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mike12

3.9 running rich

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Hi Guys

can anyone shed any light on the issue i am having with ms. I go for a logging run and the afr is in the 3 4 5's i then go into mlv and run a ve analysis and then load that onto the ecu but then when i go for another run i still get the same issue.

I have checked lamda wiring and exhaust for leaks both are ok.

Thanks in advance Mike

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How are you reading the AFR? Do you have a wideband O2 sensor? Is it actually too rich (does it smell rich) or just reading odd?

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Hi just using the narrow band that was supplied by Nige. Its doesn't smell too bad for a v8 had the plugs out and they are all a light brown colour. Fitted new ones with the correct gap but have since not been back out to check. did save the new ve and load it onto the ecu.

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.... but is perfectly sufficient for tuning MS on a RV8.

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What they said, narrowband cannot measure AFR, the AFR gauge is a lie, ignore it or swap it for some other gauge. A narrowband can ONLY tell you 3 things:

Lean (<0.5v)

AFR is EXACTLY 14.7:1 (0.5v)

Rich (>0.5v)

That's it. Most of the time you probably want to be on the rich side, especially idling & under load, cruise is the time to aim for 14.7:1 using the inbuilt O2 correction. That's a generalisation but it's a fairly safe one.

o2volts.gif

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So if the AFR gauge in megatune with a narrowband is a bit of a waste is it possible to define a gauge that just gives you voltage? Would that make it easier to get an idea of where you are, or is there just too much noise on the signal.

Interested as I am going to not the 3.9 with luck next week and as its been off the road for so long the tuning will have to take place on the way to the not station as its not had a not since fitting megasquirt

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