Stembro Exhaust

[Rammer]

Hi,

has anyone heard of Stebro exhaust? Any feedback would be appreciated.

Thanks
Bill

http://cgi.ebay.com/ebaymotors/Porsche-BOXSTER-RACING-EXHAUST-1997-2004-BY-STEBRO_W0QQcmdZViewItemQQcategoryZ33630QQihZ017QQi temZ270110300491QQrdZ1

[JAAY]

I think it looks like a two cherry bombs and some bad piping. I have Mille Miglia exhaust and it sounds way more tuned than that. I am only going by looks and sounds of it. That sounds like a steep price too for 2 straight through civic mufflers. If you like the look of that get a GHL.

[Allen K. Littlefield]

I am with you on this JAAY, looks like two juice cans and at what a price!!! Please! I wonder what the resonance would be on this little concotion or then again it may be ok. Any buddy ever hear one of these?

Seems like the only performance increase would be the weight loss and I imagine a lot more heat would be dissipated, that being a good thing. Same with lightweight headers. I drive a tip and that adds about 100 lbs to the car and adds a second to 0-62.. I imagine a loss of weight with headers, muffler & battery would trim some time off this benchmark. Sorry for digressing.

AKL 986geezer

[Boxtaboy]

Don't know if it matters to you, but it also doesn't have the steel beams that connect from the muffler and hangs onto the cats that the OEM muffler has. These additionally support the muffler.

Well... its got lots of stickers so it must be good.

[mn box s]

Che's exhaust is much better. that looks cheep! Che's sounds sweet too.

[Rammer]

Originally Posted by JAAY

I think it looks like a two cherry bombs and some bad piping. I have Mille Miglia exhaust and it sounds way more tuned than that. I am only going by looks and sounds of it. That sounds like a steep price too for 2 straight through civic mufflers. If you like the look of that get a GHL.

Jaay,

are you happy with the Mille Miglia exhaust?

[Cloudsurfer]

Jayy-

Where did you acquire the Mille Miglia? How do you like it? Is it resonance free? Cost?

thanks

Patrick

[John V]

Any and all of this style exhaust will resonate. No way around it.

For 1,000 bucks, just go have a muffler shop build your own and spend the rest on gas.

[Cloudsurfer]

Well the problem I have, is that I have the GHL Race exhaust, which are basically straight pipes. Sounda AMAZING above 4k, but also resonates pretty badly between 2 and 3k. I have thought of the idea of cutting the piping and welding in some resonators or straight through silencers, but if I'm going to hack the thing up (I got it cheap enough I dont really care about sacrificing its value), I'd like to do some homework and insert the proper size and length devices to quiet the resonance from 2-3k.

Any thoughts on that?

Patrick

[John V]

You're not going to cancel the resonance (the "drone") by inserting more silencers. The straight-through glasspack-style silencers don't do anything for low frequency tones, and the resonance is caused by the low-frequency cylinder firing rate (CFR). I calculated it out to be about 110Hz.

The stock muffler uses helmholtz resonators with absorptive material plus long path length to attenuate the CFR. Any straight-through exhaust is going to resonate between 2-3k on the Boxster, period.

I do believe there are ways which you can eliminate the resonance using quarter-wave resonators and additional tailpipe length, plus reactive mufflers, but I don't have regular access to a welder nor do I have the desire to throw a bunch of money at the problem. Maybe someday.

[Cloudsurfer]

John-

Thank you for the much thought out response. So, essentially, in my situation the only thing I can do is swap out my GHL for a properly designed, non resonance exhaust (i.e. CarGraphic, FabSpeed, Gembella, etc)?

Patrick

[Cloudsurfer]

John-

Related to that, I had another thought:

Would it do anything to elimate some of the drone if I welded in some high flat cats into the exhaust section (that way I could do catless headers and secondary cat deletes and still be semi EPA friendly and have a happy ECU)? Would the cats do anything to attentuate the low frequency drone or are we still left with the same problem?

Patrick

[John V]

I really doubt inserting a cat would do anything at all. But I haven't tried it, so I can't say for sure.

[JAAY]

I love my exhaust. I also have the s-car-go headers. Sounds great. Yes it resinates between 3200-4000 around there. I got from Steve Timmins, Instant-g.com. The headers and exhaust came off a car he did a 3.4 in and got his headers and exhaust. As
for the price I don't know what it costs. I never really looked it up I think the headers are $2150.00, that is what there site says and the exhaust, well the site doesn't say.

[edevlin]

"Thank you for the much thought out response. So, essentially, in my situation the only thing I can do is swap out my GHL for a properly designed, non resonance exhaust (i.e. CarGraphic, FabSpeed, Gembella, etc)?"

I would be careful with which of the exhausts you choose. I have headers and 100-cell cats, and I found that the Gemballa muffler and the sausage-style Dansk muffler both give that 2-3K resonance that drove me nuts.

I finally settled on a Dansk OME-style "sport" muffler, which has higher flow rates than the stock muffler. It is only slightly louder than the stock muffler and has no resonance issues.

BTW, the "butt dyno" seems to registrar a difference with the higher flow rate with this latest Dansk muffler. With the stock muffler the car would make a noticable increase in performace at 5.5K. Now, it pulls strongly from 4-6.5K without that transitional jump at 5.5K, something is going on.....

Ed

[Cloudsurfer]

My problem is I love the sound of my GHL from 3K up, its gorgeous. However, the resonance between 2 and 3 is a bit annoying.

How much truth is there in what I've heard in that doing the secondary cat bypasses decreases the resonance with open exhausts like this?

Patrick

Originally Posted by John V

You're not going to cancel the resonance (the "drone") by inserting more silencers. The straight-through glasspack-style silencers don't do anything for low frequency tones, and the resonance is caused by the low-frequency cylinder firing rate (CFR). I calculated it out to be about 110Hz.

The stock muffler uses helmholtz resonators with absorptive material plus long path length to attenuate the CFR. Any straight-through exhaust is going to resonate between 2-3k on the Boxster, period.

I do believe there are ways which you can eliminate the resonance using quarter-wave resonators and additional tailpipe length, plus reactive mufflers, but I don't have regular access to a welder nor do I have the desire to throw a bunch of money at the problem. Maybe someday.

I'd like to hear your ideas on it, and maybe I'll build it. I have all the tools necessary. You help me design it and I'll build 2; one for me and one for you What do you say? Or do you think there really isn't much power to be gained, and not worth the effort? BTW, I plan on forced induction later on...



I installed Che's exhaust and it sounds racy for sure (PM me if anyone wants to buy it before I put it up on Ebay and I'll give you the details). Just not my taste. I thought I would try it, but it's too loud for me. I like stealth. All I wanted was some more HP.

[Cloudsurfer]

Well I was hoping to get rid of my resonance by installing the FabSpeed system. It is much better, but still has resonance between 2 and 3k. I think with these cars, due to the short piping length and the cylinder firing rate.

Patrick

[SRQ Boxster]

PM sent boxsterz.