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aerohead · 04-25-2009, 02:04 PM

The I.D. of your throttle should closely mirror that of your exhaust.Your system should already have mandrel bends at all turns.A little bit of crimping won't significantly restrict the flow,and as mentioned by others,some back-pressure is ESSENTIAL to overall performance.Check me on this,but for a 4-stroke engine,if you'll divide your RPM by 2,then multiply that value times the engines displacement,this will give you your flow volume.If you divide the volume by the area of your exhaust pipe,this would give you the gas velocity inside.ASHRAE(American Society of Heating and Refrigeration Engineers) has some tables,as BicycleBob has mentioned that will give recommendations for max velocities inside pipes/ducts based on Reynolds Number.You would really have to continuously operate your car at wide-open -throttle,everywhere you went to benefit from an idealized exhaust system.Pressure taps and manometer readings along the entire system would prove it to you.

04-25-2009, 02:04 PM	#6 (permalink)
aerohead Master EcoModder Join Date: Jan 2008 Location: Sanger,Texas,U.S.A. Posts: 15,895 Thanks: 23,972 Thanked 7,223 Times in 4,650 Posts	exhaust The I.D. of your throttle should closely mirror that of your exhaust.Your system should already have mandrel bends at all turns.A little bit of crimping won't significantly restrict the flow,and as mentioned by others,some back-pressure is ESSENTIAL to overall performance.Check me on this,but for a 4-stroke engine,if you'll divide your RPM by 2,then multiply that value times the engines displacement,this will give you your flow volume.If you divide the volume by the area of your exhaust pipe,this would give you the gas velocity inside.ASHRAE(American Society of Heating and Refrigeration Engineers) has some tables,as BicycleBob has mentioned that will give recommendations for max velocities inside pipes/ducts based on Reynolds Number.You would really have to continuously operate your car at wide-open -throttle,everywhere you went to benefit from an idealized exhaust system.Pressure taps and manometer readings along the entire system would prove it to you.