I'm not sure if I'm the first hypermiling trucker or not. Between Mobile, AL and Louisville, KY there are lots of hills that are great for coasting. It's about 625 miles and I think I coasted about 40 miles total. Just guessing. I have a GPS(Streets and Trips) on my laptop so I was able to watch my speed, distance, and also the elevation. On 4 or 5 times I was able to coast over 3 miles and 4.5 miles one time. I never went over 75 mph (70 mph zone) which I don't like to do anyway plus to keep everyone safe. But I'd start at the top of the hill at 65 and reach 70 to 75. I'd leave the truck in 10th gear and depress the clutch and shut off the key. Once the motor was dead I'd turn the key on but not start it. Once I slowed to about 63 or 64 or I saw that the elevation was leveling off I'd ease out on the clutch for a rolling start and go on my merry way. It may have been more than 40 miles total. Possibly 60 or 70. I did it about 25-30 times for anywhere from 1 mile to 4.5 miles. Only bad thing is that with the truck off there is no power steering. I knew this before I started so the first time was just an experiment. As long as the truck is rolling there is no problem turning it. The truck has air brakes so this is not a problem. I only used the brakes to keep below 75 miles per hour. So the air never bled off. So there are no safety concerns. I'm able to safely control and stop the truck. As long as there is no major curve on the hill. You should definetly know your roads. Also the GPS shows what's coming ahead. And worse case if I did come to a curve I wasn't comfortable making I would ease out on the clutch and the truck would start right up.

Once I got to Louisville it was flat all the way to Milwaukee (stupid flat Indiana just kidding). I averaged about 62 miles per hour for the trip. The odometer showed 865 miles since my last fill-up in Hope Hull, AL. I put in 110.317 gallons in Sturtevant, WI giving me 7.84 mpg. My high for the past 2 months was 7.51 mpg and that was on flat land. My truck was Idling from 9 am till 5 pm in the 95 degree Indiana heat today. So I burned 9 gallons there sleeping. Which if it had been fall, winter, or spring I could have slept with my truck off saving me 9 gallons. I would have used only 101 gallons giving me 8.56 mpg for this tank. This is very exciting considering that the trucking average is about 5 mpg or less. Maybe even 3.5 to 4 mpg in the summer heat when trucks are idling all of the time to keep the drivers cool. Keep in mind that 1 mpg is $12,000 to $24,000 a year in savings depending on the miles driven. So a 4 mpg increase from 4 to 8 mpg could save as much as $96,000 for high mileage trucks ran by teams or husbands and wives. And up to $48,000 for someone like me. I'm parked in Sturtevant, WI with my truck off right now. It's 72 degrees. The trucks on either side of me are both running. A year ago mine would have probably been running too.

I hope no one is offended or frightened by my experiment. I would not do anything to put anyone else's life in danger or my life or career. Believe it or not I was still being passed my other trucks on almost every hill. I only apporached 75 miles per hour 3 or 4 times and would brake down to 73. Most of the time I was topped out at 72 or 73. The hills were not that steep. They would usually drop in elevation about 200-300 feet. From about 750 ft. elev. down to 500 ft. elev. for about 2 to 3 miles. The 4.5 miles coast started at about 800 feet and was a slow drop for 2 miles down to about 600 feet. Then it leveled off for about a 1/2 mile where I continued to coast. Then came another drop from say 600 ft elev. down to 400 ft. It was a really good feeling to go that far using only gravity. Keep in mind the truck and trailer are almost 80,000 lbs. Plus it's a tanker so the fluid goes to the front of the tank to help push. There was nothing steep or scary like in North Carolina or West Virginia. I definetly would NOT do it on roads that have run away truck ramps. Usually I'm riding my brakes all the way down to keep the truck at about 30 or 35 miles per hour. So the air would bleed off too quickly. Safety first. I've debated on sharing this wondering if I'd recieve more backlash than support. Let's see.

 

You described a Forced Auto Stop (FAS) technique that some posters (they will remain nameless) have reported on. One of these posters developed trouble with his vehicle and ended up with a $1200.00 repair bill with most of this being due to the dealership searching his vehicle for the problem(s). It would be great if the truck manufactures could/would design a hybrid feature into the vehicle. This is something you and your peers need to let the manufactures know. I doubt that FAS is legal in any state whether it is passenger car or "18" wheeler.

 

I don't see any problems as long as my speed matches the gear I'm in. I would not want to have it in a low gear and "pop the clutch" doing 70 mph. That would be very very bad. Like having a car in 1st gear and popping the clutch going down a hill doing 70.

 

Hi Brian,

I'm not a great fan of engine-off coasting if the vehicle isn't designed to handle it. It has to do with driver overload if something comes up ... not only the emergency but also restarting the engine. We are creatures of habit and adding one more, multi-step task detracts from our ability to handle the unexpected.

But let's do the math:

• idle burn ~1 gal/hr?
• 40 miles coasting @ ~70 miles per hour coasting -> ~35 minutes
• fuel savings :: .35 gallons? @$4.50/gal -> ~$1.57
• some loss of coolant temperature in radiator (may be insignificant)

I don't know what your engine does when gravity forces it to turn. Does the fuel consumption go higher than 1 gal/hr? I'm not even sure about the 1 gal/hr.

I think it would be much safer to just hold the clutch in, even if a little more fatiguing. You'll still have your power steering and full vehicle operations. But should something surprising happen, let out the clutch and you're there. This is one area where a power-assisted, clutch hold would be a help with something like a "deadman's switch" so if released, normal clutch operation would engage it again.

My thought is if you want to continue the ballistics downgrade experiments, consider some sort of simple device that would 'hold the clutch' on the descents. For example, a spring loaded latch that requires your accelerator foot to hold with a little force to hold the clutch down. If you take your accelerator foot off of the device, the clutch is automatically released. The key is releasing your "deadman's latch" engages the clutch right then and there.

At work we have electronic door latches consisting of a plate and powerful electro-magnet. Once engaged, the magnet holds the door quite firmly but once released, the door opens easily. A similar, electronic clutch holder would be ideal with a foot operated, push-to-close switch. The electro-magnet could be mounted on the clutch pedal assembly and use either the floorboard/firewall (carpet removed) or a metal plate firmly bolted to the floor. If integrated with your engine controls to "kill the diesel," other than power steering and air brake, you would have a semi-automated system that could be removed when the truck is sold.

A little more advanced would be to have an electric motor to drive the power steering pump. The racing shops have electric motors used to drive water pumps that may have enough power to drive the steering pump. In my Prius I have an electric assisted steering. The advantage of an electric motor driving the power steering pump is the pump no longer has to put up with the variable engine rpm load. Today, the pump has to 'dump' the excess energy. The key is making sure that if not moving, there is enough motor power to handle turning the wheels w/o being engine driven.

Understand that I have no problem with experimentation and learning lessons. But my approach has always been to use the lessons learned to inspire and optimize an automated solution. If this leads to an automated clutch/engine system, I'm with you. But I'm also well aware of driver fatigue and worse, folks not using your technique of using a GPS to predict the future road terrain.

Could I suggest another experimental approach that I've found helpful:

What I've done is plot the fuel consumption per unit of shaft power from data collected from my Prius. The negative numbers come from when the car automatically starts and stops the engine and some engine braking (i.e., negative engine torque.)

This chart shows the 'sweet spot' to be in the 1,500-1,750 rpm range with a nice band extending out to about 2,500 rpm. Anything over 3,000 rpm starts going downhill quickly, especially above 3,000 rpm to near redline, 4,500 rpm. This is different from the traditional "open throttle," specific fuel consumption charts because it comes from "in the field" vehicle operation.

Making a similar chart for your diesel would be a challenge but you might consider seeing if you can somehow record these values:

• engine rpm
• torque (very difficult if no sensor available)
• exhaust temperature (aka., waste heat)
• fuel consumption (aka., injector timing)

What I would do is get a sound input, USB module for multiple audio input channels. Then I would use AudioCity software to record the audio as data channels. Use resistors and/or isolation coils and/or cheap microphones to record the data and "record" your trip. Later, playback the data and plot "power/unit fuel" vs. exhaust temperature over the rpm range.

What you want is to find are "knees in the curve" where the engine is burning fuel less efficiently than at other times. The goal then is to keep the engine "in the sweet spot" for overall fuel efficiency. This is a kind of instant fuel economy meter mapped to engine rpm. Best of all, it is mapped to your specific vehicle.

Bob Wilson

ps. Do you pass through or near Huntsville/Decatur often?

pps. We are GreenHybrid and discussing non-hybrid techniques really belongs here.

 

Brian,

First it cool to see a trucker thinking along these lines. With you being an O/O I am sure the boss appreciates the attempts at fuel savings! :-P

Second...to me it's good to see you thinking of safety first because it doesn't matter how much gas you save if you or someone else gets injured/killed in the process.

As far as receiving flack over your experiment I'm sure you will get plenty of that mostly because a lot of people think that turning of the engine is unsafe. Personally I think you wouldn't see much of a difference between the engine being off or you coasting out of gear with it on. Then again I'm not an engineer like Bob or a rocket scientist like others.

I know in some pickups they have it where they only use half of the cylinders or something when the load on the vehicle is lighter. Do they utilize this technology in semis?

You joking cursed the flatlands but wouldn't you want more flatland than less? Yes you're coasting on the downside but are expending more energy overall on the upside and losing time? I know time is important to you guys.

Good luck.

 

Brian: I certainly applaud your efforts at truck hypermiling. The sharply increasing transportation costs are one of the key contributors for inflation this year. Everything, from produce, construction materials, consumer goods, you name it, has become more expensive.

I believe that eventually truck manufacturers will get it and start designing trucks with engine deactivation, some sort of hybrid engine assist (whether electric or hydraulic), APUs, electrically driven compressors and fans, improved cabin insulation, stremalining, etc, etc, etc.

Of course, all of those are technology enablers, there have to be educated and caring people like yourself to minimize fuel consumption.

Keep on trucking!

 

The truck uses about 1 gallon per hour when idling at 600 RPM's. Going down hill at 70 mph I'm running about 1700 RPM's. But there is no acceleration. I'm not sure how much fuel is used when the truck is in gear coasting at 1700 RPM's. Surely not as much as Running on flat land at 70 mph and 1700 RPM's. Now if I were to put the truck in Neutral and coast down the hll at 600 RPM that would equal the fuel consumption of just setting and idling. Downside to this I lose the ability to use the engine to brake should I need it. That's why I want an engine MPG monitor. I'd know how much fuel is used going down hill at 1700 Rpm's. I'm pretty sure it's close to the 1 gal/hr used during idling since there is no acceleration. Which would make it not worth the effort. But you have to give it a try.

Surprisingly, the coolant temperature increased. Another thing I didn't like it. That's way worse than cooling off. The truck can stay warm for over an hour after being shut off.

I rarely go up I-65. This was the first time in years. If you're in that area you must be familiar with the hills I'm talking about. I usually run in Texas and the Midwest and down to Florida and the Carolina's. Every once in a while up to New Jersey/New York and New England.

 

You definetly don't want to coast with the truck out of gear. They used to call that a "Georgia Over Drive". If you've heard that old truckin' song "Six Days on the Road" you've heard that used. I had the clutch engaged and left the truck in 10th gear so when I eased out on the clutch the truck would start right up. Like push starting a car.

There is nothing in semis yet that I know of that use less cylinders when the truck doesn't need it. Maybe in the next few years someone will come up with something like that.

And the flat lands are great. Just not for that experiment. I'd much rather run along at 62 or 63 MPH vs. down hill at 73 and up hill at 43 MPH. I'm sure if I drove from Kansas City to Denver at 62 I'd do just as well on my Fuel Mileage as I did on this trip. I would just be bored to tears. I have nothing against Kansas but it is flat with nothing to see for 100's of miles. If you ever get the chance to make that trip. DON'T!

 

Something is going to have to be done about the cost of fuel. What I'm doing is saving fuel and saving me money. But the fuel surcharge has already been charged. So any fuel I save the money goes to me. It cost's 6 times at much now to haul anything than it did 10 years ago. In 1998 where I live diesel was about 75 cents per gallon. Last night I paid $4.75 per gallon. A 100 gallon fill up that was $75 10 years ago is now $475. That extra $400 is not being paid by me, the trucking company I'm leased to, the shipper, or the consignee. It's all being passed on to the consumers. When was the last time you went to the grocery store and got a full shopping cart worth of groceries? Did you pass out when you saw the total? Way more than it was just 2 years ago. Even more than it was a year ago. My fiancee works as a Manager at Sterno. She was reading a report from a local warehouse that said they cannot keep Peanut butter and SPAM in stock because it's selling so fast. This is nation wide. People are having to decide between food or fuel. In the meantime some people are getting very rich. People here may get 50 or 60 MPG, but something still has to be done about the cost of fuel or the average person will not be able to afford to live.

 

I heard the major thing with FAS (shutting the engine off) you have to watch out for is that your transmission might overheat depending on how it is designed. Since you're driving a manual you should be fine, usually it is the automatics where the fluid pump is engine driven are the problems (basically if your owner's manual says you can tow with four on the ground you're safe for FAS). If your truck has the fuel cut feature then you're probably only saving the parasitic loss of your power steering pump by shutting off. A Scangauge should be able to tell you if you have fuel cut (if it works on semi's).

Are liquid haulers different? On one trip down to Houston I followed one going a flat 58mph while we were both being passed by normal semi's and even doubles. I got wonderful gas mileage because of him (don't worry I was almost 3 seconds behind him). He was driving a truck owned by the orangish company, dunno the name, maybe Schneider. The container looked like heavy duty plastic but not transparent enough to let me see the liquid sloshing inside (or he was hauling something clear). Don't remember seeing a diamond hazard thingie.