New cat or bypass? Wideband O2?
 

Folks,

I could use some advice. I'm trying to make up my mind. I've read a bunch of articles on the topics but can't seem to make up my mind.

First, some background. Car is an '83 SC. According to PO, the cat has been cored. That explains the stink my wife complains about. O2 sensor is disconnected and in bad shape. Vac line on decel valve is disconnected and plugged. The car has always run a little rich.

With the help of the Pelican CIS experts, I got the hunting idle and cold start issues sorted out after I first bought it. And no vac leaks anywhere.

Now I'd like to finish following up on their advice and get the car back to a baseline by hooking up the O2 sensor. And I want to tame the smell and improve gas mileage.

Now the questions:
Since I need a new cat and an O2 sensor, I'm thinking about just getting a Magnaflow cat and taking it to a muffler shop to get the right connections welded on with a bung for the O2 sensor. I don't see any need in paying $500 or $1000 for a cat. No emissions test required in GA because of the age of the car so even passing a visual is not a problem. Anyone here have experience with the Magnaflow?

I've read that just hooking up the O2 is a big help with the smell. If that's the case, should I leave the cored cat or possibly go with a cat bypass with a bung?

And lastly is there really any advantage to using a wideband O2 with an SC? Having an AFR display on the dash might be "nice to have" and now is the time to do it "while I'm in there" finishing my interior project.

What do you guys think? I'm trying not to break the bank on this one as I need to do a complete A/C overhaul next.

As always, I very much appreciate the help in thinking through these things. The only thing that would make it better is if we were standing around in my garage discussing this with a cold adult beverage in hand. :D

If you've still got the wiring plug end of the O2 sensor, and it's a 3 wire (2 white and 1 black) like the one on my '84 Carrera, you can get a Bosch sensor for a mid-80s Taurus for about $40 and splice the wires. I did mine last week. Also got a M&K premuffler which was a perfect fit.

If you want a cat that is still functional albeit a bit rusty on the outside, I will give you a real good deal on mine. The grid on the exhaust end looks perfect. I'm in Augusta.

http://forums.pelicanparts.com/uploa...1343746431.jpg
http://forums.pelicanparts.com/uploa...1343746474.jpg

I just checked with three other 3.2 owners running cat bypass instead on the Cat. Not one is even remotely familiar with this "Gas Odor" being discussed. Are we just lucky? Because in my humble opinion, the OP should just run with what he has in the car. But maybe the 3.0 has other issues causing the odor.

SiberianDVM - you wouldn't have a part number on the Taurus O2 sensor, would you? Or even which year to search? I am liking the $40 price tag.

I'm at work and supposed to be working right now. :)

I will post the Bosch number when I get home this evening. I got mine from PepBoys by just asking for one for a mid-80s Taurus. This one was for a '86 I think. Exactly the same part except for the connector. Take a VOM with you and check the continuity of the pins going to the white wires (heater circuit). The first one I got was bad.

Yea, there are a few threads on it. Here is one...

http://forums.pelicanparts.com/porsche-911-technical-forum/665023-exhaust-smell.html

There are others.

Some have described it as a "sweet" smell. Some say it is worse because of modern gas formulations.

The new pre-muffler smelled a bit like burning rubber for a while, which I thought may have been the gaskets, but it wasn't too bad. I'm betting the O2 sensor will help.

Thanks for the tip on the Bosch. A while back I was trying to verify the O2 sensor connection and when I touched the plug end in the engine compartment, it basically crumbled. Need to see if it can be salvaged.

If you have a truly friendly FLAPS, take the old one in there and see if they will let you try to match the connector to one of the Bosch sensors they carry.

Of course, there is always the real one for $130. :)

Don't forget I have a cheap cat if you want to try it. I'll bet it would clean up real nice.

Hmmm... I wonder if the combination of a pre-muffler and working O2 is enough to tame the smell? Maybe I should get the O2 working first and see what difference that makes.

In that case wideband or not?

I don't think the wideband will get you anything with the stock engine management, so stock is the better option unless you're Planning Ahead ;)

Also, with no active OXS signal the stock ECU probably is running things richer than it would otherwise.

I wasn't thinking that much about engine management as much as a way to just monitor AFR.

Definitely think the lack of OXS signal is making it run richer. That's part of why I want to get this sorted.

Probably gonna have to take it and get the exhaust gas analyzed again after I make any changes.

Thinking about doing the WUR modification to make adjustable.

Porterdog,

What did you have in mind when you said Planning Ahead?

PM sent

This would be my route. Get the O2 sensor working first. Re-assess and then make a decision on the CAT. Search the classifieds for a used OE CAT if you don't go for the offer you already have in this trhead.

I just went the opposite route. Picked up an older CAT for cheap and gutted it this weekend. Put my good CAT away incase I want to revert. I only get a little smell at start up. Otherwise I like it. It finally sounds like I think it should.

J

Yea... I am a little bummed about the idea of losing HP and sound if I have to put a cat back on it. I would love to switch to SSIs or the ones from RarlyL8 with the M&K exhaust on down the road. Maybe I just need to quick sniffin' the exhaust. :) But as someone else noted on one of the other threads about the smell, that stink sticks to your clothes.

I'd love to hear feedback from anyone that has used the Magnaflow cat. I'd really love to see dyno results from a 3.0 with a Magnaflow and without cat on the same car.

Came across this old thread reading about wideband O2 sensors on CIS. Interesting reading...

http://forums.pelicanparts.com/porsche-911-technical-forum/246909-lm-1-wot-closed-loop-trick-freq-valve-cis.html

The Bosch part number for the '86 Taurus O2 sensor is 13942.

Aftermarket engine management and/or turbo conversion.

I'm not sure the expense of a wideband setup is justified for a stock car- the ECU can't really take advantage of the additional information and CIS is (IMO) sufficiently reliable that being able to monitor AFR in real time is more to satisfy geeky curiosity (not that there's anything wrong with that ;) ) than real need.

Yea, there is definitely a geek factor to it. :D

After going through some of the threads on the wideband, some people suggest that the widebands provide "better" info to the stock ECU. It's only providing an analog signal but maybe it is more frequent? :confused: It would certainly help while I'm getting the CIS back to baseline so I could see what's going on through the RPM range. Probably not much help once it's running right.

I will never rule out aftermarket engine management or turbo, but going turbo would require widebody conversion and body work skill is something I'm working towards. :)

Man I do love widebodies.