P**s poor fuel economy

[78dude]

Okay, I take this in how we do it in Sweden, use KM
So you are able to do 272km on a tank of 45 to 50 liters? If so if we say that you use 50 liters of fuel to drive 272km, that means you use circa 1.83 liters of fuel per 10 km. I would say your car is heavy on petrol like my old E32 735iA

[sam325is]

nope it sould be right back at the 50 MPG end NOT the 0MPG end... thats what messing up my obd MPG Average.

any ideas what it could be anyone?

Sorry to put this so bluntly but you are wrong fella.

When you are not moving but the engine is running you are achieving exactly 0MPG

No forward movement but fuel being consumed
_______________________________________________

sorry mate but your wrong... as im coming to a stop enlighten me as to why my fuel consumption on the needle should be going from 30 mpg all the way past 10 to 0. it should go to the left past the past 40mpg past 50 mpg and to nothing and should then sit to the far left NOT to the right. on my obc whilst im at traffic light my avergae consumption is plummeting! its a fault of some sort.

any ideas?

[fastdiablo]

ask yourself how many miles you are covering for the the fuel used ? 0 miles, or 50 + miles ? . . .

[sam325is]

so its correct that(according to the MPG measures) im using more fuel sat at lights than i am going 80mph down a motor way

[Chris]

Yes, the 'swing-o-meter' is a purely instantaneous reference. For the second you are sitting at the traffic lights, you are using more fuel per mile than when the lights go green and you tear off down the slip road.

It's kind of Irish, but once you get it in your head that the economy guage only tells you your economy for that split second, it starts to make sense.

This is why the OBC was contrived. To tell you your average economy.

On a side note, i dont think the OBC gets it's info from the swing-o-meter so it probably has something to stop the main figure from plummeting the moment you pull over.

Cheers
Chris

[sam325is]

i know what your saying about fuel per mile. but it could say that by swinging totally to the left could it not?

and my obc average plummets when i stop at lights....more than if im gunning it..something isnt right.

[Chris]

Nope thats perfectly normal. The OBC is all about averages so for the first couple of miles after a reset it should be up and down like a nuns knickers on bath night.

When you are stopped, you are doing 0MPG (fuel consumed but no distance traveled) so swing-o-meter hits the right hand side. Temp guage, big white framed 0mpg section.

When you are rolling down hill with no throttle, the injectors turn off (above 1500rpm) so you are doing infinite or 999.9MPG (no fuel consumed but lots of distance traveled) so the swing-o-meter hits the left hand side. Fuel guage, past the big white 50mpg section.

Give me a mo and i'll host an old Excel spreadsheet i use for MPG calculations.

Chris

[Chris]

Right,
Try This CLICKY

Should let you download an excel spreadsheet.

Just reset the odometer every time you fill up, write it on the top of the receipt and then put the necessary figures in on the left hand side of the line.

I've left the details for my 320i touring on there so if you use one of the other sheets, you can still use mine as a rough reference.

Hop it helps, sort out your economy quandaries.

Cheers
Chris

[sam325is]

yea your right. nice one mate. i was writing those messages at work and since driving home i know what your saying now.

[ItsAllAboutTheE30]

Cheers Chris! I'll carry on as I am at the moment, but next time I fill up I'll start doing that. That way I can see if it makes a difference over the course of a whole tank. Fumes do smell quite rich when the car is cold to be honest and there's a fair amount of smoke produced when cold as well.

[Chris]

You want to see if it smells the same when it's warm as well, this usually indicates that the blue temp sender isn't telling the ECU the truth about the cars temp, so it overfuels.
Irritatingly, theres two temp sensors, Brown & Blue. Brown talks to the guage on the dash, and blue to the ECU. so you never really know if it's playing up.

Chris

[fastdiablo]

so its correct that(according to the MPG measures) im using more fuel sat at lights than i am going 80mph down a motor way

Sounds odd but yes . . . as Brian has already said . . .

At 80 mph you are using X amount of fuel giving Y mpg . . .

If you sit still long enough you could burn all the fuel in the tank with 0 miles covered giving you 0 mpg . . .