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Re: Rpm!
Start....a new thread.....
in another forum....this is off topic....
this was about......
rpm and it's effect......
on milage.......
pertaining to vehicles.......
in this universe.........
I've stated my findings on rpm vs milage. I've been talking to others at the shop with different engines/vehicles/gearing etc.
Kepp in mind I'm talking about how a mechanical inj diesel (6.9/7.3 ford 5.7/6.2/6.5 gm) works. The throttle pedal is only connected to a spring inside the governor box(in effect). When you step on the throttle you are only pulling a spring and allowing the governor to move to a new limit. The injectors spit the same volume of fuel at a throttle setting and the only difference is rpm.
In other words, lets say it's 50cc of fuel at low rpm governor setting, it is also 50cc at high rpm governor setting, only it fills the vial faster.(when setting the inj pump up on the bench) It only gives more fuel to accelerate the engine as once the no load rpm is reached the throttle is back to idle position. (low or high idle it's called even though I called it low/high rpm setting)
Not sure if I'm explaining it clear enough, I'll try to use % to clarify.
Idle no load 750 rpm = 10% throttle
high idle no load 3500 rpm = 10% throttle
Accelerating = 11% - 100% throttle until desired rpm is reached then 10%
Decellerating from high idle = 0% until low idle then it goes to 10%
This is in a perfect world etc.
Reality is 10% low idle and probably 13-14% at high idle because of the extra resistence from the higher rpm.
Also, driving (with a load) it would be different too.
100% to accelerate then 20% to maintain 50mph (example)
100% to accelerate then 25% to maintain 60mph.
This is why not only rpm uses more fuel, but the increase in resistance causes the throttle to return to a higher % setting which also uses more fuel.
The question then is, what is more important or causes more effect, rpm or throttle setting?
From my experience, I say rpm, because whether empty or loaded (the truck, not me) the milage doesn't vary. But empty or loaded the milage varies it's greatest amount by changing the rpm.
Empty 100kmh 25mpg
empty 140 19
loaded 100 23
loaded 140 17
So, rpm makes 6mpg difference and load makes 2mpg difference.
Also, 6.2gm 3/4ton reg cab/6ft box with 3.73 gear turbo 400 tranny (no OD) 19mpg at 100km's.
He's turning almost 3000rpm. My 7.3/e4od/3.55 gear one ton/4 door/8ft box gets 25 but I'm turning around 2100rpm.
Anyone else have any results from driving at different rpm's and want to share?
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