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would bigger/better injectors help my engine any?

C

cjben

NAXJA Forum User
Location
Illinois
I am putting a 96 4.0 in my 92 xj. I am doing the 2000 intake manifold update,mopar header,flowmaster muffler, cold air intake,bored throttle body and spacer. I have heard about putting 5.0 ford injectors in the 4.0 for a performance increase,but mostly on stroker motors or internally modified engines. would it help on my motor with a few bolt on mods?I am just wanting to know while I have the engine apart. thanks!!
 
Later Ford 302 injectors flow the same rate as the OEM 4.0L (19#/hour,) but they have four smaller nozzles, which helps with fuel atomisation. So, I do believe there is a small increase in fuel efficiency and power output (but you'd have to do before/after on dyno runs to find out exactly how much. I don't think it's enough to replace them outright, unless they want replacing anyhow.)

Installing a "bigger" (flows more fuel) injector on a stock engine won't be much help, simply because the ECU will compensate for the "rich" condition by narrowing the pulse width - or injector "open" time.

Installing a bigger fuel injector is like installing a bigger carburettor - if you've bored/stroked the engine to increase displacement, it can be a good idea (size them to match the displacement of the engine.) However, simply installing larger injectors won't be enough help to warrant the work and expense (unless you're having it done for no cost in parts and materials.)

Save replacing them for when they're finally due - like the body seam is leaking, or something like that.
 
5-90 said:
Later Ford 302 injectors flow the same rate as the OEM 4.0L (19#/hour,) but they have four smaller nozzles, which helps with fuel atomisation. So, I do believe there is a small increase in fuel efficiency and power output (but you'd have to do before/after on dyno runs to find out exactly how much. I don't think it's enough to replace them outright, unless they want replacing anyhow.)

Installing a "bigger" (flows more fuel) injector on a stock engine won't be much help, simply because the ECU will compensate for the "rich" condition by narrowing the pulse width - or injector "open" time.

Installing a bigger fuel injector is like installing a bigger carburettor - if you've bored/stroked the engine to increase displacement, it can be a good idea (size them to match the displacement of the engine.) However, simply installing larger injectors won't be enough help to warrant the work and expense (unless you're having it done for no cost in parts and materials.)

Save replacing them for when they're finally due - like the body seam is leaking, or something like that.
Click to expand...

I have the Ford injectors and I noticed better throttle response and idle quality. I got mine on E-fence for $20.
 
jeeperjohn said:
I have the Ford injectors and I noticed better throttle response and idle quality. I got mine on E-fence for $20.
Click to expand...

If you got the Ford "four-hole" units, that is about what I'd expect (due to better fuel atomisation.)

I'd not be surprised if you picked up 1-2mpg as well, for the same reason. However, it's enough work that I'd do it either to replace failed/failing units, or to complement other mods (rather like doing a bored throttle body - it has rather minimal effect on its own, but complements other mods nicely at times.)
 
The stock injectors are junk, but work. I replaced mine after 160k with some Bosch green meanies and it made a significant difference. More power and better economy than when new. $240 was fair price. Injector specs did change over the years, so be careful. Sometimes the improved injector spray pattern will make up for the spec difference.
 
cjben said:
I am putting a 96 4.0 in my 92 xj. I have heard about putting 5.0 ford injectors in the 4.0 for a performance increase,but mostly on stroker motors or internally modified engines.
Click to expand...
If you're talking about the 19# Ford injectors you would actually be putting smaller ones in versus the ones that come in a '96 4.0 motor. I'm reasonably certain the '96 model already has a 23# flow rate.

Did I miss something here?

FWIW, I replaced my 18.6# Renix injectors with some from a ~'93 rig that flow, IIRC, ~21#. My mileage is about the same and they all work with no leaks which is what I was after.

EDIT: Could the fuel pressure difference be why this might make sense?
[FONT=arial, helvetica, sans-serif] Model Year, ...Part #, ......Colour, .....Fuel Pressure, ...Static Flow,
'87-'90, ........53003956, ...Dark Tan, ..39psi, .................18.6lb/hr
'91-'93, ........33007127, ...Brown, .......39psi, .................21.0lb/hr
'94-'95, ........53030343, ...Tan, ...........39psi, .................21.0lb/hr
'96-'99, ........53030778, ...Grey, .........49psi, .................23.2lb/hr
'99-'01, ........04854181, ...Blue tip, .....49psi, .................22.5lb/hr[/FONT]
 
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sorry i didn't clarify. I am only using the block off of the 96 engine. I am using the computer,sensors,injectors and wiring harness off of the 92.
 
cjben said:
sorry i didn't clarify. I am only using the block off of the 96 engine. I am using the computer,sensors,injectors and wiring harness off of the 92.
Click to expand...

Then it would seem the Ford injectors would flow less at the same pressure than the ones you have now. You would need to step up a notch. My math tells me you would need a 26# injector at 49 psi to give you the same 21# at 39 psi.
 
John90XJ said:
Then it would seem the Ford injectors would flow less at the same pressure than the ones you have now. You would need to step up a notch. My math tells me you would need a 26# injector at 49 psi to give you the same 21# at 39 psi.
Click to expand...

Your are exeactly right. a 26# injector is what you need. The jeeps came with a DEKA1 fuel injector in them. You can upgrade to a DEKA4 (like in the fords) but you need to use a 26# injector so that you can achieve the 2.38g/s. I however DO NOT recommend using BOSCH injectors. They are a 3 piece design that sucks:looser: . This is why you always hear people complaining about thier injectors leaking around the body. I would use the SIEMENS injectors. The part number should be 53003956. I design fuel systems for a living so I know what I am talking about when I say that BOSCH injector suck.
 
sjx40250 said:
So is the preasure to flow rate ratio linear?
Click to expand...

Everything I've read indicates that it is.

If flow is 25# at 50 psi, then it will be 20# at 40 psi, or 80% of the rated amount.
 
John90XJ said:
Everything I've read indicates that it is.

If flow is 25# at 50 psi, then it will be 20# at 40 psi, or 80% of the rated amount.
Click to expand...

I'm fairly sure it's linear (ish,) but it's not that simple. I'll dig up the formula for you later (which I think I got from Marren Fuel Injection - if you can't wait, Google them.)
 
VAwheeler said:
Your are exeactly right. a 26# injector is what you need. The jeeps came with a DEKA1 fuel injector in them. You can upgrade to a DEKA4 (like in the fords) but you need to use a 26# injector so that you can achieve the 2.38g/s. I however DO NOT recommend using BOSCH injectors. They are a 3 piece design that sucks:looser: . This is why you always hear people complaining about thier injectors leaking around the body. I would use the SIEMENS injectors. The part number should be 53003956. I design fuel systems for a living so I know what I am talking about when I say that BOSCH injector suck.
Click to expand...

I looked up this part # and it comes up with stock 4.0L H.O. Cherokee injectors. What year did they start using the deka IV injectors in 302s? I'd like to keep an eye out at the junkyard. Thanks.
 
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square root of (new pressure/old pressure) * old flow rate = new flow rate
 
coastie124 said:
I looked up this part # and it comes up with stock 4.0L H.O. Cherokee injectors. What year did they start using the deka IV injectors in 302s? I'd like to keep an eye out at the junkyard. Thanks.
Click to expand...

Crap!!:doh: I am sorry I gave you the original part number. To my knowledge Jeep never installed Deka IV's. I was just trying to provide you guys with an acceptable replacement part number to convert a Deka I to a Deka IV. I will try to remembe rto look up the part number at work tomorrow.:geek:. Sorry bout that.:roll:
 
Just for a heads up. I just got a set of used 19# injectors from an 01 Mustang Mach-1 with the 4.6L I believe.. they have 40k on them and look new. You also get two spares when you buy a set off of a Mustang. They work great. (you arent able to use the original clips but they fit just fine in the rail and the top end feels a little better too, as well as throttle response)

$45 was a pretty good deal I thought. << They are ALL OVER ebay..
 
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VAwheeler said:
Crap!!:doh: I am sorry I gave you the original part number. To my knowledge Jeep never installed Deka IV's. I was just trying to provide you guys with an acceptable replacement part number to convert a Deka I to a Deka IV. I will try to remembe rto look up the part number at work tomorrow.:geek:. Sorry bout that.:roll:
Click to expand...


still waiting on that new part number you were gonna look up tomorrow 4 months ago. LOL

thanks.
 
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