Design and Simulation of Two Stroke Engines

Rearranging for the pipe length, Lj, which is in mm units:
83.3an8(irv
T _ U C P
J_,rp
rpm
Chapter 6 • Empirical Assistance for the Designer
(6.2.4)
The remainder of the empiricism presented is straightforward, following the nomenclature
of Fig. 5.7. The end of the diffuser is positioned as in Fig. 6.17, about two-thirds of the
distance between the exhaust port and the tail-pipe entry. The pipe segment lengths are proportioned
as follows:
first pipe and diffuser:
Li=0.1LT L2 = 0.275LT L3 = 0.183LT L4 = 0.092LT (6.2.5)
mid-section, rear cone and tail-pipe:
L5 = 0.11LT L6 = 0.24LT L7 = L6 (6.2.6)
For the diameters the following advice is offered. First, for the initial pipe diameter, di:
di =lqdo (6.2.7)
The value for the constant, lq, ranges from 1.125 for broadly tuned, enduro type engines
to 1.05 for road-racing engines of the highest specific power output.
d4 = k2do (6.2.8)
The value for the constant, k2, ranges from 2.125 for broadly tuned, enduro type engines
to 3.25 for road-racing engines of the highest specific power output. The normal design criterion
is for the value of ds to be the same as d4, i.e., the center section is of constant area.
The remaining diameters to be determined are that for d2 and d3 and these are calculated
by the following expressions:
where
and 43
do = die* 12 and d? = die* 13
x 12 ~ Lo + Li + L/
Li + Li
Lo + Li + L
^2
A)
Vh
xl°g< _i
dj.
xlog£
v d i;
(6.2.9)
(6.2.10)
(6.2.11)
and 1.25