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Old 20-02-2005, 04:07 AM
PuntoRex PuntoRex is offline
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Join Date: Mar 2004
Location: Taiwan
Posts: 75
Default Questions on Stock ECU (Motronic M2.7)

Hello there,

I've done the fuel injector upgrade lately & found a strange thing.

The stock injector is 240cc/min, new one is 330cc/min. At the beginning, I tried to add an interceptor to alter the MAF signal, thus alter the fuel injection accordingly. Then, I found the interceptor didn't work on my car. Shifting up or down the signal voltage did nothing to the fueling behavior.

I got only an O2 signal gauge & a rough IDC display to watch this.

At idling or light load, the O2 signal oscillates as it should, & the car runs fine. When WOT to high rev, it stays high (rich) also as it should & the IDC reduces from 80% to 60%. The interceptor did nothing to alter these behaviors. ( and of course I did not make huge/silly adjustment to the signal )

Under close loop, I believe the stock ECU can adjust the fueling properly & run fine, but how about open loop?

I've always been told, & reading on the web or books that when open loop, the fueling is based on the flow (load) signals & a built-in map while ignoring the lambda reading.

If so, why can my ECU adjust itself to adapt the bigger injectors? ( IDC drop proportionally at WOT & with an identical fuel consumption in one month's observation )

Can it be possible that the ECU is always in sort of close loop & never let go the lambda reading? (but the stock O2 sensor is a narrow band)

I found this on the web and it says: ( on the last second page )

"Two factors are responsible for oxygen regulation:

1. The integrator regulates without delay.

2. The block learn function adapts the regulator to long term changes, as for example those which occur due to running in and aging of the engine, density and changes in quality of the fuel, air leaks etc.

Block learn function 1 is effective during idling.

Block learn function 2 is effective in the partial and full load phases. "

This is not directly for my car, but it's the same ECU 'version'.

According to above, 'learning' function is working in patial & full load as well. Dose this mean more or less this ECU is always watching lambda reading, so it can adapt itself to the outer changes like bigger injectors?

Is this a really "smart" ECU, or that I misunderstand all these?

Any thoughts or any experiences?
'97 Fiat Punto GT
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