[firebird_1252]

sorry if this is in the wrong forum but i need some insite. i have a 04 MBN cat. 435 hp. anyway, i was reading on another forum that there is some stuff to do to them to make them run a bit better and get some more fuel milage out of them. i heard a 10 ohm resistor in the fuel pump wire, and some other stuff would really make it get better milage. all though right now, i'm pretty happy with the milage but it could be better. i get about on the norm 6.1mpg pulling rail containers up and down i81 and i83 always at 80000lbs. the truck has a 10 speed with 3.73's. the truck goes in friday night to cat to get the over head ran and a pm so i figured i'd ask here before bringing it there. one thing i will not do is straight pipes. thanks for the info guys

[Maniac]

i heard a 10 ohm resistor in the fuel pump wire

A little more power, thats all it will do, running that heavy with those type of trailers, you are doing as good as you will ever see, the overhead WILL help but don't expect miracles

[firebird_1252]

Originally Posted by Maniac

A little more power, thats all it will do, running that heavy with those type of trailers, you are doing as good as you will ever see, the overhead WILL help but don't expect miracles

kinda figured that. i run like 67mph too. i over heard people talking saying the mufflers kill that motor (they have cat. converters in them? ), something with the boost and i know you can get the ecm to be flashed as a 6nz motor. but if its only going to give me .25 mpg diffrence i'll save my money.

[Maniac]

Originally Posted by firebird_1252

kinda figured that. i run like 67mph too. i over heard people talking saying the mufflers kill that motor (they have cat. converters in them? ), something with the boost and i know you can get the ecm to be flashed as a 6nz motor. but if its only going to give me .25 mpg diffrence i'll save my money.

Yeah the mufflers are restrictive, but also expensive to convert it over, if you HAD to replace them I would go for ones with lower restriction, you will still be fighting those trailers

[firebird_1252]

what do i have to do to convert them? if anything i was thinking just getting mufflers from like an 02. ( i have a columbia). i defintally fight these trailers. that truck crys going up 81 loaded. not loaded i can easly hold 70 (where the computer cuts it out). i'm kinda wondering if a muffler is "blown out" the truck is kinda loud. i have dual exhaust behind the cab but they're also turned straight back. i talk to people all the time with detroits (old 12.7's) and they arent doing much better if better all all then me.

what i learned is that idling kills the milage. even though i'm home every night, i average idling 2-5 hours a day so i'll be getting a tripac in sept. pa is doing a grant system and they eat 50% of the total bill. i knwo what most are thinking but i'm not pulling cans for much longer. anyway, when i idle i go from my 6.1mpg down to a low of 5.3mpg. the way i figure it. the apu will still pay for itself.

also a HUGE HUGE HUGE way to kill the milage is take off hard. taking off like you got an egg under the peddle and under 1400 rpm makes a world of diffrence.

[Maniac]

If you have verticals behind the cab/sleeper, I'm pretty sure they are strait thru's, for some reason I thought you had a KW, which has very restrictive duals UNDER the truck.

You pretty much are doing everything right, keep your tires inflated properly (this would help on the trailer but I realize it's impossible)

[firebird_1252]

wish i had a kw.. it wouldnt handle like a damn barge ... anyway no its a 04 columbia. the tires are going from low pros to regular 22.5's. if HUGE if i land this work i'm dropping the gears to 3.55s. when i do the tires i'm getting 6 alum. wheels.

[Maniac]

Originally Posted by firebird_1252

wish i had a kw.. it wouldnt handle like a damn barge ... anyway no its a 04 columbia. the tires are going from low pros to regular 22.5's. if HUGE if i land this work i'm dropping the gears to 3.55s. when i do the tires i'm getting 6 alum. wheels.

What ratio do you have?, don't be so quick to change the ratio, it will be around 4 grand and might not do a whole lot, aluminum wheels are 60 pounds each, the steel ones are 90 pounds, not much weight to be saved, but they do look better, and will last longer

[firebird_1252]

i have 3.73's with a 10 speed. right now low pro 22.5's but they'll be switched out in dec or jan for reg 22.5's.

oh and a fuel milage update. as i said i run 65-70 normally 67mph. 75% of the time at 80k lbs. this is with about 5-7 hours of idling. 6.31mpg. oh and hills on I81 and I83. i am almost postive once i stop pulling these damn rail cars, a normal trailer/reefer and if on flat ground i can get 6.5. love how people slam cat for not being good on fuel. and what makes me laugh, is that people slam the MBN motor.

with the alum. wheels it will look a lot better. i think i'll do 6 for the time being when i swap the tires out.

[Maniac]

love how people slam cat for not being good on fuel.

Fuel mileage starts with the driver, not the engine, anything above 6 is very respectable