 Another FI O2 Sensor Question, 3.0L FI Bung Location, Muffler or Header?? |
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| Jeffs9146 |
 Jul 14 2011, 08:43 PM
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#1
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Ski Bum  Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128  |
OK I am getting ready for my Sat BBQ work party and I realized the FI wont work properly unless the sensor is installed!
Does anyone know if it should be on one of the headers or should I weld it into the muffler?? (IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/confused24.gif) Here is what I have! Attached thumbnail(s) 
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Replies(1 - 19)
| underthetire |
Jul 14 2011, 08:52 PM
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#2
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914 Guru Group: Members Posts: 5,062 Joined: 7-October 08 From: Brentwood Member No.: 9,623 Region Association: Northern California |
QUOTE(Jeffs9146 @ Jul 14 2011, 07:43 PM)  OK I am getting ready for my Sat BBQ work party and I realized the FI wont work properly unless the sensor is installed! Does anyone know if it should be on one of the headers or should I weld it into the muffler?? (IMG:style_emoticons/default/blink.gif) (IMG:style_emoticons/default/confused24.gif) Here is what I have! The muffler not only would be tough to weld on, but it would be too cold for an o2 IMO. Btw that looks stainless. You got stainless wire on the welder? |
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| Jeffs9146 |
Jul 14 2011, 08:56 PM
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#3
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
I was going to take it to the local guy and get it done tomorrow so he would have what ever I need!
I think the original was mounted in the HE exhaust so I may just do that but I wanted to ask the collective knowledge of the board before doing it! |
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| Mike Bellis |
Jul 14 2011, 09:08 PM
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#4
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Resident Electrician Group: Members Posts: 8,345 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None 
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I would put 2. One on each collector. Then you just need an Autometer dual WB gauge or an AEM unit. Range between $200-300.
I have extra bungs and threaded plugs if you need them. |
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| dion9146 |
Jul 14 2011, 09:09 PM
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#5
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Member Group: Members Posts: 469 Joined: 16-May 04 From: Buckner, KY Member No.: 2,071 Region Association: MidAtlantic Region |
Mine is installed just after the junction on the drivers side header. By the way, the engine will run without it. The euro spec cars did not run them. Go over to the 911 tech section on Pelican and you can read for days about this subject.
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| Jeffs9146 |
Jul 14 2011, 09:17 PM
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#6
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
Yes 2 sensors would be "ideal" but I am more worried about getting it running this weekend! So if it will run without it I will just install it in the Drivers side and deal with the added one later!!
The more collective imput the better......Keep it coming!! (IMG:style_emoticons/default/piratenanner.gif) |
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| Mike Bellis |
Jul 14 2011, 10:31 PM
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#7
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Resident Electrician Group: Members Posts: 8,345 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None
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QUOTE(Jeffs9146 @ Jul 14 2011, 08:17 PM) Yes 2 sensors would be "ideal" but I am more worried about getting it running this weekend! So if it will run without it I will just install it in the Drivers side and deal with the added one later!! The more collective imput the better......Keep it coming!! (IMG:style_emoticons/default/piratenanner.gif) If you're going to get it welded, do both. I will bring you a plug for the unused one. That way you won't have to pull it apart again. |
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| Jeffs9146 |
Jul 14 2011, 10:36 PM
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#8
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
I will look into getting another bung nut! Does the stock FI system have the ability to read 2 sensors?
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| r_towle |
Jul 15 2011, 06:34 AM
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#9
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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nope, one sensor.
Its a stupid sensor also...narrow band. Given I have been chasing the fluxuating idle that curses these 3.2 motors, I read a fair bit about it...wired in some gauges, monitored the output of this specific O2 on the Motronic and its really a two position sensor. Rich or lean. It gets heated up by the two white wires...and send the signal on the black wire. You should be fine if you put in one sensor just before the muffler. Just be more cautious and watch your fuel pressure at both fuel rails...put in some inline gauges to be certain...right in the engine bay is fine. So long as the fuel pressure is correct on both banks, the O2 sensors job is to tell the ECU richer or leaner...and it flips back and forth constantly....so its always changing the ignition timing and the duration of the injector spray.... When I say its always changing...its always hunting around perfect A/F mixture, so the signal bounces up and down constantly. One should be fine, the ECU cant read two....unless you start soldering. YMMV I just read above that you have a 3.0 so I would not be able to tell you how the CIS system reads the O2. I cant imaging a more complicated O2 circuit on the older CIS system, so I suspect that one will still be fine for your application. Rich |
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| ArtechnikA |
Jul 15 2011, 06:39 AM
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#10
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(r_towle @ Jul 15 2011, 08:34 AM) ...the O2 sensors job is to the the ECU rich or lean...and it flips back and forth constantly....so its always changing the ignition timing and the duration of the injector spray.... Just to elaborate - this rich/lean dithering is done on purpose for the cars in which it was originally designed - it's the environment a 3-way catalyst needs to work its magic on both HC and NOx. |
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| r_towle |
Jul 15 2011, 06:42 AM
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#11
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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QUOTE(ArtechnikA @ Jul 15 2011, 08:39 AM) QUOTE(r_towle @ Jul 15 2011, 08:34 AM) ...the O2 sensors job is to the the ECU rich or lean...and it flips back and forth constantly....so its always changing the ignition timing and the duration of the injector spray.... Just to elaborate - this rich/lean dithering is done on purpose for the cars in which it was originally designed - it's the environment a 3-way catalyst needs to work its magic on both HC and NOx. Please elaborate more. I just figured it was the best they could do and like all the previous FI systems prior to the Motronic...it was a guess to try and keep the motor from running to lean. Rich |
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| ArtechnikA |
Jul 15 2011, 06:51 AM
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#12
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
One of my 911-list friends is the real expert on this subject, and I can't condense his synopsis in the time available to me right now. I'll go back and do that, I just can't right now.
Short version: a 3-way catalyst is working on 3 gasses - HC, CO, and NOx. Two of those - HC and CO - need an oxygen-rich environment to complete their chemical trip to CO2. This means lean - more air than stoichemitrically correct for the fuel. But the NOx catalyst component needs a reducing (rich) environment to disassociate the oxygen from Nitrogen Oxide and turn them back into (relatively) inert nitrogen and - ta da - an excess of oxygen available for the next oxidation (lean) cycle. |
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| r_towle |
Jul 15 2011, 06:55 AM
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#13
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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If and when you have time, point me to your friends threads on whatver board...
It was interesting to watch ( I ran a datalogger to my laptop so I could watch over time) At Idle...it was rhythmic....lean, rich and so on. When revved up...it went right to rich and stayed there. Rich |
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| ArtechnikA |
Jul 15 2011, 07:12 AM
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#14
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(r_towle @ Jul 15 2011, 08:55 AM) If and when you have time, point me to your friends threads... Threads? This is the dinosaur RennList (now Reutterwerk) 911 email list. There are no threads, aside from what individual members happen to save and archive. I've archived all the digests back 18 mos, and I also keep those individual posts I feel are of special value. So I've got the data, but I doubt any of it is available in a persistent online archive... |
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| ArtechnikA |
Jul 15 2011, 07:15 AM
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#15
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
QUOTE(r_towle @ Jul 15 2011, 08:55 AM) At Idle...it was rhythmic....lean, rich and so on. When revved up...it went right to rich and stayed there. That is the CIS/Motronic 'accelerator pump'. The cats are designed for steady cruise. Once your right foot calls 'More power, Mr Scott!' the emission rules go out the window and you get power - until equilibrium is again attained. |
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| jcd914 |
Jul 15 2011, 09:36 AM
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#16
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
Your CIS can run without an O2 sensor connected, it goes into open loop mode does not compensate for mixture changes. You unplug the O2 to set the base mixture. O2 sensor system on this CIS is simpler that the DME system and the O2 signal is only used for mixture compensation.
I don't think any of CIS 911's ever got a heated O2 sensor (3-wires) just the single wire sensor but maybe 82 or 83. Without a heater in the sensor you might have issues with the sensor cooling off too much or taking too long to warm up, if so you can add a heater circuit and a more $$ heated sensor. I would add a 2nd sensor so you can monitor 1 bank of cylinders while the CIS uses the other for mixture control, will give you a heads up if 1 side is richer or leaner that the other. CIS systems have multiple places for vacuum leaks so it is easy to get some cylinders that are leaner than others. Do you have access to a exhaust analyzer to set the fuel mixture with? Jim |
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| Jeffs9146 |
Jul 15 2011, 10:09 AM
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#17
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
QUOTE Do you have access to a exhaust analyzer to set the fuel mixture with? No analyzer! Your answer makes me feel more comfortable with starting the engine without the sensor installed!! That will free up some time today to get other things ready for tomorrows BBQ work party!! (IMG:style_emoticons/default/beerchug.gif) |
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| jcd914 |
Jul 15 2011, 04:42 PM
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#18
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Advanced Member Group: Members Posts: 2,081 Joined: 7-February 08 From: Sacramento, CA Member No.: 8,684 Region Association: Northern California |
QUOTE(Jeffs9146 @ Jul 15 2011, 09:09 AM) QUOTE Do you have access to a exhaust analyzer to set the fuel mixture with? No analyzer! Your answer makes me feel more comfortable with starting the engine without the sensor installed!! That will free up some time today to get other things ready for tomorrows BBQ work party!! (IMG:style_emoticons/default/beerchug.gif) If I manage to remeber to pull it out, I'll bring my analyzer with me on Saturday. Jim |
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| SirAndy |
Jul 15 2011, 10:16 PM
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#19
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Resident German Group: Admin Posts: 41,644 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
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| Jeffs9146 |
Jul 15 2011, 10:32 PM
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#20
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
Yea thats what I was thinking about doing! I will do that after I get it running since it is not needed to start the motor! (IMG:style_emoticons/default/piratenanner.gif)
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