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Old 12-04-2011, 04:22 PM   #1
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Default Mileage - Propane Injection?

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.

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Old 12-04-2011, 09:44 PM   #2
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Location: Grand Forks BC Canada
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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.

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Old 12-05-2011, 07:42 PM   #3
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What is the nomenclature? What is the differnce between a C7 and a C15? 7 liters vs 15 liters?


Started looking for 379 Peterbilt TC, 24' to 30' box, bumper pull--but ended up w/1999 Liberty Coach conversion of 45' Prevost XLV bus. 1,000sf heated/AC'd race shop w/dump station, 50amp shore pwr where bus parks, 3 NASCAR/ARCA race cars & 26' Bravo trailer.
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Old 12-06-2011, 12:12 AM   #4
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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.
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