injector size for 306 with a little boost

[novi306]

what size inj. would i need for a 3300 lb car going through traps at 114 mph? when i use some of the mustang sites they vary on estimated horse power .i know for supercharged applications the bsfc is to be .6 to .7. i plan on adding a smaller crank pulley soon so that would change everything anyway, but i dont know what i am actually pushing right now in terms of hp.so do i go with what i would think it would need with the pulley now or will that be too much inj to run? it has the usual hds ,int ,cam ,ect...with the novi 1000 but right now i have 24 lb inj. just need a general direction to go with

[89ragtopgt]

I have a novi 1000 with an 8inch asp crank pulley with heads cam ect... 7 to 10psi .... and i can log the injector duty cycle with tweecer chip programmer and logger and i can hit 85% duty cycle with 42lb green tops. and that about as high as you want to go with the duty cycle. i have ~ 400rwhp

[speedytang]

I always recommend 42lb injectors for a street blower combination.

[NMNOTCH]

Given your trap speed of 114mph in a 3300 car this estimates 381 rwhp and about 450bhp. injector needs: (power)(BSFC) / # injectors
(450)(.65) / 8 = 36.25lb/hr


Don't forget your fuel sysyem requirement to support the bigger injector

(power * BSFC) (1 + safety margin)= lb/hr
lb/hr/7.25= gallons/hr (gallons)3.785 liters= liters/hr

(450 * .65) (1.30) 380.25lb/hr
380.25/7.25 = 52.45 ( 52.45)3.785 = 198.52liters/hr

[novi306]

right now i have 24 lb inj. and i have a 255lph pump i have the 8.1 disk in the fmu ,so what base fuel pressure should i be running right now?

[NMNOTCH]

Ususally with an FMU you run the same fuel pressure that you would run in naturally aspirated form and the FMU will increase the fuel pressure under boost a proportional amount.

IMO I would ditch the FMU an run the 42LB injectors with a 1:1 regulator.

[novi306]

so what is it about lightning mass air meters for the bigger inj. ??

[NMNOTCH]

The meter has to be matched or calibrated for the injectors you are running. I would reccommend a Pro M or Pro flow whatever they are calling themselves nowadays 80mm calibrated for the injectors you are planning to run. The problem with the MAF is it is only as good as it is calibrated. Some run great some don't. Don't waste your time with a C and l as they use a sampling tube to trick the ecu into how much air is coming in. As stated earlier the FMU is a band aid also and should be left for the person who will bolt a kit on to a completely stock vehicle and is looking for just a little boost in performance. Obviousily you don't seem to fit that criteria or you probably wouldn't be asking.

You could always go with a standalone MAP based system. I never believed until I tried it:) This way you can sel the meter and never worry about recalibrating again.

[novi306]

thanx for the info