Kat on carburated car ? - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 7 (permalink) Old 08-11-2019, 06:26 AM Thread Starter
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Kat on carburated car ?

Hello all,

in my everlasting quest in getting rid of those pesky exhaust fumes in the cabin I'm contemplating if it would be an option placing a kat in the exhaust, because our car is running on two solex carburettors it won't probably last many years but we only drive around 2000 miles a year and a universal kat is only 80 dollars.

Did any of you ever tried this ? opinions ? experiences ?

'86 Quad Spider
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post #2 of 7 (permalink) Old 08-11-2019, 10:26 AM
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Originally Posted by fransinge View Post
Hello all,



in my everlasting quest in getting rid of those pesky exhaust fumes in the cabin I'm contemplating if it would be an option placing a kat in the exhaust, because our car is running on two solex carburettors it won't probably last many years but we only drive around 2000 miles a year and a universal kat is only 80 dollars.



Did any of you ever tried this ? opinions ? experiences ?


Is your exhaust tip pointing straight/upwards? Or down like it should be?
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post #3 of 7 (permalink) Old 08-11-2019, 03:13 PM
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It seems that the answer is yes.

A quick search turns up at least two companies offering converters for classics. I don’t have any relationship with either and so can make no comments as to whether they’re any good or not

https://jetex.co.uk/classic-car-converters/

Classic Car Catalytic Converter | Redback Converters

I can’t imagine that their products would offer anything that couldn’t be found in a junkyarded Cat which fit your exhaust pipe.

My only question and concern would be where to locate the Cat, because of the heat.

71 Spider
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post #4 of 7 (permalink) Old 08-11-2019, 04:47 PM
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Well exhaust fumes in the cabin and exhaust emissions are separate issues. If you have leaks in your floorboard, improper routing of the exhaust tips, all these will cause exhaust fumes in the cabin no matter how clean the exhaust is.

I've never seen an OEM catalyst without an O2 sensor, and I doubt a Catalyst will last very long without the O2 sensor feedback loop. I went to both of those sites, and they both sell the same product. One of the sites has the following wiggle phrase at the bottom of the page

"...It is important that the vehicle’s engine is tuned correctly. If not, this can cause the converter to perform at a sub optimum level and possibly cause damage to the converter...."

Reading between the lines of your post. Are your Solex carbs not adjusted properly? Or are the carbs so old that they can't be adjusted properly, meaning that the throttle shaft bores are wallowed out, and expensive rebushing is required?

Wise use of your money would include fitting an O2 sensor bung to your exhaust pipe and hooking up a wide band O2 sensor. This will guide you in adjusting and diagnosing your carbs. if you find that your Solex carb are indeed worn out and too pricey to fix you can still buy rebuilt Weber cars at reasonable prices.

Hope this was helpful
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post #5 of 7 (permalink) Old 08-11-2019, 05:05 PM
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I've owned carb'd cars with cat converters so it's not unheard of, but they were designed for it and had emissions cars that were tuned pretty lean.

I wouldn't slap one on a car not designed with a cat converter just to try to cut exhaust fumes. As an example, if your problem is you're running rich, the cat can potentially overheat (I'm talking red hot) and either plug up or cause a fire. Not really something you want to mess with willy-nilly.

Tom

1963 Giulia Spider (1750 engine)
1974 GTV
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Former: 1987 Milano Gold
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post #6 of 7 (permalink) Old 08-13-2019, 01:49 AM Thread Starter
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Quote:
Originally Posted by tremere613 View Post
Is your exhaust tip pointing straight/upwards? Or down like it should be?
Tried all that, the car being a QV means that it is supposed to go straight out the back, even brought the exhaust to the right side of the car, right now the tip is pointing downwards but depending on wind direction still smelly and dizzy-ish after a drive.

Mounting a bung with an o2 sensor and a afr gauge is actually a very good idea, might wanna start with that, what ratio should I be looking for to keep a kat.conv. in decent shape ?

'86 Quad Spider
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post #7 of 7 (permalink) Old 08-13-2019, 03:25 PM
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So your car is a 1986 model and it came stock from the factory with carb, is that correct ? In the USA all Spider's after 1981 had Bosch L - Jetronic EFI.

In answer to your question a catalyst likes to sees 14.7 to 1 air fuel ratio (AFR). Rich mixtures like 13 to 1, and 12 to 1 will rapidly degrade the catalyst as unburnt gas will stick to the catalyst surface. Lean mixtures 16 to 1, and 17 to 1 are not as bad. The catalyst can tolerate those for a long time without failure, but the catalyst also doesn't work well at those AFRs.

It is true that there were carbureted cars in the 1980's in the USA that had catalysts. However they were so called "Intelligent Carburetors" or "Emissions Carburetors". They had an O2 sensor, and a microprocessor controlled motor in the carburetor. Depending on the brand, the motor either controlled an air intake butterfly or some kind of fuel jet.

They didn't work very well.

Hope this was useful.
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