I need a bit of help with dsmlink airflow tables

[partylikeits82]

Please bear with me as I am still fairly new to tuning. I did some searching, and I couldn't find an answer to my question. I don't know, maybe I didnt look hard enough, or maybe I'm just blind. Anyway, I am a bit confused as to what the purpose of the dsmlink airflow table is. I understand that with an afc, the purpose of creating a compensation table is to trick the ecu into thinking there is less air flowing into the engine, thus shortening up the injector pulse. In dsmlink, you can directly change the injector compensation as well as the dead time. So I am a bit confused as to what the purpose of the airflow table is, if you can use the fuel section to compensate for bigger injectors. For reference, I am running dsmlink v 2.5 with Fuel injector clinic 650s. The kid that had it before me had it tuned at 18 psi with a 14b, and it is running extremely rich. The only modifications to the fuel system are bigger injectors. I am planning on a bigger fuel pump and fpr, but I am just trying to get it running right at the moment. If anyone could answer my question or point me in the direction of a helpful link, it would be greatly appreciated.

 

[gofer]

Heres a good read. Air flow, fuel flow, & timing 101

 

[twdorris]

Anyway, I am a bit confused as to what the purpose of the dsmlink airflow table is.

To correct airflow?

I guess the question is really "why would one want to correct airflow if they can just crank on the fuel adjustments to achieve the same result in terms of final mixture". The answer to that is part philosophical and part engineering.

On the philosophical side of things, most people like things to make sense. They want to see airflow in their logs that matches and compares well to everyone else's logs. This greatly helps in analyzing a log file to find real problems when things aren't making sense. If everyone just cranked on a "make it right knob", then it's nearly impossible for anyone to make sense of your logs when you run into a problem that the "make it right knob" doesn't fix.

On the engineering side of things, the code inside our ECUs is designed to model the real world. The whole code base works best when everything inside the ECU accurately reflects everything happening on the outside. If you have airflow way out of whack and you adjusted for that with tweaks to the fuel table, the ECU code that does things and makes decisions based on airflow can get all confused and you start getting side effects in the car's operation. Without knowing the cause of those effects, you can easily spend hours working around hacks of sorts to make it behave as it would have if you had just corrected the airflow issue to begin with.

So that's some of the logic behind making airflow changes instead of fuel adjustments even on a system that gives you full control over fueling.

The books I mentioned in this thread are also great resources to learn about how and why the ECU does things and why a real-world model inside the ECU works so well.

Thomas Dorris