O2 sensor search & thermocouple

http://www.ferrarichat.com/forum/showpost.php?p=136782647&postcount=122
Try this.

 

Try this Bosch reference; see 328 K-Jetronic(Lambda). Same as '85 308. But I'm not certain that O2 sensor = Lambda sensor. I'm not sure which part you mean by "thermocouple".

http://www.ferraridatabase.com/The_Downloads/The%20Documents/Bosch%20Vehicle%20Component%20Applications%20parts%20catalogue.pdf

 

Seeing as how Mike has the same car and wouldn't post without researching I'm pretty sure you can trust the information provided. Like you said it's a pretty simple device.

 

I Finded dit

BUT I can't make the link work, probably because the title is too long. SOOOoooo here is the Bosch catalog as an attachment.

Part numbers for Ferrari models are start on page 64 of the 156 page document and I've pasted (unreadable) 308/328 info below (sorry-get the pdf)
Mondial is at the end of Ferrari models.

If someone wishes to save, I'd suggest grabbing part numbers for Ferrari and checking other makes, like BMW or Alpha etc, for them.
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My link was to the same Bosch application list that Paul posted. I've been told by several people that the 84/85 308 CIS is identical to the 328, and the '88 328 Spare Parts Manual shows the same components.

 

It's also the same O2 sensor as an about 89 or so 16V Saab. Exactly the same on both ends. Buy that one.

See post #7 in this thread

http://www.ferrarichat.com/forum/showthread.php?t=159952&highlight=O2+sensor+saab

 

For what its worth I just ordered one off Amazon for 48 bucks. Almost half of what NAPA was charging. YMMV.

 

Just trying to keep the discussion interesting. I too would rather not splice in a connection.... especially where it's going to sit and cook back by the engine.

I would have gone with NAPA too as I'm all about instant gratification, but being as cheap as I am I couldn't resist doing a search on that part number.

 

Omega.com can get you pretty close with a custom built probe for about $35 (http://www.omega.com/config/probeconfig_TC.html), but I was never able to find compression fitting that worked correctly for the connection to the cat. If you can solve that, you've got your answer.

 

The thermocouple is crazy money... $867.00 list? Do these even go bad? Is there a need to replace it? Aside from the prices I've seen so far it looks to be NLA for the most part and doesn't seem to cross reference to anything else.

I disconnected mine years ago. It sits wrapped and zipped tied to the upper engine support. When I went to disconnect it from the ecu, it tripped a slow down light so I reconnected it then simply tucked it up out of the way. If I recall all it does is measure the temp of the cat if it gets too hot from unburnt fuel (another reason I 86'd the cat a while back). In my mind it causes more trouble than its worth. If you have no definitive data to support replacing it, I'd simply tuck it up out of the way and leave it alone.

 

It's an ungrounded Type-K thermocouple in a ceramic filled 127x3mm stainless steel sheath with a 33mm long rugged junction transition joint to approximately 2.66 meters of 18AWG stainless overbraided thermocouple wire. The only thing I don't know is the thread pitch and diameter for the compression fitting. The sample thermocouples I've got don't have the compression fitting with them.

(My company actually produces custom thermocouples to spec, but Omega would beat us in price easily in this application)

 

Are you going to guilt me into going out and pulling my thermocouple to find out?

Thermocouples are voltage devices, not a resistance device like an RTD or Thermistor. If you want a Type-K Thermocouple milliVolt table, you can find one here (Omega again!):

http://www.omega.com/temperature/z/pdf/z218-220.pdf

 

No, 100 ohm platinum is an RTD. Completely different animal.

You can if you want, but it's definitely a standard Type-K thermocouple, I've confirmed in a calibration bath. I've also characterized the control box on the bench, and it performs to spec using a simulated Type-K input.

 

Yup, you're exactly correct. It's simply a safety light that attempts to keep you from driving on an overheated cat and causing further problems. The reason most people remove the thermocouple is simply because they have also removed the cat!


Oh, also, a quick lesson in thermocouples in case you don't already know, so you don't get confused if you want to test yours out-

Thermocouples don't actually measure absolute temperature. They generate a voltage directly proportional to the difference in temperature between the "hot junction" (the tip of the thermocouple wires that are welded together) and the "cold junction" (the other side of the wires were you put your voltage meter).

When the hot junction is at the same temperature as the cold junction, the thermocouple will generate 0 volts. When you put the hot junction into an oven, the voltage will slowly increase. This means that you cannot tell the actual temperature with only a thermocouple. You need to have a "cold junction compensation" device which measures the temperature at the cold junction, and you can then add the temperature difference measured by the thermocouple to arrive at the "hot junction temperature".

Of course, Ferrari obviously didn't really care, because their control box does not have a cold junction compensation circuit in it, so the temperature for the dash light to turn on will move around based upon whatever the ambient temperature happens to be at the control box.

 

Here's the sketch that I gave to my Machinist many moons ago when I needed to fabricate a replacement brass compression ferrule and SST nut for one of my ex-'78 308 thermocouples (and it worked well). I believe that the thermocouple fittings on my TR precats/cats are the same (and would guess that it's the same on all F models -- but would be glad to receive any confirmation/denial):
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One minor complication is that I know the thermocouple connectors evolved/changed over the years -- some using bare female spades and some using a molded 2-pin connector (and polarity is important, but I have a recollection that F thermocouples do you the industry standard yellow-positive and red-negative wire colors IIRC).