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Old 01-16-2013, 08:08 AM   #1 (permalink)
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Power & ECM Learn Down Power ?

Please help my confusion regarding Engine Control Module learn down ability. Meaning, regardless of what you bolt onto your vehicle to increase it's power does or does not the factory ECM adjust it to the level governed by the OEM ECM?

For example;
1. 2.0 + GMMP = 290 HP.
2. 2.0 + GMMP + GM Performance Exhaust = 290 HP.
3. 2.0 + GMPP + GM Performance Exhaust Solo exhaust + GM CAI = 290 HP.

Due to the parameters established by software in the ECM won't the ECM continue to learn down to the parameters allowed by the ECM?

Yes or no answers appreciated.
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Old 01-16-2013, 08:13 AM   #2 (permalink)
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I believe the engine 'learns down' to maximum torque, not HP. But that is only with an UN-tuned LNF engine. If you have GMPP tune applied (and most other aftermarket tunes) the 'learn down' is removed.
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Old 01-16-2013, 08:54 AM   #3 (permalink)
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As I understand it: The GMPP tune (on a manual transmission car) does not completely remove torque management. However, it raises the maximum allowed torque to a level where you will never top out anyway, on the stock turbo.

The GMPP tune does leave in place a couple engine protection protocols that some aftermarket tunes reduce or remove:

1. Max Turbo RPM: If the ECM calculates the commanded boost is resulting in the turbo spinning to fast, the ECM will intercede and reduce boost command.
(I have the GMPP tune on a manual transmission car, and I have observed this phenomenon. I live at high altitude and on a hot summer day the ECM has to to command a butt load of boost to compensate for the low ambient air density, while at WOT. In these conditions, the turbo will get to spinning to fast, so the ECM protection protocol kicks in and the ECM opens the waste gate a little to slow down the turbo)

2. Max Manifold Absolute Pressure allowed: If the ECM reads Manifold Pressure as exceeding maximum allowed threshold, then boost is reduced.
(I have never observed this protection protocol. And I have not read of anyone else observing it either. I suspect that this threshold is set high enough that it does not come into play on a stock turbo manual transmission car.)

The system is Torque based. In OEM format (no GMPP tune or aftermarket tune), the ECM absolutely "learns down" to the maximum allowed peak torque of 260 Lbs. I have personally observed this. Any mods you do to a stock car will learn back down in a few key cycles. The most you end up with is maybe a little quicker spool time on the turbo, but peak torque is quickly learned back down to the 260 threshold.

Now, as far as your examples:

1. 2.0 + GMMP = 290 HP (340 Lbs of Torque). Correct

2. 2.0 + GMMP + GM Performance Exhaust = 290 HP (340 Lbs of Torque). Correct
(Not because the ECM "learned down", but because the "Performance Exhaust" doesn't really add performance, just noise.)

3. 2.0 + GMPP + GM Performance Exhaust Solo exhaust + GM CAI = 290 HP (340 Lbs of Torque). Correct
(Not because the ECM "learned down", but because the "Performance Exhaust" & "Performance Intake" don't really add performance, just noise.)

The only proven mods that actually increase performance are:

1. Additional Tuning

2. Aftermarket IC
(May result in additional torque if your elevation is high enough that Boost Command is peaking out at the top of the efficiency range of the stock turbo. Known as "high altitude syndrome". The stock IC has about a 1-1.5 PSI pressure drop across, therefore the turbo has to run 1-2 PSI higher to compensate and deliver the commanded boost. With an aftermarket IC that does not have this pressure drop across, then the turbo PSI can drop accordingly; thereby getting the turbo back into it's peak efficiency curve. So you end up with an increase in peak torque available.)

3. High Flow CAT or CATless down pipe.
(Has been reported to increase HP by 20ish and increase torque closer to 30ish)

4. Replace OEM Turbo with larger and/or newer technology Turbo, along with new tuning.
(Now you are officially going big. You will quickly reach the max HP and Torque you can run on OEM engine internals: 400ish HP and 400ish Torque)

Sorry that wasn't a yes or no answer.

Edit: (GMPP tune and automatic transmission car)
If automatic transmission then 290 HP, but torque is limited to only 325 LBS.
(It appears as though GM did leave torque management in play and reduced for the automatic transmission cars. If so, then I suspect that the automatic transmission cars still have "learn down" in play and therefore would have to go aftermarket tune to realize any gains. Someone with an automatic and GMPP tune will have to comment.)
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Old 01-16-2013, 09:17 AM   #4 (permalink)
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Here is what I think I know about the factory tune:
There is a very lengthy post on this subject. Westers did a write up on the GMPP tune and what it does and does not do to the car.
The way the code is written in the ECM, the 2.0 is torque managed. The factory tune manages the engine parameters to produce 260 ft pounds of torque. The horse power is a result of achieving that torque value.
If you add hardware that is capable of producing torque values (and resultant HP) above the 260 ft pounds target, the ECM will "learn down" to achieve 260 ft pounds.
Basically, there are a set of data tables that are fixed. And there is memory that is controlled by the ECM. The fixed parameters cover all the possible variables, timing, fuel, air, boost, cam timing etc. Itís more complicated than that but conceptually you get the idea.
The ECM is constantly looking at all the sensors it has available. It is constantly "learning up and learning down" the various parameters it can control to maintain what it believes to be the settings that produce 260 ft pounds of torque.
Itís not strictly learning down because the ECM is constantly varying in real time the engine parameters it controls. What is really happening is the ECM is choosing specific settings from the pre-programmed tables for timing, fuel, air, boost, cam timing etc. based on near real time calculations. The calculations include throttle pedal setting, ambient temperature, air flow rates, O2 sensor readings etc.
The ECM "remembers" where it is at in each of the data tables. It "learns" where it is in each of the tables as it changes its mind on where to pull the settings from the tables based on current sensor readings. It does not create data per se, it uses the data it has in the tables but changes where it pulls the data in the tables based on a set of rules programmed into the ECM operating system.
Since the ECM can react faster than the mechanical systems it is managing, there is a built in time constraint on how much it can change its entry points into each of the data tables. The time constraint is a real time - mille seconds for some setting changes and key cycles for others.
Typically when you are running an unmodified car, when you start the car it "remembers" where it was when it was shut down and begins with that location as the current setting. It looks at the MAF to update air density and watches the O2 sensors to make sure itís managing the settings. But it does not make any big changes when you start the car. It is making small "make play" environmental changes to optimize the startup and initial running experience. It may make small changes during that run cycle but is constrained to making small changes per run cycle.
If you bolt on a piece of hardware that can produce 10+ hp, the ECM makes small adjustments per its constraints, but it will experience an increase in torque measured because of the hardware update. It will adjust the engine parameters to avoid damage - that is crank up the fuel to avoid lean runs and vary the timing to avoid knock. So you may see the 10 hp increase for that cycle.

When you shut the car off and restart it - executing one key cycle - the ECM will recognize that it is producing MORE than the target of 260 ft. pounds and will crank down the parameters it controls as much as it can in that key cycle. Over the course of 5-6 key cycles, the ECM will be incrementally adjusting the engine parameters to get back to the ideal 260 ft pounds. After 5-6 key cycles, with each cycle resulting in the maximum "learn down" allowed, the car will be producing 260 ft pounds of torque. Again the HP is a product of producing the value that results from the ECM setting parameters.
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Old 01-16-2013, 09:26 AM   #5 (permalink)
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Here is what I think I know about the GMPP tune:
The GMPP tune loads a new set of FIXED data tables. The ECM operating system still operates in fundamentally the same manner, but when it enters a particular data table it pulls out data that is different. The new data tables are designed to produce 340 ft pounds of torque with the stock hardware. The resultant horsepower is said to be 290 HP but itís again just a product of the new data tables.
The biggest change in the new ECM software is that it NO LONGER is constrained to the fixed torque rating of 340 ft pounds. It can go higher than the level because the data in the tables allows it to go higher.
There really is NOT a learn down feature.
There are constraints on the allowable settings in the factory tune and the GMPP tune. In the factory tune, the constraints result in the ECM always modifying its entry points into the tables to produce 260 ft pounds. In the GMPP tune, the constraints are higher because there is "room" in the tables for the ECM to "learn up" to a higher torque (and resultant HP) value. If you hit the edge of one of the data tables, then you are through "learning up". So itís not really a learning constraint, itís the combination of the data tables are fixed and constrained to max values, and the ECM has built in code that predicts what the turbo will do in the near future and will not allow any combination of settings that is predicted to over speed, over heat or over boost the turbo.
So there is not any real learning going on as I understand the system.
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Old 01-16-2013, 12:08 PM   #6 (permalink)
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Quote:
Originally Posted by rob the elder View Post
The biggest change in the new ECM software is that it NO LONGER is constrained to the fixed torque rating of 340 ft pounds. It can go higher than the level because the data in the tables allows it to go higher.
There really is NOT a learn down feature.
Hey Rob: Do you know anything about the GMPP tune for automatic transmission cars?

Is it the same set up, but they just loaded the initial tables with a lower torque (pretty sure they said 325 lbs for the auto cars): But it is NO LONGER constrained to that threshold, just like the manual transmission cars?

Or did they leave some kind of constraint in place, like with the OEM program?
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Old 01-16-2013, 01:23 PM   #7 (permalink)
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I do not know for sure, as in have any positive evidence, but what I think is that the GMPP tune adds new data tables that contain values for the automatic cars. That will deliver the torque values that the engineers want the auto to deliver.

Unless they also built in new constraints on the "learning" process, it should be able to "learn up" in a similar manner to the 5 speed tune, but with different data tables that are set at a lower torque value.

That implies to me that you can go up from the auto GMPP tune limits.

But as I say, I dont KNOW that as a fact.

I believe I have read posts by auto owners who have gotten significant HP increases however.
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Old 01-16-2013, 01:40 PM   #8 (permalink)
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This was always a bit confusing to me. I've heard about the lower torque available (from GMPP) for the Auto vs. the Manual. But I also heard that the auto is stronger than the manual - these two things conflict.
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Old 01-16-2013, 02:14 PM   #9 (permalink)
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Quote:
Originally Posted by TomatoSoup View Post
This was always a bit confusing to me. I've heard about the lower torque available (from GMPP) for the Auto vs. the Manual. But I also heard that the auto is stronger than the manual - these two things conflict.
But the Auto is a different beast. One glaring example is that it does not dump boost at the shift points. So maybe GM felt that the autos put additional wear on the rest of the drive train? Therefore they backed it off a little with the GMPP tune.

Which if that is the case; I find it humorous that GM did put the NLS into the the manual transmission GMPP tune, because NLS effectively mimics the auto shift of no boost drop. Of course I am sure the engineers assumed no one would be daily driving with the NLS function being used all the time.
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Old 01-16-2013, 02:24 PM   #10 (permalink)
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One consideration may be the software in the TCM. If the TCM and the ECM diverge, then the TCM goes not protection mode. It is possible that the TCM software is the constraint on the GMPP tune values. If you crank up the power output of the engine beyond that which the TCM can track as "normal" then you creat a new set of problems.
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Old 01-17-2013, 04:34 AM   #11 (permalink)
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Thanks everyone for their responses. The ECM learn down issue is why I was thinking some choose to go with an aftermarket tune, because aftermarket tunes removed (or altered) the GM, GMPP, ECMs learn down parameters.

Copied this from Crate Engine Depot
Solstice SKY HP & Torque ratings:
290HP @ 5,200 RPM
MT 340 lb,-ft of torque @ 3,600 RPM
AT 325 lb,-ft of torque @ 3,600 RPM
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Old 01-17-2013, 07:36 AM   #12 (permalink)
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Some great answers from the usual suspects. I'll just add this link to a thread I started way back when - look at the quote from a GM engineer in the initial post, although I'm not sure it adds much to what has already been posted.
LNF Mod Primer
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Old 01-17-2013, 08:56 AM   #13 (permalink)
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Excellent Thread wsphon.
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Old 01-23-2013, 02:05 PM   #14 (permalink)
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So to keep has anyone ever published numbers of the amount of HP/TQ that can be expected with the GMPP + Trifecta Tune (auto/man)?

Reason I'm asking is because I was thinking if you went with GMPP you couldn't also consider adding the Trifecta tune.
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Old 01-23-2013, 02:12 PM   #15 (permalink)
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Having the GMPP tune is immaterial - once you have the Trifecta installed that's what you get. The only reason for a progression of GMPP to Trifecta would be people that want to keep their warranty who later switch after warranty ceases.

You can find the basic Trifecta figures with a google. Usually 280 - 300 rwp (or about 40 more than the GMPP)
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