Chapter 5. Combustion Maladies and Fuel Qualities.|
10139 words. 9 illustrations.
'Knock'. Definitions and differences between detonation, pre-ignition and pinking. Potential for damage. Piston damage.
Octane rating. MON, RON, AKI (pump octane). Performance Number.
Ignition Timing. Centrifugal advance curve - features and critical points. Programmed advance. Performance benefits often over-stated.
Part Load Advance. Slower combustion. More advance required. Combustion irregularities with too much advance at light load. Effect on idle quality.
Knock Sensors. Timing control strategy. Filtering out the background noises. Location and number of sensors required according to number of cylinders.
The Hart Turbo - An Exceptional Case. Second spark plug. Location in detonation risk zone.
Practical Considerations. Octane equivalence table - relative effect of different factors. Range of variation according to conditions. Detonation assessment in the laboratory. Pressure curves with and without detonation. Difference from audible assessment.
The Basic Fuel. Evolution from early days around WW1. The advent of lead (tetra ethyl lead, etc.) and how it works. Need for scavenging agents. WW2 production and post war growth.
Gasoline Additives. Difference between additives and blend components. List of common additives.
Emission Control Influences. Early unleaded fuels. Reduction of compression ratio. Toluene as a lead substitute. Meaning of a fuel distillation curve.
Reformulated Gasoline. Introduced by ARCO as a low emissions fuel. Low evaporative emissions, lower toxicity and low CO and HC. Soon made mandatory in critical areas.
Lead Substitute MMT. Origins as AK33X. Modest effect. Effective for low lead fuels. Toxicity problems.
Unintended and Unforeseen Consequences. Side effects from fuel changes. Valve deposits. Carbon Rap. Effect of deposits on emissions and drive qualities. Sticking valves and piston rings.
Oxygen Blend Components. Alcohols - Methanol, ethanol, etc. Ethers - MTBE, etc. Advantages and problems.
Ethanol and Methanol as Alternatives to Gasoline. Table of properties - energy content, stoichiometric point, etc. Combustibility issues. Emissions. Inferior at low temperatures. Higher rate of consumption. Corrosive effects. Sustainable fuel conjecture.
Modern High Quality Gasolines. EPA standards not good enough. Car makers demand better fuels. Top Tier Gasolines. New higher standards.
Valve Seat Recession. Cast iron heads susceptible. The mechanism of seat recession. Positive and negative factors. LRP. FBHVC tests of possible cures at MIRA. Results. Lead still best. LPG issues.
Racing Fuels. Racing gasolines. Turbo F1 super-fuels. ELF blend of Toluene and n-heptane. Lower risk of detonation at very high speeds. Methanol in rich mixtures. Nitromethane. Nitrous Oxide. Amazing RON of Triptane when dosed with lead. Loony-fuel Hydrazine.