How engines work

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HE engine (gasoline-fed) described last time was based on an engine using a carburetor to deliver fuel to the cylinders. We hardly see that now on newer cars. Almost every car now has an electronic fuel injection (EFI). Even the distributor is gone. Fuel injection has been around for years. The first ones used a mechanical injection pump which was geared to the engine. EFI made the gasoline engine more economical, more powerful and gave off lower emissions. It has a computer or an engine control unit (ECU) that manages the engine functions. Air goes in the engine through a throttle plate. It has a sensor which tells the computer how wide the throttle is open through the throttle position sensor (TPS). The ECU needs to know how much air is going inside, that is done by the Mass Air Flow (MAF) meter. The ECU also needs to know the position of the pistons and the valves. A sensor on the cam shaft or on the crank shaft sends the information to the ECU. With this information, the ECU can also inject fuel to the proper cylinder and deliver a spark to have combustion. Older EFI engines use the distributor to distribute spark, but the newer ones have individual ignition coils; one per cylinder. And this is controlled by the ECU. After combustion the gases exits through the exhaust pipes where the oxygen sensor senses the amount of oxygen to determine if the air/fuel mixture is correct. If it is not correct, it could make adjustments by varying the amount of fuel or the timing of the combustion. This is basically how EFI works. Different brands, newer technology, would have different way to monitor engine parameters. So don’t go around screaming “off with the writers head” for not including other details.

Even diesel engines are getting a big help with EFI. The newer ones now are easily pumping out at least twice the power as compared to the older mechanical injection type with no electronics.

Another common feature on engines now is variable valve timing. Decades ago, you would have to change your camshaft to change the performance of your engine or increase the valve size. These changes would alter the amount of air/fuel mixture entering your engine. Or if you were on a budget, you could set your stock cam slightly advanced or retarded. But that’s it. If it was set for high-end power you could lose in the bottom-end and the mid-range. You would have to reset your set-up if you wanted to change the performance of your engine. A god send before was having twin cams; then multiple valve heads. Before EFI, having multiple carburetor set-ups were the way to go. Weber side-drafts would be the focal point of an engine. Tuning it would be a talk-of-the-town. Every driver, mechanic would have their own recipe for taming multiple carb set-ups. Being able to drive it daily and go nuts on a Saturday night would be the holy grail of tuning. Now, your cam timing can be altered as the ECU see’s fit to provide maximum power. The horsepower created by those semi or full-race ‘Saturday night’ specials, decades ago, is now under the hood of your everyday grocery runner sedans—and it gets good mileage with A/C. Here’s the icing on the cake, some of those old engines were either full-blown 1,600’s or bored out to two-liters; that are comparabIe in power to present-day grocery runners that are only 1300cc to 1400cc–stock.

But hey… that’s progress for you.


(Dave Siytangco is our resident “car doctor” who will give buying advice and expert solutions for your car troubles. Dave is certified motorhead and runs his very own car repair shop. For questions about your vehicle, please email Doc Dave at motoring@manilatimes.net.)

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