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bimmer007
Fri, Jan-28-2005, 04:49:45 PM
Have any of you attempted to just modify the existing OEM section 1 peice so that it's 2 straight pipes, instead of having one resonator? Me and a buddy were talking about this, and it seems that if the rasp is coming from that resonator, wouldn't you just be able to cut that resonator out, and weld in a peice so that it's just straight?

I know, I'm trying to be cheap, but I can't justify spending $500-$1000, on a stupid peice of bent metal tubes that doesn't add any performance and just eliminates that annoying sound. And yes, I tried doing a search, but couldn't really come up with much other than people are putting in a magnaflow muffler or something in there.. But I think that's to prevent it from being so loud?

TIA

Beowoulf
Fri, Jan-28-2005, 05:16:11 PM
Removing the resonators will not get rid of the rasp, it will probably just make it louder. Midpipes without resonators do add power. I think you are talking about the Rasp-X which is a whole different ball game.

Rob's Archive
Fri, Jan-28-2005, 05:17:39 PM
actually the rasp is not only a design from the midpipes but also from the cats being integrated into the headers...

I think that BMW put that resonator in there because if you took it out, it would make the rasp worse. I have heard of people adding new resonators to both sides and supposedly getting rid of the rasp.

http://www.uucmotorwerks.com/raspx/raspx_comparison.jpg

from that picture, i see what you are trying to do but the reason that the stebro and the raspX works is that they put an equal amount of resonators on both sides of the exhaust flow...not take out all the resonators. That would be like using a SS Spipe and a SS X/pipe without resonator. It would change the rasp but it would still be there and the overall volume of the things would go up.

bimmer007
Fri, Jan-28-2005, 05:27:26 PM
That kind of sucks, because me and Dan thought it would have gotten rid of the rasp. Hmm.. maybe i'll have to just bite it, and pick up the stebro in 3 months, when it actually is available--haha. or find a deal on a used rasp-x. Would the rasp-x make the exhaust note any louder? I would like to have the eisenmann race scream just a tad bit more. Maybe I should go with the stebro + Eisenmann section 2.

Thanks for the reply guys.

Rob's Archive
Fri, Jan-28-2005, 05:44:55 PM
both stebro and the raspx will reduce overall volume tone as you will loose the "volume" that the rasp creates. If you do the section 2 it should help you regain that "volume" loss.

RydeWitM3
Fri, Jan-28-2005, 08:50:15 PM
Have any of you attempted to just modify the existing OEM section 1 peice so that it's 2 straight pipes, instead of having one resonator? Me and a buddy were talking about this, and it seems that if the rasp is coming from that resonator, wouldn't you just be able to cut that resonator out, and weld in a peice so that it's just straight?

I know, I'm trying to be cheap, but I can't justify spending $500-$1000, on a stupid peice of bent metal tubes that doesn't add any performance and just eliminates that annoying sound. And yes, I tried doing a search, but couldn't really come up with much other than people are putting in a magnaflow muffler or something in there.. But I think that's to prevent it from being so loud?

TIA

that is exactly what i did, and the rasp still exists but its alot less existant. as long as you leave section 2 alone and u remove the resonator from section 1 you will notice a diff in the power band and the rasp will be alot less if i remember correctly, with only the resonator removed from section 1 the rasp was only existant between a certain range of rpm, i think from 3-4 or 4-5, cant remember. and it is alot cheaper cost me 40 bucks vs 400, lol.

TIA

bimmer007
Fri, Jan-28-2005, 10:43:27 PM
that is exactly what i did, and the rasp still exists but its alot less existant. as long as you leave section 2 alone and u remove the resonator from section 1 you will notice a diff in the power band and the rasp will be alot less if i remember correctly, with only the resonator removed from section 1 the rasp was only existant between a certain range of rpm, i think from 3-4 or 4-5, cant remember. and it is alot cheaper cost me 40 bucks vs 400, lol.

TIA

well, now if you'd just sell me ur supersprint section 1, i wouldn't have to go through all the trouble's :wave: but i still think i'd have the rasp as it is essentially a straight pipe as well. but you're saying the oem midpipe minus the resonator will give me noticeable power throughout the band? interesting, well i guess it would be less restrictive, so maybe, but i doubt it would be too noticeable since the diamater of piping is still the same.

anyone else done this? i'm sure more people have thought about doing such??

RydeWitM3
Sat, Jan-29-2005, 12:46:52 PM
well, now if you'd just sell me ur supersprint section 1, i wouldn't have to go through all the trouble's :wave: but i still think i'd have the rasp as it is essentially a straight pipe as well. but you're saying the oem midpipe minus the resonator will give me noticeable power throughout the band? interesting, well i guess it would be less restrictive, so maybe, but i doubt it would be too noticeable since the diamater of piping is still the same.

anyone else done this? i'm sure more people have thought about doing such??

i dont have the supersprint section 1 i have the supersprint section 2 for sale, plus i do have the resonator removed on my stock section 1, and after i did it the first thing i noticed besides less rasp (alot less) is the how much better 3rd would pull, and second of course, but more noticable in third.

TIA

glenspeed
Sat, Jan-29-2005, 09:50:11 PM
I have the Eisenmann sec 1, Supersprint X pipe and muffler. I recently took off the Eisenmann and went ghetto with the OEM midpipe 1 and cut off the resonator, so the Eisenmann is available for sale. I figure I'd go cheapo and recoup the cost of the Eisenmann and when I go to headers I can change to race cats at that time.

The OEM midpipe with resonator removed did not sound as aggressive as the Eisenmann midpipe 1 even though both did not have the resonator. I can say that the Eisenmann material is superior and lighter and definately sounds better. You really do get what you pay for...
The rasp is definately more noticeable on part and full throttle. It comes on quicker that without the resonator for sure. Hope that helps.

BTW, Eisenmann Sec 1 is available...

ArtM3
Sat, Jan-29-2005, 10:08:06 PM
Looking at the picture got me thinking:

why only 1 front resonantor?
why that side? and not the other, and everything else is symetric

it's got to be to equalize the load the engine sees thru the catalysts, because one set of pipes is longer, catalyst closer, etc., so they add a little back pressure on the one with less pressure drop, i.e., shorter, etc.

that way you can balance flow thru the catalysts.... :nixweiss:

...I think that BMW put that resonator in there because if you took it out, it would make the rasp worse. I have heard of people adding new resonators to both sides and supposedly getting rid of the rasp.
http://www.uucmotorwerks.com/raspx/raspx_comparison.jpg
...

glenspeed
Sat, Jan-29-2005, 10:40:52 PM
got me thinking too so here's my theory. For one thing the resonator isn't that restrictive, it's pretty free flowing so it wouldn't unbalance to a great degree IMO. The other thing is the cats in the manifold aren't equalized either as distance on one cat versus the other is different, so maybe this one resonator balances out that difference...then you gotta look at the muffler and think that the passenger side outlet pipes have a greater distance to get out and maybe one of those pipes feeds more exhaust out that pipe...

ArtM3
Sat, Jan-29-2005, 11:13:56 PM
got me thinking too so here's my theory. For one thing the resonator isn't that restrictive, it's pretty free flowing so it wouldn't unbalance to a great degree IMO. The other thing is the cats in the manifold aren't equalized either as distance on one cat versus the other is different, so maybe this one resonator balances out that difference...then you gotta look at the muffler and think that the passenger side outlet pipes have a greater distance to get out and maybe one of those pipes feeds more exhaust out that pipe...

yep, I think so, after it get's past the x-over tube, second resonator and muffler it's all mixed and balanced...I bet changing that negatively affects performance to some degree, efficiency, etc. but less restriction might overcome this loss for a net gain...

when you focus your ear on the rasp, it sounds like it's comming from it...I need to put it on a lift and see... :hmm:

glenspeed
Sun, Jan-30-2005, 12:55:45 AM
yep, I think so, after it get's past the x-over tube, second resonator and muffler it's all mixed and balanced...I bet changing that negatively affects performance to some degree, efficiency, etc. but less restriction might overcome this loss for a net gain...

when you focus your ear on the rasp, it sounds like it's comming from it...I need to put it on a lift and see... :hmm:

I think the rasp comes mainly from the manifold. I've got the straight pipes now and I have more rasp...(that's great because I actually like it)

MattsMthree
Sun, Jan-30-2005, 05:00:15 AM
As well as the stock muffler if anyone wants them. It's free for anyone who doesn't mind picking them up...


Best regards,
Matt

daytonaviolet
Sun, Jan-30-2005, 06:56:14 AM
theres a member on the forum who lives local to me (ericshun) .. he claims he removed his rasp by adding another resonator. i plan to meet up with him, listen to his exhuast and take pics to see how he did it.. perhaps he can explain to us in more detail how he did it.


here's his orig thread with sound/vid clip http://www.m3forum.net/m3forum/showthread.php?t=49096