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Two Stroke Exhaust, Expansion Chamber/Diffuser Design
Note: All input and output on this screen is in Metric units only.
This will let you calculate the dimensions of a single, one, two, or three stage expansion chamber / diffuser exhaust systems
for your two stroke engine. Based on which command is selected unused output cells will be grayed out when the results
are displayed.
Some of the main parameters in exhaust design are exhaust duration, the effective exhaust port diameter (calculated from
exhaust width and height as a basic rectangle), engine RPM, and the speed of sound, and the variable that causes changes
in the speed of sound which is Exhaust Gas Temperature. The user can enter each of these or check either or both check
boxes and have the program calculate these values for you.
The LT value is calculated from the piston face.
These constants will let you customize the calculations. For these you have 3 choices.
1) Use the default values in the program.
2) Enter the values you want to use.
3) Have the program calculate the values for you. This only works for exhaust gas temperature, Horn Coefficient, K0, K1
and K2. To do this the program needs to calculate BMEP using cylinder capacity, power in KW, and RPM’s.
Constant Value based on Engine Type:
Exhaust Temp
K0
K1
K2
Road Bike
375
0.70 1.125
2.0
Enduro
500
0.7
1.125
2.25
Motocross
600
0.65 1.0875
2.75
Grand Prix Racer
650
0.6
1.05
3.25
Lower K1 and K2 numbers will give you a boarder power band and higher numbers for a higher / very narrow RPM range.
The Horn Coefficient works with smaller values for narrow power band and larger values are for a boarder power band.
Angle A1 normally is between 7 to 10 degrees, while angle A2 is normally set to twice A1 or between 14 to 20 degrees.
Single Stage Diffuser is based on the book "2-Stroke Tuner's Handbook" by Gordon Jennings.
Two and Three Stage Diffusers are based on the book "Design and Simulation of Two Stroke Engines" by Dr. Gordon P. Blair.
CARFOR Performance Software by Stan Weiss / World Wide Enterprises - 121