Series III 3800 SC Engine Tuning

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Series III 3800 SC Engine Tuning

Tuesday, 29 April 2008

Well, I have received my HPTuner's scan tool, and have started to tune the GTP. After digging around through all the sites, and good stuff, it seems like some of the information I have found is just out-dated, incorrect for currect versions, different cars then mine, or just plain wrong. On this page, I am going to show you some of the things I have done, and am currently doing to tune my 2004 Grand Prix GTP.

Now, this engine is different from the previous year and models. This is the new Series III 3800 3.8L V6 Supercharged Engine by GM. This engine is not only used in the Grand Prix GTP, but also in many others. For this reason, I will be just showing you things from my Grand Prix, and hope you can learn something, help me in someway if I am incorrect, or help yourself tune a little more.

While digging around the HPTuner forums, most of the posts are for our V8 big brothers, Corvette, GTO and so on. Well, they have not forgotten about us V6 people. While some of the options are different, the basic fundimentals are still there.

First of all, I started by downloading my current tune, I will call this my Stable tune. It is from a DHP 1.0 PCM, and it works alright. The car does not get pissy, or piss poor performance from this tune, and it's what I am currently using. Alright, open the VCM Editor and make a full Read Entire from your ECU. This might take a while, mine seems to only work if it is -NOT- in High Speed Mode. So it took me 15 minutes to download the ECU programming. Once you have this, make a copy of it, store it on the server, just keep a version of this in a safe place at ALL times. It may not be the best, but it might just get you home incase you really foul things up.

Now, run the VCM Scanner Suite program, and lets setup a histogram to log the MAF and LTFT. On the current version of the software, 2.22.3035.28206 we have this available to us from the base install. So click on the Configure Histogram button, and then click on the number 8 in the list on your left. Click on the Import Histogram folder icon in your top left corner and Import the File Named: MAF LTFTs if you are showing file extensions it will be: MAF LTFTs.hst Alright, open that and Histogram 8 should have some data in it, click on the Commit Changes arrow on your toolbar and then close that Histogram Configuration window. Now, click the number 8 Histogram. You should have something like the photo below:

Empty MAF

You should now configure your Table Display. Make sure you are logging your MAF Hz. I have attached what my table looks like for this tuning step. If I am missing something you think would make it easier for me and others, just let me know!

Table Display

Now, switch back to your VCM Editor, and open the ECU file that you got while doing a Full Read. Click on Engine -> Fuel Control -> Power Enrich -> PE Enable TPS Hot. It should look something like the shot below:

PE TPS Hot

Lets make these all 100% so that we never enter PE mode. If you enter PE mode the LTFTs will lock at the last value before entering PE, this is what can make your engine blow up, if it locks at something REALLY rich, or even slightly lean on high boost. Select all the values in the table, you can click on the top left corner button to select all cells. In the top text box with the % to the right of it, type in 100 and click the = button. This will change them all to 100%. Now, go to Engine -> Spark Control -> Spark Advance -> High Octane and select all cells, right click and Copy. Now, in the same place open Low Octane, select all cells and just do a normal Paste. This will basically make them the same. You want to do this, because from what I have read, when your not in PE mode, the ECU uses the Low Octane table. You want to keep this the same as your High Octane table when you go back into PE mode, the values will pull from the real High Octane table, and will match what your scans found.

High and Low Octane

Now that you have made those changes, do a -SAVE AS- and save this to a new file! Then write the changes to the ECU. At first I did a Write Entire, but since you also have Write Calibration Only, I did dig into the Help files, and found that you only need to do a Calibration Write. So, do just that, click Flash -> Write Calibration Only and let it go. I also do this in -non- high speed mode, takes me ~2 minutes.

Now, lets start the car and let the engine warm up to the average operating temprature, and start the VCM Scanner. Once you have values start to populate the histogram, click to Histogram 3 and make sure you are on the Average Values, just click the large A on the top right of the Histogram window. Click to number 8 and you will see a few values moving around slowly. Start to drive around, you will notice that you have much less power with PE mode disabled. Don't floor the car everywhere you do, try to drive normally, but do try to get some higher RPMs, maybe around 2000, 2500, or 3000 but try to get to them, and back down from them in a smooth motion as to gather as many cells in your table as possible. You can switch to Histogram 3 to see your data. Also, keep an eye on KR, Histogram 2, just to make sure you are safe at this point from KR. You should try to drive around for about an hour. I've done mine for around 45 minutes to an hour, and I usually have to get two trips.

After that, stop and save your VCM Scan before you power off the car. It should look a little something like below for the Histogram 3:

VE Long Term Trim

And something like this for the Histogram 8 that we setup:

MAF LTFT

Now we need to copy this data into our tune to adjust it some. Open your VCM Editor, and then open the new tune that your car is currently running. Open the Engine -> Airflow -> MAF Calibration -> Airflow vs. Frequency now select all of the cells in the table using the upper left corner button, right click inside one of the cells and do a Paste Special -> (Multiply by % OR a Multiply by % - Half) This depends on how far off your values really are. If they are really off, you probably will not hurt it doing a plain Multiply %, if they are pretty close to zero, do a % - Half. This should help smooth your MAF Output Frequency. You may need to hand smooth the table, or you can try selecting all the values again, and then clicking the smooth table button once. The smooth table button is the red, yellow and orange 3D button on the top of this window. Hover over it and the tooltip will say "Smooth Selection".