CM871 Engine cycle...

[Unilevers]

heres come the tennis ball, schoolbus, and bowling ball explanation. it really is a rather good story....

[Rock hound trucking]

i have the same trouble with my @m*m^2 any boost over 38 psi and i get a a vibraton back out of it and the vibration goes away . how can a guy fix it or what changes have to be made . i pull the mountians lots and like the extra power my pyro runs around 750 when pulling hard with high boost once a back out it it drops down just below 700

[Rawze]

(12-22-2016 )Rock hound trucking Wrote:  i have the same trouble with my @m*m^2 any boost over 38 psi and i get a a vibraton back out of it and the vibration goes away . how can a guy fix it or what changes have to be made . i pull the mountians lots and like the extra power my pyro runs around 750 when pulling hard with high boost once a back out it it drops down just below 700

Lower the boost levels a bit. It sounds like your making too much boost for the power your making.

[Hammerhead]

(12-22-2016 )Rawze Wrote:  

(12-22-2016 )Rock hound trucking Wrote:  i have the same trouble with my @m*m^2 any boost over 38 psi and i get a a vibraton back out of it and the vibration goes away . how can a guy fix it or what changes have to be made . i pull the mountians lots and like the extra power my pyro runs around 750 when pulling hard with high boost once a back out it it drops down just below 700

Lower the boost levels a bit. It sounds like your making too much boost for the power your making.

With winter temps the air is more dense. This translates into more boost pressure than summer time. If you drove an older truck with a standard fixed vane turbo and a boost gauge I'm sure you noticed that they would always make more boost in the winter, particularly on really cold days.
Watch your boost gauge on a good pull and make a mental note of the rpm range where your boost exceeds 38psi.
Pull the cal from your ECM, in the C_TCG_Min & Max table lower the numbers in the upper range of the table of the rpm range where you were exceeding 38psi by 2 is a good starting point. Then send the file back into the ECM, and make note of boost pressures again. Repeat if necessary. If you're only noticing it exceeding 38psi on really cold, -30 or more days, just feather the throttle on those days.
I've had to do this with winter as well.
*NOTE!!! This is with @M*M^2 that uses controlled VGT closing percentages, NOT a tune that uses the mass air flow and let's the ECM decide the VGT position. If you don't know which version you have, confirm it before doing what I have suggested!

[axe]

My CM870, stock form and tune, will boost around 5lbs less on cold days. Teens and below. Just wondering?

[Hammerhead]

(12-22-2016 )axe Wrote:  My CM870, stock form and tune, will boost around 5lbs less on cold days. Teens and below. Just wondering?

The air operated VGT is not "position reported" like an electronically controlled VGT therefore the ECM cannot "verify" the command of closing. So an 870 uses the mass air/charge flow calculation, and the ECM can calculate that the colder air is more dense, therefore it commands less closing, reducing the boost because it "knows" there is enough air molecules (the density) for the amount of fuel.

Think of it like this:
One cubic foot of air is one cubic foot of air, but we all know that the air is thinner at 10,000' than it is at sea level. At 10,000' there are less molecules of O2, N2, and the other gases that make up the atmosphere because there is less pressure, there is more space between the molecules which is why the volume is the same.
Temperatures have the exact same effect on atmospheric gases, so the colder it is, the more molecules of O2, N2, and such in each cubic foot of air, so the ECM knows it needs less boost to get the correct number of O2 molecules in the cylinders to burn the amount of fuel being injected.
The @M*M^2 tune uses input commanded VGT positioning from the table, so when the air gets more dense, it's putting more molecules of atmospheric gasses in the cylinders, so the percentage of closing needs to be cut back a couple of points to keep from over boosting. The MM tune is set for very fine control, so when these conditions change it becomes noticeable when you watch your gauges closely.

[Signature620]

Could somebody please offer points for & against min/max closing tuning VS Mass Flow tunes? I've only ever used TG tables but I'm interested in the MCF side.

[Marajin]

(12-23-2016 )Signature620 Wrote:  Could somebody please offer points for & against min/max closing tunes VS Mass Charge Flow tunes? I've only ever used TGC tables but I'm interested in the MCF side.

870 and older engines have no TG (min/max positioning) tables. they can only be set for positioning the turbo via mass flow formulas.

781 and newer have min/max tables, allowing for a choice of either type of control.


mass charge method
++++++
The turbo tries to self-adjust within its full travel range, to control the boost based on a lot of factors like fuel flow, fuel air mixture, temps, etc.

Pros/cons...

* It is full-range Auto-adjusting. This can be both good and/or bad. When all is right with the engine and there are no CAC leaks or bad/incorrectly reading sensors then it works well. The bad is when you get incorrect sensor data. A bad reading exhaust gas pressure sensor can make the turbo go out of control and make way too much boost. it can get so bad that it can even destroy the engine and turbo. Same thing if any other sensor is going bad or reading incorrectly. This can also be bad if you have feedback data from a sensor like the ambient temp sensor and it throws the engine into the wrong engine mode like high altitude, or cold startup, etc. This throws everything off, including charge flow and turbo boost levels.

* CON: There is a lot less ability to pre-spool the turbo for better engine performance and the engine typically has a bit more lag than the other method. The turbo simply will not want to spool up until it first sees the fuel demand. A truck that suffers city stop/go traffic all day every day will have darker oil and a higher potential for black smoke from the stack than one that has been programmed to pre-spool for such operations.

* Engine/turbo boost/efficiency is directly effected by the myriad of engine sensors that can read a bit off, and effect turbo positioning in negative ways.

* CON: A CAC and/or exhaust manifold leaks, bad sensors, etc. will be harder to detect and find. You end up with hidden and mysterious fuel mileage and other losses if something is not quite right, and the turbo, because it "compensates" for leaks etc. ends up masking your real problems quite often. You end up guessing at your problems more than you should when something is wrong.

* PRO: when everything is right with the engine, The turbo will always "try" to only provide minimum boost levels for any given rpm and/or torque of the engine in an attempt to maximize efficiency. This can be pretty effective. On the other hand, tgc-style turbo tuning can be as effective, and quite ofter more, but requires effort in test driving, and fine-tuning the adjustment tables to get right.


Min/max Closing Limiting Methods
++++

The turbo does NOT go just anywhere it wants to based on feedback data. It has some, but very limited adjustment range/compensation of its own, but very little. Instead of letting the turbo go where it wants to based on a lot of information and math, someone programs it to a specific position for each rpm, fueling etc. with only a narrow window of adjustment range. This only allows it to make minor adjustments and "cages" it to within a narrow range of self-adjustment so it can't get too far out of whack from what the person who programmed it wants it to be.

* CON: If not done correctly, you can have the wrong boost, etc. and if bad enough,.. same thing.. engine damage from over-boosting, etc.

* CON: Must be dialed in for each type of truck to get right. Every truck has different intake and exhaust air flows, different components, different pipe sizes, CAC size, etc. Getting it just right can be a challenge if not familiar with differences among truck makes/ models, and brands.

* PRO: The turbo can be pre-spooled and controlled much more precisely, etc. for trucks that have stop/go operations like city trucks. or for competition.

* The turbo will no longer auto-correct for larger CAC and other air-flow problems/leaks and/or bad/incorrect sensor feedback. It will make only minor corrections, so if you get a CAC or other intake or exhaust manifold leak then it will directly effect boost levels and engine efficiency. If you have a boost gauge then you will see that something if off. Personally I think it is easier to find and fix air-flow related problems that effect fuel mileage when programmed like this. If the turbo gets weak and worn out, you can see that too. If it is expected to provide a certain boost level at a certain position,.. and it does not,.. you can see and feel it in the engine and know something is wrong.

* PRO: The ability to "fine tune" exactly what boost levels you want at any given rpm/torque, allowing for getting better performance and/or efficiency above what the engine wants to do on its own.

* CON: It is more difficult to get "just right". It requires test driving etc. to ensure it is dialed in correctly. The turbo and its operation are solely reliant on the skill of the tuner and it is now a bit more "finicky" per truck to get right. -- More work for the tuner, more difficult to do up front. it also will reveal charge flow or turbo problems if the tuner has to adjust it very far outside of the norm for a particular brand/make of truck.

* PRO: When done right, and dialed in correctly, it can have higher gains than other methods simply because of an overall more precise control.


============

- Many people who claim that they are ECU tuners do not have any clue how to properly tune/re-program a turbocharger at all regardless of either method. They leave the factory settings for the turbo untouched. This is VERY VERY VERY bad!. They simply use the factory set "mass charge" method/settings,.. but do not compensate for the changes that they have made to the engine. Drastic changes take place to the overall intake flow, exhaust flow, and EGR flow(or now lack thereof) during a de-mandate(delete) in countries where it is legal to do so. The problem is that they always make the false assumption that somehow the engine will magically adjust the turbo to correct all their massive butchering/alterations through hollowing out cans and installing block-plates etc. -- What they don't realize is that all the sensors are screaming different data now and it confuses the hell out of the mass flow and turbo as a result. Over-boosting, unstable turbo operation and eventually and engine damage is almost always the result.

During a de-mandate and tuning, because air/exhaust/charge flow is altered - Corrections have to be made for the engine and its turbocharger to operate correctly regardless of what method you choose to use to achieve it. BOTH methods are very good and have their place. Think about someone who does not want to fine-tune a turbo and have the truck test driven possibly several times to get it right, who is doing the tuning remotely over the Internet. they STILL have to edit/adjust the mass flow tables to compensate for all the changes, but its much more lienient (though the numbers themselves are very sensitive).

Personally I like the TG method the most. It removes all question as to what the engine should be doing and it simply does what it is told to do (assuming it has been done right to begin with). Something suddenly changes or goes bad, you can see and feel it right away. I like this the most.

[Unilevers]

I personally run the TG method. both work but the MCF method is too reliant on feedback and i find is very lazy and slow no matter how you tune it. My favorite is when the PID screws up and the logic jumps outside it range and the vgt starts going to infinity....because this happens with MCF mapping.

I know where i want that turbo, and i want it where i tell it to be with no BS from it. Yes this requires tweaking and tuning for each and every truck, but over time you know ballpark numbers and can dial them in much faster than you would think. This is why i always ask on remotes what type of truck is it, because it matters alot.