Propane Air/Fuel Ratios.

[turbine guy]

A little background info; I have a 2005 GMC Sierra Denali fitted with a Bi-Phase liquid propane injection system. (6.0l LQ9 engine.) This system replaces the gasoline injectors with liquid propane injectors, and has a GM gasoline pump immersed within the propane tank, keeping the rail pressure 50psig above tank pressure to eliminate vapor lock. To date the truck has accumulated 52,000 miles with no issues with the fuel system. Initially when fitted with the Bi-Phase conversion, the VCM was tweaked by a fellow with HP Tuners, and I recently purchased the truck. (Estate sale, owner passed away.)(Tuning consisted of increasing ignition timing at idle, scaling the injectors and leaning the injector crank pulse mass tables.)

My question; Currently the VCM is commanding the standard gasoline air/fuel ratio of 14.67:1 In PE, approximately 12.7:1 Stoich A/F ratio for propane in cruise is 15.67:1 and in power, 13.9:1 Can I simply command these A/F ratios, or will the narrow band O2 sensors be outside of their operating ranges, not allowing the VCM to hit the commanded ratios?
I know I can get to the correct ratio in PE, but what about the 15.67:1 overall? This truck runs well, but I think there is fuel mileage being left on the table so to speak.

Thanks in advance guys.

Robin Sipe.

[cutlass_455]

Haha, I have no idea how to help you, but this is damn interesting. I hope some of the smart guys chime in here. Fort St John, thats north, wow. Im close to Edmonton and I thought that was north.

[smithers]

narrowbands search for stoich or Lambda 1.00, not necessarily 14.68:1 AFR... that just happens to be the stoich value for gasoline. Which ever fuel is being used...


I have no first hand experience with propane injection, but would suspect one could simply adjust the Stoich AFR table to your desired fuel being used and let the trims (using the narrowbands) handle the rest... the will find stoich by toggling on the rich and lean sides of lambda 1.00...)

[mecanicman]

Correct. Right now your fuel trims are likely always negative because the 02's are trying to achieve stoich, but computer a/f calculation is putting in to much. Change the stoich value to propane and the trims will likely be a combination of +/- like any vehicle.

[patooyee]

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