My Jeep doesn't really have engine work done to it, except I just purchased a 68mm throttle body and custom intake for it. It's a 99 XJ with a 4.0L, stock internals, stock header, stock exhaust up to a 3" hi-flow cat, 2.5" pipe and a 2.5" Flowmaster 40 Delta series with a 2.5" tail. I just have a snorkle, I don't know how much of a difference that makes as far as forced air goes.
I'll probably be getting a header soon and potentially a cam, but that won't be for a while.
However, I do have 24lb. Ford racing injectors, four-hole type, and I heard they'll fit in my Cherokee. Are they okay size-wise with what I've got in my XJ? They were originally for my boyfriend's 91 Mustang LX 5.0, and said to fit a 87-93 5.0 fox body.
I just want to try to get the best out of my engine that I can now that I'm pretty much finished with my suspension and such.
__________________ Female owned, built & beaten.
Charlee "Nancy" '99 XJ: 10" lift, 37x14" Iroks - D44 front & rear, Safari Snorkle, ETC. ETC.
I know earlier model 4.0s all run 19 lb. injectors. I can't imagine later models would require much different.
On a side note. I replaced 100K mile stock injectors in an old '90 with some low mile 19 lb. injectors from a ford 5.0. I did this based on supposed gains due to a better fuel spray pattern. I noticed zero improvement. They are a good cheap replacement due to all these 5.0 guys swapping for 24+ lb. injectors, but unless you "need" to replace your current ones I'd not mess with them.
Unless you stroke it 24 lb. is overkill. On the other hand do it for our edumucational benefit.
The following is a list of the injectors used on the 4.0L since 1987 along with their rated static flow:
Model Year Part Number Color Fuel Pressure Static Flow
1987-1990 53003956 Black 39psi 18.6lb/hr
1991-1993 33007127 Brown 39psi 21.0lb/hr
1994-1995 53030343 Tan 39psi 21.0lb/hr
1996-1999 53030778 Grey 49psi 23.2lb/hr
1999-2006 04854181 Blue Tip 49psi 22.5lb/hr
The injector flow rate varies as the square root of the pressure drop across the injector. The stock '91-'95 4.0 injectors are rated at 22lb/hr @ 43psi fuel pressure, so at 39psi they flow ( sq. rt.(39/43) x 22.0 = 21.0 ).
For stock/modified 4.0 engines or stroker build-ups the following injectors can be installed. The flow rates are:
The '95 Jeep 5.2 ZJ/Dodge 5.9 injectors (Part no. 53030262) are rated to flow 24.6lb/hr at 39psi.
The selection of injector size will depend on the estimated horsepower output, brake specific fuel consumption BSFC (assume 0.5), no. of cylinders, and the injector duty cycle (assume 80% or 0.8). The formula is: Injector size (lb/hr) = (horsepower x 0.5)/(no.of cylinders x 0.8)