[pgfpro]

I've been pondering this for some time now. IMHO I believe that 95% or more of the fuel during the power stroke is burnt. X amount of fuel has X amount of energy.

So on my engine 0.144 lbs/min total fuel testing lean-burn vs no lean burn when in lean burn the 0.144 lbs/min total fuel makes more power then NA
0.144 lbs/min total fuel. So this tells me that lean-burn with the same amount of fuel the BSFC has improved. Without lean-burn I will have to increase the amount of fuel to get the same power and thus see a loss in mpg. So the question is where did the efficiency come from. My guess it came from a better increase in cylinder pressure from the added air by an increase in dynamic compression.

Now this where it gets interesting. When running 30:1 A/F I have to increase the timing by about 4*. This is due to the slow flame speed issue with lean-burn. But with even increasing the timing it still must have a better BSFC. We all know that an increase in timing advance is really not a good thing due to the pressure before TDC and will lower efficiency. But in my case it out weighs this and I get a better FE. A couple years ago I wanted to test flame speed. So I did a ABA test and used nitrous to increase the flame speed. The gains we're substantial!!!! I started by pulling a lot of timing out, because from being a nitrous tuner I knew that the flame speed would increase. The test showed an improvement of 8 mpg with less then 0.144 lbs/min total fuel. So I took a fairly decent fast burn head and made it way faster.

Now the hundred-dollar question. Where did the extra efficiency come from? My guess is burn angle and cylinder pressure. The fuel was completely burnt before in lean-burn but now the efficiency has improved from burn angle and cylinder pressure. To this day I'm still very surprised how much nitrous helped by using its increase flame speed that in turn improved the FE with less fuel.

So, the next question is how to make this work without using nitrous. Nitrous isn't cheap anymore, (lucky for me mine is free from a sponsor) so its gain has a cost to it and makes it not worth the extra amount of fuel savings. Also before I forget, the amount of nitrous used would be equivalent to a small nitrous solenoid leak. Hydrogen could work but I don't know how much it would need to get the same results? Auto Ignition could also be an answer like Honda's F1 engine but that would require a DI engine and I'm not rich enough for that lol.