The Pontiac Fiero has some very interesting qualities, good and bad. It was built by GM in 1984 through 1988. The Pontiac Fiero was going to be a true GM sports car. It was a mid engine car as most exotic sports cars are. This means that the engine sits behind the driver. Having the engine behind the driver has many advantages in a sports car. This is why they are often used today in many kit car conversions. First the front to rear weight is usually close to 50/50 which would be a perfect balance.
Alternative fuels are continuously being looked at. Propane or LPG cars are already currently being used on buses and taxi cabs. Alcohol or ethanol can be produced from corn or other carbon based by products. Methanol is being replaced by ethanol in racing. Although it is a cleaner fuel the cost is generally higher and can be corrosive. It is already being mixed with gas in some places but only at a 10 percent mixture. MTBE is a manmade molecular chain gasoline, but has no real environmental advantage other than possibly elongating how long our oil supply lasts. The most exciting fuel is hydrogen. It can burn and only release water as a by product. The problem comes with the storage of the hydrogen. In order to have enough volume of hydrogen gas it has to be highly compressed. This is a little difficult as conventional compressors are not suited to this task. Most compressors only compress to 3000 psi, whereas 10,000 psi would be great for hydrogen storage. All cars could be converted to run with hydrogen.
A basic car’s engine can be broken down into terms that anyone can understand. The goal of an engine is simple, move the car, which is accomplished by turning the wheels. The wheels are connected through the driveline (transmission, rear end gears), which connects to the engine. The rotation comes from a part in the engine called the crankshaft. The crankshaft is connected to a straight “bar” of metal called the connecting rods. On the top of the rods are pistons, cylindrical aluminum pieces that have rings of metal around them. The rings seal them close to the cylinder bore. The cylinder bore is simply a long hole that the pistons can move up and down in. This up and down motion pushes the rods down and rotates the crankshaft. Make sense so far? Next, the piston gets it’s motion from an “explosion” that happens when it is in the top part of the cylinder bore. This makes the piston move downward very quickly. For an “explosion” to occur the engine needs two things, air and fuel. At the top of the cylinder bore, it is sealed, to force the piston down, with a cylinder head. The cylinder head also allows fresh air to come into the cylinder bore and after the “explosion” allows the used air (exhaust) to leave the engine so more fresh air can come in next time.
The variable valve timing used the best of two camshaft profiles. Some of the most common abbreviations for this are the Honda vtec and Toyota vvt-i valvetrain. Although I believe the Acura nsx was one of the first to use it. Other systems are now being used by all manufacturers. Some systems actually use two separate camshafts to benefit from low end torque, good emissions, and top end power with the other cam. The vtec uses a second lobe on the same cam with another profile. Others use a wide cam lobe with a different profile on each side of it. They then move the cam side to side. The problem with using one cam is compromise. Most single or dual overhead cam vehicles are tuned for mid range power and low emissions. This means reasonable lift numbers, but not optimal. Lift is simply how high the cam lifts the valve into the head chamber, to let air pass through it. The overlap is the amount of time that the intake and exhaust valves are opened into the chamber at the same time.
The valvetrain includes the camshaft, lifters, followers, rocker arms, pushrods, retainers, springs and valves. It determines, along with the heads, how much air can pass into an engine. Most valvetrain system are very mild from the factory. This is why alot of horsepower can normally be extracted from a mild factory setup. The cam is usually the best place to extract power and can be purchased for a reasonable amount.
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The oxygen sensor or o2 sensor measures the oxygen content in the exhaust. The more fuel placed into the combustion chamber (rich condition) the more oxygen that will be used in the combustion process. When the oxygen content in the exhaust is low, there is a chemical reaction in the sensor. This produces a higher voltage up to 1 volt. Lower voltage is for more oxygen content and can go down to .2 volts. The oxygen sensor will not work when it’s cooler than 600 degrees F. At less than this temp it displays .45 volts same being if there is a problem with the sensor. The computer will show an error (engine light)if at this value longer than what it should take to normally warm up. The o2 sensor continually shifts above and below .45 volts. If you believe the o2 sensor is bad you can test it. First run the car for 5 minutes. Disconnect only the wire running to the oxygen sensor. Then connect a ohm/volt meter with black to ground and red to the o2 wire. Set the volts to MV (millivolt) setting, the o2 should fluctuate between 100 and 1000 mv. If it dosen’t, it is not good.
The mass airflow sensor’s purpose is to measure the mass amount of air entering the engine. The mass sensor is usually located on the intake inlet running to the intake manifold. Sometimes if there is a problem with it you can tap on it gently in the electronics area, and the engine should surge. There are multiple types of mass airflow sensors. Hot wire airflow meters use a current to keep a wire at a constant temp. The heat is carried away from the wire dependent on the airflow and temp. The ptc resistor varies with temperature change, as the temp drops so does the resistance. As the resistance changes the current has to increase to keep balance. This is sent to the ecu in a form of a voltage change. Another system is the hot film. It is very similar to the hot wire mass airflow meter. It heats a wheatstone bridge board, The air moves across the board and is measured on the back of the board. The thermistor measures the change in temp and thus the airflow change. The intake air temperature sensor also contributes to this equation being that humidity can slightly throw off the density reading. A vane airflow sensor simply rotates a flap as air comes in.
