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Q: 22RE w/ headers and O2 sensor performance

Last year I installed headers onto my 89 truck 22RE (california) engine. Somewhat common knowledge is that the mixture needs to be made more rich so you don't burn out vavles and pistons, so I've done that. Back in November, it was smog time. I passed but it was close. Two years earlier it was a pass with flying colors. Since then I've been obsessed with the idea of dialing this thing in for peak performance.

For several months prior to the smog, I had kept records of miles per gallon, and had changed the Mass Air Flow sensor one notch at a time to get 23 MPG, so I know I'm close, but the close call on the smog had me concerned that I might not be as close as I thought.

Now I'm playing with the O2 sensor readings as my judge. The service manual shows how to diagnose a bad O2 sensor, but doesn't explain the theory of operation, or good vs. marginal performance. I found a nice Toyota technical doc at

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that has a very comprehensive explanation of O2 sensors. Back to my truck, I test for voltage an the diag connector from E1 to O1, and find between 0 and 1 volts. At 2500rpm or so (I have no tach), it bounces from approx 350mV to 550mV, 6 or 7 times per 10 seconds. Life is good.

My benchmark road test is to drive over CA 52 from Santee to Kearny Mesa, a 5 to 6% grade for about 2 miles, and perfectly straight. I can run at

70 or 75 with wide open throttle and hold my speed in 5th. During my test run, the O2 sensor outputs ~950mV solid. I understand that the rich/lean fuel trim adjustments by the ECU do not happen during wide open throttle, but 950mV would indicate a rich condition. Is this what I want for a fully loaded engine? Is this normal? If it is over rich, would adjusting the MAF do anything, or is the MAF only for basic adjustments?

I know this is a longshot question, but if anyone has played with this to this extent, I figure the internet can find them.

Thanks,

-Bill

Reply to
Bill Paul
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I find my '85 22RE runs full rich at or near WOT according to my A/F guage. Seems to vary depending on different variables as to when it froms from closed to open loop mode. At low RPMS, you can hit WOT in closed loop mode and higher RPMs, it'll transition at 75% throttle or so. In open loop mode, the ECU runs off the AFM readings and tends to keep the engine on the rich side. The conventional wisdom is that there is no need to tweak the AFM when you add headers or do other similar mods. I did nothing to mine after installing LC Headers, a TRD Level-1 cam and a bored out throttle body. Still works fine and passes smog, although it is at higher readings than when it was stock.

Reply to
Roger Brown

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