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Do I need upgraded injectors?

nectarXJ

NAXJA Forum User
Location
Utah
My 2001 developed a loud knock (bottom end) so I'm rebuilding it to a 4.5 (top end remains stock but new) and all new cooling. The previous owner had an Edge Trail Jammer chip / kit installed which remains in place today.

So I guess my questions are:

1. How do I determine if upgraded injectors are a good idea for this stroker build?

2. Is this installed chip helpful, harmful, or doesn't matter for the stroker build?

3. Could the chip somehow have contributed to the development of the knock?

Any experience, opinions or advice would be helpful.

Thanks!


Addition rig specs (incase this is helpful):
- 35 inch tires
- 4.56 gears
- snorkle (I'm wondering how well a jeep can really breathe through these)
- some sort of throttle body spacer
- K&N air filter
- stock auto-trans
- stock transfer case
 
1. How do I determine if upgraded injectors are a good idea for this stroker build?

Come on now don't be shy. :) If all you do is help with question number one that would be most helpful.
 
I would talk to Russ P. He's the man when it comes to stock or stroker builds. He should be able to point you in the right direction.
 
Last edited:
Awesome thanks!
 
The chip could be making your car run leaner. The leaner you run towards 14.7:1 air:fuel, the lambda of gasoline, the more power you will get. However, the leaner you run, the hotter the inside of your engine can get, which can lead to pre-detonation in the cylinders since the fuel is heating up beyond its flash point. This pre-detonation can lead to knock, and could bend push rods, break cylinder heads, cylinder rods, and cams. If somethings broken, it could continue to knock due to misfire in valve or timing.

I hope this is helpful!
 
The chip could be making your car run leaner. The leaner you run towards 14.7:1 air:fuel, the lambda of gasoline, the more power you will get. However, the leaner you run, the hotter the inside of your engine can get, which can lead to pre-detonation in the cylinders since the fuel is heating up beyond its flash point. This pre-detonation can lead to knock, and could bend push rods, break cylinder heads, cylinder rods, and cams. If somethings broken, it could continue to knock due to misfire in valve or timing.

Ah, funny you should mention all this. I had heat issues before eventually developing the loud knock in the bottom end (I suspect broken piston skirt).

So do you think it would be better to just remove the chip and fall back to stock for the stroker build?
 
Ah, funny you should mention all this. I had heat issues before eventually developing the loud knock in the bottom end (I suspect broken piston skirt).

So do you think it would be better to just remove the chip and fall back to stock for the stroker build?

A few things I would check first. I would recommend checking spark plugs to make sure they still look good, then pull out your injectors and make sure they don't look clogged.
Now some brief info on how chips work. Most chips (yours may be different), intercept data coming from sensors and modifying them based on huge 2D tables that are stored in the chip. Basically, it spoofs the engine to think that the AFRs, timing, and many other factors are different from what they actually are.

My advice would be do ditch the chip, and if you really want more power do some engine mods then get a manifold pressure turner (i think is what its called) and tune the manifold pressure yourself. They mention it in this article: http://www.fourwheeler.com/vehicle-reviews/131-0403-jeep-xj-cherokee-mileage/
 
Thanks for the advice. Sounds like I've got some things to check.

...then get a manifold pressure turner (i think is what its called) and tune the manifold pressure yourself. They mention it in this article: http://www.fourwheeler.com/vehicle-reviews/131-0403-jeep-xj-cherokee-mileage/

Thanks for the link. I'm assuming it's the "MAP (manifold absolute pressure) adjuster" mentioned in the article that you're talking about(?).

What am I looking to accomplish with this adjuster?

Thanks.
 
Thanks for the advice. Sounds like I've got some things to check.



Thanks for the link. I'm assuming it's the "MAP (manifold absolute pressure) adjuster" mentioned in the article that you're talking about(?).

What am I looking to accomplish with this adjuster?

Thanks.


Yes that is what i was talking about!! And it changes the air fuel ratios in the cylinders by changing how much air the engine sucks in, so you can adjust if you want to run lean or rich. I would only recommend that you run one if you can spend the time to get it dialed in. From what i have read, the 4L runs pretty rich from the factory, so it could give you some power boost if you get it dialed.

What I would do long before getting one of those though is changing out your injectors to the 4 hole instead of your stock 1 hole. You will get better power and better mpg. I think on ebay they run from 100-200 for a set of 6. There also should be some threads floating around here on what part# you need to look for for your year 4L, as well as detailed instructions.
 
Yes that is what i was talking about!! And it changes the air fuel ratios in the cylinders by changing how much air the engine sucks in, so you can adjust if you want to run lean or rich. I would only recommend that you run one if you can spend the time to get it dialed in. From what i have read, the 4L runs pretty rich from the factory, so it could give you some power boost if you get it dialed.

What I would do long before getting one of those though is changing out your injectors to the 4 hole instead of your stock 1 hole. You will get better power and better mpg. I think on ebay they run from 100-200 for a set of 6. There also should be some threads floating around here on what part# you need to look for for your year 4L, as well as detailed instructions.

Okay, so how's this for a list:

1. ditch the chip
2. Stroke engine to 4.5
3. MAP adjuster (to adjust fuel/air ratio)
4. wide band o2 sensor w/ dash gauge (to read fuel/air ratio)
5. new injectors*
6. tune so that I'm on the safe (rich) side of 14.7:1 air:fuel

Am I missing anything?


*Do you know if these injectors would work?
http://www.blueovalindustries.com/engine/fuel/en8810kit.html
They are 6 hole, 24# and have the EV6 connector. It's a set of 8 but I figure I could use the extra 2 as spares.
 
Okay, so how's this for a list:

1. ditch the chip
2. Stroke engine to 4.5
3. MAP adjuster (to adjust fuel/air ratio)
4. wide band o2 sensor w/ dash gauge (to read fuel/air ratio)
5. new injectors*
6. tune so that I'm on the safe (rich) side of 14.7:1 air:fuel

Am I missing anything?


*Do you know if these injectors would work?
http://www.blueovalindustries.com/engine/fuel/en8810kit.html
They are 6 hole, 24# and have the EV6 connector. It's a set of 8 but I figure I could use the extra 2 as spares.


Ok good you are going to be getting a wideband O2!! That will help a ton! I wish my old subaru had one of those...

I would stay away from other injectors besides the ones that have been proven to be a direct swap. Injectors are very tricky things to deal with. Basically, almost all injectors are different, the valves have different latencies and take different voltages, so when you try to put injectors from one car to another, you could be accidentally running the car too lean or too rich because of the valve latency or voltage. Just because they fit doesn't mean they will work 100%. A way around this is if you go to a tuning shop and get the ecu tuned to match the injectors you put in, but i dont know if anyone does that for jeeps. Check out this link for install instructions: https://thexjguys.wordpress.com/2012/12/31/xj-4-0l-fuel-injector-swap/

If you have a 87-98 engine, you will need the bosch part #0280155703
If you have the 99-01 it is bosch part #0280155784
Look up the part number on ebay and you will find a bunch of people selling them for the 4L in a 6pack.

From my understanding, the internals of these injectors are identical to your stock injectors, they just have a different valve plate that sprays 4 streams instead of 1.


Also, with your MAP adjuster you will be able to tune the AFRs your self since you will have a wideband O2 sensor.

And i would say for things you are missing...get a digital temp gauge for engine temp, much better than the analog one that comes stock. Also if you are wheeling a lot, get a tranny temperature gauge and an auxiliary tranny oil cooler. You can use any oil cooler for that (should be around 100-120$ new)
 
Dude you ROCK!! Thanks, this is exactly the direction and info I was really needing! I think I'm ready to pull the trigger on this stroker.

:party:
 
Dude you ROCK!! Thanks, this is exactly the direction and info I was really needing! I think I'm ready to pull the trigger on this stroker.

:party:

Thanks man! Do you have an Instagram for your build or a build thread here? Id love to follow it!
 
Just got your PM nectarXJ

Looks like XJ_Rudolph has ya going in the right direction with good info.

Good luck and keep us posted.
 
Thanks man! Do you have an Instagram for your build or a build thread here? Id love to follow it!

Sadly I don't have a build thread anywhere. I should probably start a thread showing pics and details of this stuff and all the past stuff I've done. I always enjoy reading those types of threads that others post. If / when I start one I'll post a link to it in this thread.

Cheers!
 
Iv got an edit here, 4L runs lean stock:
"The MAP (manifold absolute pressure) adjuster was the only part we put on that was not going to improve fuel economy. It provides adjustability of the fuel curve,therefore allowing you to run the engine richer or leaner. The MAP adjuster plugs in to the MAP sensor's harness and has a 12-volt wire which needs to be hooked up to a switched 12-volt power source. Once that is done, you can use a voltmeter to watch the voltage reading as you adjust the fuel curve with the turn of a screw built onto the unit. We curved our unit to give us a 5-volt reading from the MAP sensor. Cherokees are set to run lean from the factory, and we were going to increase spark efficiency with the Performance Distributors ignition kit, and therefore only saw the potential for a more complete combustion." -FourWheeler (http://www.fourwheeler.com/vehicle-reviews/131-0403-jeep-xj-cherokee-mileage/photo-05.html)
 
good catch.
 
Well I thought I was out of the woods with the MAP adjuster. Turns out it's not as easy as I thought for my 2001 XJ (was going to make my own). Check out this PM with Dr. Dyno:

Dr. Dyno said:
nectarXJ said:
Hi Dr. Dyno,

I was reading this thread:

http://www.naxja.org/forum/showthread.php?t=76062

and found your link about making your own MAP adjuster:

http://www.angelfire.com/my/fan/MAP_adjuster.html

Will this work on my 2001 XJ or is it limited to certain years of XJ's?

Thanks!

The MAP adjuster works best on Renix & OBD I XJs, fairly well on early OBD II from '96-'99, but doesn't really work on '00+ XJs with DIS and more finicky ECUs.


From what I can figure from other posts I guess I might need something more like the AEM 1913. Apparently I'm really late to this game since no one seems to be making a piggyback harness anymore to get this installed. Plus the AEM is like $400. Ouch! (much more than the $10 in parts to make my own MAP adjuster like in Dr. Dyno's link.)

So, I'm back to wondering if I really need to do all this. If I install the 4 hole Bosch injectors (part number #0280155784) and just had the stock ECU with no wideband o2 and no MAP adjuster would I be okay or would I totally fry my new stroker???
:wow:
 
Here's some more info from a PM to boostwerks.com (for anyone following this thread):

nectarXJ said:
Boostwerks.com said:
Honestly, slightly larger injectors might be the best swap to make. It will idle better, and under full load will have the correct fuel ratio without having to do any special tuning. This is what most people do with stroker builds anyways.

The AEM wouldn't really be very advantageous as you wouldn't be able to advance timing.

Hope that helps!
Bryson

nectarXJ said:
Just trying to decide if I need something like the AEM 1913 for my stroker. I'm about to rebuild my 2001 stock 4.0 to a 4.5 (new crank and pistons and all else stock but new). If I just do the build and use all stock stuff would this work or will I need different injectors, wideband o2, and something like the AEM 1913?

Thanks!

Ah excellent feedback thanks! So if I just swapped out the injectors for the bosch 4 hole injectors (part #0280155784) would that do what you are talking about?

I'll post his response when I get it.

So, my short list is now (so far):

1. ditch the existing chip
2. Stroke engine to 4.5
3. 6 new 4 hole injectors*
4. Take selfie of smile on face on first test drive.
:sunshine:


*bosch part #0280155703 (...made by eBay).
 
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