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Map table switching


zoltan
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Ive got my 3.5 EFi running sweetly on petrol now is time to save some pennies and get it working on LPG. My ECU is built with a wire for map table switching only I can't remember whether I ground this or give it voltage to table switch

Also, running on LPG, do I have to have the fuel pump churning away all the time or can I switch this off via a relay when on LPG? The only reason to have the petrol system pressured up is for faster change over to petrol on the hop

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I considered this switching malarky, and came to the conclusion that having a 3-way switch was the answer.

The first position is petrol system on, petrol map.

The second would switch the relays for both systems on, but a logic gate would keep the map-switch in it's current state, so you would keep running on the fuel you are already on.

The third position is obviously for the LPG map, with the petrol system off. This would also need a solenoid for the LPG on it to stop the gas actually coming out of the carb when in the middle position.

As I've already got a 3-way switch from my carb LPG system in my dash, this seemed like a worthwhile idea.

hth,

Jake

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As above, +12v is normal but best to check with the supplier first :)

I switch mine of the LPG solenoid circuit so when the LPG is activated it changes to a zero'd out fuelling ,map and a different spark map. You can then fine tune the changeover time in MS to give a smooth switchover.

I leave the fuel pump running so the change from LPG to petrol is seamless but you could possibly turn it off if you feel it will help extend it's life although immersed fuel pumps seem to last forever anyway.

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It is recommended by many to leave the petrol pump running when on LPG. It provides a degree of cooling to the injectors by circulating the petrol, and can help prevent the rubber seals hardening and subsequently leaking.

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It is recommended by many to leave the petrol pump running when on LPG. It provides a degree of cooling to the injectors by circulating the petrol, and can help prevent the rubber seals hardening and subsequently leaking.

That make the installation even easier this morning. If I think back to the number of times when I was running on carbs where I was wanting to go to petrol as the gas ran out on the move it would be good to have this seamlessly achieved instead of trying to time the flicking of two switches

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