Lean codes only in winter?

[pyro225]

Interesting one - this happened last winter too…

When the temperature drops below around 5c I get random lean codes appear on gas on my 4.2 supercharged l322 with Valtek injectors and king Ecu.
When it’s warmer no faults at all?
Switchover is set to 45c

Any ideas?

[LPGC]

There are 2 likely reasons...

One is that it's likely the temperature compensation parameters in the King ECU are over-leaning mixture for cold temperature readings. This can be exacerbated if the vapour temp reading sensor isn't in the flow of gas being fed to the injectors - If it is fitted in the metal body of injectors or at the far end of plastic injectors and not directly in gas flow it will be slow to respond to changes in actual gas vapour temp, also prone to reading somewhere between actual gas vapour temp and engine bay temp instead.. If the vapour temp reading is lower than actual gas temp it will have the effect of leaning mixture to some extent, a sensor fitted at the far end of injectors (that doesn't see gas flowing past it) or in the metal body of injectors (which will take more time to warm up than the gas vapour) will see lower readings than a sensor fitted in the gas flow.

The other is that you might have the problem of gas injectors sticking due to oil in gas, mentioned on this forum viewtopic.php?t=19640

There are other potential reasons but they too boil down to temperature compensation/pressure compensation parameters and injector response.

Which Valtek injectors? Most Valtek injectors have internal restrictions tighter than 2.8mm while for the Supercharged L322 you'd need a fair bit of pressure and/or bigger flow than most Valteks could provide (if the engine is going to be capable of running on gas when you put your foot down), with the exception of some Valtek Type 32's (the OMVL Superlight copies, some of which have 3mm internals). If you have a combination of injector flow rate and pressure that is low flow for the spec of the engine it implies that the calibration will have high multiplier settings, unusually high (or low) multipliers can mess up temperature compensation which by default are set to be near correct for average multipliers.

The AEB (including King) ECU's are set up by default to compensate for gas vapour temperature AND compensate for reducer (water) temperature readings. Most ECU's aren't set up to compensate for reducer/water temperature by default because in theory (and in practice with an accurate gas vapour temp reading) the reducer temperature shouldn't (and doesn't) have any effect on fuelling, it is only the pressure and temperature of the gas that needs to be compensated for (not the temperature of the reducer, the thing that turns liquid gas into gas in vapour form, we read the temp of the gas it outputs directly...). But since you have your system set to changeover to LPG at 45degC the fact that the AEB ECU will compensate fuelling for temp of the reducer shouldn't affect fuelling much because it will be at 45degC (and a 45degC reducer temp reading won't lean mixture off by much) when it switches to LPG anyway.

There's plenty to say about injector response, temperature and pressure correction, how most ECUs account for temperature and pressure correction purely on the basis of gas laws / physics while assuming the injectors are ideal and not affected themselves (in terms of open/closing time) by changes in temperature and pressure. But it's a complicated subject and to describe in adequate detail would mean a very long post.