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