A 'different' muffler question...
 

I am wondering if anyone has seen a serious comparison between mufflers / exhaust systems and their sound output vs. power output. Specifically I am looking to free up the exhaust on my 87 Carrera but I want it as quiet as possible. (jeeze, I know I am going to get flamed on this one :) ) I drive the hell out of the car and I don't want the cops looking up their donuts and I don't want the rice burners to think that they need to race me.

I have been thinking of putting the euro pre-muffler in place of the cat and then a quieter stainless muffler. Another idea would be a 74 style header with 1-5/8 or 1-3/4 primaries and then some sort of quieter style muffler behind it. (Something like an SSI but with larger pipes.)

Anybody tried anything like this?

Wayne

We don't know how to make them quieter. We also don't know how to reduce horsepower, make them handle more unpredictably in corners or require longer braking distances. (just being a smart@ss)

Saw a show ("Trucks on TNN") the other day, showing a switch actuated valve that switches between muffler and no muffler. Someone pulls up to you at a stop light, and the coast is clear... Flick! Vroom! Flick! Purr....

-Boyo

'74 Style headers make things louder all by themselves I think.
-Chris

(I think I stopped putting cards in the spokes when I was 12...)

I think I asked the wrong question. Has anyone ever tried a muffler and found that it was too quiet and refined? (That way you can hear the guy next to you when he asks for the Grey Poupon!)


Wayne

Boyo,
I saw that too and I'm surprised no one here has tried something like that. Have a two out muffler, but one out is mechanically closed for street driving then opened up for track. I too want a quiet or slightly louder than stock muffler, but would like more HP.

Quiet and free flowing don't usually go together. You sorta have to pick one or the other. Just by installing a Euro style pre-muffler or test pipe will increase the noise level.

I saw that too on trucks<My question would be do you have to adjust fuel mixture?And if ya do without a computer it would be sota silly

and my question would be wouldnt you have to adjust the mixture?

stealthn:

How did you make the open/close flap for the muffler?

I have a dual in/dual out BB system and I would like to be able to close the right
side when I don't need it as the resonance between 2 & 3k rpm makes my teeth
hurt. It also rattles the neighbors windows when I pull out of the driveway. :D

edit: stealth, I just reread the thread and see that you didn't actually do this yet.
Has anyone ever done a cutout flap for the right exhaust?

I use Supertrapps bolted to the SSI's on my 2.4. Will do the same setup on my 3.2 in my '73 targa. By varying the plates you can change the noise level. It also has an effect on the power band. I've seen some racing 993's using headers with Supertrapps.

My uncle has been into Porsches forever. He time-trialed (and ruined, on a mis-shift) a 912 when I was a little kid. Now he has a 993 cabriolet tip. He is definitely of the "caviar" Porsche set. Only Andial touches his car. He would probably object completely to the basic premise of this bulletin board, if he even knew it existed.

When I first pulled up to his place with my Carrera with a dual-out B&B muffler and cat bypass, he said, "Nice car, but your muffler's broken." Then he said, "Soon you'll take that piece of ***** off and put the stock one back." He also said, "Power doesn't equate with volume. If you want more power, you should call Andial and get a 'tuned system.'" I talked to Andial. They said they do SSI and Dansk for the street. They said they didn't know anything about the other vendors. They probably don't approve of them, even though they make more peak hp, because they're too loud for the street.

I think that as long as you assume that you're using some kind of dual-out headers, and that you'll chip the car appropriately, volume will equate with power - in other words, disregarding the single-in setups, the louder you car is, the more power it will make. I think we know that SSI and Dansk is nice on a Carrera. That's probably what you ought to do. It'll be louder than stock, and too loud for my uncle, I'm sure. But not too loud for most of us. I don't think it would make quite as much peak hp as my new GHL headers & dual out muffler. My new system is louder than SSI and Dansk, but less loud and less boomy than my previous stock headers and B&B dual-out setup. And it sounds much better! More "Porsche" and very like a leopard.

I can't wait to hand my uncle his caviar tiptronic a$$ on the street. It will happen!

Cheers,

pretty much what everyone else has says. If you get rid of the cat or go to headers/ssi's then you will get more noise. You can probably stay relatively quiet, but hey, I just took the muffler off of my '88 and bolted a pipe/tip to the cat. No muffler, sounds good, less backpressure (but still got the cat), and less weight. It is pretty loud, but primarily outside of the car. It's actually quieter inside the car than when I had the dual out flowmaster.

I never seen any data showing that a louder muffler beats the (original) stock muffler. Also true for the Boxster. Take a look at Bruce Anderson's book and various columns in Pano and Excellence.

Bruce also says something to the effect that "the best chip change is an exhaust change," right? And then he goes on to talk about SSIs and custom headers. I believe the basic premise of gettin more power and improving the exhaust on these cars is GET RID OF THE STOCK HEADERS & CAT. After that, the quieter whatever muffler you put on, the more it will be causing turbulence and impeding the flow of gases out of the engine. Freeflow and louder will mean more peak hp. A little more backpressure and a little less volume may put the hp peak lower on the tach. I sure don't have the data to back myself up, but I just feel & intuit (!) that if you go as quiet and restrictive as the stock muffler is, you will have just wasted a serious amount of $$ putting the better headers on there.

There are data (dyno charts) in Bruce's book showing significant hp increases in 3.2 power with various non-stock header setups.

SSIs and megaphones
 

Why use them on the street?

1) Moron drivers will hear you coming...

2) Moron drivers will move the hell outta' the way...

:)

The only direct correlation I have ever seen between a 'sport' muffler with higher noise level ... and additional power output is with the 'original' 'sport' muffler with narow-spaced small pipes, as sold by Stoddard's and AJ-USA for many years. That muffler is reported by many sources as being good for an additional 10 - 12 hp, at significantly higher noise levels, perhaps as much as 15 dBA! The Phase 9 'silencer' featured in several of BA's charts and tests on 3.2 engines ... were not designed for the street, but, rather to allow race cars to meet more stringent noise limits at tracks. They looked more like 2-stroke motorcycle expansion chambers than automotive mufflers!

<b>Although I have seen many users of Bursch, B&B, Flowmaster, and SuperTrapp's claim higher power than stock ... I have yet to see any noise test numbers coupled with dyno test numbers that support such claims!!!</b>

One switchable 'muffler' that looks like one ... but hardly provides any suppression at all ... was the 1970 racing 'silencer' provided as part of a 'rallye' power kit. and which had very large outlets directly inline with the inlets, and much larger than normal inlets designed to mate with a racing header/megaphone set I have never seen one of those mufflers, or a duplicate/copy ... for sale anywhere, but it is shown in both editions of BA's <b><i>Handbook.</b></i>

My setup is B&B headers, no cat, and a B&B dual in dual out muffler on a 3.2.

Their (B&B) dyno results show an 18 hp +/- gain with a slight dropoff if the right
muffler outlet is closed. With the right side blocked off the sound level
is perfect inside and out, but I would like the option of being able to open
or close the right outlet from inside the car for DE or just general obnoxious-
ness.

I remember seeing some hot rod setups from the fifties with a setup like this...
maybe I'm trying to relive my childhood?

From my experiances with various drivers in various cars that when the sound level is increased that the driver will always report an improvement in power. I have also found that when you break out the stopwatch or put it on a dyno that they are wrong about half the time. I'm kind of inclined towards Randy Webb's point of view.

I realize that you aren't going to get any real power improvement out of the 3.2 with out spinning it faster, increasing the displacement or pressurizing the intake. I really just want to be able to use all of the power without calling attention to myself. On my average drive to work I will see the up side of 100 and I don't have any tickets in the last 6 years. I like it that way. :)

Of the common single outlet mufflers is there one that is close to the stock sound level?

Wayne

I would just search the Internet looking for "exhaust cutout" or "electrical exhaust cutout". years ago I talked to a guy who had done something like this on a big block Chevelle and he said the the cutouts tended to rattle when closed and he took them off. He also said that when he opened them up that it made every nut and bolt on the car rattle!

maybe I'm trying to relive my childhood?
Why relive it? It is easier to just skip that whole 'growing up' thing.

Wayne

Sorry I don't agree. Although the freer flowing exhaust the more power will be made, and the noise will be louder, If you could generate the opposite acoustical frequency as the exhaust, the power would be the same, but the sound would be less.

I believe the Stealth (figher/bomber) uses this type of technology.

The "anti-sweeping generalization task force" :D

originally posted by Quicksilver,
"maybe I'm trying to relive my childhood?
Why relive it? It is easier to just skip that whole 'growing up' thing."

Ogden Nash wrote....
" You are only young once but you can stay immature indefinitely "

Wayne, yes this flap device would have to be pretty well engineered
or the possibility of rattles or buzzing would be huge.

Mine makes noise, therefore I must be going faster :)

"the quieter whatever muffler you put on, the more it will be causing turbulence and impeding the flow of gases out of the engine."

- No. This is a widely misunderstood area. The real issue is the superposition of the pressure and rarefaction pulses and the degree to which they can "scavenge" gases from the compustion chamber -- and at what rpm. There is no real relation between noise and power. The flow will be highly turbulent no matter what. You will get little laminar flow out of any exhaust system.

You know I think there is a way to make the 3.2 faster and quieter, but I have yet to hear of anyone doing it. That is to install the super quiet 993 exhaust into a 3.2, but it will take some fabrication. The 3.2s exhaust is almost identical the the 964 exhaust, but the 993's exhaust was responsible for freeing up like 18 hp from the 964s 3.6. The way I would do it is modify the 993 headers to mate onto the 3.2's exhaust, which has been done many times. This would provide the large diameter desired plus provide heat. On the 993s there is a crossover which mates the two sides out to a pair of cats, and from each to a pair of mufflers. What I would do is fab a crossover out of the pair of headers, and into a pair of stock 993 mufflers, exiting to a pair of dual outs (AKA 'A Quite Boom's configuration) If anything this will have even less restriction than the factory 993 exhaust, because of the elimination of the cats, but have all the flow of headers larger than a set of SSIs. And everything will be in Porsche stainless.

On the other hand, the factory Bischoff single out muffler mated to a pair of SSIs aren't really all that loud. Just a decibel or two louder than the stock 3.2 exhaust, with a somewhat different tone. Also the annoying part of modified exhausts are not the volume of noise, but the drone which often occur in specific rpms and load ranges. If you can eliminate the drone, I think many 'loud' exhaust systems are actually quite bearable. As I have tried many mufflers mated to a pair of SSIs, I think only the factory single out is 'drone free'.

If you just want a little more power out of your stock 3.2 exhaust, without more noise, just install a euro-premuffler for about 6-8 hp and be done with it.

I'm not hugely worried about the power output. Frankly I find the cost to power ratio of most of the 3.2 mods to be way out of line. To get more power out of it I am planning on increasing the bore to 100mm, increasing the rev limit to 7500 (rod bolts and valve springs), 964 cams, .5 more compression, and twin plug w/direct ignition.

Walker (the muffler company) experimented with an electronic muffler over 10 years ago. They would flip a switch and poof, instant noise reduction. Never heard anything about it again.

So...
Is the Danske considered to be the quieter stainless muffler?

I'm really appriciating the quantity of feedback here.

Wayne

Before her rebuild, the Blue Bomber ran with a cat pipe and a GHL 1in/1out. The sound was delicious, but certainly much louder than stock. I sold that rig to a Carrera 3.2 owner who likes it v. much.

Now the 'Bomber is equipped with SSI's and a Dansk 2in/1out.
As I've just recently returned the car to the road, I can say the new combo is much quieter, but still sounds authoritative. The SSI people recommended using Dansk mufflers with their product.
I think it was a good call.

As far as an "electric muffler" that's what the current boxster "sport" muffler is. It is connected to the computer and when the sensors say you are getting on it they change some baffles in the muffler to provide more noise, and possibly more power, but definitely more noise.

Electronic Mufflers
 

Saw a special on tv a while back about an experimental muffler that used electronically generated sound waves whose sine wave is 180 degrees out of phase with the exhaust to reduce noise. The amount of exhaust noise could be controlled by turning the electronics on or off. Don't laugh it worked! Unfortunately, I can't remember who was doing the muffler. I think it was a company like Flowmaster or one of the other major brand muffler manufacturers. Anyway, something to search for on the 'net.

Good Luck!

Fred Cook
'80 911SC

Other than the stock Bischoff muffler, the Dansk if probably your next best bet. Their dual out sport muffler was one of the mufflers I tried. Louder than stock at idle, a bit of drone until 2200 rpm, at which point it disappears, is pretty quiet, and then has a nice mild roar above 5000 rpm. Nice power. A single out may be a bit quieter, and down probably a couple of hp.

I have the Dansk dual in-dual out on my 80 SC and really like it, Steve is correct, rumbles at idle, little resonance off idle, and means business at high rpms. Other than that my exhuast is stock, including cat, I tried a test pipe but with that muffler but I felt like I was in high school again. I'm looking to buy a fabspeed pre-muffler and give that a shot.....any experiences?

hipo i/o boats have 'silent choice' type systems. search marine websites and you might find something better that the jc whitney cutout.
being able shut down the second outlet would be the best of both worlds.

tryan- What is a hipo i/o boat? Thanks for the lead I'll try to search that later.
I agree that the cutout would be the best solution.

sorry high performance inboard / outboard. you can switch from thru the hub ( quiet ) to out the transom ( not quiet ). diameters might be larger than what you need but search for 'silent choice' or 'captains call' . nothing sounds sweeter than a 911 on the pipe, but it would be nice not to piss off the neighbors when you have to sneak home late at night.

This is the first hit I found on the Silent Choice.
http://www.marineparts.com/partspages/Corsa-Gil/gil3.htm

Can't see how it works from the picture but there must be a way to make something like it that is smaller.

Wayne

rex marine. eddies. gil marine. i'll look in powerboat.

another thing that might work is a diesel exhaust brake.

this picture shows the y. you just need the guts.

how about a heater flapper and a cable just to test it?

Wayne,

I think you should get SSIs and a dual-inlet /single-outlet Dansk sport muffler. $hort of that, get a fabspeed "euro pre-muffler" (nice stainless thing that replaces the cat), and a single-inlet/single-outlet Dansk sport muffler. Either way, as long as you get rid of the cat and use a Dansk sport muffler, you'll get a nice little performance improvement with minimal noise. You'll still hear your fan, put it that way. And I think you'll like that OE stamped design & look of the Dansk.

Cheers,

tryan, the openings out of my muffler are 3" round. Is that a common i/o exhaust size?

Randy Webb says.. "There is no real relation between noise and power. "

I guess that's why race cars are so quiet, eh. I never meant to say that power is a direct result of noise. That's ridiculous. What I mean is that, at a certain point, noise becomes a necessary byproduct of making more power. I doubt very seriously that the setup Bruce Anderson was able to make the most power with in his tests is anywhere close to the stock brand of quiet. In fact, I bet it's a good louder than my GHL system.