Induction Info - Provider by RinB

[drunkmunkey6969]

Copy of a technical post made in another section, thought it should be added here too for future ref. See original post if you wish to comment. Cheers Smiffy. Dan.

Below is the basics for working out the peak torque engine speed
which is deduced from the wave period & velocity of gas in a tube

Peak Torque (RPM) is found using the formula:
RPM=0.667 x a x In Deg/((4xV/Pi x d²)+L)

Where:
In Deg =Inlet Port Timing º
a =1100 Speed of sound
d =Diameter of Inlet "
L =Length of inlet track "
V =Swept Volume "

From the formula above the following table can be made please note every thing is in Inches.

V----d-------L-----deg-------RPM
7.5----0.9-----6-----120--------5000
7.5----0.9-----6-----160--------6600
7.5----0.9-----10----120--------4100
7.5----0.9-----10----160--------5400
7.5----1.1-----6-----120--------6350
7.5----1.1-----6-----160--------8500
7.5----1.1-----10----120--------4900
7.5----1.1-----10----160--------6600

So from above the engine speed that max torque occurs needs a large
carb, short inlet track & a long inlet timing.


Now lets put this into lamie terms
200cc Inlet timing 160deg

using 22mm standard dely track length 6.4" RPM =4400
using 25mm dely big bore track length 8.7" RPM=4800
using 28mm dely big bore track length 8.7" RPM=5500
using 30mm dely big bore track length 8.7" RPM=6000
using 30mm dely big bore track length 7" RPM=6500


Now you see why I dont fit 25mm might as well stay with std 22mm

Also why I use manifold with 7" track

Hope this gives an insight into the induction system.

The next step to this is the engine speed at which Max power occurs
Which again track Length and Diameter has an effect but Ill do this later

Smiffy