Optimum placement for wideband O2 sensor?
 

I have found the oem O2 sensor wires clipped and dangling right above the front muffler. There are two white wires and a single black wire. I imagine my car is running on a set fuel map and isn't performing as well as it should or maybe my fuel economy could be better.

I can see a bung on the passenger side exhaust manifold, but it is blocked off with a bolt, and it is no where near where the wires pass through underneath the car.

I have an Innovate LC-1 stashed away in my closet, and I think it's time I put it to use. I'd like to install the wideband O2, and I believe the controller can output a narrow band signal for the ecu.

Where would be the optimum placement for the sensor? I know it needs to be mounted on top of the pipe to avoid condensation in the exhaust. I know it needs to be a certain distance away because of the heat, but it would be better to monitor both banks of cylinders, correct?

Should I fabricate a Y pipe and place the sensor just after the Y?

So you have a total of 1 bung in the whole exhaust setup, currently mounted on the passenger side. have you checked just above the front top of the Cat? stock location for the o2 should be there [see pic]. if its not there, you can easily have an exhaust shop make a balance pipe between the 2 down pipes and add a bung, for around 50-70 bucks.

My car's exhaust is like the image below. I have the front muffler then the little pancake catalytic converter towards the rear. The cat does have a hole in the top, but again, I have the small one towards the rear, and after feeling for the hole, I noticed it needs a plug. :banghead: Stupid POs. Also, the heat shield above the front muffler does have a hole in it to clear what would be an O2 sensor.

The only difference is I don't have intermediate pipes between the cast manifolds and the front muffler. My front muffler has two pipes that connect directly to the cast manifolds.

What the hell has been done to my car?

*edit - The rear pancake component may be a silencer, and what I thought was a front muffler may be a catalytic converter. Who knows? I don't.

I honestly just want to hack off the middle guy and merge the two pipes coming off the manifolds into one pipe to run straight to the rear then I'll add in my O2 where they merge.

http://c782224.r24.cf2.rackcdn.com/202-00.gif

Here are pictures of my exhaust. You can see the dangling O2 sensor wires. There is not a hole on top of the catalytic converter, muffler, silencer, whatever to thread in an O2 sensor.

http://i1150.photobucket.com/albums/...g/100_0104.jpg

http://i1150.photobucket.com/albums/...g/100_0105.jpg

http://i1150.photobucket.com/albums/...g/100_0107.jpg

http://i1150.photobucket.com/albums/...g/100_0108.jpg

couple thoughts

why is the red nylon strap there......that ISN'T supposed to be there

I don't know why someone would cut the 02 sensor on an L jet car (like yours)....the way the 02 sensor works is when the throttle position sensor is on idle or cruise it enables the O2 and it tries to adjust the map to stoich..... without it the car will run overly rich and your fuel mileage will suffer quite a bit.....if its been this way for a while, your catalytic convertor is probably damaged as well....

The good news is a new one is cheap and easy to install

Read my thread on replacing the shifter linkage bushing. That will explain the strap. :roflmao: It was one of those WYAIT taking pictures of one thing, I should take pictures of another.

I have a wide band O2 I want to install which can output an analog narrow band signal. Could I ditch the catalytic converter, and put the O2 sensor in the merge of the Y pipe and get acceptable measurements?

looks like a custom welded muffler replacing your stock cat to me, any signs of your smog pump air vein down there(unless the whole pump was deleted) ? An exhaust shop can probably better answer the question of whether its a cat or not, either way if you wanted to keep that setup (assuming you can or dont need to pass emissions), the exhaust shop can very easily add a bung to either pipe or weld a balance pipe between where the wires are dangling in pic 2.

If you want to use your wideband sensor, i would recommend running it independently of your oem sensor as the readings sometimes can fluctuate or the system errors out, causing false readings and making the fuel trim go nuts.

Sounds good. I'll probably delete the front doo-hicky and get them to fabricate a Y pipe. I'll put my wide band in, and install a new narrow band for the ecu slightly downstream. I could probably angle each sensor slightly, and the wide band wouldn't block the narrow band at all. It might help them miss the torque tube too. Bingo!

I do have the air pump. Is the "vein" you speak of a rubber hose? If so, it's just dangling too.

The front muffler is now gone. I liked the exhaust note before a little better. It didn't have that raspy growl of a Mustang or Camaro. I kept the muffler incase I ever wanted to put it back on. Someone had custom made it I think. Now it has a little raspiness accelerating from idle, but it tones down into the powerful vvvvvrrrrrmmmmm I'm used to.

I had two O2 bungs welded into the new y-pipe at 10 o'clock and 2 o'clock. One is about two inches downstream from the other. I am running a Bosch narrow band connected to the ECU. I'll be putting in my wide band gauge and sensor soon.

I believe I have read before that the ECU has to "learn" as you drive the car. How long can I expect it to take for the ECU to obtain the proper A/F mixture? I won't be able to install my wide band gauge for a week or so.

I am running at the standard 43.5psi fuel pressure for 24lb injectors. Is this greater than stock for the psi? Can the ECU correct that? I wouldn't mind if the injectors got a little break at a lower duty cycle.

Here is the O2 sensor I bought and wired in.

Your exhaust looks exactly the same as my '81 K-Jet non cat 928. Looks like someone replaced your cat system with a non-cat system, so they just cut off the O2 sensor? Not real smart.

That makes sense. Only Porsche could design a muffler to tone down the exhaust right where it needs it to be a little more subtle. I'm glad I saved the muffler, I may see about getting two bungs welded into it at some point. The engine code matches the year model (1984) of the body, so I'm pretty sure I don't have a mismatched car. I hope I gain a few horsepower and gain more miles per gallon after this O2 sensor. I need to get the wide band in asap.

if you decided to connect the O2 sensor you need to change the coding plug to make sure that the computer knows to look at the 02 sensor, just remembered. However I'm not sure the OBs have this, any one know?

US '80-'84 uses L-Jet injection. L-Jet is analog. It doesn't learn.

(Learning/memory starts in '87 with LH 2.3.)

Stock FP for L-Jet is 2.5 bar/36 psi. WOT will be way too rich at 3 bar.

Thanks. So the ECU has a narrow range of a/f compensation, and my current fuel pressure is out of that range? I'll lower it.

I have another question. Looking at the front of the car, in the lower driver's side corner of the radiator is a sensor. Someone has unplugged the sensor and jumpered the plug with a piece of wire. What sensor is this?

Unless I have a defective fuel pressure gauge, with the fuel pressure set at 36psi, my car is not getting enough fuel. When I give it gas, it wants to die except at very light load. It runs great around 45psi. Could my maf be defective or is my car getting more air than stock? I don't believe I have any air leaks.