crownaviation
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I've seen it get to 10s during a wot, sometimes stays low-high 11s. It's really laggy too but I guess that comes from it still having cats on the car with the wideband being stuck in one of the cats in the rear 02 sensor spot.
idle is around 14.6, but sometimes when I start to take off I see it jump to 16s for a very split second. Really scary, is I've seen it jump to a 17.2 one time while starting to take off from a stop too. Not punching it or anything, and not sure why.
The higher the number the leaner it is. It is fine to see the afr jump to even peg the gauge when you let off the gas etc.. this is actually normal. The gauge will wonder around under normal driving.. also ok. Steady idle ill be around 14.7 or real close (will likely jump around a bit too but more stable at idle).
WOT is where it matters. Normally you should lift if you do not see the gauge go below 12 really soon after wot. With the smaller blower you may get away with a bit more (leaner is more power but risk of detonation and your m90 makes a ton of heat). You do not want it too rich either. If it is in the 10's you are way too rich and causing other problems. Normally tuners will seek around 11.2-11.8 on a blower setup but there are variables. Get a good tuner and let them walk you thru it.