What is in that muffler looking thing just behind the cat? I'm trying to decide if I should spring for a full cat back . I'm thinking of taking that piece out and putting a 2.5 in piece of stainless pipe in its place. Then putting in a Borla muffler straight thru design . Full cat back $559 for B&B on a group purchase. Pipe and muffler $200. Is there really a $350 performance benifit to the catback . The muffler and that other piece are the two major restrictions and they would be gone.

 

That first muffler looking thing is a first stage muffler, some call it the resonator..The beer barrel in the back is a spark arrestor and final stage muffler...Together, there is significant back pressure and restriction to exhaust flow..The cat back systems are tuned for optimum exhaust flow and back pressure...The disadvantage with what you have in mind is, you have to cut your stock system...Leaving you with no retreat in chance that the Borla doesn't meet your likes...You won't be able to put the stock back on if you have to..With a full cat back..You can take your stock system out in one piece and store it for later or return the car to original for resale...For $372.00 you can get a Gibson
And you don't even have to be part of group, and free shipping to boot..

 

Dennis, I don't know if you have measured the exhaust backpressure at various points in the exhaust system, but if not, I don't think we can automatically assume there is significant backpressure due to the factory muffers/resonators. GM has been getting pretty good at designing at exhaust systems lately. In fact, there is virtually no power to be gained by changing the stock mufflers on the new Corvette, so about the only thing you can get is more sound by changing mufflers on those.

Michael

 

Mike, you might be right..I don't have means of comparing backpressures, and yes the sound definitely changed and of course we got rid of a two muffler system, to a one muffler system..that in it's self should mean some free'r flowing exhaust..The makers of these Cat-back systems, all claim to have tuned their system to optimize the exhaust flow for maxium power gain..Are they ALL BSing us? I don't know..I can't imagine them ALL claiming that, unless there was some truth to it, or performance facts to support their claims of HP increase..Anyways, at this point I'm pretty satisfied with the results of the gains in my cat-back that I believe that I've noticed...Besides it looks good too.

BTW..I think a Vette is in a league all it's own and wouldn't be fair to compare a $60,000 car to a $30,000 H3, as the Vette is probably tuned to optimum performance from the factory in ALL respects. So in that case you are probably 100% correct.

 

Being intimately familiar with the aftermarket industry (and I'll leave it at that), most aftermarket performance claims are complete BS. I wouldn't believe any published number, without independent verification. Here are a few of their tricks:

1) Measure horsepower so far beyond the horsepower peak RPM, you would have shifted long ago for maximum vehicle performance.

2) Put aftermarket exhaust on a modified engine, which needs the extra flow to begin with.

3) Run horsepower test, but also change other components and retune engine at the same time, so you can't really tell if the exhaust system helped or not.

4) Make exhaust system louder, so the buyer "thinks" there is an improvement in performance.

Independent, unbiased testing is very hard to come by, and the aftermarket knows this. Caveat Emptor.

By the way, increasing the number of mufflers/resonators can actually improve performance. Lower backpressure components can be used for the same amount of silencing. Resonators can be placed where they have the most effectiveness at reducing resonance, while adding much less backpressure than a more restrictive muffer accomplishing the same thing. Almost all aftermarket systems are very poor at resonance control. In general, the larger the muffler, the lower the restriction (general rule), because internal piping and baffling can be made larger.

Having said all this, are there any good aftermarket systems? A few, but it takes a lot of research to find them. Also after a certain point, price doesn't seem to be much of an indicator of quality.

Happy 4 wheeling,

Michael