Using heated 02 sensor in place of non-heated 02 sensor
 

Hello -

I took advantage of the drivetrain-specific skillzz of saturnfans.com to help me install a (narrow-band) heated oxygen sensor in my exhaust manifold :

Using heated 02 sensor in place of non-heated 02 sensor? - SaturnFans Forums


Here is the unheated sensor behavior at cold start (Universal Bosch 1-wire) :

http://www.youtube.com/watch?v=CZ9G_h5o2Yc

Here is the heated sensor behavior at cold start (4-wire NTK part no. 29413) :

http://www.youtube.com/watch?v=C4EKi2oNtzY

I compared the before/after YouTubes. The time to enter Closed-Loop operation is almost the same, only a 3 second difference, :( . However, the *working* heated oxygen sensor is actually showing normal 14.7 AFR about 24 seconds before the unheated oxygen sensor. This implies to me that the ECU/PCM has a proscribed timer for cold-engine-start to closed-loop operation ... but, if the oxygen sensor is *working*, the ECU/PCM *uses* it during open loop operation (at least that's my hope).

- Time will tell if this helps, but I am already happy because it *works*.

- My hope is that engine-off at red lights and bump starts will have shorter open-loop operation states.

- If it *only* improves my emissions, I will still be happy.

Note: I piggybacked the backup light fuse in the engine bay fuse box. I used this kind of "piggyback" fuse splitter :

http://www.parts-express.com/images/.../071-580_s.jpg

The backup light fuse met my requirements of being an "ignition-hot-only" fuse and being "non-critical" to engine operation.


CarloSW2

Very curious. Now I'm wondering how many O2 sensors my truck has. the newer ones have 3 (one for each bank, and a 3rd because...) so I'd hope I wouldn't have that many. I hope I only have one downstream of the y-pipe. Or maybe it only has one, on one downpipe. A crap-shoot I guess. But if it helped with at least 1mpg in the winter, $30 would be saved. Barely. hmm. 17mpg vs 18 mpg over 4000 miles at the prices here is only $35 saved, in 6 months. Becomes even less when I step my mpg to 18-19. Guess there's just no winning with a high clearance truck. :(

But awesome for you! I think in winter months (despite you not really having "winter") you should see a gain. The higher that temp differential is, the more effective this mod can be. Although it may take a few years to pay back the cost of the sensor at your mileage if the gains are minimal.

I know in the Nissan ECU programing, the Open Loop/Close Loop on start up is determined but the coolant temp.

For Example, my '91 240SX and my '98 Frontier (both use the same KA24DE DOHC four cylinder engine), when cold started it runs as a simultaneous multiport injection system, where every injector fired two times for each engine cycle, then with the cool temp reaches operating temp, it switches to sequential multi-port injection.

Your Saturn may be similar in its operation, which would describe why the Open loop/Closed loop switches about the same time with the different O2 sensors.

Just a thought

Bow -

Yeah, that makes a lot of sense. If true, then "spoofing" the coolant temp sensor should put me into closed-loop faster. However, that kind of mod is not on my todo list.

What is on my todo list is an engine kill switch (of the fuel injector fuse variety). My 02 mod will allow the 02 sensor to stay hot, so a long EOC will not lead to a cold 02 sensor after I bump-start.

CarloSW2

I'm not sure you are in closed loop in either of those videos. During closed loop the O2 sensor display should be switching between rich/lean very quickly. Also I'm not sure most cars can idle at 14.7 afr especially cold. Its usually something much richer, thats why there is an airpump to push O2 into the exhaust directly and burn off the excess fuel before it hits the atmosphere. Also, I would take any reading from a narrow band O2 sensor that is not switching very quickly with a grain of salt. Anything more than + or - .1 AFR and and they get extremely inaccurate.

tjts1 -

I trust the digital AFR because it ends up behaving the same way it does when the car is all warmed up. The ScanGauge is reporting what the ECU/PCM is telling it. If the ECU/PCM says closed loop via OBD-II, then I believe it's closed loop.

What you *might* be seeing is a delay in the way the AFR is displaying. Don't look at the numbers, they are cumulative. Are you watching the vertical bargraph on the right side? Once I reach closed loop it flips up and down pretty fast.

I just watched the second video again, and the refresh rate on YouTube is not fast enough to show you how fast the bargraph is flipping. This could be either the original video from the camera and/or the YouTube compression.

If it doesn't cost anything, maybe I will upload a Hi-Def version of the same video.

CarloSW2

That makes sense then thanks for clearing that up. I tried to get my megasquirt conversion to idle at 14.7 afr with no luck at all. It bucks and stumbles like you woudn't believe. I'm hoping that once I switch from batch fire to sequential injection, I can lean out the idle afr. Also desperately need to upgrade the ignition system.