Economy Gauge On My Dash Is Doing Funny Things?

[jaydece]

Hey All,

Was wondering if anyone else has this problem?

I noticed today while driving that my economy gauge gets stuck or moves from the yellow bar to the green bar like it's on drugs? not that I pay attention to it ....but it's just VERY annoying...

But then sometimes it will work normally?

Any idea's Anyone?

The car has only done 50,000km if this helps? never had a problem before, car is completely stock! FOR NOW......

[blacktop™]

It's instantaneous...Not an average reading

So just say your going foot to the floor it will be max yellow, then when you take your foot off the pedal it should switch over to max green.

[jaydece]

It's instantaneous...Not an average reading

So just say your going foot to the floor it will be max yellow, then when you take your foot off the pedal it should switch over to max green.

hey ryan aka blacktop, well thats exactly the problem.....I toke that picture last night with the car OFF!......

and while driving it will stay stuck on max yellow...then when it feels like it, it will goto max green....then like a bitch it will work normal like it should......

[cpitts]

The little needle also reacts to:
- full tank of juice (less than 1km driven) -> stuck on max yellow
- As soon as you get 1km driven -> swings to green area (because you're not caning it out of the servo anymore )
- the green/yellow intersection is actually your current fuel economy number (l/100km) so every needle movement is relative to that

So at the start of a new tank of juice, it'll be all over the joint. At the end of the tank, it'll be pretty steady.

[jaydece]

The little needle also reacts to:
- full tank of juice (less than 1km driven) -> stuck on max yellow
- As soon as you get 1km driven -> swings to green area (because you're not caning it out of the servo anymore )
- the green/yellow intersection is actually your current fuel economy number (l/100km) so every needle movement is relative to that

So at the start of a new tank of juice, it'll be all over the joint. At the end of the tank, it'll be pretty steady.

- full tank of juice (less than 1km driven) -> stuck on max yellow .......really? didnt know that......thats interesting.....

[cpitts]

If you think of it like a computer program, the car hasn't travelled 1km yet, so to calculate fuel consumed per kilometer means you need to divide by zero....... and that's impossible. So the default state is the worst case scenario (max usage).

[jp928]

Thats a vacuum gauge, as its an indirect indicator of consumption - full yellow is WOT(zero vacuum), full green is shut throttle (max vacuum), in the middle is....in the middle, no, more like a bit between feathered and cruising.
jp 08 gtb 6mt wagon.

[slackboy72]

Thats a vacuum gauge, as its an indirect indicator of consumption - full yellow is WOT(zero vacuum), full green is shut throttle (max vacuum), in the middle is....in the middle, no, more like a bit between feathered and cruising.
jp 08 gtb 6mt wagon.

Yeah, I remember these 'economy' gauges started appearing in the early 80s when people started freaking out about petrol going over 50c/l.
They're just inlet manifold vacuum gauges and don't really mean anything.
I would pay them no attention unless you're trying to save fuel and wan't some indication of how heavy you are with your right foot.

[Arith]

It's one of the most useless gauges in the dash. Guess they had to fill in that space with something. They could have been clever and practical by putting in a boost gauge for the turbo owners.

[cpitts]

<snip>They could have been clever and practical by putting in a boost gauge for the turbo owners.

AMEN to that! I wonder if it can be converted........ if it's just a vacuum pressure gauge.......... I'm sure it can be recailbrated
Would be fun to see it head into the red then.

[Arith]

I wonder if it can be converted........ if it's just a vacuum pressure gauge.......... I'm sure it can be recailbrated

Wow, that would be a very useful project to undertake! I'm sure it's just more than just swapping hoses here and there but that would be awesome to have an integrated boost gauge (I remember back in the 80's my uncle's Volvo had an in-built boost gauge)

[slackboy72]

Nah...
Surely you want to stick one of these in:
https://www.subarugenuineparts.com/prod ... cts_id=967
http://www.youtube.com/watch?v=4sRzhiIt-bg
http://www.youtube.com/watch?v=YASe6piJprs

[cpitts]

Nup, got in built Satnav so the ricepack is a no go.

[jp928]

If its behaviour changes with full tank, then it sounds like the ecu is interpreting manifold vacuum and driving the needle, rather than the gauge being a direct read of vacuum. Anybody ever seen bhind the dash, to know if there is a tube connected there, or just wires?
This would be Consistent with the temp gauge NOT really being a gauge - once car is up to temp, it never moves, even though actual temp moves, in my car, from 83C to 96C.
jp 08 gtb 6mt wagon