Determine injector size from known physical parameters

NOTE! Incredibly bold assumptions Ė teee heee! HEY, you gotta start somewhere!!

Assumptions:

 

*      Highest fuel consumption will occur at peak torque

*      Peak torque occurs at 3700 rev/min

*      Peak fuel demand is 18 mi/gal or 6.4 Km/litre

*      Differential ratio is 3.44:1

*      4th gear is 1:1

*      Tyre size is 145x80x10 which is 1060 rev/mi or 660 rev/Km

*      Maximum duty cycle available for balanced running is 58% of 1 revolution

 

6.4 Km

*

1000 m

*

litre

=

6.4 m

=

0.156 ml

litre

 

Km

 

1000 ml

 

ml

 

m

 

3700 engine rev

*

1 wheel rev

=

1075 wheel rev

*

Km

=

1.630 Km

min

 

3.44 engine rev

 

min

 

660 wheel rev

 

min

 

1.630 Km

*

1000 m

=

1630 m

min

 

Km

 

min

 

0.156 ml

*

1630 m

=

255 ml

m

 

min

 

min

 

 

 

 

 

So if the injector is running at 58% open time its total capacity will then be

255 ml

*

1

=

440 ml

 

min

 

0.58

 

min

 

 

Since those 440 cc are being fed to the engine by 2 injectors, each will have a capacity of 220 cc/min. Using those same parameters in a spreadsheet we get:

 

CHECK: The 5.7 L V8 Corvette uses eight 219-230 cc/min injectors. Thatís an equivalent of a 2.8 L 4 cylinder roughly double our 1.3 L . Since we are using 2 injectors to feed the whole engine instead of 4, thatís about the same as a 1.4 litre. QED