lamba sensors not connected

[allante]

I have noticed on the 3 cars I have had with LPG that the lambda sensors are not connected and in the installation instructions it says do not connect. But I do see on the forums that some people have them connected. I'm wondering why some are connected and some not and if there is any advantage to having them connected.

[Gilbertd]

The only advantage is that it allows the LPG software to display what the lambda is doing. Gives you everything on one screen rather than having to have a laptop telling you what the LPG system is doing and a code reader to see the lambda. It has no effect on the fuelling though.

[allante]

Thanks for your reply.
That sounds like a good option for diagnosing problems including non LPG issued.

[scottyf]

I thought some systems adust themselves using the lamda reads on the lpg slightly?
I know the ecu of the car would adjust it regardless but still...

[LPGC]

I thought some systems adust themselves using the lamda reads on the lpg slightly?
I know the ecu of the car would adjust it regardless but still...

Single point closed loop and multipoint none slave systems need to connect to lambda but these are not really suitable for modern vehicles.

A few systems are capable of running in slave mode at anything up high engine load and then switching to a kind of lambda compensated mode when the engine is running at high loads. Here we're talking about systems that don't have many handles over fueling (can only really be calibrated using a single multiplier and single offset), so it might be expected that the feature would be most useful on such systems... But even with these systems it is usually easy enough to get calibration correct across the entire rpm/load range (because such systems are usually fitted with good injectors) and the feature is hardly ever seen enabled. Arguably, the feature isn't very useful but can cause potentially engine ruining consequences if, for example, a lambda probe goes wrong and continues to read rich when the engine is actually running lean.

If you get any problem on an engine that causes the petrol ECU to switch to open loop 'limp home' mode, then usually if the LPG system is calibrated properly the engine will continue to get a mixture that isn't far wrong on LPG too, so booting it on LPG the full throttle mixture shouldn't be a problem. But suppose the problem is due to the lambda probe showing rich all the time and when you boot it (on LPG) the LPG ECU switched to lambda compensate mode and continuously leans the mixture... Probably damage the valves on, say, a 4.7 V8 Jeep with a Prins system fitted by certain installers that all upload the same LPG config settings for this particular model of vehicle, that!

While on the subject, other aspects of config on such systems that can damage valves are installers that actually do try to map the system themselves but leave the MaxGinj (maximum gas injector pulse duration allowed) figure stuck at maybe default parameters that are too low for torquey low revving engines.

Simon