How much difference in hp
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Joined: Nov 2005
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From: PA
How much difference in hp
I post this here because it is more a hp question than an exhaust question, well it is actually both, and quite frankly the exhaust section doesn't get to much responce...
i currently have a borla catback, pacesetter lt's, and pacesetter y...
i am getting a 4" mufflex with flowmaster muffler and i want to know how much hp i will gain and is it worth getting a double 3" merge to single 4" y-pipe or should i just save the money and run my single 3" y pipe?
i currently have a borla catback, pacesetter lt's, and pacesetter y...
i am getting a 4" mufflex with flowmaster muffler and i want to know how much hp i will gain and is it worth getting a double 3" merge to single 4" y-pipe or should i just save the money and run my single 3" y pipe?
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Joined: Nov 2005
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From: PA
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From: Houston, TX
heres a quote from the sticky in the exhaust section which might help you out a little bit on the pipe sizes
Hey guys I just got done reading a good article in the May 2005 issue of Popular Hot Rodding Magazine. The article was written by David Vizard 
who seems to be one of the most accredited and respected people in the automotive performance world. In the article he stated that CFM is a great way to help develop a zero loss exhaust system. For zero loss a exhaust must flow 2.2 CFM per horsepower(This means less than 1% of total power produced by the engine is lost due to back pressure.). From reading the article I think that a lot of people that see gains when going from a 2.5” exhaust system to a 3” dual system see them because the muffler on the 2.5” system didn’t flow enough for their application. David stated that per square inch of exhaust tubing there is 115 CFM of flow. So plugging some numbers into the good ole TI-89….. ((3.14 * radius^2)*115[*2 for a dual exhaust system])/2.2 = Max hp supported with zero loss
A 2.75” (stock) single system is good for a 310hp engine with zero loss…
A 3” Single system is good for a 370hp engine with zero loss…
A 3.5” Single system is good for a 503hp engine with zero loss…
A 4” Single system is good for a 657hp engine with zero loss…
A 2.25” dual system is good for a 457hp engine with zero loss…
A 2.5” dual system is good for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…
Now these numbers are assuming that everything else is set up perfectly. The muffler must flow as much as the open pipe or more to get zero loss at the listed hp levels. He also states that using a muffler with a larger inlet/outlet diameter than your exhaust pipe is a great way to get more out of a smaller diameter system since the muffler flow will be able to match the straight pipe flow. Now there are many other things to consider when designing an exhaust system but I figured this would give a great foundation to build on.
Just a side note that he stated that I thought was neat... “Just as fish don’t feel the weight of water, we don’t readily appreciate the weight of air. Just to set the record straight, a cube of air 100 feet square will weigh 38 tons!”
Hopefully I’ll get some more understanding of flow in a closed space in my fluid dynamics class next semester.
who seems to be one of the most accredited and respected people in the automotive performance world. In the article he stated that CFM is a great way to help develop a zero loss exhaust system. For zero loss a exhaust must flow 2.2 CFM per horsepower(This means less than 1% of total power produced by the engine is lost due to back pressure.). From reading the article I think that a lot of people that see gains when going from a 2.5” exhaust system to a 3” dual system see them because the muffler on the 2.5” system didn’t flow enough for their application. David stated that per square inch of exhaust tubing there is 115 CFM of flow. So plugging some numbers into the good ole TI-89….. ((3.14 * radius^2)*115[*2 for a dual exhaust system])/2.2 = Max hp supported with zero lossA 2.75” (stock) single system is good for a 310hp engine with zero loss…
A 3” Single system is good for a 370hp engine with zero loss…
A 3.5” Single system is good for a 503hp engine with zero loss…
A 4” Single system is good for a 657hp engine with zero loss…
A 2.25” dual system is good for a 457hp engine with zero loss…
A 2.5” dual system is good for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…
Now these numbers are assuming that everything else is set up perfectly. The muffler must flow as much as the open pipe or more to get zero loss at the listed hp levels. He also states that using a muffler with a larger inlet/outlet diameter than your exhaust pipe is a great way to get more out of a smaller diameter system since the muffler flow will be able to match the straight pipe flow. Now there are many other things to consider when designing an exhaust system but I figured this would give a great foundation to build on.
Just a side note that he stated that I thought was neat... “Just as fish don’t feel the weight of water, we don’t readily appreciate the weight of air. Just to set the record straight, a cube of air 100 feet square will weigh 38 tons!”
Hopefully I’ll get some more understanding of flow in a closed space in my fluid dynamics class next semester.
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I post this here because it is more a hp question than an exhaust question, well it is actually both, and quite frankly the exhaust section doesn't get to much responce...
i currently have a borla catback, pacesetter lt's, and pacesetter y...
i am getting a 4" mufflex with flowmaster muffler and i want to know how much hp i will gain and is it worth getting a double 3" merge to single 4" y-pipe or should i just save the money and run my single 3" y pipe?
i currently have a borla catback, pacesetter lt's, and pacesetter y...
i am getting a 4" mufflex with flowmaster muffler and i want to know how much hp i will gain and is it worth getting a double 3" merge to single 4" y-pipe or should i just save the money and run my single 3" y pipe?
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Joined: Dec 2004
Posts: 454
From: So. Cal
Good Sticky. I can give you my dyno results but not exactly apples to apples. I was running a 3" SLP catback on my car. It is a L98 motor with dual cats. I put down 304 rwhp and 334rwtq.
I then installed the 3.5" Mufflex cat back with a 3.5 inch Magnaflow muffler. Also a Flowmaster 2.5" to 3.5" wye. During this time I also installed a Meizere electric water pump. I went back to the dyno and put down 330 rwhp and 370rwtq. Can't tell you what the electric water pump was worth or the Mufflex by themselves. Only the two together.
I then installed the 3.5" Mufflex cat back with a 3.5 inch Magnaflow muffler. Also a Flowmaster 2.5" to 3.5" wye. During this time I also installed a Meizere electric water pump. I went back to the dyno and put down 330 rwhp and 370rwtq. Can't tell you what the electric water pump was worth or the Mufflex by themselves. Only the two together.
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Joined: Nov 2005
Posts: 646
From: PA
Good Sticky. I can give you my dyno results but not exactly apples to apples. I was running a 3" SLP catback on my car. It is a L98 motor with dual cats. I put down 304 rwhp and 334rwtq.
I then installed the 3.5" Mufflex cat back with a 3.5 inch Magnaflow muffler. Also a Flowmaster 2.5" to 3.5" wye. During this time I also installed a Meizere electric water pump. I went back to the dyno and put down 330 rwhp and 370rwtq. Can't tell you what the electric water pump was worth or the Mufflex by themselves. Only the two together.
I then installed the 3.5" Mufflex cat back with a 3.5 inch Magnaflow muffler. Also a Flowmaster 2.5" to 3.5" wye. During this time I also installed a Meizere electric water pump. I went back to the dyno and put down 330 rwhp and 370rwtq. Can't tell you what the electric water pump was worth or the Mufflex by themselves. Only the two together.
i def. think it is worth doing the 4"... mainly because i plan on building the engine down the road and it can handle 675 hp... not sure what it handles with the cats, but i have heard of people gaining ponies with cats...
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Joined: Aug 2005
Posts: 434
From: Utica, NY and Jacksonville, FL
because IMHO flowmasters are some of the worst flowing exhausts for our cars... my loudmouth comes in on tuesday and i plan on changing it out ASAP... flowmaster sounds ok but thats about it.. i personally dont like it.. but hey a bunch of people run em still so i guess that cant be that bad...
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