Originally Posted by popatim
Am I correct in assuming that you're running lean and the pcm is at the max rich limit? hence the need for slightly bigger injectors?
Also, whats the purpose of the wideband O2. How is it different than the normal O2 sensor. olet me know if these questions should bein their own thread.
Thanks - Tim
It'* not that simple. Fueling changes across the band whether you're under load or not, throttle position, etc.
At WOT I'm SLIGHTLY lean, depending where in the RPM band I am. In GENERAL, I'm a tad on the lean side across the board, even though I'm running about 20% higher fuel pressure than stock (almost 4bar, 3bar is stock) and feeding it from a Walbro fuel pump.
The Walbro can keep up with FLOW just fine. It'* outflowing the demand by at least 30% or so. Probably more. It can support 400hp or more. The injector change will allow the PCM to get back into the 'range' it needs with slightly larger injectors running at a slightly lower pressure. My target is 3.5bar. The higher pressures have the added benefit of greater atomization of the fuel. That'* efficiency and power.
Again, the GOOD news is that the slightly lean condition seems to be fairly linear (or EVEN/EQUAL) across the board. This makes it very easy for me to adjust for the condition using HARDWARE. Fine-tuning can happen later with a custom burn, and I can log wide-band data to nail it down. I now have all the diagnostic tools I need for a correct burn.
Wideband O2'* look at a wider band than stock. OEM sensors don't have to be looking at a wide window, as they're selected for specific constants like known demand, stock MAF tables, known fuel pressure, etc.
At a certain point in modding, you start to get out of these 'constants', and they have a somewhat cumulative or interrelated effect. I'm finally to the point where I need to make hardware changes to counteract it.
The rule of thumb that I mod by is to fix as much as you possibly can MECHANICALLY before you resort to tuning. You get a much more stable and predictable machine that way.