[sport330i6spd]

So I have little knowledge as to what goes into the E90 N52 330i exhaust system (or exhausts in general), and would like to learn more before I start buying/changing/tuning things. Would greatly appreciate an education here.

As far as I can tell, you've got the following sequence from front of car to back:

a. The engine block's 6 cylinder chambers
b. 2x exhaust manifolds (connecting to 3 cylinders each); each manifold has its own catalytic converter [first picture below]
c. 2x exhaust pipes, each connecting to an exhaust manifold, and each having an additional catalytic converter [second picture below]
d. A center muffler that joins the 2x exhaust pipes [third picture below]
e. The rear muffler that connects to the center muffler [third picture below]

The BMW PE (part # 18102208793, fourth picture below) replaces the center muffler and rear muffler. Generally speaking, in mufflers there are resonance chambers that cancel our sound waves. By changing the resonance chamber design, the BMW PE exhaust is louder and awesomer. What I'm not sure about is this:
1. In the U.S. BMW PE, do both the center muffler and rear muffler feature different resonance chamber designs?
2. Why do we have 2x sets of catalytic converters (primary and secondary / front and rear)?
3. When people also do a secondary catalytic converter delete in addition the PE (and I'm assuming they mean catalytic converter in the exhaust pipes), what effect does this have besides better sound? Does the car's performance take a hit? Does it release noticeably more exhaust fumes? We've all smelled those cars whose exhaust seem to come completely unfiltered from the engine, and that's a step too far for me.

Stock system:


http://www.realoem.com/bmw/showparts...87&hg=18&fg=10


http://www.realoem.com/bmw/showparts...88&hg=18&fg=10


http://www.realoem.com/bmw/showparts...11&hg=18&fg=20

BMW PE:


http://www.realoem.com/bmw/showparts...97&hg=18&fg=95

[Nordkeyz73]

That "center muffler" is deleted. It is formally called a resonator or resonating chamber and attenuates low frequencies both by diffusion and phase cancellation. The PE gives you the classic bimmer sound. As it gets broken in, it will get pleasingly louder, too loud for some people. But, I think it's the best mod I've done so far.

[Seanzie]

These are the types posts that keep me coming back here... thanks for the great question!

I previously didn't understand what a resonater was, and it's good to know that it's essentially the muffler midway through the system.

[Mike.]

Do the mod, it's like if Shakespeare was personally writing his greatest poem coming out of your exhaust

[EndOfAnEra]

Do the PE and secondary cat delete, that's what I have and love it

[sport330i6spd]

Originally Posted by Nordkeyz73

That "center muffler" is deleted. It is formally called a resonator or resonating chamber and attenuates low frequencies both by diffusion and phase cancellation. The PE gives you the classic bimmer sound. As it gets broken in, it will get pleasingly louder, too loud for some people. But, I think it's the best mod I've done so far.

Ah, gotcha... so the diagram above is kind of misleading. I see from this photo there's no real center muffler / resonator, it's just a pipe now:


http://www.ecstuning.com/BMW-E90-330....0L/ES2159240/

Originally Posted by EndOfAnEra

Do the PE and secondary cat delete, that's what I have and love it

Cool! The secondary cat delete, does the shop just use some standard tubing to replace that section and weld them in?

And did you notice any trade-offs in deleting the secondary cat?

[EndOfAnEra]

I bought these:

http://afepower.com/shop/details_new...rtno=49-36319&

and the most power gained will be from deleting the secondary cats

[fravel]

Originally Posted by sport330i6spd

Cool! The secondary cat delete, does the shop just use some standard tubing to replace that section and weld them in?

And did you notice any trade-offs in deleting the secondary cat?

You've got a couple options for this. Simply cutting out the cats and welding in new pipes is certainly one of them. I'm a DIY kinda guy and I don't have access to welding tools, so I purchased a set of the AFE race pipes that EndOfAnEra linked to (search around because I paid less than $250 through Amazon). Those will bolt directly onto the exhaust manifold and you can remove the entirety of the stock exhaust from the mid-pipes back. The BWW PE can then be clamped directly onto the AFE pipes.

The only downside I've noticed thus far is some minor drone when at cruising speed AND going uphill. Exhaust smell isn't noticeably stronger, MPG actually seems to have gone up.

[Phil325i]

Just for completeness and the benefit of anyone reading this from Europe: what's been said above is fine for the N52 engine (port injected) but in Europe the NA engine (the N53) has direct injection, with a NOx catalyst/sensor/ECU installed after the secondary cats (item 1 in the picture below), so PE consists of the rear box only, not the center pipes.

[Taskmaster]

It's an expensive muffler.

[Kgolf31]

Personally, I see no benefit from doing secondary cat deletes with OE headers.

[EndOfAnEra]

Not sure why you feel that way ^ I didn't feel much of a performance difference when I installed the PE, but when I added the afe race pipes which deleted the secondary cats, I was able to feel quite a difference in performance...even with OEM headers.

[chris82]

I'm very jealous you e90 folks get all that piping, our PE for the 128i is just a muffler . . . .

[jc5988]

Originally Posted by EndOfAnEra

Not sure why you feel that way ^ I didn't feel much of a performance difference when I installed the PE, but when I added the afe race pipes which deleted the secondary cats, I was able to feel quite a difference in performance...even with OEM headers.

yes, big difference through out entire rev range for my afe mid too. PE does freeup the backpressure, but only when you pair it with mid pipe or header.

[krahooligan]

ok. next question, im in southern California. and ive been reading the law, and I don't see anything about secondary cats... is taking my secondary cat out illegal in the state of California? I have primaries on...

[Fume]

Originally Posted by krahooligan

ok. next question, im in southern California. and ive been reading the law, and I don't see anything about secondary cats... is taking my secondary cat out illegal in the state of California? I have primaries on...

I think pretty much every state in the US require emissions related parts to not be removed. Even if you replace with high performance cats, that would still be illegal.

That said, most states also do emissions tests with OBD2. I believe in our cars, removing secondary cats doesn't cause any codes to be thrown so as long as they don't do a visual inspection, you should be able to pass the test. However, even if you can pass the test, it's still technically illegal to tamper with the catalytic converters.

[sport330i6spd]

Originally Posted by fravel

You've got a couple options for this. Simply cutting out the cats and welding in new pipes is certainly one of them. I'm a DIY kinda guy and I don't have access to welding tools, so I purchased a set of the AFE race pipes that EndOfAnEra linked to (search around because I paid less than $250 through Amazon). Those will bolt directly onto the exhaust manifold and you can remove the entirety of the stock exhaust from the mid-pipes back. The BWW PE can then be clamped directly onto the AFE pipes.

The only downside I've noticed thus far is some minor drone when at cruising speed AND going uphill. Exhaust smell isn't noticeably stronger, MPG actually seems to have gone up.

Awesome - planning to go the DIY install route too, were there any non-included parts or tools you needed for the job? (Fasteners, gaskets, hangers, whatnot...)

[Kgolf31]

Originally Posted by EndOfAnEra

Not sure why you feel that way ^ I didn't feel much of a performance difference when I installed the PE, but when I added the afe race pipes which deleted the secondary cats, I was able to feel quite a difference in performance...even with OEM headers.

You're deleting 200 cell cats, which are minimal.

OEM Cats are IIRC 500 cell.

[Taskmaster]

I would do the AFE pipes, just for the sole reason of allowing you to undo the removal. With headers, no secondaries and PE, it's said the car is too loud.

[fravel]

Originally Posted by Kgolf31

Personally, I see no benefit from doing secondary cat deletes with OE headers.

I really only did the 2ndary delete with the AFE pipes because it turned the project into an easier DIY job that would also add some sound. If I could have just unbolted the stock exhaust and bolted the PE on byself I don't think I would have bothered with the AFE pipes.

Originally Posted by sport330i6spd

Awesome - planning to go the DIY install route too, were there any non-included parts or tools you needed for the job? (Fasteners, gaskets, hangers, whatnot...)

Yeah, you're going to need new gaskets for the joint between the mid-pipes (#6 on first diagram of opening post, 2x) and you'll want new nuts (#7, 4x) too. I pre-purchased replacement studs too (#10, 4x) and I was glad I did because I ended up having to cut/drill one of them out because it sheared off when I was taking off the old exhaust. The other 3 were fine and they are splined in place so if you don't absolutely have to replace them I wouldn't bother.

You'll also need 2x 55mm exhaust clamps to mate the PE to the midpipes, and maybe one for the PE itself. I bought my PE used so it came with the muffler and the "resonator" pipes already clamped together - I'm not sure if you'll need to buy that clamp (#4 on BMW PE diagram) or if it comes with the PE.

Hangers just swap over from the old exhaust. You'll need male and female torx bits to loosen the hangers from the car though, and I ended up having to use crow's feet to actually tighten the midpipes down to the exhaust manifold, so you might want to have a set of those handy.

[sport330i6spd]

Excellent. Thank you all for the awesome advice.

[Efthreeoh]

I'd suggest one more tool, which is a exhaust hanger removal pliers. It makes removing stuck-on hangers a lot easier. Most auto parts store sell some version of this: