[rank]

Originally Posted by TomB985

Wow...that efficient at 1700 RPMs...

Imagine if I could drive 55!

We heathen company drivers don't have much choice of equipment, and thus I drive what I'm given. The only two engines I've ever had for any length of time were 14L Series 60s, and this Cat C15...both of which like 12-1400 RPMs.

uh-huh. we have them too and that's where they live.

It's amazing the figures you guys are getting with smaller motors, you have to wonder why many fleets prefer the large ones.

This is pure speculation on my part, but I wonder if a low speed limiter setting will mean you need a bigger moder because you can't get a run at the hills.

[rank]

Originally Posted by tracer

Large engines last longer.....

I wonder if there is any stats on this. That lil' M11 has 925,000 miles on it.

[rank]

Originally Posted by rank

that M11 that I drive? I used to drive it 70, then 65, now 60. Mileage got better every time. Even at 60, it screams 1700 rpm with that 4.55 rear gear and 22.5 LP tires. I can't drive slower than 60 so I think I'm going to swap some tall rubber on there for fun. Should drop the rpm's to ~1400.

I bet it gets me .7 mpg

I need to correct some bad info in my post.

1. it's 1600 at 60 mph (not 1700)
2. it's a 4.33 rear gear (not 4.55)
3. I measured the tires again today and there isn't the difference that I recalled....only 5% in circumference. So the rpms would only drop from 1600 to 1500 with the tire swap (not 1700 to 1400).
4. I'm revising my prediction to .5 mpg.

sometimes I get these trucks mixed up.

sorry if you all went out and bought new tires and rims today.

[solo379]

Originally Posted by rank

I wonder if there is any stats on this.

I didn't think so. Just a common sense. Stronger, lasts longer, doing the same job, as a weaker....

[heavyhaulerss]

[QUOTE=rank;429091]I get 7 summer and 6 winter with my M11 Cummins. 925,000 miles. 370/410hp. Peak hp at 1800. Peak torque at 1200. I shift at 1400 with an 80,000lb gross and it recovers to 1200.


I shift at 1700 min, loaded. any less & I'm lugging the engine. 1200 sems real close to lugging. at least it fells like it in my truck . usually 1300 or a hair under is the lowest I feel comfortable, otherwise I'll drop another gear.

[tracer]

OK, here's how it went during the first trip after the dyno tuning. With both tanks full, I picked up an empty 53" van trailer in Guelph, ON and drove to Sarnia, ON (Port Huron, MI is on the other side of the Detroit river). The shipper near Sarnia loaded me up with 43,500 lbs and I headed to Laredo, Texas via 69, 70, 57, 55 and so forth. Most of the time I drove 58 mph at 1325 rpm, with the cruise control on.

On Friday I ran into foul weather between Fremont, IN and Forte Wayne, IN. Because of snow, ice, and freezing rain it took me 1.5 hours to do 80 miles. Most of these miles were done in lower gears (7L, 7H, 8L), which certainly affected my fuel mileage. West of Indy I drove in strong cross-wind that continued some 100 miles into IL. This has cut my fuel mileage too.

I refueled in Matthew, MO at the Flying J, and the tanks took 151 gallons to "full". Distance traveled: 860 miles. So, I did ... 5.7 mpg only. But for driving in lower gears in Indiana and fighting the crosswinds in IL and IN, I'm positive I'd show 6 mpg or better.

My next refuel is going to be in Texas, 995 mi away. Will report the new fuel mileage from there. Hopefully it's going to be above 6 as I'm set on driving 57 mph at 1300 rpm all the way to Texas. The load weight is still 43,500 lbs.

Cat C15 550 hp, 1850 torque, 13 speed RTLO-18913, 3.73 rears, 295/75R22.5 tires; 2004 International 9400.

[rank]

[QUOTE=heavyhaulerss;429399]

Originally Posted by rank

I get 7 summer and 6 winter with my M11 Cummins. 925,000 miles. 370/410hp. Peak hp at 1800. Peak torque at 1200. I shift at 1400 with an 80,000lb gross and it recovers to 1200.


I shift at 1700 min, loaded. any less & I'm lugging the engine. 1200 sems real close to lugging. at least it fells like it in my truck . usually 1300 or a hair under is the lowest I feel comfortable, otherwise I'll drop another gear.

1700! Holy crap.

[allan5oh]

Cruising at slower speeds will increase fuel mileage.

[TomB985]

Tracer, what were your average MPGs before the tune?

[tracer]

Originally Posted by TomB985

Tracer, what were your average MPGs before the tune?

I could get 7.4 mpg going light (real life example: going from California back to Canada with 5,000 lb load) but as soon as there was heavy stuff in the box (over 40k lbs), the mpg would usually drop below 6, especially in winter. I have probably gained 0.2 - 0.3 of a mpg with bigger power. Will see what happens at my next fuel-up in Laredo, TX. One thing I noticed: before the up-rate I couldn't cruise at 1,300 rpm with 43,500 lbs going thru hills; the engine wanted 1325 minimum; or better yet - 1350. I could climb virtually any hill if I stayed at 1,400 rpm. I just checked the Dyno report for the tune-up I did 1 year ago with 1,650 torque: at 1,400 rpm: at that rpm I had 450 hp. Now, after the tune-up with 1850 torque, the engine can make ... 450 hp at 1200 rpm! I think I"m at 475 hp at 1300 rpm. That's a huge difference. I kept at 1,300 rpm all day today and the thing pulled like a bulldozer on all hills. I haven't downshifted once