Cat bypass question

[Chino]

What year would a cat bypass without a oxygen sensor bung work on? In my case, I have a test pipe with what looks like a O2 sensor fitting, that has a welded on cap. Looks like it came this way, since the cap seems to match the pipe and the welds are real nice. Thanks

[Chino]

[James Brown]

Not sure I understand the question. IF it has a bung AND you don't need it, cap it. IF it does not have a bung and need one, put one on. IF you need one and there is a bung there, USE IT. If it's welded on and you need it GRIND IT OFF. This is kind of like solid fuel first stage rocket boost phase acceleration requirements. (some kind of science)?

[Chino]

I was just asking, what year 911 would use a cat bypass w/o a O2 sensor. It would help me in my ad to sell it. This one has fitting with a welded on cap. The welds are real nice, like the manufacturer made it this way. I'm not going grind off the welds, since the fitting might not be threaded for an O2 sensor. In other words I just want to know what it fits and I'm not going experiment with it and make it a worthless hacked up part.

[WIL84911]

I just looked at the Pelican catalog and all pre-mufflers with an O2 bung are for 78-89.

[Chino]

A friend just told me, my cat bypass would work on a 1978-1979 911SC . Thanks for your help guys.

[Danny_Ocean]

Originally Posted by WIL84911

I just looked at the Pelican catalog and all pre-mufflers with an O2 bung are for 78-89.

Not to hi-jack, but where/what would an O2 sensor connect to on a '79? My ROW '79 does not have a cat.

[James Brown]

were talking US version of the euro pre-muffler (non existent). Confusing, isn't it.

[oregonmon]

Fairly sure 78,79 does not have 02 sensor. I know my 79 does not have one, hence the plug in my cat bypass.

[Danny_Ocean]

Originally Posted by oregonmon

Fairly sure 78,79 does not have 02 sensor. I know my 79 does not have one, hence the plug in my cat bypass.

+1 - I know my buddy's car, a US '78, does not have an 02 sensor. Our cars (78/79) don't have "computers" as far as I know... Not sure what the sensor would plug in to...

[McLovin]

That is correct, at least for US cars.

US 911s did not use an oxygen sensor until the 1980 model year, for sure.

[Chino]

I posted this 1978-1979 911SC cat bypass on the classifieds section, if anyone is interested.

[Wil Ferch]

First of all....don't call it a cat by-pass as that conjures up an image that the exhaust gases somehow by-pass an installed cat. The "location" where a cat is used is also the place for a Euro "pre-muffler" when no cat is used.

For the SC cars, I believe the 1980 SC was the first to use an O2 sensor., at least for US but maybe also ROW., thru 1983.

Now....continue to the 3.2's. ( 1984-89). The Euro cars *generally* did not use a cat and used a pre-muffler. So ...no O2 sensor. The US, Japan, and some other markets *did* use a cat, therefore also an O2 sensor. To make matters more confusing, there was a tax-break option for the Euro cars such that one COULD have bought a car with cat and essentially get a US/Japan market engine and O2 sensor. This was the M298 option for Euro cars and you essentially got a US low compression engine and cat ( which means "and O2 sensor").

Clear as mud...eh? Physically...the cat or premuffler all fit in the same space alongside the driver's side of the engine...longitudinally.