[E90 335xi]

UPDATE: See post #9 below for post PE-mod results, review & additional questions.


Hi All,

I've searched this topic countless hours and now have an appointment next week to do the PE mod at a local shop that can do it.

I've seen The PDF and it says that E90s need to replace the resonator with an X-pipe. Do I correctly understand that said resonator is before the mufflers?

I know what replacing the perforated straight parts of the mufflers with a non-perf straight pipe does (gives PE-like exhaust sound), but what does replacing the resonator with an x-pipe do?

My goal is to have the PE-sound, with lift-throttle burbles, but no raspyness, and no drone. I don't have catless DPs... maybe in the future, but just doing the PE mod for now.

I also plan on leaving the fiberglass packing in the mufflers after replacing the perf-piping with straight pipe... as I believe that will minimalize drone. Am I right?

Lastly, does doing the PE mod, replacing the resonator with an x-pipe, and leaving the packing in the exhaust achieve that PE sound with burbling?

Please educate me on the resonator/x-pipe issue, and anything else I may need to tell the shop at my appointment (in order to achieve the my goal as stated above).

Thanks!

[Sidewinderpb]

Not sure about the e90, but I have an e92 with the PE Mod. Took my downpipe off a few months ago because it's been in and out of the dealership, and the sound is weak. Infinitely better with a catless downpipe. It still burbles without the downpipe, but they're not very audible.

[melloww22]

I went back to stock from FBO because the dealer refused to fix HPFP and Fuel Rail Sensor. I feel my car lost its heartbeat and rhythm.

[Sidewinderpb]

Originally Posted by melloww22

I went back to stock from FBO because the dealer refused to fix HPFP and Fuel Rail Sensor. I feel my car lost its heartbeat and rhythm.

Exactly what I did for the same reason, along with several other issues.

[E90 335xi]

I don't have warranty issues though.

Can anyone with an N55 E90 that did the PE mod confirm what they did with their resonator?

[Sidewinderpb]

This should help:

http://www.e90post.com/forums/showthread.php?t=977077

Cheers to Glowin

The .pdf also includes a link to the original thread.

[E90 335xi]

Cheers to Glowin indeed.

Some quotes from the PDF which have prompted me to ask the questions in this thread, which apply specifically to E90 (not E92):

Replacing resonator with X pipe (if you have an e90. e92's don't have a resonator). A 2.5” stainless Xpipe will work

*Please note that the internal muffler resonator is different
than the resonator on the e90 that sits about 18” before the mufflers

The e92 already has an Xpipe, whereas the e90 has a resonator. Therefore, e92 owners don’t need to install an Xpipe

I think I'm arriving at my own conclusion that the E90 pre-muffler resonator should be replaced with an x-pipe. Was just wondering what impact doing so has on sound. Likely makes it louder I guess.

[weehe126]

Slightly off topic, but I could have swore I had an x-pipe before my mufflers when i was under it to swap downpipes. Now I will need to go check again lol. (yes I have an E90)

[E90 335xi]

Update: did the PE mod. The resonator is in the driver's side muffler, not 18" before the mufflers like the PDF says. At least that's the case on my N55 E90. I left the packing in there. The shop added a bit of fire-resistant-wool-type packing to even out both sides (there's more packing on the passenger side muffler which doesn't have a resonator).

Impressions: kind of a waste of money, even at 1/4th of the price of BMW PE. Not sure if it's cause I left too much packing in the exhaust, but the sound is maybe 10% louder than the factory exhaust at most. Even with all the windows down, I can't hear any exhaust burbles whatsoever. At very light throttle, I can hear the engine itself more than the exhaust note, and anything above 15% throttle, all I hear is my BMS intake and the blow-off sound. The intake/blow-off sound is 5X louder than my exhaust. On the bright side, I have zero drone.

Question 1: did I go wrong in leaving too much packing in there?

Question 2: will deleting the secondary cats help?


Also, the PDF talks about E90s having a resonator 18" before the mufflers... maybe that's for N54 E90s only. My N55 E90 doesn't have a resonator before the mufflers, rather it's in the driver's side muffler. This is what my N55 ZE90 exhaust looks like:

[Sidewinderpb]

Downpipe

[E90 335xi]

Originally Posted by Sidewinderpb

Downpipe

Yes, that's the short answer; but it doesn't answer my questions above.

Not really interested in having a catless DP given the smell.

[Sidewinderpb]

Originally Posted by E90 335xi

Yes, that's the short answer; but it doesn't answer my questions above.

Not really interested in having a catless DP given the smell.

There is a smell for a solid one minute on cold starts - that's really it.

[E90 335xi]

Originally Posted by Sidewinderpb

There is a smell for a solid one minute on cold starts - that's really it.

Hmmm really eh...

[weehe126]

If you keep the secondary cat i doubt there will be much smell.

[Ramsey]

Originally Posted by E90 335xi

I don't have warranty issues though.

Can anyone with an N55 E90 that did the PE mod confirm what they did with their resonator?

I did the PE mod last summer. From what I remember, I just had the perforated pipes replaced with straight pipes. Also took out some of the sound deadening suffing removed out of the mufflers.

I do not recall doing anything with the resonator.

The result has been very good, cold start is very aggressive, car gurgles on 2nd and down shifting is noticeably heard compared to stock.

[CantCatchMe]

I'm putting my catless DP on next weekend mated with my PE, I plan to keep the secondary cats for the smell and chances of drone. Just get the DP.

[einbruch10]

Originally Posted by E90 335xi

Yes, that's the short answer; but it doesn't answer my questions above.

Not really interested in having a catless DP given the smell.

Buy 2 model 1792 resonators from vibrant and replace the secondary cats with those. It will not produce the catless smell as the primarys are still there. Also buy a nice x pipe to replace the center section on your exhaust (tell the shop to use scrap 2.5 inch piping to help) and you should achieve what you are looking for. The video on YouTube of the tiag sedan in the garage has exactly that done. Only exception being he has downpipes which probably adds 10-20 decibels, but you'll get the crackles and pops.

[E90 335xi]

Update: ended up getting VRSF DP anyway, and the exhaust is quite a bit louder. Pleasantly surprised that there's practically zero smell of gas... perhaps because I have secondary cats, perhaps because I'm running about 35% ethanol.

Thanks for the information einbruch10. Any chance you know what the difference is between the factory x-pipe (which I believe you refer to as the center section), and an aftermarket/custom x-pipe? And would replacing that x-pipe alone augment the crackles and pops?

[Longdoggy]

Originally Posted by E90 335xi

Update: ended up getting VRSF DP anyway, and the exhaust is quite a bit louder. Pleasantly surprised that there's practically zero smell of gas... perhaps because I have secondary cats, perhaps because I'm running about 35% ethanol.

Thanks for the information einbruch10. Any chance you know what the difference is between the factory x-pipe (which I believe you refer to as the center section), and an aftermarket/custom x-pipe? And would replacing that x-pipe alone augment the crackles and pops?

I'm curious too about the x-pipe. I'm really not interested in doing DP. I don't care at all about the smell, I actually like it. And I would welcome stage 2. However, New York emissions and my CPO won't fly. Given I have an xDrive I hear DP install is a bitch also.

I'd like to know the effect of the x pipe if anyone can share.

I have an appointment to do the PE mod next week. I definitely want more sound and burble if possible. But I am not quite going for all out down pipe loudness.

Wondering how much of the packing should be taken out to make sure I get the best sound out of this job?

[Revn29k00]

I have many of the same questions but I have just installed the BMW PE exhaust since it is so cheap now. I too am debating what to do with the x pipe and resonators. Not considering DP's since this is my daily driver. How much will the x-pipe install change the sound? By the sounds of it no one can answer this question so far.

On my next weeks vacation in July I plan to install the x pipe so I can update you guys. Can you guys recommend any particular x pipe? I see plenty on ebay that are fairly inexpensive.

[E90 335xi]

Originally Posted by Revn29k00

I have many of the same questions but I have just installed the BMW PE exhaust since it is so cheap now. I too am debating what to do with the x pipe and resonators. Not considering DP's since this is my daily driver. How much will the x-pipe install change the sound? By the sounds of it no one can answer this question so far.

On my next weeks vacation in July I plan to install the x pipe so I can update you guys. Can you guys recommend any particular x pipe? I see plenty on ebay that are fairly inexpensive.

Thanks for taking this on, I'll stay tuned as I'm curious about your results.

[shirtpants_]

what ever happened with this? anyone have any updates? I plan on getting a local shop to do this later this week. Ill let everyone here know how it goes.