ISX CM2350 VGT & Brake Table

[Moose]

After looking at everything I guess I need to revise my question.

I can go in and change the tables, loosen them up as to not be so tight at idle and light load. BUT, something else has a final say over VGT commanded. I don't know what that is. The two cals are close in the upper limit table and it actually is set at 90%. I can go in, massage the table but am I just band-aid(ing) my problem? Forcing it by not allowing it to close as much as it "wants" to.

So, what makes it "want" to close so hard? The stock cal would open and close based on need, SCR temp control, active regen, etc. It could be as open as 20% at idle. Something is holding this at 82% no matter what until the mg/strk & RPM exceeds a threshold.


Rawse, I had no intention of modifying or increasing the brake tables but the seat of the pants sensor tells me that they aren't pulling down like they did before. Again, more meddling as they also lowered the upper limit VGT braking table over the stock cal. Between 5-10%

[Unilevers]

ooh someone getting serious about their cal....your in the deep end now!

just put the vgt position tables for engine braking back to stock. you really want the boost to peak at about 32-34 psi under full load jake. any higher and guys like it but its extremely hard on the engine and dropped valves are common.

what is controlling the VGT is MCF tables for different operating modes. The engine looks at sensor variables and load demand and decides how much Mass Charge Flow (physical amount of air) the engine needs and ramps the vgt to provide that aslong as its between its set operating limits. This varies greatly per mode the engine is in and sensor inputs aswell. if it wants 50 lbs/min and its only getting 30 its going to start ramping the hell of the vgt to max to speed the turbo up and push more air through until it hits its set operating limits. the engines are also set to have factory variable limits which mean it varies per Chi and alpha mode. this is why you see it trying to continually ramp up.

is its a common rail or a dual cam? its varies greatly and i have found stock cals for common rails are rich as hell in the idle regions and need to be compensated for - just food for thought.

[Moose]

Thank you for that answer.
It's a 2350 common rail.

The jake table is going to get returned to stock values.

Now after a de-mandate in a prior truck (CM871) I saw an immediate 1MPG gain just by the HC Doser injector not using anymore fuel. Further work & tuning yielded about a 1.5MPG total gain.

This CM2350 with the same de-mandate I'm losing about a MPG since. Something is not right. Some of the red flags of a crappy file are evident, but some things are dead on; Boost tops out at 35psi, shaft speeds are less than 120k under full throttle. Exhaust temps max out at 1100F at the k-probe pre-turbo and 1200F calculated. The turbo just seems like it trying to work entirely too hard and the fuel mileage is agreeing. I've got 5psi @ idle with 40k shaft speed 82% VGT, 10PSI at light throttle and then it drops off over 1100rpm. I want to fix this. I've got too much money and time in rebuilding this one. I don't want redneck tuning... I want it not to breathe it's own soot and last beyond 400k miles.

I'll pay more attention to the MCF and operating mode. Plus I can go back and look at the other cals now that I know what to look for. When you say that "stock cals for common rails are rich as hell in the idle regions and need to be compensated for" Does this vary from cal to cal, family to family? What i've learned even back in my days working for this maker is that they were poor idling engines and needed some load to smooth out but excessive idle load, if not for aftertreatment heating purposes, was compensating for a bad running condition or in this instance maybe, a piss poor tune?

But, If I cannot get this rectified, a stock engine with better fuel economy is going to be better than what I have now. I could have lived with a lateral move but a loss in mileage I cannot. I know it can do better...

Thanks again

[schISM]

(12-03-2017 )Moose Wrote:  Boost tops out at 35psi, shaft speeds are less than 120k under full throttle. Exhaust temps max out at 1100F at the k-probe pre-turbo and 1200F calculated. The turbo just seems like it trying to work entirely too hard and the fuel mileage is agreeing. I've got 5psi @ idle with 40k shaft speed 82% VGT, 10PSI at light throttle and then it drops off over 1100rpm. I want to fix this. I've got too much money and time in rebuilding this one. I don't want redneck tuning... I want it not to breathe it's own soot and last beyond 400k miles.

I'll pay more attention to the MCF and operating mode. Plus I can go back and look at the other cals now that I know what to look for.

Just thinking out loud, but it seems to me the turbo is operating exactly as it should utilizing MCF. Before low NoX was common terminology there was no reason to see more than 1000 degrees pre-turbo/800 post. I'd be inclined to look at SOI before messing with the turbo. If its only vectoring to one mode it may still be using a "protection" SOI that is too far retarded allowing your heat to go out the exhaust instead of drive the piston. I know these common rails can't take much timing advance I'm just saying thats where I would start.

[Rawze]

I disagree with the engine needing a load at idle. - The factory does this mainly only to speed up the warmup time of the engine and scr system. Take those systems away and there is no need to waste fuel like that unless your in extreme cold climates all the time.

It is not unusual to get an ISX to drop down all the way to about 11 or 12 mg/stroke fuel consumption at idle, down from 40 mg/stroke when it was factory programming. That is a huge saving in fuel if someone has to idle a lot. Every truck I have seen set like that idle perfectly fine and smooth unless there are worn out fuel components or injectors.


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Taking a step back ...

First of all, I would have the whole program looked at by someone like myself, Unilevers, and/or Gearhead to get a second opinion. If the turbo tables aren't quite right, then god only knows how many other systems are out of whack that may be yet unseen. Your welcome to e-mail the file to me and I can look at it for you when I get a few minutes. I PM'd you my number so you can call me and talk about it as well.

[Rawze]

Got a chance to see the file he had. It had been done by someone off another forum according to the truck owner, he did not say who specifically. Here are some things I did not quite agree with ...

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* The original factory file he had in his truck was from 2017. It looks like it was replaced by a much older file from maybe early 2013?. - CM2350 files that old have some known issues like injector instabilities and other small problems that got corrected a year later. The file that the person who used to do the delete also has settings in it for an older style of fuel pump with different coil resistances for the regulator. There have been a lot of updates on those fuel components since that file was made. It could potentially lead to erroneous errors with the fuel system if components like the regulator are replaced. Not sure I would have trusted a file that old if it were my truck and I have seen no need to use any file older than 2015 to prevent just these things.

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* Not sure if it was simply the really old file, or if someone purposefully edited it but the engines normal main high altitude operating mode was overridden. The mode that replaced it was high altitude thermal management mode. Also, this operating mode was altered heavily with things like 16% more fueling in places, modified injection timing maps that were as high as +12 degrees BTDC at high torque outputs (this could potentially damage the engine severely) and other things that just did not seem quite right.


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* Besides the one altered operating mode that will only be active above 4000 feet,... there was no correction of the turbocharger operation to compensate for the now vastly different exhaust and intake flow. This the most likely reason the guy was having trouble with it making 5+ psi of boost at idle. Its a typical mistake for someone who is re-programming the ecm to think that the factory programming can compensate for these kinds of changes on its own.

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* Same problem with the injection timing, fuel air ratio, oxygen fuel control, etc. of no compensation at all for the now missing/blocked EGR or the vastly more efficient exhaust flow. I guess the person does not know about the injection processes of the CM2350?. - Unsure,.. but here is a direct reference to the consequences of ignoring these things...
http://rawze.com/forums/showthread.php?t...8#pid15548


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* Not sure if it is the old out of date file, or if it was done purposefully but some of the fuel pump leakage detection during engine run time has been disabled. Not sure I agree with that one, as a leaky injector or relief valve would have to get pretty severe before a leak was detected.

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* cold ambient timing advance has been completely disabled. This easily makes for hard starts, rough idle, + heavy black smoke in very cold weather (below freezing) when the engine is first cranked, but hey, what do I know. I have seen my share of custom tuners struggle with this, as it is one of those systems that simply screws with all your hard work if you don't understand what it wants.


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* The engine is being told that it has to work up to 12% harder to make correct power output in the high altitude operating mode that has been overridden. Why so much effort was put into only one operating mode when there are 10 more to contend with?. I can see it if the engine was locked into this mode and you only drove the truck above 4,000 feet in elevation all the time, but it does not appear to be.

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* The engine brake upper limiting has been altered to weaken the overall engine brake operation by anywhere from 8% to as much as 16% in places in its mapping. I guess that is better than most of the bad deletes I have seen in the past where some moron tries to double it, causing engine damage. - Why not simply leave it alone?

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* The NOx allowance for the overridden engine mode is altered by a high margin and made to be more stringent. I.E> the engine will try to make even less emissions than the original factory file. It seems almost as if someone tried to make it more lenient, but went the wrong way with the table?

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- Other than that, not much else was touched. Overall, it is not a terrible program like I have seen some people do. it has the general appearance of maybe someone who simply does not know a whole lot about what to correct when the cans are axed + egr blocked off on a 2350. There was nothing done about the fall-back emissions that try to reduce NOx, PM, erg fraction, or anything else either. This results in unpredictable injection timing, fueling, altered turbo state and fuel air mix, and it effects power output and efficiency. Not sure about anyone else, but if I were having such mods done, I would want to know the outcome instead of guessing at it.

The engine is still capable of operating in the other 10 operating modes it has. Modes including city, highway, high altitude was bypassed and replaced, extreme high altitude, and others that have not been re-programmed. Also the various thermal management, passive and parked regen modes and other sub-operations have actually not been locked out. I would think the passive and parked regen modes would not become active with all the exhaust component logic disabled, but what about the rest?. Personally, I think this could have the potential to cause the engine to do some unpredictable things down the road when a sensor fails or some other system becomes unhappy.

Some could say that on the opposite end of this coin, M M 2 style programming that locks the engine down into only one (factory non-egr) operating mode is not perfect either. At least with one operating mode, the outcome is much more stable and very predictable. High altitude correction, extreme cold compensation, and various other conditions still happen, but not quite as efficiently as having an engine mode dedicated solely to such environments. Such is the sacrifice that one makes with all those systems axed from it. As long as the total sum of outcome does not shorten the life of the engine or its turbocharger overall, that is what is most important. Second to this is fuel efficiency, because no one wants an engine that sucks the tanks dry unnecessarily either.

If the program he had was not so out of date, had some basic compensation to the altered intake and exhaust flow, had corrected timing advance for the now much more volatile fuel mix, had cold ambient at least somewhat still enabled, and a few other tweaks IN EACH OF THE VARIOUS STILL ACTIVE OPERATING MODES + the passive, parked, fuel limiting, SCR thermal management modes disabled ... It would not have been half bad.

That is my opinion for what its worth, maybe I am just simply full of s#it too.

[Moose]

A small epilogue...


After several conversations with Rawse I'll believe his dissertation of the file I got from the other board. All I can honestly tell you without learning its intricacies is that it ran and went up and down the road but in a hammered dog turd kind of way. Now that he said it was locked in a thermal management mode it makes sense.

I lost 1.5MPG right off the bat, although it pulled like a raped ape, the turbo seemed like it was a couple kRPM from sending the turbine downstream and the compressor across the street. It didn't sound right, didn't sound or feel healthy.

When i went back to the asshat I bought the file from to tell him that I wasn't happy with the way it ran his response was "If you're not happy with the way it's running put the factory cal back in" Now, I know I'm walking in the shadows of a black market, I guess there really is no honor among thieves. Shame on me.

Out of respect for Rawse and his board I won't name him or bash him anymore than I have. Now, off the board is a different story.