Mapping

[Edb]

Newbie question I know - but when someone says that the engine needs to be mapped, what does this mean?

Cheers

Ed

[Blatman]

Have a read of this

You can ignore the emissions regs stuff, as Westfield owners mostly convert to fuel injection to optimse control of the ignition timing and fuelling. In our case, good emissions control is the happy by-product of a sweet running engine.

[peterg]

If you have an engine management system (such as Emerald, DTA, Weber Alpha etc.) then they need to be setup so that the fuel/air ratio is correct at idle/midrange/full throttle etc. and so that the ignition fires at the correct time and for injected cars they also decide when the injectors squirt the juice as well  

They normally have sensors for ambient intake air temperature and throttle position and basically replace the coil/distributor function  

[Edb]

If you have an engine management system (such as Emerald, DTA, Weber Alpha etc.) then they need to be setup

So it's just software changes then?  Don't any mechanical engineering things need to be done?

Ed

[Nick M]

Actually mapping is a bit more involved than setting up the air fuel ratio at idle, mid range and full throttle.

What you're aiming to do is to create a "map" (imagine a 3 dimensional graph) for the ECU so that for any given throttle opening (determined by the throttle pot), engine speed (determined by the crank sensor) and air temperature (determined by, guess what, an air temp sensor !!   ) the correct amount of fuel is delivered (the map determines when the injector opens and how long for) and the spark is triggered at the right moment.  

Typically you would have a "site" on the map every 250rpm or 500rpm for every throttle opening.  For example, at 2,000rpm and zero throttle angle you'd have one site.  At 2,000rpm and half throttle you'd have another site and at 2,000rpm and full throttle yet another.  Then you'd do the same at 2,250rpm, 2,500rpm, etc., etc.  Obviously there are lots more sites for the throttle angles that get built into the map, as well as the way the throttle is opened, i.e. gently or suddenly.

Once you've mapped the fuel delivery you then need to go back and do it all again for ignition timing (in practice it's done at the same time).  The "maps" for fuel and ignition then combine to allow the engine to run in the most efficient way.

An ECU doesn't replace a coil - it's simply the brains behind the outfit.  You still need a coil to create the spark with full engine management - either one big coil pack or one for each cylinder.  You can, however, sometimes do away with the distributor and allow the ECU to tell the coil when to trigger.

So yes, mapping is all about software - it's the process of creating the instructions which the ECU then delivers to the mechanical bits of the engine.

[steppenwolf]

A picture paints a thousand etc etc etc ...

The following is a view of part of the Fuelling Map for my Zetec 1800. The 250 increments are RPM and the 0-15 increments represent the opening of the throttle as measured by the Throttle Position Sensor (TPS) - the higher Site number, the wider the throttle is open. The numbers in the matrix represent the number of milliseconds that the fuel injectors are kept open for at any particular mix of RPM and TPS.

This next picture shows a graphical view of my complete fuel map. The red graph is how it was mapped when I got the kit from the factory and the green graph shows how it is now that I have mapped it to suit my own requirements and get the engine running at it's best:-

Hope that helps you to understand what a map is ...