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Thread: Fuel Mixtures

  1. #1
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    Default Fuel Mixtures

    Well looking at the plugs my mixture is really rich (foul & cause problems with every tank of fuel!)

    So i need to adjust the mixture accordingly...
    easy enough, find a little screw & twist it...

    but how much?

    Looks like i need to buy an EGO sensor & then hook up a kit to test the voltage...

    I assume i'll need to drill the exhaust to put it in?!?
    what sensor do i buy? (i'm sure there's not THAT many out there?)

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    Contented Peugeot Driver addo's Avatar
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    Hey Nate,

    That is a step in the right direction. I think you need a powered EGO sensor (three wire) from wht I'm told. Places like Summit Racing sell own brand gauges for displaying this info; also they're on Evilbay often enough. A friend of mine used a different gizmo (more expensive) to curve his carb fuelling and reported excellent results.

    I'll edit my post with the details and link in a few minutes. A different car, carb and country but air:fuel ratios don't care about that!

    OK, here's the info. Bill used an Innovate LM-1. Link to another Forum (slight redneck warning!).

    Cheers, Adam.
    Last edited by addo; 3rd February 2006 at 08:17 PM.

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    nate, do you a renault 5 turbo!?
    Take the long way home....

    - 306 gti6

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    When you start to play with turbos, it's very important that you have a fast acting sensor with an accurate display. The difference between a good and a melted piston is just a few seconds. Adrian Wuillemin has an M&W Eugo setup which is top shelf. The readout can be displayed on a laptop or a Palm, or fed into a programmable ECU. They were approx. $1000 but I believe they've come down a bit. Have a look at this other locally made product - http://techedge.com.au/vehicle/wbo2/. I've been considering making one myself. Autronic and Motec also make them.

    '92 205 Mi16
    '90 Mi16x4

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    Yeah the problem is its fouling the plugs MAJORLY (clean them every time i use the car!), so i need to adjust it...
    But its mechanical fuel & dizzy, so no computer!
    Just a screw i gotta find somewhere & wind it back a bit...

    will have a good look before i start tinkering.. hmm

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    IIRC, you said it had an upsized intercooler. If this has improved flow capacity (by reducing pressure drop through the IC), it could be part of your hassle. People often upsize the carb too, on a blow-through turbo car, using the reasoning applied to N/A vehicles. In fact, this is often counterproductive.

    There's probably four effective fuel circuits in your carb, going from idle to power valve open. It has to be managed so that one tapers out as the next comes on song. Also, because loaded conditions create different levels of manifold vacuum compared to the same throttle position stationary, it often needs dyno tuning to finesse these transitions.

    With the right gear, you'll be able to get pretty close on a DIY basis. Should be fun with the car in question, too!

    Cheers, Adam.

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    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by addo
    There's probably four effective fuel circuits in your carb,
    it's mechanical injection. Surely there's an expert on here?

    '92 205 Mi16
    '90 Mi16x4

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    It uses k-jetronic, yes?
    if so, there should be a mixture screw somewhere on the flap arm, accessable by removing a screw port (it adjusts the relationship of the fuel metering piston to the air measuring flap). The adjustment on my R26v6 is extremely sensitive, fractions of a turn in or out make a big difference. You need a very long allen key to adjust it, 3mm on the v6 (and a few others). One of the things with k-jet is that every part has to be spot on, otherwise the all sorts of problems turn up. The Probst fuel injection book is a good place to start.

    Farmerdave

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    yeppas Bosch-k...
    Been doing a lot of research!

    I've got a figure of 1-1.5% CO at 1200rpm from the service manual, but that doesnt help me with an O2 sensor reading!

    The next thing i'll have to do is work out the placement of the sensor too, was told to put it before the turbo, but the link above says after... hmmm

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    Gus
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    Part of the problem is that even if the K-Jet system is spot on at idle, if the fuel regulator (the afm plate pushes a piston in and out of this to increase and decrease fuel flow) bores/piston are worn/corroded, or the spring in the afm is tired then you can get rich/lean spots throughout the rev range. I used to have a 505 STI which idled fine but ran too rich off idle. Eventually the piston in the regulator jammed totally and the thing was fuelling full rich even at idle (unburnt fuel was pouring out of the engine pipe gasket, and the thing kept running!) Anyway, a new regulator got it running much better but may/may not be an option.

    IMHO, a good wbo2 sensor is a very good idea. Good luck.

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    Update - mixture is fine!
    after giving it a bootfull yesterday (plugs will foul unless its hammered constantly), plugs are good...

    So back to the old ignition system! (ALWAYS the issue!)

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    Seems to be a partial throttle spluttering issue...

    Just cleaned up some wiring contacts... a little smoother...
    but still lumpy on partial throttle...

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    Quote Originally Posted by nate

    So back to the old ignition system! (ALWAYS the issue!)
    A good CDI unit will help to clean up any extra fuel, possibly solving your part throttle responsive.

    '92 205 Mi16
    '90 Mi16x4

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    yeah i'll grab a CDI kit from Jaycar & see how it goes...

    I'll also grab some Magnecor ignition leads (current ones are dodgy & some are reading 12ohms!), they're all the wrong lengths etc...

    Maybe also a new coil... hmmmm

  15. #15
    farmerdave
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    Quote Originally Posted by nate
    Seems to be a partial throttle spluttering issue...

    Just cleaned up some wiring contacts... a little smoother...
    but still lumpy on partial throttle...
    Vacuum leaks?

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    no leaks...

    Seems to be the ignition!

    Got a new set of Magencor 8mm leads... mmmmm
    now to adjust the timing... the manual (in French) states 10deg BTDC at 1050rpm, does that sound correct?

    I've been doing it by 'feel' on the road... getting pretty good at it too! LOL

    Mite have another leak in the zorst manifold, time to get it machined i think, brand new gasket & its leaking again...

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