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Does anyone have any information as to the FE improvement of drafting on the back corner of another vehicle or large truck.....as in a semi is in the middle lane and you are in the right lane with your front bumper behind their rear bumper.....like geese.

And drafting in this manner, where would be the optimal position for your vehicle in relation to the other vehicle? If a semi was in the middle lane, where would the drag be the least on your car?
a)with you towards the front of the semi
b)with you towards the middle of the semi
c)with you towards the end of the semi or
d)with you behind the rear bumper of the semi

I have been testing and trying different techniques, and over the past 3 months I have worked my way up to 41.5mpg with my' 05 corolla. With coasting on the hills and other strategic places I have cut off a little more than 10.6 miles off each way of my 56 mile round trip! Thats drifting over 1/3 of my total trip!! I dont know how this stacks up to others on this board, but I am all smiles and as excited as could be.

thanks,
jon

We don't recommend any of these positions because if the semi suddenly needs to change lanes and brake you are toast. Ever seen a car that went under a trailer?

Semis don't like this either because in some of the positions you describe they can't see you in their mirrors, which means they can't see you at all.

One gets a few moments of side draft as a semi eases by, but we don't recommend looking for more than that. Try slowing down and doing your own thing, and you will probably find that your mpg figures increase even more.

Try reading the info on Pulse & Glide. If it is possible to time your glides for your downhills you may do even better than you have been (which is excellent).

drafting can be dangerous, and in some cases trying to follow speeding trucks will counteract any advantage you may get from drafting. i live in Canada where the speed limit on the hwy is 100km/h and trucks routinely zoom past me at 120. i have yet to find a truck that is going slow enough (90-100) for me to tuck myself behind it.
nuf said :)

chuck, can you post that chart that shows the danger zones behind trucks?

Hello, Jon,

A lifting body, like a goose wing, creates a vortex at the end where the high pressure below leaks around the wing tip to the low pressure on top. The vortex from the goose just ahead is rotating the opposite of that for the goose just behind, and the cancellation helps the second goose. It actually helps the lead goose as well.

There are two corner fortices at the back of a truck. While these may be helpful, I think the effect is small, much less than the benefit of the truck's wake (forward air velocity).

Do you have a ScanGuage? That can help a lot in deciding how best to drive around other traffic. I see as much as a 10% mileage increase when I am 200 feet behind a truck. Trucks from the same company are often seen drafting on each other. There's a lot of money to be saved for them.

Drafting in the old meaning, tailgating, is a bad idea. But following a truck at a safe distance makes sense to me. I have noticed that when the highway is crowded with cars (usually going much faster than I am) that my mileage improves quite a lot from the influence of all that forward motion.

By the way, if there is a strong crosswind, then the downwind lane is a great place to be relative to a truck.

Ernie Rogers

Does anyone have any information as to the FE improvement of drafting on the back corner of another vehicle or large truck.....as in a semi is in the middle lane and you are in the right lane with your front bumper behind their rear bumper.....like geese.

And drafting in this manner, where would be the optimal position for your vehicle in relation to the other vehicle? If a semi was in the middle lane, where would the drag be the least on your car?
a)with you towards the front of the semi
b)with you towards the middle of the semi
c)with you towards the end of the semi or
d)with you behind the rear bumper of the semi

I have been testing and trying different techniques, and over the past 3 months I have worked my way up to 41.5mpg with my' 05 corolla. With coasting on the hills and other strategic places I have cut off a little more than 10.6 miles off each way of my 56 mile round trip! Thats drifting over 1/3 of my total trip!! I dont know how this stacks up to others on this board, but I am all smiles and as excited as could be.

thanks,
jon

With coasting on the hills and other strategic places I have cut off a little more than 10.6 miles off each way of my 56 mile round trip! Thats drifting over 1/3 of my total trip!!

This statement puzzles me. Could you explain what you mean by "cut off a little more than 10.6 miles"?

How do you figure that?

Speedo is not counting ... shows 10.6 less miles travelled on the counter.

ohh and another thing .... I believe geese fly to the right or left of the goose in front to avoid the crap ... they're always crapping as they fly ... perhaps hypermiling is just a bonus :)

If the ODO is not counting you probably aren't putting the key back in run position!!! :eek:

This is a safety issue -- please return the key to the run position after the engine has stopped running so that all electrical and safety systems are active -- and your ODO will still record distance.

If the ODO is not counting you probably aren't putting the key back in run position!!! :eek:

This is a safety issue -- please return the key to the run position after the engine has stopped running so that all electrical and safety systems are active -- and your ODO will still record distance.

THAT'S what I was afraid of. I read the original post and the little alarm in my head started to go off. Before you turn your engine off while in motion, if you have any question as to the proper safe proceedure, please search the site for more info or ask us for clarification.

BTW, when you start to count all your miles while hypermiling, your mpg will get a nice boost too.

Upanddown, From your description, I sense danger. Most trucks that pass me, have come from the right lane and wish to return to the right lane. As soon as they clear my car, I flash my lights to let them know it's okay to return to the desired lane. They seem to appreciate that, as most will pull in and flash their tail lights.

So, as traffic passes you in the middle or left lane, allow them to complete their pass. Don't speed up to maintain contact or benefit. You will actually benefit more as they pull in front, but for a short time as they pull away. And, all the while, don't exceed the speed limit in the Right lane.

Now, toss out everything I said if the passing traffic on your left is a train. They won't be wanting to pull back in front of you. Here, the worst that can happen is if your lane crosses the tracks up ahead, so be looking way down the road. If you happen to be driving parallel to an airport when a plane takes off, that's even better, the sky's the limit. (Someone please delete this last paragraph and make me shut up!)

Seriously, Jon, take the traffic side drafts as they come and go. It may be too dangerous, and perhaps unwanted by them, for you to hang time with the big kids.

A dash mounted airspeed indicator with its pitot tube mounted at the front of your car can be useful for finding the best following position (seek the position where you get the lowest indicated airspeed while driving at least 2 sec behind the preceeding vehicle). An airspeed indicator is also useful for detecting head and tailwinds (look for a difference between your speedometer reading and the indicated airspeed) so you can adjust your speed to compensate.

The trouble with pitot tubes, is that you can forget to remove the little sleeve covers prior to driving.

Thanks all for your responses and I very much appreciate the very apparent concern for my safety. I assure you that i do follow safe driving procedures and keep a keen eye on my surroundings (i dont go to work for myself, I work for my family and I dont want to do anything to take away from them). I am the type of person that wants to know the good with the bad as long as it is accurate information....ergo, I want to know the FE that would come from the different positions of drafting.

To explain my situation better, I travel I35 in fort worth, texas for my one way trip to work of 28.2 miles. There are very many good opportunities to pulse and glide for many of those highway miles. With using P&G methods in the far right lane, i can drift for many miles, as I stated at least 10.6 miles each way of gliding, with multiple spots of gliding for over 1 mile while not dropping below 50mph. I would keep track of the mileage of when I would turn the car off and the electronics back on, and when I turn the starter over to restart the car. Usually I drift for about .3-.6 miles on average and try not to drift unless I can get at least of .25 miles from drifting.

Being in the far right lane, I do get a lot of constant passing traffic on my left which creates a very good wind in the same direction of my travel. Thanks for all the good insight and knowledge, I look forward to getting better gas milage....but I honestly am very pleased with an average of over 41.5mpg for a tank of gas that carries 13 gallons.

Just wandering, how does this stack up to others on this board with non-hybrid vehicles?

It's all good. I'd send you to the Mileage Logs, but with the server changeover, plus some major organization and file movements, the Mileage Logs don't appear quite as they did before. I'm sure it's a ton of work, so I'm not saying anything about it.

But, when the logs are finalized, you will be able to (and we will be able to) see your average, and your individual tanks.

You can check out some of the Hybrids in the Mileage Logs (but remember those guys and gals are the pros - don't get disheartened). In the meantime, go to fueleconomy.gov and see how both other cars like yours, and the Hybrids are doing without Hypermiling. It's an eye opener.

The logs are in good shape right now. Any vehicles entered with no miles driven won't show up until at least one tank is entered (so the logged miles are more than zero), and the default is now to only show the top 50 vehicles (ranked by FE) in each propulsion section. You can change this layout by selecting 10,20,50,100, or All from the drop-down at the top right.

I had to restrict a default view of all the vehicles at once because with over 1600 vehicles the page load time was getting to be unacceptable. You can still choose to see all of them by selecting "All" from the drop-down menu.

You are doing well with your numbers -- keep up the good work!

say "big oil made me do it" when you're doing the police report for rear ending that tracker trailer...

Just wandering, how does this stack up to others on this board with non-hybrid vehicles?

As you can see from the logs (if you care to check), I started at 30 MPG last year. That's a bit over the combined EPA average for my car. I'm now working on getting a 45 MPG tank--I've gotten close twice so far, but the murderous heat last month wrecked that tank. (I "only" got 40 MPG on that one.)

After 45 MPG, I'm going to try for 50!! :)

There's a whole lot that can be done.

Oh, and let me reiterate two points that have already been made:
- Turn the key back to "run" when you FAS! Having the steering lock in one position if you have to turn the wheel for some reason is only one of many potential problems of leaving the key in the "off" position.
- Don't actively try to draft; just take advantage of the momentary FE boost you'll see when someone in the left lane blows by you at a high rate of speed. And if you find a truck that's going at your preferred speed, tuck in behind him at a nice safe following distance. You'll still find decent FE doing that, and you won't wind up eating a tire. Or other road debris, or a very angry trucker's fist...

-soD