Gregg, my point is in response to this comment.
We know that mufflers will not make goobs of HP.
But none the less you can "gain power from mufflers"

My test was with just the mufflers all located in the same spot on the exhaust pipe.
This way every dyno pull was equal except the muffler.
On the small four cylinder engine the delta was almost 15 rwhp.
The Flowmaster pulled highest HP with almost the highest Db level.
A straight pipe was least, and the best overall a "Turbo-Muff" So there is a gain from nothing to something.

Yes we're splitting hairs and an "airfoil" might have the same results.

 

Details of this test?

The fact that you dyno tested mufflers is so awesome, compared to what most others on this site do (the "peel-o-meter" for example), I really don't want to question it. But something is not right here. A muffler can not "make" power. This means compared to a straight pipe, a muffler (a pipe with a large cross section and baffles, OR a pipe with holes in it), can not make the exhaust flow increase...which is what a muffler would generally have to do to "make power" over a straight pipe in the same place.

Again...it's totally cool that you applied objectivity here...but I seek an explanation as the results you got defy reason. If it were my test, I'd have to look deeper. Maybe the details of the vehicle would provide an answer? Did the A/F ratio change pull to pull? IDK. This certainly caught my interest!

 

bingo!!!

 

One thing that plays in, are you talking L98 or LT1 exhaust? The LT1 mufflers are already a low restriction muffler. Dont know about the VW cited earlier. I have played with stock exhaust vs magnaflow mufflers, and at the track can tell no difference, much less by the seat of the pants.
IMO and this is very subjective, A set of LT headers, tied back into the stock LT1 exhaust, is the best bang for your buck. Its louder and deeper then manifolds and cats.
FWIW Even if it is worth 6-11 hp. $1,000.00+ is not the way I want to spend my money.

 

What I see is no Mufflers do not make HP, But they do restrict HP/flow so a better flowing muffler will gain you HP that you lose due to a flow restrictions. So I guess you could say its found HP.

 

Thats how I would correctly state it.

I'd call it a gain in HP for newbs asking about mufflers, but its semantics.

 

Mustang 5.0 Magazine (Rick Anderson ) did a really good chassis dyno session back in Dec 2002 with a low 11 second second car and about 15 or 20 different mufflers....

They documented peak power, average power, peak TQ, average TQ, DB at idle and DB at WOT....

I'd link you to it but the site is blocked from my work computer.
Will

 

This it?

http://www.mustang50magazine.com/tec...mparison_test/

Car is a black '90 5.0.

THANK GOD that you can still look at the 'Vette forum at work!

 

That's the one if I remember correctly.

Oddly enough most forums are not blocked but for whatever reason our internet filter thinks the 5.0 mag site is all bikinis and neked womens...
Will

 

The mustang test was interesting.

Just looking at the numbers a little, the Bassani mufflers were well below the rest. With them excluded the rest of them (and open exhaust) all averaged within about 8.8 hp over the whole rpm range.

My $0.02---There might be some power to be gained over a bad exhaust, but most of them are close enough that any gains are minimal. It still looks like we should buy the ones we want for the sound or looks. If you are racing and need the last few hp then it may be worth looking further.

 

That would be Yellowbullet

 

And YB is totally accessible at work!

Of course I know better than to click on some threads.
Will

 

Cool! Now we're getting somewhere. Let's see a muffler/airfoil dyno test!

FWIW...Seems like I remember Vizzard saying chambered mufflers flowed a bit better than those necking to larger/smaller cases (like glass-packs/cylindrical canisters/etc...

Another Vizzard approach is to choose a larger necked muffer than your piping and adapt. (Same for converters.)

 

Just changing the Mufflers wont give you a better exhaust. The L98 exhaust is very restricted. On a budget I would say go with a catless y a free flowing cat and what ever muffler tickles your fancy. If you really want better flowing exhaust go with headers and a dual exhaust. I fit stock LT1 exhaust onto my 91 it may be possible to fit them to your car as well.


http://forums.corvetteforum.com/c4-t...te-videos.html

 

After owning several cars with several different exhaust combinations, I've come to the following "budget" minded results for the c4;

The 92' - 96' exhaust system is pretty decent. If you don't mind more noise, and want to gain a little more power, replace the mid-muffler FIRST. The majority of the restriction is recognized in the mid-muffler, and eliminating it entirely, or replacing it with an aftermarket unit should yield a reasonable improvement (over stock). The least-expensive rear-muffler option would be to get a pair of muffler-eliminators. Several owners have mentioned the eliminators sound great and yield an improvement in power. I would even take it a step further and replace the stock H-pipe with an X-pipe (proven to marginally increase HP over an H-pipe)

I'm certain the above modifications would get you about the same amount of horsepower as a complete aftermarket setup (which would be pretty expensive).

The Corsa has been known for years to provide a visually appealing end-result, with minimal drone (interior noise). If Corsa offered a true 3" system, I would be all about it. "But" the system is actually 2.5" (stock is 2.75"), not worth the heavy price in my opinion. (the current knock-off version from OBX offers the same visual appeal for the fraction of the price).

The Magnaflow (which I've run on 2 of the 3 c4's I've owned) is a true 3" stainless system, but the muffler-body in relation to the muffler is total straight (unlike the tastefully tucked look of the Corsa system). This is definitely the least expensive, true 3", true dual with x-pipe system available.

My 96' had some B&B's on it, and it had an outrageous amount of drone. The road trip I took from LA to PHX was terrible, I had a loss of hearing for a solid hour after the trip. I hated it, I took it off and sold it. B&B is also over-priced.

My conclusion is, "IF" I did it all over again, I'd go with the stock system and install electric cut-outs to then have the best of both worlds. You can also regulate the amount of flow out the cut-outs as well (in electric versions).

If costs wasn't a factor, I'd go with Corsa's (or the OBX knock-off) AND cut outs. Enjoy the looks, enjoy the civil cruising noise, and take complete advantage of the power potential with cut-outs.

 

Interesting. I have been considering what to do for exhaust on my '95.

I read in another thread that someone replaced the center resonator with and X-pipe with good results. They claimed 1-2 mpg increase along with a better sound. That mpg increase tends to support that the resonator may be the restriction in the system. I had never been thinking of this mod before recently, but I would like to learn more or hear from others that have tried it.

I have had muffler eliminators on an otherwise stock '94 and liked them, but that is about my limit for how loud.

If I mod the stock exhaust with either the X-pipe or the eliminators, the sound increases. If both are done, is it way too loud or would I be better off doing one or the other?

 

I respectfully disagree. A proper muffler, with a significant interior volume compared to the exhaust pipe feeding it, appears as a low pressure "dump" for the exhaust flow. The abrupt area/volume increase of the muffler causes a reflected low pressure wave to go back to the header and the exhaust valve. If the exhaust valve is still open when the negative wave gets there the effect is an extra suction/scavenging effect to empty out the cylinder.
A large volume muffler, if placed in the correct location, acts like an exhaust pulse termination box.

Disclaimer: I wasn't smart enough to figure this out on my own, but Vizard is. I took his advice and modeled my exhaust system after his recommendations. My exhaust system is quiet, has minimal drone, and minimal backpressure. My pressure gauge setup to monitor pressures/pressure drops in the car:

 

Tom is right. He was merely clarifying you can't "gain" power with the addition of a muffler over straight pipe (or header dumps).

Vizzard had pointed out the effects of cams and scavenging and the ability to increase VE above 100% with proper exhaust design. It's not that a muffler adds power...as Tom indicates. You can create the affect Vizzard talks about with the use of a pulse termination box...which doesn't have to be a muffer. I understood the box to be a method for extending exhaust pipe BEYOND the "ideal termination length" that would create best scavenging/horsepower. You could, just as easily/effectively, terminate your exhaust at the ideal length. It would end up under the car and you'd smell the fumes. Vizzard also addresses the use of mufflers as many racing venues require "something" anyway.

I'm with Tom. Mufflers will never "create" horsepower. Properly placed and designed, they will minimize loss.

 

My understanding is similar to what 427 Tom Greg and Reckless have said. a significant change in collector configuration will signal the end of the collector. A resonator, T, Y, or muffler will represent the end of the collector. A good pipe program will get you in the ball park about how long works for what application. Different shapes will initiate the wave reflection at a different place in the device. For instance a Flow master reflects at the first baffle, perforated straight through reflects at the end of the can. There is also a point where the low pressure behind a exhaust pulse is no longer defined well enough to help scavenge. Its my understanding that wave tuning works different in the collector than the primaries. I read a great paper back in the early 80s iirc it was titled Motor sport pulse dynamics written by a Penskie engineer. First time I heard anything about the shock waves bouncing back and fourth in the intake and exhaust. Cool read.

btw I rember reading somewhere about Saint David Vizard developing and testing a exhaust for a high powered C4 but I have no idea where to find it.

 

If you currently run muffler eliminators (in the back), I would suggest a MUFFLED x-pipe. here is an example from Magnaflow;

http://www.magnaflow.com/02product/s...=main&id=11391

it will provide an internal x-pipe and incorporate a muffler. This would be a nice replacement for your existing center resonator! While retaining your rear-position muffler eliminators. It will be "louder", by how much? I have no idea.

Otherwise, you can run bullet mufflers right behind the long-tube headers (in the catalytic converter position), or JUST BEHIND the existing cats, and run a traditional X pipe.