But how would it increase the duty cycle to accommodate it? ECU has no fuel pressure sensor, O2's only work at low revs/load and not when your injectors will be at a high duty cycle. From my understanding the injector duty cycle is run off TP and revs only. If the fuel pressure is low the ECU won't know and will just keep on doing things as usual.
My understanding is the low fuel pressure causes the maf voltage to be lower than it should be at a given throttle % and load. This increases the pulse width to get the engine into the ecu's predetermined parameters for that load point, ie tp scales for timing and fuel. I also thought the O2's were always referenced but not necessarily used for afr. Sort of the ecu's way of watching itself.
So you mean the low fuel pressure creates a poor combustion and hence less air is being drawn in? I can't see how the fuel pressure would have any bearing on the MAF voltage. Doesn't make sense to me that the TP would be increased if the MAF voltage is lower either. It all sort of seems backwards. Do you know the exact parameters that the TP is calculated from? I haven't seen anything about this in my travels. Everyone just seems to say "it is what it is, just accept it". O2's may always be monitored, never really looked into it. I know in my VH there is a error code for leaking injectors which is monitored by the O2's, so a possibility for sure.
The TP isn't increased, as you say, it is what it is. As far as I can work out, ecu uses maf voltage, coolant temp, throttle position and rpm to determine where on the VQ table it needs to be, then calculates where on the TP scale it needs to be, then spits out a pulsewidth. But there is some sort of safety there that will keep the engine with in a defined set of numbers, I think this is what it is looking at o2's for. This is a paragraph out of an article for tuning I have When incoming air passes by the MAF sensor, the sensor then sends a voltage signal back to the ecu. The ecu reads the voltage signal on the VQ Map and assigns a numerical value to the voltage. That numerical value is then multiplied by the K Value in a mathematical formula to find the proper pulsewidth need for a 14.7 AFR (air fuel ratio) *at any engine load and rpm*.
VQ map? What is that one? I thought TP was directly calculated, rather than a product of another table. And it shouldn't be aiming for 14.7 AFR outside of the closed loop points on the main map. I wish Nissan wrote a manual on how this all works
