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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Mon, Dec-03-2018, 11:12:12 PM   #61
matty088
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Default Re: Rasp

I think the part that I am struggling with is the fact that I need to keep my cats. I totally see value in adding headers to remove the cats. But is it really worth adding headers when moving the cats to section 1? Are people doing this? Is it worth the 2000 investment? I understand that some after market and the euro cats are 200 vs the stock which is 400. But isn’t even 400 considered pretty high flowing as far as oem cats are concerned.

The euro car is rated at 10 more hp than American spec. That’s not much of a diff at all. Is this due to the euro headers and cats.

Once again ty for everyone’s patiences in helping me.

Last edited by matty088; Mon, Dec-03-2018 at 11:30:02 PM.
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Old Mon, Dec-03-2018, 11:16:02 PM   #62
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Default Re: Rasp

Quote:
Originally Posted by Twiin View Post
if what you want is to eliminate the rasp put a section 2 resonated, I changed my supersprint x pipe resonated section 2 by SS 2.5 Twin-Pipe not resonated and now I have much more rasp than before
Iíll definitely do that if I end up with more rasp than I want. But Iíd rather go with a setup with lower rasp and only do the resonators if I have to.

I guess I should have asked earlier. Whatís the biggest culprit to getting rasp? Is it the removal of the cats?
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Old Mon, Dec-03-2018, 11:27:40 PM   #63
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Default Re: Rasp

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Originally Posted by Dr M3an M3 View Post
If Supersprint is out of your price range even after discounts (totally understandable), I'd recommend OE Euro headers. They will have perfect factory fitment making installation painless and perform great for their price. You can usually get them pretty cheap, used on here if you don't want to buy them new (which there isn't any reason to, as long as guys keep offering used sets). I can only speak for the single set of SGT headers I helped a local friend install. Fitment was terrible. If the engine hadn't been pulled, the set we received would never have been possible to install. Even with the engine out of the car it took a LOT of work trying to to pry them on to fit correctly. They practically needed to be cut and rewelded. That same friend ended up replacing them soon after with Supersprint. If you want CHEAP...I'd check out the Megan headers. Quite a few guys have had luck with them. Fitment seems to be hit or miss, but the price is pennies on the dollar compared to SGT. They look to be exactly the same as AP headers and likely made in the same factory. I don't "recommend" personally, as I have zero experience with them, but other guys have had great things to say and it might be worth your time to read the thread that was made on them. I DO recommend used OE euro headers, you won't have any issues with those.

Doesn't get much better than this raspy beast when it comes to noise...Dixis Titanium. Very exotics.
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Not all stepped headers are equal. Supersprint are multi-stepped and CPI are single stepped. From reading Obioban's posts, the stepped location on the CPI were arbitrarily placed and ended up losing low end torque and performing worse than OE Euro. Take that with a grain of salt, as I don't have any dynos to source, but I have seen this mentioned over and over again about the CPI.
Great info ty very much. So. I will go with the euro headers. I will post a wtb thread although I may just buy them new.

As far as euro section 1 cats. It seems like those you canít buy new?? That sucks. Buying those used seems challenging as they do have a shelf life so to speak. Are they available new anywhere ?
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Old Mon, Dec-03-2018, 11:39:07 PM   #64
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Default Re: Rasp

I was under the impression that eliminating rasp was achieved at the section 1 pipe. Sounds like you created more rasp by going with non-resonated section 2 pipes but does going with a resonated section 2 reduce rasp from the stock setup or does the rasp eliminator section 1 achieve that?




Quote:
Originally Posted by Twiin View Post
if what you want is to eliminate the rasp put a section 2 resonated, I changed my supersprint x pipe resonated section 2 by SS 2.5 Twin-Pipe not resonated and now I have much more rasp than before
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Old Wed, Dec-05-2018, 07:54:20 PM   #65
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Default Re: Rasp

Quote:
Originally Posted by matty088 View Post
Iíll definitely do that if I end up with more rasp than I want. But Iíd rather go with a setup with lower rasp and only do the resonators if I have to.

I guess I should have asked earlier.Whatís the biggest culprit to getting rasp? Is it the removal of the cats?
I'm not sure, I also thought it would be to eliminate the cats, but with cats (200 cell SS race) and section 2 not resonated there is still a lot of rasp
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Old Wed, Dec-05-2018, 07:57:46 PM   #66
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Default Re: Rasp

Quote:
Originally Posted by M3Lyfe617 View Post
I was under the impression that eliminating rasp was achieved at the section 1 pipe. Sounds like you created more rasp by going with non-resonated section 2 pipes but does going with a resonated section 2 reduce rasp from the stock setup or does the rasp eliminator section 1 achieve that?
I can not say, my current configuration is full supersprint and it is with what I have done tests, the only thing I can say that even using cats if section 2 is not resonant a large amount of rasp is added
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Old Wed, Dec-05-2018, 08:10:02 PM   #67
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Default Re: Rasp

I have no resonators in section 2 but two resonators in section 1,off of an E92 m3. No rasp.
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Old Wed, Dec-05-2018, 09:35:03 PM   #68
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Default Re: Rasp

My hypothesis is that rasp is a by-product of the the firing order of the motor, exhaust pulses, and dual-exhaust configuration of the car. At the right RPM, the pulses bounce off the walls of the exhaust at just the right frequency to resonate the sound waves in a way that produces the raspy noise heard, which is likely why you only hear rasp at a certain specific rpm (around 2700-3000 rpm). Temperature gradients seem to also affect the severity of rasp; ie: when it's cold, the exhaust produces more rasp until the car is at operating temperature (even if catless).I think a full single exhaust does a lot to eliminate rasp (but there are compromises with that configuration too).

Most people add canister resonators to their exhaust system to reduce or eliminate the rasp. You can do this by either adding a resonated section 2 or resonators to the section 1. If you have cats, it's probably easier to add a resonated section 2 rather than welding resonaters to your catted section 1. Guys that have the rasp totally eliminated (even with loud mufflers) seem to have a combination of both dual resonators in the section 1 and a resonated section 2. Having a well muffling muffler will also help quite down the rasp.

I haven't seen anyone mention it on this forum, but it's common on domestic cars and the Honda S2000 came with one from the factory, but you could probably add a Helmholtz resonator or a J-Pipe to your exhaust to completely cancel and tune out the rasp (like you would for drone) so long as you calculate the rpm it comes on and plug it into the equation that gives you the length needed for the J-tube. I would love to see more on this option, but it seems non-existent for this platform.
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Old Wed, Dec-05-2018, 10:40:11 PM   #69
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Default Re: Rasp

good info.
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Old Thu, Dec-06-2018, 01:23:45 AM   #70
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Default Re: Rasp

Engine temp definitely plays a roll on my stock car. It sounds awful when it happens hence why I am hesistent to upgrade the exhaust which could amplify it if not done correctly.

At the end of the day this thread has been helpful as I have learned a lot. I am gonna go with the stock euro headers and cats. Seems like a lay up that doesn’t break the bank. My expectations are low though. I know it’s popular opinion that this is a good setup but if that’s the case then why did the euro cars make like 5hp more than the Us spec. It’s just logic. But I figure do the exhaust, intake, and tune. Even if power doesn’t tick up much I bet the car will feel and sound more sporty. I am going to keep the stock muffler. My best guess is that if I want to make decent power you need to get rid of the cats.
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Discussing Rasp in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)