SOHC engines feature a single...
SOHC engines feature a single camshaft that controls all of the valves but many Honda engines feature DOHC configurations, which means there's a separate camshaft for the intake and the exhaust valves. The advantage here is that the camshafts can be placed closer to the valves, allowing its lobes to either work directly on the valves or through smaller rocker arms. This keeps the valvetrain's inertial mass to a minimum, which helps high-rpm operation even more.
SOHC (single overhead camshaft) engines have just one camshaft that controls both the intake and exhaust valves but many Honda powerplants feature dual overhead cams, meaning there's a separate camshaft for the intake and the exhaust valves. The advantage here is that the camshafts can be placed closer to the valves and allow its lobes to either work directly on the valves or through smaller rocker arms. This keeps the valvetrain's inertial mass to a minimum, which helps high-rpm operation even more. Most high-performance Honda engines use dual overhead cam valvetrains, also known as the DOHC configuration.
Select Honda engines have one of the greatest innovations for performance-minded, small displacement engines-VTEC. VTEC is Honda's unique and highly effective variable cam timing system. The system affords the intake and exhaust cams two sets of lobes: one set optimized for low-rpm effectiveness, the other for high-rpm use. This gives the engine a wider operating range, enabling one to build something that's quite docile at lower engine speeds yet remain capable of high-rpm screaming. Honda's i-VTEC is similar but also allows for intake camshaft phasing adjustments, advancing and retarding it to alter cam overlap for a broader powerband.
The intake system consists...
The intake system consists of the intake manifold, featuring an open chamber, or plenum, attached to a series of pipes that span from the plenum to the cylinder head's intake ports. The throttle body serves as an air-metering valve and is mounted to the plenum's end.
The Intake System
The intake system consists of the intake manifold featuring an open chamber, or plenum, attached to a series of pipes that span from the plenum to the cylinder head's intake ports. The throttle body serves as an air-metering valve and is mounted to the plenum's end. The throttle body controls the amount of air the engine sucks in, thus controlling engine speed and horsepower. When it's shut, air is limited so the engine is forced to idle. When wide open, the engine ingests all it can to produce the maximum power it's capable of. The manifold contains the fuel injectors, which are electro-mechanical valves controlled by the ECU-the engine's brain. The ECU controls the amount of fuel injected by modulating the injectors' tiny valves' open and close time. During idle conditions, only a small amount of fuel is injected but with the throttle fully opened, allowing additional air to be ingested, the ECU signals the injectors to remain open longer to inject a proportionally greater amount of fuel. More fuel and more air equal bigger explosions and more power to the wheels.
The Ignition System
An electrical spark timed by the ECU and fired across the spark plug's electrodes ignites the flammable air/fuel mixture in the cylinders. The spark fires just before the piston reaches TDC, near the peak of the cylinder's highest compression pressure. This is the most efficient time to fire the spark. Usually, spark timing advances alongside engine speed because at higher engine speeds there's less time for combustion events to take place so it must be started sooner in the cycle to maintain proper operation.
The Exhaust System
The tubing directing burnt exhaust gases away from the engine is the exhaust system. This includes the exhaust manifold, catalytic converter and exhaust piping. The manifold collects each of the cylinder head's exhaust port's waste gas and collects it into a single pipe. This leads into the catalytic converter where poisonous constituents of the exhaust gas, like nitrogen oxide, various unburned hydrocarbons and carbon monoxide, are converted into non-toxic carbon dioxide and water vapor. From there gases flow into the exhaust pipe where they pass through the muffler, reducing noise to an acceptable level and then out into the atmosphere.
The Intake Stroke
With a basic understanding of an engine's moving parts under your belt, now's a good time to explain the four-stroke process and find out how everything works together. Manipulating the cycle is essential when looking for more horsepower so it's important to completely understand the different parts and how they affect overall power output beginning with the intake stroke.