US 308 QV CAT removal - Tech advise / step-by-step needed

The 1983 FI system is "dumb." You can remove the cat and the system doesn't know. You will have to figure out what to do with the EGR and the "Slow Down" thermocouples, but it is just nuts and bolts.

And please don't. We had a 308 drive last weekend with a dozen cars. I couldn't stand being behind the cat-delete cars - it was obnoxiously stinky even at 100+' and 50 mph.

 

Agree with Brian, in fact I considered installing cats on my 1985 Euro QV. I replaced a Frankenstein-exhaust installed by a PO with a Tubi last year and though I love how it sounds, it smells terrible and I now rarely drive the car.


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Same issue with my 84. Tubi with a test pipe. Sounded great but the eye watering fumes that made it into your clothes just killed the deal.

Fun while it lasted, though.

 

What you need to probably do is dig up a pair of generic plane jane vanilla test pipes (cheap), bolt them on and see what you think.

Hyperflow, etc brand cats are not cheap (for you times two) and you dont want to blow 2k just to test the waters.

 

A properly fueled, OEM warmed-up engine should not produce a noticeable smell and certainly no eye watering. The mixture is too rich or not being efficiently lit. Cats were for emissions and, initially (back in the day) , CAUSED an objectionable rotten eggs smell from exhaust that was commonly complained about. IOW, properly tuned engines didn't produce the odor being discussed. So...fix whatever the problem is that's causing the incorrect fuel mixture.

If the car has aftermarket "performance cams," then it may not be possible to eliminate the improper mixture at idle or low/medium RPM.

HOWEVER, like others, I suggest you leave the Cats in place. The idea that they reduce performance WAS true 40 years ago; it's not now. If the car has the original cats, replacement may be a good idea but you can get cats from a local muffler shop that will do the job as effectively/efficiently as any of the "high performance" cats.

John Lingenfelter - famous Chevy engine builder, did a test back in the early '00's where they had a 700+ HP motor on a dyno and installed/removed cats. The HP change was considered not really verifiable because it was within the error range of the dyno itself.

 

I deleted my cat on my 84 QV many years ago and I don’t smell fumes or any richness in the car weather while driving or while idling but you do smell it if you stand behind the car and that’s expected. I did however leaned out the fuel air mixture a little bit the car has been running flawlessly for since I did that.

 

Disconnecting the O2 sensor will creates the fume issue in a big bad way.

 

i removed my 328 cat thinking it was corrupted. i did experience the fumes like everyone else.

i installed a straight pipe in place of the cat, but did not screw the o2 sensor into the test pipe in the port provided.

will re-installing the o2 sensor alleviate the odor?

since running ethanol-free fuel, the odor is more tolerable.

 

Well, cats at will reduce exhaust noise (as does a turbocharger) so a set of cats will automatically reduce the decibel level of the exhaust. So if you are looking for that maximum "raw" sound from the Tubi, cats would reduce the volume somewhat so it may not be the way to go to do what you want.

 

Nuno, if you like you can install the cat back on and choose the loud version of the Tub. These are the two Tubi version.

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‘83 doesn’t have an O2 sensor. You can make a couple of test pipes for about $30, just some 1 3/4 inch tube and four flanges. Use the original cats as a template.

 

Yes, overheat sensors only. The lambda was added to CIS in ‘84.

 

I think the offending car Brian was talking about had carbs. I have an ‘83 with no cats and have not smelled any problems. Nor has anyone following me lodged any complaints.

 

I smelled it behind a QV also (I'm not sure who it was, it was a red one...) , but it is possible that I could smell the old carbs that far back.
True that carbs will smell worse than K-Jet.

 

My car used to smell pretty bad on a twisty road until I replaced all of the vent line coupler hoses between the tanks. It could have been something like that. Raw fuel does stink.