Nistune Forums

Type 3 OBDI 91-92 B13 SR20DE
I basically have come to the conclusion that the Type 3 OBDI ECU just doesn't like to idle at stoich for very long no matter what you do, it will find a way always to resort to roughly a 13.5AFR at idle no matter how you slice and dice the TTP MIN and Multiplier or mess with the fuel table it will always resort back to this 13.5AFR after a few minutes of holding onto stoich, is there any reason for this behavior? The o2 sensor will also stop osciliating after a couple of minutes and this is when the AFR dip into the 13's for idle and will stabilize there indefinitely, anybody the reason why the o2 sensor stop giving feedback and hang rich after a couple of minutes of idling?

The only way I have been able to achieve a stoich idle indefinitely is by disabling o2 sensing in the video below is the last 10 minutes of a 35minute idle session with o2 sensing disabled

Last 10minutes of 35 minute idle session (o2 sensing disabled)
http://youtu.be/ilK_JjCUn5Q

Just some throttle blips and recovery to stoich (o2 sensing disabled)
http://youtu.be/do00Iw0RQfw


Type 4 OBDII 97 B14 SR20DE
Now this ECU is very good at maintaining a stoich 14.7 idle indefinitely for hours on end with no problem and the o2 will oscillate, no complaints or problems here, I actually love using the Type 4 ECU aside from the fact that the "VE trace" is worthless cause its highly inaccurate and doesn't illuminate the actual cell being accessed.

This is just a video showing the Type 4 ability to maintain stoich and good recovery do to everything being dialed in correctly love this Type 4 actually (Matt get the VE trace fixed please) also fuel trims and nice and perfect +/- 2~

http://youtu.be/EFbESRH0r6Q

Type 3- even in factory configuration? Normally it should hold closed loop but I've never looked too muh into the operations behind this apart from pulling the maps out of the ecu

Matt wrote:Type 3- even in factory configuration? Normally it should hold closed loop but I've never looked too muh into the operations behind this apart from pulling the maps out of the ecu

Yes in factory configuration (stock) even if I recall back to some 12-13 years ago when I had my first couple of B13 Sentra SE-R NA and then later turbo'd but with the stock ECU, I had always monitored the stock o2 sensor because I had always used an Apexi Turbo Timer which monitored o2 voltage also and I can say without a doubt that always at idle the o2 sensor never oscillated for more than just a few minutes. I have years of experience monitoring this in both my B13/B14 and S13 for what that's worth lol........but

p.s. I also ran my Apexi Turbo Timer to monitor o2 voltage even when I was NA so everything was completely stock and in perfect working original order.

My OBDII P11 w/Type 4 B14 97 ECU oscillates at idle and will maintain a stoich idle 14.7 AFR for hours on end with no problem.

Type 3 - Matt I have a crazy idea, do you think its possible that maybe the ECU is monitoring the stock oxygen sensor and looks for a steady high voltage .82-.92v and that's how it is able to pretty consistently keep the AFR's in the low-mid 13's at idle after a few mintues of keeping stoich? And from my observations in the past and present the o2 sensor will hang high indefinitely at idle with the Type 3 OBDI ECU.

Perhaps there is a table in there that this is adjustable similar to what the table is for the Z32 but maybe it has a taret idle o2 voltage instead I dunno it just feels like something like that is happening.

I havent seen anything like that when going through the code. I see the code using counters to go richer/leaner with trim adjustment based on above/below the target voltage levels from memory