modern fuel injection for dummies
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  1. #1
    Rods 'n' Sods Junkie tony lewis's Avatar
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    modern fuel injection for dummies

    i'm the dummy!! ever sincepassing my test many many years ago have always been smitten by old cars therefore have never owned a modern one as time goes on now its gettin more and more apparent that im going to need to put a modern engine in my ride can someone please explain to me how they work or if i can get one to work on carbs will i still have to get a ecu to work the ignition? im a bit confused about it all?

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    Official RnS Addict Cragarsarecool's Avatar
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    Sent you a PM!
    The Original Terry Fuckwit...

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    Official RnS Addict THE VIKING's Avatar
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    Quote Originally Posted by Cragarsarecool View Post
    Sent you a PM!
    Why dont you post your reply on the board as we all need to learn about this fuel injectoin and electronic engine magnegment

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    Col
    Heavy Oiler Col's Avatar
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    Depends on the engine you use. The earlier (efi) injection engines had more conventional ignition systems and the efi bit was "standalone" (early efi rover v8 ) Nowdays ignition is intergrated into the system- You don't even have distributers now, you have coil packs instead. Timing is by crank trigger.
    The easiest way of using a modern engine is to buy a scrap doner car and take out the engine wiring loom and ecu's and put the lot in whatever car is to receive it. The problem is most modern set-ups don't work well on modified engines so radical cams will give you grief. If you want to modify the engine, then Accel, F.A.S.T, holley etc make aftermarket ecu's and systems which would make the system more tunable -usually through a laptop.
    Last edited by Col; 11-03-2010 at 10:59.

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    Rods 'n' Sods Junkie tony lewis's Avatar
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    Quote Originally Posted by THE VIKING View Post
    Why dont you post your reply on the board as we all need to learn about this fuel injectoin and electronic engine magnegment
    I agree not all of us are as tech minded as most guys on here but we're all willin to learn if one of you guys can do a how it works thingy on tech features it would be really usefull to those of us who are pickin stuff up as we go and arent neccesarily in the "motor trade". hope you can help

    by the way i'm not totally useless am fairly handy with a mig .

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    Rods 'n' Sods Junkie
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    The Haynes book by Dave Walker, Engine Management is well worth a read.

    http://www.haynes.co.uk/webapp/wcs/s...1025&langId=-1

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    Rods 'n' Sods Junkie tony lewis's Avatar
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    Quote Originally Posted by FlatheadFordV8 View Post
    The Haynes book by Dave Walker, Engine Management is well worth a read.

    http://www.haynes.co.uk/webapp/wcs/s...1025&langId=-1
    that looks just the job matey thank you so much was startin to feel a bit of a numpty compared to other people on here but that sounds like just the thing for a bit of self education thanx for your time and effort mr flathead

  10. #8
    My name is Martin 30psi's Avatar
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    I can give you a basic understanding.

    The ECU is just a basic computer. It simply looks at a set of different tables and using these figures creates outputs that give you a spark at the right time and opens up a fuel injector for the right period of time to give you the correct amount of fuel. These tables are what's known as a 'map' and setting up these tables and tuning them is know as mapping.

    In order to rattle out the spark and fuel the ECU needs to see a few things on engines with sensors. These inputs are then pointed towards the map and these will pull out an output.

    I'll start with the inputs:

    Crank wheel and crank angle sensor:

    This tells the ECU 2 things. The engine rpm and where in the engine cycle it is. It's a toothed wheel sat on the crank. A tooth is missing which identifies TDC, or you tell the ECU how far away the missing tooth is and then the ECU does the rest. The ECU has no clue what stroke the engine is on. Usually made up of 36 teeth with one missing (known as 36-1).



    Cam position sensor: This is actually excluded on most aftermarket and some OEM ecu's. It points at the cam and tells the ECU whether No.1 is on it's induction or power stroke etc. Without it the ECU doesn't know which stroke.

    MAP (Manifold Atmosphereic Pressure) sensor: This tells the ECU how much vacuum the engine is under. Or boost for the cooler kids. It helps the ECU understand the density of the air entering the engine and consequently help it calculate the right amount of fuel to chuck in. 0.5 bar of vacuum requires half the fuel, 1 bar of boost will require twice the fuel. There's normally a table in the map which is used to provide the adjustment.



    Air temp sensor: Again similar purpose to the MAP sensor. The temp is referenced to a table and if the air is cold it's denser so a richer mixture is needed. If the air temp is really high you may want to throw in more fuel and retard the timing on say a turbo car, helping avoid detonation.



    Water temp sensor: Yep, it relates to another adjustment table. Used mainly for cold start where you will want a higher rpm, more fuel etc.

    Throttle Position Sensor: This is used to identify 2 things. Main one is the engine load and is used in the very basics of the map. It's also used to do the accelerator pump effect. e.g if opens quickly the ECU knows and on another table you can set up how much extra fuel is thrown in at that moment.



    Lambda sensor: Kind of optional but used on whats called 'closed loop' to help the ECU dial in to a 14.7:1 stoichiometric a/f ratio. Screws in the exhaust and measures oxygen



    Gonna get a drink and I'll bore you with what the outputs are and then explain some maps

  11. #9
    My name is Martin 30psi's Avatar
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    Once the ECU gets readings from the above sensors it then does two main jobs. Provide a spark and open up the injectors for the right amount of time.

    Outputs and other hardware:

    Fuel pump: Sounds obvious, it is, but they can be controlled by the ECU. You don't want the fuel pump running all the time with the ignition on, so let the ECU turn it on once you start cranking the engine. Normal pressure is around 2.5 bar.

    Fuel injectors: There are 2 main types, high and low resistance. V=IR, so low resistance demands more current, so most aftermarket ECU's prefer higher resistance injectors. You can use resistors though with low resistance injectors.



    Fuel pressure regulator: The ECU assumes that the fuel pressure at the injector nozzle is a constant so the regulator disrupts the fuel returning to the tank. Engine vacuum/boost increases or decreases the pressure to suit.



    Air valve: Basic ECU setups normally don't have these, but it you want a nice cold start and idle they can help loads. It's a throttle bypass valve. It will open up a bit on cold start. It's the IAC on this diagram:



    Coilpack: Very typical for aftermarket system is the use of the Ford EDIS coil. This is where I refer to the cam sensor earlier. Without one the ECU has no clue where in the cycle the engine is. On a 4 pot, it knows that either of 1&4 and 2&3 are doing either of inlet/power stroke or compression/exhaust stroke. So what you have is a spark per cylinder for each crank turn. Yep it's weird, but is know as a wasted spark system. The wasted spark is on the end of the exhaust stroke. 1&4 and 2&3 will spark together. The ECU runs the injectors all simultaneous on these setups.
    If you have a cam sensor, then the ECU can run a spark to each plug in the normal manner. If need be this can be done via a distributor and a conventional coil. A cam sensor will allow the injectors to run sequentially too.




  12. #10
    My name is Martin 30psi's Avatar
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    There are 2 parts to a map. Fuel and ignition.

    Here on this map for fuel, recorded on a table, is the opening time for the injectors. This is in millisecs. It is based on RPM and the throttle position/MAP. See here it's shown both graphically and numerically:



    Ignition is rather similar



    Engine load can be determined either by the throttle position or from the MAP sensor.

    In terms of the other tables, there can be many but here's an example of what the water temp can adjust:


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