Quote:
Originally Posted by Cardinal Grammeter
Let me try this one more time.
This is based on observations of the Instant MPG Readout of a Scion w/Toyota engine.
Lets say you want 45 mpg.
Depress the pedal until you read 45 mpg in the dash display.
As long as you keep the pedal at that position, you will continue to get 45 mpg up hill and down hill no mattery what rpm the engine is turning (everything is in 5th gear from about 25-75 mph, mostly 30-60 mph, calm wind conditions)
Its was that simple.
If you disagree with what happened, you can talk to the Scion. I'm only reporting what I observed during 4 hours of driving.
Obviously with such a simple relationship, all the effort of this thread seems focused on the wrong parameters.
One relevant question might be, does Scion use fly by wire? This Scion is probably 2008-ish vintage.
Regards,
Tom
PS. As an exercise, let me quickly categorize your parameters of concern:
N=Negligible
C=Constant (non-varying)
C=Dependent Variable (function of another variable)
V=Varying (true variable)
N- quality of pavement
V- slope of the road
C,N- speed of the wind
C,N- direction of the wind
C- density of the air, (temp, humidity)
C- weight of the car
C- gear of the transmission
C,N- traffic
C- quality of tires
C- hardness of tires
C,N- altitude
C- temp of the engine
V- speed of the car (resistance of air is proportional to the square of speed)
D- rpm of the engine
V- power of the engine
So you are left with Speed, Slope, and Load.
Load = f(Speed, Slope)
QUESTION: What would happen if injector pulse width was a function of throttle position? (all other parameters constant of course)
ANSWER: MPG would remain constant no matter what speed engine/car is going.
QUESTION: Is this possible?
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Dear Tom,
This outcome looks very strange to me.
Fuel yield in (miles/gallon) is calculated as the coeficcient of:
speed (miles/hour) / consumption (galons/hour) = miles/galon
If you keep the throttle fixed, you may get a rather constant consumption in galons/hour. However, the miles you travel per hour will variate a lot depending on speed which depends mainly on slope.
Anyway, from another source of info, consumption of a diesel engine (probably any engine) depends "ceteris paribus" on two variables: throttle position and rpm. This is because the injector pump graph of cubic mm injected per rpm is convex if you look it from above, concave to the X axis, for a determined throttle position.
You have a family of harmonic curves where each represents a load, meaning a throttle position.
I got this information from BOSCH which is the maker of the injection pump.
However, as Diogenes said, "movement is proved moving", then I will check the same excercise you did with my car, before come to a definitive opinion.
Then we can compare results.
Until then,
Oldbeaver