it's scary what can be found in an ECM

chance cobb said:
The pulse width will jump to that column cus its trying not to add any more fuel cus you just lifted the gas but cus there is a number in that column when it should be a Zero you get your hang ?
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The combination of that and the fact the motor can't come down off the RPM's because it's still be driven in part by the rest of the drivetrain throw's the PID into an unstable condition. On one hand you're telling it no fuel, on the the other you're telling it to make pressure that it can't because of the limiter.

Bumping it down to neutral is the only time that ALL of the values (including pilot, main and post injection events) drop to zero because it's in a no load condition and WAY higher than it's allowed to be in neutral.

Dropping it to neutral and not having any throttle applied tells the ECM to command 750 RPM's (800 for a manual) and it's able to cut the rail pressure.
 
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Also what I see, because I wasn't paying 100% attention, You're on a duration table. If what you say about mm3 being a reference to tps, I see that at any pressure "0%" tps leads to 0 pw.
 
TheBigNasty said:
Also what I see, because I wasn't paying 100% attention, You're on a duration table. If what you say about mm3 being a reference to tps, I see that at any pressure "0%" tps leads to 0 pw.
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Not 100%...even when the truck is sitting there idling, it has a load on it and you'll never see that value at 0.

The only time the commanded mm3's drop to 0 is when the engine has no load on it, like when you're coasting down hill and the TC is locked. What you'll see happen here is all of the duration values drop to 0.

At an idle, sitting still, you'll see a very low commanded fuel number (high singles to low 20's isn't uncommon), depending on how you have the duration table setup.

If the truck is in gear, and you have a fairly tight converter, it puts a lot more load on the motor and it has to adjust to maintain idle.
 
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But if what you say about mm3=tps%.....in both tunes the pw is 0 at any pressure at 0mm3. The bottom table only shows maxed pw calling for high mm3....
 
Very rarely do you ever see that value at zero. For the motor to be running (unless it's being driven by the rest of the drivetrain) it has to have SOME fuel.

What this tune also doesn't do is bring the pilot completely to zero. Even on pilot alone, with the pressure up there over 20k psi, it's commanding between 160 and 260 uS of duration. It NEVER turns that off.

All of this is what set the PID into the unstable condition.

If that main duration in the zero column even sees 1 or 2 mm3's, it's commanding more uS of duration than most of the column all the way to the right. At 2 mm3's, thats like 50mm3's in the farthest right column.....with all that pressure behind it.
 
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LReiff said:
If what Rich is saying makes sense then tell us why Cummins put a value in the tuning software that EfiLive translated as "mm3" that some think is not directly related to fuel flow?

The tune is built around this parameter. You run out of fuel flow volume the engine loses power. You build the tune to reflect a loss of fuel flow by lowering the numerical value of this parameter and the engine responds the same as it would if fuel flow volume were restricted. A well built tune will have the mm3 parameter adjusted to match the fuel flow volume of the components on the motor.
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Exactly!!!

EFI has done such an awesome job of of giving us access to this ecm, and if you just dig at the software, some of the background stuff is not apparent .


The stock tune absolutely revolves around a few basic parameters, ONE being full load fuel volume or mm3's.

Lets go through how the ecm calculates the fuel mass for any individual given stroke.

Starting out with speed or torque demand (depending on ecm or end use)

(Accelerator position) at max actuation = Full load fuel volume. (mm3's)

BEFORE LIMITATIONS

Limitations being torque control, smoke control...AIR/FUEL ratio, speed ect.


NOW after limitations we exactly have our mm3's or (fuel mass)mg (depending on ecm)

(YES WE NOW HAVE OUR FUEL VOLUME/MASS already.....)

Next we check our fuel pressure setpoint chart vs rpm (Cool we now have our pressure point)

Next ON to the injector conversion table (Or pulsewidth table like efi likes to call it)

Using.....

1. fuel volume
2. pressure point

Placing our fuel volume required and pressure point into the injector conversion table or (pulsewidth table) we find our injector needs to energize for XXX amount of time to give us the volume of fuel our calculation started out with.

COOL....now we have our energization time.

Now what are we missing .....Oh yes.... TIMING.....

On to the main timing table, we know our rpm and we know our fuel mass we plan to inject into the combustion chamber, and BINGO there is our timing value (HOWEVER first taking in account limitations and modifiers)

NOW....

we have

1. fuel volume

2. pressure point

3. Injection duration to achieve our fuel volume from #1.....

4. TIMING.


There it is, wound up in a nutshell.

EFI does not make this all obvious, HOWEVER that is how it works.



NOW a quick explanation of the mm3's on the engine plate. This still seem's to be beyond doghouse's grasp so.....


Starting with the figure 129mm3's per stroke @ 2900 rpm for a rating of 325HP.


This IS the fuel volume shot into the combustion chamber during each combustion stroke.

OR

You can look at it per/cycle as some like to look at....

129mm3's * 6 = 774mm3's per cycle......knowing one cycle takes 2 crankshaft revolutions........(Now that number might start ringing some bells......)

OR

(2900 *6 /2 * 129mm3)/1000000 *60 = 67.338 liters per hour.


It is what it is, ^^^^ This is how it works.

Frankly if Doghouse wants to keep calling it "reference"......reference to angel tears or unicorn chit I don't care........
 
Flashscan said:
It would be indeed, the Cummins ECM (Duramax too actually) imposes a 400mm3 limit on it's calculations. If you put in 500mm3 to a table, the max it will pass through the rest of the system is 400.
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Cool.....good to know.
 
Your break down sounds great, and I applaud the breakdown, but you're forgetting one thing....IT's ONLY AT ONE SPECIFIC SET POINT IN THE ENTIRE TUNE, and it's the factory set point at that. The only application that is even remotely useful is in a genset or other stationary engine that works at that one RPM range and specified power output.

If you care to do that for each point on your standalone, AND take into account all the limiters, have at it swinger. In this application, its not needed.

Any one parameter changed results in a completely different output.
 
YES that is exactly one point in time for demonstration......, and all other times the ecm calculates it exactly the same in real time.

With this ^^^ Basic understanding on how the ecm works all the tables in efi will be much more apparent. (Of course those that are learning.......those that already knew it all.....of course.....know it all!!!......LOL)
 
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Sounds great, except that none of us are using factory parts, which means the ECM is NOT calculating ANYTHING correctly.

It doesn't even have to be a wild change to the motor. Put even the mildest set of injectors in, and it's wrong. Put even the mildest turbo on, and it's wrong. Change the exhaust manifold, and it's wrong.

The ONLY accurate calculation there is is with stock parts, at one given RPM. And even that isn't accurate. The factory calibration doesn't allow the engine to achieve rated output at the crank. Not the wheels, the crank.

The instant you change ONE variable, your entire calibration is out of whack.
 
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Cummin-a-long said:
Sounds great, except that none of us are using factory parts, which means the ECM is NOT calculating ANYTHING correctly.

It doesn't even have to be a wild change to the motor. Put even the mildest set of injectors in, and it's wrong. Put even the mildest turbo on, and it's wrong. Change the exhaust manifold, and it's wrong.

The ONLY accurate calculation there is is with stock parts, at one given RPM. And even that isn't accurate. The factory calibration doesn't allow the engine to achieve rated output at the crank. Not the wheels, the crank.

The instant you change ONE variable, your entire calibration is out of whack.
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Your right......LOL.....THATS WHAT TUNERS DO correct the calibration.....LOL :nail: At least the ones who know what their doing......LOL
 
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And if you want to do that on your standalone, go for it.

THAT'S NOT WHAT THIS APPLICATION IS.

The sooner you understand that the ECM IS NOT calculating the injected quantity, it's being TOLD to deliver this much pressure for this long. The result of THAT is the quantity DELIVERED. It has NO IDEA the size of the orifice in your injectors.....NONE at all.

The ECM DOES NOT CARE if the command is 1mm3 or 100mm3, that value is 100% meaningless unless it knows the pressure and the duration and THAT is what you are telling it.

You don't achieve a result by commanding a result. You achieve the result by implementing the variables. Those variables are what dictates your outcome.

You can say, "I want to put in 129mm3's into this space". It can be done with high pressure / low duration, low pressure / high duration, or a balance of both. Each of those results in a different outcome. One will make good HP, one will make good torque and the other will be in between both.

Quantity alone at a specific RPM is NOT what is going to dicate the power output. I can inject the EXACT SAME quantity and move it left or right and the power output is different. OR, I can inject less, move it left or right and make the same power.

You are so wrapped around quantity, that you're seeing it as the be all, end all in the power production process.

You can do all the math you like prior to firing up the motor, but when it comes down to it, you're still going to be adjusting those variables to meet the desired output. If the desired output is simply a QUANTITY, the ONLY parameters needed are TIME and PRESSURE. With those two, you get the quantity. The same quantity at 3 degrees does NOT get the same result at 8 degrees. And THAT means you'll be doing EXACTLY what we do with EFILive....put it on the rollers and dial it in. The difference is, we can apply it to a process that is actually usable in manageable time frame. If all you had to worry about was one motor for a racing season, sure you have the whole off season to do the math for each set point.
 
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Cummin-a-long said:
And if you want to do that on your standalone, go for it.

THAT'S NOT WHAT THIS APPLICATION IS.

The sooner you understand that the ECM IS NOT calculating the injected quantity, it's being TOLD to deliver this much pressure for this long. The result of THAT is the quantity DELIVERED.

The ECM DOES NOT CARE if the command is 1mm3 or 100mm3, that value is 100% meaningless unless it knows the pressure and the duration and THAT is what you are telling it.

You don't achieve a result by commanding a result. You achieve the result by implementing the variables. Those variables are what dictates your outcome.

You can say, "I want to put in 129mm3's into this space". It can be done with high pressure / low duration, low pressure / high duration, or a balance of both. Each of those results in a different outcome. One will make good HP, one will make good torque and the other will be in between both.

Quantity alone at a specific RPM is NOT what is going to dicate the power output. I can inject the EXACT SAME quantity and move it left or right and the power output is different. OR, I can inject less, move it left or right and make the same power.

You are so wrapped around quantity, that you're seeing it as the be all, end all in the power production process.

You can do all the math you like prior to firing up the motor, but when it comes down to it, you're still going to be adjusting those variables to meet the desired output. If the desired output is simply a QUANTITY, the ONLY parameters needed are TIME and PRESSURE. With those two, you get the quantity. The same quantity at 3 degrees does NOT get the same result at 8 degrees. And THAT means you'll be doing EXACTLY what we do with EFILive....put it on the rollers and dial it in. The difference is, we can apply it to a process that is actually usable in manageable time frame. If all you had to worry about was one motor for a racing season, sure you have the whole off season to do the math for each set point.
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DUH.....thats TIMING.......LOL
 
And yet, you are still hung up on the quantity REFERENCED in the tune.

Here, here's a table for ya....

FU.jpg
 
Cummin-a-long said:
And yet, you are still hung up on the quantity REFERENCED in the tune.

Here, here's a table for ya....

FU.jpg
Click to expand...

That's the greatest thing ever!! :bow:

I would really just like to spend a day with you and just try to learn anything and everything about EFI Live.
 
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