Real time consumption read out.

Exspeedaway · Nov 3, 2012

Did anyone noticed that when you coast to a stop sign or a light if you leave it in drive the real time consumption read's 0.0 and if you put it in neutral it show's 0.8l/100km??
Not a big deal but just trying to understand the logics behind this.
By the way sorry if it's not completely clear or for grammar mistake but im french canadian so im doing my best here.....(lol2)

paris1 · Nov 3, 2012

Next to "avg miles per hour" (???like I care?!) "current fuel economy is the second most useless readout on the trip computer. The only one that means anything to me is the average fuel consumption. And at the risk of hijacking your thread, has anyone ever suspected that zeroing out the average fuel consumption so you can check mileage on a particular leg of a trip really doesn't have any effect on the reading? Example: I drove my CX-5 home to Northern Calif. from San Diego where I bought it and put the first 565 miles on as pure freeway driving. The average readout said 34.2 mpg at the end of the trip which jibed pretty well with the 34.4 figure I calculated at the pump. So I zeroed out the average readout figuring the next tankful would be pretty much around town driving here at home and I wanted to see how much difference there qould be. When I filled it up again the readout said 30.4 mpg, but actual calculation said 28.15. The 30.4 figure was so far off the real mileage (compared to the relative accuracy of the prior calculation) that it looked suspiciously to me like an average of the first tank of freeway driving and the second tank of city driving. So I'm feeling like zeroing out the reading in between tanks really didn't accomplish anything. Any thoughts?

Exspeedaway · Nov 3, 2012

Except the fact that you find the current fuel economy useless you dont bring much info to my question, not that i really care.

watermelon · Nov 3, 2012

Exspeedaway said:
Except the fact that you find the current fuel economy useless you dont bring much info to my question, not that i really care.

lets say you are coasting at around 60km/h and leave it in gear. the readout says 0.0 which should be correct since the car is in gear leaving the wheels connected to the engine. The engine in this case doesn't need to deliver fuel to the combustion chamber to keep the pistons turning over - the wheels are doing that for you.

Now, if you're coasting from said speed in neutral, well the wheels are no longer connected to the engine, so something has to keep the pistons firing and thus keep the engine from stalling. So it uses fuel, and that is the .8 readout that you are seeing.

now if you're at a stoplight at zerospeed and just idling, the readout says 0.0\well technically this is incorrect as it SHOULD say that .8 consumption figure, but that would just piss people off, so that 0.0 is a little white lie when you're stopped and idling.

what does this all mean? well if you're chasing good fuel economy, there are scenarios where you're better off leaving it in gear as opposed to neutral.

Exspeedaway · Nov 3, 2012

watermelon said:
lets say you are coasting at around 60km/h and leave it in gear. the readout says 0.0 which should be correct since the car is in gear leaving the wheels connected to the engine. The engine in this case doesn't need to deliver fuel to the combustion chamber to keep the pistons turning over - the wheels are doing that for you.

Now, if you're coasting from said speed in neutral, well the wheels are no longer connected to the engine, so something has to keep the pistons firing and thus keep the engine from stalling. So it uses fuel, and that is the .8 readout that you are seeing.

now if you're at a stoplight at zerospeed and just idling, the readout says 0.0\well technically this is incorrect as it SHOULD say that .8 consumption figure, but that would just piss people off, so that 0.0 is a little white lie when you're stopped and idling.

what does this all mean? well if you're chasing good fuel economy, there are scenarios where you're better off leaving it in gear as opposed to neutral.

It make sense, thank's for the reply.

watermelon · Nov 5, 2012

HTML:

Exspeedaway said:
It make sense, thank's for the reply.

one small correction, at idle the readout just goes to --.-- which is their way of getting around that little white lie thing. No one wants to see the car fuel consumption while stopped and idling.

oaklandopen · Nov 5, 2012

If you are in gear and coasting (slowing) then your true mileage would really be infinite since youre not using fuel. if you put it in neutral and coast then it will calculate your mileage through injector duty cycle and wheel speed etc

at a stop with the engine running it would read 0 because youre simply not going anywhere. but yea no one likes a big fat 0 so its just dashed out

in my car during a coast in gear its max is 99.9mpg. technically i suppose if the incline was steep enough and long enough for you to stay a constant speed, even with your engine operating you would never run out of fuel. on that same hill if you coasted in neutral with the engine running at idle you would run out of fuel, and your mileage readout would be fantastic as well

Real time consumption read out.

Exspeedaway

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paris1

Exspeedaway

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watermelon

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Exspeedaway

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watermelon

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oaklandopen

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