Grand Cherokee with nasty mpg on LPG

[Mdizzal]

Well it was still at 80 but after a 2 minuite drive around the corner and back it dropped went down to 74, what does this mead exactly??

Thanks
Mark

[Tubbs]

If the default is dropping then its a bit rich and the stepper is opening less to keep it all on check. So do you have two bars on the screen ? A blue and a red one ? How big are they ?
And also how have you connected up the lambda wire, we all generally just sample it with the purple. The grey is for a simulated wave back to the ECU. You dont really need to do that on a jeep. But if you have connected them the wrong way round then you could be making yourself a problem.

[Gilbertd]

It means that the Millenium is doing it's job. It learns the average opening and sets that as the default. The fact that it is going down means that the actuator was opening too wide before at 80 and it is now learning where it wants to be. This would explain your lack of economy. On the configuration page there is a box marked Open Loop Duration or something similar (usually set at 20 seconds or thereabouts). This is the length of time it ignores the lambda sensor signal when first started to allow the lambda sensor time to heat up and start giving an output, during this time it will run at the default.

I usually set the actuator limits at something like idle +20, -10, out of idle, +40, -20. Ideally you want to drive the car (or get someone else to) and watch what it is doing on the laptop under different driving conditions. A variation of 10 or so over all conditions is fine, if it varies more than that then it needs more than just the controller programming. For instance, when I first got my LSE (which has a Lovato system but it works just the same) at anything over half throttle the lambda signal would drop to zero and the actuator would shoot up to maximum open as the vaporiser was shot and couldn't supply enough gas.

The other thing to look out for is a glitch as you come off idle. Your vaporiser has 2 adjusters, one that sets how far below atmospheric pressure the gas supply is and one that allows a dribble of gas through all the time to allow the car to idle. Under normal running the gas is drawn in by the intake 'suck' generated in the engine air intake but at idle there may not be enough suck so it would die on you. To get round this, the idle valve allows a small amount of gas to dribble out to supply sufficient for it to idle on. Obviously this isn't enough for anything over idle so you have a transition between 'dribbled' gas and 'sucked' gas. If the actuator climbs as you initially open the throttle and then drops back, the 'suck' setting is too high and it is trying to run on the 'dribble' gas. It isn't too critical, but if you want to set it up absolutely spot on, that's the way to do it. Mind you, I used to own a car with two twin choke Webers and could spend hours getting them absolutely perfect where most people were quite happy with close enough.

The 0.8-4v is indeed what you would expect to see on a standard 0-5v TPS. This will allow you to set a lower actuator opening while on the over-run (the cut off setting). You'll need to play around but I would suggest something like 45 or 50 with a threshold of 1,500 rpm. If it almost dies after you blip the throttle, increase the threshold, if the power comes in with a wallop if you go back on the throttle while coasting down a hill, increase the actuator setting.

[Mdizzal]

Hi tubbs

The red one is about 2.5 inch and the blue is almost full size of my laptop screen, been on a bit of a longer drive and it was often down to 72. I wired the lambda by splitting the signal wire and then putting the purple to the lambda and the grey to the cars ecu if you get what I mean (it showed it like that on the leonardo website when I downloaded the technical instructions.

Thanks

[Gilbertd]

It does and it shouldn't cause a problem on your car but it can on some. The simulated signal supplied to the petrol ECU on the grey wire can sometimes upset the petrol ECU so it runs like a dog after you've run out of gas and try to go back to petrol. The accepted, and better, alternative is to not break the signal wire but simply Tee the purple wire onto it and leave the grey one disconnected. That way both controllers see the actual lambda signal and not a simulated one.

[Mdizzal]

Hi Gilbertd I see whAt your saying but I just spent half an hour splitting and crimping and taping but if it causes a problem the. I'll join the lambda back with the ecu and just tee into it with my purple wire. I will have a play with th settings as I noticed that when I'm accelerating up a hill for example the actuator is almost always down in the 60's range but when coasting down a hill with no acceleration the actuator seems to be in the mid 90's and if I'm sat still at idle it's around 80' my average is already about 73 but it seems the coasting is coasting me money (lol) so it it were possible to have less gas going in when coasting down hill then it should improve my default of 73 ??? (I could be wrong). It's funny because I've just returned from the LPG garage where ive now filled up who supply gas and also do conversions and I mentioned to him about the lambda not been connected and he said "there's no need to connect them at all" but according to my software now showing 73 that must be clear evidence that there is a need to connect your lambda

Thanks
Mark

[Gilbertd]

There's no need to connect the lambda on a multipoint as it slaves off the petrol ECU. On a single point the petrol ECU is doing nothing, all the controlling is done by the Millenium and the only input it has is the lambda sensor. Rather than being not needed, it is the only thing that is most definitely needed.

On the overrun, the mixture is going weak (because the throttle is closed so it is sucking less gas in). The lambda sees it as weak so the controller opens up the actuator to compensate. This isn't necessary, most modern petrol injection systems actually switch the injectors off on the overrun so there is no fuel going in at all! If you go to Optional Configuration and select the Cut Off tab, you can set a fixed actuator opening when the throttle is closed but the revs are above a certain amount. Start with a setting of 45 or 50 and a rev threshold of 1,500 rpm. You can set it at 0 and shut the gas off completely but this can cause problems as the actuator has got to open up to the default as soon as the revs hit the threshold and before the engine dies on you. You must have the TPS wire connected so that it knows the throttle is closed (or it will cut off all the time!). Under the TPS tab is a figure for TPS Hysteresis which you may need to play with otherwise it will think the throttle is closed at very small throttle openings. This will display itself as the revs increasing until you hit the threshold and it will then cut and start to hunt around that rev setting.

If the default at idle is higher than under normal running, you may need to give the idle bleed screw on the vaporiser a slight (and I mean slight) tweak open to get it the same. This will increase the amount of gas dribbled in but will stop the actuator from having to thrash up and down all the time, it will probably end up sitting almost steady under all conditions.

[Mdizzal]

Okay so tomorrow I will have a good old play around with it, just so I can get the full jist of how these systems work does the vapouriser produce only a certain amount of gas based on how much the inlet sucks ?? Or does it produce a certain amount under pressure and then the actuator will let the correct amount through?

Thanks again
Mark

[Gilbertd]

The vaporiser turns liquid LPG into a vapour and then holds it at a set pressure. This pressure is fractionally below atmospheric pressure so without any suck, no gas flows (except for that allowed to flow through the idle bleed circuit, the dribble). The amount that flows depends on the amount of suck but it can't be regulated sufficiently, so the actuator does that bit. In theory, if you could match the mixer to your engine perfectly, then the exact amount of gas would be sucked in, but the mixer would only be right at any given revs and load. It can be done but is only done on things like generator sets which run at a constant speed. The mixer is chosen to suck more gas in than required and the actuator then regulates the flow.

[Mdizzal]

Super Gilbert that gives me a clear idea of how it works and I can't thank you enough for helping me with this I do like to educate myself and at the same time sorting my jeep out, I do think 10 mpg is a bit poor even on a v8 jeep so hopefully it should start to improve now after this and a bit of setting tweekage, the jeep it's self does seem to run great on gas but it is a bit hesitant and jumpy with bad idle on petrol but that seems to all go away if I keep it on petrol for a while (which I don't cos im to tight)

Thanks
Mark

[Gilbertd]

the jeep it's self does seem to run great on gas but it is a bit hesitant and jumpy with bad idle on petrol but that seems to all go away if I keep it on petrol for a while (which I don't cos im to tight)

That is due to the LPG system being set wrong. With the default set and locked at 80, which we have now established was too rich, the petrol system has been trying to compensate. It doesn't know that you've switched the petrol injectors off and are squirting LPG in there instead, all it knows is that the lambda sensor is telling it that the mixture is too rich. So it reduces the petrol injector pulse duration to correct it, but nothing changes, so it reduces it a bit more. Still nothing changes so it keeps on reducing the injector pulse duration. Then when you go to run on petrol, it is running stupidly weak until it corrects again by increasing the petrol injector pulse duration back to where it needs to be. Some cars have a petrol ECU that is intelligent enough to realise that something isn't right and if it has to adjust the mixture by more than a certain amount, it brings the MIL on to show you that it isn't happy.

[Mdizzal]

Are you saying my jeep is somewhat of a thick yank? Hahah yeah I agree with you they are quite a basic machine and considering there a 4.7v8 it's shocking that it don't even produce as much bhp as my partners audi 1.8T lol. Hope you have a nice weekend and hopefully the weather will hold out too

Thanks again
Mark

[Tubbs]

Ok now richard has given you all the background. What you are looking to acheive is this :-
You want the actuator to be moving the lambda about 10 or so steps under the default. Idle is the blue bar. It shows how far the stepper can open. So say 20 steps over and under the default arrow.
You can tell the ecu to open the stepper more or less depending what figures you input. Idle opening steps over and under default. But always remember to press enter.
The red bar is out of idle. Same here. But you dont want it climbing all the way to the top of the screen in order to get the lambda to move.
So lets say your default is 70. You want to see lambda movement, at idle maybe 65 or 60. This can be adjusted on the idle (air bypass) screw.
Now you have TPS the unit knows when its in or out of idle. When you touch the throttle, TPS voltage changes and the stepper will always jump to the default. You always want the stepper to be opening and not closing. So again out of idle you want to see lambda movement under the defalt. The main mix will hopefully acheive this. Just make sure you make a reference point before you start adjusting things. And only a bit at a time. Its not loads and loads of turns. More like 1/4 or 1/2 a turn at a time really.
Oh and if you think about it, just cut the grey wire and splice it into the purple leaving the grey coming out of the ecu un connected and terminated if its easier, you can do that at the unit save grovelling around trying to get to the lambda again. Im sure its also under the plastic cover that the injector loom lives in.

[Mdizzal]

Cheers tubbs I'm gonna have a go at that lot today I'll let you know how I get on and good idea about joining the grey into the purple up a the millennium ecu area, will save me a lot work as I crimped and taped up my wiring down at the lambda under the jeep with great difficulty and am still suffering with rust in my eyeballs the next day:(.
Thanks
Mark

[Gilbertd]

Just to prevent confusion, I'm Richard referred to by Toby (Tubbs), damn confusing all these usernames.....

I wouldn't agree entirely as in an ideal world you would want the actuator at the same on idle as normal running, then it never has to move as you come off idle. However, as you will no doubt discover, a gnats wotsit on the idle bleed screw will have quite an effect so getting it exactly the same can be a pain. But, if you can't get it the same, get it slightly lower rather than higher than the default for normal running. As Tubbs says, then the actuator is always opening rather than closing so much less chance of a lean mixture leading to a backfire and the requirement for a new airbox.

Not only does setting the cut off option save gas (although not a lot because there isn't a lot going in with the throttle closed) but it gives more engine braking on the overrun, always useful on an auto. The only time I have found it to be a problem is that with the diagnostics set to show lambda faults, I get a Lambda lean for too long fault flagged up every time I leave my mates place in France. There's a 3 kilometre long downhill section of Autoroute and as I'm usually towing a trailer, I go down it on a closed throttle. I've never found out how long is too long as far as Mr AEB is concerned, but it's less time than it takes to get down that hill!

[Tubbs]

Its always interesting for me to find other peoples take on a Leo. After all its mostly trial and error afterall. As the Op has discovered, not all gas converters understand older systems. And obviously the person who installed it didnt either judging by the fact that the lambda and tps had never been connected.
Personally when setting a Leo up ( thats a millenium by the way ) i like it to idle below the default, jump up to the default out of idle and hover around there. But its not always possible.
The only time i have used the cut off is when the engine 'hangs' when dropping back to idle on over run, or as richard gilbert says if you turn the diagnostics on it will log a lambda fault.
And also, common misconception, the cheif electronics engineer who developed the Leo was infact a woman. So if anything its Mrs AEB and not MR !
I know, it kind of shocked me too when i met her on a jolly to Italy many years ago.

[Mdizzal]

Okay I messed about with the two screws a little and checked the settings in the actuator tab and they read "idle opening steps over default = 20" then " idle closing steps under default = 20" and "out of idle opening steps over default 40" and then lastly "out of idle closing steps under default 40"

My car is idling very smoothly at 600 rpm but I can see that the O2 sensor is always at the far right of the bar and reading between 0.00v and 0.004 so basically it's not moving and I'm unsure if that is a good thing. My default reads 76 but the position is currently at 96. I willmnow drive it around for 20 mins to see how it drives.

[Tubbs]

Ok mate, listen they wont move unless you phsically tell them to get bigger or smaller. All those settings do is open the blue and red bar up to get the stepper to open and shut more. So at idle on the display screen is the stepper ( actuator ) sitting above the default at the top of the blue bar ?

[Gilbertd]

You've either managed to lose the lambda signal or you've mucked about with the settings and it's now running very weak at idle. The idle actuator setting is at 20 over the default so the limits you have set won't let it go any higher. Make sure the lambda is working out of idle and you haven't lost the signal, open the idle limits up and then tweak the idle bleed screw to get it back down to at or just below the default.

[Mdizzal]

Hi the lambda is still at the left jumping between the two last left boxes (green) but it defiantly still has a signal I have changed the settings so that the idle opening steps over default are now at zero so now the default reads 75 and the position is also at 75 as the settings Wont allow it to go any higher than the default, would that be okay ? I'm not too sure what the goal is so I'm getting a bit confused as to what I need to achieve ? Should the lambda be always going from left to right (weak and then rich) or should it be sat In the middle to show a perfect mixture?