6 replies to this topic

[api100]

I've had a 2005 Revolution with a 400 Cat for about 5 years. Does anyone have suggestions for possible modifications  to the engine to improve power and possibly improve mileage?  

My previous coach had a 275 Cummins which pulled hills just as well if not better than the Cat and got 9 mpg on a 6000 mi trip.

Yes, the previous coach was lighter. My Cat gets 6.5 mpg on a 6000 mi trip.

Also will I have to go to a Cat dealer to have anything done to the engine?

Thanks!

Andy

[wolfe10]

Comparing MPG and power between two coaches is a LOT more complicated than it would first appear.

Were the two coaches the same weight? Heavier is slower (with same HP) and takes more fuel. Physics is physics

Were they the same HP (producing more HP does require more fuel)?

Were they both compliant with the same emissions standards? Comparing a per-emissions to post-emissions engine?

But, to answer your question, I would start by checking your air filter minder. If air flow is restricted, HP and MPG will suffer on any diesel. Said another way, you can't feed any diesel too much air.

Also, on a hot day with less than 1/4 tank of fuel, check fuel temperature. If more than 10 degrees F more than ambient temperature, consider a fuel cooler (I have used transmission coolers) in the fuel return line from engine to fuel tank. Just make sure you cover it in the winter! But, it is those long hard pulls in the summer that often elicit those "I need more power" issues.

Also, as Caterpillar recommends, be sure to have the initial valve adjustment around 30,000 miles. Valves well out of adjustment affects MPG and HP.

[DickandLois]

Hi Andy, Like Brett said. A little like apples and oranges. The 275 Cummins was likely matched to a Allison 4 speed or 5 speed transmission. From your information I'm thinking thinking an MT 643- 4 speed.The big items are weight, body profile and gearing between the two coaches. Also 125 more HP. More ponies equals more oats. More power is not always a good thing, its how all the parts come together.

Are you driving them the same ?

Was the coach new or a couple years old when you purchased it. Filters, injector pump setup, ECM program, Transmission style and software setup, CAC size, tappet settings, Turbo set up and boost, plus air flow through the engine all come into play.

One could go through the system and get a good shop to check things out to see where you could gain some mileage, no single item will get allot of mpg.
The other is a complete Re-power. replacing the engine with a Detroit 550 and all its required Radiator and CAC changes plus and Allison 4000 transmission might work real good. A friend had this setup installed in his coach and its on its first run. Getting about 18 mpg and all the power one could ever use on a 45ft. coach / 50,000 lbs or so, but at a price.
Note received later this AM, MPG is now 20+. Running the Grapevine at 75 mph.

Re-power also requires the use of DEF fluid. Your current set up is Pre. 07 or 2010 EPA. a lot less involved then to meet the new standards.

Rich.

[desertdeals69]

If I remember correctly the 275 Cummins is a ISB computer engine which for the most part was connected to a Allison MD3060. A 190,230,260 was a mechanical engine and connected to the Allison MT 643. I have installed a ISB 275/MD3060 in my 32 foot coach an get between 10 and 11 mpg towing a 1/2 Silverado.

[DickandLois]

DD you are correct, but a number of Freightliner Chassis had the 275 HP an MT 643 up to the start of the 1999 chassis year and the MD 3060 used from then. The MT-643 is 660flb torque at 70,000 lb load and the MD 3060 is rated at around 750flb torque at a load of around 40,000 lbs.
Close with out looking up the exact specks.

Rich.

[desertdeals69]

My ISB 275 and MD3060 came out of a 98 Freightliner Discovery.

[api100]

Thanks for the comments and suggestions. My coach now has 50k miles. I was not aware of the need for valve adjustments at 30k miles so I'll get this checked , will also check air flow. Thanks! Andy