
Horsepower Past & Present

When men get together to discuss their prized vehicles, you can be practically guaranteed that the conversation will include, or completely be dominated by, talk about horsepower. Before the motor vehicle, the horse was the vehicle of choice, the power source for moving supplies and goods, and a primary source of power behind the United State's early agricultural and industrial prominence.
The horse essentially did work for its owner. The more powerful the horse the more work it could do. A standard horsepower was defined as the mass that a horse could move in a specified time period. Suffice to say that since horsepower represents a rate of doing work, more horses means more work could be done, or the same work could be done more quickly. Standard lawn mower or snow blower engines now weigh in around 5 horsepower, riding mowers might be closer to 15, a typical car is in the neighborhood of 100-150 HP, and for you race car types, there are typically several hundred (figurative) horses under those hoods.
The Workings of Gasoline Engines
Please watch the following (:15) video:
Click for a transcript.
[Video opens with a close-up of a spark plug.] [The spark plug it fed electricity and a blue spark is seen.] [We hear the noise of a loud shock.] [This is repeated several times.] [Video ends]
The combustion of the gasoline occurs because of the appropriate mixing of a vapor of the gasoline with air and a spark provided by the spark plug (see left). The battery in the car provides the electricity to create the spark; it is also used to run the radio, lights, and to start the starter motor to start the gasoline motor. The motor needs to turn over so the piston rises in the cylinder, compressing the air and gasoline mixture, which is ignited by the spark. The timing of these events is very important, hence the need for a timing belt. The resulting combustion produces hot gases, which drives the piston down providing the energy to run your car. The starter motor has started the engine and now is no longer needed, until next time.
Thus, the basic four strokes (for a 4 stroke engine) are:
Engine Stroke | Description |
---|---|
Intake Stroke | Air and gasoline (sprayed in a fine mist to permit better mixing of the air and gasoline) enter the cylinder. |
Compressions | The piston head rises, compressing the air/fuel. |
Combustion | The spark ignites the combustion/detonation, which rapidly pushes the piston down (via a crankshaft connection; turns the vehicle's wheels). |
Exhaust | The products of combustion are vented out of the cylinder on the way to the catalytic converter and the tailpipe. |
Once again, I suggest that the curious amongst you take a trip to the "How Stuff Works" website to see a more detailed presentation of How Engines Work.
The Gas Alternative?

The lead acid battery that sits under the hood in nearly all our cars is heavy, and not inexpensive (especially if you leave your lights on regularly). Considering the size and weight of this battery, and its purpose to just start your car, you can imagine the size, weight, and expense of the one that would be needed to actually power your car? This is the major reason that electric cars running on stored electrical power did not make it off the golf course and onto the roads
Interestingly, living in England, the milk would be delivered to your doorstep, every day except Sunday, by a fleet of electric "milk floats" which started in the 1970's. As we will discuss later, many of the new approaches in vehicles and fuels will occur in those organizations with a large fleet of vehicles.
Who's That Knocking? - The Story of Octane

When the Model T Ford was filled up with gas, variations in the production and quality of the gasoline sometimes caused "knocking" in the engine. This violent shaking of the engine caused excessive wear on the engine and limited its power. The cause was the self-ignition of the gasoline and air mixture on the compression stroke (2nd stroke - remember?). In a diesel engine, this is actually desirable, as they don't have spark plugs, but in gasoline engines, it's not a good thing. The knocking is related to the shape, size, and type of molecules found in the gasoline, which is pretty complex stuff - when you account for the added cleaning compounds and environmental packages, your gasoline can include over 100 separate compounds! Please watch the following (1:15) video:
Click for the transcript.
[Video opens with Dr. Mathews standing in front of a large machine.] Dr. Mathews: I am here at the energy institute research facility. To my left is an octane rating engine. When you go to buy gasoline from the garage you have a choice of several octanes. Most of you will be buying 87. Iso octane, the octane number, is based on a mixture of iso octane and heptane. When you are buying an 87 octane gasoline, what it means is it will have the same knocking behavior as 87 percent iso octane and 13 percent heptane. The way that is tested is in a device exactly the same as this. What we will do is take an 87 percent mixture of iso octane, a 13 percent of heptane, and blend them together, and see how they behave in certain conditions in this particular engine. Then we will compare it with a complex blended mixture of gasoline. Remember gasoline is going to contain at least a hundred different compounds. So you are not buying octane, your not buying iso octane, and you are not buying heptane. They might be there in small quantities but they are not a majority of the components. What we are looking at is knocking behavior. If we get that undesirable, spontaneous combustion when we compress the cylinders and the gasses and the fuel in the air, and it self ignites, that is called knocking. That is completely undesirable in a gasoline engine but it is exactly how a diesel engine works. [Video ends]
Basic Environmental Issues

This knocking can be eliminated by changing the composition (or size, shape, and type) of the compounds. One of the early octane booster compounds added to gasoline was tetraethyl lead. This has been banned now to reduce lead vapors that end up depositing lead in the bloodstream, which resulted in reduced mental capacity, particularly in children.
A bit more about lead.
Now we are required to make many changes to our gasoline recipe to meet environmental challenges (more on this in the next lecture).