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Thread: DIY LPG Tuning

  1. #1
    Nerd Extraordinaire denmaster's Avatar
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    DIY LPG Tuning

    Hi,

    Disclaimer: I know nothing about LPG.

    The problems I have:
    1) doesn't start consistently, particularly when its hot.
    2) doesn't have any power above 3000rpm
    3) stumbles when I nail the throttle

    The kit is a GNGAS Argentinian conversion kit.

    I have three bits which look adjustable:
    1) a flat-screwdriver adjustable thingo in the line going to the mixer
    2) a flat-screwdriver adjustable thingo in the reducer
    3) a finger adjustable adjustable thingo in the reducer

    What would each one do?
    adjusting (1) seems to do the most, (2) and (3) don't appear to do much...
    What AFR should I be targeting on a wideband
    - when idling
    - when cruising
    - when nailing it
    - during cold start
    - during hot start

    Patience and help MUCH appreciated.

    Thanks,
    --lg

  2. #2
    Nerd Extraordinaire denmaster's Avatar
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    This is a pic of the reducer:


    The adjustable bits are those just above the blue label.

    What do they do???

    --lg
    Last edited by denmaster; 17-04-06 at 04:27 PM.

  3. #3
    It's cause I is black. carazy's Avatar
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    dude... It's like $20 to get a car's LPG tuned.. just drive it to a LPG shop and leave it with them for an hour.
    Unless you have an o2 sensor your guessing.

  4. #4
    dangerous fugitive
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    Are you really in KL? If you are local, I'm sure more than a few people can help.

    Any chance you (or anyone) could email me the pics - I can't seem to get it to load . Or even better get me a couple of underbonnet pics.

    Very basically the 'big' screw/tap in the big low pressure feed line doing toward the throttlebody/carb (whichever you have) is the high speed a/f adjustment. If you are running a simple convertor and complex mixer, it might actually be part of the mixer. But I think you are (sight unseen) running an amos ring and complex convertor.

    There can be one or two screws on the convertor (depending on the specific model) one of them is the idle a/f mixture adjustment, the other is usually termed a 'sensitivity' adjustment. Basically it will help to trim the a/f mixture in the range between idle and high/wide open throttle/full power by altering how far it can pull on the diahphragm (some even run a dual diaphragm so it alters when higher speed enrichment comes in)

    TO adjust the idle is fairly easy. It will _usually_ be the smaller of two screw/bolts on the convertor. To pick which is simple enough - look at where it is now, and remember it. With the car warm (normally you'd actually adjust it cold, but for figuring out which is which, drive it around the block and warm it up a little) and idling if you turn the idle a/f mixture screw, you would be lucky to get more than 1/4-1/2 turn tops before it started to get quite rough in either direction.

    You _can_ adjust it for best idle (if it's an auto, adjust it in drive, with the handbrake on, and preferably with someone in there ready to put their foot on the brake just in case) as is and be done with it. But what I prefer to do (since there's stuff all load at idle) is to temporarily increase the idle speed around 200rpm. Either get a friend to extremely lightly push the accelerator pedal, or better yet use the idle speed screw on the throttlebody/carb if it exists.

    What you often find with lpg is that when it idles perfectly, it'll have an annoying rough running, just off idle, as you are slowly creeping out of a parking space or similar. Pain in the arse it is. So instead, after finding the perfect 'idle' in drive, then crack the throttle open than minute amount, and _readjust_ the idle a/f mixture till it smoothens up. Of the two, it's _far_ more important to have it smooth at that point than idling. Once you've done that adjust the idle rpm back down (or lift off the acc pedal). It will almost always still run perfectly acceptably. If it doesn't remember which way you adjusted it when you went from idle to that 200rpm higher spot, and turn the idle mixture half way between the two adjustments. You usually get most of the smoothness in both situations then.

    To adjust the wide open throttle/full power mixture, ideally you screw it in till the car starts losing power up hills (find a steep hill you can drive it up at full throttle). then screw it out 1/4-1/2 a turn at a time and retest. You'll find it gradually picks up power with each turn. When you get to a point where the last test was no improvement, turn it back in 1/8th of a turn, and leave it. Unlike a petrol car, running much richer than stoich won't make more power on lpg (as generally the power comes from the fuel evaporation leading to a slightly cooler/denser intake charge) it just wastes gas, so you aren't risking anything doing it this way.

    Another thing - some lpg fitters (for god only knows what reason) put a colder thermostat in cars they convert to lpg. It's a _very_ flawed idea. the convertors are designed to run at 195F and any other thermostat just has them belching out a richer mixture, across the whole rpm range, and wastes gas for no benefit.

    I haven't mentioned the sensitivity adjustment, because I'm hoping it is at least close to the mark. If you really want to stuff around with it, I can't describe a decent quick method to getting it right (other than with an ego sensor) but generally would suggest trying adjusting the idle first, then the high speed adjustment above, and from there, trying turning it 1/2 a turn in (which might require a slight tweak of the idle mixture to clean it up again, but often not, that generally happens if the setup is being used on an engine too big for the lpg gear - which happens a little more on stuff like big ford/holden 6s and possibly some japanese larger 6s) And see how it responds. You'll generally notice the difference gained by the sensitivity will come in the form of throttle response and general engine output at moderately low rpms and 1/2 throttle or a little more.

    Other than that, it often helps to run the same type of spark plugs as is normally used on that car (don't run colder heat range plugs) and to close the gaps by 0.005" (5 thousandths of an inch, or 0.127mm or 0.13mm to round off) vs the factory recommended gap for petrol. It'd take a mammoth post to fully explain why that works, just trust me it does.

    Other than that, make sure the air cleaner isn't clogged, and just as importantly make sure it does have one fitted, and there's no hoses or fittings that have come off and are letting unfiltered air in there. the very very slight restriction of an air filter actually makes it much more accurate to tune/adjust the lpg and get a conistent performance from it. Without an air filter, it can often be hard to get the bloody thing to idle at all. Much in the same vein, if the amos ring isn't sealed onto the throttle body (or carb) well then leaks below it will massively throw out it's fuel metering producing the sort of situation you are experiencing.

    this is all assuming it's setup like that, and that there isn't a module in there that's designed to trim the lpg a/f ratio from the ego sensor. They _do_ work well, and return decent enough economy, but most people I have spoken to suggest that they are slower to respond, and make the engine feel somewhat sluggish.
    John McKenzie

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    Religion flies people into buildings.

  5. #5
    dangerous fugitive
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    I tried http://www.gngas.cn/hk/knowledge.htm as well, but couldn't find a page in English, so it might not be the same company. At one time I could read chinese ok (simplified at least) but that's been decades, plus brain damage, plus I never exactly had opportunity or cause to learn the various words for technical descriptions etc (or put another way, I could probably get around in China as a tourist without speaking English, at least in parts of the country where they speak mandarin, but wouldn't be able to program a VCR using the instructions in Chinese. I might have missed the character for 'english' (well the two characters) on the page - anyone?

    Interestingly (I hope) there's what I believe to be a translation error on that page. I'm hopeful they actually meant to use the word 'conservation' not consecration.
    John McKenzie

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    Religion flies people into buildings.

  6. #6
    Nerd Extraordinaire denmaster's Avatar
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    dammit - lost my big post - grrr.
    try 2 (in notepad )

    jmac,
    You are a legend. That was a monster post. The website is http://www.gngas.com.ar

    The car is a carburetted petrol Pajero, 2555cc. It is a manual.

    I have had a fondle of the tuning over lunch, and adjusted the main low pressure line going to the mixer. This made the car run much smoother, but gas consumption seems to have suffered a little (75km trek over lunch, managed to finish off 7-8 liters)

    I have tried adjusting both of the adjustable bits on the converter, but they don't appear to be doing anything.

    The car is extremely gutless up top now, so I have goofed something somewhere...

    So far I have used the highly (un)scientific way of having a little notebook with the various adjusting bits drawn as little clocks, and taking notes about the drivability. It is VERY irritating that the tune appears to change as the tank gets emptier, so I keep having to visit the servo to pump it up to full so that I can eliminate that variable.

    I have a WB02 that I use to tune my Microtech, so I will get that hooked up soon. Unfortunately the car has a curved tailpipe, and the exhaust probe that I have won't secure well, so something will have to be fabbed up.

    What AFR's should I be targetting? On petrol it idles around 14, and when nailing low 13s. I have googled and it appears from the gasresearch website that the stoich point is 15.5. Can I apply direct fractions and assume that
    1) 13.0 X (15.5/14.7) = 13.7 is a good target when nailing it
    2) 14.0 X (15.5/14.7) = 14.8 is a good target when idle

    Thanks again for your help, it is MUCH appreciated.
    --lg

  7. #7
    Nerd Extraordinaire denmaster's Avatar
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    oh - yes, really in KL

    --lg

  8. #8
    dangerous fugitive
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    No worries about being from KL - a few guys here put all sorts of locations in their info, sometimes joking, sometimes not, so I had to ask - because if you were local, there's a few places I could recommend to take it to !

    I still can't get any pics to load from that page - any chance you could take a couple of underbonnet pictures?

    7-8 litres for 75km is actually bloody good for a larger vehicle. I think you on the right track there with the high speed adjustment. Another 'trick' you can do to tune the high speed is to put it in neutral and get someone to push the accelerator down until it's up around 4000rpm (assuming for for that the motor is redlined at 5500 or so. If it's redlined lower, put the revs up to around 75% of redline rpm. Get them to hold the accelerator pedal still, then quickly screw the big adjuster in or out (it might take a few turns in either direction) until it gets the highest rpms. It's not as good as the uphill testing, but it might help you if it's really problematic to be able to get a baseline right now, so you can actually 'do' the finer tuning.

    with regard to it running poorly, sight unseen, I'm going to suggest trying turning the sesitivity adjustment 2 turns anti-clockwise, resetting the idle and seeing if this makes a difference. Another way you could do it would be to screw it all the way in (not ridiculously tight, just hand tight) and try it. It'll possibly refuse to idle at all, or poorly at best. Re-check idle and high speed (the quick test above) then turn the sesitivity screw 1 full turn anticlockwise, then repeat, basically keep going 1 full turn anticlockwise till it's running well. Depending on how the screw attaches, there might be a locknut or a spring to hold the screw in place, don't back it out too far - 5-6 turns is probably the max (beyond that might be fine, but there's a chance it might drop out, and if you aren't super familiar with the internals (and on some it's 'fool proof' on others it might not be, and I've learnt that the hard way, as I've learnt most things!)

    Your description of the problem with the idle being ok with a full tank, but deteriorating as the tank gets near empty _very much_ sounds like a possible sealing problem between the amos ring and the carb, or the amos ring and the air cleaner. On some vehicles like this, the air filter is a long way away, and connected via a 'snorkel' from the top of the carb to the air filter case with a rubber hose, or sometimes plastic. These can be very heat sensitive, and often brittle after a fair few years. They can crack, causing the problem. further, if the car has backfired on lpg a few times, it can burst such items (very common on v6 commodores, which is why probably 90% of taxis here are ford inline 6s, not the commodore (it's due to the way the ignition is run, and the engine management can sometimes mistakenly think that it's flooded and it can start to either alter ignition timing, or produce multiple sparks to try and clear it. It can go far enough (due to how it feeds each cylinder, not quite individually, from the coil packs) that it will cause a spark in a cylinder where the intake valve is still open, and it ignites the gas in the cylinder _and_ the rest of it in the inlet manifold, blowing airboxes apart sometimes). If your's has backfired, it may have done something along these lines (even though the _cause_ of the backfire isn't quite the same as what causes it in the holden v6, the general 'results' can be much the same.

    the more I think about it, the more and more I think that this is going to be the root cause, and worse still, it'll keep interfering to the point that any adjustments to the lpg fuelling won't do what it 'should' do and end up driving you mad (and yes, I speak from experience on that one too!). If at all possible, beg borrow or steal (joke) a digital camera and get some pics of the engine bay. In particular the convertor, and the entire air filter assembly, and then also if possible a pic of the amos ring (on top of the carb) with the carb hat/snorkel temporarily removed so the hose(s) going into the amos ring, and the amos ring itself can be seen. If anything can possibly be seen, or looks suspicious, I'll edit the pictures, and post the edited ones with arrows showing the area of concern.

    And one last ignition related thing. If the ignition is borderline in output (I'm assuming it's a electronic ignition, but it could possibly be points) then it'll show up a hell of a lot more on lpg, _especially_ at idle. Whilst at the same time it can run perfectly on petrol. The reason is actually pretty simple. At idle, on petrol, with the throttle closed, there's stuff all airflow through the carb. But there's _heaps_ of vacuum in the manifold. The main fuel circuit won't work, but a tiny slot/hole is in the carb base, below the throttle plate. It's connected to the fuel bowl. Basically with the throttle closed, this tiny hole sees a lot of vacuum, and it can easily draw the amt of fuel required for idle through it. The high vacuum is 'really' lower pressure (than atmospheric) so it also means that it's easier to cause the petrol to vapourise, just like water will boil at a lower temperature than 100 when you go high above sea level where air is 'thinner' (or create a lower pressure in lab conditions). So idle supply for a petrol carb is 'easy'. On a dual fuel it's ok for petrol, but the lpg amos ring sits _above_ the throttle plates. That means at idle, there's almost zero airflow through the amos ring, and zero signal to get lpg flowing. So what the lpg setup does instead is the convertor actually has an idle circuit. It's 'powered' by the pressure of the lpg in the line (so to speak). When the car is idling, it pushes this tiny amount of lpg into the amos ring, where it 'falls' down into the carb and is drawn past the mostly closed throttle. It's a 'controlled bleed' and will provide the same amt of lpg, irrespective of engine rpm, as long as the throttle is closed. Which is why a carb can (to some extent) have no trouble at all going smoothly from idle to just off idle, responding to airflow (there's also a 'transition' or 'off idle' circuit in petrol carbs to help further). But for the lpg mixer, it supplys the same lpg regardless of engine rpm. Which means on an auto if you adjust the idle mixture in neutral, it will potentially be rough when in drive.

    Aside from that, the lpg and the air are nowhere near as well mixed together (only at idle). So basically a slightly subpar ignition will show up a lot sooner on lpg - as it has less ability to provide perfect mixtures at idle.

    It also means, that with no other changes, if the engine stalled, the mixer would keep bleeding in that lpg, flooding it (or worse, if the car was in a crash). which is why they have that 'little black box' module. It takes an input from the coil, to know when the engine is running, and if the spark stops being triggered, it'll shut off the lpg flow.

    When you first turn on the ignition, for 99% of these setups, it will engage the lpg solenoids (or just the primer, depending on which type) for about 1-2 seconds. This will give an intial 'shot' of lpg, kinda like pumping the pedal once or twice before starting on a petrol/carb setup. This helps tremendously with cold starts after the engine has been sitting for some time. But if you've 'just' switched it off, there's still enough lpg in the intake to start as is. This extra 2 seconds can come close to flooding it. SO if you find it starts ok in the morning, but not after a trip, where you turn it off and restart a few minutes later, there's two things. Firstly - to start on lpg, push the pedal down around 1 inch (or a touch less) then turn the starter, and it should start instantly. Obviously as soon as it fires, ease off the pedal so it doesn't rev too high. Secondly - if it's hard to restart you can do two things. Don't turn the key all the way off, as then it'll reprime the next time it's turned on, flooding it even more. the 'quick n easy' thing (if the initial 1" acc hold didn't work) is to push the accelerator to the floor, and turn the key on the starter till it fires, then back off the accelerator. If that still doesn't work, switch the lpg/petrol switch into the middle (i.e. both off, no petrol no lpg) and foot to the floor and start it. as soon as it 'catches' you need to do two things, 1. lift off the pedal (leave it down around 1cm, so not _all_ the way off) 2. click the switch back onto lpg. with that switch off, there's no new lpg coming in, so it clears/cleans and starts. Obviously this is a lot easier if the lpg/petrol selection switch is in a place where you can switch it with one hand whilst turning the key in the other.

    That should help, but in any case, if there's a chance the ignition isn't up to par (esp if it's points) then replace those items that are suspect. There's probably a million writeups as to how to check/address any ignition issues, and this post is already to the point some people will fall asleep reading it

    Actually here's one last thing. A friend of mine has a 4wd on lpg. It very very occasionally backfires. Due to where he often drives, it's not practical for him to risk blowing out the airfilter and it's connections, as it would leave him stranded. So he's drilled a hole in the carb hat/snorkel (whilst off the engine) and filed/sanded it to get rid of any sharp angles. he then literally sticks a wine cork (with a little electrical tape around it to help it go in without tearing, and to help wedge it in tighter. As long as the cork is tapered (slighly triangle shaped) it can't get sucked all the way in. And if it backfires, it just blows the cork out, and keeps the rest protected. He's got the cork on a string tied to something in the engine bay (I forget where, but it's unimportant) and also carries a spare in the glovebox just incase.

    As soon it's practical, get some engine bay pics, and I'm fairly sure (if none of the above helps) that it'll be solved satisfactorily.
    John McKenzie

    Science flies people to the moon.
    Religion flies people into buildings.

  9. #9
    Nerd Extraordinaire denmaster's Avatar
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    Re the ignition system: I've done everything you suggested including change the ignition coil, as well as the spark plug leads, and regapped the plugs. It has made a hugh difference to how smooth the engine runs, but not to the power output.

    I have discovered how irritating the little stumble that you said would occur is, and have not managed to get rid of it yet. It happens with the air conditioning off, and I ease off the clutch, or with the air conditioning on and in neutral, it feels like its going to stall. Its annoying the hell out of me, and I want to get that fixed.

    In line with what you said yesterday about the carb needing some restriction, I tried something really weird, I actually blocked off the air intake snorkel leading to the carb, trying to see if I could find (listen) for any leaks, and the idle instantly became smoother. What gives with that? The mixer is of a poor design and isn't mixing/atomising the LPG well with the incoming air? Maybe those hiclone/cyclone things have a use after all :LOL:

    Thanks muchly for all the help - this is slowly making sense to me. I think I have the low pressure thing sorted out, I'm just struggling with the full throttle transitions, it feels as though the sparks being blown out or something...

    On the upside, it started on the gas really well this morning...

    Anyway you're 100% right on the "can't start immediately because of the LPG priming" point. I find if I leave it 10-15seconds it'll start again easily, but not immediately. Unfortunately this combined with the off-idle stumble with the air conditioning on is just enough time for the people behind me as I'm heading out of the car park to get irritated and begin tooting their horns. (as I would probably do, had I not known the pains of LPG tuning..)

    Any ideas about the lambda values?
    --lg

  10. #10
    Nerd Extraordinaire denmaster's Avatar
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    Update - its still a bastard. Yesterday I let the gas run down to the end of the tank, and it ran like crap. Taking off everything to find that mysterious leak you mentioned...

    --lg

  11. #11
    dangerous fugitive
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    The other thing aside from air leaks in general can come about if there's a hell of a lot of distance between the throttle plate and the amos ring. On most they put the ring right on top of the carb, but I have seen some that place them in the air cleaner plumbing (for 4wds with remote air cleaners). That leaves so much 'dead space' between where the lpg is being introduced at the amos ring, and the throttle plate, that there's a hell of an inconsistent and poorly mixed intake charge getting in there under idle conditions.

    AFAIK at least one of the wb ego kits out there can automatically plot the a/f ratio vs rpm and can convert the lambda value from stoich to what a/f ratio that actually is be it for lpg or gasoline based fuels (for the 'stoich' reading on both lpg and petrol, the actual lambda value will be the same).

    the main difference is that with lpg, there's not a huge advantage (in fact stuff all) in going much beyond stoich even for WOT. It has no added cooling effect. At higher flows, the lpg _will indeed_ mix very well, and have better mixture distribution and mixture atomisation (that's actually the wrong use of the term, but you get my meaning) so you don't have the same extent of lean and rich pockets within the cylinder, so you only need to got a little richer than stoich to get good results.

    generally, you'll probably need to go a little extra rich at idle to get the most out of it, simply because it won't be mixed in as well.

    If I was in your shoes right now, i'd be looking at what the ego sensor is reading at full throttle from 2000rpm through to redline, and then another set of runs, staying away from full throttle, only using 2/3 throttle, and constantly going up through the gears, not topping 4000rpm, That should give you a handle on which way and how far the 'high speed/flow' screw needs to be adjusted, and then the sensitivity respectively. I suspect you'd likely end up between 0.9 and 1.0 for idle and full power, probably closer to the 0.9, and doubtful below it (but I'd still do back to back tests, and if it did show more power, I'd go with that).

    Based on what you've said so far, I'm thinking it'd be worth (if the ego isn't hooked up) trying the high speed a further 2 full turns anticlockwise (or to full open) and see what that does.

    It's very hard to make a definitive call on it, I can tell you that I've seen a bunch of lpg setups on friends cars that were atrociously tuned before I took a look at them. One in particular was a big 4wd. I borrowed it to help a friend towing another broken down 4wd on that had broken down. We went and picked up the running 4wd and got a big trailer, and it could barely pull the trailer at all. I got under the bonnet and adjusted the high speed a/f mix as well as sorted a couple of air cleaner issues. Then we picked up the broken down 4wd. The difference this made was so much that it actually went quicker _with_ the broken down 4wd on the trailer and the properly adjusted lpg mixture, than it did previously, just pulling the empty trailer.

    For it to be making such a huge difference from full to empty lpg tank in how it runs, it must have something going on - either the convertor isn't able to regulate the lpg flow across the spectrum of tank pressures (which is rare if new, and they don't vary as much as people might think) or there's an air leak, or huge air gap (as mentioned above) between amos ring and throttle plate/carby.

    I did touch on the fact either here or in another recent thread, that unfortunately lpg systems aren't all created equal. There seems to be some considerable differences in quality control with some brands. for any given brand some have no dramas ever, but the few who get a dodgy or below par unit can have no end of trouble. I don't think that this is the case with this one (at least not at this point in time) but I wouldn't 100% rule it out. If it was suspect, it'd take some experienced eyes to find it. But generally you'd be looking for things including (if you dismantled one) sticking needle/tapered seat valves, torn or ballooned/swelled diaphragms, corrosion buildup in water passages, bent or damaged springs.

    Hell there's even a tiny amount of lubricant (alleged) in lpg. I've seen some converters literally full of sludge from a bad batch or two of lpg (probably several over the course of a year or more) that went fine when washed out and refitted. But I couldn't guarantee it, nor would I be super confident I could pick that from a picture. Their actual inner workings are quite simple in principle, and although each brand differs in specific design, they all more or less are the same. But it requires a close look, and sometimes the need to move/lever/actuate the various parts to check they can do what they are supposed to.

    If all else fails, there'd likely be someone who could help, perhaps a local lpg fitter. I can't speak for overseas, but believe it or not, often the places that do taxis are actually chosen for those who can get their systems to work and run reliably and economically, even though most would assume that taxi operators would just go to whoever is cheapest.

    I just had another thought - when the engine is warm, put your hand lightly on the convertor - it should be hot - as warm as the top of the radiator. maybe even a touch warmer. If it's just luke warm, or worse yet, almost cold, there's insufficient water flow through it, and it's belching out a lot of lpg. I don't think this is happening because it would use more lpg, but it might be borderline, and getting it to be responsive etc won't work without it being up to temp. If it's not, look for kinked hoses (on mid 80s fords, they tend to leak oil, and the hoses go really soft, and then the bend and kink, and can't totally heat the convertor up to run ideally. Sometimes they idle fine and ice up at higher rpms, sometimes quite the opposite (demand is higher with higher rpm, but sometimes the water pump can manage to push more water through the hoses at higher rpms, so either is possible)
    John McKenzie

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  12. #12
    Nerd Extraordinaire denmaster's Avatar
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    G'day,

    Did some major tinkering today.

    FYI, the setup I have is like this: The AMOS ring sits right on top of the carby, and the air filter housing directly on top of the AMOS ring.

    There was a 2mm gap between the amos ring and the carby... An o-ring was used to seal that right up, and I tigtened the bolt securing the air filter housing down as well.

    Seeing as how restricting the air seemed to be a good idea, following on the way many local taxi's are set up here, I restricted the intake to the air filter housing a bit with some carefully shaped plastic. This worked really well, the idle was MUCH better with the added restriction.

    The other thing I did was the stick the wide-band in there, and tune the restrictor in the main line going from the reducer to the AMOS ring. This worked wonders, and the car is much more drivable, significantly more power. I found it smoothest and most responsive with a lambda of around 0.8-0.9. As it nears 1 and leaner, it runs weirdly and the engine feels very choked.

    I have managed to get rid of the little stumble off idle with some messing with the idle screw on the petrol carb.

    The most irritating problem now is that the car stumbles when I MASH the pedal. This is needless to say very irritating, for example when you want to quickly get into a gap in traffic. Fortunately its a stick shift so you can actually drive around the irritating problem by half-clutching a little.

    Anyway, what I seem to have learnt is:
    1) Adjusting _any- screw on the reducer doesn't do anything. Grr.
    2) A little restriction on the air intake is good, makes the idle smoother
    3) The main line to the AMOS ring/mixer is the trick to making good power
    4) Need to adjust the idle screw on the carb to compensate for the changes in the main line to the AMOS ring/mixer.
    5) Spark gap doesn't seem to do too much.

    Any hints for how to solve the stumble when I mash the pedal?

    --lg

  13. #13
    Surf's Up! bigmuz's Avatar
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    Just wanted to mention that this is possibly the best piece of data for diy lpg tuning in the real world ANYWHERE on the net.

    John Mac, you are a generous man with your knowledge and time. We appreciate it mate.
    Quote Originally Posted by Stix Zadinia
    2x Robbie Williams Tickets, Brisbane, Monday Night 22nd Sept, Row A Platinum
    Quote Originally Posted by Shifty
    Won't be much of a show now that he's dead.
    Quote Originally Posted by agentcrm
    ROBBIE Williams the singer not ROBIN Williams the recently deceased Actor & comedian

  14. #14
    2ofdem
    Guest
    Quote Originally Posted by bigmuz
    John Mac, you are a generous man with your knowledge and time. We appreciate it mate.
    agreed

  15. #15
    Registered User TurboRA28's Avatar
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    Can I dig up an old thread? I'm doing a bit of DIY LPG tuning.. Complex converter, simple mixture. Due to the car having no 02 sensor it was installed with an open loop system. I may get a new processor for closed loop though and chuck an 02 sensor in..

    Anyway, what i'm finding.. I can get cruise mixtures perfect by adjusting the valve in the low pressure line between converter and mixer. Using the wideband I am getting around 14.7 (freeway) - 15.5(around town) on cruise. But.. if I nail it, it doesn't richen up much.. Full throttle may see 14.4.. I would have expected this to be a bit richer?

    But not sure what adjustment I can make to keep the cruise mixtures where I have them, but allow richer for load/full throttle etc.

    Thanks
    Joel

  16. #16
    m o d e r a t o r Greg Rust's Avatar
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    Is this thing turbo, if so do you have the convertor refrenced to the positive side of the turbo?
    xw Falcon 351 3/4 race cam, check engine light on.

  17. #17
    Registered User TurboRA28's Avatar
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    Nah it's on a 80 series NA cruiser.

    Been playing heaps with this, but doesn't seem to matter what I do with the sensitivity adjustment or power valve thing, it always ends up a pretty steady mixture from idle to redline and everything inbetween. eg lambda 1 at cruise, maybe .98 at full song and 1.02 at a real light cruise. Bugger all change.

    If I open up the power valve I can get a richer mixture at full song, but then end up with a rich cruise also. Stupid thing.

  18. #18
    arboreal bukkake briney's Avatar
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    is it a huge drama to add an oxy sensor ? there are closed loop controllers which i've had some good success with. just get the full noise working then the cruise stuff is closed loop. probably even pinch a whole setup from a wrecker.
    I didn't choose the thug life.

  19. #19
    Registered User TurboRA28's Avatar
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    Yeah probably go down that path

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