apparently i have a 325ex

[Kershaw]

^ this. that's why the more you change your injectors, the more your obc is off. i have a friend with an m30 swap and the obc says he gets 25-30mpg. lol he gets 15-18mpg.

i have 17.5lb injectors (stock being 14.5) so it's not a huge difference, but it is off.

[nando]

you measured that over 1 gallon, which you couldn't possibly know accurately, plus the OBC said 30mpg which we know is way off (more things affect the total % difference other than pure size, reaction time has a big effect). "not a huge difference" is really 3-4mpg, enough to explain your anomaly (I once got a *real* 26.5mpg in my ix when it was bone stock and automatic).

[325ixa]

no it doesn't.

it reads an injector PW signal which it can translate into fuel volume. it knows how far you're going from the VSS input, so it's simply distance traveled/fuel volume = mpg.

did some research and you are right. Dont know where i got that ecu measures air flow and calculates consumption based on that.

injector puls, revs and speed in equasion gives consumption on obc.

[nando]

well, the econometer can be related approximately to engine load, which is related to airflow. old VW's used a MAP signal to do nearly the same thing as BMW, it's just not quite as accurate because it doesn't know the true mass of air or fuel.

[Isostar13]

Tire size? If you change too far from stock your speed and mileage will register differently, which could explain the higher reading.

I average about 20 city, maybe 22-24 highway if I absolutely baby it. I'm on stock 205/55/15 tires, with a stock m20 (no chip.)

[nando]

he has larger than stock injectors.

/end

[Bretts85E30]

Man as an eta I feel ashamed by the fact that I'm gettin the same mph as an ix at 23mpg it sucks

[Kershaw]

my tire size is smaller than stock. i run 205/50/15s. i think stock is 205/55 iirc.

with an eta, you can run the piss out of it and still get 30mpg. if you're getting 23mpg, you need to change your o2 sensor and go from there.

[Bretts85E30]

did that and my injectors and gas mileage shot up from 17-20mpg and that was a year and a half ago..... my thinking is its probably my afm

and stock tire size is like 195/65R14H

[Kershaw]

not for an ix.