Quote:
Originally Posted by CSG Mike
It reads up to 20.0 PSI absolute, but starts to get inaccurate over 19.3 PSI. The ECU will also read barametric pressure, and you need to subtract the barometric pressure from the MAP pressure, to get your actual boost pressure (but again, the MAP sensor maxes out before you hit peak boost).
Most OBD2 readers will be able to read Lambda, which is a raw voltage value for AFR. If we see 0.8-0.9 raw on that under WOT, we're happy. It's "close enough". We also read the catalytic converter temp (also available through the ECU), and that'll tell us very quickly if we're leaning out, as the temp will skyrocket past 1600F. I don't think we've ever seen it go over 1500F under hard use, and normally sits around 1100-1200F cruising, and 1450F under sustained load (going uphill, WOT, etc.)
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lambda is perfect for reading AFR , just do the calculations like mike said. I look for around .83 on WOT.
if you are really serious about boosting, i'd recommend getting an afr gauge still. simple enough, cheap enough, worth it