Mixture Monitor
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  1. #1
    Budding Architect ???? pugrambo's Avatar
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    Default Mixture Monitor

    i just finished putting one of these kits together from Jaycar and put it in the car to monitor the A/F mixture in the 604

    i bought an EGO sensor (single wire) from repco and welded it into place in one of the engine pipes

    very simple and works a treat and now i can monitor the air/fuel ratio of the engine

    it is even handy as an economy guage

    the only thing that has me baffled is that when i am on trailing throttle the read out reads rich

    when i just touch the go pedal it comes back to normal running A/F and when i put my foot down going uphill it reads towards the rich side and when i floor it and open up the secondary throat on the carb it reads between rich and normal depending on the road speed so that from standing start it will read rich when flat but very quickly reads normal A/F and if foot kept flat starts to come back to rich again but by this time i have gone from 0-40-180km/h respectively

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    so at say around 80-140km/h the A/F is normal running

    so anyone else want to add any comments to my findings

    BTW i also had the water injection going at the same time and this may have had an effect on the readings and it also 1/2 the fuel in the tank being normal 98 fuel and the other 1/2 E10

    also when i take the top of the air cleaner off the readout goes towards the rich side al ittle and put it back on it goes back to the leaner side but still within the normal range
    3 x '78 604 SL

    1 x 2018 3008

    1 x 2000 Citroen XM,

    1 x '98 306 GTi6 sadly sold

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0

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    Quote Originally Posted by pugrambo
    the only thing that has me baffled is that when i am on trailing throttle the read out reads rich
    With your foot off the throttle it should go to poor for a few seconds, then the light should go off completely. When you first start the engine and for the half minute or so it takes to warm up does it indicate rich or lean?

    Quote Originally Posted by pugrambo

    when i just touch the go pedal it comes back to normal running A/F and when i put my foot down going uphill it reads towards the rich side and when i floor it and open up the secondary throat on the carb it reads between rich and normal depending on the road speed so that from standing start it will read rich when flat but very quickly reads normal A/F and if foot kept flat starts to come back to rich again but by this time i have gone from 0-40-180km/h respectively
    This would be the expected behavior.

    Quote Originally Posted by pugrambo
    1/2 the fuel in the tank being normal 98 fuel and the other 1/2 E10
    The oxygen contained in the alcohol molecule of the E10 fools the sensor into thinking that there is more oxygen in the exhaust gases. Try using all E10 one time and all 98 RON another time and see if your readings are affected. My guess is that the difference is fairly small and since the sensor does not control an ECU of no consequence.

    Quote Originally Posted by pugrambo

    i also had the water injection going at the same time
    Water vapor would dilute the concentration of the other combustion gases but the effect on the readings depends on the amounts injected. Try it without injection and see if your readings are affected.

    Quote Originally Posted by pugrambo

    also when i take the top of the air cleaner off the readout goes towards the rich side al ittle and put it back on it goes back to the leaner side but still within the normal range
    This puzzles me a bit; I would expect that with less restricted air flow more oxygen would come in, combustion would be better, unused fuel would be lower and a leaner mixture would be indicated. Unless the unrestricted flow results in less vacuum and therefore less air going into the chambers.

    Thanos

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    Budding Architect ???? pugrambo's Avatar
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    i'll check what it does next time it is cold again

    i was sure it was reading rich which is normal when i first started it and the choke was on but i'll double check next time

    it all seems to be working correctly though but it had me baffled why when going downhill with my foot of it that it would read rich and then applying the slightest amount of pedal it would resume normal A/F readings

    i'll give it a run very shortly with a tank of pure 98 to see what readings i get then

    the water ratio is about 7-10%

    the beauty of it is that i can run 16deg advance without the poor thing pinging plus it is running a higher CR than standard as well

    she's not quite stock but it's nothing overboard either

    just a nice clean slightly modified engine that makes a very standard paintwork needing attn 604 go fairly well and attracts a few looks when she passes cars going uphills where normal 604's would be passed
    3 x '78 604 SL

    1 x 2018 3008

    1 x 2000 Citroen XM,

    1 x '98 306 GTi6 sadly sold

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0

  4. #4
    1000+ Posts Wildebeest's Avatar
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    Default Mixture monitor.

    Rambo,
    Are your problems associated with your Weber equipped V6 ?
    Some Webers such as the Cortina type are designed for auto or manual trans operation. The auto trans Weber has a device, a vac. operated diaphragm that prevents the throttle closing off and stalling the engine.
    The manual trans Weber doesn't have this because the drive is allowing the engine to turn preventing stalling.

    The Weber you are using may be the manual trans type that would allow the throttle to return to its stop too suddenly creating a rich condition on a trailing throttle?
    The above are my understandings, I''ll leave them wide open for comment.

    I believe the vacuum capsule connection to the throttle on the Solex TMIMA carb is for the above and also part of the emmission control ?

    Has the air cleaner got any vacuum controls ? These may be disturbing engine settings creating rich conditions when removed?

  5. #5
    Budding Architect ???? pugrambo's Avatar
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    the weber i have on the 604 is off a falcon

    there aren't any hoses connected to it other than fuel and vacuum advance the dissy

    there is a diaphragm there that is supposed to have a line to it but it is only for the fast idle when A/C is opperated

    the air cleaner also has nothing attached other than the PCB to the oil filler

    so basically this car is void of any add ons or pollution controls bar the PCB and charcoal canister
    3 x '78 604 SL

    1 x 2018 3008

    1 x 2000 Citroen XM,

    1 x '98 306 GTi6 sadly sold

    1 x secret project

    1 x '98 406 STDT troop carrier and i don't care if it stinks, i don't sniff it's arse Death by wank tank

    1 x '99 406SV 5spd wagon, time to burn more fuel

    1 x 1994 605 SV3.0

  6. #6
    Fellow Frogger! AlsPug504's Avatar
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    The reason the mixture goes rich on coast down is because it is at the time of highest vacuum in the engine. It is at that time that the engine is most susceptable to miss firing. Miss fires allow unburnt petrol to escape through the exhaust. This is read as an HC emission. Manufacturers deliberately richen the mix to cure the miss fire problem. With carbies the greater vacuum pulls more mix through the idle jets.

    One reason a lot of maufactures dont use fuel cut off is because the cooling part of the mixture evaporates and any manifold loading gets pulled in during the fuel cut off period which it is to lean to fire. So it comes out as an emmission.

    Manufacturers also dont like the popping sound that can occur with some cutoffs.

    When you floor the throttle to re accelerate. The accerate pump function on both carbs and efi cuts in and squirts alot of juice in to the air to prevent a part throttle miss. Which is a quirk of part thottle airflow. The mixture then leans off over time (due to evaporation) so would come back to seeming normal A/F but as more power is required more fuel is nessary hence the re richening of the mixture.

    The remedy is to rich coast down is to completly vaporise the fuel this stops the emmission problem, popping sound, engine loading, and stops the carby draining your tank and wallet.

    Als
    Last edited by AlsPug504; 3rd December 2005 at 10:25 PM.

  7. #7
    1000+ Posts PeterT's Avatar
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    Those kits are ok for seeing if you're around 14.7:1, but they won't read a full power mixture (<13:1). For that you need a wideband sensor and associated electronics. Adrian Wuillemin has a very nice M&W Uego which gives very fast and accurate readings. However, you can also buy a locally made kit:
    http://wbo2.com/default.htm

    '92 205 Mi16
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  8. #8
    Gus
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    Quote Originally Posted by Thanos
    The oxygen contained in the alcohol molecule of the E10 fools the sensor into thinking that there is more oxygen in the exhaust gases.
    Quote Originally Posted by Thanos
    Water vapor would dilute the concentration of the other combustion gases but the effect on the readings depends on the amounts injected.
    This is something I've been wondering about for a while (water/alcohol injection and O2 sensors), although I haven't done a lot of reading about it.

    I would imagine, although I know very little about it, that the oxygen contained in either ethanol or water molecules can be present during combustion in one of two states:

    1 - Integral to the molecule
    2 - Cracked from the molecule during the combustion process and present as an O2 ion

    I figure if that (1) should have no effect on the oxygen sensor, but (2) would have a big effect. However, (2) - in cases where there is still fuel in the system - should combust anyway, which means that if there is excess O2 ions, regardless of where they are from, there is insufficient fuel (or bad combustion of one sort or another) as well.

    (Of course, some of the water/ethanol might crack in the exhaust pipe, which means you can have a "lean" reading and still have stochiometric combustion.)

    Sorry if this seems to be a hijack of the thread, and especially sorry if my dodgy half-remembered chemistry is wrong.

    (I'm mostly going off http://www.ngkspark.com.au/pages/tec...sors_index.htm for how an oxygen sensor works. Maybe someone can explain this further, too.)

  9. #9
    Fellow Frogger! AlsPug504's Avatar
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    Quote Originally Posted by Gus
    :This is something I've been wondering about for a while (water/alcohol injection and O2 sensors), although I haven't done a lot of reading about it.

    I would imagine, although I know very little about it, that the oxygen contained in either ethanol or water molecules can be present during combustion in one of two states:

    1 - Integral to the molecule
    2 - Cracked from the molecule during the combustion process and present as an O2 ion

    I figure if that (1) should have no effect on the oxygen sensor, but (2) would have a big effect. However, (2) - in cases where there is still fuel in the system - should combust anyway, which means that if there is excess O2 ions, regardless of where they are from, there is insufficient fuel (or bad combustion of one sort or another) as well.

    (Of course, some of the water/ethanol might crack in the exhaust pipe, which means you can have a "lean" reading and still have stochiometric combustion.)

    That is partly true. However, excess oxygen ions exist regardless of exess fuel. The A/F ratio 14.7:1 is said to be "perfect".

    Consider that if this were true the oxygen sensor would be unable to read richer ie 13.0:1 mixtures due to the absents of oxygen Ions.

    The oxygen sensor is really just a fancy electrical charge pump. The AFR meter is just an eleborate voltmeter. The air fuel ratios are infered from the reading you get.

    All the oxygen sensor reads is the burnt mixture.

    For the most part the afr 14.7:1 is a pollution compromise. By flooding the engine with liquid fuel the vaporisation of the excess quenches the flame so as to keep tempratures to 1150 degrees C

    The reason this effect pollution is that the amount of Oxides of nitrogen and carbon dioxide produced are as a direct result of temprature.

    This will also effect the oxygen sensor. If the average temprature is lowered so to is the formation CO2 NO2. Hence: more free oxygen ions become available when the temprature drops. And less emmissions occur.

    Your sensor would infere that the mixture is lean. When in reality the combustion efficiency has improved. While the true mixture ratio would remain unchanged. This also is partly why lambda 1 moves in ratio depending on the fuel you use. Unleaded for example is 14.7:1 the same mark with gas is 15:0:1 methanol is 6.0:1 diesal is 14.5:1.

    The Oxygen sensor really is just a tool. Its use needs to be set in the context of other instuments and a tuner who knows there inference to make tuning sucessful.

    Als
    Last edited by AlsPug504; 5th December 2005 at 07:12 PM.

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