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Discussion summary
YOUR RESEARCHIs This Considered a Lean AFR?
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Install right
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
A few weeks ago, I had a Bosch O2 sensor installed right after the header and only a few inches before the factory O2 sensor before the catalytic converter.
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Performed · outcome unconfirmed · Original poster
Basically, nothing has changed with this new configuration.
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Suggestion
If you have the equipment -- Durametric I supports this -- it might not be a bad idea to check the camshaft timing to ensure the camshafts have reasonably correct timing.
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Suggestion
If you have the equipment -- Durametric I supports this -- it might not be a bad idea to check the camshaft timing to ensure the camshafts have reasonably correct timing.
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Performed · outcome unconfirmed · Original poster
A few weeks ago, I had a Bosch O2 sensor installed right after the header and only a few inches before the factory O2 sensor before the catalytic converter.
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A few weeks ago, I had a Bosch O2 sensor installed right after the header and only a few inches before the factory O2 sensor before the catalytic converter. I also moved the air filter closer to the supercharger (directly in front of the SC's intercooler).
I was surprised to see a wide fluctuation of AFR readings -- anywhere from 14.8-18. It seems the car is "hunting for idle". The DME was reset during the weld-in of the O2 bung. It should have had a chance to re-calibrate. Yes, this is a custom flash based on VF Engineering's SC kit.
Could moving the air filter too close to the supercharger started screwing with the MAF?
Here's a video of it idling w/ gauge read-outs.
http://youtu.be/ZTxqitPm-h8
I would keep the MAF as far away from the filtet as possible. You are probably getting turbulance through the MAF. They are very sensitive to turbulance. I had to deal with this when I supercharged my 928. Perhaps even instalking air straighteners would help. They look like a box of straws.
+1 All the turboed cars that I have built with the MAF has at least 8 in pipe between filter and MAF. ( I prefer MAP sensors...)
Like lmo said, the filter creates turbulance. Basically the air is bouncing around the pipe and MAF cant measure all of it. Thus lean condition.
In order to have easier access to clean it. The process of pulling the ABS piping out from underneath the PS lines, electrical lines, and SC coolant lines is quite the PITA. In fact, I nearly damaged the SC coolant reservoir pulling it out over the weekend. Thus, I decided to move it once and for all.
I have a honeycomb grid already. I think increasing distance between the filter & the MAF housing is key, as others have mentioned.
Good point. I have an idea on how to create more distance.
Thanks for the advice.
Below is what I'll call
modded intake, configuration #1
. It's 3.5" aluminum pipe with silicone joiners. The MAF is well situated away from the air filter. The honeycomb mesh, to smooth out the air flow, is attached directly to the air filter. I'm still seeing lean AFRs at idle. Basically, nothing has changed with this new configuration. My phone battery died right at the end of the video, so there's not a lot of visual data regarding the AFR.
In reality, this setup isn't ideal, because, I'm in effect, creating a "hot" air intake... but a few weeks ago, it seemed like a good idea at the time. With the car stationary, that aluminum is doing its job quite well, as a heat conductor.
Aesthetics aside (which is all this is, really), what are my next steps? Even before I had this hairbrained idea of moving the air filter from its intended location, I think the car was hunting for idle. With the addition of a new O2 sensor after the header, it just became more apparent. I'm confident there isn't a vacuum leak.
If I were VF, the first thing I'd be asking is "why the hell are you modifying our kit? We aren't going to support your wacky changes"... Then again, I think there was a problem, previous to the mods.
On the advice of another, I'm going to datalog with a Durametric. There must be some clues in the data.
The hunting idle can have several causes...
The fact the engine has a supercharger complicates things so I'll cover issues the stock/unmodified engine can experience, first.
Right off the bat there is the AOS. It was a hunting idle, albeit going up and down at a slower more leisurely pace, that was the symptom of an AOS failure, pending AOS failure. There was no CEL.
Another time there was a hunting idle was when a VarioCam solenoid was acting up. In this case there was no CEL but a reading of the pending codes turned up an error code pointing to the VarioCam solenoid. (Both the solenoid and actuator were replaced.)
With the addition of the supercharger, that changes the game. I would still try to verify the AOS is ok, though how you would do this I can't say. Certain engine behavior helps me decide the AOS is at fault. (The most recent AOS failure had the engine billowing smoke. There was no pre-warning behavior from the engine either.) The good old try to remove the oil filler tube cap while the engine is running is not infallible. Not every AOS failure generates a CEL with error codes, unless the failure is very far along, and even the one time I was seeing the CEL come the error codes had me suspecting the MAF not the AOS.
Thus you might concentrate on ensuring the cause isn't from something else.
With modifications to the engine -- especially the intake -- I'm always thinking intake air leak. Either it leaks under vacuum, well, low pressure, or it leaks under boost. There can be a leak at the oil filler tube too. These can crack/split and leak under some conditions. Wrenching on an older engine can result in inadvertent to be sure but real nonetheless damage to the oil filler tube and to other hoses/lines around the engine.
Before I go on if I read your first post correctly, at least read between the lines correctly, this behavior only came about after you made some changes to the intake system and possibly the exhaust system?
If so I have to point out the last thing touched is the first thing suspect.
I guess if I were at the car I'd want to see what the intake air pressure reading looks like. This might point to a leak then all you have to do is find it.
Also, I would want to monitor the short term fuel trims and the ignition advance.
If you have the equipment -- Durametric I supports this -- it might not be a bad idea to check the camshaft timing to ensure the camshafts have reasonably correct timing.
I'm thinking you would see something out of the ordinary that would help lead you to ultimately to the cause.
First of all, I want to thank everybody for taking the time to help me diagnose this problem. Tonight I hooked up the Durametric and cleared the common O2 sensors codes, as well as an alarm code. I made no other changes since my last post. Oddly enough, the AFR readings have narrowed quite a bit, with no real explanation, other than clearing all fault codes.
Should I be concerned with the O2 sensor resistance (ahead of the cat on bank one) reading of 384? What exactly is "loss adaptation idle"?
Below are videos of the data (engine roughness, O2 sensor, camshaft deviation, mass air flow, ignition angle, etc.) Does anything stand out to you guys?
Still TODO:
1. move honeycomb from filter to MAF housing (thx Imo000)
2. check for AOS leak (oh that's going to be fun... -- thx Macster? LOL)
3. inspect oil filler tube for possible crack
http://youtu.be/NHP54TK0SPQ
http://youtu.be/oQZNKUBSA-M
http://youtu.be/S1L9SwAnAWY
Looks as though I should have taken some fuel trim readings. Here's an informative read regarding FRA and RKAT:
http://www.callasrennsport.com/tag/porsche-drivability/
This is a source reference. Confirm exact model applicability in the original material.
