Wideband reporting lambda as stoich when it's actually rich

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kipu98
Posts: 2
Joined: Tue Mar 27, 2018 6:38 pm

Wideband reporting lambda as stoich when it's actually rich

Postby kipu98 » Tue Mar 27, 2018 6:55 pm

Hello!

First off, it might not be correct forum for my issue - if so, I apologize, feel free to move it.

Peugeot 2.0L, high compression NA engine, quite aggressive cams. Mapped on dyno, all top end working flawlessly, just the idle is acting up. I have Elite 550 and WBC1.

While engine is hot and idling, the wideband reports lambda being spot on to table (1.00) but when checking with the probe at the end of exhaust it reads quite rich, around 0.92-0.94. I have re-calibrated the WB1 as per instructions, looked for any leaks in exhaust, re-checked wiring - it seems all OK. When revving up to mid-range it is a bit on a rich side but nothing too drastic.

What IS interesting though - when engine is warming up the lambda constantly reads around 0.91 (which seems to be correct) and O2 control desperately tries to pull fuel out. As soon as the engine gets up to temps at 80 degrees centigrade, the lambda slowly goes to 1.00 and then hovers slightly around it (0.99-1.02).

What should I look for? I haven't tried the Zero Demand table yet, should I try it? The MAP reading is actually quite stable, that's because I haven't tried it yet. Or can it be issue of cams being too aggressive and when the closed-loop idle RPM falls, it will create problems? Mind you, at 1100 RPM and 70 degrees (centigrade) it is still reading rich, but as soon the temperature reaches 80 and RPM drops to 1050, lambda gradually goes up to 1.00 and then hovers slightly around it. Or is it just the sensor gone bad? WBC1 doesn't report any errors though.

So, a bit of a mystery to me :)

Krister

natanel
Posts: 17
Joined: Sat Jun 12, 2010 4:58 am

Re: Wideband reporting lambda as stoich when it's actually rich

Postby natanel » Mon Apr 02, 2018 9:58 am

Why are you aiming lambda 1.00 at idle while having aggressive cams?
The cams overlapping causing more fuel to enter the chamber thus causing the ECU to chace the target AFR when clearly it can't..
You should target around 0.9 lambda (petrol) with Aggressive cams

kipu98
Posts: 2
Joined: Tue Mar 27, 2018 6:38 pm

Re: Wideband reporting lambda as stoich when it's actually rich

Postby kipu98 » Tue Apr 03, 2018 1:58 am

Maybe it wasn't clear from the description but the car is actually already operating at lambda 0.9x (rich) and is not particularly happy about it. I made modifications to tables (see below) and it operates just fine at 1.00.

Anyway.

I slapped an AEM wideband next to the WBC1 sensor and wired it to ECU, so I could check them in parallel. It turns out WBC1 does read funky at low RPMs. I left the WBC1 as "main" sensor for O2 control and let the car run. Then I went on to tweak the target lambda table so that AEM lambda would read 1.00 at different RPM levels (no load). The resulting table is attached.

So, is it sensor - or the WBC1 that is at fault?

Krister
Attachments
lambda target.PNG

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blakebonkofsky
Posts: 239
Joined: Sun Aug 02, 2015 2:58 am

Re: Wideband reporting lambda as stoich when it's actually rich

Postby blakebonkofsky » Tue Apr 03, 2018 1:13 pm

I'm not really sure what you are trying to accomplish beyond simply thinking that the WBC1 is reading incorrectly. That is certainly a possibility, but your methodology is confusing at best. If you think it's a sensor problem, why not just try replacing the sensor? They don't live forever.


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