That seems to be the popular opinion of this board.

Glasspacks are a straight though design. Do the louvers (i guess that's what they are called) cause turbulance restricting flow?

Most other high performance systems have to go through a non-straight path which will definately cause resistance.

Enlighten Me!!

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1986 Black/Gold "GT" Z28
Original Owner, 202K+ near trouble free miles.
Mostly Stock, becoming less stock each day.

1995 Dark Red Metallic Corvette Coupe 36K miles

 

You hit the nail on the head. Those hundred of louvers create considerable turbulence with their sharp edges. Further, many glasspacks point the louver openings into the flow of the exhaust. Finally, some(but not all) glasspacks "neck-down" at the entrance, in an attempt to keep the sound level reasonable.

The only real advantage to glasspacks is their compact size.

Interestingly enough, Borla and SLP's "Power-Flo" mufflers also use louvers internally. However, as these mufflers have dual outlets(in effect "neck-up") some of the restriction caused by the louvers is removed. And because they use more durable material for sound deadening(Borla uses steel wool, SLP uses a ceramic blanket), they will retain their tone and last longer than glasspacks.

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He who hesitates,... is lost!

 

About everything he said was true. One way to get around having a restrictive glasspack is to just get a size bigger than you would normally use. For example, if you were going to use dual 2 1/4" exhaust, get 2 1/2" glasspacks if you don't want near as much restriction. That way they will flow great. And sound great too!

 

Guy thats just not true. There are lousy glasspacks (Like cherry bombs) that don;t flow for anything, just like there are lousy standard mufflers. There are also Great ones, like Thrush Magnums or dynomax bullit, that outflow any other muffler out there, Including Flowmaster Edelcrock and Hooker. I run a glass pack and I'd never go pack, it blows away the flowmaster I used it to replace.

 

Jester's right. Some glasspacks flow really good. The Thrush Glasspacks do flow great. That's what I have on my car. You can just look on the inside of it and tell that it will flow good.