Hi everyone,

I'm trying to understand how the Delphi DDCR diesel ECU works in order to do a proper tune on it but I came across something very weird and despite all research I've done, I can't find a logical explanation.

I compared two dumps from Renault 1.5 dCi engines (K9K), one from the 82bhp and the other from the 100bhp. I am 1000% sure these engines use the same injectors, I checked multiple times using the official parts catalog.
But when I compare the map which defines the injection pulse length from the 82bhp and 100bhp, they are completely different!

It's very strange because for me, the injection pulse length is directly tied to the injectors physicals characteristics...
So, did any ever seen something similar? Or even better, maybe someone as an explanation because despite all my efforts I don't understand why this has been done this way!

Any help will be very much appreciated, thanks for your time!

From my quick research (meaning I may not have all the details), the dCi motor is common rail. By adding longer injection times/pulse length (duration), you add more fuel, increasing possible power output. If all the other components are the same, I assume timing will also be different also. Likely advanced a few uS to compensate for the additional injection duration.

Similar to gasoline engines, you would vary the pulse length to get different amounts of fuel from the same injector. When increasing power, there's a limit when the injector is open too long or for the entire length of the injection window and you need to either increase fuel pressure (to push more fuel through the same size holes) or get injectors with larger holes. The trade off is lower pulse length performance. It takes time for an injector to open, so there is a minimum amount of fuel an injector will supply as well.