what temp to switch from petrol to LPG?

[HangOver]

I have one of those engine watchdogs thingys that shows temperature in °C
I was just wondering if there is a "best" temperature to switch over?
I have tried 40-60°C with no difference really. I know it has to be warm so the gas convertor?/mixer doesn't freeze up but don't know when.

[bee utey]

what temp to switch from petrol to LPG

Whenever the coolant is sufficiently above freezing and able to cope with your predicted power usage.

Any normal lpg system in good condition should be able to run from stone cold, so long as you don't demand much power before the engine hits about 30-40°C. I've never cold started on petrol to get a gas car going, unless it was petrol injection dual fuel or injected gas. Even then they will run on gas in a frost.

Warming up a stone cold engine on petrol has the risk of fouling the plugs and you may need standard heat range plugs to cope. Then they are too hot for full power use on gas.

[p38arover]

I think the ECU on mine is set to 30°C. I'd have plug the laptop in to check.

Having said that, I had no problem running from cold for a few days after I had a fuel pump failure (the overnight ambient temps at that time were about 15-20°C).

[MacMan]

I only ever start on petrol when I have no gas. Always have.

[101RRS]

I have one of those engine watchdogs thingys that shows temperature in °C
I was just wondering if there is a "best" temperature to switch over?
I have tried 40-60°C with no difference really. I know it has to be warm so the gas convertor?/mixer doesn't freeze up but don't know when.

Your watchdog will be showing the metal temp in the engine not water temp. My TM2 Combo is normally showing normal operating temp well before the thermostat opens so gets hotter well before water (ie my TM2 shows 72 degrees (normal) well before the water gets to its 85 degree operating temp.

But I start on gas in Spring, Summer and Autumn.

Garry