Anyone know what the PSI rating is of the stock fuel injectors in the '96 5.0l engine? I am thinkin about installing higher PSI injector in my new motor (E303 cam, GT-40 heads, Eddy intake man, Heddman headers), but I am not sure which injectors to go with, or if there will be more mods necessary to do it.

 

The stock injectors are rated for 19 lbs/hr at 39 PSI.
Injectors do not control the injection pressure. That is done by the fuel pressure regulator. Typically ajdustable regulators can increase the injection pressure to as high as 60 or 70 PSI.

For any given injector, flow is a function of the square root injection pressure.
i.e.

flow at rated pressure x (pressure P/rated pressure)^0.5 = flow at pressure P

for your stock injectors running at 60 PSI:

19# x (60/39)^0.5 = 23.5 lbs/hour

 

Thanks Ranger. My thought was that it might be a good idea to have a fresh set of injectors in the new motor, but I wasn't sure if I should go for stock units, or some Accel's. If I understand what you're saying, I could buy higher rated injectors, and it wouldn't hurt, because they would perform the same as OEM's, unless the regulator were adjusted. Is the stock regulator adjustable, and would I need to get a custom tuner (Xcal2?) to make other adjustments to match? Thanks again.

PS-
I'm not doin this work myself, in case you are lookin at this and noticing that I am out of my depth here I'm just lookin for some advice as to what to order up, and what to ask my mechanic to do for me while he is installing my new motor.

 

Yes, you will need a custom tune.

You cannot simply change the output of the injectors without letting the EEC know

I use a TWEECER

 

Bigger injectors do not make more power. They simply provide enough fuel for the amount of air the engine ingests. Unless you're adding a camshaft and/or bigger heads or other mods that significantly increase the amount of air your engine takes in, bigger or higher pressure injectors will do absolutely NOTHING for you.

Your stock injectors provide at least enogh fuel for:

((8 x 19 lbs/hr)/ 0.50 Lbs/HP-hr) x 0.80 duty cycle = 243 HP

If you pust the BSFC to .47 and the duty cycle to 90%, the HP from the stock injectors could go as high as:

((8 x 19)/0.47) x 0.90 = 291.

Unless you're making over 243 at the flywheel, you have no earthly use for more fuel. Unless you're making something close to 290 at the flywheel, you may not need more.

With a 96, you have an OBD-II processor. Count on bigger injectors to not only give you no improvement but also to throw error codes and light up your MIL

 

Yes, I am pumping more air through the motor. That's why I am considering it. The new motor (which has not arrived yet), has an E303 cam, and GT40 heads, as well as an Eddy intake manifold, and shorty headers. I intend to go to hi-flow cats, existing 2.5" Flowmaster exhaust, and I might switch to the twin 61mm throttlebody (if I do a fuel delivery upgrade). I think that XCal2 might be a must for this job. Hopefully Troyer does a group purchase again.

 

An E303 (same as a Crane 2040) in a truck? You may not like it as well as you think. It makes lots of HP but you have to spin the pee out of it.

With that setup you're going to need 24# injectors. You can get a set rated at 39 PSI and stick with the stock regulator or you can get a set with some other pressure rating and an adjustable regulator. If you're willing to run as high as 60 PSI, you could make do with the stock injectors, but I wouldn't recommend it.

Have you thought about the fuel pump situation? Your stock pump will fall just a hair short of being able to supply enough fuel for those injectors at WOT and max RPM so it may limit your power. If may also lean the engine out under load at high revs which is a recipe for burned pistons.

Whatever injectors you end up with you're going to need either a new MAF meter or have your stock one reworked to match the thruput of the new injectors. You're also going to need some reprogramming to the EEC-V.

 

Thanx for the good info Ranger.

Ford Racing E303 cam

I will keep working on the correct solution, so that the engine installation goes as smooth as possible. As crazy as it sounds, I am working in a fairly tight budget on this project, so I had to rule out the stroker (arguably the only way one can get the desirable low end torque numbers a 302 truck owner really wants). So, settling for a motor that is spec'd out similarly by Ford Racing's GT40 motor, (which claims 340 HP, and 310 ft/lbs of torque) is not a fate worse than death for me. Understanding that what my truck actually dynos at will be the true measurement of HP and torque, I am confident of major gains over the stock motor. Gettin it to run smoothly is what I am looking for help with here.

Given the specs on the Cam I linked you to above, do you believe the motor will run decent enough on stock injectors, stock regulator, and stock MAF, until I tackle this tuning/fuel injection project? I would like to address that separately if possible, even if that means avoiding sustained, or frequent WOT situations.

Thanks again,

Jon

 

You cannot cheat on injector size. The engine will require something on the order of 0.5 lbs of fuel per HP per hr; there's no way around that. Ford even used the 24# injectors on the 93 Cobra engines, rated at only 260 HP. If you're really anywhere remotely near to 340, you're going to need the 24# units.

Your present fuel pump is rated for 115 lph @ 39 PSI. That's about 190 lbs/hr. Figuring a 10% reserve capacity in the pump, it tops out right at 340 HP. If you raise the injection pressure to 55 PSI so you can make do with the smaller injectors, the pump rating drops to only 95 lph which, at the same 10% reserve, is only enough for about 280 HP. Your engine is probaby going to make more than 280 HP, so no matter how you look at it you cannot squeak by with your present 19# injectors.

 

New injectors it is! I'll pickup a set of 24lb Accels from Summit.

Dang, man. You've got some serious fuel injection calculations figured out. You want some side work? I believe you were once living in this neck of the woods - do you visit much?

 

Injectors are only part of the puzzle. You also need an air meter matched to them. You can either buy a new one or have yours recalibrated. You're likely to have some drivability issues until you get your EEC-V reprogrammed as well.

 

Once I came to understand that the injectors had to go, I figured that meant I'd be down until I had reprogramming done. I'll call Troyer tomorrow. I have a shop lined up to do the motor installation, but I don't think he signed up for this much fun.

 

You and that new motor...get it in already...

 

I NEED SOME HELP I HAVE A 99 F150 WITH THE 4.6 AND I WAS WONDERING IF THERE IS ANY NEED FOR BIGGER INJECTORS IF I HAVE FULL EXHAUST, K&N FIPK, HYPERTECH POWER PROGRAMMER, BBK THROTTLE BODY, POWERDYNE TB SPACER, SUMMIT MASS AIR, FORD RACING PLUG WIRES,AND ACCELL COILS? THINK MAYBE I NEED BIGGER INJECTORS IF SO HOW BIG?

 

Unless you go to a set of improved/modded heads and/or aftermarket camshafts (or, obviously, a power adder), you're not going to need or want bigger injectors