Author Topic: engine issues: the problem could be.... (Read 15160 times)

Gentleman Jack · « **on:** July 12, 2011, 09:24:13 PM »

With the recent threads about engine failure and some indication it may be related to the GMPP tune or tunes of cars that had / have the GMPP tune, I started doing some research. I don't have a ton of back up for this yet, so this is as much a discussion as it is a dissertation. Here are some thoughts I have been working over with someone that has some insider tuning experience: >>>> Please let me know if any of this info is blatantly wrong, seems wrong, might be wrong or just doesn't feel right. I am not trying to say I am 100% right, but hopefully this might stimulate some conversation.

Let's start with the ECM:
The ECM provides all the sensors in the car with a constant 5v. The sensors then relay info back to the ECM in V between 0 and 5V. The ECM understands this input and makes adjustments accordingly. This should hold true for everything from MAP to MAF to fuel level etc.

The stock 2 Bar MAP sensors therefor would be providing the ECM with a reading between 0 and 5V. The reading is effectively a pressure reading (or vac reading might be a better way to word it). If we assume that when the engine is not running the reading would be 0 and at full throttle it would be 5V, then at half throttle it would ready 2.5V. The MAP does not read commanded or actual throttle position, but the vac. reading would be in direct relation to throttle.

Here is where I will need a little help: The vac readings at these different voltage readings would be??

Let's use some round numbers:

Lets say that at full 5V the stock sensors are reading 23 PSI (I chose this because it is the max that an 07 GXP will read on the GXP). That would mean that 2.5V would be 11.5 PSI. Here is where the problem comes in:

When switching to the new 3 Bar MAP sensors all the math changes:
Now, at a full 5V (full throttle, WOT) the reading is now lets say 28 PSI. Now, at 2.5V we would be at 14 PSI. The pressure is a relation to the amount of air entering the engine. So if the ECM is seeing 2.5V, it doesn't understand that that means a different pressure / air volume. Therefore, it is telling the fuel system to input an incorrect amount of fuel. It would cause a lean condition since the computer would be seeing 2.5V and assuming it means 11.5 PSI and the corresponding volume of air, when in reality it is 14 PSI and an increased volume of air. Less fuel than should be going in to the engine.

This could be solved by tuning the ECM to understand the new figures. And perhaps that is possible with the Kappas. The tuner I have been talking with specializes in other GM vehicles and has a working relationship with Lyndon Wester. In the Full Size trucks, they are NOT able to change this. The problem arises with guys that are putting superchargers on the full size trucks and looking to get boost readings. In their case, the stock MAP is a 1 bar. They were trying to install 2 bar sensors and read them thru the OBD2 (ECM) and the trucks were running very poorly, especially at full throttle. When installing a secondary sensor and not running it to the ECM, but running it to a gauge like an aeroforce that can accept the same 0-5V signal, they were able to monitor the readings. I'm not sure they have worked all the bugs out yet, but that seems to work to solve some of the problems.

As I was discussing this with them, I started to think about our car and that this may also be an issue with out cars... so I tried to organize my thoughts (VERY difficult) into a thread that may make sense to some.

What do you think?

GJ

TomatoSoup · « **Reply #1 on:** July 12, 2011, 09:34:08 PM »

Well, the GMPP tune is designed to work with the 3bar sensors and so use the reading ranges they provide. It won't work (or not for long) with the older 2bar sensors and will throw codes and go into limp if you try to go WOT with the wrong sensors.

So if you are saying that the problems are occurring because the ECM isn't accounting for the different readings from the new sensors, I don't think your theory, err, "holds water".

Gentleman Jack · « **Reply #2 on:** July 12, 2011, 09:40:58 PM »

Quote from: TomatoSoup on July 12, 2011, 09:34:08 PM

Well, the GMPP tune is designed to work with the 3bar sensors and so use the reading ranges they provide. It won't work (or not for long) with the older 2bar sensors and will throw codes and go into limp if you try to go WOT with the wrong sensors.

So if you are saying that the problems are occurring because the ECM isn't accounting for the different readings from the new sensors, I don't think your theory, err, "holds water".

One would think that GM took this in to account. I would agree. What about the folks that then had a tune done "over" their GMPP tune? Is it possible the aftermarket tune does not take this in to account? Joe had indicated that many of the engine issues were folks that had a tune "on top of" the GMPP tune. In reality, the GMPP tune gets wiped out and a new tune gets loaded in. I am not trying to bash any tuners out there. I am trying to "brainstorm"

Does that hold any water?

tazz · « **Reply #3 on:** July 12, 2011, 10:13:24 PM »

The Entire GMPP tune never gets completely wiped out. This is because nowhere near all the tables are ever seen or touched with Vince, Lyndon or HPT tunes. One has to remember that there are over 600 tables that control fueling alone and we have less than maybe 20 tables? for fueling through HPT. That was the main reason before this last HPT update that most people used the based GMPP tune then changed parameters from there since there was not a table for the sensor linear adjustment to calibrate the new upgraded sensors but also the upgrades to the other tables that HPT has no control over.
Is this what your getting at that we are effectively raping and skewing the some tables to achieve a desired out come and if you are the answer is YES. Take the Dal's up until a few months ago it was common practice to rape the DAL table to achieve higher boost levels and now the consenses is we can raise boost levels by other means in addition to the DAL Table other than just by the Dal's.
Im by no means an expert but Ive been over on HPT for some time just learning what I can and they are learning more and more each day on how our ECM works and how the tables we do have interact with one another to get the desired results and it's complicated.
There was also a discussion on KR and AFR and how alot of tuners are commanding a richer AFR and that could be some of the problem since the LNF hates Richer fuel mixtures and actually shows more KR due to rich mixtures. Went on that no one has damaged a motor by running too lean and melting pistons or plugs for that matter but by KR which might have been caused by too rich of an AFR.

Arabas · « **Reply #4 on:** July 13, 2011, 02:41:37 AM »

although there is reason in your thoughts ( i know i know..this sounds weird

) i would be extremely shocked if the GMPP tune did not take into account the new 3bar sensors..after all their whole tune kit depends on these new sensors... there are too many assumptions on this theory to go on with it..
also, i know that Lyndon has experimented on these sensors, so he, at least, can not be wrong...
i have seen kappas with just a tune go kaboom.. for me these failures most probable cause is shitty gas, until further evidence..

Critterman · « **Reply #5 on:** July 13, 2011, 08:59:49 AM »

Touch Base with Dave, I know it is apples and oranges but the supercharged LN5 uses a 2 bar instead of the stock 1 bar sensor.

JimmyBaja · « **Reply #6 on:** July 13, 2011, 10:54:48 AM »

Correct me if I'm wrong but I believe a constant rich condition would lead to breakdown of cylinder wall lubrication leading to premature ring wear wich would lead to low compression... the end result sounds familiar.

tazz · « **Reply #7 on:** July 13, 2011, 11:02:17 AM »

That also will happen.

HAMMER DOWN · « **Reply #8 on:** July 13, 2011, 11:45:43 AM »

Just thinking out loud. Is their a why to find the build date of the motor? With no real common denominator. Wondering if the failures are do to a bad patch of part ie; pistons, piston rings, O-ring & seals.

Mike

Brazen17 · « **Reply #9 on:** July 13, 2011, 04:04:33 PM »

Quote from: HAMMER DOWN on July 13, 2011, 11:45:43 AM

Just thinking out loud. Is their a why to find the build date of the motor? With no real common denominator. Wondering if the failures are do to a bad patch of part ie; pistons, piston rings, O-ring & seals.

Mike

That sounds like a reasonable possibility. Does anyone know if the Cobalt 2.0 turbo are having any similiar issues?

Brazen17 · « **Reply #10 on:** July 13, 2011, 04:06:35 PM »

As I mentioned before I am seriously thinking of Trifecta or Westers tune because, although it will void the warranty, I think it will, ironically, be safer.

elff · « **Reply #11 on:** July 13, 2011, 06:24:10 PM »

Brazen

You aren't off the mark.
After seeing the amount of knock in the GMPP tune, I believe I am safer with the 2871 and the DDM tune.

GJ
The GMPP does alter the "For lack of a better word" Operating system of the ECM which accounts for the 3 bar sensors. So I don't think that is the case, but while the performance is decent, the GMPP tune makes tuners go WTF?? Why did they do that?

tazz · « **Reply #12 on:** July 13, 2011, 06:36:22 PM »

You could also splash in 2 gals of E85 every tankful you will rid yourself of any knock.

elff · « **Reply #13 on:** July 13, 2011, 11:39:36 PM »

One other note. HPT has a lot more tables available to tweak on the 2.4L engine.

kennysabarese · « **Reply #14 on:** July 15, 2011, 02:56:17 AM »

People who were tuned before GMPP came out are running more than the 2.5bar sensor can read, but those guys seem to be just fine, and make the same power as the GMPP tuned guys.

So unfortunately, I have to disagree that it has anything to do with the MAP sensors.

HAMMER DOWN · « **Reply #15 on:** July 15, 2011, 09:23:29 AM »

I'm still leaning towards part quality &/or modification of GMPP tune.
What I posted in other thread.

GMPP here, installed around 20k, Hit & max out the OEM Boost gauge at 23psi many times when I'm drive my 07 GXP. Now have over 65k with no problems what so ever. Other mods are; Hahn, BOV & Hoses, Hahn IC & modded OEM intake box. http://www.kappaperformance.com/forum/index.php/topic,1606.0.html.

Joe thinks it may have to do with a modified GMPP tune, Not GMPP tune alone. From Joe's post above "I've been watching this also and it seems that most of the LNFs I've seen that have bad turbos or crapped out were the ones with the GMPP upgrade and then a tune on top of that."

Must be another key to this puzzle we are missing.

Mods could you join these to threads:

This one & http://www.kappaperformance.com/forum/index.php/topic,7479.0.html

Thanks, Mike

kennysabarese · « **Reply #16 on:** July 15, 2011, 12:27:52 PM »

Quote from: HAMMER DOWN on July 15, 2011, 09:23:29 AM

I'm still leaning towards part quality &/or modification of GMPP tune.

I wouldn't disagree with you, I have a modified GMPP tune and it's not too great, I keep going back to the standard GMPP tune and the car works fine.

But to be fair, I haven't had the time to really troubleshoot the tune, and I'm going to try to pass emissions when I get home so I have to make sure I don't have any codes or CEL, so I won't be really getting into my tune until September probably.

tazz · « **Reply #17 on:** July 18, 2011, 08:51:50 PM »

Whats wrong with it?
Lyndon should be able to fix it for you.

HAMMER DOWN · « **Reply #18 on:** July 19, 2011, 03:03:30 AM »

I change my spark plugs & sense I have one of the highest mileage 2.0L turbos with the GMPP tune. I did a compression test, miles 65k, from front to rear, 170, 170,165,170psi.
Mike

kennysabarese · « **Reply #19 on:** July 19, 2011, 03:46:18 AM »

Quote from: tazz on July 18, 2011, 08:51:50 PM

Whats wrong with it?
Lyndon should be able to fix it for you.

I keep getting codes, and limp mode. Lyndon says I have a leak, but I go back to GMPP and all the codes go away. Maybe I have hardware issues that only show themselves when at higher than GMPP boost levels.

But like I said, I just haven't had the time to play with it, and I don't want to risk problems and limp mode while on the track. I pay way too much for track time to waste it in the pits resetting codes.

Gentleman Jack · « **Reply #20 on:** July 20, 2011, 01:42:55 AM »

Quote from: Kenny on July 19, 2011, 03:46:18 AM

I keep getting codes, and limp mode. Lyndon says I have a leak, but I go back to GMPP and all the codes go away. Maybe I have hardware issues that only show themselves when at higher than GMPP boost levels.

But like I said, I just haven't had the time to play with it, and I don't want to risk problems and limp mode while on the track. I pay way too much for track time to waste it in the pits resetting codes.

Kenny,

you and I both. stock tune, never throws a code. Wester's tune, I will get a MAF code and temp. limp mode. Doesn't happen all the time, and is less repeatable with a reflash, but still happens. That's pretty much the whole reason why I ordered the HPTuners from DDM today. I just have to get to the bottom of it.

GJ

kennysabarese · « **Reply #21 on:** July 20, 2011, 03:40:36 AM »

cool. good luck

Gentleman Jack · « **Reply #22 on:** July 20, 2011, 09:45:38 AM »

Quote from: Kenny on July 20, 2011, 03:40:36 AM

cool. good luck

This sounds strangely like " yeah, GJ, I've been there. I have no friggin clue what is wrong and you have no chance in hell of figuring out what is wrong with your car either. These cars are great, but they don't make any sense what so ever. Your screwed, and will just have to live with the problems. Good luck"

Arabas · « **Reply #23 on:** July 20, 2011, 09:55:43 AM »

Quote from: Gentleman Jack on July 20, 2011, 09:45:38 AM

This sounds strangely like " yeah, GJ, I've been there. I have no friggin clue what is wrong and you have no chance in hell of figuring out what is wrong with your car either. These cars are great, but they don't make any sense what so ever. Your screwed, and will just have to live with the problems. Good luck"

i m sure Kenny was just laconic in saying "I hope you find the problem buddy"

Gentleman Jack · « **Reply #24 on:** July 20, 2011, 09:56:47 AM »

I just learned a new word.

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Author Topic: engine issues: the problem could be.... (Read 15160 times)