Std Zorst Q

[ratter]

  MICKAJ said:

So the smallest Area in this exhaust is 3" as 2X2.25 is larger than single 3".

So there is no point getting a custom 3" fab'd for this car, only 3.5"

Correct, but a high flow 3" muffler may still be better than the standard set up, although size wise it is down slightly

[SILK RSPEC]

2.25 inch pipework = 57.15mm dia. = 10260mm2 x 2pipes = 20521mm2 area

2.5 inch = 63.5mm dia. = 12667mm2 x 2 pipes = 25335mm2

3 inch = 76.2mm = 18241mm2 area

3.25 inch = 82.55mm dia. = 21408mm2 area

3.5 inch = 88.9mm dia. = 24828mm2 area

3.75 inch = 95.25mm dia. = 28502mm2 area

4 inch = 101.6mm dia. = 32429mm2 area

therefore you require a minimum of a 3.25 inch pipe to be greater than 2 x 2.25 inch pipes

and 3.75 inch pipework to be greater than 2 x 2.5 inch pipes

this is only if you want to keep to same velocity of the exhaust gases if they are the same temperature.

exhaust gases shrink when they cool so theoretically to keep the same velocity in the pipework the dump pipe should be larger than the twin exhaust pipes.

the back pressure increases and velocity when the pipework is smaller.

the smaller the pipework the faster the gas needs to run to get the same amount of flow through the exhaust. the friction loss through the pipework restricts the velocity to a maximum number eventually. The higher the velocity the noisier things get (well that is the case with water anyway)

Someone who is a mechanical engineer may be able to elaborate on this, the best way to test what would be the best bang for buck would be to install the exhaust and measure the back pressure in them or alternaively install an air flow meter on a free to air exhaust pipe say just after the dump to work out the required air flow that has to travel through the pipe and calculate the best size from there but this cost time and money.