Do I need upgraded injectors?

[XJ_Rudolph]

I would still recommend the wideband O2 because you are increasing engine displacement and that can upset AFRs, and you need to make sure you are not leaning out.

Also, make sure you reset your ECU!!! I forgot where I read it, but there are certain steps you have to take to reset your ECU "memory". Basically the first 100 miles you drive the car the ECU "learns" how the engine responds and what the driver drives like and calibrates the ECU accordingly. With the stroked motor, the ecu needs to relearn how much fuel it needs to squirt to keep the O2 sensors happy.

Hope this helps, and i am subscribing to this thread now.

 

[nectarXJ]

I would still recommend the wideband O2 because you are increasing engine displacement and that can upset AFRs, and you need to make sure you are not leaning out.

So, are you saying that the stock o2 sensor(s) won't provide the range needed for the ECU to learn the new performance characteristics?

Also, make sure you reset your ECU!!! I forgot where I read it, but there are certain steps you have to take to reset your ECU "memory". Basically the first 100 miles you drive the car the ECU "learns" how the engine responds and what the driver drives like and calibrates the ECU accordingly. With the stroked motor, the ecu needs to relearn how much fuel it needs to squirt to keep the O2 sensors happy.

Ah, now that I read from the link you gave me the other day:

Taken from https://thexjguys.wordpress.com/2012/12/31/xj-4-0l-fuel-injector-swap/

Resetting the PCM:

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the battery terminals and touch them together for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.)

Reconnect the Battery Cables

Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”

The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

You will run a little rich until the PCM adjusts for the new air/fuel mix.

So, possible updated to-do list:

1. ditch the existing chip
2. Stroke engine to 4.5
3. install wideband o2 sensor(s) (still wondering if I'm okay to not do this)
4. new 4 hole injectors*
5. Take selfie of smile on face on first test drive.

 

[XJ_Rudolph]

Install the wideband O2 so that you can see whats going on, not for the ecu. The stock O2 sensors basically only return a yes or no to the ecu saying that yes it is at the correct AFR or no its not at the correct AFR, which is why you cant hook up a gauge to the stock ones. Basically put in an extra bung in your exhaust (pre cat i think?) and put in your wideband and hook it up to a gauge on your dash so that you can see how the motor is doing.

 

[nectarXJ]

Oh okay.

I think I have two pre-cat o2 sensors since I have the two cat's up by the manifold. I'll take a look tonight when I get home.

Also, I found some wideband o2 sensors online that seems like they have "pass through" hook ups on the gauge (if I'm reading the info correctly - can anyone comment that actually knows?).

So I figured that if I did this then I could just replace both my pre-cat stock sensors with wideband o2 sensors. I'd have to have two gauges (or a double gauge I guess), one for each sensor. Then the ECU connections would be wired to these "pass through" hookups on the gauges. That actually seems pretty useful if indeed that is what they are for.

 

[cal]

I don't know that you would need to do 2 of them, those wideband o2 sensors are not cheap.

 

[Johnnie Walker]

Since you have pre-cats, unless you decide to ditch them and go with a 91-99 exh. mani or header, I would weld a bung in the down pipe after the pre-cats.

 

[nectarXJ]

I don't know that you would need to do 2 of them, those wideband o2 sensors are not cheap.

You're right about them not being cheap.

Since you have pre-cats...I would weld a bung in the down pipe after the pre-cats.

Ah good point (why didn't I think of that!). :doh:


With my stroker build I'm still wondering if a wideband o2 sensor is really necessary. (4.5 stroker with swapped out crank and different pistons - keep stock 4.0 rods and top end but top end is new + 4 hole injectors instead of stock 1 hole injectors).

I understand that having the wideband o2 sensor and a gauge lets me see the AFR (plus I like nerdy cool looking gauges) but with out any means to adjust the MAP there is nothing I can do change the AFR anyway, right? (...well nothing that doesn't cost $$$).


So, I guess I'm looking for more clear feedback such as:

A. Your ECU will greatly benefit from a wideband o2 sensor and more accurately adapt to your new engine characteristics vs if you just kept the stock narrowband sensor. Regardless of swapping injectors, without a wideband sensor your build will seem to run fine but then someday in the near future you'll break down because it's been running way too lean (or rich) and because you broke <something-scary> it's gonna be $$$ to fix.

-- or --

B. Installing a wideband o2 sensor for your build is not really necessary especially since your top end is still stock and you're not adding any sort of boost. Just swap injectors and reset the ECU and you'll be fine (i.e. reasonably safe from frying the engine due to running too lean or rich).


So what's the general consensus, A or B? ...Or chime in with an option C if I'm missing something here.

 

[XJ_Rudolph]

Hmmmm
I dont think the ecu would be able to benefit from a wideband, you would be the one benefitting because you have more information about what is going on.

Unfortuently i cant comment on A or B any more since i use to deal with forced induction mostly. We need a muscle car guy to answer those questions for ya

 

[Talyn]

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)

Not really correct. The PCM will keep the AFR around 14.7:1 in closed loop, which most all EFI vehicles do. When in open loop (warm up, accell, etc) it will richen the mixture to around 12.5:1 or so. No map adjuster will change the closed loop operation.

As far as using the wideband output to the PCM it usually won't work. Widebands operate on a 0-5v output. Narrow bands (stock) operate on 0-1v. The gauge output on a wideband will not work with the PCM input. However, there are a few that emeluate a narrow band output, and they do state that. But there aren't many.

Monitoring both banks would be good from a safety stand point. However, with either a simple MAP adjuster or more complex piggy back you will be only adjusting the entire bank (1-6 cylinders). Perosnally I wouldn't go with a simple map adjuster unless you are trying to stay cheap. They adjust the AFR in only open loop and only at a fixed point. However, they also mess with the timing in closed and open loop.

 

[Talyn]

A. Your ECU will greatly benefit from a wideband o2 sensor and more accurately adapt to your new engine characteristics vs if you just kept the stock narrowband sensor.

The PCM would have no idea what to do with a wideband sensor.

Regardless of swapping injectors, without a wideband sensor your build will seem to run fine but then someday in the near future you'll break down because it's been running way too lean (or rich) and because you broke <something-scary> it's gonna be $$$ to fix.

Changing displacement, and injectors you will have no idea what your AFR is without monitoring with a wideband.

B. Installing a wideband o2 sensor for your build is not really necessary especially since your top end is still stock and you're not adding any sort of boost. Just swap injectors and reset the ECU and you'll be fine (i.e. reasonably safe from frying the engine due to running too lean or rich).

While you might get away with just adding larger injectors (say the Neon 24lbs) you really won't know if its too rich or too lean.

There is a lot of misinformation in this thread and poor interpretations.

 

[nectarXJ]

While you might get away with just adding larger injectors (say the Neon 24lbs) you really won't know if its too rich or too lean.

I was planning on installing the 4 hole Bosch injectors (part number 0280155784). From what I understand they are basically the same as the OEM injectors but have 4 holes instead of 1. What do you think about those?

There is a lot of misinformation in this thread and poor interpretations.

Thanks for chiming in. I am in no way an expert at this stuff so I really appreciate any corrections and additional info that can be contributed. PLEASE set me straight where you can. I really want this build to work well.

I have almost everything figured out (or purchased) for this build. The only thing I'm still trying to figure out is all this business about the o2 sensors and any other tuning parts and / or procedures.

I'll most likely install the 0280155784 injectors.

It seems like a wise choice to also install a wideband o2 sensor (in addition to the stock narrowband sensor) so I can keep an eye on the AFR.

So the question I'm still asking is if AFR is off then what exactly do I do about it??

 

[Talyn]

I was planning on installing the 4 hole Bosch injectors (part number 0280155784). From what I understand they are basically the same as the OEM injectors but have 4 holes instead of 1. What do you think about those?

They aren't the same as stock. They are a 24lb/hr injector on the 49 psi rail. I run them on my 4.6L stroker. They will be plenty for you.

I have almost everything figured out (or purchased) for this build. The only thing I'm still trying to figure out is all this business about the o2 sensors and any other tuning parts and / or procedures.

Get a wideband and the 784 injectors and go from there. I recommend a wideband with data logging so you don't have to watch it while driving.

So the question I'm still asking is if AFR is off then what exactly do I do about it??

You have a few options. 1) PCM tune from the likes of christuned, 2) simple map sensor adjuster, 3) more advanced MAP adjuster like the Apexi SAFCII (more points to adjust), 4) A piggy back like the AEM FIC6 that intercepts and directly controls the injectors

 

[nectarXJ]

They aren't the same as stock. They are a 24lb/hr injector on the 49 psi rail. I run them on my 4.6L stroker. They will be plenty for you.

Get a wideband and the 784 injectors and go from there. I recommend a wideband with data logging so you don't have to watch it while driving

Okay, that's settled then, I'll move in that direction.

You have a few options. 1) PCM tune from the likes of christuned, 2) simple map sensor adjuster, 3) more advanced MAP adjuster like the Apexi SAFCII (more points to adjust), 4) A piggy back like the AEM FIC6 that intercepts and directly controls the injectors

Regarding option 1, I suppose I'd just contact Chris once I get this build running with the injectors and the wideband.

As for option 2, earlier in this thread I posted a PM from Dr. Dyno about a simple MAP adjust and he said it "...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." Mine is a 2001. Do you have a second opinion?

Haven't yet read much about option 3.

Option 4 looked really good to me until the PM exchange I had with boostwerks.com (earlier in this thread). He said "The AEM wouldn't really be very advantageous as you wouldn't be able to advance timing." Any second opinions on this response?

Thanks.

 

[XJ_Rudolph]

If you are going with totally different injectors, you really need some sort of protune. The ecu will have no idea what the latency of the injector is and will be pulsing at the wrong time.

"Injector "lag" time is the time it takes for an injector to open (OT) form the time it has been energized until it is fully open. There is also a close time that you do not hear about very often (CT). Some engine managment systems require you to enter this time and refer to it as injector lag, latency, delay or other terms. Although the times can vary slightly, the following chart should give you a good starting point. We will not be held responsible for any misinformation contained on these pages." http://injector-rehab.com/shop/lag.html

Every injector model has a different latency, which is why you need a tune to tell the ecu when to start energizing the coils and when to stop.

 

[cal]

If you are going with totally different injectors, you really need some sort of protune. The ecu will have no idea what the latency of the injector is and will be pulsing at the wrong time.

"Injector "lag" time is the time it takes for an injector to open (OT) form the time it has been energized until it is fully open. There is also a close time that you do not hear about very often (CT). Some engine managment systems require you to enter this time and refer to it as injector lag, latency, delay or other terms. Although the times can vary slightly, the following chart should give you a good starting point. We will not be held responsible for any misinformation contained on these pages." http://injector-rehab.com/shop/lag.html

Every injector model has a different latency, which is why you need a tune to tell the ecu when to start energizing the coils and when to stop.

Do you have specs on the stock jeep injectors for reference?

 

[XJ_Rudolph]

Do you have specs on the stock jeep injectors for reference?

I will do some research right now and try to find it

 

[cal]

You had me ready to go buy new injectors for the team naxja car right now

 

[XJ_Rudolph]

Alright guys I did some digging...but no website seems to have the detailed specs on these injectors.
BUT the good news is I found this cool website that shows you the injectors you can run on a stroker build!!
"For stock/modified 4.0 engines or stroker build-ups the following injectors can be installed. The flow rates are:

Ford Motorsport 19.0lb/hr @ 39psi (Part no. FMS-M9593-C302)
Ford Motorsport 24.0lb/hr @ 39psi (Part no. FMS-M9593-A302)
Ford Motorsport 30.0lb/hr @ 39psi (Part no. FMS-M9593-B302)
Chevy LT1 24.0lb/hr @ 43.5psi (Part no. 17124248)
Chevy LT4 28.0lb/hr @ 43.5psi (Part no. 17124251)
'98 Chevy LS1 25.2lb/hr @ 58.0psi (Part no. 12533952)
'99-'00 Chevy LS1 26.2lb/hr @ 58.0psi (Part no. 12456154)
'01-'02 Chevy LS1/LS6 28.6lb/hr @ 58.0psi (Part no. 12482704)
Accel 19.2lb/hr @ 44.1psi (ACC-150119)
Accel 21.1lb/hr @ 44.1psi (ACC-150121)
Accel 24.4lb/hr @ 44.1psi (ACC-150124)
Accel 25.6lb/hr @ 44.1psi (ACC-150126)
Accel 29.4lb/hr @ 44.1psi (ACC-150130)"
http://www.jeep4.0performance.4mg.com/tech_specs.html
Looks like someone already did the research on the latencies and found the ones that are close enough that the ECU can adjust for it.

READ THIS FORMULA: 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)
(also from website stated above)

I forgot to mention this above, but even your 6 injectors currently in your 4L all have slightly different latencies, but the ECU can correct for the minor differences. When you put in an injector with too different of a latency, it will try to correct but it might not be successful, and can lead to burning rich or lean. On a forced induction car, this could lead to predetination and total the inside of your motor.

 

[Talyn]

Looks like someone already did the research on the latencies and found the ones that are close enough that the ECU can adjust for it.

No research into latency there. It is based on flow rate & impedance. Latency is rarely mentioned because, as you found, its very difficult to find real numbers. I know one of the tuners doesn't do anything with latency and I don't know about the other one.

That formula is a little too generic to work for our application. According to it most strokers should be running 26+ lb/hr injectors, which are not needed. I have seen it other places and I think its more designed for a stand alone or ground up PCM build.

 

[XJ_Rudolph]

No research into latency there. It is based on flow rate & impedance. Latency is rarely mentioned because, as you found, its very difficult to find real numbers. I know one of the tuners doesn't do anything with latency and I don't know about the other one.

Yea there are no number on there site, but they could have done the latency research and only posted the injectors with similar latencies. But I could be wrong in believing that they did that. I would recommend the OP to go off of your advice since it looks like you have done this before. Iv only had experience with injectors and limited knowledge on tuning since iv never tuned a car myself, just read a lot into it.