Cat bypass/bung installtion help...

[Targa4now]

I recently purchased an "ORIGINAL GENUINE PORSCHE 911SC CAT BYPASS TEST PIPE" as displayed in the photo below:



Unfortunately it doesn't have an O2 bung despite the sellers claims. I am eager to have this installed but am unclear regarding the path forward. cheapest bung source, welding requirements etc.

Simple advice would be greatly appreciated. I'll be sure to post the post install sound clip for those who are interested.

Thanks as always!

Jeff

[ninelevenick]

Assuming the photo you provided is of the test pipe you purchased, that is not a test pipe. It's cat. converter equipped with a bung just above the part where the pipe splits to mate with the heat exchangers.

[Jdub]

Yes, unless the honeycombing is gutted that is a catalytic converter - at least that does not look at all like the bypass on my SC.

But for the price the cat. is typically more expensive than the bypass IF the honeycombing is in good nick and no rattles are heard when tapping the item.

[dicklague]

I got my bungs and plugs on eBay. there are lots of them there.

Procedure is to drill a 3/4" hole and then MIG weld the bung in place. It is a good idea to run a 18mm 1.0 tap through it after welding, be cause the welding can easily distort the bung. You can also use a spark plug thread chaser that is a lot cheaper than the tap. These usually have 2 size plug thread chasers. The largest is the 18mm.

Best to put the O2 sensor in the upper part of the pipe.......9 o'clock to 3 o'clock.

I installed a few bungs in my Bursch exhaust to test different locations for my Daytona Sensors Wego IV AFR instrument. I installed a wide band sensor to feed the instrument.

[Targa4now]

Thanks everyone.

Here's the description from the ebay add:

"Here is an excellent used original genuine Porsche catalytic converter test pipe 930.113.228.00 for 1978-83 911SC models. This pipe is not street legal. It is hollow. For off road use only!! This unit is $1347.75 from the boys at Porsche!!"

I knew there was risk but only paid $100. It has been hollowed and I like the stock look over std bypass pipes.

Either way I'm in this situation now. I'll search 18mm SS bungs and move forward with tig welding etc. Regarding best location, the bung should be placed on the former Cat body on one of the upstream pipes??

BTW - in the above photo, that bung looking plug after closer inspection appears to be a spot where a diagnostic sensor could been placed. It's a tiny whole with an unususal course thred pattern that can't recieve an O2 sensor as initially thought.

I'll keep you posted.

Thanks,
Jeff

Thanks for the feedback

[Bob Kontak]

Interesting thread. I found your style cat in another ad on ebay. Same shape and size. Says it's european which explains why it does not look familiar to most of us. I actually bought parts from this guy last year and had no problem with him. He is a Porsche shop owner (or was) in Indiana.

I think you are in good shape and it is a pretty cool conversation piece. Call a few welders. That is a $25 job. Some shops want an arm and a leg for welding. When I gutted a Carrera muffler I had a $300 quote to weld it back up. Got it done for $70 or so.

Porsche 911 SC European Catalytic Converter: eBay Motors (item 260606341290 end time Aug-17-10 20:01:00 PDT)

[Wil Ferch]

Careful ! ..... O2 sensor is typically metric M18mm x 1.5 ..... not 18 x 1.0

O2 Sensor Thread Size?

[Targa4now]

I must say I was drawn to the stock look of this pseudo bypass pipe. And for $100 bucks how bad could it be...

I just purchased the bung on ebay for cheap and can hopefully get the installed within the week.

Considering the structure of this pipe, it'll be interesting to see how throaty is sounds after installtion. Likewise, I'm hoping to see a bit more throttle respose...

Thanks for everyones comments and advice.

Jeff

[Targa4now]

Thanks Wil, looks like the one I purchased meets spec (i.e., 18mm x 1.5 thread ID).

[dicklague]

SORRY.......it is 1.5mm that is all you will find in an 18mm bung. I was going from memory.