Mileage - Propane Injection?

[aseuffert]

I'm looking for anyone that has tried propane injection. We have Haulmark Garagehauler on a M2 Freightliner with a Cat C7. The power and milage is all over the place.

[Gordy]

When is the mileage the worst? The C7 isn't the biggest engine out there and you may just be overworking it, giving you the bad results.
For example, I got better fuel mileage pulling a heavy trailer with a 454 equipped dually crewcab then I do pulling a smaller trailer with my new 5.3L 2010 Silverado.
This is why I put a C15 in my Freightliner Century, that is soon getting converted to a motorhome.

[#90-GTSC]

What is the nomenclature? What is the differnce between a C7 and a C15? 7 liters vs 15 liters?

Thanks!

Dick

[Gordy]

The C7 is 7.2 liter or 441 cu in
The C15 is 15.2 liter or 928 cu in
My C15 is set to 475hp 1650 ft lb torque. A 300 hp C7 has max 860 ft lbs torque.
Notice that even though hp is up approx 50%, the torque is double. Torque takes you up the hill.
My Century Freightliner @55,000 lbs total weight pulls a 8.5% grade easily at 60mph and didn't overheat in the summer months.
Fuel mileage is around 8.5 to 9mpg on the highway which I find acceptable for this much engine. Some say mileage will go up with a few more miles on it but to date it has 27000.
May look at "chipping it" down the road.