Am I wasting fuel?

[LowTech]

This is something that I've been wondering.
Lets say that I'm on a slight uphill grade, I shift up and put my foot to the floor till it gets up to a good shifting RPM.
Am I wasting fuel by having my foot on the floor?
Would it be better if I had my foot just past the point where it doesn't change the acceleration any?
I can feel the point of change if I back off the throttle.

I'm new to diesels, but I know how it works in a gas engine. Would like someone that understands the fuel delivery system to educate me.

 

[phil2968]

Diesels have a govenor that controls the fuel rate. You control the engine rpm setting and the gov keeps the engine at that speed by increasing or decreasing the amount of fuel.
Let's say you set your hand throttle going down the highway to 2000 rpm on level ground. When you come to a hill the rpm will stay the same (up to a point), but the gov will increase the fuel even up to full fuel to maintain that set rpm.
Make sense?
I would not say your wasting fuel, your just making the most out of the power the engine has.

 

[hoop]

No, You are not wasting fuel. The extra is just going back into your tank thru the bypass tubes.

 

[wreckerman893]

If there is black smoke coming out of the stack you are wasting fuel. Too much fuel...not enough air or you are lugging the engine.

 

[cattlerepairman]

How can you waste fuel when you are driving a Deuce??

Here is how I see it:

When your engine is under load and you plant the foot down onto the go pedal, you are instructing the injection pump to supply fuel up to the maximum injection quantity per cylinder.
The pump will also attempt to increase the rpm up to the governed limit. Depending on how much load is placed on the engine, the rpm increase may or may not be possible. Where the "fuel saving" comes in is when you decide to hold the engine rpm constant by easing off the pedal. This will reduce the injected fuel quantity a little. You can test that (with a passenger in the Deuce)...go up a steep grade and plant your foot down. The Deuce, like most older trucks, will now smoke black, regardless of whether or not the engine manages to increase speed in the chosen gear. Lift up your foot a little...the black smoke will decrease but the engine rpm do not necessarily drop. Sometimes that "neutral" range in which you can play is very small or non-existent, depending on how much the engine has to strain.

In short, yes, if you decide to ease up on the pedal you probably save a little fuel.

When I leaned to drive trucks I was taught that, if you cannot accelerate on a grade, your gear choice is too high. Observing that would take care of the black smoke issue.

 

[spicergear]

The other thing to do in an older diesel is to hold your gear until you crest the hill so you don't lug. Most people don't realize the inefficiency of too low of rpm's on an engine especially while trying to maintain or climb.

 

[Paul Wolfe]

Hi,

Short answer: Black smoke = unburnt fuel (wasted fuel). Any time the injector puts more fuel in the cylinder than there is air (oxygen) in the cylinder to completely burn the fuel you get black smoke.

 

[nk14zp]

The other thing to do in an older diesel is to hold your gear until you crest the hill so you don't lug. Most people don't realize the inefficiency of too low of rpm's on an engine especially while trying to maintain or climb.

 

[swbradley1]

Anyone who has been to my place knows there is a hill due east. I can't even get up to speed in 5th to even try to climb it so like most hills I just try to maintain RPMs until I get to the top. Some days I have to all the way to 3rd, sometimes I keep her in 4th.

Never a good idea to lug a diesel.

 

[goatijoe]

I try to run the hill by getting up enough speed or as much as i can on long hills to keep the rpms up when going up the hill. Most of the time there is a down hill then a uphill to get a good run with it up the next one. Try that it will pull a lot better up the hill when you do so.

 

[03silverado]

when im driving the 5 ton i do what cattlerepairman said i floor it then let off until i hear the engine r.p.m.'s drop then i give it just a little over not to the floor unless im on a nice hill she'll climb most of your hills with the pedal just past full throttle for that r.p.m.

 

[mikes47jeep]

simple anwser, if there is smoke there is wasted fuel

 

[LowTech]

Thanks everyone for the "no lugging", and how to "climb hills". I've got those covered. Many, many years of pulling trailers in the mountains, and I only lug it on down hills

This was more about "How" the fuel system determined how much fuel to inject.
I think this explains that which I had been feeling when I'm running about in one of the rigs.

How can you waste fuel when you are driving a Deuce??

Here is how I see it:

When your engine is under load and you plant the foot down onto the go pedal, you are instructing the injection pump to supply fuel up to the maximum injection quantity per cylinder.

In short, yes, if you decide to ease up on the pedal you probably save a little fuel.

When I leaned to drive trucks I was taught that, if you cannot accelerate on a grade, your gear choice is too high. Observing that would take care of the black smoke issue.

I'm going to work on keeping it just above that point where the RPM quits changing on such grades, slowly working it up instead of just flooring it And I do know about "too high a gear choice", had to teach that one to Elise when she was learning to drive her 109 w/ a slipping / oily clutch . . . in the Eastern Sierras
Now I'll have to teach her how to not "floor it" on grades. She's the one wasting the fuel, I'm the one that has to harvest it

 

[Truckoholic]

Just 'cause there's smoke, don't mean it's broke