AFR ratio and Ox sensor

[Roby466]

I made a few searches but could not find the exact info on this... sorry if a thread already exists.

I have a 1985 Euro 930 that has been "federalized" and then kind of "de-federalized" later.
It does not have a catalytic converter but it does have an O2 sensor (disconnected) and the control box is under the driver seat.

I recently installed a LC-1 system with XD16 gauge from Innovate.

Here are my 2 questions:

1: Did the euro 930 have the Ox sensor or was that installed when it was brought in the US back in 1985? The reason I am asking is that looking at how the box is fitted (or lack of proper fitment), it makes me wonder if it was added)
And should I plug that sensor back in? I run K27 7006 and Andial intercooler.

2: Now, the car seems to have around 12.5 AFR at idle and it will go around 14 or 14.5 AFR on cruise and back down to 12-13 under boost. When I gently push the throttle, it sometimes goes to 15.2 or .3 and comes right back down to the 14 range very quickly.
Does anybody think that this is a good behaviour? Do I just worry too much now that an AFR gauge is installed or should I adjust it further?

I am going to Driver Skills in the PNWR this week-end and I don't want to hurt the car due to an unsatisfactory AFR.

Thanks again for your help

David

[mooney265]

I would be more concerned about the 12-13 AFR under boost...

[Roby466]

That's great, thank you for posting that chart!
Yeah, I did some better testing last night... under low-medium boost, it stays at 12-13 but once the boost builds up it goes down to 10.5-11 so that should be good right according to the table posted above.
What I am wondering is why it stays at 12.5 at idle... is that so rich that it will wash down the rings or is it just bad on fuel economy? I don't want to lean it out too much with the screw as I fear that it will make it run lean at normal crusing and possibly under boost...
David

[smurfbus]

You can always dial it back if you're not happy about the results. I would dial it leaner on idle ie. 13.5AFR

[Roby466]

Thanks
I will try that tonight... Anybody knows what would an "acceptable" rich mixture be if I cannot get it back to spec for whatever reason?

[mark houghton]

Originally Posted by smurfbus

You can always dial it back if you're not happy about the results. I would dial it leaner on idle ie. 13.5AFR

+1^^^.
I would turn the mixture screw counterclockwise a couple degrees to lean out the idle.

Don't be so concerned about what your idle adjustment does to your boost AFR's. It will have very little if any affect since the boost enrichment is an entirely different circuit controlled by the WUR.

[smurfbus]

I shortly ran my full boost AFR at 14 (before I saw how lean it was) and it was ok so don't get too worried.

[Miguel Antonett]

Originally Posted by mooney265

I would be more concerned about the 12-13 AFR under boost...

Where did you get that data from?

[TimT]

Motec has some good info in one of there news letters

http://www.motec.com/filedownload.php/30JUNE2007.pdf?docid=2639

[mooney265]

Got it from here... literally [I think David got it from MOTEC]

Air Fuel Ratio chart