was, I rolled into the SC with 4 miles remaining that night.
roblab
Active Member
The advantage I see of drafting is that the drafter is being slowed down. Right there the range should go up without the danger of running into the butt-end of a truck in the rain at nights, snowing and uphill both ways.
I wonder how much extra range one gets from less air resistance behind the truck vs less resistance driving slower. Did Mythbusters compare that?Your post above mine popped up as I posted. And -- I have noticed that some people I know used to have quite a few miles after zero displayed range, and all of a sudden zero means zero and they get stuck needing to call a flatbed.
KidDoc
Member
The advantage I see of drafting is that the drafter is being slowed down. Right there the range should go up without the danger of running into the butt-end of a truck in the rain at nights, snowing and uphill both ways.
Your post above mine popped up as I posted. And -- I have noticed that some people I know used to have quite a few miles after zero displayed range, and all of a sudden zero means zero and they get stuck needing to call a flatbed.
From my limited data set driving into a head wind this weekend I was actually going FASTER drafting than pre-drafting. The semi's would run 75-82 MPH (75 mph speed limit). While I was not drafting I set the cruise to 75 mph and was getting 380-450 wh/mi and it dropped all the way down to 280-300 when drafting. The head wind was really chewing up battery when > 70 mph this weekend making my range drop in a scary fast fashion.
gavine
Petrol Head turned EV Enthusiast
I would think drafting would have even more affect on a Model X than a Model S due to the X being less aerodynamic.
I had an experience here where I got behind a semi at TACC distance 7 (while towing, so farther than usual), and saw a drop in consumption from my typical 550Wh/mi to about 470Wh/mi. So about a 15% potential benefit, realizing I'm not controlling for possible wind changes, etc.
KArnold
Active Member
I have another anecdotal story. This past Sunday I was driving from CT to OH - some 550 miles. According to ABRB I needed 3 super charging stops, the 2nd stop a scheduled 20-minute charge. Shortly after the first SC charge, a Tractor with one of those large air dams on the roof passed me doing about 80 MPH (70 MPH limit). He did not have a trailer. Traffic was light-to-medium. Set the cruise to #1 distance and fell in behind him for the next couple of hours.
Typically ABRB is pretty close for me. I did a refresh of it every 15-20 minutes, watching the scheduled charge time drop. It finally told me I could skip the 2nd SC altogether.
I wish I had better stats - I'm just saying in this scenario the energy savings was easily noticeable.
Typically ABRB is pretty close for me. I did a refresh of it every 15-20 minutes, watching the scheduled charge time drop. It finally told me I could skip the 2nd SC altogether.
I wish I had better stats - I'm just saying in this scenario the energy savings was easily noticeable.
Similar story, going north on 5 at 75 mph into a stiff headwind and got passed by a truck. Tucked in behind the truck and at 80 (TACC set to 7 distance and 85 MPH) was using 50-75 KWH less.
Fingers crossed that The Duke found a wormhole on I-5. That would open up some serious possibilities for family vacations.
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