Starting a new tune - MAF Tuning - What am I missing?

[wetcoast]

As a lot here seem to profess, I'm new to tuning. I've done a ton of reading books, watched the tuning videos, read on this web site a lot.

I'm stuck and was hoping someone might be able to nudge me over a bump I'm currently running into.

Here are the files I'm working with:

2009 CTS-V Modified No Cats, ID850's, PE Edited, Delete TM, Fans (MAF Tuning).hpt
CTS-V Metric.cfg
June 30, 2014 (Open Loop) 1.hpl

I've verified that I'm logging the lambda error, MAF only, open loop.

The issue that I'm running into is that when I adjust the MAF airflow vs frequency according to the lambda error that I'm seeing and re-load, I end up with the same lambda error as if the change to the airflow isn't even registering. I've tried this twice with the same results.

What am I missing?

TIA,
Chris

[BigDaddyCool]

Use AFR Error for maf tuning, much better.........

[wetcoast]

Use AFR Error for maf tuning, much better.........

Why?

Isn't AFR error the same percentage difference from stoich as lambda error?

[Force]

Maf lambda error tuning is fine. Have you got your tune file so that we can see it.

[Force]

If you have a look at your primary table in the bottom left corner beside ecm you have too many bits (26) in the primary table. bring it down to 24 or less by deleting some of the info in your primary table that you don't need to scan. It buggers up the resolution. You can get rid of short term fuel trims as you are not interested in those.
I gave your scan a run and your lambda error is -37 at idle so there is something wrong for sure. If it was that rich the engine would not run. I can t see all your scan either as my scanner is set up differently for a E40 ecm.

[wetcoast]

If you have a look at your primary table in the bottom left corner beside ecm you have too many bits (26) in the primary table. bring it down to 24 or less by deleting some of the info in your primary table that you don't need to scan. It buggers up the resolution.

Will do and thanks for this.

I was over 24 because of the HP TUners help file that I mentioned here http://www.hptuners.com/forum/showth...l=1#post354333 where it appears as if the E67 ECM can log up to 28 bits without loosing resolution.

I'll try again but I can't see it getting me past this current issue.

[Force]

oh ok, maybe e67 is different with resolution. put up your tune file onto here.

[wetcoast]

oh ok, maybe e67 is different with resolution. put up your tune file onto here.

Thanks!

My tune is on the first post.

[wetcoast]

One thing that is strange to me is that I've added a New Era cold air kit which is supposed to pull in cooler air but my measured Lambda and subsequently Lambda error is indicating that the MAF table is commanding a really rich fuel ratio. Shouldn't it be too lean if the cold air kit is bringing in more air?

[umrjmac]

If the intake tract ahead of the MAF sensor has changed, then the flow of air across the sensor has changed. That is going to be why you have to recalibrate the MAF table. It doesn't have much to do with more/less air...but more with how much air really corresponds to a particular MAF Hz with this particular intake topology (which changed).

If you are curious about change in IAT, I would look at IAT rather than Lambda error.

[Force]

when I open up the 2 files in your first post they both come up as scanner configs. They don't seem large enough for a tune file. I am scratching my head there lol. sorry looking at the wrong there. I have it now.

[wetcoast]

If the intake tract ahead of the MAF sensor has changed, then the flow of air across the sensor has changed. That is going to be why you have to recalibrate the MAF table. It doesn't have much to do with more/less air...but more with how much air really corresponds to a particular MAF Hz with this particular intake topology (which changed).

If you are curious about change in IAT, I would look at IAT rather than Lambda error.

That makes sense but if I'm seeing a rich AFR when the commanded AFR is stoich, would that not indicate less air than the stock setup?

[umrjmac]

It would mean that your car thinks that there is more air flowing for a given Hz value than what is actually entering the engine. Since it thinks that there is more air, it squirts more fuel, yielding your rich condition.

Think of a twisty water slide at an amusement park. As you enter a turn, you are pressed up against one wall or the other. You don't simply sit in the middle of the tube through turns. Air is going to be moving in a similar way. As you add or remove bends from the path, you create areas of higher and lower pressure within the tube. Now think about the MAF sensor itself. If you look at it, there will be some small number of thermally resistive/heated elements. They are at fixed points on the maf, typically near the center of the housing. A MAF sensor can only really "spot measure" particular points in the air path, use the measured value and a lookup table (your MAF calibration) to tell the computer how much air mass it expects to have passed through it.

You can see how adding or removing a turn from the pipe would affect the flow of air across the sensitive bits of the sensor, which in turn would necessarily change the calibration required to appropriately approximate the air flow through the sensor. You can also affect the air flow by adding or removing obstructions. For example a bellows-like accordion can add turbulence. Some MAF sensors come with a screen on the front to try to smooth out the flow of air across the sensor.

If you observed this behavior without changing the intake tract at all, then your conclusion would be valid. Weather would be a factor as well. A dirty MAF sensor could also be a culprit. O2 sensors being out of calibration or bad could be a factor.

Does that help?

Edit: Really that is a long way of just saying that your MAF calibration has to be accurate for your intake tract. Since you changed the latter, you need to update the former.

[wetcoast]

It would mean that your car thinks that there is more air flowing for a given Hz value than what is actually entering the engine. Since it thinks that there is more air, it squirts more fuel, yielding your rich condition.

Think of a twisty water slide at an amusement park. As you enter a turn, you are pressed up against one wall or the other. You don't simply sit in the middle of the tube through turns. Air is going to be moving in a similar way. As you add or remove bends from the path, you create areas of higher and lower pressure within the tube. Now think about the MAF sensor itself. If you look at it, there will be some small number of thermally resistive/heated elements. They are at fixed points on the maf, typically near the center of the housing. A MAF sensor can only really "spot measure" particular points in the air path, use the measured value and a lookup table (your MAF calibration) to tell the computer how much air mass it expects to have passed through it.

You can see how adding or removing a turn from the pipe would affect the flow of air across the sensitive bits of the sensor, which in turn would necessarily change the calibration required to appropriately approximate the air flow through the sensor. You can also affect the air flow by adding or removing obstructions. For example a bellows-like accordion can add turbulence. Some MAF sensors come with a screen on the front to try to smooth out the flow of air across the sensor.

If you observed this behavior without changing the intake tract at all, then your conclusion would be valid. Weather would be a factor as well. A dirty MAF sensor could also be a culprit. O2 sensors being out of calibration or bad could be a factor.

Does that help?

Edit: Really that is a long way of just saying that your MAF calibration has to be accurate for your intake tract. Since you changed the latter, you need to update the former.

Thanks for the clarification. I'm starting to get it. I guess if I really wanted to see if the net effect of the CAI is I could put the stock intake back on and measure Lambda error.

Still can't figure out why when I multiply the MAF Hz vs. air mass by my lambda error and retest that I don't get different results.