Exhaust Flow E.g. Would 2 X 3 Inch Flow The Same As 1 X 6 Inch

[stomper]

As the title says, having this debate currently and would like to open it up to those that may know.??

Barring any loss of efficecny for the seperation/merge, would a theoretical twin 3 inch system flow the same as a single 6 inch; twin 2inch same as single 4 inch etc.

Cheers

[Strik3r]

No

Simple math. Area of a circle (pipe) = pi * r^2

since pi is constant, we can ignore it and just look at the r^2.

2 * 2 ^ 2 (8) is LESS than 1 * 4 ^ 2 (16)

2 * 3 ^ 2 (18) is LESS than 1 * 6 ^ 2 (36)

you can multiply those numbers by pi to get actual surface area measurements. 1 4" pipe flows JUST under what 2 3" pipes will do.

[R31Nismoid]

indeed, not quite that simple as stated.

remember the further you go out/larger the circle, the more area you get with each increase in radius.

hence you only tend to see a twin system on skyline for ride height/clearance issues and sometimes noisenot really for flow.

although that said the 400rwkw r32gtst down here has a very nice and quiet 4" tucked up into the body.

[75coupe]

isnt there also a temperature factor to take into account as hotter air moves faster so if you were to wrap the exhaust somewhat you get faster exit of exhaust gases or does that get cancellled out due to air density changes???

[Adriano]

And then there is the friction of the boundary layer of gas around the perimeter of the pipe. At a guess i would say a 4in would flow more than 2x3inch.

[T04GTR]

you have twice as much boundary layer with 2 pipes.. so i would say with confidance that a 4" pipe will flow better. and if its going from a single to 2, then you have to take into account the transition.

[NXTIME]

What would you reccommend for my car, Dave?

[TiTAN]

single 5" pipe out the front guard.

[Adriano]

Nah, too long, high mount rigoli style with a 45 deg bend so you dont melt the windscreen