apparently i have a 325ex

[Kershaw]

not for an ix.

[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]

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]

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

[nando]

he has larger than stock injectors.

/end

[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]

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.

[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]

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).

[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]

obc measures air flow not fuel.

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.

[Kershaw]

1.066 gallons. distance traveled, 33.9 miles.

this was in the original post.

how many of you passed 3rd grade again? ;)

i can not drive a full tank of gas at 65mph, i'd get waay too bored and i'd be late for work. i average 80-85mph on the highway and im no slouch in the city either. i usually get ~23mpg to a tank of gas. if i babied it and kept it strictly highway, i know i could get ~30mpg cross country if i wanted to. but i would never waste my time like that. it's not worth the $20 extra over 500 miles.

i once did this in my rx8, topped off, did a 30 mile cruise @ 65mph and topped off again. 24.5mpg. i cant do that on a regular basis. more like 20mpg.

[325ixa]

obc measures air flow not fuel.

[Wh33lhop]

Kershaw, did you seriously just go off of the OBC calculation after swapping injectors?

[downforce22]

I agree with both of you guys ^^ but 30 mpg is not totally unreasonable in an iX, depending on speed, temp and terrain. I just got another 28 mpg tank, of course I was driving like a grandma (65 mph) on the highway, normally 75, and speeding up downhill, but a properly running fresh m20 ix should get 25+ highway. The only way I see to improve to 32+ is to start at altitude and drive downhill a majority of the way. I heard upon 0 throttle the fuel is cut unless at idle. Not 100% on this, but the only way to gain anymore over 30 is to swap to the 3.64 final drive.