Modded Mustang Forums banner

1 - 7 of 7 Posts

·
4POINT6
Joined
·
429 Posts
Discussion Starter · #1 ·
Just wondering what injectors to use with my saleen blower. Came with 30 pounders but that's meant for stock setup with stock boost and I will be running 10-12psi. Should be around 370-390rwhp.
 

·
Registered
Joined
·
2,936 Posts
42 lb/h will be running around 85% duty cycle at 475 fwHP, 400 at the wheels.



HPmax is flywheel HP, BSFC is Brake Specific Fuel Consumption, a rule of thumb value for calculating how many pounds of fuel is required per HP. use 0.5 lb/HP for n/a engines and 0.6 lb/HP for f/i.

42 * 8 * .85 / 0.6 = 476.0 fwHP
 

·
Registered
Joined
·
2,936 Posts
I'm guessing he's headed for 10-12 psi at 370-390 rwHP...
 

·
Registered
Joined
·
6,974 Posts
42s will work. They will handle much more than 470 flywheel hp.
 

·
Registered
Joined
·
2,936 Posts
42s will work. They will handle much more than 470 flywheel hp.
Yes they will, two ways. You can push them to 95% duty cycle bringing the maximum fwHP up to 530, or you can run them at higher than 39.15 psi differential (Ford's standard) which increases their maximum delivery rate.

The standard pressure drop for injector rating is 3 bar (43.5 psi), and if the operating pressure is not specified this is normally assumed--except in Ford discussions because Ford operates injectors at 39.15 psi (though this is nominally referred to 40 psi the value 39.15 is used in all Ford injector specs). This actually downgrades rated capacity from the industry norm and is why in Bosch reference catalogs you will see the 21 lb/h pink injectors used in the later New-Edge GTs listed as 22 lb/h units.

The formula for calculating injector capacity resulting from changing fuel pressure is:



So for the pink 21 lb/h injectors, rated 22 lb/h by Bosch:

(39.15/43.5)^0.5 * 22 = 20.87 lb/h.

Ford rated (39.15 psi) 42 lb/h injectors, operated at 60 psi pressure drop, become:

(60/39.15)^0.5 * 42 = 51.99 lb/h injectors

Eight 52 lb/h injectors at 85% duty cycle will support:

52 * 8 * 0.85 / 0.6 = 589.3 fwHP.

I.e. saying "42 lb/h injectors" without knowing (or assuming) the operating pressure is meaningless...
 
1 - 7 of 7 Posts
Top