Tuned Exhaust Pipe Length Calculation For Single/Twins/Fours.
Tuned exhaust length start from valve head,this know as "Down pipe"
The induction length start from valve head to end of the belmouth, center line of the port or
as You know it the "Stacks"
For Single engine use:# 1,2,8
For Twin engine use:# 1,2,6,7,8
For Fours engine use:# 2,3,4,5,6,7,8
Example:
A Single cylinder:
Aermacchi 349cc
Exhaust Open = 91Deg
Rpm = 8600
CC = 349
1,Tuned Length 24 Inch
2,Primary inside diameter 1.510 inch
8,Tailpipe Length: 23.492 inch
Twin Cylinder:
Two in to one:
Ducati 1017cc (one Pot 508cc)
Exhaust open = 95 Deg
Rpm = 7500
CC = 508
1,Tuned Length 28 Inch
2,Primary inside diameter 1.700 inch
6,Collectorbox Length 3.949
7,Tailpipe inside diameter 2.290
8,Tailpipe Length 27.051 inch
Notes:
A reduction in primary pipe Diameter of 1/8 of an inch
will move the torque peak down by 650-800 RPM.
Conversely an increase in diameter of the header will raise
the engine speed at which max torque occurs,by approx the same RPM,for each
1/8 of increase.
Adding length to the primary pipe will increase low speed and mid-range power,
with corresponding reduction in power at max RPM.
Shorter primaries give an increase in high speed power,
at the expense of reduction in the midrange.
However,there will be little change in peak torque or
the engine speed at which it occurs.