94ford5liter

When going to larger injectors I was just wondering what the increments for each set are. I know 24lb injectors are good to about 350rwhp. What about 30lb,36lb,42lb, etc? Does the limit increase about 50rwhp per 6 pounds more on each injector you have? Plans for a supercharger are not far off, so wanted to figure out what size injector I should use so I have room to grow.

luckythirteen13

if your going sc, run 42s. the 42s will support enough hp to split your block.

its hard to say for certain what the hp rating of each injector because there are a few variables such as the fuel pressure you run and the duty cycle

Tony71502

Right on, duty cycle = what % of the cylinder's compression stroke the injector is spraying fuel in.

If the injectors are not big enough they have to spray fuel the entire stroke (100% duty cycle) and that may not be enough fuel if they are undersized injectors. That's the basis for selection, basically. Not horsepower.

disposablehero27

www.rpmoutlet.com shows what each injector is rated at per each set. just look up injectors as if you were gunna buy them. shows how much they are rated to.

94ford5liter

Well my other problem is, I can't find a mass air for 94-95 cobras that is calibrated above 36lbs. It seems like if I go above that, I would just have to make a lightning mass air work. I am going to be aiming for about 400rwhp, so I assume 36lb would be plenty.

NoGo95GT

My car makes 400+rwhp and I am running 30lb injectors with an FMU and have no fuel problem. Plus I am running 15psi boost; 12-13 psi in the hot summer.

94ford5liter

was 396 rwhp the 30lb injector limit on your car? Because I noticed in signature it says you ran out of fuel on the dyno at that level.

Liquid_02

If un-sure go bigger. You don't want to run any higher than an 80% duty cycle, your injectors will burn out and fail pre-maturely if you do.

Quick little equation you can do is:

HP X BSFC
------------------------------
#of Injectors X .80 (duty cycle)

So doing this... say you want 400hp, and your BSFC is .50 being NA

400 X .50
----------
8 X .80

=

200
----
6.4

=

31.25lbs/hr

So for 400hp w/ 8 injectors you need 36lbs injectors to do it safely. I ran this equation many times before I bought my 42lbs injectors for my car. Keep in mind fuel pressure all plays a role as-well, this equation works normally for people running the industry standard 43.5lbs pressure.

JD1969

I am at about 400 rwhp, running 42's with a Vortech V2SQ. No computer tune, I just use a wideband, timing and fuel pressure. I am running a safe AF ratio. Did you call Pro M for a MAF? 94 Cobras are just 5.0's with a GT40 heads and intake, they really are nothing exotic.

94ford5liter

I know they are not very different, but the computer is different, so apparently they need a different MAF compared to the standard gt. I suppose I could just try calling them. Most sites don't even carry a mass air unit for the 94-95 cobra though, and the sites I found that do only go up to 36lb. I guess because they made so few of them in comparison the the GTs.

Oh I see that on the PRO-M website I can get one for 42s because you select your vehicle type and just put in the injector size. Thanks JD . Didn't you have a camaro ss for a while?