Relationship between compression ratio and octane

Compression Ratio And Octane | Pilots of America

relationship between compression ratio and octane

Is there a relationship between compression ratio and minimum fuel octane? In answering, please give examples to support your comments. The compression ratio of your engine determines the octane rating of the gas you must use in the car. One way to increase the horsepower of. Increasing compression ratios for future SI engines would be the primary Bell , A. G. The Relationship Between Octane Quality and Octane.

The higher an engine's compression ratio, the greater the amount of heat generated in the cylinder during the compression stroke. Posted octane numbers on gasoline pumps are a result of testing fuel performance under laboratory and actual operating conditions.

The higher the octane rating on fuel the less volatile evaporative qualities and the slower the fuel burns. In the refining process, fewer gallons of higher octane fuels are yielded from a barrel of raw crude. The net effect is a loss in power and possible engine damage. The operator hears an audible "knock" or "ping", referred to as detonation.

Detonation may vary from a faint noise on light acceleration to a constant, deep hammering noise while driving at a constant speed. Improper timing adjustments, vacuum leaks, or excessively lean fuel mixtures may also cause detonation.

In reality, the premium label originates from the higher cost to refine and the resultant higher retail cost. Only engines with high compression ratios can deliver all the potential energy from higher octane fuels! Always consult the manufacturer's octane recommendation to determine the proper octane requirements for any given vehicle. Generally, engines with compression ratios of 9. Engines with higher compression ratios usually require higher octane fuels.

Many owners who operate vehicles designed to operate on 87 octane fuel experience ping and knock.

What's the connection between compression ratio and fuel economy?

They usually "fix" this problem by purchasing the higher priced, higher octane fuels. Most owner's manuals indicate that some light and intermittent ping is normal but that heavy or sustained ping or knock should be attended to by either purchasing the correct octane fuel or servicing the engine.

Most fuel refiners blend fuels for geographic areas and adjust their blends seasonally. These blending techniques compensate for the decrease in oxygen content with an increase in altitude and compensate for volatility during the warmer or cooler seasons.

relationship between compression ratio and octane

These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methanepropane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together.

Compression ratio - Wikipedia

It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens.

relationship between compression ratio and octane

It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are: Lead clogs a catalytic converter and renders it inoperable within minutes.

Compression Ratio and Octane Ratings: What You Need to Know | HowStuffWorks

The Earth became covered in a thin layer of lead, and lead is toxic to many living things including humans. When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more.

Airplanes are still allowed to use leaded gasoline known as AvGasand octane ratings of or more are commonly used in super-high-performance piston airplane engines.