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Advanced SCT Datalogging


This section assumes that you have you wideband connected (if equipped), calibrated in livelink to match your gauge, and you are familiar with datalogging using SCT products (Xcal2, Xcal3, Livewire, or raptor).  Check out our starter guide here.  WOT datalogging and data analysis will be discussed first with more to come in the future.

WOT (Wide Open Throttle) Datalogging

Always choose the parameters with capital letters if there is an option because they are DMRs (direct memory read) and respond a little quicker than the lower case options. The parameters you will need to log will follow.  Logging extra unneeded parameters is not advised because more parameters will decrease the update speed.  I added a few of the possible names because sometimes they are called different things on different cars.  You may have to hunt around for some of the parameters, but the setup is fairly logical.  If you come across a name I've missed or is different please email me at joe@tricktuners.com and I'll add it to the website.

This is a general list.  For specific issues, and some types of tuning, different parameters may be logged.

1. ECT, Engine Coolant Temperature, or Coolant_temp.  Probably in the environment folder.

2. IAT, Intake Air Temperature, IAT 1+2, IAT upstream and downstream, ACT, Air Charge Temperature.  You will only have 2 IAT options if the vehicle was equipped with a supercharger when stock like the terminators and lightenings. Probably in the environment folder.

3. RPM, Engine rpm, probably in the misc folder

4. Battery Volts, VPWR, probably in the misc folder.

5. Throttle position, TP absolute, PPS, pedal position sensor, probably under misc.

6. Load, Engine Load, % Load, probably under the maf folder.

7. MAF Counts, maf ad counts, probably under the maf folder.

8. Fuel Pump Duty Cycle, Returnless fuel pump duty cycle, probably under fuel pump, or returnless fuel pump.

9. Pressure drop across injectors (only on cars with a returnless fuel system). Probably under fuel or injectors.

10. Spark, timing, probably under spark or engine.

11. Spark source, probably under spark or engine.

12. Analog 1 for wideband.  Under analog, use the correct function and make sure it matches the gauge!

13. STFT, short term fuel trim bank 1 or 2, only one needed because they are the same at WOT.  If you take this value and multiply it by 14.64 it will give you the air fuel mixture commanded by the ecu and should match the wideband data. Ex. 0.82=12:1

Secure the laptop in the car and setup livelink.  Put the mouse over the green square so you can just hit the button to start datalogging just before the WOT run.  Use 3rd  gear on the track, or 4th gear on the dyno.  Start at 2000rpms hold it there for a second or 2 then punch it quickly.  Pull to near redline but LET OUT if the AF is lean, or detonation is encountered!  Stop the datalog when you are stopped. 

Data Analysis with Excel

After you collect your data (Getting started with datalogging) you need to open the .csv file in Excel. These steps will help you sort and analyze your data.

1. Click on the .csv file that you saved. If the computer does not recognize the file type, right click on it and select Open With, then select Excel.

2. Press CTRL and A at the same time to highlight all the data. Right click and Copy.

3. Click Insert (on the title bar) and insert a worksheet.  This may not be necessary if there are already multiple worksheets.

4. Right click on cell A1 and select paste. This copies the original data, while also protecting the it, during data manipulating for analysis.

5. Highlight the first row of the descriptions by holding the mouse over the "1" on the top left until the mouse turns to an arrow pointing to the right.

6. Right click and select Format Cells. Click the Alignment tab at the top and select Wrap Text. This will make the headings easier to read.

7. Click on cell A2 and then click on Window on the title bar. Select Freeze Panes. This will keep the header at the top while manipulating the data.

8. The sort function can be very useful. Highlight all the data you would like to sort (or press CTRL A) and go to Data, then Sort.  You may need to check the box that says my data includes a header row.  It can be very useful to sort by TP (throttle position) so you can cut out all the non-WOT data.  When you cut data make sure to highlight the entire row by clicking on the row number and dragging down.  Rt click then hit delete.  If you just delete the cells there will be a huge blank spot in the data.  Once the data is setup, resort by time so itís all in the normal order. Its also very easy to see if you have a pegged maf, injectors, or fuel pump by sorting for that option and looking at the highest value.

14. Graphing is another very useful function. The easiest way is to analyze only one WOT run at a time (can be 1/4 mile style). By clicking on the column header you can select the entire column instead of highlighting the actual data.  This is very helpful when looking at large data sets.  Selecting time first is a common way to analyze the data. The far left column will be come your X value and all the other columns will become different y series that all use the same x column.  Some things I usually look at are MAF counts, FP duty cycle, RPM, and pressure drop across injectors vs time. There are many other things that can be useful to graph depending on what you are looking at. Hold down CTRL and select the headers (or the raw data) you would like to graph. Then select the chart wizard (bar graph looking thing). Select the XY scatter chart type and then the curved line one (middle on left). I usually just press finish instead of adding title, etc, but feel free to label the chart and the axis, add colors, etc. Many times it's best to right click on a point of the rpm graph and select "format data series", then go to the Axis tab and select secondary axis. This will put the rpms on their own axis to help view the other data better.  Once you understand these basics you can analyze all your data with this method. 

  Sometimes it's useful to multiply an entire column by something like 10 or 100 to put it on the same scale as another parameter you are graphing.  One of the limits of using excel is that you are limited to using only 2 axis.  To multiply a column by something, rt click on the column next to the one you want to manipulate, and click insert.  Label your header and in the cell below the header, press = then click on the cell you want to multiply (should be directly to the left or right and not above or below the cell you are in), then click * then your value.  Ex. =C2*10.  Press enter.  Hold the mouse over the bottom right corner of the cell you just typed in until the mouse changes to a +.  Double click and the entire column will populate with your formula.  You can now use your new column in your graphs.  You can see that this was done on the example below to add fuel pump DC to the same axis as pressure drop.  You could also multiply it by 100 instead, and raise the rt scale to 0-100. (that would probably make it easier to see)

  If you have very long datalogs (generally above 15-20 min) excel will peg at the 69,000 row limit (unless using excel 2007).  One way around this is to highlight the data in livelink and then choose file, save current view.  This can also be useful for cutting out just the WOT data.  Your data manipulation will be faster with less data too.  Update: as of 2010 I now primarily use SCT livelink for data analysis.  It works really well as long as the datalogs are less than about 5-7 minutes.  I like it because I can switch between what data is graphed to try and determine what is causing the specific issue.

 Watch it in a Slideshow

Here are some examples of common problems that can be detected using this graphing method.

Pegged MAF

You can seen the maf counts peg at 1024. Not good! The worst thing is that a shop told the customer that the maf was not even close to pegging and the tune was safe. Sometimes its best to "see for yourself".

Going Lean due to Pegged MAF

This not safe!!! You can see the maf peg in the previous picture and then the AF goes WAY lean.

Fuel pump nearly pegged

This is the same car with the pegged maf. You can see that the fuel pump is about done too. (this calibration pegs at 0.5). Not good!

This shows a pegged fuel pump.

The FP DC is multiplyed by 10 to put it on the same scale as fuel pressure (rt side). You can see that the fuel pump hits 10 (1.0 duty cycle = 100%) then the pressure starts dropping as the rpms increase. Not safe!

Battery Voltage Drop




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Last updated: 03/07/10.