12 hole fuel injectors jeep 4.0

4 hole vs 12 hole Injectors

I'm thinking about getting the 12 hole injectors from Ksuspension and was wondering if anyone has installed them. My question is was there any difference in performance by changing them? I have 4 hole injectors now but she idles a little rough and I'm trying to find a way to smooth it out a bit. The claim of better atomization sounds like a solid point and might help along with better mileage but my searches always come up with mixed outcomes. Some threads say it makes a huge difference and others say it's pure snake oil. Any input would be much appreciated.

Re: 4 hole vs 12 hole Injectors

Well seeing as factory injectors are 1 hole, your 4 hole injectors are only 3 better. But the 12 holes are 8 better than what you have now. That's 11 better!

Seriously, don't bother. You already have an atomization upgrade. Your idle issues are a maintenance problem. These motors idle just fine with OEM injectors.

Re: 4 hole vs 12 hole Injectors

Make your own 20 holes, more is better.

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Re: 4 hole vs 12 hole Injectors

Also, Ksuspension has a horrible track record specially from selling crap chinese injectors!

Re: 4 hole vs 12 hole Injectors

Multihole injectors can provide improved fuel atomization, but it depends on the circumstances. I was told by a Jeep engineer that the 4L motor is designed so that the factory single hole injector shoots fuel right to the back of the intake valve which also is an effective means of atomization. He recommended against multihole injectors on the 4L. Another reason to not go with an aftermarket injector is that an aftermarket injector is likely to have a different injection latency value which affects low engine load performance. In general, the injector characteristics (latency, flow rate, and sometimes partial opening flow rate and intake runner wall wetting behavior) need to be input into the ECU for the injector to provide optimum drivability. There are endless discussions about injector tuning in the street performance vehicle forums.

Re: 4 hole vs 12 hole Injectors

Quote:

Originally Posted by maxbraketorque

Multihole injectors can provide improved fuel atomization, but it depends on the circumstances. I was told by a Jeep engineer that the 4L motor is designed so that the factory single hole injector shoots fuel right to the back of the intake valve which also is an effective means of atomization. He recommended against multihole injectors on the 4L. Another reason to not go with an aftermarket injector is that an aftermarket injector is likely to have a different injection latency value which affects low engine load performance. In general, the injector characteristics (latency, flow rate, and sometimes partial opening flow rate and intake runner wall wetting behavior) need to be input into the ECU for the injector to provide optimum drivability. There are endless discussions about injector tuning in the street performance vehicle forums.

I know it gets annoying on these forums and I apologize for beating this dead horse, I just needed to ask. I replaced the injectors because they were in a bad way when I bought the Jeep. At the time I was new to the XJ world and it seemed like a good upgrade. After a few years of owning this thing and hours of reading forums and websites the more my eyes have been opened to some of the snake oil out there. The rough idle I have may in fact be just the way a 4.0 idles. The motor is brand new and every sensor has been replaced with OEM replacements.

Re: 4 hole vs 12 hole Injectors

The Jeep in-line 6 cylinder engines have never been known for their smooth idle. You should sit in my CJ-7 for a ride and a bit of idling at a stop light.

My 1998 has 284,000 miles and the original injectors. It runs great, idles funky, never stalls, and it gets good gas mpg's. If it doesn't stall at idle, it is fine.

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Quote:

Originally Posted by bimmerjeeper

Go ahead and slam the liftgate down on a blanket, and see how long you are laughing.

Re: 4 hole vs 12 hole Injectors

I do have 12 holes in two XJs, a '98 and an '00. I also had Ford 4 holes in the '98. Also, had another '98 with 4 holes. On both '98's the 4 holes did not seem to add any power by the but dyno. The engine did seem to run smoother. I also, did not see any MPG increase.
On the '98 that I changed to the 12 holes from 4 holes, it was running rough. I mean really rough, and down on power. When I changed to the 12 hole, the power increased. I mean noticeably. Then it kept getting less and less. After a week, it was back to as before. I did replace the spark plugs. I had Champion Truck plugs and replaced them with NGK. Or I might have used some new Champion Truck plugs. The '98 ran about as stock.
A guy who I have do work that I can't handle, mainly welding, also said he had the same experience. He racked it up to poor quality of Chinese stuff. I bought one of my 12 hole sets from Cobra Marty. The other off of EBay. I also wonder if the ECM is adjusting parameters back to 'stock'. ???
On my '00, I was battling to get it to start. The plastic case of the stock injectors were cracked. So, I used some 12 holes off of EBay. It runs about stock. I did run the engine several times before driving it. So, I would not have noticed if it gave more power and then adjusted back to stock.
Also, there is more to injectors than the number of holes. Some say the Neon Injector has an 'Advance' hole shape, with its single injector.
As stated before there is the impedance and also the rated pressure for injectors. So, I wonder about having the EMC reprogrammed and the fuel pressure increased. I am going to try that possibly latter in the year on my '00.
I would also check your plugs. I'd probably go with NGK. Did you change the O2 sensor? With NTK or MOPAR? I did change mine with a Denso. The one replaced looked rough. Also, I don't think it was tightened in correctly, or a bit lose. Still, I saw no real improvement. I do have an intermittent miss. I do have NTK O2 sensors to put in.
Don't know if any of that helps.

Re: 4 hole vs 12 hole Injectors

Quote:

Originally Posted by boneheded

I know it gets annoying on these forums and I apologize for beating this dead horse, I just needed to ask. I replaced the injectors because they were in a bad way when I bought the Jeep. At the time I was new to the XJ world and it seemed like a good upgrade. After a few years of owning this thing and hours of reading forums and websites the more my eyes have been opened to some of the snake oil out there. The rough idle I have may in fact be just the way a 4.0 idles. The motor is brand new and every sensor has been replaced with OEM replacements.

I'm puzzled by the rough idle thing. My 2000 XJ idles very smoothly, but I have gone through and replaced quite a few things on the motor. However, I haven't touched the injectors. Having said that, I'd recommend to anyone with rough idle or rough running to have their factory injectors cleaned and tested. I have a cleaned and flow matched set of stock injectors sitting on my bench waiting for the day when I feel like trying an injector swap. I also recommend looking at the plugs and consider trying a coil replacement. Those are easier than an injector swap, so I'd try those first, unless there are obvious issues with the injectors such as a leaking injector which typically causes hard warm-hot engine start.

Re: 4 hole vs 12 hole Injectors

I'd also suspect the TB. There are seals around the shaft. Maybe some air is getting around them. Others could be an exhaust leak, or even the temp sensor. Or other vacuum leaks.

Re: 4 hole vs 12 hole Injectors

I'd also check the cap and rotor. Also plug wires and the coil.

Re: 4 hole vs 12 hole Injectors

Some years back I switched to 4-hole injectors from a Ford. Didn't notice any real improvement but stuck with them for a few years. I did keep my old OEM injectors. Two years ago I was having trouble with a very rough idle and couldn't pass smog check. My #3 cylinder seemed to be the culprit. However it had good compression and strong spark. I ended up getting a "rebuild kit" for the OEM ones (basically new screens and o-rings), hooked them up, one by one, to a battery, sprayed TB cleaner through them all and put them back in.

It didn't fix #3 which turned out to be a wiring issue but I left them in. After some other tweaks, I passed smog.

Bottom line, with my stock motor, I still didn't notice any performance change going from 1 to 4 then back to 1.

Mine has a funky idle (varies rpm a bit) but runs smooth as soon as I boot it.

YMMV

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Re: 4 hole vs 12 hole Injectors

I went from my stock 1 hole injectors in my 91 to the 12 hole injectors from KSuspension, and I couldn't believe the difference. Way more power. Way, way more power. Better idle and quicker starts, too. I probably had some issues with my original injectors, so even just getting new 1-holes would probably have been an improvement. But holy crap, the difference was crazy! Money well spent (for me, anyway).