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-   -   Typical engine noise after removing catalytic converter (http://forums.pelicanparts.com/porsche-911-technical-forum/1080380-typical-engine-noise-after-removing-catalytic-converter.html)

eric hellersted 12-10-2020 04:09 AM

Typical engine noise after removing catalytic converter
 
Hello all,

I had my 1983 SC catalytic converter removed about a year ago. It gets driven about 1000 miles per year, and has around 59,000 miles on it. The question is the sound delivered under load, consistently starting at 2,800 RPM. It's throaty for sure, but makes a consistent popping sound until I reach a steady rpm.
It doesn't make this popping noise while revving it up sitting still.
All while having good oil pressure, no smoke, and being plenty warmed up.
When letting off the gas from being under load, no popping or backfiring, just normal sounding.

I've heard it was normal, and some say bad head studs...
Any help would be appreciated.
Thank you.

Eric, '83 SC Cab.

theiceman 12-10-2020 04:28 AM

i have never had a cat on my 78 as it was gone when i first got it and had been bypassed, never experienced what you are hearing, no popping at all under load , what plugs are you running ? i know there was a split in the SC i think 78/79 used one set of plugs and 80 up used another ,. i would check that . But who knows maybe it is normal and i am the odd one out .
Other think to consider is the setup is a little different with yours having lambda .

Solamar 12-10-2020 06:28 AM

Is the popping rythmic, consistent with rpm? Or is it random lean popping/backfires?

trond 12-10-2020 07:24 AM

popping is wrong. Look elsewhere. Exhaust leak but then it should be more prominent off the gas ? Headstuds ?
If exhaust related I would expect it to be worse at low/no load. Popping is not normal under load

Lakelab 12-10-2020 04:05 PM

had my cat removed with a straight pipe this year. No popping noise. 88

john walker's workshop 12-10-2020 04:13 PM

Pull the bottom covers and see how many studs are broken. Drain the oil first.

capt911 12-10-2020 11:27 PM

I had what you are explaining and thought it was an exhaust leak. When I went to adjust my valves found two broken head studs on and back right hand cylinder. I only heard it when on the power and never when decelerating. 83 SC with about 160k miles at the time


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