It's an interesting read if nothing else. I understand they are referencing heavy duty diesel engines but do you think this also applies to our engines?

STARTS HERE

It seems here lately, there has been a lot of discussion and questions asked about what some of these custom tuning shops have been doing to these newer diesel engines. Looking at some of their work, discussing the details of what they do, and seeing the aftermath of bad practices points clearly to a few serious discrepancies towards clear understanding of some basic processes. I have been doing a lot of research on this type of stuff because it has a direct effect on how long someone's engine lasts after they have this type of de-mandating + custom tuning done.

(Hopefully, and assuming for a moment they live in a country where that stuff is legal)...

People have been asking me about the differences and changes these newer engines are going through and why some of the things they do to "tune/de-mandate" them are no longer working, or are even sometimes contributing to pre-mature engine failures. It seems that the overall design changes that the engine makers have done to them is being mostly overlooked and greatly mis-understood. That seems to be where the problem lies, so I thought I would put down a few basic words to the effect based on what I have seen, observed, studied and have read.

This article is by no means any type of final conclusion, but is a basic understanding point based on observation and research for those who are doing this type of custom tuning who want to become better at what they do. I would hope that anyone doing such type of work would always be looking for the latest answers and solutions towards doing things in a manner that does not shorten engine life for themselves or their customers.

-- I have heard the argument time and time again. -- Its an engine, it is not that complex...

This is their mistake number one, and the biggest one of them all. Diesel engines have undergone some very serious changes in how they are internally designed here of late. I am not talking about that fact that they have emissions control components like EGR valves and DPF filters, I am talking about the design of the inside of the engine itself and particularly its combustion chamber. This is one of the most important things to understand if your one of those guys who is tweaking on fuel, air, and timing on these newest engines. It is this same lack of understanding, or disregard for these drastic changes that have directly lead to engine failures, fretted liners, cracked pistons, recessed valve seats, and a lot of other problems that have been seen here lately by these so-called "bad deletes".

Here is where the argument begins with a lot of these guys. They will argue...

"so what they changed the compression ratio? "
-- YES AND NO,.. it is far more complex than that,....

"So What, they changed the spray type and pattern of the injectors,.. it is an engine,.. fuel, air, and some injection timing and it will go,.. not that complex."
-- This is where they fail. Usually because they do not want to be bothered to learn that it is much more complex than this simple minded viewpoint.

Here is what I think a lot of these guys are missing and do not understand ...

The main injection process has dramatically changed. So much so, that it can cause a good tuner to damage a newer style engine simply because they do not conform to the rules of that process.

Here is an equivalent analogy...

A dog likes to eat meat. A cow likes to eat grass. A plant likes to be watered. -- Then someone coming along and saying --- "The heck with it. It can't be that complicated,... they are just life forms. - Just water the dog, give that hungry cow a steak, and pour grass over the plant".

There are so many things wrong with that way of thinking that it is not even funny, so if your a custom tuner, I suggest you get your head cleared up and get ready to learn a thing or 2 if you have not already done a lot of research ...


Because of emissions standards, the combustion chamber, injectors, pistons, etc. in newest diesel engines have been re-designed around a completely different combustion process than the older diesel engines of the past. They use much newer and different types of injection processes and it greatly effects everything going on inside the engine. Lets discuss some of these different strategies so that we can understand them better. They are a big part of why you can't just simply throw fuel and air at an engine any more...

I lightly touched on this in this post...
Rawze.com: Rawze's ISX Technical Discussion and more

I thought I would say a few more words about injection strategies and what I have learned/observed so that others may benefit, and hopefully stop making bad programming for themselves or their customers...

( Injection strategies and their meanings are explained further down in the article, just generalizing for the moment here) ...

One of main changes that have taken place due to emissions standards is that diesel engines are physically evolving at a rapid rate. Prior to about 2003/2004 or so, every diesel engine out there was basically designed around what is known as CDI injection. In about 2004 or so, to meet emissions standards, that had to change. It was too unpredictable and there was little control of the combustion process, so engine makers started designing their engine around PCCI injection. PCCI injection gives a much greater control of the combustion process, its temperatures, and emissions standards could be met by re-designing the engine to use this strategy. -- then the emissions standard changed again. In about 2009 or so, engine makers started using HCCI injection methods, but not heavily, as it is still so new and hard to control. Then again in about 2010/2011, they designed the combustion chamber, injectors, and everything else fully around HCCI because it offered the best solution to meet the newest emissions rules.

In a nut shell, diesel engine designs have gone through some serious hardware changes internal to the combustion chamber. Here seems to be the stages of advancement they have undergone ...

* CDI injection.

* CDI with partial PCCI injection.

* Full PCCI injection.

* Full PCCI with partial HCCI injection.

* Full HCCI injection with partial PCCI injection.


I want to discuss each one in a bit in regards to injection timing with detail for each of these so here we go...

* CDI injection.

- CDI (Conventional diesel Injection) in its simplest terms is the equivalent process of dumping fuel into the intake of a diesel engine long before the cylinder is compressed enough to make the fuel burn. A lot of older articles floating around the Internet that have to do with combustion theory and diesel engines talk about injection timing of 14 degrees BTDC and even as high as 20 degrees BTDC. This is typical of CDI injection.

2-stroke engines used this and 4-stroke diesels used to use this too. The injectors were clunky and spray liquid fuel into the cylinder, and it took some serious amount of time for the fuel to mix and the temperature to rise enough to make it burn well. Hence, the early injection timing was set for +8, +12, +14, or even +20 degrees depending on compression ratio before TDC in some engines. The reason for such early injection is to allow extra time for all the raw liquid fuel to mix before it burns. Try doing that with an HCCI engine and you could blow it apart at high torque and fueling levels. The days of CDI engines are long gone and over. The sad part of the loss of CDI designed engines is that they were the most forgiving and robust, had low compression ratios and were forgiving for custom tuners who weren't so knowledgeable. Because compression ratios were low and injectors were spraying mostly liquid fuel, they liked to be over-fueled, over boosted, and the engines were built tough as nails. All the soot out of the stacks was the result of those very large unburned droplets of fuel when you got on it hard. The final combustion peak cylinder pressures (Final Crank Angle) is a loose-fit sort-of "git-er-done" mostly uncontrolled point but it did not matter much. The length of burn to prevent detonation was done by adding more liquid fuel to that was difficult to ignite to lower temps. Engines were built tough enough to handle this unstable condition and the loud rattling of the valves were a typical result. The length of burn through the stroke was always long due to poor mixing of the fuel and this prevented detonation in all but the most extreme of cases of abuse.

- I have met plenty of custom tuners who are clearly still stuck in that era who would argue that all diesels are the same and still practice those things in the newest HCCI engines. This is all while wondering why it blew a head gasket 40% sooner than it should have, or hammered out the crank or wrist pins in a short time, accusing the newer engine of being inferior instead of taking a look at what they might have done to cause it.


* Then came PCCI injection.

PCCI injection (Premix Charge Combustion Ignition) is basically a much improved version of CDI injection and is an attempt to "wrangle" both the emissions and that moment of unpredictable final Crank Angle (point of peak cylinder pressure). CDI/PCCI was around in its early forms before the onset of EGR, hence some engines that were mostly CDI would use some PCCI injection strategy for improved fuel mileage, but the PCCI injection process itself makes the fuel burn too quickly due to a finer mist. The onset of detonation would occur at higher torque and power levels, so as a CDI/PCCI style engine reached high torque output, it would transition back towards CDI to protect itself. This was done mostly by over-fueling the cylinder and retarding the timing. It can be seen in older engine timing/fueling maps where the timing advance drops off sharply and where the fueling is increased at those same regions in a fuel table. Some engines used a lot of late PCCI injection where the timing advance maps would have negative numbers in them and go slightly higher as they transitioned. It all heavily depends on the injector design, injection pressure, spray pattern, width, and how fine a mist they would spray.



The bulk of PCCI (early injection) still puts the fuel into the combustion chamber BTDC, and it still does it before it has reached high enough temperatures to ignite the fuel, but it only does it at about +2 - +4 degrees (+8 or higher being an extreme). This is because the fuel is in a much finer mist and spreads/mixes quickly. The higher the BTDC setting in the engine, the more time it has to mix and saturate the cylinder before it starts to ignite. This creates the problem of >>

The longer it is allowed to mix, the more volatile and the sharper the peak cylinder pressure will become.

With PCCI injection,.. increasing the BTDC timing LOWERS the overall crank angle because the fuel ignites quicker and more violently. Decreasing BTDC reduces the mixing time before it starts to ignite and RAISES the final crank angle, dulling the entire combustion process.

Remember, the goal in EVERY style of diesel engine during the combustion process is to correctly control 2-TWO main things with regard to injection process and timing advance. The final crank angle, AND how long the burn happens (how sharp or dull) to prevent detonation and hammering of the components...


Then came the EGR Valve...

With the advent of the EGR valve and EGR circuitry, suddenly PCCI injection could be controlled very well. There was no longer a need for CDI injection at all. Full PCCI engines spray a much finer mist instead of mostly liquid fuel, and the entire engine from its internal temperatures, the air/fuel temp, and about 50 other things are monitored closely to help control the final CA (Crank Angle) and proper final timing. The advantage of the EGR valve is not only better emissions control, but the EGR gas itself can be used to adjust the length of burn in the cylinder, preventing completely the problem with PCCI injection becoming too volatile at higher fueling/torque rates. To the engine makers, better fuel mileage, better emissions control, better management of CA and burn length. Both are achieved in PCCI engines with EGR gas far beyond anything CDI engines could even come close to.


Understanding PCCI Early and PCCI Late injection strategies...

With the addition of EGR gas to control the length of burn, it is now possible to advance the timing and allow of a LOT more pre-mixing of the fuel before it burns without worry of detonation. This improves fuel efficiency by a lot, even when considering there is less oxygen to go around by the EGR gas. The only problem is that it needs a lot of EGR gas to slow down the burn. This is not good for making a lot of torque and power. This leads us into the PCCI late injection strategy.

PCCI late injection (far less pre-mixing and retarded timing advance) is used to control length of burn when there is a demand for high torque, more fuel, more oxygen, and therefore less EGR gas to get us there. Retarding timing advance is also slightly less fuel effecient so it becomes a trade-off, or transition.

-- Looking at the timing maps of PCCI engines it becomes clearer what is going on. When the timing map has +6 - +8, or even +9-+10 degrees BTDC in it in its mid range of fueling and rpm,.. it is very clear that it is PCCI early injection strategy and the EGR gas itself is used to control detonation and burn length. As you go higher in torque and fueling demand in the map, the timing advance falls off sharply at some point and this is where it is transitioning towards PCCI late injection and very little EGR gas. -- It should be clear as mud by now if your reading and learning this that the entire combustion process, the final CA, and burn length is controlled by not only the timing advance and fueling, but equally the EGR gas itself. Altering any of these throws the engine CA and burn length off by several degrees and problems with detonation, hammering, burn length becomes hard to control real fast with PCCI injection.

-- The trouble, de-mandating, and custom tuning...

The trouble is that PCCI injection itself makes the fuel burn much hotter and quicker without that EGR gas. it is not just the extra oxygen doing it, but the design of the cylinder/injector itself. Custom tuning shops are just too quick to axe these systems and block that gas thinking they are dong a lot of good to the engine. All they seem to think about is how "clean" they can make it burn and they have no idea that the gas itself is large contributing part of the process and its stability. With no more EGR gas, that early PCCI injection the engine was using to increase combustion efficiency now becomes a serious risk. At higher power levels it will be downright engine damaging. This means that there is no correct injection timing map any more in the engine. There is no more proper fuel-air mixture map, or any other maps or settings in the engine that are designed to handle this situation. This leads into arguing about the the engines protection mode that some tuners rely on to make the engine right again.

The protection mode...

Most of these newer engines do have a protection mode, or protection mode mappings in the event of the EGR gas being blocked or being incorrect. The Emissions standards call for, when there is an error, that this mode limit emissions directly and also limit power/torque or have some other severe penalty if someone blocks off that EGR gas. The injection and fueling maps in these modes limits fueling and torque, or boost pressure, or other things to meet the standard,.. but also the injection timing map is written to severely retard the timing in all but the very highest torque output to lower emissions and to protect the cylinders from detonation. It is definitely late PCCI injection, so late in fact that the fuel does not even pre-mix, simulating CDI injection but very poorly.


-- Is this starting to paint a picture here???

-- Now we are in La-La-Land...

Someone altering the emissions components has now sent the engine into La-La-Land with its timing, fueling, final CA, burn length, and everything else. If the ECM detects this, it will jump into protection (non-egr gas) mode and the timing and everything else is set like mentioned above to protect everything and penalize the driver. -- The problem is that a lot of custom tuners do not use this protection mode or its settings. After-all, it is NOT what they want. They want full power and torque and full boost and all the things like they were before,.. Only the whole engine is in a state of disarray towards detonation and a lot of other problems.

PCCI injection Without EGR...

Engines designed around PCCI injection that suddenly have the EGR gas removed have no settings in them whatsoever in any of the engines operating modes to achieve the same level of power/torque/efficiency that they had with the EGR gas. In all the main operating modes, the timing is too far advanced, relying on EGR gas to set the burn lenght and in the protection modes, it is too far retarded. This means all new settings have to be found, not only for the timing advance,.. but for everything else from the boost pressure, the fueling, fuel-air mixture, and an entire myriad of things to bring the engine back into safe specifications.

"Poking around in those factory calibrations and copying-pasting tables is not going to get you there,.. not even close!". The data simply is not there!. There IS NO PROPER MAP ANY MORE -- YOU ARE IN UNCHARTED TERRITORY WITH SHARK INFESTED WATERS WAITING TO SEND THAT ENGINE TO A SLOW AGONIZING DEATH WITH HAMMERED WRIST PINS, FRETTED LINERS, AND A FAILED HEAD GASKET!

The injection timing of a PCCI engine without EGR gas to control it now has a very limited range of acceptable settings. Fortunately, larger diesel engines are tough and can handle some limited abuse from this, but not much. Leaving the PCCI early injection and its +6 - +9 and i have seen as much as +10 degree timing advance (now without EGR because no one corrected it) at very low torque and fuel output settings can make one burn the fuel so clean that the engine oil no longer turns dark. CDI engines just could not achieve this without detonation, as the droplets were simply too big to get them that clean. It gains a lot of fuel efficiency but it can only be done at low energy levels (roughly the bottom 1/3 of the engine potential). At low torque and fuel settings the overall energy released and overall combustion pressures are low enough to get away with it without harm, as long as it was not set so far out to cause slight detonation and excess valve lash (problems with recessed valves will set in).

With early PCCI, put the screws to it, and it is problem city...

The normal factory timing advance map now has to be altered so that the engine only uses late PCCI methods as fueling and torque demand go up in all operating modes that the engine may still be operating in. This now somewhat retarded timing slightly lowers fuel efficiency and is needed as a protection for the engine and its components.

-- That is -- If someone has taken the time to re-map everything to match this.

This also includes new fuel-air ratio and everything else to match new timing table(s) that are required. I have seen almost no one who claims to be a custom engine tuner doing these things, nor know about them nonetheless able to even discuss them. The bulk of them have no idea that the cylinder design is now vastly different. All the tuning tricks and things they got away with on an engine just one year prior, no longer works correctly. Ask them what PCCI or HCCI injection is, how to properly control an engine designed around it, or even its early/late strategies, and they all seem to draw a blank (or give a smug look and pretend it is a secret).

The typical response is yet again, that it is not that complex. Most would rather keep their head in the sand and pretending to "know what they are doing", putting your engine directly in the high risk zone of pre-mature failure. Others will argue that somehow the ECM and all its factory settings will magically adjust itself and everything will be ok. - It is simply not true at all.


* Full HCCI injection... engines similar to the 2250/2350 comes to mind here ...

HCCI (Homogeneous Charge Combustion Ignition) is the latest and greatest in modern diesel engine design. It is so new in fact that the engine makers themselves are still trying to figure it out. HCCI is basically the process of spraying fuel into the cylinder in such a way that how "mixed" it is, is no longer controlled by advancing/retarding the timing. The mixing is almost instantaneous and fully atomized, fully "Homogeneous" (100% even mixture) by the time the burn process starts. This changes the game by quite a bit and normally will create a highly volatile explosion,.. like a fire-cracker or a bomb going off all at once. It is a very efficient release of the energy of the fuel. It is achieved through extremely high fuel pressure (common rail) and the injectors are designed to spray a very wide atomized pattern of fuel that penetrates into the cylinder very very quickly. There is really no way to control the burn length in a cylinder under HCCI control with fuel this well mixed without EGR gas and pulse injection cycles. Some engines use internal EGR by using a pre-combustion cycle that burns out a portion of the oxygen to achieve the same thing. This is often the engines only protection against serious detonation issues. All the same processes described in PCCI and the problems associated apply here, but in a more amplified state.

Timing maps of PCCI/HCCI engines and full HCCI enmgines...

You can always tell the injection maps of HCCI common rail engines. The injection timing maps look severely retarded compared to older CDI and normal PCCI engines. This is because they do not need time for pre-mixing in the map, and a large portion of the injection cycle happens during and after TDC because the mix is so volatile. The engine cylinders and injectors are physically designed this way and you can throw out all that "it needs timing advance" to run right way of thinking to the curb real fast. Many custom tuners will look at these retarded maps, assume it is for heavy emissions control, then go about advancing the timing by several degrees. They are dead wrong and amplifying the problem in thinking/doing that. Most have no idea that the combustion process of the engine they are looking at has dramatically changed and everything they know or are assuming about it is now defunct!.

Just like PCCI injection, there are early and late injection strategies for HCCI. The trouble is that HCCI is very difficult to control even by the engine makers, so they resort to simulating PCCI injection at high torque output to protect the engine from detonation, even when using EGR gas. Earlier model HCCI injection engines had lower compression ratios resulting in a lot of difficulty controlling burn HCCI length. The HCCI was only used in the mid range of the engines output torque, and it can be seen by high timing advance, but what is not seen is the higher amounts of EGR gas used to pull it back into spec. The EGR gas itself actually heavily influences the timing advance in the HCCI process. Timing advance is set very far forward, and the EGR gas itself brings it back down for the final crank angles and burn time. Taking away the EGR gas throws if far enough out of whack to start causing long term damage.

Overall, HCCI does not do as well as PCCI at extreme low rpm and torque, nor does it do well at high output and torque. It shines in the middle though and makes the engine meet the strictest of emissions standards while maintaining high efficiency. It is the only way they could meet the very newest standard so this is why it is used.

The problem with HCCI,... higher aspirated/mechanical compression ratios (18.9:1 instead of 17:1) in the newest engines has proven that HCCI can be much better controlled by the use of less "stuffed in" oxygen and reduction of exhaust manifold pressure (smaller turbo, less boost, etc.). This is even before using EGR gas.

NOTE: Remember, there are actually 2 ways to make cylinder pressures go up. Either by raising the mechanical compression ratio of the engine,.. OR by turbo charging (boost). there is a difference between the 2 though. The mechanically raised compression ratio contains quite a bit less oxygen than using turbo-charging (stuffing more air into a smaller space) to achieve the same pressure. Bringing the compression ratio up for better HCCI control without adding oxygen was the goal. That is why they are mechanically higher compression ratios here lately. requiring far less boost. - I hear the newest 2018 engines are even higher yet at well above 19:1

With higher compression ratios of the engine, Early HCCI now becomes more viable at higher torque output settings, making the engine slightly more efficient. Early HCCI injection is used heavily even at higher torque levels on engines with 18.9 compression ratios. Late HCCI injection is used in any protection mode, where as much as -2 degreed BTDC (putting fuel in AFTER TDC) severely retarded timing to protect the cylinders from this very volatile fuel mixed and a lot lower injection pressure. it creates a sudo-simulated PCCI mode that can be used when needed.

HCCI without EGR...

If you have followed through and studied the PCCI stuff I mentioned above,.. then you might stand a chance to get one of these set close without EGR, otherwise,.. This is the stuff of science fiction for you and you need to stay away from these newest engines.

An engine with mechanically high compression ratios and injectors designed specifically around HCCI requires that EGR gas as it is set from the factory in all its operating modes. Taking that gas away requires a complete re-design of the entire injection process to simulate PCCI more hevily and to use the pulse injection to help control burn length again. It is no easy task at all to get right, and the high compression ratio and volatile spray of these injectors makes the timing advance extremely sensitive. As an example of how much more sensitive they are, 1 degree change on this system at higher torque levels is like 3 or 4 degrees change on a CDI engine.

Without EGR or (some engines use a pre-combustion burn cycle instead), you are completely in uncharted territory 100%. No engine that uses HCCI is designed to properly run like this from the factory and you can stare at all the maps and tables you want to,.. you are not going to find an answer.

- Will it run? -- Any engine you throw fuel and air into will run, that is what they do. But that does not mean you have a stable, viable solution to removing that EGR gas at all.

will it run somewhat ok? -- Maybe, but you had best not have engine torque or HP set at higher than about 50% of the engine power/torque capacity. Otherwise it will likely have a short lifespan.


Can one be made to run correctly without the gas? -- Very difficult to achieve but is possible. A LOT of editing and corrections need to take place. Things like heavier simulation of late PCCI in the upper and high torque output ranges, moderate to heavy changes to charge pressures, fuel-air mix, completely new injection mapping that corresponds to the now sudo-simulated late PCCI, and a whole host of other tings. The pulse injection timing can also be used to control/limit detonation, maintain engine component stability, and to lessen the piston drag seen on the liners/cylinder walls seen with higher compression engines.

In a nut shell,... ALL of these very newest diesel engines are a far cry from anything seen in the past and if you, as a custom tuner are stuck in the age of "fuel, air, and timing," and have very limited views of all this stuff, i feel really bad for the engines you are programming.

All this CDI / PCCI / and now HCCI is in the present and will continue to be future of what you do. Not understanding and following this technology is only going to make things harder and harder as you go along. You can't "just add some fuel" to cool things down any more, you can't "just back off the timing", or god forbid, someone advances it even more like a real dummy to lessen detonation any more. You can't just "raise the fuel pressure or boost levels " to get it to burn cleaner or make more power. They just are not built that way at all, and something somewhere will suffer and fail as a result. Maybe not today, maybe not next month, or in a year perhaps you are still lucky,.. but it WILL EVENTUALLY TAKE ITS TOLL! and the engines of the future are only going to get more and more complex and sensitive to this stuff.


My advise --- STUDY STUDY STUDY AND LEARN THESE NEWEST INJECTION AND COMBUSTION TECHNOLOGIES because if you don't,.. And don't start making engine programs designed to work with the hardware you are hacking up, you will only look like the fool that is tearing up engines blindly that others with similar thinking to myself have to go behind and straighten out! - Car engine are like this now, Truck engines are like this now, and Industrial engines are too. the technology keeps changing,.. Why aren't you?

 

Direct link won't work without being registered and logged in it look like.

Thanks for fixing that broken link by posting the info here.

 

What an essay... It sure seems like you've had a bad experience with someone, just spit it out man so we can learn and stay away.

I totally get your point here though, I got the isx too and I had a few of them worked on and wonder constantly about these things.

On the other hand, I also agree that it is an engine after all. I always felt that a diesel engine is designed to detonate. There are cetane boosters which actually increase the volatility of the fuel just for that reason. But that's just what I learned in school from old guys who probably only knew cdi. So I'm definitely not debating you.

 

Just for the the record this is not my rant/essay. I copied it from another forum. I personaly don't own a big rig truck, I just found this very interesting and wondered if any of the therory applies to our trucks.

.

 

Sounds like they learned the lesson on the ISX people learned on the 6.0 about ten years ago; you can't just throw timing and fuel at an engine and expect it to hold up as well. Combine that with higher injection pressures resulting in better fuel atomization, I can understand viewing exhaust via EGR as an inert gas to temper the much cleaner burn newer diesels have.

The 6.0 can't go over about 28000psi for fuel pressure, based on the 7.1:1 ratio between fuel at the nozzle and oil in the injector body, and HPO capping just under 4000psi, the engine probably runs more in the 10-15000psi range normally. The common rails can get up to 44000psi, meaning the fuel spray has to be better controlled so it doesn't burn at the wrong point.

But our little dinky 6.0s with the perpetually clogged EGR valves and HEUI injectors.... I'm not going to sweat it. Don't run canned tunes that jack up cylinder pressures by playing with the timing and dumping fuel, and don't worry.

 

I tried rep'ing you, Bryan, but still in jail....

And if one skips forward to Bryan's 7 or so sentences, he's summed it up pretty succinctly....

 

Just my thoughts being around the powerstrokes... they have litterally been light years ahead in controls vs everyother truck in the market.