Yair...Our nomal open road speed limit here is one hundred kilometers an hour I came up behind an oldish Kenworth on the highway the other day and the sign on the back of the trailer said "I RUN AT 80 PLEASE PASS". Apparently the bloke has powered down and altered the gearing to get into the 'sweet spot' and the rig is undergoing fuel consumption trials. I also know of a fuel distributor that has gone from five hundred horsepower down to two fifty on their tankers. The standard eighty kilometer run is taking an average of seven minutes longer but is resulting in a "significant" fuel saving...apparently for a start there were some unexpected costs for tissues as the drivers were doing a bit of crying. It's all sweet now though and the replacement trucks have come through with the new spec. and every one is happy. Is this sort of thing happening in other places? I often wonder when I see todays trucks on the highway just how far we've progressed in the cost of moving freight. On the "Old Iron" board I have a post about how we used to regularly gross at around 170,000 pounds with less than two hundred and fifty horse power...the truck had 32 mph diffs and I venture to say that on the roads we ran a modern truck would be very little quicker. To take this to rediculous extremes...If you were to take that old Mack and new Mack with say identicle 170,000 pound loads and send them on their way over (say) five hundred kilometers of indifferent roads how would the fuel consumption compare? Any comments?
No comment.
A friend of mine and I were just discussing this yesterday. He has a Grove truckcrane with a 6-71 in the lower section, and I have a 1970 tandem dumptruck w/ a 6-71. He had just completed a 225 mile trip in the Grove, and we were talking about how little fuel he burned. I use that old truck for mostly on-site hauling now, but still drive it from site to site, frequently hauling equipment. I am constantly amazed how little fuel it burns. I haven't done this in about 10 years, but running it on short repetitive hauls in town, that old 6-71 will smoke a brand new 400 Mack from stoplight to stoplight. Now, out on long runs, there is no contest. 0-30 is quick, but 31-60, you better pack a lunch. I have sold all my Macks now, except 2, but I still have "my" truck, a 1994 CH w/ an EM7-300hp (Maxitorque). In later years all my others were 400-427hp. That 300 would smoke a 425 Cat climbing out of the bottom of the quarry, and is only a little slow getting up to speed on flat ground, but get out on the hills on I-26, not mountains, hills, and I'm climbing then at 30, while the other guys haven't downshifted. That 300 has a signifigant fuel economy advantage with a fairly light load, and/or flat ground, (with me driving, anyway), but in the hills, high speed, at 80,000lbs, the 427s did better.
Yair...grandpa's grumpy??
What kind of terrain are we discussing Scrub? Basically flat? Hilly terrain? Mountains?
Yair...willie. for the hypothetical with the old and new trucks I imagine dead dirt and wash boards. There would undulations and jump ups...some hills, definately no mountains. On the truck shown taking that nine aboard (on the "old iron" board) fourth high was the highest split and then you went to fifth. At 170,000 it didn't happen often. For the tankers I mentioned it is the run between two major cities, traffic all the way but not a lot of pulls. Hey Mitch. I'd heard the jimmys were of the road in most places in the 'States noise and pollution and all that sort of crap? We live close by the highway and even over here I havn't heard one for yonks.
Well Scrub, I'll just say it straight up. In the states, if you're driving local to your area, you could simply choose which HP truck suits your needs, maybe 200 HP, maybe 400. But if you travel the states, you might be in flat land in Kansas, and do just fine with 200 HP on a loaded rig. But if you're headed west through Kansas, in just a few hundred miles you're gonna (literally) hit the Rocky Mountains. If you're dragging 80,000 lb with a 200 HP engine, it's gonna take you a half hour to pull those grades, talk about burning fuel. As opposed to a 400-600 HP engine that can walk the dog and be over that grade in a matter of minutes. Question then, which one consumes more fuel, the rig that takes a half hour to pull the grade running full tilt, or one that can do it in 4 minutes? That's the choices the American trucker and trucking companies deal with.
Willie has it pretty much right on the money. Running around town or on flat lands, a lower horsepower truck makes sense. But, hit the hills or mountains, and the lower powered truck is going to struggle, hold up traffic, probably burn more fuel, cause more pollution, and eat up more resources to keep it repaired and running. But in flat land, I see no reason at all not to run a lower powered truck.
Total hijack here but what does Yair mean? Back on topic, I once drove a GMC Topkick tractor unit pulling a 20000 litre tank. This thing had a 3126 Cat in it with I think 250hp or so, with a 6 speed spicer behind it and no jake. Drove it from Pemberton to YVR empty and it was painfully slow. Got a full load of fuel and headed back. It was a very long trip back. Pretty much every hill I could find was first gear only, and on any incline the thing would slow down too fast to grab the next gear, especially with no jake or engine brake of any kind. There are some pretty long hills on that Sea to Sky Highway and they were all a 1st gear affair, and I was praying the whole way up that there would be no reason to stop with all the construction going on on the highway at the time. Luckily they only stopped me once going down a hill thankfully. I agree with alco in that the truck would have been great in the prairies or other flat areas but in the mountains this truck was downright dangerous! First gear down every hill as well and it would still take off, them brakes got a very good workout. And it actually overheated on me just as I finished climbing furry creek hill and the engine shut itself down. Now that was fun! I coasted into Britannia and let 'er cool off. Continued the journey the next day. It took 7 hours to get from YVR to Pemberton, a trip that normally took 3 hours give or take a few minutes...
spitzair, a truck like that is what ya call a dragonfly...drag up one side of a hill to fly down the other side.
Haha, that's awesome Willie, I'll have to remember that one
Hey, there are some pretty good grades through the flint hills. US50 can get pyros a bit uppidity.
Yair...okay. "Yair" is a habit, it means "yes" and some of us old bush blokes sort drawl it out before we begin to talk...some times it gives you time to have a think about what you're going to say before you put your tongue in gear. It does'nt seem to work too good on HEF judging by the way I upset folks over here!! Thanks for all the feedback on this topic. Are the high horse power rigs at a disadvantage fuel consumption wise when running on the flat? The opinion here seems to be that any horsepower used to move any given load at more than 80 kays is just wasted bucking wind...not so much of a problem now but with fuel bound to get expensive at some time in the not to far distant future it must be a consideration for the owner driver. Cheers
Welllllll, yes, but.... It's not significant on long steady, non-stop Interstate Highway runs, because the engine is only producing the hp needed to keep it moving. A lot of the large fleets here have cut the top speed of the trucks back, because, of course, the faster you move the load, the more energy needed. In local, stop-and-go work, it mostly depends on the driver. If he is taking off full throttle to keep up with traffic, that burns a LOT of fuel. Most private passenger vehicles here are pretty dang quick on the takeoff, and people use it. I have a Toyota 1-Ton pickup with a 4-cylinder gas engine, and it will not keep up with traffic, stoplight-to-stoplight, when I go to town. It's hard to teach most drivers that if you are only going 10 miles between stopsigns or turns, the difference in 55 and 70 mph is measured in seconds. I always find your comments interesting, and actually agree with some of them. You do tend to touch on subjects that are sore points with a lot of people over here though. Keep it up, it's interesting, Mitch
Yair...Thought I'd try it too You sure didn't upset me, I was just wondering what it meant... Personally I'm not so sure that the extra HP is going to burn that much more fuel if the driver doesn't use it. Yes I'm pretty sure it will burn a bit more but if the guy behind the wheel drives sensibly I'm sure it will positively affect his fuel mileage versus the guy who always puts the hammer down. After all, you're only using part of the ponies under the hood so you don't need as much fuel...
Yair...thanks fellers. Appreciate the comments. I upset folks over here too Mitch!
Or a rollscanardly, it rolls down one side and canardly make it up the other.
LoL!
Awesome
Grampa grumpy? Never! My gut feeling is that the higher horsepower truck, driven properly would be more economical in most situations, because the maximum torque can reached at much lower revs, therefore a higher gear can be used in the lower rev band and in my experience, higher revs equals higher fuel consumption. RnR.
As I understand it here in the states large fleets are cutting back for insurence cost savings as well as tax breaks. Overall per unit fuel consumption is reported to have gone down 2 to 3 cents per mile for large fleets. Does not sound like a lot until one considers that there are companies here with 20000 trucks on the road on any given day. I have to agree with Willie and others here that circumstances and conditions dictate horsepower needs and driver ability also is a major factor in fuel consumption. Personally both of my trucks are turned way up!! Reason one being because I can. Reason two is they are primarily used dragging oversize/overwieght equipment in mountainous terrain, over half the time on steep narrow logging roads. True, I am burning more fuel in this case but I never require another truck to snatch [helper] me over steep 2nd gear pulls in the woods so it seems like a wash to me. Both trucks average 5 MPG dragging 110,000lbs on flat freeway running 600+hp kitty cats with 18 speeds. Differance in fuel consumption compared to a 550hp Cat is negligable to say the least in my opinion. True, it can be argued that driver ability is a major factor as far as fuel consumption as well as increased maintenance and repair costs when running specs like mine. Fact is if I ran more units then the two I have now I would turn em all down.
Scrub , You surprised me with the way you approached this . I have to commend you for not Bashing The States as in the past posts. Now maybe a discussion can really take place . My son drove for a flatbed company for a year (Before he wised up ) TMC from Des Moines ,Iowa . The truck he drove had a 400+ hp engine in it but through company research the company found the best fleet fuel mileage was at 62.5 Miles an hour. So the trucks are governed at 62.5 mph. There are lots of trucking companies here that are using this approach not necessarily for saving the planet but more from a cost stand point. Several have been doing this for years. These I am speaking of are freight companies . Now to my personal opinion , Its my belief some of the resistance you have run head on into may be from a lack of knowledge about this industry . Please forgive me if that sounds like an attack , It's not meant to be . The truck I drive has the small engine of the fleet mostly due to the fact it weighs 34,000 bobtail, so weight had to be kept down and the small engine is how they chose to do it and still it's a 400 hp engine , barely. Company wise with the trucks, we will be expected to get off road at any moment . Heavy loads and soft ground eat up horsepower big time . Most of the time if you can keep a load moving you do pretty good but again that takes horsepower . Nothing really new about that . Most guys hauling heavy know exactly what I'm talking about . I also believe that RocksnRoses is right about the higher Horsepower engines in the hills will fuel mileage better . I come from the days when 240/250 diesel were big . The hills were always time and fuel killers , it was shift ,stand on it ....Repeat . lots of fuel left on those hills . I believe you can under power yourself into poor fuel mileage.
I've been searching the internet today looking for some studies of class 8 trucks concerning fuel economy related to engine horsepower and torque, haven't found anything interesting yet. I do recall several years ago, some of the big freight hauling companies went with lower HP engines and governed them about 58 mph, two that I can recall doing this was Schneider and J B Hunt. You'd be tooling along on a 70 mph interstate hwy and see one of those orange Schneider trailers a mile up ahead of you, go ahead and switch lanes because with him doing 58, you're gonna be on his bumper in no time. It seems that even these companies have bumped their speed up a bit because they no longer seem to be a slow moving vehicle hazard on the highways. I have no idea what has prompted them to do this, can only speculate, but I ponder if it has to do with data that they logged which showed trucks moving this slow caused them to use more fuel pulling grades as opposed to a good size HP and torque engine that could hit a hill, get it over with quickly, and leave it behind them. I just can't seem to find any research data that supports this anecdotal evidence.
All I can go by is what I have have run . The truck I drive now has been repowered . It started life with a cat 3126 engine .It was a 330 horse engine . It was a 170 to a 180 gal of fuel once week . 3 years ago the company replaced that engine with a c11 cat engine rated at 430 horsepower . Same 170 to 180 gallon but went to every 10 days to 2 weeks. That may not sound like a lot difference but over the long haul I believe it will help cover the cost of the swap . Also there was an added benefit , Remember my truck has an 11 ton boom on it . with the old engine I could pull the hoist lever with a heavy load and stall the motor so my standard practice was rev it up to 1,000 rpm . With the repower that problem went away
Back to one of the original premises in this thread. As previously stated, for an individual or trucking company driving local in the US, you're pretty much free to choose whatever best suits your needs. But the OTR contract hauling trucking industry is a totally different situation. OTR haulers and fleets are very much involved in pinching every mile they can out of a gallon of fuel since the cost of fuel is a major expense to operations. With that said, the industry and truck builders are always looking for any way to make the rig productive and at the same time efficient. But one method that will not work for OTR haulers here in the states would be powering down from a 400 - 500 HP engine to a 250 HP, no way, no how, the grades in the mountains here would kill fuel mileage. Instead, improvements in truck and engine designs are ever evolving. Back in the 70's fuel was relatively cheap. Trucks were boxy (remember Cabovers?) and not very aerodynamic. With the rise in fuel costs in the late 70's and early 80's, things began to change. If I recall, first out of the gate was Kenworth with the aerodynamic designed T-600. That started a trend that continues to this day. Nowdays, it's rare to see cabover on American highways, there's just no way you can make one aerodynamic enough compared to a aero conventional rig. With a CO, you're basically using an engine to push a sail "into" the wind. And there's no comparison to the efficiency difference between modern diesel engines compared to older engines. All these things, as Tiny stated earlier, are not being done to save the planet, or fear of limited oil reserves, but rather it is incumbent on them from a business standpoint to make the rig efficient with every drop of fuel. One of the latest trends I've seen is skirts under box van trailers to lessen the wind drag under the trailer behind the truck and to stream air by the trailer axles. Again, any little edge to making the rig more aerodynamic and therefore more efficient.
Yair...Interesting discussion. To sum up it seems that high a high HP (500+) rig conservativly driven is the best choice for a general purpose application. On the other hand, on any given run, there would be scope to come up with a spec. that best suits the route? Queensland conditions are MUCH different to those in the US. If you were interested you can look at google earth and see a goat track called the "Bruce Highway" that runs up the eastern seaboard. It is two lanes for the most part (that is one North one South) and is in pretty poor condition. Access to the mining areas is by sometimes even narrower roads that wind across our "Great Divide". If you get stuck behind a heavy load you'll be there for a while...the sharp curves and lack of momentum are probably more of a factor than the grade its self.
Yair...Tiny, them's were the days...when 240/250 HP was big. You must be getting up around my vintage. I posted a bit about one of my old rigs on the "Old Iron" page. Cheers.
Not a full fleged study by any means, but the lowboy truck I drive, back when it was new to us, had a significantly turned up 550 Cat 3406E. I don't know what it was turned up to, but it would pull 124,000 up a 5% grade at 55-60 MPH. Back then, it averaged 5.5 to 6.0 MPG with loads mostly in the 80 to 120K range A couple of years back, it had some engine problems, and had the fuel system worked over at the Cat house. It got returned to its factory 550 HP spec, and when I first drove it afterward (I only drove it occasionally then, as it had a full time driver) it was a DOG compared to before. The hills that were formerly 55-60 were now pulled at around 40 MPH. That was a huge dissapointment, but to add insult to injury, the fuel mileage loaded dropped to 4.5 to 5.0 range, with a best of 5.8 empty on long freeway runs at very conservative speeds, just trying to get the best mileage. To think that it used to pull overweight loads with a heavy foot and get better mileage than it will now empty with a light foot is disheartening to say the least.