LPG on 3.9V8 problems

Long story short!! I have had to revert to the OEM Lambda sensors in a 3.9 cat exhaust (no cats as cut out and engine did not have them in the first place) not cheap £83.00. Problem is I cannot obtain the correct data to input into the AEB Leonardo Program. Even NGK Tech guys in Japan (who make them) seem able to help. What V output range do they operat on, Are they Open Circuit, Simulated Earth or Square Wave (if not standard what settings)? Without this info I am unable to tune/set up the ECU! I have tried the old fashioned way but this raises another issue. The voltage at the Lambda is higher than at the wire going into the AEB ECU? Getting this LPG to run correctly and above 7mpg is really starting to P155 me off.
Can anyone help. Please!!!

What type of Lambda sensors are you using? 3 or 4-wire?

The OUTPUT signal range is very small, less than a volt.

4-wire sensors have built-in heater elements that are fed from the engine ECU, 2 wires for the heater and 2 for the signal.

There are two basic Lambda types, are the ones you are using correct for the ECU?

Peter

listerdiesel said:

What type of Lambda sensors are you using? 3 or 4-wire?

The OUTPUT signal range is very small, less than a volt.

4-wire sensors have built-in heater elements that are fed from the engine ECU, 2 wires for the heater and 2 for the signal.

There are two basic Lambda types, are the ones you are using correct for the ECU?

Peter

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It is the original equipment Lucas Lambda, which in reality is an NGK sensor, that was fitted by the factory although a brand new one. It has three wires. Red 12V+, White Earth & black the signal wire (this connects the the shielded earth return to the ecu. This much I do know. What I need is the specific data for the rate and type of output along the signal wire. NGK were not very helpful and only really suggested that it would be whatever resistance (therefore voltage output) that was specified by the vehicle manufacturer.

This could be 0-1V, 0-5V, 5-0V (Type A or B, 1 or 2) 0.8-1.6V? It could be any of the above and I also need to know is it open circuit, standard square wave etc.

There are two Lucas Lambda sensors listed, 3LS and 4LS. I assume that the first digit is the number of wires on the sensor.

Peter

The sensors are 0-1v,but in reality they only get up to 0.8v. Its pointless trying to get them to work unless you change the tune resistor in the engine ecu loom for a Cat type one.Unless you change it the ecu will not look for an Oxygen sensor signal and continue to run open loop.
It will run better closed loop anyway,but you should also be able to change the settings in the LPG ecu to just piggyback the petrol injector pulse width - this is a much more accurate way to trim the LPG.
The waveform form the oxy sensors running in closed loop is a sort of spiky AC type wave going lean-rich about once a second or less as speed rises.

eightinavee said:

The sensors are 0-1v,but in reality they only get up to 0.8v. Its pointless trying to get them to work unless you change the tune resistor in the engine ecu loom for a Cat type one.Unless you change it the ecu will not look for an Oxygen sensor signal and continue to run open loop.
It will run better closed loop anyway,but you should also be able to change the settings in the LPG ecu to just piggyback the petrol injector pulse width - this is a much more accurate way to trim the LPG.
The waveform form the oxy sensors running in closed loop is a sort of spiky AC type wave going lean-rich about once a second or less as speed rises.

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Sorry, totally lost me on that one. The car does not run lambda's nor does it have cats. I only need the lambda for the LPG ECU! The 'tune resistor!!!! Would |I be correct in assuming this regulates the voltage that goes to the Lambda +Volt red wire? If so, stupid question here, what does it look like and roughly where would I find it? I have 80% of the old wiing loom lurking around somewhere. This could explain why the lambda is reading between 0.5v and 1.4v!!!

Cheers

Dod51e said:

Sorry, totally lost me on that one. The car does not run lambda's nor does it have cats. I only need the lambda for the LPG ECU! The 'tune resistor!!!! Would |I be correct in assuming this regulates the voltage that goes to the Lambda +Volt red wire? If so, stupid question here, what does it look like and roughly where would I find it? I have 80% of the old wiing loom lurking around somewhere. This could explain why the lambda is reading between 0.5v and 1.4v!!!

Cheers

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Most of the ECU's have more than one setup, called 'tunes' (referred to as such in the Land Rover RAVE manual) and you can select various options by an external link or resistor.

The LPG ECU also needs that Lambda information, as it otherwise has no feedback for mixture strength etc.

Ours is a Zavoli Multipoint system, but when we use the laptop to read the values, the Lambdas are there, along with the rev's, water temperature, gas pressure and temperature etc etc.

Possibly best to get in touch with an installer who is familiar with your LPG system.

Peter

So how have you wired the Oxygen sensors in - do they go to the original petrol ecu,or just into the LPG ecu ? Any of the 14CUX petrol ecu's will look for and use Oxygen sensor signals with the right tune resistor plugged into the ecu loom.(The plug is about 9" from the ECU plug itself in the loom.)Then you can set up the LPG ecu to just piggyback the petrol injector pulse and fine tune from there unde the "Modify carb" page.

i have the aeb, it is set up to 5-0 v for the lambdas, its a p38 tho!!

can't remember is its a or b, i will do a screen print tomorrow for you if you like!

basically all you need do is get it to emulate what it does on petrol, so run it on petrol and when you have the correct setting it will flick from lean to rich quite rapidly.

keep trying the settings an remember to press enter or it wont save the setting, i usually press enter then re start the prog to be 100% sure.

if you set the lpg to change over at 500rpm this will keep it on petrol for you whilst you faff around. remember to press enter to affect the change, and remember to reset it once finnished.

i think also its set to whatever is standard for the square wave/ground simulation section!

System Setup 2 - tuning a closed loop mixer system | None | DIY-LPG is a bit of help if you don't understand the aeb system.

once its flicking to and fro on petrol, you can have a look at the gas, remember to change the changeover rpm you adjusted above. if its not flicking then its the vap that needs adjusting.

look on the link for info on this or google your particular vap!!!

i have managed to get mine more or less spot on. remember its better with a slight bias to rich than lean!!!

Well from searching the internet I found a decent article on the RPI site. There, it says that the Lambda's run 0-1V but with a controlled voltage 'in' of 5v from the ECU. Problem is that the loom is from a NON cat/lambda car. THe Rangie did not have cats/Lambda's for the petrol system as it was manufactured just before the change. I have a 14CUX ECU that can be fitted but will the loom have the lambda connections and the correct tuning plug? Or the correct 5v output?

The article was either not decent or you read the wrong bit.The Titania sensors for 14 cux are 3 wire 0-1v sensors which generate their own output.The Titania sensors used on RR P38's from 95-99 are 4 wire 5-0v sensors which use a 5v input.
If the oxy sensor wiring is not in place then its probably easier to set up the LPG ecu to just piggyback the injector pulse width an run open loop.
The only problem with this is in the trimming of the ecu to match the petrol system.You really need some feedback info to make sure its not running lean - the main enemy of LPG.