Waldig,

I read your write up on this and from what I gathered the stock regulator looks like a 1:1; 1 PSI of fuel pressure increase for every psi of boost added. This is nothing short of Nirvana for an NA car going FI if it holds true. This is also the primary difference between your needs and mine.

You have an ECU that is designed for boost and a tune to match. I take it that you are trying to add more fuel above and beyond what the ECU is already programmed for due to your pulley upgrades, etc. Thus your need for a predefined threshold so as not to erroneously add fuel where the tune and fuel delivery is a known quantity. Even if you are increasing fuel rail pressure to get more out of your existing fuel delivery system like me, the same still applies in your case.

I on the other hand have an ECU that was not designed for boost and therefore have to hide it from the ECU and from every sensor. However, I also have what amounts to full control of fuel so I'm not relying on fuel pressure alone or trying to manipulate fuel pressure to achieve my target A/F.

The AEM allows me to tweak fuel via the MAP sensor, therefore my target fuel delivery is based on injector open time and achieved flow per rpm, per psi of boost. Therefore a change in boost will simply put me in a different cell with the proper injector time for that cell.

I couldn't use your setup as it would negatively impact me unless I could reduce the threshold to zero (which is effectively what I have now). In fact, it would introduce an interesting tuning challenge based on the perspective of my starting point versus yours. Having a nice linear fuel delivery based on manifold pressure is 100x better in my case as it is readily predictable.

The reason I would employee the 1:1 by adding a boost signal is to get more from my stock fuel pump and SRT injectors to support my ultimate power goals.

All things considered, I couldn't ask for anything better!