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A recurring question we face here at PHP is “why is FICM tuning needed if I have a PCM tune?”

I feel to properly answer that question, you have to first understand the way the PCM and FICM work together to determine the fuel pulse width.

To start, the FICM (Fuel Injection Control Module) is the deciding factor to determine injector pulse width. The FICM will determine the inj PW based off three primary values from the PCM. Those three input values are:

1. Engine RPM
2. Injection Control Pressure (ICP)
3. Mass Fuel Desired (MFD)​

To explain how each of these values correspond to the PW, I will try to break down the logic behind why these three values are important.

Engine RPM is used to determine how many milliseconds the injectors are open. At lower engine RPM, the piston is traveling at a slower speed. Each injection cycle is constrained mechanically by the piston location. As the piston is traveling towards TDC, the injection will begin around 15 degrees TDC. If the start of injection occurs any sooner, you risk over stressing the rods causing engine malfunction. The end of injection will be around 30 degrees. If you exceed this piston location in the cylinder, you will risk “washing the cylinder walls”.

The slower the engine is turning, it will take a greater amount of time for the piston to go from point A (15 degrees pre TDC) to point B ( 30 degrees post TDC). This is often referred to as the injection window.
These are arbitrary numbers for proof of concept.

Injection Control Pressure (ICP) is used to determine fuel quantity in a given window. The way I often explain how ICP affects the injection system is to use an analogy. Thing of an injector as your generic spray bottle. If you squeeze the trigger slowly, you will get less fluid to come out of the nozzle than if you squeeze the trigger hard. The HEUI fuel injector operates much like this. If the ICP is low during the injection cycle, you will not get as much fuel from the injector nozzle. If the ICP is high, the injector nozzle will disperse more fuel into the cylinder.

For this reason, the injector PW operates inversely from the ICP. If the injector pressure rises, it will cause more fuel to come out in a given period of time. With low injection pressure, the amount of fuel in that same period of time will be less. Because of this, injector pulse width will expand at lower RPM to attempt to achieve a target amount of fuel. If the injection pressure is high, the injector PW will reduce to attempt to hit that same target amount of fuel.

The PCM measures ICP based off values from MFD and Engine RPM.

Mass Fuel Desired is used to help facilitate what the target amount of fuel is. The PCM measures MFD by calculating between the accelerator pedal position and engine RPM. With the desired outcome of MFD being the amount of fuel, this is measured in mg per stroke.

Spoofing The ICP: With the FICM taking these three values to ultimately calculate the PW, a lot of PCM tuners have taken to “spoofing the ICP”. What spoofing does is to trick the truck even though it is making 4,000 psi ICP, the PCM interprets the psi as actually 2,000 psi ICP.

As mentioned above under ICP, if the truck has less ICP, it will naturally expand the PW to hit the target amount of fuel.

Since we are actually producing 4,000 psi ICP (not the 2,000 psi the PCM thinks) we now have an expanded PW while having full ICP. This is where FICM tuning comes into benefit. Since “spoofing the ICP” is not a precise way to increase PW, FICM tuning steps in to take over.

The ICP spoof only occurs over a set ICP value. On average, tuners begin to spoof the ICP around 2,000 actual psi to 3,000 actual psi. So when you are driving around town at light throttle, there is very little fuel modification via injection PW. That is because the PCM tuning and spoofing the ICP simply cannot work in that situation. When tuners do attempt to spoof the ICP too soon, that is what will cause the ‘light switch effect’ in the way the truck fuels.


Since the FICM is the deciding factor in how the injector fuels the truck, wouldn’t it make sense to tune the actual fuel maps opposed to ‘spoofing’ aka faking values?

This is exactly why FICM tuning is needed in addition to a PCM tune for the truck to run in optimal form.

FICM tuning is able to help your truck achieve better off idle throttle response, increased fuel mileage and more power / torque in the areas that PCM tuning simply cannot achieve on the 6.0 platform due to design.

If yall have any questions, please post them below or call out shop at 678-890-1110

Written by: Jay Chatham from Power Hungry Performance
 

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Great write up thanks, now I can spend even more money on my truck :wink[3]:
Now if one of the mods would make it a sticky.... @Rattlesnake18
 
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I have been sold on FICM tuning since long ago, but I have a greater appreciation for it after this great explanation!! Thank you


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Great info, thanks! Does an existing custom PCM tune need to be altered after the FICM tuning? For here in Commifornia, how does a FICM tune effect smog testing?
 

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Great info, thanks! Does an existing custom PCM tune need to be altered after the FICM tuning? For here in Commifornia, how does a FICM tune effect smog testing?
Whether or not the two can be stacked or are synergistic with each other is a murky concept. Both are essentially independent computers right? The PCM tunes from some writers pair well with a FICM tune and others do not. Gearhead for example does not recommend anything bigger than the Atlas40. Ideally, I would think you would want to do FICM tuning first and then let the writer of the PCM tune know what you're running. Or, it might make no difference at all but it sure appears that at least with regards to fueling both are trying to do the same thing but ultimately the FICM has all the control.

That is an awesome write-up Jay. Correct me if I'm wrong in the above assertion but going back a year or two there was a thread on the org as well as army and FTE regarding the same issue. Mainly with GHP tunes but at least one other tune writer I talked to wasn't that keen on FICM tuning paired with his PCM tunes. Presumably because they're trying to fool the ICP sensor but besides light bulb effect the issue ends up being funky shifting.
 

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Funny , when ever I order tunes from anybody and tell them that I have a FICM tuner , there is never a mention about which FICM setting is recommended ( or not ) .
Seeing as their so overlapping shouldn't it be a necessary input from the tuners .
I would imagine that all the tuners know what the " sweet spot " is for their tunes .
 

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I think an answer blaming the FICM is an easy way out for an unsolvable tune issue. :dunno:

I run tunes on both with zero issue.
 

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Discussion Starter #10
The FICM tunes add more PW on the big end. If the PCM tune is already pushed out pretty far, the FICM tune will push the PW out even further than that.

This is why companies like Gearhead recommend only the ATLAS 40. This is because the Atlas40 will boost up the bottom end performance without over doing it on the top half(when paired with their tune)
 

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Funny, whenever I see the term PW I think of the Pussy Wagon in Kill Bill:grin:

Anyhow, basically what you are saying by adding more PW is that FICM tuning adds more fuel (thus prolonging the burn) after the piston reaches TDC rather than before (which would increase cylinder head pressure).

But what is not clear here with regard to stacking FICM tuning is what PCM strategy the tuners like to tweak. You guys at PHP have already gone to great lengths to show the power differences of different strategies with empirical data. Some strategies have better fueling than others right? For example, VXCF4 and VXCF9. However, the strategies that make better power may not pair well with FICM tuning because they end up very smokey, run hot, w/ decreased mileage. I read in another forum wrt ficm tuning that this is why some tuners prefer a strategy that does not excel at fueling (compared to others) so they end up less smokey and make better and cleaner power. Isn't that one of the reasons why PHP prefers to roll back later model 6.0s to VXCF4? Besides of course EBP and vane control.
 

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Discussion Starter #12
Isn't that one of the reasons why PHP prefers to roll back later model 6.0s to VXCF4? Besides of course EBP and vane control.
EBP function and vane control are the main reasons we use VXCF4 opposed to VXCF9. On NonVGT setups, I like to run VXCF7.

Any tuner can build great power using any of the strategies. It is just the small differences like the way the transmission handles the shifts, vane sweep, inferred EBP, etc.

We (as tuners) just have a bias for which base strategy we like most. Then we expand on that base strategy to develop various power levels / shifting schedules.

_____

Yes, adding a larger FICM tune will allow the injector to stay open longer. It does not advance the start of injection. It just delays the end of injection.
 

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When running a FICM tune with custom SCT tune, what should be considered excessive pulse width?

Also, at what point does the more aggressive FICM tune make no difference vs less aggressive FICM tune. For example, a race tune and running Hercules FICM tune, vs race tune and Atlas 40. Or a Mild street tune with Hercules vs Mild street tune with Atlas 40?
 

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Ok...my head is really spinning now. For instance in my case also being a resident of the Peoples Republic on the west coast, who has a "relatively stock truck that tows heavy frequently is this important to me if I want my studded truck with stock turbo and injectors and a mild tune to perform the best it can. Small increases in power/torque is important to me but I want my truck to run as clean as possible. I have finally really learned to love my rig and what it is capable of after moving from my tow monster Cummins powered you-know-what's and want to get as much clean power as reasonable without affecting reliability AND being able to go back to a Cali passable emissions test. Probably a silly question but you know about those that do not get asked. Is this important to me?
 

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I'll pass along my observations, I've been running an FICM file with SCT tunes for about 2 years now.

When running a FICM tune with custom SCT tune, what should be considered excessive pulse width?

Also, at what point does the more aggressive FICM tune make no difference vs less aggressive FICM tune. For example, a race tune and running Hercules FICM tune, vs race tune and Atlas 40. Or a Mild street tune with Hercules vs Mild street tune with Atlas 40?
Excessive pulse width for most of us would be the point where 1) the truck is simply too hot and smokey for your driving style, or 2) you have indications of cavitation of your fuel injectors. (That is where the capactiy of your injector is depleted by the oversized nozzle before the injection cycle ends and your plunger is striking the injector body.)

Running heavy FICM files with any SCT tune as to where the FICM vs. SCT gains are made is always going to be a case-by-case basis. I don't run PHP's FICM Files, but I've seen trucks that do. The heavier the FICM tune, the hotter smokier and lopier the truck seems to run - reason for this in most cases is the SCT file isn't dialed in to tune the transmission, injectors, and VGT to account for it. To really determine the line where the aggressive FICM tuning is muddled by the SCT files, you'd really need to see some form of study (best if it is conducted on a dyno) where a comparable SCT (defined that way so that the SCT specific file for the FICM tune compared is adjusted to maximize the benefit) file is run at each level of performance. Unfortunately I haven't seen any such dedicated comparison.

From the base line SCT files I have experience with, PHPs Atlas40 or IDPs Performance files seem to be that level where the whole truck really comes alive and runs great and still allows you to tow, DD, and still get wild with it. Most of the more aggressive files seem to be better suited to the track.

Ok...my head is really spinning now. For instance in my case also being a resident of the Peoples Republic on the west coast, who has a "relatively stock truck that tows heavy frequently is this important to me if I want my studded truck with stock turbo and injectors and a mild tune to perform the best it can. Small increases in power/torque is important to me but I want my truck to run as clean as possible. I have finally really learned to love my rig and what it is capable of after moving from my tow monster Cummins powered you-know-what's and want to get as much clean power as reasonable without affecting reliability AND being able to go back to a Cali passable emissions test. Probably a silly question but you know about those that do not get asked. Is this important to me?
You'll need to get one of the portable tuners, and not simply ship yours off for a permanent file this will allow you to drop back to stock or near stock and clear any soft CELs prior to inspection. What I see, and why I run FICM tuning in the first place, is the gains made by the FICM tuning low in RPM band. Towing, turbo spooling, fuel economy even at the stock PCM level all seem to appreciate the gains made by the lower powered FICM files (say +40HP and below).
 

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My experience with FICM tunes has been nothing but great!

I run about 3 different tunes depending on what I am doing. With those tunes I change my FICM tune around as well.
For example With my gearhead SRL++ tune (race,having fun) ill run either the 40 or hercules depending on what I am doing. When I am just around town I will run 40 just to give me a jump in low end and fuel mileage. When I know im gonna be racing ill run the hercules tune.... (some may recommend you dont) however I have noticed that when I take it easy I actually have lower EGTS with the hercules. Now with that being said if I get into it at all my EGTS will get hot, but nothing that isnt managable.

With gearheads 8k tow tune I will run either the 40 or economy tune, depending on the heat outside. Both are very manageable while towing a 16 foot enclosed lawncare trailer. I just change it for my own sanity.

With my WPE white rain tune (power but wayyyy better fuel mileage) I only run the 40 tune because white rain has low end power like no other, so the larger FICM tunes are not needed down low.

I hope this helps someone down the road, im not saying im right by any means just what my personal experience has been the past 2 years
 

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Ok...my head is really spinning now. For instance in my case also being a resident of the Peoples Republic on the west coast, who has a "relatively stock truck that tows heavy frequently is this important to me if I want my studded truck with stock turbo and injectors and a mild tune to perform the best it can. Small increases in power/torque is important to me but I want my truck to run as clean as possible. I have finally really learned to love my rig and what it is capable of after moving from my tow monster Cummins powered you-know-what's and want to get as much clean power as reasonable without affecting reliability AND being able to go back to a Cali passable emissions test. Probably a silly question but you know about those that do not get asked. Is this important to me?
I agree with the head spinning :crazy: This is a great write up and thanks for making it more easily understandable.

I'm currently running the SRL+ and until my truck gets to operating temps it likes to smoke a little after I pull out from a stop. I'm assuming a ficm tune would help fix this if not completely? There seems to be so many different possibilities from the tuning I'm not exactly what to run. I would really like to get the white smoke gone but at the same time cannot afford to send out my ficm to get it tuned. That and also plan to upgrade my sticks and turbo in the unforeseeable future. Not sure if it would be worth it do get a specific tune for the ficm now, then again with the upgrades until I get it all together.

Why hasn't there been a standalone module made to plug into the ficm connectors to tune it? Does the actual circuit board need to be altered?
 

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A FICM tuner plugs into the OBD port and in less than one minute, you have changed the FICM tune.


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I agree with the head spinning :crazy: This is a great write up and thanks for making it more easily understandable.

I'm currently running the SRL+ and until my truck gets to operating temps it likes to smoke a little after I pull out from a stop. I'm assuming a ficm tune would help fix this if not completely? There seems to be so many different possibilities from the tuning I'm not exactly what to run. I would really like to get the white smoke gone but at the same time cannot afford to send out my ficm to get it tuned. That and also plan to upgrade my sticks and turbo in the unforeseeable future. Not sure if it would be worth it do get a specific tune for the ficm now, then again with the upgrades until I get it all together.

Why hasn't there been a standalone module made to plug into the ficm connectors to tune it? Does the actual circuit board need to be altered?
The FICM tune will help with low RPM power and spool the turbo better. The FICM tuners that I recommend PHP and IDP both have portable units. Right now I don't think IDP sell theirs, its just a rental by the website. PHP's programmer sounds like its the answer you need. You don't change the FICM turner programs when you do separate mods - all those files are the same. By tuning the FICM you open up more possibilities for your SCT files. The programmers run through the OBII port, you simply pull your FICM relay, tune, and reload your SCT files (the FICM is loaded first with your SCT tuned the truck to stock, then you reload your SCT files).

Personnaly, even if you didn't run an SCT tuner, I'd run a mild FICM tune to simply help spool the turbo.
 

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Great write up. When i changed my injectors I had a funny idle. I did research and found that a FICM tune was in order and should correct the issue. I found a PHP tuner locally and updated my strategy to the Atlas 40, loved it. Ive since switched to the economy tune and love it even more. I dont run a PCM tuner or have upgraded turbo and thought this was a better option for my truck. Best thing ive done to the truck and couldnt be happier
 
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