Injector confusion

[lazyxj]

Here is what I'm building
2001 XJ California emissions
4.6 Russ Pottenger short block
Russ Pottenger 0630 P&P, with big valves
CompCam 68-231-4.
Ported late-model intake manifold
62mm TB
Banks header

My build looks very similar to Dino’s 4.6L 268-HP low-buck stroker, which specifies a 24-lb injector.
Problem is, almost every build sheet specifies 24-lb injector, regardless of the horsepower rating, no matter if the projected output is 240 or 268-hp.
Logic would seem to dictate a larger injector for a higher output engine.

According to the injector size formula, on Dino’s site (and many other sites), a 268-HP 4.6 should use 27.9-lb injectors
Injector size (lb/hr) = (horsepower x 0.5)/(no.of cylinders x 0.8)
Let’s say my engine will produce a conservative 260-HP
(260 X .5) (6 X .8) = 27.2-LB
So, should a 27-lb @49psi injector be used or am I missing something?
Are the formulas invalid or do they not take into consideration other aspects to the build? Black magic maybe?

Something like this?
https://fuelinjectorconnection.com/coll ... r-27lb-set

[Cheromaniac]

My build looks very similar to Dino’s 4.6L 268-HP low-buck stroker, which specifies a 24-lb injector.
Problem is, almost every build sheet specifies 24-lb injector, regardless of the horsepower rating, no matter if the projected output is 240 or 268-hp.
Logic would seem to dictate a larger injector for a higher output engine.

I did indeed specify the Ford 24lb injector on more than one build but note that in each case, the fuel pressure (and injector flow) is different for each application. On the Jeep I6 you'll need an injector flow in lb/hr (adjusted for fuel pressure) that's 1/10 of the expected crank HP.
The Ford Racing 24lb injector is rated to flow ~24lb/hr at 39psi. On a 49psi injector rail it'll flow 26.9lb/hr which is exactly what you'd need on an I6 engine in a '96-'04 Jeep that produces ~270hp. The injectors you referred to in the link would also work.

[lazyxj]

Thanks Dino for confirming what I had hoped I understood.
Like so many forums, the core group of knowledgable people is shrinking, as they move onto new interests and hobbies.
Thanks also for continuing to participate in the forum...even if you do own a Ford.

I own a Ford too, used to pull our Jeep around the USA.
https://www.flickr.com/photos/lwade/alb ... 7829693253

[Russ Pottenger]

Thanks Dino for confirming what I had hoped I understood.
Like so many forums, the core group of knowledgable people is shrinking, as they move onto new interests and hobbies.
Thanks also for continuing to participate in the forum...even if you do own a Ford.

I own a Ford too, used to pull our Jeep around the USA.
https://www.flickr.com/photos/lwade/alb ... 7829693253

Total agreement with you Larry.
Dino's continuing participation in the Jeep community is truly appreciated

[Cheromaniac]

Thanks also for continuing to participate in the forum...even if you do own a Ford.

Yeah, but not just any old Ford. It's this one:

http://www.angelfire.com/my/fan/Mustang2006GT/Home.html

Dino's continuing participation in the Jeep community is truly appreciated

Thanks Russ.

[RockyMtn96XJ]

Is there any harm in buying injectors that are "too big" for my build? As in, can I use the 26.9lb injectors in my ~245hp modified poor man recipe?
Just curious, so I know what my options are when buying injectors next week. If I find bigger ones I just want to know If I can use them or if I need to find the "24.x lb" injectors.

If I use larger ones, would I need an adjustable voltage regulator for my MAP to turn the fuel down at high RPM?

[Cheromaniac]

There's no harm in buying bigger injectors than you might really need as long as you have an ECU that can be reprogrammed to reduce the injector duty cycle. Luckily yours is OBD 2 so that makes it possible.

[RockyMtn96XJ]

Thank you for the info.