A few things need to be known before we start.Injector 'duty cycle' time,this is the time ,in % ,the injector is open,sometimes called the pluse width.For race motors safe cycle is around 0.85.Rembember that an injector can only open & close so fast(min dynamic flow range).With too big an injector the ECU will try to lean out the fuel and can select a pulse width shorter than the min dynamic flow range of the injector.Bigger is not always better.To establish the fuel reqired can use the following:
Fuel in lbs/hr=(max HP x BSFC /(Number of injectors x duty cycle)
BSFC is the brake specific fuel consumption,the amount of fuel needed per unit of power produce.Only ENGINE dyno data can give you this butwe can estimate:-
High Compression 0.45>0.55, Low Compression 0.50>0.60, T/c & s/c 0.55>0.65.
An s/c set up has to take into account the parasitic losses to the s/c,an engine makes say 250hp with a s/c,it takes 30hp to drive the s/c so the net hp is 220hp.
Example on a 215hp motor.
Injector size =(215hp x 0.55) /(8 x 0.80)= 18.5lbs hr, thats on an 8cyl.The max safe duty cycle on OEM injectors is around 0.80duty cycle.Soc Ford pressure regulators operate at around 39-40PSI,with adjustable regulators you can increase the flow rate ,but dont go above 55 psi,the lines and connections wont take it!
To calc a new flow rating use the following:
New flow rate ={sq root of (new press/ old press)} x old flow rate.The two rules of thumb are ,dont go too big with injectors,dont go too lean with mixture.Hope some of this help...Regards Terry Haines, Haines Motor Sports Inc (PS TRUE engine dyno,not vechicle,data is best for these calcs) by Terry Haines
So with that equation, 240hp * .45 / 6 cylinders *.8 duty cycle = 22.5 lb injectors. or should use 24 lb injectors.
So 6 cyl * 19 inject * .8 duty cycle / .45 = 200 max HP w/o increasing Fuel pressure.
My interpretation....
