Air/fuel meter

[Kevin Bacon 5]

Incidentally, the blanking plate's (if you haven't got that type or a spare one) part number is 535 957 087 and costs £2 from VAG.

 

Kev

[exturbo2003 0]

very nice meter mate, i like the way you have done them and if i hadnt bought one recently i would buy it. nice work

[stormseeker 0]

Look - it's spawned a twin...

 

Testing on the bench (desk!) showing 0.7V in dot mode.

 

(Note the copious amounts of green PVC tape used for that professional look!)

 

Only cost me £4 for the bargraph driver chip as I had all the other bits lying around in my numerous boxes of bits :-)

 

 

:D

 

Just need to hack into the loom and find somewhere to mount it... :shock: bit tight for room with the heated seat controls being in the stack where Kev mounted his. Might move the ABS warning light to the single square blank next to the heated rear window switch and put the LED meter in a blank where the ABS light was. Always thought the big orange ABS light was a bit OTT :-)

[Kevin Bacon 5]

Nice one, good man!

 

You prefer dot mode then? You can have it switchable (dot/bar) if interested.

 

Not bad for under a tenner, eh?

 

Kev

[Fat Tony 0]

Whats the red light for?

 

Sorry if it's obvious but you both have them. :oops:

[Henny 0]

Red LED = Power on 8)

[stormseeker 0]

The position of the red LED above the bargraph marks stoichiometric - i.e. perfect mix.

 

I've made it bar/dot switchable and will install a power switch when it gets installed in the car - just in case it's too distracting for me when driving.

[Henny 0]

The position of the red LED above the bargraph marks stoichiometric - i.e. perfect mix.

 

Ooh, nice idea... I like that... 8)

 

I've made it bar/dot switchable and will install a power switch when it gets installed in the car - just in case it's too distracting for me when driving.

 

also a good idea... I'm half way through building one of these, and that was my first thought... I'm also thinking about putting in a switch so that I can flick it to "night" setting and make it much dimmer... If I get really carried away, I may even put in a light sensor and make it dim automatically! :roll: :lol:

 

Looks good so far though stormseeker 8)

[stormseeker 0]

The position of the red LED above the bargraph marks stoichiometric - i.e. perfect mix.

 

Ooh, nice idea... I like that... 8)

 

that was Kev's idea

 

I've made it bar/dot switchable and will install a power switch when it gets installed in the car - just in case it's too distracting for me when driving.

 

also a good idea... I'm half way through building one of these, and that was my first thought... I'm also thinking about putting in a switch so that I can flick it to "night" setting and make it much dimmer... If I get really carried away, I may even put in a light sensor and make it dim automatically! :roll: :lol:

 

Looks good so far though stormseeker 8)

 

yeah - I thought about dimming too...

[stevemac 0]

If you want one, it'll cost about a tenner (much cheaper than purpose made ones, and just as accurate) to make and I'll post complete instructions and a parts list if there is sufficient interest.

 

Kev - I fancy sticking one of these on my G60 - any chance you could PM some instructions & parts list to me.

 

Cheers

[Dubcharged 0]

Nice product Kev. I recommend all performance car owners especially G60's to have an A/F gauge just in case.

 

Couple of points to remember though: The reading on any gauge is only as good as the lambda it reads from. When using the standard lambda, you cannot accurately get readings above stoich (14.7:1) ie you cannot use it to fine tune your motor in the WOT range. It will show you rich/stoich/lean but just as an indication, not an accurate figure which nevertheless is very essential to know. For tuning purposes you have to use a wideband lambda which is where the cost surges since as the name suggests these are accurate up to around 9:1.

 

Keep up the good work Kev, its about time people started to see what their engines are being subjected to!

[G60Jet 1]

okay

 

I've just spent the day moving and adding gauges to My C

 

The A-piller is in and houseing the Boost Gauge and A/F gauge

 

I've got the A/F gauge all wired up and running but the meter is showing rich, all the way as if the O2 sensor was sending a constand one volt.

 

Is the o2 sensor dead? i thought they gave no voltage back when dead

[Rossco 0]

What about us without lambda probes (16v boys) can we just bung one in the zorst or is it way mor complex than that?

[h100vw 0]

Nigel, did you let it run for a while until the probe warms up? And not trying to have you suck eggs, it's connected to the output and not the power?

 

Gavin

[GazzaG60 0]

Nigel-get a good earth, double up on it for testing see if it sorts itself. earth is the baddie in that one.

 

wideband is great. i agree with exturbo in that the AF is better for fault finding that showing true readings. it shows stoich rather well though.

 

on the wideband. get the NGK probe over the bosch. NGK does 8:1 whereas Bosch does 10:1

[G60Jet 1]

i've ran the car well and it don't move :( gonna double check everything at somepoint.

 

I've tapped into the purple probe wire. which I checked in the manual.

[G60Jet 1]

okay Well I've got the meter running, found a bad connection!!! the meter is not acting as i expected it to. So i am going to earth the meter to the probe and see what happenes before i go changing the probe itself. the meter is reading in the middle of the range and only moving one LED either way correctly, but the whole meter is trying to light when blasting it. So i think its an earthing problem. Mind you i did cheat and earth it to the chassis rather than battery.

[Kevin Bacon 5]

Nice product Kev. I recommend all performance car owners especially G60's to have an A/F gauge just in case.

 

Couple of points to remember though: The reading on any gauge is only as good as the lambda it reads from. When using the standard lambda, you cannot accurately get readings above stoich (14.7:1) ie you cannot use it to fine tune your motor in the WOT range. It will show you rich/stoich/lean but just as an indication, not an accurate figure which nevertheless is very essential to know. For tuning purposes you have to use a wideband lambda which is where the cost surges since as the name suggests these are accurate up to around 9:1.

 

Keep up the good work Kev, its about time people started to see what their engines are being subjected to!

 

 

Good points mate and very valid. I thought about installing a second probe (wideband) for the sole purpose of running the AF meter but couldn't be arsed! I'm not terribly interested in ultimate accuracy, all I want to see is when the probe is dead (stuck at 0.4V) and 0.7V at WOT, hence the simplicity of my meter (red light over 7th bar). For you forced induction boys, then yes I would probably go for something more accurate, but for NA, it's just a rough guide, which suits me :lol:

 

Henny, you can substitute one of the 220K ohm resistors for a 4.7K ohm variable pot and adjust the LED brightness manually :lol:

 

Parts list is as follows:-

 

1 x LM3914 Chip

1 x 18 pin IC holder

1 x 10 bar LED module

1 x 2.2uf tantalum bead capacitor for probe voltage smoothing.

1 x 3mm 12V red LED

2 x 2.2K resistors (or 1 x 2.2K & 1 x 4.7K for LED dimming)

1 x 10Mohm resistor - for the input, high impedance ensures minimal, if any, current drain from the probe.

1 x 2.2uf electrolytic capacitor (smooths the car's 12V supply)

Some heatshrink

Lengths of white, red and black wire

Some thin solid core wire for the LED module

Some preformed circuit (aka breadboard)

 

I've lost the circuit diagram unfortunately, but I'm sure Stormseeker won't mind forwarding the one I sent him. But you can also try a google search on 'Air fuel meter' as there is plenty of info on them online.

 

Meter Behaviour:-

 

At idle and driving at moderate speed, the meter will flick up and down constantly, indicating the ECU is in closed loop mode and hunting for stoichemetric. The meter jumps up and down because the ECU is using the probe to monitor O2 content and pulses the injectors 2-3 times a second to lean and enrichen constantly, for economy/emmisions more than anything else.

 

At WOT, the ECU goes into Open loop mode and enrichens the mixture. During OLM, the probe is not consulted, the ECU just blasts that old motion potion in :lol:

 

When you back off the throttle, the meter will extinguish all it's lights, indicating the ECU has shut off the fuelling for over-run.

 

If you get all that happening, the ECU is doing it's job and passes with distinction.

 

Hope this helps

Kev

[Kevin Bacon 5]

okay Well I've got the meter running, found a bad connection!!! the meter is not acting as i expected it to. So i am going to earth the meter to the probe and see what happenes before i go changing the probe itself. the meter is reading in the middle of the range and only moving one LED either way correctly, but the whole meter is trying to light when blasting it. So i think its an earthing problem. Mind you i did cheat and earth it to the chassis rather than battery.

 

No don't do that mate. You'll be putting the entire load of the meter through the probe, which it won't like. The meter must be earthed to the battery or the chassis.

 

If the meter isn't moving much, either the probe is dead (sits at 0.4V) after preheat mode has expired or you've used to high a resistance on the reference pin of the chip.

 

Kev

[G60Jet 1]

kevhaywire, I've got a Autometer Ultra light A/F meter

 

so to test the probe

 

do i tap the probe wire through a digital meter to the earth/battery then.

[Kevin Bacon 5]

kevhaywire, I've got a Autometer Ultra light A/F meter

 

In that case I don't know what the problem is.

 

K

[Dubcharged 0]

 

At WOT, the ECU goes into Open loop mode and enrichens the mixture. During OLM, the probe is not consulted, the ECU just blasts that old motion potion in :lol:

 

 

 

 

And this is where the G60 boys can physically see the digi-lag in action on the gauge!!!

[Henny 0]

Kev? Here's your diagram... 8)

[stormseeker 0]

Henny beat me to it 8)

 

Kev - just a small point - the cct diag shows 2 x 2k2 resisitors, but your note above mentions 2 x 220k :?: :?: :?:

 

I've built mine with 2k2 - worked ok on the bench :?:

[G60Jet 1]

I've got mine working!!! probe is fine, it had come un connected after i did not reconnect it correctly.

 

One thing worth pointing out though, when under WOT and the Lambda isn't used, that digi Lag is very easy to see on the meter!