Propane Fumigation on gas EFI cars

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

One of the downsides to attempting to add small amounts of propane to a gasoline EFI engine is that propane, as a gas, easily displaces the air entering.

So does the EGR flow, either standard or increased.

So not only does it burn up with some of the oxygen it also displaces more oxygen, unlike a liquid fuel that wouldn't diplace as much.

There would be fewer oxygen free to react with the nitrogen in the air flow. Not so bad at all.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

So does the EGR flow, either standard or increased.




There would be fewer oxygen free to react with the nitrogen in the air flow. Not so bad at all.

I wonder if adding propane via the EGR circuit would be helpful. Maybe put a very small propane carb (e.g. lawnmower carb) on it? Of course NOx would be worse.

Edit: Which NOx could be offset via water injection.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

I wonder if adding propane via the EGR circuit would be helpful. Maybe put a very small propane carb (e.g. lawnmower carb) on it?

I guess it would not be of much help.

Of course NOx would be worse.

Most likely non-methane hydrocarbons would increase, while NOx would eventually decrease, unless the ECM would trim down the stock fuel injection flow.

Which NOx could be offset via water injection.

Had it been strictly to offset NOx, water injection would've been a more likely approach.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

I guess it would not be of much help.

Most likely non-methane hydrocarbons would increase, while NOx would eventually decrease, unless the ECM would trim down the stock fuel injection flow.

Had it been strictly to offset NOx, water injection would've been a more likely approach.

The idea I'm taking about using the EGR is to add both propane and air through there. The goal is to trick the ECU into burning the propane with enough oxygen so it actual does something other than enrich the fuel mixture. By adding propane and oxygen together through the EGR the ECU will continue to add enough air and gasoline in through the the normal means. Since the propane will burn with the extra air the O2 sensors should see pretty much the same amounts of O2 as if the engine weren't modified, as long as the propane and air metering are good enough of course. The MAP sensor should compare to the throttle position sensor and MAF sensor like it would without the mod. The benefit would be it would burn the propane and make more power which would allow you to close the throttle more and use less gasoline over all.

But with fuel and air entering through the EGR valve NOx will increase since the A/F mix will be stoichiometric with no inert gas like to exhaust gas to lower the combustion temps.

Another con would be the throttle would tend to be more closed causing more pumping losses.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

But with fuel and air entering through the EGR valve NOx will increase since the A/F mix will be stoichiometric with no inert gas like to exhaust gas to lower the combustion temps.

Depending on the proportion of fuel enrichment, it won't harm performance, it may actually lead to some improvement. On a sidenote, replacing the so-called inert gas with a gaseous fuel is more likely to decrease NOx, as it will decrease the amount of free oxygen molecules to reach with the nitrogen. A richer AFR is usually more likely to result on lower NOx, regardless of how the supplemental fuel is delivered to the intake tract.

[Isaac Zachary]

Originally Posted by cRiPpLe_rOoStEr

Depending on the proportion of fuel enrichment, it won't harm performance, it may actually lead to some improvement. On a sidenote, replacing the so-called inert gas with a gaseous fuel is more likely to decrease NOx, as it will decrease the amount of free oxygen molecules to reach with the nitrogen. A richer AFR is usually more likely to result on lower NOx, regardless of how the supplemental fuel is delivered to the intake tract.

I think I wasn't clear. I meant replace EGR with a flow of propane and more air so it wouldn't enrich the air fuel mix, but rather keep it the same.

[cRiPpLe_rOoStEr]

Originally Posted by Isaac Zachary

I think I wasn't clear.

Indeed. Well, then it would most likely either increase NOx, or the ECM would enrich the AFR to keep NOx within the limits.