Quote:
Originally Posted by drmiller100
the cause is if the rpm is slowing down, typically MAP is relatively low. If the RPM is rising, then MAP is high, and the driver is trying to accelerate.
NOS makes no sense for better mileage. HHO makes no sense for better mileage, unless you are a unicorn salesman.
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Without quoting all of that, yes you just described how a main spark table is basically set up (MAP vs RPM). Basically it needs to be set up this way to avoid misfires and/or engine damage. That does not imply that it is optimized though.
As for that last comment, that is why I specified that an oxidizer can effectively be added without additional fuel.
We are not talking about how an oxidizer like N2O makes power. I have been doing that for a very very long time, but it is irrelevant to this discussion of efficiency.
Whenever you lean out the AFR, the effect in the chamber is similar to adding an oxidizer because the ratio of free O2 to fuel goes up. At first this will actually speed the burn rate and efficiency will improve. If you go further lean, then the burn rate will begin to drop off.
Many people do add spark advance at this point, but more often than not they go beyond what returns the best fuel mileage.
Very high spark advance combined with a very lean AFR will make for an extremely load-sensitive engine that IMO will have an unacceptable number of misfires during normal driving, even when not outright stumbling.
This effect comes back to the reality of spark advance as a tuning tool in general. As you use advance to improve one end of the scale, you begin to pay for it at the other end of the scale. More energy is lost during the compression stroke with a lot of advance. This means you can only go so far with the starting the burn sooner before diminishing returns sets in. At that point you need to either change the characteristics of the fuel or the combustion chamber.
An oxidizer speeds the combustion process, which allows you to start the spark later in the cycle (not sooner), so besides a better energy conversion in the chamber, you also get less energy lost on the compression stroke.
A relatively small amount of oxidizer does not need extra gasoline in order to improve the burn in the chamber. In the heat of combustion the O2 will combine with H or C, or even other elements such as the aluminum that makes up the chamber surfaces. The point isn't so much what it ends up being combined with by the time it reaches the exhaust, but when it does its combining, and how many times during the critical window that increases energy transferred to the piston. With the use of an oxidizer there will surely be more free O2 leaving in the exhaust, but to assume that it just breezed through the chamber without affecting the burn is naive.
If you really have this belief, then I ask you to please set up an experiment with a small sacrificial engine. An oxidizer is easily purchased in the form of O2 or N2O. Put a wideband O2 sensor and a K-type thermocouple in the exhaust. Make sure your AFR starts out at the chemically perfect 14.6:1 ratio, make your observations as complete as possible, then add your oxidizer. Note everything that happens from rise in RPM, to the visual condition of the combustion chamber and spark plug upon tear-down.
If you have a way to measure a fixed partial-load power output, then all the better.
I can only share results that I have collected and highly encourage you to collect your own. There's no substitute for learning by doing. Yes you can absorb spoon-fed information, but it's not the same impact, and is often done too selectively.