ECU’s job

[steve_rt]

I am getting to grips with all things car at the moment before i start to experiment with engines etc.

I am looking at the ECU at the moment, and just need to make sure i understand everything it does:


Has an ignition map stored (2D on std, 3d usually if aftermarket)
Takes readings from sensors, MAP, lambda, TPS, flywheel position etc. and provides the spark at the precise instant.
Takes a reading from knock sensor (if present) and retards / advances ignition as reqd.
but uses the base map, and throtte position and engine load to give a precise fuelling value per cycle into the injector/s.
Has a learning circuit where it adapts to the engines running. Does it change the base ignition map here?
Generates fault codes if no reading present from sensors, or irregular signals etc.
Ok anything I have missed?

Steve

 

[steve_rt]

oh one other question - what are the axes (plural of axis?!) on a 2d map (throttle position and engine speed?), and 3d map?

 

[edde]

I would have though all ECU would carry a 3D map. On a diesel these would be


Revs
Amount of fuel injection
Throttle position
Also boost pressure on turbo cars is Mapped on ECU along with injection timming so that on 172 Clios full use of 98 octane fuel can be made.

I would expect that an extra dimention cannot be added to a cars ECU due to the space limitations on the chip (i.e. they could run adifferent map values but not another completly different job such as Windows or Linux) whereas a simple PC could run then.

EDD

 

[BenR]

you are correct on all instances.

ignition in 3d form is , engine speed, load and throttle position.

With most engines now they havea startup map for lean running to pass euro emissions regulations, and with lambda control (closed loop) they strive to keep the engine running near a 14.7:1 a/f ratio as this is the ratio the cat requires to operate. On high rpm and power requirements (TPS/LOAD) it will switch to eitehr open loop or preset map.

 

[steve_rt]

how does the engine detect load, and what is it measured in? or is it just given a value of say between 0 and 5?

 

[BenR]

The MAP sensor and TPS, and RPM......

 

[Frosty]

Everyone has overlooked the airflow meter (although MAP sensors can be used in place of these as well as along-side them).

 

[BenR]

not all cars have an AFM.

 

[Frosty]

Just a thought - does the 172 have an AFM - I have never looked?

 

[BenR]

The MAP sensor does that job.