FullThrottleV6.com - 5th Gen V6 Camaro, Firebird, Grand Prix, Regal, Grand Am and Mustang Tech Forums FAQ

Here you can find answers to questions about how the board works. Use the links or search box below to find your way around.

Info on the Intake

This is where it starts, the intake (assuming the engine is on, just hang on for a bit). The intake in an L67 consists of a rubber ducting from the throttle body to the air box. This ducting has two 90* bends, and at the air box end is a rectangular air filter. The box houses the PCM (Power train control module). As the intake draws air, sensors in the ducting and throttle body keep track of the airflow.

The throttle body houses controlled by the gas pedal (the one you scream at slow drivers about using for once), and is opened the throttle plate, and connects the intake ducting to the supercharger. The stock throttle body is 69mm’s and L67’s came sporting an Eaton M90 supercharger. The throttle plate is opened and closed, regulating the amount of air passing into the supercharger. A sensor measures the amount of air flow and relays the information to the PCM, where calculations are made regarding the amount of fuel to be used (but that’s later).

After the air enters the supercharger, it is forced into the intake manifolds by spinning rotors, the rotors are connected to the supercharger pulley through various bearings and couplers. As the supercharger pulley spins it turns the rotors. The more engine output the faster the supercharger spins, creating boost (boost is a term for the pressure of the air as it is forced into the intake manifolds, 9psi = 9 boost). Supercharger speed is also affected by the size of the pulley, as a smaller pulley will spin faster.

Info on the Combustion

When you turn the key, you activate the starter, which turns the flywheel, gets the air and fuel flowing, and fires off the spark plugs until the engine is self sustained, or you stop trying to turn it over.

When the engine is on, the alternator generates power through a spinning pulley, and charges the battery. The coil packs and plug wires send power to the spark plugs, where they spark and ignite the air/fuel in the combustion chamber.

As the air is brought into the combustion chamber, fuel is added through the injectors. The amount of fuel is determined by the PCM’s calculations. This is where it gets tricky, so bare with me. The cylinders are housed by the block, and the pistons are connected to the crankshaft by connection rods. At the top of the block, are the heads, which house the valves and spark plugs, and cap off the cylinders. As the crankshaft turns, it moves the pistons up and down. It is also connected to the flywheel, and also turns the camshaft. The camshaft spins at ½ the speed of the crankshaft. The camshaft is made of lobes, and the lobes move the valve train assembly (which consists of springs, rockers, pushrods, and valves, and various retainers and seals), and the valves move up and down. The intake valve lets in the air and fuel, the piston moves up creating heat and pressure, then the spark plug fires off, the mixture ignites and drives the piston back down, this action spins the crankshaft, and allows it to be self-sustaining, because as some pistons are being driven back down other pistons are being turned up, this is because of the crankshafts indescribable shape, but if you see a picture of one you will understand how it works. The order the pistons move in is called the “Firing Order.” After the combustion the exhaust valve opens and the mixture exits the combustion chamber into the exhaust manifolds.

It is probably a little easier to see how things work now, the crank spins, the cam spins, the supercharger spins, the alternator spins, all these things powered through rotation are all connected through belts and chains, and the action of the pistons rising and being forced back down is what keeps them spinning, and keeps the engine running. The thousands of micro-explosions that occur to keep this going are just a matter of some air, a very tiny amount of fuel, and a spark, kind of cool isn’t it?

I mentioned that the crankshaft is connected to the flywheel; well this is where the first horsepower rating is found. When you see advertisements on TV or in a magazine for cars, or maybe some uneducated ricer bragging about the power gains from his Wal-Mart intake, they will say something like “240 horsepower.” This is crank horsepower, and it doesn’t matter for crap, because not all of that power can get to the wheels, it is lost in the drivetrain. The rule of thumb is a 15% loss in power, so for estimates you can use this formula, .85c = w where c is crank horsepower and w is wheel horsepower.

Info on the Drivetrain

As the crank is spun, it spins the flywheel; the flywheel is connected to the input shaft through a torque converter. The torque converter is what engages and disengages the transmission in an automatic car. The input shaft is connected to the transmission, something I won’t even bother to explain other then it is a maze of gears. After the transmission, is the output shaft, which enters the differential, which perpendicularly connects the output shaft and the axle. The axle goes to the wheel/rotor assembly and spins them.

This is where the second horsepower reading is found, and this is the one that matters, because this tells you just how much of that power is getting to the ground, where it makes the car move forward (or backwards). The only true way to get a horsepower measurement is a dyno.

Info on the Exhaust

After the exhaust valve opens and lets the combusted gas out, it enters the exhaust manifolds, where the 6 little streams become one, and exit the engine bay through the downpipe. There is an o2 sensor where the two manifolds meet, which takes a reading of the raw exhaust. The downpipe enters the catalytic converter, where the exhaust is processed. After the cat there is another o2 sensor that takes a reading of the clean exhaust, for emissions reasons and to monitor the cat. The second o2 sensor is protected by a “u” in the exhaust called the “u-bend.” The downpipe splits into two smaller pipes at the point called the “y pipe.” Those pipes then enter mufflers, then into the exhaust tips which are at the end of the car. A resonator is also in the exhaust for sound reasons.

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