few Q's upgrading my 323is from the headers back

[jasonk02]

Hi guys! So my catalytic converter on my 98 323is finally gave out. I say finally because now I can actually do what I've wanted to for years. The cat on the 323is are very restrictive. The headers come together into one pipe all the way down to the muffler.

What i want to do is buy cats for a 328 and then install an aftermarket catback. I found a new aftermarket catalytic converter with all the piping from the headers back to where the catback would start for right under $400.

So my first question is are Bosal catalytic converters any good? Its pretty much the only brand i can find that fits my budget.

Second question I have is will a catalytic converter for a 328 bolt on my stock 323 headers? Or a better question is are the headers on the 323is the same as on the 328 models?

The website im ordering the bosal cat from says that its made for the 2.8L but im assuming it only says that because its made for a 328 and wouldnt fit with my 323is catback?

Any help would be greatly appreciated I kind of think i got it all figured out i just dont want to order the parts and find out i got it all wrong.

Thanks in advance

[locks325is]

The 328 cat should fit but have you looked at magnaflow cats, not too expensive & heard good things about them. Get obd2 headers or supersprint reps, free flow cats or the obd2 midpipe (cats already attached), a catback & you should see a nice bump in power. You have de-tuned 325, the whole exhaust system is restrictive on the 323. If you replace the whole system (headers back) with one from a 328 or 3.2 M3, it will be a nice upgrade from stock.

[jasonk02]

yeah i know i've been waiting to do it and my cat is pretty much trashed on my car now so i figured its the perfect time for a little upgrade

[bmw4life99]

yeah i know i've been waiting to do it and my cat is pretty much trashed on my car now so i figured its the perfect time for a little upgrade

just checking on what you have done with your exhaust system Im going to redo mine here when my cats go bad as well!

[TeamRootbeer]

The exhaust manifolds are the same across all 96+ e36 models.

The midpipe from a 96+ e36 323is can be replaced with a used 96+ e36 M3 or 328 midpipe. Because the manifolds are the same, it is a direct swap. You will need to replace your muffler at the same time (can use a M3 or 328 muffler) because it shares the single pipe inlet of the midpipe.

If you elect to use parts off of the cars above to do the swap, the hardware you will need (assuming nothing else is broken/missing) are the manifold-midpipe gaskets, midpipe-muffler gaskets, manifold-midpipe locking nuts, and midpipe-muffler nuts/bolts.

I prefer to replace the nuts rather than re-use because they are fairly cheap, and will ensure a good, clean mating surface in case you need to remove again (to service transmission, etc.).

[jasonk02]

wow i thought i had posted about this earlier..

I did do the upgrade because i had to replace my catalytic converters. What i did was get new catalytic converters for a 328 and then a catback for a 328. The cats cost me a nice buck so i basically bought a no name catback (cant wait for the responses from you guys) just to see if i liked it and if its too bad i can always invest in something better.

Now before i talk about the power gain and all that i have a question about the cats. Now i drive a 323is which has one pre cat and one post cat sensor. The problem is on the 328 catalytic converter the pre cat sensors are on the headers and not on the cat part. So what i had to do is basically put both sensors post cat. Now the check engine light comes on every 250 miles or so but hasnt since the temperatures dropped really low. In the spring i plan on doing whatever i need to do to get it right.

My question is what is the better and most economical solution to this. Is it to get 328 headers with positions for the sensors or is it to have a qualified person make two positions for the sensors?

Other than that I liked the switch alot i do think there is a little more power than before. The catback is a little loud even for my taste and that might have to be switched in the spring also. Ill post a link of a the sound at the bottom of my post but although i really like the sound of the catback its just way to loud inside the car and i think that has to do with the fact i bought a shitty catback. Anyway there it is i liked the transformation but please give me some insight on what to do about the sensor issue.

found a thread i started with the answer on it thanks

[ame]http://www.youtube.com/watch?v=c4aLHg-2eRc[/ame]

[FLYINV]

I'm pretty sure you put one sensor pre-cat and one post-cat along the same exhaust pipe and place a bung in each of the sensor locations on the other pipe.

[GallyClack]

Get obd2 headers or supersprint reps

[jasonk02]

I'm pretty sure you put one sensor pre-cat and one post-cat along the same exhaust pipe and place a bung in each of the sensor locations on the other pipe.

Obviously thats what i need to do but there isnt a pre cat hole to put the sensor in.

Im just curious what you guys would do. Get 328 headers or making a custom hole for the sensor pre cat.

[magicninja]

You could get an o2 sensor bung welded in. I had to get one for the vw i swapped the engine in. These guys are local to me, so thats why i got mine there.

http://www.034motorsport.com/fabrica...l-p-18213.html

[TeamRootbeer]

Get obd2 headers or supersprint reps

He has OBD2 headers (identical part number to the 328 and M3). This is bad advice.

OP, you do NOT need to modify (read: drill/weld) your setup in any way to accommodate the pre-cat O2 sensor. The 328 originally uses two pre-cat and two post-car O2 sensors, and since your car only uses one of each, the remaining 2/4 holes will not be used. The 328 achieves this by using two O2 sensor holes in the midpipe (the post-cat locations), and two in the manifold (the pre-cat locations).

There are two bolts in your current headers, which plug the locations where the 328 would have mounted up its pre-cat O2 sensors (but your previous "323" configuration did not use those holes - thus, plugged). Remove one of the bolts plugging the manifold, insert your pre-cat O2 sensor, and reinstall that same bolt into the post-cat hole that you opened up by removing your pre-cat sensor. You are reusing the same bolt. All four holes should be plugged again at this point.

You will need to reroute your pre-cat sensor's wiring behind the heat-shielding along the transmission tunnel so that it does not contact your exhaust.

[jasonk02]

He has OBD2 headers (identical part number to the 328 and M3). This is bad advice.

OP, you do NOT need to modify (read: drill/weld) your setup in any way to accommodate the pre-cat O2 sensor. The 328 originally uses two pre-cat and two post-car O2 sensors, and since your car only uses one of each, the remaining 2/4 holes will not be used. The 328 achieves this by using two O2 sensor holes in the midpipe (the post-cat locations), and two in the manifold (the pre-cat locations).

There are two bolts in your current headers, which plug the locations where the 328 would have mounted up its pre-cat O2 sensors (but your previous "323" configuration did not use those holes - thus, plugged). Remove one of the bolts plugging the manifold, insert your pre-cat O2 sensor, and reinstall that same bolt into the post-cat hole that you opened up by removing your pre-cat sensor. You are reusing the same bolt. All four holes should be plugged again at this point.

You will need to reroute your pre-cat sensor's wiring behind the heat-shielding along the transmission tunnel so that it does not contact your exhaust.

Wow thats really helpful. I guess my mechanic was wrong and that is really a surprise because hes been fixing european imports for about 20 years. Thats good to know my car is in his shop anyway because a tree branch fell on my car but ill have him do that too. (I hope you are right because he had told me theres nowhere to put the O2 sensors.)