Expounding on Expansion
If you pour gasoline on top of an engine, it doesn’t start making power. When you burn gasoline, it generates heat. So then, if you ignite that fuel... it still doesn’t make power. Obviously there are several conversions of energy taking place in the engine.
When the spark plug ignites the fuel, it burns/oxidizes and releases heat. This heat expands the nitrogen and other gasses in the cylinder creating pressure. This pressure pushes the piston down, creating rotational force on the crankshaft. The gasses that absorb the heat to create pressure are called the Expansion Medium.
Ambient air is around 78% nitrogen. The burning fuel heats the nitrogen creating expansion — or pressure. As the HC fuel burns/oxidizes, the resultant gasses are water vapor, carbon monoxide, and carbon dioxide (see Combustion Characteristics Considered). Water vapor has an expansion ratio grater than nitrogen. In other words, if you have a cylinder filled with nitrogen, and another filled with water vapor — initially at atmospheric temperature and pressure, the same amount of heat BTUs applied to both cylinders will result in more pressure on the water vapor cylinder. Carbon dioxide has an expansion ratio even greater than that of water. If we feed an engine an AFR of 14.7:1, the exhaust gasses will be about 15.3% carbon dioxide, 18.1% water vapor, and about 66% nitrogen (+ trace other).
Exhaust Gas Recirculation (EGR)
For most of us alive today, our first exposure to EGR was in the 1970’s when the US EPA mandated EGR Valves to mitigate the formation of NOX emissions (NO & NO2). In conjunction with adding EGR, car companies reduced compression and retarded ignition timing. All 3 of these actions reduced the formation of NOX. Many folks disabled the EGR valve on their 70’s era engines and were rewarded with better performance and fuel economy. However, just for contrast, let’s look at an EGR strategy introduced about 90 years ago by George Arlington Moore.
Moore patented a method (US Pat No’s 1,633,385 and 1,768,854) of utilizing exhaust gasses recirculated back into the air intake to improve performance and fuel economy. What?!? Improve performance with EGR? Improve fuel economy with EGR?? I don’t stutter, you heard right. HOWEVER, whereas the OEM’s reduced compression, Moore increased compression. Whereas the OEM’s retarded ignition timing, Moore advanced ignition timing.
First let’s consider how EGR mitigates NOX. NOX is formed when the nitrogen in the air actually burns — chemically combines with the oxygen in the air. The formation of NOX is dependent on time and temperature. Higher temperatures form NOX at a faster rate. Exhaust gasses are made up of about 15% CO2, 18% H2O, and 66% N2. None of this contributes as a fuel, nor does it contribute as an oxidizer. In other words, exhaust gasses do not contribute to the combustion process in any way, they just take up space.
The 1970’s approach to NOX remediation was to introduce “stuff” into the intake charge that would not act as fuel, nor as an oxidizer (exhaust gasses). The result was a slower burn and thus lower peak temperatures. Since NOX forms more readily at higher temperatures, lab results showed this technique reduced NOX output levels. Moore observed that the lower combustion temperatures lent well to higher compression ratios. Furthermore, the slower burn benefitted from more ignition timing advance. Moore’s approach ultimately took advantage of EGR’s expansion medium properties to improve performance and economy. Moore’s emissions testing only sampled CO2, O2, CO, and visible smoke, but he does claim reduced emissions.
Note that modern engineers take a more intelligent approach to EGR compared to the 1970’s, so don’t disconnect it. An engine with a 10:1 static compression ratio rated for 87 octane gasoline (like the Honda 3.5 liter V-6 minivan engine) certainly uses EGR intelligently. EGR has the advantage of not freezing in winter temperatures, and requires no regular fill-ups — unlike water injection...
Water Injection
Water injection can be found under 2 categories; liquid and vapor. Liquid water injection involves spraying a fine atomized mist of tiny water droplets into the intake air stream. Water absorbs energy from its surroundings as it phase changes to a vapor. This cools the localized area. Liquid water injection has proven effective in eliminating damaging detonation in serious performance engines, like turbo applications. It is usually triggered at a certain threshold like 12 psi of boost. It is often mixed with alcohol (usually methanol) at a 50/50 ratio which adds to the cooling effect AND enriches the AFR. When used for fuel economy applications, it usually adds no benefit (at best), and can even hurt fuel efficiency (more likely). It absorbs so much energy as it phase changes that there is less total energy available to push on the piston. The fuel is powering a water vaporizer.
Water vapor injection capitalizes on the hefty expansion ratio of water. Since water expands more than nitrogen, it can beef up the expansion medium. One version of a water vapor injection system uses exhaust heat to vaporize the water, then admits the steam into the intake air stream. Several other versions use a bubbler. The bubbler is filled half way with water. Stainless steel pot scrubbers are added inside to break up larger bubbles into smaller bubbles; and a fresh air source is drawn by engine vacuum from the bottom of the bubbler. Some versions use fresh air, while my favorite version bubbles the PCV gasses up through. Bubbling PCV gasses up through water will pull heavy HCs and other contaminants out of the PCV charge. This alone helps the engine run better. The warm PCV gasses pick up water vapor, adding to the expansion medium.
All water injection systems are susceptible to freezing in colder temperatures. They all require frequent refilling. The PCV version requires periodic cleaning as well to remove the heavy oils and contaminants condensed from the PCV charge. If considering a water injection system, keep maintenance requirements in mind. Also, it may need to be disabled over winter months to prevent freeze damage.
Combustion Accelerant Supplementation
Distributor cap modified to tap ozone.
Both EGR and water injection tend to slow down the flame propagation rate, as the flame must jump over the “stuff that doesn’t burn” to get to fresh fuel and oxygen. To a degree, the more powerful expansion medium offsets some of the losses from the slower flame speed, yielding a net gain. However, to get the most from EGR/water injection, a combustion accelerant will counter the slower flame speed. A combustion accelerant chemically speeds up the flame propagation rate. Two examples are Ozone and HHO. Ozone is a less-stable form of oxygen. Ambient air contains stable O2 oxygen. Ozone is O3, O4...O60... Ozone is almost always generated electrically. A high voltage dipole separated by a dielectric plate creates ozone. This is the method employed by most commercial ozone generators used in air fresheners. They apply several thousand volts to stainless steel screens glued to both sides of an electrically insulating glass or mica plate. A spark also creates ozone. Older brushed DC motors create sparks at the brushes. You can smell the ozone near the motor while it runs. (Ozone has a chlorine like smell.) Dielectric plate ozone generators can be purchased, or even made relatively inexpensively. However, they require
Ozone drivers mounted to air cleaner housing. Ozone coils mounted inside.
frequent cleaning with dish soap and a tooth brush. The stainless steel screen on either side of the dielectric plate tarnishes and corrodes. Humidity in the air is the biggest culprit. Older engines with a distributor generate usable amounts of ozone inside the distributor cap. As the rotor spins around, it never touches the terminals. The ignition coil’s energy has to jump an air gap from the rotor to the terminal, creating ozone in the process. Drill a small hole in the cap and glue a length of small plastic emissions vacuum tubing in it (see image). Run the tubing to a vacuum port just manifold side of the throttle body. Make sure the distributor cap is vented, otherwise you will create a vacuum. (Electricity will travel freely in a vacuum. This creates carbon tracks down the sides of the cap that short the coil’s energy to ground. At first it just creates a random misfire. Eventually, a no-start.) An added benefit is by removing the ozone from the distributor cap, it lasts longer; ozone is a powerful oxidizer that corrodes the metal terminals easily. Less ozone = less corrosion.
Between tapping the ozone in the distributor cap and an add-on ozone generator, I took an ’84 Dodge Charger (2.2 liter carbureted) from 34 mpg to 42 mpg. In another instance, I tested a list of technologies on a small diesel generator. The ONLY one to improve fuel economy above the margin of error level was ozone (an 11% improvement). Since ozone is unstable, it requires less endothermic energy to separate into individual oxygen atoms used in the combustion process. This frees up more of the total energy to power the vehicle. Furthermore, since ozone falls apart more easily than ambient oxygen molecules, it takes less time to free up individual oxygen atoms. This speeds up the burn, working in our favor within the magic window.
HHO Cell, water enters bottom, HHO escapes from the top.
An under-rated combustion accelerant is on-board hydrogen. It is called HHO, HOH, Brown’s Gas, water gas, generically Hydrogen, and other names. It is created by electrolyzing water into its hydrogen and oxygen constituents. This gas is then fed to the air intake. Whereas gasoline has a flame propagation rate of 41.5 cm3/sec, and bottled hydrogen 212 cm3/sec, Chris Eckman at the University of Idaho showed HHO having a flame speed of at least 180,000 cm3/sec! The difference between bottled hydrogen and HHO is that HHO is made on-demand. When water is first electrolyzed, it contains stable H2 molecules, stable O2 molecules, as well as unstable radicals like OH-. In time (several seconds to several hours), the radicals stabilize into H2 and O2 gasses. The radicals are what set HHO apart, and what makes this gas magical.
As a simple experiment, you’ll need a glass of water, a little table salt, 2 metal utensils, and a 9 volt battery. Add about a teaspoon of salt to the water and stir until the salt is dissolved. Put both utensils into the water, making sure they are not touching.
Connect the 9 volt battery to the utensils, positive to one and negative to the other. You will see bubbles forming on the utensils. The one connected to battery positive is generating oxygen gas, while the one connected to the negative post is creating hydrogen gas.
Though educational, this approach is far from practical. There are hundreds (no, make that thousands) of videos on YouTube showing you how to build a hydrogen generator with a glass jar and egg beaters (and other equally stupid methods). If you decide to try an on-board HHO generator, your quickest and cheapest path to success is to simply buy one from a seller with a good reputation. A good system will include safety controls, as well as hopefully output controls. Ideally, you want to vary the output with the engine load to maintain an air-to-fuel-to-HHO ratio, and compensate for varying salinity levels as the water level drops.
Be aware that HHO and Ozone do not mix. I have done extensive testing with both. HHO works great. Ozone works great. But when you combine them together, they seem to counteract each other. Instead of getting even better results, you loose economy. The greatest success stories with HHO involved engines with EGR valves. The HHO did indeed counteract the slower burn rate caused by EGR. Ozone seemed to work great with or without EGR.
FE3
MPGenie Basics 051 Training - Expounding on Expansion Part 1
MPGenie Basics 051 Training - Expounding on Expansion Part 2
MPGenie Basics 051 Training - Expansion Science
