FCD to offset upgraded injectors?

[scottzg]

Ok, so I've never had a sophisticated turbo car, and im more of a solder monkey than an electronics genius, so ive probably have an half baked idea here; bear with me.

From my understanding, there is several types of FCD's. The most popular one is one that matches the stock pressure output voltage to a point, at which it just keeps reporting the same pressure regardless of the actual boost pressure. It has its problems, whatever.

The one im thinking of is the one where it reports a percentage less than actual boost. So like at 6 psi it will report 4 to the ecu and at 12 it will report 8 - you always run lean. Now, if you had one of these with a gain control, and increased your fueling by the same amount, via upg. injectors or altered fuel pressure, you could have the 2 cancel out and have pretty accurate fueling.

Is this already common practice?

[vrg3]

It is done sometimes on cars with speed density engine management. It's super ghetto, though, because manifold pressure isn't directly proportional to airflow.

But our cars use mass flow engine management.

[-K-]

I think the MAF sensor reading is used the most for fuel calculation.

[free5ty1e]

Yeah, I think the MAP sensor is just there to sense when to pull fuel. MAF sensor is the main one used to figure out fueling, with the help of the O2 sensor in closed-loop mode for trims.

You could put your gain control / pot on the O2 sensor, I believe we've discussed this before... it could allow for very slight trimming if done properly but again it's pretty ghetto. (like I have room to talk, look at my car lol)