O2 sensor and cat elimination?

[Fredfox]

Should I leave it in or is there a way to disable it?

[Pete R]

I think you have to leave it in.. it controls stuff. (how's that for a technical answer? that's all I know though) The cat eliminating straight pipes I've seen have a provision to screw the sensor into.

[Pete R]

i didn't even time my last post

[MattGram]

You need it

[Fredfox]

Thanks.

[FIREMN]

wow..i have been looking for this discussion to come up.
I have an 87 S4. was given a set of cat delete pipes with a port for an o2 sensor..the port is a fake to trick emissions folks...i still want to add it but am pretty sure i have to make the port real...has anyone ever used pipes like this?

[Pete R]

Originally Posted by FIREMN

wow..i have been looking for this discussion to come up.
I have an 87 S4. was given a set of cat delete pipes with a port for an o2 sensor..the port is a fake to trick emissions folks...i still want to add it but am pretty sure i have to make the port real...has anyone ever used pipes like this?

I put a straight pipe on my car. It had a threaded hole for the O2 sensor. I actually just welded it shut because my CIS doesn't need the sensor. I don't understand why the port is fake. No threads?

[FIREMN]

the port was a fake, i think because they just welded straight thru pipes together, then got hit by an emissions inspection for not having an O2 sensor...
What model year do you have? and what is the CIS?

I am new to the board and haven't learned the acronyms to this car yet...thnx soo much for the reply....do you like the pipes?
i want a better sound, and want to eliminate the heat from the cats

john

[Landseer]

The port can be used for a wide band O2 sensor for tuning.

If you don't need cats now due to local decision to not enforce federal law, be aware that could change in the futur

I'm reversing direction and installing cats on everything.

[FIREMN]

do i need it? can i bolt straight up with no worries to the 87 S4

[Landseer]

The O2 sensor is an important part of the engine control loop. Do some searching on rennlist on this topic, its been covered there.

If you want sound, keep cats and combine to a large single pipe, maybe with one muffler, custom, after the cat.

Spending for horsepower addition for a street car is a fool's game in my opinion. I can't use what I have on the 220 hp early cars.

[FIREMN]

Yea, i am not too worried about extra HP. my car is titled as a classic and doesn't require the emissions insp. the pipes were given to me, and if i could get rid of the heat and potential fire issue plus with better sound, then i am all in. as far as re doing the exhaust..I am not wanting to throw money that way.

[porken]

MAF sensors (even rebuilt ones) don't all measure the same airflow from idle to WOT. (They are often way off. It only takes a fraction of a volt to change the fueling quite a bit.) The O2 sensor loop keeps the fueling near the factory tune (in a sine wave from 13 to 16:1 AFR, averaging low 14's).

Going for a few extra peak HP is usually counterproductive overall. Better drivability from performance mods is a better goal. More average HP is good, and more TQ is even better.


With my '85-'86 chips, I've programmed an option to force the O2 sensor loop to keep a flat 15.4 AFR, which is more efficient, and gives better response than the sine wave around 14.