fuel consumption

[scooby999]

I normally get about 180 to 200 miles out of a tank of fuel.
i have an air/fuel gauge in the car and it nearly allways sits on lean.I was just wondering how i could get it into the normal range.
The only mods i have on the car is a 3" middle and back box exhaust and i cant have it mapped as it is unmappable (MY98 Wagon JDM) and its allways run on tescos 99.

any ideas???

thanks jason

[andy-m]

bad lambda ?

Mines a 95 STI RA ECU with a chip so not quite the same as yours but I get 220 - 240 on a tank and still have 10 ltrs left.
with throttle on idle or holding a steady speed, my AFR jumps between lean and rich. On full throttle - its fully rich, and decelerating - its fully lean.

[scooby999]

I did change the lambda about 6 months
Its does flick between 800 to 500rpm on idle and under hard acceleration between 3rd and 4th and 5th it does trigger the fuel cut off thingy(the thing that slams you into the windscreen)

[andy-m]

I never get the fuel cut. I always thought that was due to overboosting

[scooby999]

I think it is ,didnt know if it was related

[Scott.T]

Afr should oscillate around stoichiometric at idle and cruise.
On an early classic it should stay in the stoichiometric range below 3000rpm or during vacum/negative boost. Once you go above either it should start to richen up or show rich on a basic afr gauge.

[scooby999]

Originally Posted by SilverSurfer

Afr should oscillate around stoichiometric at idle and cruise.
On an early classic it should stay in the stoichiometric range below 3000rpm or during vacum/negative boost. Once you go above either it should start to richen up or show rich on a basic afr gauge.

Is there anything I can do or change to sort it out.
I was told to have it mapped but as it cant be mapped ,I guess it would be tricky.

[Scott.T]

Can you post up a vid clip of the gauge in action.
It may be just a lambda fault.
The other thing to try is disconnect the lambda and see if the gauge activity changes.
The voltage going into the gauge is provided by the lambda sensor. The lambda sensor generates a small voltage due to a chemical reaction to the oxygen content in the exhaust gasses. It doesn't need to be connected to the ECU to provide this voltage. The ECU just reacts to what voltage it see's during idle/cruise to fine tune the fuel mix for emissions purposes. The car will run fine with it disconnected.

[scooby999]

Originally Posted by SilverSurfer

Can you post up a vid clip of the gauge in action.
It may be just a lambda fault.
The other thing to try is disconnect the lambda and see if the gauge activity changes.
The voltage going into the gauge is provided by the lambda sensor. The lambda sensor generates a small voltage due to a chemical reaction to the oxygen content in the exhaust gasses. It doesn't need to be connected to the ECU to provide this voltage. The ECU just reacts to what voltage it see's during idle/cruise to fine tune the fuel mix for emissions purposes. The car will run fine with it disconnected.

Ok thanks I will give that a try.

Also my bad,it stsys on RICH not lean..........I really must learn to read

[Scott.T]

If it's reading rich all the time then I expect your lambda has failed.
These drop volts and therefore the ECU think's it's running lean and chucks in fuel.
You will probably find that on idle and cruise you are running about 12.5AFR instead of 14.7AFR.

http://www.gendan.co.uk/oxygen_lambd...reza_2.0i.html
Just pick the one that matches the connector you have (early or late classic) and gives at least the minimum cable length. Don't worry about the model description lists.

Or just get a 3-wire universal which comes without a connector and wire it in yourself.
I'm running a £30 universal in mine.