Nightclaw

I have this nagging feeling that I've shot myself in the foot, but I'd like your collective opinion.

I was testing ATap on WinXP today (it works, if anyone was wondering), and noticed my BxS1 voltages were all over the map, from a low of .050 to a high of .905. See here for the actual ATap data.

I'm thinking that both S1 sensors are fouled (I've been playing with my MAFT for a couple weeks trying to get rid of pinging - it's gone @ 10% rich, but at what cost?? <img src="graemlins/gr_cry.gif" border="0" alt="[whiner]" /> ), but are there other explanations for such erratic voltage readings? I don't have headers, and have never played with the O2 sensor wiring. All mods are in my sig. Any thoughts? Thanks!

Crazyquik

I'm still an ATAP rookie, but here is what I think.

At WOT, you look at your B1S1 and B2S1 voltage to determine air-fuel ratio. But when just crusing around, the computer is working in open loop (using sensor feedback from the TPS, IAT, RPM, etc to adjust to stoich (14.7:1) to get the best most effcient burn). And at low throttle inputs or idle, the 02s switch back and forth. As far as I know, its perfectly normal to have a large difference like .1 in one bank and .825 in the other at low throttle inputs.

At WOT it goes to closed loop, with limited sensor feedback. This is when you want both your 02s to be .880-.900

J.

[ January 01, 2002: Message edited by: Crazyquik ]</p>

y2khawk

iTrader: (5)

It's actually close loop that is the correct term.

At anything other than WOT, the PCM is adjusting the fuel miture to maintain stoich, ie 14.7 A/F

Since the O2 sensors are the switching type, the method used is a "push till it switches" method.

The PCM will nudge the fuel mix either toward rich, or toward lean depending on the current state of the sensor. If it consistenty takes more "nudging" than normal to get it to switch, the l-trims will update to add that extra "nudge" in for next time.

The s-trims are the nudging in action.

If the are bouncing between 100 mV and 700 mV as you cruise around, they are working just fine.

Once you got WOT, the PCM goes open loop. The commanded A/F is other than 14.7, usually less than 12.5 to 12.8

This is when you watch the O2's for the 860+ mV reading.

Nightclaw

Ah. I didn't know that such behavior was normal at part-throttle. I think I need to bone up on the finer details of ATap data... Thanks for the clarification guys! <img src="graemlins/gr_cheers.gif" border="0" alt="[cheers]" />

Crazyquik

Arrrr, but thanks Harlan. I had the closed loop/open writen like you said, then I started doubting and went back and edited it <img src="gr_sad.gif" border="0">