FabSpeed 2nd bung location for an SC

[mhackney]

My FabSpeed cat bypass arrived today and looks great. It has a bung installed for the lambda O2 sensor towards the front. I want to install a second bung for a wideband O2 sensor and looking for advice on location. I googled and can't find a photo of a similar setup.

My FabSpeed has the lambda bung near the large diameter pipe. There really isn't any room in that area. The inside of the pipe has a mesh so drilling a hole and welding seems problematic. That leaves the short section at the outlet as shown by the red arrow in this photo:



Is that a reasonable option?

['76 911S 3.0]

Yup that is actually the ideal location as it is about 12"-14" downstream of the merge. Just make sure your gasket is up to snuff and you should be good to go!

[porschyard]

this is where i put mine on a recent 3.2 SS build. a little tricky to weld the bung because of the tight quarters, just have to take your time. also used my smoke machine to leak test the weld

[mhackney]

Thanks gentlemen.

['76 911S 3.0]

Originally Posted by porschyard

this is where i put mine on a recent 3.2 SS build. a little tricky to weld the bung because of the tight quarters, just have to take your time. also used my smoke machine to leak test the weld

I hope that's not post catalytic converter...

[porschyard]

thanks for your concern but after 38 years of working on strictly porsche i would hope i know better than that. here is a pic of the motor on my test cart showing the euro pre muff.

[mhackney]

right above the cat bypass-muffler connection there is a sheetmetal flange that protrudes near the cat and muffler. This complicates things as I need to make sure the wideband O2 does not interfere with it.

[Bob Kontak]

Originally Posted by mhackney

right above the cat bypass-muffler connection there is a sheetmetal flange that protrudes near the cat and muffler. This complicates things as I need to make sure the wideband O2 does not interfere with it.

This fat old guy just did walrus gyrations to see how his fabspeed fits at the muffler.

I see nuttin but wide open spaces. The heater tube is a touch in the way.

Are you talking about the heat shield for the factory cat?

[mhackney]

It is difficult to get a photo but this is as close as I could get. Mine is an SC Cabriolet and it has that engine cross mount and damper. I have not confirmed but this might be the underside of that (on the driver's side).

[mhackney]

This might be a better photo. Laying on your back looking up: rear of car is to the right. Top is the outside and bottom towards the engine. The red arrow is the part I'm concerned about bumping in to.

[mhackney]

Found this photo of an 83 SC Cabriolet that clearly shows that flange (keeping an SC Cabriolet registry has its benefits!)



This car has had its exhaust system modified but that lets you see the metal bracket clearly.

[Bob Kontak]

Originally Posted by mhackney

This car has had its exhaust system modified but that lets you see the metal bracket clearly.

That thing is substantial.

[mhackney]

Does your Targa have that Bob?

I've been through the PET twice and can't find that. Maybe it is unique to the Cab shell.

[universeman]

Never seen that on mine. Is it some kind of tow hook or what?

[mhackney]

It does look like a hook of some sort. It is positioned so it would damage the number if you tried to tow with it though.

[Bob Kontak]

Originally Posted by mhackney

It does look like a hook of some sort. It is positioned so it would damage the number if you tried to tow with it though.

I looked at the 84 PET. Tell me if this pic has the "appendage".

Maybe some sort of transitional thing where the Cab picked up some of the 3.2 chassis? Strength?

For the 84 there appears to be no differentiation among the three sub-models for this section of car.

[Bob Kontak]

The fabspeed muffler has a skinnier neck that appears to offer a little breathing room?

[mhackney]

None of the PET for 84 looks like my thing.

Yes, I removed the CAT cover tonight and can see the flange more clearly. The FabSpeed does have about 6" of smaller diameter tube going to the muffler flange. So there looks to be plenty of room.

I know the Wideband sensor should be installed between 10 o'clock and 2 o'clock. But I thought I read somewhere that 12 o'clock was not good. Is that true? If not, then the new bung could go at 12 and miss that flange completely.

[porschyard]

all 3 of my G body cars, 79 us sc, 84 euro carrera and 87 euro 930 all have that same tie down point and all 3 are coupes so i dont believe it is a cab. thing. the 87 930 has a slightly different shape hole but other than that they are all the same. the pics are of the 2 euro cars

[mhackney]

That's it exactly. I wonder what it's for.