Need Cliffs notes on fuel trim and RKAT on the Durametric
 

Okay smart guys and Porsche forum mentors,
I've grasped the concept of fuel trim (both short and long term) thanks to this great video (https://www.youtube.com/watch?v=5WnM_NsOtd8&feature=youtu.be) and hooked up my trusty Durametric to see these results:
http://986forum.com/forums/uploads01...1401588662.jpg
Sooo..., What exactly is this telling me?
I have just redone my cam chain pads etc., I just changed the AOS, I just replaced the oil filler tube, I just replaced the venturi tube, and a new coolant tank (which is unrelated but I thought I would mention it as it was such a b'tch to do) ;)
Any thoughts?

RKAT is out of whack.. Have you performed a handover?

Please define "handover".

Its a term used to define a "reboot" of the ECU. Google it for details.

Basically if you do a ton of work to an engine that has a few small issues that the fuel trim has been "masking" the ECU doesn't know when those items are corrected. It will continue to "adapt" to the prior conditions, and it does this through fuel trim primarily.

A handover will reset the adaptive and your fuel trim values will be accurate for the current engine conditions, otherwise you are looking at the past.

Great, thanks!

So do I have to take it to the (gasp) dealer to do this? I only have a Durametric.

I saw somewhere if you clear all codes with the durametric it erases the long term fuel trim and then begins the process of relearning them. Maybe worth a shot? I did it one time while idling the car to clear a code and the car definitely started running differently the instant I cleared them. It seems like disconnecting the battery would clear everything as well. To readapt the egos I think you put the key in and turn to on and wait like a minute and then turn it back off, all without touching the gas.

Clearing the codes is always able to make for a quick change in the engine idle and low speed characteristics. This is not a handover.

You can do a hard reset by disconnecting both battery terminals and touching them together, then leaving them disconnected over night. This is similar to a handover in its results.

A handover can be done by any shop with a PIWIS or Autologic system.

Good. I'll try the "hard reset" approach to start with. I still need to change the fuel tank purge valve and do a general vacuum leak test or smoke test to finish my current intervention. Thanks for the tip.

Look at your MAF readings at correct rpm (about 740), motor fully warmed up. I don't know what the MAF spec is for an S, but for the 2.7 its 15 kg/min +/- 1.5.

If you have significantly low MAF values, then its probably likely you have a vacuum leak. Check the usual suspects, AOS, oil filler tube, intake plumbing before the intake plenums, evap system.

MAF is bang on 15. FRA is at 0.98.
I've done the hard reset but I'm still getting the RKAT close to 4.
I've not done the purge valve yet (waiting for the part) nor the smoke test.
This morning I have codes P0430, P0410, and P1411.
Things are getting worse, not better. Hopefully the leak test will show something.

Success!
Found a leak in the rubber collar that holds the intake plenum to the manifold. Gear clamp on crooked. Spray test confirmed it. Fixed it and now I get this:
http://986forum.com/forums/uploads01...1401901370.jpg
Happy camper! :)