[align=center][/align]Electronic Engine Management, Part 1
It's good to have an idea of how the engine management system works before you start modifying the engine!
By Julian Edgar

All engines require that the combustion air and fuel get mixed in the right proportions, and that each cylinder's spark plug is fired at the right time. Those are very important points to remember because it's easy to lose sight of these basics when making modifications or considering complex engine management systems.
Remember: it all comes back to:
[ul][*]how much fuel [/ul]
[ul][*]and when does the spark fire. [/ul]


[/align]The amount of fuel that is mixed with the air is described as the air/fuel ratio. A 'rich' mixture (like 12:1) uses lots of fuel and is good for power, while a 'lean' mixture (like 17:1) uses less fuel and so is more economical. The 10:1 air/fuel ratio shown on the meter here is very rich indeed! The ignition timing refers to point during the rotation of the engine's crankshaft that the sparkplug fires. This needs to vary because at high revs there is less time available for combustion to occur, and so the spark needs to start the burn earlier. Changes in timing are also needed at different engine loads, different temperatures and on different octane fuels.
Quick Overview


[/align]The first part of an engine management system is the fuel delivery system. This starts off at the high pressure fuel pump (pictured) that is mounted in or near the tank. The fuel line from the pump passes through a filter before it runs forward to the engine bay. The fuel line connects to a fuel rail that feeds each of the injectors. At the end of the rail is a fuel pressure regulator, with surplus fuel heading back to the tank in the return line.


[/align]The air supply system starts at the airbox. A pick-up collects air from the atmosphere and channels it through a filter. From there the air heads off to the engine. On some engines, an airflow meter is located close after the airbox. The throttle body (butterfly) controls how much air enters the plenum chamber. So that idle speed can be regulated, there is a bypass around the throttle body. The amount of airflow flowing through this bypass is regulated by a computer-controlled valve, which here can be seen on top of the throttle body. Once into the plenum (the aluminium box in the engine bay), the air is distributed evenly to each intake runner, flowing down the runner to the intake valve. Just before the air reaches the inlet valve it meets the squirting fuel injector. The air/fuel mixture then passes into the combustion chamber when the valve is open.
The electronics system of the engine management uses sensors. Many times each second they tell the computer what's happening to the engine. The computer is the brains behind the system, and in most cars it is called an ECU - an Electronic Control Unit. It is programmed by the factory to give the right outputs when it receives the right inputs. One example of the outputs it controls are the injectors.
The Inlet Sensors
In order that the ECU makes the right decisions about how much fuel to inject and when to fire the spark, it needs to know precisely what the engine is doing. Is the car at full throttle up a long hill at 3000 rpm o

 

nice find space man!!
thanks

 

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Quote:

ORIGINAL: mickey

nice find space man!!
thanks

[/align][align=center][/align][align=center]Your WelcomeModerator `Mickey[/align][align=center]I liked the way the article was written...I could even understand it : )[/align][align=center]I keep learning something everyday. I wish there was a post to contain information[/align][align=center]like this on the forum for new members to read and understand.[/align][align=center]Engine Management is really getting more high tech every year & model.[/align][align=center]It's not easy to mod a modern day engine : ([/align][align=center]I'm glad you appreciated the article. I hope that more members post[/align][align=center]information that will assist and help other members.[/align][align=center][/align][align=center]Peace Out[/align][align=right][IMG]local://upfiles/714/B55F3016E58E4A8696CF8097AA037DAD.gif[/IMG] [/align]

 

Engine Management Systems, Part 2
In addition to determining the injector opening time and the ignition timing, the ECU also controls idle speed and other factors.
By Julian Edgar & Spacce : )
The most important components that the ECU controls are the injectors. The amount of fuel that flows through the injectors is determined by the length of time that the ECU switches them on for. The time that they are open for is called their pulse width. When they are on, fuel squirts out of them in a fine spray. While it varies from car to car, the injectors in many cars pulse on for a single very short squirt each two rotations of the crankshaft. If more fuel is required, the injectors are switched on for a longer time period. The pulsing on and off of the injectors is the clicking noise that you can hear if you listen really closely to an injected engine.
The percentage of time that the injectors are open for is called the duty cycle. An injector open for half the time has a 50 per cent duty cycle, while if it's open for three-quarters of the available time it has a 75 per cent duty cycle. At max power in a standard engine, the injectors might have an 85 per cent duty cycle. That means the injectors are flowing at 85 per cent of their full capacity. A good quality multimeter can be used to read off the injector duty cycle by back-probing the injector plug when it is connected to the injector.
[/align]It's when modifying an engine that the duty cycle and flow capability of the injectors becomes very important. For example, adding an aftermarket blower means that the engine will breathe a lot more air. Because of this, extra fuel will need to be injected if the right air/fuel ratio is to be maintained. But are the injectors big enough to do this? The maximum injector flow occurs when the injectors are held open all of the time. This is the same as saying that when the injector duty cycle is 100 per cent, that's as much fuel as you're going to get (at that fuel pressure). If more fuel is needed than the injectors can flow even with a 100 per cent duty cycle, larger injectors should be fitted.
[/align]We'll be covering the modification of factory engine management systems a bit later, but here's an easy example of how to overcome the problem of injectors that are a little too small. If the budget doesn't stretch to larger injectors, an increase in fuel pressure will squeeze slightly more fuel through the standard sized injectors (and standard opening times!). A pressure regulator that performs this function is called a rising rate fuel pressure regulator. It increases fuel pressure by an increasing amount as boost is sensed in the inlet manifold. For example, fuel pressure might go up three times as quickly as manifold pressure. However, increasing fuel pressure isn't as good as fitting larger injectors and then making the required ECU modifications - but it's a lot cheaper!
[/align][b]In most cars, the ECU doesn't directly control the ignition coil. Instead, an ignition module is used to switch the power to the coil on and off. The ECU tells the ignition module exactly when it needs to do this switching so that the s

 

[align=center][/align][align=center][/align][align=center][/align][align=center][/align][align=center]If you're a car guy or gal you may already have the very common yet unfortunately incurable performance affliction. Be it new or old, big or small, car, truck, minivan, or even an SUV, you can't leave well enough alone. You want your ride to go faster, handle better, stop quicker, sound cooler, and look better than it did when it left the factory—and you'll get it there by any means possible. Like the old saying goes: Speed is just a matter of money—how much do you want to spend? [/align][align=center][/align][align=center]If you had the all the money in the world the answer to that question would be a no-brainer. As fast as possible! While this is an easy order if your name is Donald Trump or Bill Gates, if your bank statement is closer to reality you'll likely want to squeeze the most performance possible out of your dollar. Remember that if for some reason you don't have this common performance affliction, it's never to late to get started with upgrades and modifications you can do yourself! [/align][align=center][/align][align=center]One of the easiest and most popular ways to increase engine performance is to simply open the front door and let in more air. Since the engine under your hood functions essentially as a giant air pump as it revolves round and round, letting more air in simply helps make more power. Increased airflow means more air and fuel flows into the cylinders. [/align][align=center][/align][align=center]While a performance air filter can be an effective upgrade, further performance gains can be realized if the entire intake system is replaced. Since engineers at the factory design modern intake systems to be a compromise between quiet operation and optimal performance, the tradeoff in installing a performance air filter is an increase in engine noise. With all the air baffles and silencer tubes removed, the engine will finally be heard! [/align][align=center][/align][align=center]Don't expect massive horsepower gains from an air filter upgrade alone. Do expect improved throttle response, a bit more power, beautiful engine music, and the ability to clean and re-use the air filter many, many times. There are a world of filters and intake kits out there for almost every vehicle on the planet and most every last one of them can be installed with basic hand tools. [/align][align=center][/align][align=center]Just as air enters the engine, it must exit. If more air is coming in, it needs a bigger route out. In this reciprocal relationship, the faster air can exit, the more can come in. And so it goes. [/align][align=center][/align][align=center]Right along with brake pads and discs in the going-to-have-to replace-them-anyway department are the tires and suspension components like struts, shocks, and springs. [/align][align=center][/align][align=center][b]Nothing can affect the handling and performance ability of your vehicle like the right, or wrong, set of tires. The caveat here is to do your research. While a softer compound tire will grip the ground like a gorilla, the soft rubber will also wear out faster. An ultra-high performance summer tire will turn hard as a hockey puck in winter temperatures, and slide across the ice just like one too. A tire with a stiff sidewall will improve cornering but give a stiffer ride. The

 

 

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