My bud just put an air/fuel gauge on his B16 Del Sol...on startup it shows that it's running rich as all hell...then as it warms up the gauge flips from lean to rich and back and forth at warp ****** speed...so my question is this: is the gauge reading wrong, or is this what is actually going on?

 

air fuel gauges only read when the ecu is in closed loop because there wired to the 02 sensor and when in open loop the ecu has pre determined fuel maps and doesnt take reading from the 02. You want accurate readings get a exhaust temp gauge.

 

I have a chip that does not use open loop. My AF gauge varries a little but its no light show. Mugen chip

 

Are you sure you don't have that backwards? The engine is not in closed loop very much, really. Start-up and time out, cold engine op, decel, and moderate to heavy accel are all performed in open loop.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Quantum_CRX &raquo;</TD></TR><TR><TD CLASS="quote">I have a chip that does not use open loop. My AF gauge varries a little but its no light show. Mugen chip </TD></TR></TABLE>

 

Maybe, I get closed and open loop confused all the time. You know what I mean though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Taiyed &raquo;</TD></TR><TR><TD CLASS="quote">My bud just put an air/fuel gauge on his B16 Del Sol...on startup it shows that it's running rich as all hell...then as it warms up the gauge flips from lean to rich and back and forth at warp ****** speed...so my question is this: is the gauge reading wrong, or is this what is actually going on?</TD></TR></TABLE>

What you are seeing is totally normal. Before the car is at normal operating temperature, the ECU operates in 'open-loop', meaning the ECU is strictly using the pre-defined fuel/timing maps to operate the engine. It does not accept any readings from the O2 sensor. Like they said above, the ECU also operates in open-loop when you have the throttle floored.

Once the motor has reached full operating temperature, at idle and whenever you are only using partial throttle, the ecu is in 'closed-loop' mode. It takes readings from every sensor on your motor and applies custom made fuel/timing maps to the motor in order to achieve a good stoich A/F ratio. This equals optimal power and clean emissions.

Now, the reason why your A/F guage jumps around like crazy is because our non-wideband O2 sensors aren't super accurate in their readings. The Autometer A/F guage lights up according to the voltage it recieves from the O2 sensor. When the O2 sensor sniffs out a stoich reading, the voltage will bounce from anywhere between .3-.7 volts. This is partially because the O2 sensor can't be very accurate in it's reading, AND because the ECU is in closed-loop mode, meaning the ECU is constantly trying to get the best 14.7 A/F ratio by ever-so-slightly adding and removing tiny amounts of fuel, which obviously affects the O2 sensor readings since the motor can't keep a perfect a/f ratio all the time.

So in other words, it's okay.

 

so that would also explain why it gets a consistent reading under throttle...that now makes sense...now all we have to do is lean the bastard out some under throttle and it'll start to make good power...under throttle the mixture (according to the gauge) is like 2 bars from full rich...so I'm gonna guess leaning that out a little will help us make some more horse...

 

Yeah, I made quite a bit more power when I leaned out my fuel settings (VAFC). I have a digital A/F sensor guage that shows the actual voltage coming from the O2 sensor itself, instead of just lights.

I'm guessing you'll want the Autometer to show just 1 green bar (rich), and no more at WOT. I find that tuning your car on the freeway is pretty nice, 3rd gear and sometimes 4th seems to be the best, because that way you get a very accurate reading for each rpm increment. If you do test runs in 1st, or 2nd, it rips through the rpms too fast to get an accurate reading.

Partial throttle, the guage should showup somewhere in the middle of stoich, or just bouncing around.