Mac Headers w/cats please review my data
11-29-2004, 12:28 PM
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Mac Headers w/cats please review my data Just spoke to the tech guy at MAC and he told me that the cats on there catted y pipe are made by CATCO and flow 360 CFM each. If I am reading the article from Install University correctly if my almost stock ls1 is putting 350HP at the fly wheel and I need a flow of 2.2 cmf per 1 Hp 2.2x350=770 CFM. If in fact these cats truly flow 360 CFM each 2 would flow a total of 720 CFM. I should not loose any Hp to speak of until I really start modding the engine. I really like the MAC headers but I have read so many bad things about their cats I am afraid to get them but if this info is correct they may not be as bad as everyone suspects. Dose this make sense or am I completely screwed up
Inlet Diameter (in.) Outlet Diameter (in.) CFM @ 20.4” H2O CFM @ 28” H2O
Passenger Side Catalytic Converter 2.5 2.5 299.5 350.9
Driver's Side Catalytic Converter 2.5 2.5 268.3 314.4
TTS Bullet Catalytic Converter 2.5 2.5 277.1 324.6
Car sound Catalytic Converter 2.5 2.5 372.7 436.7
FLP Catalytic Converter 2.5 2.5 376.0 440.5
Each pair of catalytic converters restrict about eight (8) rear wheel horsepower on stock LS1’s. David Vizard’s research shows that 2.2 cfm of flow at 20.4” of H2O will support 1 horsepower. 2.2 cfm is the optimum flow through the exhaust system and reflects open pipe flow. Removing the stock catalytic converters on the LS1 usually results in a gain of 8 rear wheel horsepower. Assuming that the average LS1 puts 300 horse power to the ground, that is a 2.67% increase in power.
http://www.installuniversity.com/ins...sity/index.htm
Inlet Diameter (in.) Outlet Diameter (in.) CFM @ 20.4” H2O CFM @ 28” H2O
Passenger Side Catalytic Converter 2.5 2.5 299.5 350.9
Driver's Side Catalytic Converter 2.5 2.5 268.3 314.4
TTS Bullet Catalytic Converter 2.5 2.5 277.1 324.6
Car sound Catalytic Converter 2.5 2.5 372.7 436.7
FLP Catalytic Converter 2.5 2.5 376.0 440.5
Each pair of catalytic converters restrict about eight (8) rear wheel horsepower on stock LS1’s. David Vizard’s research shows that 2.2 cfm of flow at 20.4” of H2O will support 1 horsepower. 2.2 cfm is the optimum flow through the exhaust system and reflects open pipe flow. Removing the stock catalytic converters on the LS1 usually results in a gain of 8 rear wheel horsepower. Assuming that the average LS1 puts 300 horse power to the ground, that is a 2.67% increase in power.
http://www.installuniversity.com/ins...sity/index.htm
11-29-2004, 01:47 PM
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Definitely do NOT run the Mac highflow cats. Correct, those things suck and don't flow worth a $hit once you start modifying your car. Rather, have a Carsound, Random Technology, or Magnaflow highflow cat welded in place of the Mac cat if you decide to go with these headers... 
Flow problems then solved and you still have a great set of headers that are very comparable to the top of the line longtube set-ups for much less $$$... 
Mike
Flow problems then solved and you still have a great set of headers that are very comparable to the top of the line longtube set-ups for much less $$$... Mike
