[flash]

well, i've finally found the time to get in and play with the system again. what i have now provided the most power, but it's a bit louder than i want. i must be getting old, but i just don't want to hear the exhaust all the time. it would be one thing if it were way in the background, but it's a bit more present than that. i want to hear it when i am on it, so i can "feel" the car, but not when i am cruising.



so, i think i found a muffler that will knock it down. not sure what it's going to do to power yet though.



film at 11.



lol - side note - after this round, i think i will have spent more on exhaust systems and testing than most current owners spent buying their car.

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[flash]

complete fail. ugly, even louder, just plain old complete waste of time and money. it smoothed out the tone up to about 3k or so, but made a whole lot more of it after that. the weird thing was that the brief test drive didn't show those results. it got worse as i drove it more. unfortunately i gave away my muffler, thinking i had nailed it. going back tuesday to put back in a new muffler just like i had. i think i'm just going to have to learn to live with it. there does not seem to be any solution to the sound, that also flows well enough. this is really annoying.

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[williamoss]

try stuffing your ears with cotton

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[flash]

that rather defeats the purpose of the now $6000 i've spent on the stereo, doesn't it?

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[Cloud9...68]

What about active sound cancelling? I'm sure adapting a sound-cancelling system to the interior of a car, particularly a convertible where the sound signature is drastically different with the top up vs. down, would be extremely complicated, but I'm wondering if the technology has advanced enough to bring it within the realm of feasibility.

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[flash]

due to the level and frequency of the offending sound, it would take a LOT of power to cancel it.



the problem is that no straight through muffler will knock down the sound enough, and other than what i had, that's really the only thing out there that flows enough. every single one i have heard is way too loud and droning. anything that would knock down the sound is a huge compromise in performance. i don't want to really hear the exhaust at all when i am cruising. i only want to hear it when i am on it. but, i don't want to cost a bunch of power either. i just can't find anything that reduces the level enough, without losing power.



a large component of the problem is the fact that this is a convertible. that comes with a certain amount of exhaust noise. the same system in a hardtop is not nearly so bad.



i am still poking around, but i think i have to go back to what i had, buy another one of the same muffler i had, and reinstall it and call it "done". i may just have to give up the car. it isn't making me happy. what i am really looking for is the sound i have in the SL550. i just don't know that i will ever get it in the 968.



the next thing i am going to look at is more sound deadening under the car. i may be able to knock down more sound by modifying the heat shield to be a sound absorber.

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[Bulti]

And what about an active valve in the exhaust system? You can adjust it to whatever mood you're in at any given moment. If you want to step on it, you probaly do not mind a (very) sporty sound, and when taking it easy, those few horses that get muffled along with the noise can't hurt either.

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[flash]

very old school (dating back to hot rod days with lake pipes) but, i tried that too. stuck the dynomax VT in there for a minute. worst sounding piece of crap i have ever heard. lost 15hp in the process too. one of the problems with this type of muffler is that the car is supercharged. that makes for more flow. that pretty much keeps the flapper open if you even tickle the pedal. there is even a point where it is on-off-on-off-on-off, and of course it is just about at freeway cruising. very annoying.

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[Bulti]

What I meant was a valve that you can operate with a switch, like in many sportscars today. Something that can be put into an exhaust you do like (and provides the flow needed), but when activated quiets everything down.

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[flash]

i remember hearing of a car recently that had something like that, but certainly not "many". i understand the concept, but question the viability. also, having to flip a switch in order to step on the gas for real power, sounds problematic. i suppose i could put a switch in the accelerator pedal that activated the valve at a certain point, or perhaps even tie it to a load map in the ECU, and as i type this, i can see how i could make it work, but it seems like a pretty complicated workaround.

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[Bulti]

Come on Flash, put your back into it! Screwing around with the ECU a bit, what's the hassle?



Ok, shutting up...

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[quick968]

Flash have you looked at any of the Corsa RSC type mufflers? They have great Corvette systems, dual mufflers, so maybe one of theirs might fit the bill. I had one on my Cummins, obviously diesel is a different critter, but their RSC gimmick does do what they say. My truck has no drone at all running hwy speeds, but as soon as you get on it, it's sounds just amazing. Anyway, you've prolly investigated them before, just thought I'd mention them.



Cheers

Mikey

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[flash]

yes - got their marketing CD a while back.



again, NO straight through muffler will work. it absolutely must turn around or hit a series of baffles, or something to that effect. i've tried just about every straight through muffler out there, with the same results on each and every one, regardless of how many internal tubes, flared cones, perforations, or whatever.



if dynamax, or anybody else, made a reverse flow that could handle the flow, i'd run that

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[MB968]

From my years ago work on noise control of machinery (when they put in the 90 dbA max for an 8 hour day) I'm not surprised that you're finding a straight through will not work. The air noise from a large electric motor alone could drive us out of compliance. The materials you can line a straight thru path will give some attenuation to the high frequencies if you have enough (length) of it. But the only way to deal with a lot of the noise is to make it turn several corners. On my Ford/Mazda, my custom exhaust (3" mandrel) used both a straight thru in conjunction with a muffler with corner turns. Gave it a nice deeper sound with no objectionable sounds/resonances.

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[flash]

that is essentially what i have now. it's just not quite enough to really make me happy. i really don't want to hear it at all when cruising down the freeway.

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[ds968]

[quote name='flash' timestamp='1393112448' post='155405'].it's just not quite enough to really make me happy. .[/quote]



Hmm, now there's a statement where by replacing "quite" with "quiet" would not really change the message, LOL .

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[williamoss]

WELL SINCE YOU SPENT$6,000 ON A NEW SOUND SYSTEM. YOU SHOULD WEAR BOSE NOISE CANCELLING HEADSET WHILE YOU DRIVE, GREAT SOUND REPRODUCTION ND NOISE CANCELLING AT THE SAME TIME. MiGHT ALSO BLOCK THE SOUND OF THE SIREN BEHIND YOU FOR WEARING THEM WHILE YOU DRIVE.



"BUT OFFICER I HAD TO WEAR THEM BECAUSE MY EXAUST IS TOO LOUD" YEAH RIGHT............

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[Carl968]

Billy Boat has an exhaust system for corvettes with a switch for loud and not so loud exhaust noise. Actually pretty nice on the vettes.



Carl

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[flash]

don't get me started on billy boat. singularly underwhelmed by their products, but i have heard about the system. i would want it to be controlled, not by a switch, but automatic, as the need arose for performance. i think i know how to do it, but frankly, i think i'd just rather it was quiet. i really like the sound in the SL550. i wish i could get that out of the 968.



going back this week to correct, and maybe try one more thing. when i leave there though, i'm done and it will be what it will be. if i can live with it, fine. if not, i'm selling the car.

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[MC968CS]

Funny, I too have a rear straight through muffler and though it seems to be good for the HP I am 'over' the volume. It actually smooths out above about 4000rpm, but still too much for me now. I want to just change the rear muffler.



Any tips, for a NA car, what to go for in terms of a muffler thats not as loud as straight through, but flows well Flash? Its a car mainly used Sunday am and track days, and straight through is killing me.

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