Injector confusion

Performance mods and Advanced Stroker discussion.
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lazyxj
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Stroker Displacement: 4.6
Vehicle Year: 2001
Vehicle Make: Jeep
Vehicle Model: XJ

Injector confusion

Post by 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
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Cheromaniac
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Re: Injector confusion

Post by Cheromaniac »

lazyxj wrote: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.
1992 XJ 4.6 I6 - 5MT - Stroker build-up, Stroker "recipes" Sold
1995 Mustang GT - 4AT - Modded Sold
2006 Mustang GT - 5MT - Modded Midlife Crisis Car :mrgreen:
lazyxj
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Stroker Displacement: 4.6
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Vehicle Model: XJ

Re: Injector confusion

Post by 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
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Re: Injector confusion

Post by Russ Pottenger »

lazyxj wrote: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
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Cheromaniac
I live here
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Posts: 3180
Joined: March 8th, 2008, 12:58 pm
Stroker Displacement: 4563cc
Vehicle Year: 1992
Vehicle Make: Jeep
Vehicle Model: Cherokee
Location: Cyprus
Contact:

Re: Injector confusion

Post by Cheromaniac »

lazyxj wrote:Thanks also for continuing to participate in the forum...even if you do own a Ford.
Yeah, but not just any old Ford. :mrgreen: It's this one:

http://www.angelfire.com/my/fan/Mustang2006GT/Home.html
Russ Pottenger wrote:Dino's continuing participation in the Jeep community is truly appreciated
Thanks Russ. :cheers:
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