How Car Engines Work - Not Your Basic Four-Stroke Guide - Tech

At one time or another all of us have felt the hurt of misapplied modifications. Even the most respected names in the tuning industry have been pwned at least once. Those who have moved on to make power history surely had a short and direct learning curve, but some of us never seem to learn and just struggle to make power.

Are you tired of losing in front of crowds? Does your local tuning shop guru intimidate you with quasi-scientific BS? How do you know if that ROM tune or latest Chinese knock-off tempting you on eBay is any good? What exactly is a bigger camshaft? Are you bummed out by bad surprises on dyno days or getting pwned on those forums?

Manipulating the four-stroke cycle is essential when looking for more horsepower so it's important to understand the different parts completely and how they affect overall power output.

If you fall into any of these categories, keep reading. The information is simple but it's essential for you to understand if your goal is to operate in the jargon-filled world of engine modding. Plus, if you want to go faster, you've got to understand how engines work.

Cars are, with the exception of rotaries, powered by the Otto four-stroke engine cycle. The name stems from the power cycle's four strokes: the intake stroke, compression stroke, power stroke and exhaust stroke. The cycle explains how an explosion of gasoline and air can be smoothly transferred into useable power, hurling you down that quarter-mile or just taking you to work.

Engine parts work in harmony in an exacting manner to harness gasoline's chemical energy converting small explosions of air and fuel into rotary motion. Honda aficionados can consider themselves fortunate. The company has some of the most advanced engines available for automobiles. Just by owning a Honda, you're ahead of the game.

The Block
The block contains the reciprocating components that harness gasoline's explosive properties. Pistons slide up and down cylindrical-shaped bores and the number of bores equals the number of cylinders. The block also contains cooling and lubrication passages for water and oil. Inside are main bearing saddles that support the crankshaft. Blocks are typically made of cast iron but Hondas are made of lightweight aluminum. Four-cylinder engines power most Hondas, although the Accord, NSX and various SUV types offer six-cylinder powerplants.

Pistons are basically aluminum cylinders that slide up and down the block's bores. To work effectively they require thin, circular-shaped rings that seal off the chamber and prevent combustion pressure from blowing past the piston, losing power-producing pressure.

The Pistons
Simply put, pistons are cylinders of aluminum that slide up and down the block's bores, with the top of the bores being blocked off by the cylinder head. To make driving power, a flammable charge of compressed gasoline and air is ignited within the bore forcing the piston downward toward the cylinder's open end away from the cylinder head. This is the basic premise of how an engine works.

Pistons also have rings, which are thin, circular, springy metal seals that fit inside grooves around their tops. Rings help prevent combustion pressure from blowing past the piston and losing power-producing pressure. Rings also help scrape lubricating oil off cylinder walls to prevent oil from burning inside the cylinder. Without rings, it'd be impossible to develop enough compression to run, as well as burn up all that oil in just a few minutes of operation.

Connecting rods transfer the explosion's force required to shove the pistons down their bores toward the crankshaft. The connecting rods look like metal dog bones connected to your pistons.

The Connecting Rods
Connecting rods transfer the explosion's force, shoving pistons down their bores toward the crankshaft. Connecting rods look like metal dog bones and are attached to the pistons by wrist pins-this would be the rod's small end. The rod's other end is attached to the crank. This is called the big end since the crank's journals are much bigger than the wrist pin's journals. Crank journals need to be bigger since the crank rotates at high speeds, unlike the wrist pin's simple rocking movement. This high-speed rotation requires additional bearing area to prevent the rod and crank from friction damage. The rod's big end spins smoothly on the crank's journal over a pressurized oil film and sleeve bearing-these are the rod bearings. On a typical Honda engine, the rod's small end has a bronze bushing for the wrist pin that's lubricated by oil splashing throughout the block.