4m50 highway use?

boostin

Adventurer
Hey guys.

Just wondering what is the preferred RPM to maximize fuel mileage on the 4M50 ?

My truck is a 2wd 6 speed auto so little different then the fg but I am sure this engine has a sweet spot.
 

westyss

Explorer
Hey guys.

Just wondering what is the preferred RPM to maximize fuel mileage on the 4M50 ?

My truck is a 2wd 6 speed auto so little different then the fg but I am sure this engine has a sweet spot.

Your fuel mileage is directly linked to speed due to drag coefficient so the slower the better, most say they like a speed due to comfort and handling, but if its MPG's you are looking for then go slow. I like to putz along at 60mph for comfort, I did a MPG comparison one year on a trip from BC to Death Valley and back, on the way there I stayed at 60MPH, on the way back I stayed at 65MPH, oddly enough I had better MPG at the higher speed but with the two comparisons there are still some variables, like head wind, tail wind. Do you have a box on the back or is it low profile?
 

boostin

Adventurer
It's actually a work truck with a deck on it so pretty aero. I have had some cars where a little faster actually is better mpg cause you are more in the engines sweet spot.

But this is my first larger diesel and it seems wrong to be revving at 2400 @110kph but I seemed to get great fuel economy.
 

DzlToy

Explorer
Aero will play less of a role at speeds up to about 55-60 MPH (box vs flatbed). In the 07 FE with six speed auto trans and flat bed, I will average 15 MPG. If you get up to 65-70 MPH on the hwy, the MPG drops down to about 12-13.

The high RPM is a function of the gutless wonder that MFTB sought to install into these trucks. A mate's Dodge 2500 on 35's runs about 1200 RPM at 65 MPH and gets high teens for MPG on the hwy. (that is with an aftermarket programmer and EGR deletes netting about 450 HP and 1,000 foot pounds of torque - not exactly Canter numbers, but who is counting :D
 

DzlToy

Explorer
I have only done a 10-12 mile test drive on a 2013 FE, so I am not the one to comment on that in the long term, but the one I drove was a turd for sure and it was empty.

I do know the axle ratios are at least 5.13 and maybe 5.29 or even 5.71, so that is going to keep RPM up with small tires. The engines are supposedly designed for it, but I cant imagine low HP and high RPM is good for fuel economy in any car or truck, much less one that is heavy and has the aerodynamics of a brick.

A higher HP and more importantly higher TQ engine with some higher R&P gears would do wonders for drivability and MPG IMO. The similar weight Dodge truck above is a perfect example, with rougly triple the HP and TQ of the 150 HP Fuso.
 

boostin

Adventurer
Aero will play less of a role at speeds up to about 55-60 MPH (box vs flatbed). In the 07 FE with six speed auto trans and flat bed, I will average 15 MPG. If you get up to 65-70 MPH on the hwy, the MPG drops down to about 12-13.

The high RPM is a function of the gutless wonder that MFTB sought to install into these trucks. A mate's Dodge 2500 on 35's runs about 1200 RPM at 65 MPH and gets high teens for MPG on the hwy. (that is with an aftermarket programmer and EGR deletes netting about 450 HP and 1,000 foot pounds of torque - not exactly Canter numbers, but who is counting :D

Do you have a 07 or 13?

I know the 13 has much less power then a 07
 

DzlToy

Explorer
I have an 07 and you are right, much more power than a 13, but its still not all that great. Was looking for an "upgrade" when I did the test drive on the 13 model and decided to keep what I have. The new trucks are awful IMO.
 

boostin

Adventurer
I have an 07 and you are right, much more power than a 13, but its still not all that great. Was looking for an "upgrade" when I did the test drive on the 13 model and decided to keep what I have. The new trucks are awful IMO.

What exactly do u do with the 07 fe..work or play?
 

DzlToy

Explorer
both, it has a flat bed on it and is used for "hauling" (I have had 6500 pounds on it) as well as for hauling a Polaris XP1000 RZR, which I drive onto the bed using 8 foot ramps. Easier than pulling a trailer and rides pretty good. RZR is about 1500 pounds loaded up with gear.
 

DzlToy

Explorer
It was quite noticeable, lol.

I ran back roads at 45-50 MPH and was very careful with cornering, braking, etc. The load was low COG and well distributed over the entire bed, as it was 1" thick sheets of a high density plastic that weighs about 400 pounds per sheet. I think I had 20 sheets on there, but some were only 5/8" thick or 3/4" thick. It is not something that I will ever need to do again, but I know the truck willl handle it.

Rear duallies were at 80 psi and were almost touching on the sidewalls. Rear axle was on the overload springs and only had minimal travel. Not scary by any means, just had to be really really careful. I was probably near max GVW for that truck, which i think is 14,000.
 

boostin

Adventurer
Hmm very interesting... My gvw is 18 000. I towed a 10 000 pound trailer behind it...did 60-65mph ok on flat but hills where another story.


I bought this truck to start a business and choose mitsu cause I have only had and love mitsu cars. I assumed I could do 65 with a load easy but so far I am wondering if I need another truck for my business cause this one seems useless .

I did do some in town runs with 6000 pounds and it seemed pretty happy but I need it to run good on the highway.


I am thinking a proper sized turbo would make a world of difference
 

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