LTFT's on CNG / LPG

[2008Silvy]

I am curious how trinity calculates the LTFT's? Is it the same as the car's ECU? I get weird results when running on CNG, but everything works perfect on petrol. It will show +30 LTFT's. The car does act funny too sometimes, but giving it more gas just makes it run rough and will die eventually. It obviously doesn't need more gas but readout says lean, usually bank 1?.

Maybe these oxygen sensors just won't work on CNG? I thought they would read stoich AF ratio, no matter the fuel, they just measure oxygen content.

It's funny the readout of the O2 voltages shows them switching around pretty good, but then it'll get on a wild hair and start increasing injection times of one bank (the gas ECU just follows the stock ECU). Is there any way to force it to run in open loop, even temporary to check things out? Been pulling my hair out for days trying to get rid of this, done everything, changed plugs, redone whole CNG system, nothing.

[06MonteSS]

the fuel trims are read directly from the ECM... so whatever the ecm reports, is what is shown by the trinity...

need special/specific tuning for cng/lpg... the stock ecm tunes/programming are made for regular/normal gas, not cng/lpg...

you will need custom tuning if you are running cng/lpg...

[2008Silvy]

Thanks, will be in touch.

[06MonteSS]

not me... don't send stuff to me... I don't tune for that stuff... heh...

[2008Silvy]

lol ok, not sure why not though, it works just like petrol when it's working right, and you have to tune for petrol anyway because it's bi-fuel. The CNG has it's own fuel maps on a different computer. It just follows the car ECU's strategies for closed loop, enrichment, etc, and you fine tune things on the new gas ECU.

I finally found the problem. Little air leak around one of the fuel injectors. Thank goodness, I was about to go crazy.