Exhaust / O2 conversion

[Beej '86 325es]

I'm putting on an IE catback system, and probably their headers too. I have an eta, so my catalytic converter will not work with this. Instead of buying an 'i' cat, I'm thinking about just fabricating some pipes to replace the cat.

Now the O2 sensor on an 'i' is different from an eta, correct? Something about a 2 wires vs. 3 wires, or something like that? What's involved in converting?

Also, how are the the exhaust manifolds fastened? Are they a stud that goes into the head, with a bolt?

I am hoping my cousin and I will be able to do this...he has helped me do some mild exhaust fabrication before...but just from stuff like the small sections you buy at autozone. It might be a bit of a project for us to do in a weekend.

Thanks.

[Bill 84 318i]

Do you have the equipment to bend/weld exhaust piping?

There are just studs/nuts that hold the exhaust manifold on. Have fun though, as I've snapped those studs before.

You should be able to just thread your 'eta' O2 sensor into where the 'i' sensor was...provided you're keeping the hole for it.

You can also get a generic (and lightweight) cat for like $80ish, if emissions are a problem.

[Beej '86 325es]

Do you have the equipment to bend/weld exhaust piping?

There are just studs/nuts that hold the exhaust manifold on. Have fun though, as I've snapped those studs before.

I just found Fred's article on his website about switching exhausts, which answered most of my questions, but didn't help much with the exhaust manifold part.

http://www.strictlyeta.net/technical/exhaust.html

I wish I had an exhaust bender (mandrel bender right?). My cousin wants to buy one, but I'm sure they're expensive. We usually just use those 45s and 30s at autozone, but those aren't mandrel bent, just kinda wrinkled so they bend.

It really scares me that I will break one of those studs. I will have to drive back to my home-town (3 1/2 hours away) on some weekend to do this. Breaking one of these on my daily driver would really really suck. Is there any way really to avoid breaking them?

[e9nine]

..the real Beej... u can try soaking the nuts in PB blaster a few days prior to driving there, as you drive the car hopefully the heat and PB blaster mix will allow them to come out easier. PB blaster for breakfast, lunch and dinner for the car...

Have your cousin try asking local shops if they'll bend the stuff for you for a small fee...

[SA E30]

If ur going with out a Cat, u don't need the O2 Sensor, here in South Africa, our E30's never came out with Cats, so we don't need them on the car. Because they never came with Cats, they never needed the O2 sensor, so they just didn't put them in. :D . On another point I asked where the O2 sensor was on another forum, and they told me, but I thought I was going nuts, cause I couldn't find it, and I thought I was dense or something.

[Beej '86 325es]

If ur going with out a Cat, u don't need the O2 Sensor, here in South Africa, our E30's never came out with Cats, so we don't need them on the car. Because they never came with Cats, they never needed the O2 sensor, so they just didn't put them in. :D . On another point I asked where the O2 sensor was on another forum, and they told me, but I thought I was going nuts, cause I couldn't find it, and I thought I was dense or something.

But doesn't not having one mess up your air/fuel mixture a bit and hurt your gas mileage?

[SA E30]

No, I not that I know of, I think it might hurt the milage, a bit. Every person I talk to in SA, says the 325i , and 325is, and 325is Evo 2. Are all high on gas. I get about 500km on a tank of petrol, but them I drive in a lot of traffic, and when on the highway I don't drive slower than 140km/h :D

[SA E30]

Oh yeah, in the Haynes manual, it also says that a non-cat car, doesn't need a cat

[EtaSport]

Yea man.. Eta, You dont need an o2 sensor. Just throw it in the trash. Only one question... does your state have emissions laws which require you to have your emissions checked? If so good luck as you will have a hard time getting the car to pass without an o2 sensor. our 528e didnt pass with it unhooked and mine skipped through okay with it on.

But yea I ran my car for half a year with no o2 sensor it actually runs a little bit better without it but you might lose a little fuel economy. I plugged mine back in because I developed an idle problem when it was cold out and having it in fixed it I seem to be able to get some more milage as well (negligible).