Detroit DD13 or DD15

Legal 80k and under isn't what I call heavy. Even running 78-80k a 12L or 13L engine is plenty enough.

 

That being said I'd take the 505 1850 dd13 over the less powerful dd15.

I don't have much to say about the 15s they were all gutless 2.64 direct drive. Makes this old mack feel like a race car

 

The emissions system is the limiting factor.
You want more then 505hp then you need something without SCR. Well, if factory warranty is important anyway.

 

Of course, I'm just saying consistently running big weights on big hills you might see better fuel economy with the bigger motor.

I run 95,000 gross down the 17 in Ontario (up to 7% grades) with a 470hp C-13 and she gets up them just fine, but a 550-600hp C-15 would probably do it better.

 

Yea I hear you. The old ch is a 350 from The factory with 3.91s but she has some fuel put to her prob putting 460-475 out and not really any fleet spec trucks out pull it

 

When I made the specifications for my truck I talked to the engineers at Detroit and Cummins as well. The smaller engines are recommended for LTL, local and regional works. If you ramp up the horsepower and use on highway with 80,000lbs, it will use more fuel and will have shorter life span than the 15 liter. Choose the engine what designed to your work.

 

Don't forget the common sense and remember that climbing steep hills is a very small part of most use. If you drive 10 miles of steep grade climbs ( say over 13% grades to be considered steep) pulling heavy loads ( to me heavy loads are when gross is over 140,000 pounds) on a trip length of 1,000 miles, you still only had to pull a steep hill 1% of the time, so a very insignificant portion of it. And then just pick a gear it will and hold your foot to the floor, the trucks engine will not care, diesels are meant to be worked. If you have over heating issues or something, then fix the problem, and just drive the truck, and worry less . I find it bizarre that people assume they should just be able to climb all hills at the speed limit or close to it. Let the engine work, it was built to do so, and they hate idling or not working hard enough. Maybe part of the reason I never have engine problems is because mine actually get worked, and not just idling around all day.

 

@Oram

Had to be a bs selling point. Just look at the S60 12.7 history. Millions of miles otr on that platform but now Dd says you need a 15l motor.

Nope!! 13 can do it just the same.

 

We can start to bash the new emission stuff, but that is new challenge. The old engine couldn't handle and they increased to 14 liter what was mule junk. I had one of those 12.7 legend and praise it day and night. But those days not coming back ever. You can try to put a temporary pause with a glider if your jurisdiction let enough loophole to have one, other way you have to look forward. The engine makers do not build the bigger engine just to fool you and sell more iron. To produce the same horsepower in smaller engine means more pressure on the internal parts, that is why the extended warranty price is different based on the horsepower. Obviously there is a sweet spot and the engineers try to find the balance and not a bunch of idiots..... Unless if you still believe the Earth is flat.

 

Just look at the other engine manufacturers.

Paccar MX13 biggest displacement available.
Volvo discontinued the D16 so now the 2 options are D13 and even the D11.

Must be a different engineering philosophy.