Do glasspacks hurt fuel economy?

[OFF-RD]

Hey guys, I'm going to put a different muffler on my new truck. Can't decide what to get. The Flowmaster and Magnaflow muffs are $60-$100 and that's nuts. I noticed that you can buy a glasspack for $25. Isn't a magnaflow muffler just a perforated tube with fiberglass packing around it? If so, then what's the difference between a Magnaflow and a "glasspack"? Will a glasspack hurt my fuel economy or power? I've never used a "glasspack" before. Any advice would be appreciated.

[carneyman]

Any kind of muffler you put on that makes your truck louder will hurt your fuel economy. You are always romping on the gas to hear it! But I've had 2 trucks with glasspacks and have never noticed any change either way with the mileage.

[snoman]

Hey guys, I'm going to put a different muffler on my new truck.  Can't decide what to get.  The Flowmaster and Magnaflow muffs are $60-$100 and that's nuts.  I noticed that you can buy a glasspack for $25.  Isn't a magnaflow muffler just a perforated tube with fiberglass packing around it?  If so, then what's the difference between a Magnaflow and a "glasspack"?  Will a glasspack hurt my fuel economy or power?  I've never used a "glasspack" before.  Any advice would be appreciated.

 

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You might gain a fraction of MPG on highway (maybe) but you will take a hit on MPG and responce in town with duals and with straight through mufflers being the worse combo in this regard. On the difference, the Magna Flow has a different resontance chamber size the is "packed" and it effects the resulting sound.

[OFF-RD]

Yeah I've been averaging around 16 mpg with this truck...it's blowing my mind and I don't want to loose that great mileage. But I would like to "open it up" just a little bit and get a nice performance sound out of it. Are "glass packs" really loud compared to say, a Flowmaster?

[snoman]

Yeah I've been averaging around 16 mpg with this truck...it's blowing my mind and I don't want to loose that great mileage.  But I would like to "open it up" just a little bit and get a nice performance sound out of it.  Are "glass packs" really loud compared to say, a Flowmaster?

 

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Yes a lot louder. Modern engine are well tunned for intake to exhuast and little is gained in the mPG department tinkerig with them (usually it is a loss around town) the reason for this is that if the exhause gas is allowed to blow down to quickly at lower RPM less energy is captured from the expanding gasses. Some backpressure helps pervent this. Also ifm back pressure is too low, some fuel is lost to savanging during overlap at lower RPMs where most town driving is done.

[OFF-RD]

OK thanks. I will just go with a Raptor performance muffler then. They supposedly are made by Holley and are good quality for $25. I don't want a REALLY loud exhaust..my wife wouldn't like that. I just want to hear this beautiful all-aluminum V8 talk back to me. Thanks for the replies.