Determine gas speed in inlet port
Assumptions:
At high engine speed the gas speed in the port
is higher than the velocity of the fuel being sprayed from the injector
Engine speed is 3700 rev/min
100% VE
Valve open time is 260°
Engine size is 1330 cc or 332 cc per cylinder
Inlet port average diameter is 1.3” or 3.3 cm
which is 8.56 cm2
|
3700 |
* |
360° |
* |
|
= |
22000° |
= |
22.2° |
|
|
|
|
|
60 sec |
|
sec |
|
ms |
The valve is open for 260° so
|
260° |
* |
ms |
= |
11.7 ms |
|
|
|
22.2° |
|
|
|
332 cm3 |
= |
28.4 cm3 |
|
|
11.7 ms |
|
ms |
|
Through continuity, pushing a volume through a fixed orifice
we get
|
28.4 cm3 |
* |
1 |
= |
3.31 cm |
= |
33 mm |
(about 100 km/hr) |
|
ms |
|
8.56 cm2 |
|
ms |
|
ms |
The distance from the cylinder head face, where the injector
tips should be, to the back of the valve is something like 75 mm so it would take
in the order of 2.5 ms for the fuel charge to reach the valve throat.