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The Intake System
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| This SR20DE O2 induction intake manifold makes big power on a turbo SR. |
The intake system consists of the manifold which basically is a series of pipes that connect the throttle body, which is the valve the controls the amount of air that can reach the insides of the engine, to the intake ports of the head. The throttle controls the amount of air the engine can suck in, thus controlling its speed and power. When the throttle is shut, the air is very limited so the engine must idle. When it is wide open, the engine takes in all the air it can so it can produce its maximum level of power. The manifold usually contains the fuel injectors which are electro-mechanical valves controlled by the ECU, or engine control unit, a small computer which is the engines brain. The ECU controls the amount of fuel being injected into the engine by modulating the open and closed time of the injectors. Under cruise or light throttle conditions, the ECU maintains the proper stoichiometric ratio of air and fuel for the emissions controls, mainly the catalytic converter to work efficiently. When the throttle is fully opened, allowing the maximum amount of air possible into the engine, the ECU will command the injectors to stay open longer so they can inject a proportionally greater amount of fuel to create a bigger volume of explosive fuel-air mixture. More fuel –air mixture means a bigger explosion and more power.
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| The Skunk 2 4G63 intake mainfold is goood for quite a bit of power. |
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| The WORKS 4G63 throttle body on the left is much bigger than the stock part on the right for more flow. |
The Ignition System
To get the fuel air mixture burning, the ignition system ignites the flammable mixture by firing a powerful electrical arc across the electrodes of the spark plug. The engine’s ECU controls the timing of this spark. The spark is fired as the piston has almost risen to Top dead Center (TDC) near the peak of the cylinders highest compression. This is the most efficient time to fire the spark. Usually the timing of the spark advances as the engines RPM increases. This is because at higher RPM there is less time for the combustion event to take place so it must be started sooner in the cycle to maintain proper operation.
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| Spark plugs screw into the head and the electrodes protrude into the combustion chamber. The spark is created at the electrodes and starts combustion. |
