Thread: Fuel injector questions

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  1. #1 Fuel injector questions 
    Senior Member Lifetime Supporter ZJ TINS's Avatar
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    So I was looking at the you tube 4 hole vs OEM single hole fuel injectors and the atomization seems to be much better. Has anyone simply swapped fuel injectors and noticed a MPG or power improvement?

    Also is there any cheap (good) drop in 4 hole fuel injectors for a 96 I6? junkyard is fine. I think I need a 49 psi and 24 lb/hr unit (or close to it). It seems to me the excess fuel will be regulated down by the computer. But later a stroker can use the full flow but for now I would hopefully see a MPG improvement due to the atomization.
    Last edited by ZJ TINS; 09-26-2010 at 06:23 PM.
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  2. #2 Re: Fuel injector questions 
    Senior Member Lifetime Supporter ZJ TINS's Avatar
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    Well I found a guy on ebay who has drop in 4 hole injectors around 23-25 lbs (at least he says). Too late for our trip this week but I will end up trying them i think. Most of his sets are under $200 with warranty. right now i am looking for an MPG gain due to better atomization, means the computer should learn and feed it less fuel. I will let you all know when this happens and the results. Eventually I am going to stroke it 4.5 or 4.6 low buck. So they should work for both.
    “I ask, sir, what is the militia? It is the whole people, except for a few public officials.”- George Mason
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  3. #3 Re: Fuel injector questions 
    Senior Member Grand Slam West Planner
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    I had these injectors (Ford Mustang) on my '95 4.0L. I didn't notice any MPG gain. It did seem to give a bit more power, but that could have been wishful thinking. I think mine ran rich after the injector replacement, so the '95 computer didn't seem to learn.
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  4. #4 Re: Fuel injector questions 
    Senior Member DJJordache's Avatar
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    Quote Originally Posted by ZJ TINS View Post
    Well I found a guy on ebay who has drop in 4 hole injectors around 23-25 lbs (at least he says).
    at what pressure? the 49 you need or the earlier 39psi?
    93' ZJ 4.7L STROKER, Clayton LONGARMS, 4wd conversion, 231 SYE, HPD30, 8.8, BFG 35's, 2000 manifold & injectors, Hesco fpr, Port & polish, LS1 valves, WJ Steering/brakes, KOR SliderZ & steering box brace, Clayton TB bracket and my custom trackbar, Crane ignition, B&M cooler, Tom Woods, etc....
    Quote Originally Posted by Krash80 View Post
    We're all insane here...
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  5. #5  
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    Well 93 to 95 had differnet injector sizes they actually flowed more than the later zjs I'm not sure why your zj didn't learn from them but if you just threw them in and gunned it that's why there's about a month period after the swap where your supposed to baby your vehivle so the computer can gradually learn from the new injectors

    Sent from my Ally using Tapatalk
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  6. #6 Re: Fuel injector questions 
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    How can the ECU "learn" open loop fueling?
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  7. #7 Re: Fuel injector questions 
    Senior Member Lifetime Supporter ZJ TINS's Avatar
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    My ZJ has 49 psi.
    Latest update. Install with MMO or something I used gas to wet the o-rings and had to reinstall four of the injectors cause I tweaked the o-rings.

    I cannot report on mileage because my intake/exhaust gasket was leaking and I just replaced it. If you get an APN header dump the gasket and go get a Felpro.

    I can say one thing, it starts immediately in all conditions. Was down to -7 oF and fired right up. Last year I had to crank for a while and a couple cylinders would catch and then the rest finally fire up. Looking back it felt like the cylinders were getting globs of fuel not a mist and would not fire and when they did it felt like too much fuel for a few seconds. The new injectors start the same no matter the temperature. The good start occurred before and after the gasket was replaced.
    Last edited by ZJ TINS; 03-02-2011 at 02:33 PM.
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  8. #8 Re: Fuel injector questions 
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    So ZJ Tins, Whats the outcome for the fuel mileage? Any updates on the injectors? Which ones did you actually install. What model application they come from
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  9. #9 Re: Fuel injector questions 
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    Same people sell any in the 5.2 flavor?
    93 ZJ 5.2.headersCAImoparPCMmsd,boredTB,efan, custom ugly bumper,KOR tb radsup,242, 5.5 lift Claytons LAs front adj SA's rear, d44 aussie locked, danaturdy w lockright, 35s
    Bloody box addict
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  10. #10 Re: Fuel injector questions 
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    I thought this was kinda pointless because the ECM will adjust the fuel accordingly. So, without a different tune, chip, piggyback system, the end will result should be about stock. Am I misinformed?
    I'm still waiting on the inexpensive shit to break!!!

    '02 WJ with 60's, locked, full hydo, ORI's, on 40's, and still have air conditioning!
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  11. #11 Re: Fuel injector questions 
    Senior Member Lifetime Supporter ZJ TINS's Avatar
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    here is the info i have. got him off ebay and asked sizing questions. ended up buying direct for less
    From: Michael Whicker <performanceefisystems@gmail.com>
    Sent: Thu, October 14, 2010 9:33:21 PM
    Subject: Re: fuel injectors


    I can get you a set of true 24-24.5 lb injector... or higher... However, the 23.5lb injectors should be perfectly fine for up to around 325HP. At this level the will not even be operating at an extreme duty cycle to provide the necessary fuel. I honestly do not believe you will have the need to go to a larger injector, but I can get you whatever you want. Unlike my competition, the injectors I sell as upgrades are a true 4-hole discharge injectors, not a purple Siemens single pintle injector that SLIGHTLY better than the factory Siemens single pinlte injectors. Let me know what flow rating of injector you would like. Anything over 24.5lbs/hr would have to be custom flowed to your specifications at my shop. If you buy the 23.5lb injectors directly through me I will give you a better price that what is on eBay. Thanks in advance for your business!

    Indy if you look at the video on you tube showing the spray pattern of a 1 hole vs 4 hole injector. the 4 hole atomizes the gas into a much finer mist. this means more complete burning so it is possible the computer learns to inject less because of the more complete burning.

    sorry not enough mileage to tell yet. i want at least 20 tanks of gas before i can say same or better. anyway with gas prices now we drive the camry most of the time.

    still fires up in cold better than the one hole , and i have yet to experience the apparent flooding/hesitation the 1 hole occasionally gave me.

    I got the 23.5 lb.

    blackbeer send him an email. his ebay posts many injectors.
    Last edited by ZJ TINS; 03-02-2011 at 02:32 PM.
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  12. #12 Re: Fuel injector questions 
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    I was reading in another forum that they used neon injectors on the XJ's.
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  13. #13 Re: Fuel injector questions 
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    I had free access to the four hole injectors from a Dodge Stratus 2.5L so I installed six of them into my 4.0L ZJ. I have noticed absolutely nothing different in two weeks time since the swap. It is just nice to know that I still have all six factory injectors in case I need to un-swap.
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  14. #14 Re: Fuel injector questions 
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    i know ist not a i6 but on my 5.2 i swapped over to ford 24lb injectors and the only thin gi can actually notice is a bit more better gas milage and pulls a little harder off the line but then agian u have to take into a account that they were factory injectors so ya the news will work better
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  15. #15 Re: Fuel injector questions 
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    I have found the benifit in injector upgrade without accompanying modifications to VE related components is drivability. I have run modded injectors, budget injectors, and top of the $line$ injectors in my 424whp (AWD) WRX. I see little to no difference in peak power on my dyno plots.

    What I do "feel" is the idle, starting (especialy cold starts on Ethonal), and low throttle cruise smoothing out with the "beter" quaility injectors. Good fuel atomization is far more important at lower intake air velocities, at higher RPM, the turbulant incoming air is doing a pretty good job of shaking things up, not to mention the increased heat in the CC and overall cylinder pressure aiding in vaporizing the mixture.

    The OE ECU is calibrated to the OE size injectors (obviously), in OL (open loop) operation when the ECU is ignoring the NB02 sensor, it has no way of knowing it is injecting more fuel than it should be, its simply following a calibration. OL operation is typicaly for start up, warm up, and heavy load/throttle acceleration, CL (closed loop = reading 02) is for cruise, light throttle, ect. The NB02 sensor is worthless for reading anything much leaner/richer than stoich (14.7:1 AFR). In OL the ECU just assumes it knows the injector size, and is precalibrated to go to x PWM based on load/TPS, MAP/MAF, IAT, and CTS. Are you asleep yet?


    I think going to better performing injecotrs that are size appropreate given modifications to increase VE is the way to go. How to determine VE? Messure MAF/MAP volts before the VE mod, and after, what % has the voltage increased is a pretty good indication of the VE increase. Obviously you need to map this with all the accompanying perameters to ensure an apples to apples comparison of before and after. Or, just guess, example, I added bitchen free flowing glass packs and a CAI, this should be good for at least 1% increase in VE, well it makes sence to add 1% to the injector size now.....

    Or when no VE improvments are present, going to a better injector of the OE size would almost certainly net an MPG improvment and deffinately a drivability/startability improvmnet. Ok Ill stop now.
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  16. #16 Re: Fuel injector questions 
    Member Sandvipr's Avatar
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    On my old Dakota with the 5.2, I ran some Ford performance injectors for a 5.0. They drop right in the fuel rails and the plugs snap right together. I think they were 24 or 26LB injectors. I noticed some decent performance gains- not sure on the milage though.... that was about 8 years ago too.
    '93 ZJ 42's, locked ton's, full-hydro, 5.38's 231, 8 pissed off squirrels- always looking to go bigger.....
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  17. #17 Re: Fuel injector questions 
    Junior Member 96grandbeater's Avatar
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    i did some pretty lengthy research into injectors when i was looking to do the 99+ intake swap on my 96 4.0L and all ive found out is bang for your buck 01+ neon injectors are the best way to go for your non internaly modded or charged air 4.0l. also noone had any conclusive mileage gains, just smoother running and easier starts. the jeep ecm doesnt learn anything in open loop, open loop is running off of purely predetermined peramiters, its when you get into closed loop that the computer will actually learn that the jeep is getting slightly more fuel and after a while it will turn the preasure down, maybe then you would get some fuel mileage gains but probably not enough to mention, also as most of us are running fairly modded jeeps getting them into closed loop actually is pretty tough, theyve got to be right at running temp(say goodbye to that if you have put in a lower temp thermostat) crusing(goodbye to that if you have a heavy foot or not nough gear) and many other things that can be toughish in our kind of vehicles. all in all id say doing the neon injectors is worth it if you dont have alot of fuel flow needs and your looking for a little smoother running
    96 grandcherokee laredo- 4.0L, 3.5" jy lift, welded 44a, beating the poopnoodles out of it whenver i can!!
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  18. #18 Re: Fuel injector questions 
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    so far no one has any true upgrade for performance/MPG. This has gone on thru many websites and forums
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  19. #19 Re: Fuel injector questions 
    Senior Member Lifetime Supporter ZJ TINS's Avatar
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    Yup no difference. Gonna see if I can find someone with a programmer and tune it in.
    “I ask, sir, what is the militia? It is the whole people, except for a few public officials.”- George Mason
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