Drafting behind bus on for fuel economy(video)

[PaleMelanesian]

I'm getting 70+ mpg these days, with no drafting. I would have to speed up to catch a draft, since they're going faster than I am, but why would I? It would cost me more fuel to do that.

We have to be careful about the message we're giving out. If we want others to drive more economically, our ideas have to be something they'll accept. If there's a single sticking point, they'll reject the whole batch.

Drafting, even with explanations about doing it safely and keeping following distance, is one of those points. People hear the word, and the picture they have is of parking inches behind big rigs. I actively recommend against it, for that reason. The listener will likely not hear the details after the single word, "drafting". I don't want to be responsible for them to misunderstand me.

[Chuck.]

Again, really good fuel economy is three things: (1) good car (mods help), (2) good technique, (3) ignore the speeders and ragers. Actually you can get pretty good fuel economy with a car that is not all that fuel efficient.

It's worth repeating again: the more you feel like you have to keep your speed with the pack, the harder hypermiling will be. Two reasons for that. The first is on a graph of wind resistance, it takes off above 45mph, so if you do much of your driving above 60, it's going to be hard to get good results. If you vary that throttle - good fuel economy is almost guaranteed to not happen. The other reason is allowing speeders and angry drivers to drive like them and fillup like them.

I live in the Dallas area. Drafting on a typical commute is overrated. To effectively get better results, the semi needs to be going steady in the 50-65 range - unlikely in a city like Dallas. Outside cities, there are more opportunities, but truckers have been alerted to drafting and they often defeat it by weaving, changing speed, etc.

If you are three or more car lengths from the big rig, then it's not the type of drafting that has been demonized in the media.

Take inventory of how you drive and it will improve.

[PaleMelanesian]

Originally Posted by Delta Flyer

If you are three or more car lengths from the big rig, then it's not the type of drafting that has been demonized in the media.

But it uses the same title. This leads to confusion and misinformation.

[Chuck.]

Andrew,

Sorry if I appeared to be passively endorsing the D-word.

Was attempting to say, make sure you are clear of a rig's "No-Zone" so everyone has a clear field of vision.

What I see (and experience) daily is aggressive drivers bolt from car to car tailgating and rabidly pass to tailgate the next car.

[PaleMelanesian]

No, no. I was merely highlighting what I consider a key point of your text.

[theunchosen]

I definitely will not say something if I think a reasonable person is likely to misinterpret it or misunderstand it.

Drafting as I said is not one of those things. Before I even say the word draft I always say "I stay more than 2 car lengths back always, but I like to draft. . ."

I also live in Tennessee and our truckers don't care. They do it to each other much more so than I do and if they see me come back there they will always signal far in advance of making a move. Likewise I always communicate with them when I can. If they put on a blinker and there is room in front of me I flip my lights to say its all clear.

My FE is 25% above my combined for my city driving(I only have short city hops during the week). My normal tank does 35, but if I am highwaying without a truck escort I still can punch 37. I'll be the first to tell you my transmission is geared too low.

Also drag doesn't really take off. Its a quadratic with no inflection points. Its a pretty big deal at 20 mph for a bicyclist. At 30 mph its a considerable force for a car.

One of the single most effective proposals to eliminate the need for high speed rail is to install on the HOV lane a magnetic strip. As soon as you want to insert your car into the lane click a switch the car closest to being behind you decelerates just enough to allow your car in. your car catches the line sends a radar pulse finds the car in front of it and tada, each car can draft inches away from the car in front of it safely.

Lets just imagine that except for the lead car this more than less eliminates drag( at out speeds its pretty close but at race speeds its not so close). It requires 9 horsepower to overcome drag at 60 mph. My max is 101 hp at 6400 rpm(?), I'm barely pushing the gas down at 3000 rpm, but even if we assume I'm WOT at 3000 I'm still using 1/2 fuel and producing roughly 1/2 the power. 50 hp-41hp/41 is a 21% improvement. I can assure you its not anywhere near WOT so its going to be alot more than that.

[Chuck.]

We all want to improve our fuel economy and encourage others to also do the same.

I'm talking about setting a good example to the public and avoiding bad PR.

Last summer, many were intentionally spreading myths to discredit hypermilers. It's copycat reporting, bad reporting, and even slander.

Check out this link - it's Google: "hypermilers drafting"

A year ago, there was a hypermiling event in Washington state. A Channel 5 reporter did a 90 second shoot of Wayne Gerdes - that part was fair, dispassionate. Afterwards, the reporter added another 90 seconds throwing Wayne under the bus...had a trooper who probably had just heard of the term making this sound like this is more dangerous than DUIs. That's just a worst case of reporting.

Brief tangent: a word for "stingy" is taboo...it sounds too much like the N-word...has nothing to do with a serious racial slur, but that's what people think so it's not used anymore. Drafting is another such casualty.

You may be safely behind someone and benefit from their lead, but I avoid the use of the term drafting as the propaganda implies it driving too close to see the traffic or to stop safely, even in this instance. Call it surfing or something else.

[theunchosen]

fine by me.

I surf car wake!

[donee]

Hi Unchosen...,

I think you need a Chirp CW radar for that application. A pulse radar would need to be expensive to have the range gates as small and as often as needed. I would avoid drafing without such an aid. But to be sure it works, you will need a test track and a willing lead car. The new Prius has an optional radar cruise control. Also, that 77 GHz stuff is kinda expensive in small quantities.

Hi Delta...,

I remember that. They showed a car drafting a big rig that was not even Wayne driving it. They used a sly technique to imply that it was Wayne. They were talking about the Insight, while the Saturn SL was there on the screen tail gating the semi. Wayne was in the area to demonstrate Insight techniques, and the short bit with him was in an Insight.

Hi All...,

In the Prius, it gets best mileage when its going along very stable-y at about 53 mph. When a Semi comes up next to it, the bow wave will drop the speed 1 mpg, which drops the mileage from about 72 to 65. Once you get back up to 53 mph, you can then feather back the throttle and have it lope along at 72 mpg again. The main problem is the sideways wind flow is like a cross wind. Which increase the aero drag. Along the side of the truck, the boundary layer of the truck is so low-energy, that its turblent, and screws up the Prius aerodynamics. And the Prius has such good aerodynamics it does not get much benefit from astern drafting at 65 mph (what trucks do around here in the 55 mph zones), that I just stay at 53 mph in the far right lane. If I see a truck coming up along side, I get way over to the right to avoid most of the bow wave and turbulent side air.

[Bicycle Bob]

Once upon a time, long, long ago, I was slogging through slush, stuck in slow traffic and low visibility, when I got spattered by a Greyhound with schedule on his mind. I jumped on behind and had a great run. There were just enough holes in the traffic for someone with a high seat to maintain speed. I probably saved gas, as well as time.