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Introduction to Engine Tuning: What is EFI?

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What is EFI?


00:00 - Before we talk about EFI or Electronic Fuel Injection, we need to go back a few steps and find out what we're really trying to achieve when it comes to engine tuning.
00:12 Getting the best out of any engine, requires us as tuners to supply the correct amount of fuel to match the amount of air entering the cylinders.
00:22 Once we have the correct amount of fuel and air inside the cylinders, we next need to ignite it at the right point in the engine cycle.
00:32 Of course with modern engines with variable cam control, electronic throttle control and perhaps variable valve lift, there is a lot more to consider too, but fuel and ignition are still the two key aspects that we as tuners need to control and optimise.
00:53 If we rewind perhaps thirty to forty years, the main way of achieving these aims was thanks to a carburetor to supply the fuel, and a distributor and coil to provide the spark.
01:06 This got the job done, but didn't offer a lot of precision or control over either.
01:12 The drawbacks of the carburetor are numerous, however the real nail in the carburetor's coffin was the poor emissions control.
01:21 An inability to precisely control the fuel delivery, coupled with a tune that varies based on atmospheric conditions, meant that the carburetor didn't have a fair fight as emission standards have become increasingly tighter.
01:36 EFI on the other hand uses an ECU, or Electronic Control Unit, to control the engine operation much more precisely.
01:47 EFI's biggest advantage is the processing power and flexibility that comes from using a computer to control the fuel and ignition.
01:58 We start with a range of sensors that tell the ECU how fast the engine is tuning, how much air is entering the engine, and what the atmospheric conditions such as temperature and pressure are.
02:12 The ECU can then process the data from these sensors literally hundreds of thousands of times every second and decide exactly how much fuel to supply and what ignition timing to deliver.
02:27 Even at extremely high RPM, the ECU can process all of the sensor data and make decisions on fuel and ignition before the crank shaft has even rotated through half a degree.
02:39 Such is the speed and precision of EFI.
02:44 Now as well as these inputs, the ECU also needs a way of delivering the fuel and spark.
02:51 Fuel injectors are in charge of the fuel delivery and you could think of these as a solenoid that the ECU controls.
02:59 When the ECU opens the injector, fuel is delivered is delivered in a finely atomized mist into the engine.
03:06 Due to the design of the injector, and the speed of the ECU's operation, it's possible to very accurately control the exact amount of fuel being delivered.
03:17 The spark on the other hand is delivered by the ignition system, which can vary from one engine to the next.
03:24 In perhaps it's simplest form, we may still see the old familiar distributor and coil, however, this time the ECU controls when the coil fires and delivers the spark.
03:36 In more modern engines we're more likely to see a coil on plug arrangement where a separate coil is fitted to each cylinder.
03:45 Regardless of the actual design though, the ECU can constantly adjust when the spark occurs as the engine speed and load change.
03:55 So where does all this help us out? Well, firstly we have much more control over the fuel and ignition timing being delivered to the engine.
04:05 This can over more power, more torque, better drivability and better fuel economy.
04:12 Just as importantly though, since the ECU can account for changes in atmospheric conditions, we can expect a consistent tune from one day to the next regardless of temperature or air pressure.
04:27 And the real key from a manufacturer's perspective is that it allows them to make the all important emissions standards.