Fuel efficiency

Re: 18 speed overkill....

The beauty of an 18 speed is that it gives you the same final reduction of .73 as most other transmissions while not sacrificing reduction on the lower gears. Ie. it reaches way lower than any other tranny.

So what that means is:

You can gear tall to get your cruzing RPM down while not giving up low speed grunt. Gears multiply torque, so the lower the gear, the more your engine's torque is multiplied. This lets a small motor act "big" and get heavy loads moving quickly. If you've ever been on a job site and gotten on really soft ground with a heavy load you understand that an 18 is not overkill.

 

Go with any 13litre block and a 10 speed.
Just make shure the engine you choose has torque.
Hp doesn't matter.(unless you want to brag about it)
Make shure that the gap between truck and trailer is as small as possible.
And offcourse go for an aero hood and cab.
Tyres are another point to look at.

And then there is speed.
It is very easy,the faster you go..............the more oil you burn.

 

Horsepower does, in fact, matter in hills. The downside is that high horsepower is harder on your drive train under acceleration. A 13 speed is better from a fuel mileage standpoint than a 10. If its geared to where you can run your chosen speed in 12th gear with acceptable rpms, even better.

 

If that is true, why did CAT, when they still made highway engines, advertise that their engines did in fact have:
"Hill flattening torque"?

 

In the hands of a bad driver.

 

When you're pulling heavy weights 12-13 speeds are essential and of course help the fuel economy because you can keep your engine in the economy band much easier

 

Just downloaded my ECM 4.5 years worth. Highlights or lowlights are,

5.23 mpg. By refueling numbers it's. 4.9 ish

Load factor 33%

Idle time 22% (guilty on this one)

Drive 65-70 all day

Daycab hauls 99000 lbs gross every load 550 cat, 18 speed, 3.73 rears and 11/24.5 tires on 6 axles.

Am I nuts to think these numbers are acceptable ?

 

It could be better, but it's not horrible. 3.73s aren't gonna get the best mileage. Could improve it a good bit with 99 rolling resistance tires, a fleet air filter, and one of those Pittsburg power straight through mufflers.

In any event, at that speed, weight, and gearing, it's not horrible. IMO.

 

How much big roads vs start/stop?

That will matter too

 

I'm pretty impressed with this W9. I've been running 6.1 mpg pulling 76k tanker loads. I run 70 and idle for every 10 I take. Got a cat c15 twin turbo, 500 hp, 3.36 rears. With all the mileage tweaks, I bet I could easily turn over 7. I am seriously considering buying this truck when they decide to replace it.

Especially now that I'm waiting at the kenworth dealership to get the catastrophic blown turbo replaced at least I'll know the turbo will be good to go!