[rank]

I was poking around under the hood of our "new" 2005 T2000, 475 hp, C15 Acert the other day. Decal on the engine said "625 hp max". I think all C-15's can be 625 if you want them to be. Just our the fuel to 'em.

[BanditsCousin]

Cattle haulers actually don't accelerate as fast as they can when loaded. If the cattle tumble on each other the can break necks and stuff, which they have to pay for. I will agree, they like to go a "little" fast, but that's because they wanna make sure there is enough breeze for them, almost to the point of air conditioning

My buddy has a 600 CAT in his W900. Pulling HHG, he can hang with "pig pen" and "rubber duck". His avg'd 5.2 according to the onboard KW computer screen.

[Jackrabbit379]

Sidman, I went to the website. I can just imagine what it would be like to have a motor like that. Man. :lol:
I didn't think the guy was full of beans, but I thought, "dag gum!"

Originally Posted by allan5oh

it is obvious that most cattle haulers do abuse the power, go as fast as they can, accelerate as fast as they can, etc...

Well, they do pin the ears back, I know that. You can't take off too fast. Not fast at all, in fact. You have to be easy in the turns, curves, etc.. If you take off real fast, youre gonna have to stop somewhere, and get the hotshot out to get your cows back up. Once you get going on the straight away, you can pretty much smash on it.

Cowhaulers get paid by the mile, (get paid lots) but they also have shrinkage. One reason why they do run down the road, is so they can get their cows off as soon as possable. (or atleast that's what I've always been told)

[allan5oh]

They certainly accelerate faster then I do.

[ironeagle_2006]

Allan big HP does not alwys mean BAD MPG regardless of what your computers tell you. I drove a 88 IH 9300 that had a 444 Cummions in her bossman rebuilt her to 720 TO THE GROUND. MPG BEFORE THE REBUILD WAS 4.5 after 6.3 why did it go up because I had the resevre NOT TO HAVE TO DROP IN THE HILLS AND NEED TO SCREAM UP AT HIGH RPM's. I could leave out of Streator IL heading to Fredoina NY and not have to get Fuel at all on the entire round trip of 1190 miles after the overhaul. Before I always had to stop for fuel in OH or PA on the return trip. If I got sent to Denver and I did ALOT I could make it there without a fuel stop running the speed limits. That truck went from the worse fuel hog to the best mileage in the fleet and we had everything form 60 series to fleet 315 cummins to 310 cats. The worse mileage trucks we had were the 315 cummins why called they could not get up the mountains we ran in. When you are dragging 45-47K up the rockies at 30 mph you are sucking the fuel down like a pig.

[allan5oh]

"reserve" isn't what gets you fuel mileage, regardless what Bruce Mallinson says.

I'm wondering exactly what was done to this engine, full rebuild? different turbo? free flow mufflers?

Like I said before, many modifications that increase horsepower may increase efficiency. But the efficiency increase is not from the higher horsepower at all. It's from a better flowing engine, and a more efficient one.

But simply turning up a 475 cat to 550 or more won't increase mpg. I have a friend who has a 475 acert, turned it up to 550, and noticed no difference at all. This guy has a fuel mileage log of the truck since new, down to the hundredth of a mpg. He keeps very close numbers, and I trust his numbers.

[tracer]

Originally Posted by Jackrabbit379

I can just imagine what it would be like to have a motor like that. Man. :lol:

Horsepower alone is not enough. The engine can be 500 hp but only 1650 torque, or it can be 500 hp 1850 torque. The best way to put a smile on the driver's face is to custom tune the engine performance through a Dyno. The difference in the truck "before" and "after" the procedure is amazing! It's not cheap but it's worth every cent. I just scheduled another Dyno for Monday. Dropping off my truck at 6 am (!) and it'll take them a whole day (!) to tweak/tune up/customize my C15 With 1850 torque, my CAT should develop 550 hp at 1600 rpm.

HP = RPM x Torque / 5252

[tracer]

Originally Posted by allan5oh

But simply turning up a 475 cat to 550 or more won't increase mpg.

My tweaked 475 hp 1650 torque engine did better for fuel mileage than non-customized 475 hp 1850 torque (after the rerate). You need to tune up the ECM fuel settings to get better mileage. But I do believe that if the truck is capable of "like-a-rocket' acceleration when bobtailing, it'll save money pulling heavy loads on hills compared to a bobtail that accelerates "so-so" from start. The main thing is to keep your right foot under control and use the high power not for speed but for conquering big hills. I personally never drive above 60 mph... Fleets buy underpowered trucks because 430 hp engines are cheaper than 550 hp engines, and they purchase so many trucks at once. If you have a fleet with 200 trucks and they can save 1,000 bucks on one truck, that's 200 grand. But it doesn't mean 430 hp is the way to go...

[TomB985]

Not that anyone cares , but I believe Allan5oh is correct.

From a physics standpoint, maintaining good fuel economy means having as little waste as possible. When you have to brake to maintain speed going down a hill, you are wasting fuel. If your truck hits the bottom of the hill at a significantly faster speed than your truck attacked the hill from, you are wasting fuel. It's a fundamental fact here that moving faster is less efficient due to increased wind resistance. Therefore, it can be said that if you achieved a higher speed, you put in more energy to get it that fast. The best MPGs possible would result from efficiently cresting a hill at a velocity slow enough that, at the bottom of the hill, you are doing your original speed you started from; this means you did NOT waste energy by braking, or excessive wind resistance through high speeds.

Imagine a scenario...you and a friend have the same truck, same load, same trailer. The only difference is motor...you have your 625 Cat, he has a "little" 435 Cat. He is forced to slow down climbing the hill, when you can power up the grade and maintain 65 MPH. He gets to the top at 45, and is immediately off the throttle. By the time he gets to the bottom, he's back to 65 again. You, on the other hand, crest the hill at 65, and your truck takes off from there, and you finish doing 80.

You both got the same truck over the same hill, and coasted down the other direction. You got there faster, but HE burned less fuel getting up the hill, thus returning better MPGs. Sure, he burned his a bit less efficiently due to downshifting, but wait...to get 625 out of your motor, you have to bring it up to 1700 RPMs...meaning you did no better. You came down the hill with much more energy...and that energy has to come from somewhere....

Conservation of energy. Burning fuel going up the hill is converting chemical energy to potential energy...accelerating down the hill due to gravity is converting that same potential energy into kinetic energy. Takes more energy to move the truck at 80 than 65, thus more energy was put in going up the hill....meaning less MPGs with the big motor.

Now, that same 625 motor can be just as efficient as the 435, as long as it's driven the same way. If you mirror the other driver's speed at the crest of the hill, your performance down the other side will be no different. Thus, you're going slower at the base, meaning less energy was present at the crest of the hill, meaning less was spent getting UP the hill.



Does anyone understand what I just said? Hrmm...think I just confused myself....:zzz:

[tracer]

Originally Posted by TomB985

to get 625 out of your motor, you have to bring it up to 1700 RPMs

Each time you shift from overdrive into a lower gear, you're using more fuel than the guy who stays in overdrive. The way I see it, if I stay in top gear going uphill somewhere in NC, WV or VA with 45k lbs in the box and I don't have to downshift because my Cat has 550 horses, I'm doing better than the guy with a 430 hp motor who HAS to drop 3 or 4 gears.

I keep the Cruise Control on most of the time, and if the hill is steep, the RPM will drop to 1100 RPM and the speed to below 50 MPH - and still the truck pulls without me having to downshift. Once I'm past the peak the truck accelerates back to my regular cruising speed of 59-60 mph. Who says I'm doing 80 going down?