air fuel ratio readings
Turbo Mini Forums

i decided to fit an air fuel ration gauge and at the same time change the turbo and actuator.

on start up i found the gauge reading 13.0 to 1 so adjusted to 14.5 and took it for a drive. pissing with rain and forgot to do up the throtle cable and have a reasonable exhaust leak some where.

any way put my foot down and as the revs climbed the reading went to 11ish to 1 on part throtle(the cable slipped)

i know i need to fix the exhaust and do up the cable but what should the readings be? obviously 14.5 at all times would be good but what counts as aceptable and what is dangerous?

If the exhaust is leaking before the Lambda sensor you are wasting your time, The readings will be totally innacurate. Fix the leak and then start testing.
Regards
Dave

Hi,
14.5 isn't much good anywhere really!
I think you'll want 12:1 ish on boost and about 15-16:1 on cruise (light throttle steady speed)
I'm sure someone'll shoot me down now
Cheers,
Gavin :)

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thats about right

BUT

exh leaks REALLY effect the reading your getting so be careful!

Alex

AlexF

I am currently looking to buy a air/fuel metering devise that uses a wide band 02 sensor but they are not cheep, looking around 250 AUS but very well worth it to know your engine is always on song so to speak.

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

OK i fixed the leak and adjusted the cable. adjusted the mixture and took it for a short drive. still the same 14ish at idle and down to about 11 or 12 on boost.

sounds fine to me.

i've got to do a bit more filing on mine this week, mines around 14 at idle but leans right out as you touch the accelerator then comes down to 10/11 on full throttle.

it was perfect untill i fixed the knackered choke seals, lol.

Edited by Nick on 26th Jun, 2007.

What would be the lifespan of the O2 sensor? Should you remove it and fit a bung when you've set the mixture or can you leave it there to provide a warning if it leans out?

from the info supplied with the sensor and gauge you can leave it all fitted and check it like all the other gauges, and calibrate it every 10,000 miles. if you leave it fitted but not powered the sensor will get damaged as will running leaded fuel.

AlexF

yeah i've got a stronger spring in there and changing from 3 in 1 to 20w50 has helped aswell, still needs a bit more fuel though i think.

need to go out for a play with the needle tomorrow night if its dry cos i'm on the rollers saturday morning.

I have a leaded head on my engine at the moment, if i run unleaded fuel with a lead additive will this damage the sensor?

Most probably yes.

Ah Balls! Now i need to buy an unleaded head from avonbar.

Well least i found out now and not after i had fitted my A/F Sensor.