911 exhaust issues

[81 911 SC]

I ran through the search and never really found the answer to my question. I have a GHL 2in 2out. It makes wonderful sounds except when cruising at 40mph in 4th gear. There is a terrible resonance inside the cabin. I am looking for a 2in 2out that does not resonate. Any suggestions or experiences?

[IROC]

FWIW, I have a Triad 2-in 2-out (street version) and it has essentially no resonance (especially when compared to the Dansk I had previously). This Triad is extremely quiet, yet has a really nice exhaust "note". It is also very well made. I was very impressed with the build quality, also.

Mike

[mb911]

I am very well experienced in this and can tell you there is no such muffler in dual out that does not resonate in some rpm range. it all depends in what range it does it in which is depended on tire Dia, compression levels, cam overlap, gear ratio. The flowmaster,ghl, B&B designs are very similar and tend to resonate the most. the dansk,M&K,monty,bursch tend to not as much but all still have some typically at about a range depending on brand from 2100-2200 up to 2500-2600. Again depended on brand some have a broader range some have a much narrower range

[mb911]

Originally posted by IROC
FWIW, I have a Triad 2-in 2-out (street version) and it has essentially no resonance (especially when compared to the Dansk I had previously). This Triad is extremely quiet, yet has a really nice exhaust "note". It is also very well made. I was very impressed with the build quality, also.

Mike

those are cost effective alternate but they have the crossflow into brick wall effect


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excuse the drawing with spaces but the bottom is coming from the 2 ssis going into the upright section and then into the 2 sistered up glasspacks. Just my observation I do know many swear by them in reality it probably does not matter anyhow for regualer street driving

ok so the drawing is not coming up like I wanted so hopefully you get the idea

[81 911 SC]

Thanks for the info. I have CIS cams with 40 mm PMO carbs, SSI and running 16x8 rear tires with 245/45. All else considered it looks like M&K is the way to go.

[IROC]

Originally posted by mb911
Just my observation I do know many swear by them in reality it probably does not matter anyhow for regualer street driving

Well, if nothing else, he has dyno results that imply that there is nothing wrong with this design. Maybe that should be taken with a grain of salt, maybe, but he does have them. According to the dyno results, the 90dB street unit I have made 4 more hp than a factory sport muffler.

Mike

[mb911]

Originally posted by IROC
Well, if nothing else, he has dyno results that imply that there is nothing wrong with this design. Maybe that should be taken with a grain of salt, maybe, but he does have them. According to the dyno results, the 90dB street unit I have made 4 more hp than a factory sport muffler.

Mike

No offense implied (on the triad)just on a design principel it seems that way. With that back pressure built in it may very well help for hp at certain rpm ranges.. I have never tested one. But in reality the poster was asking about sound not so much hp and I brought that in I appoligize should have not complicated things..

good luck

[81 911 SC]

would you say the center outlet exhausts are louder than the "side" outlets? I do not have the rear valance on my SC and have always likes the center outlet but I am concerned about where the outlets are in relation to the impact bumpers on the SC.

[mb911]

the GT3 look alike is not bad at all and I would consider them quieter then a dual outlet(standard side outlet) by some amount4-5 dbs

no interuption with the bumper overriders either

[81 911 SC]

On the GT3 muffler, how far apart are the outlets? I like the look of the Caymen S muffler and think that would look pretty nice on an older 911.