Thoughts on the amount of fuel burnt and its efficiency?

[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.

[Ecky]

Best I understand, you're running a 30:1 AFR under boost, so it isn't like you're reducing vacuum. I would guess that the extra gasses in the cylinder are acting as a medium of expansion, and are causing some thermal efficiency gains as well. Water injection can increase economy because of the expansion from the phase change, which more than offsets the energy lost to the phase change itself, just as an example. And, if you have twice as much air in a cylinder, and you add a given amount of energy to it (combusting a fixed amount of fuel) the temperature will be lower and you'll be losing less energy through the cylinder walls and combustion chamber. The turbocharger also harvests some of the expansion energy and puts it back to useful work.

Just an educated guess, however.

[cRiPpLe_rOoStEr]

Have you never tried water injection with this engine? As water injection is well reported to fare better on engines with forced induction, may be worth a try.

[pgfpro]

Originally Posted by Ecky

Best I understand, you're running a 30:1 AFR under boost, so it isn't like you're reducing vacuum. I would guess that the extra gasses in the cylinder are acting as a medium of expansion, and are causing some thermal efficiency gains as well. Water injection can increase economy because of the expansion from the phase change, which more than offsets the energy lost to the phase change itself, just as an example. And, if you have twice as much air in a cylinder, and you add a given amount of energy to it (combusting a fixed amount of fuel) the temperature will be lower and you'll be losing less energy through the cylinder walls and combustion chamber. The turbocharger also harvests some of the expansion energy and puts it back to useful work.

Just an educated guess, however.

Thank you. See you just found something I totally missed lol

I was so focus on the flame speed that I forgot about the extra gasses.

[pgfpro]

Originally Posted by cRiPpLe_rOoStEr

Have you never tried water injection with this engine? As water injection is well reported to fare better on engines with forced induction, may be worth a try.

I haven't tried water injection on this engine. So I will put it on my "to do list"

[serialk11r]

I agree with Ecky, it's running lean with boost. This is basically the principle that Mazda used in Skyactiv-X.

To an extent, excess gas improves efficiency by reducing temperatures and losses to conduction. Faster combustion also improves efficiency, and you're getting that from boost.

[cRiPpLe_rOoStEr]

Originally Posted by pgfpro

I haven't tried water injection on this engine. So I will put it on my "to do list"

If you find a way to use that residual moisture extracted by the air conditioner, would be even better.

[pgfpro]

Originally Posted by cRiPpLe_rOoStEr

If you find a way to use that residual moisture extracted by the air conditioner, would be even better.

That would be pretty cool. Unfortunately, both the Camaro and Talon don't have AC. I won't be putting AC on either of them due to where I live we just don't have that warm of weather to justify it.

I did some calculations on how much the usage nitrous would cost for 7lbs. It came out to around $30.00 for 12 gallons of gasoline or 603 miles. On waste solvent it would be worth it to test the numbers.

[mpgmike]

Thank you for this thread! It got me thinking and my thoughts went to some new places. I have experienced the benefit of a more powerful expansion medium. Running lean like you are may just be "adding more expansion medium". We know that at 14.7:1 the exhaust is as hot as it gets. When you go lean from stoic the exhaust (and combustion temps) get cooler. This has to mean that more of the thermal energy is converted to pressure.

In short, I believe your extremely lean AFRs are adding more expansion medium to absorb the heat of combustion, wasting less out the exhaust (or coolant passages).

As for compensating for the slower flame propagation, as already mentioned, HHO works. I've also had excellent results with ozone. Both have maintenance issues, though. HHO systems require water refills and periodic cleaning. The most common method of generating ozone is with dielectric plates. They corrode and require frequent cleaning.

[RustyLugNut]

Originally Posted by Ecky

Best I understand, you're running a 30:1 AFR under boost, so it isn't like you're reducing vacuum. I would guess that the extra gasses in the cylinder are acting as a medium of expansion, and are causing some thermal efficiency gains as well. Water injection can increase economy because of the expansion from the phase change, which more than offsets the energy lost to the phase change itself, just as an example. And, if you have twice as much air in a cylinder, and you add a given amount of energy to it (combusting a fixed amount of fuel) the temperature will be lower and you'll be losing less energy through the cylinder walls and combustion chamber. The turbocharger also harvests some of the expansion energy and puts it back to useful work.

Just an educated guess, however.

Upper class and graduate courses expand on these concepts. You are but a hop, skip and jump from a doctorates.

We also must add that pgfpro has certain advantages built into his engine system. His head design as well as the turbocharger produces increased turbulence and adds heat to the combustion mixture. The reaction rate ( increased thermo-chemical reaction rate ) is reflected in his need to only add 4 degrees ignition timing. In our attempts to run ultra lean mixtures with a Daihatsu engine with hemispherical combustion chambers, we found we had to add over 15 degrees additional timing to reach our torque potential.

I am not sure if his 4 degrees of timing included the NOs injection?

The bottom line is that . . . increased heat, increased turbulence and increased thermochemical activity result in increased flame speed.

Compressing the air/fuel mixture increases the heat.

A high swirl/tumble head design increases turbulence as well as the force of a turbocharged system.

The addition of oxygen, ozone or hydrogen allows for increased thermochemistry to occur.

In the run-up to the AutoXprize, a team proposed to run an engine on pure oxygen and gasoline. This was an extreme proposal that would need ceramic materials and water injection. The longevity of the ceramic materials was questionable and the amount of water needed was considerable to carry about. Outside of how to produce and carry the pure oxygen the idea was sound in that the ignition initiation could be carried out just before top-dead-center (TDC). I do not recall their expected target for BSFC (brake-specific-fuel-consumption).

Using the nitrogen in our surrounding air as a working fluid is much more plausible if we can keep combustion temperatures below 2300 degrees Centigrade or if reactions occur quickly enough to prevent the formation of NOx pollutants.