GT40s.com - View Single Post

Paul Bearman · 12-15-03, 04:42 PM

The formula for primary pipe length of 4 into 2 ito 1 exhaust header is:

P = 850 X ED divided by rpm -3

Where rpm is the engine speed the exhaust is being tuned to & ED is 180 deg plus the number of deg the exhaust valve opens before BDC.

Does this stand true when compared to a crossover system as used on a GT40?
If so, then the ideal pipe length is around 27", but this conflicts with the common accepted length of 36". Can anyone shed some light on this?

12-15-03, 04:42 PM	#1 (permalink)
Paul Bearman Paul Bearman 4 Tenths Join Date: Oct 2001 Location: UK, Kent GT40: Ex GTD40 owner, Posts: 441 Rep Power: 11	Primary pipe length formula The formula for primary pipe length of 4 into 2 ito 1 exhaust header is: P = 850 X ED divided by rpm -3 Where rpm is the engine speed the exhaust is being tuned to & ED is 180 deg plus the number of deg the exhaust valve opens before BDC. Does this stand true when compared to a crossover system as used on a GT40? If so, then the ideal pipe length is around 27", but this conflicts with the common accepted length of 36". Can anyone shed some light on this?