I originally posted this in the B8 S4 “Performance Expectations” thread, but I can’t update that post. I recently updated this on the other site with values from VCDS version 15.7.1 and some other details, so here it is here. If anyone has input on changes, I’m open. Just let me know. I know this is long, but it’s meant to walk someone through logging step-by-step.
Original post here (good post to go along with this): http://audirevolution.net/forum/index.php?topic=2656.0
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Several people have asked about logging their vehicle, so I put together a “how to” on logging with the Ross-Tech VCDS software and cable (VAGCOM). Logging is critical to understanding how your car is performing, and even more so if you are tuned. There are several parameters that can be logged that will give a good indication as to how your car is running, and if there are any problems. This “how to” guide will cover how to perform basic performance logging, and also how to interpret some of the results.
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First, a few things:
*Every version of Ross-Tech software is slightly different. In terms of logging, the only real difference is the location number associated with each logging parameter. The name of the parameter will be similar from version to version, but the associated location number may be different. I am using version 12.12.1 in the screen captures, but I have updated the parameters from version 15.7.1 (updated 10/8/2015). Regardless, your version may be slightly different.
*One of the key things people like to log is requested and actual boost. In recent versions of the Ross-Tech software boost is not displayed as an absolute value. Some conversion and calculation is required. This is covered in the next post.
*While there are others ways to log a vehicle, this only covers using the full version of Ross-Tech software with their VCDS cable.
*Logging must be done with Windows software. That can be XP, Vista, Windows 7 or 8. Doesn’t really matter. An Apple/Mac that runs Windows will also work (Boot Camp, Parallels, etc.).
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Getting Started
Step 1: Plug the Ross-Tech VCDS cable into the OBDII port under the dash on the driver’s side.
Step 2: With the car on, launch the VCDS software.
*Note: The car can be in the ON position or running for steps 1-11.
http://i570.photobucket.com/albums/ss146/jran76/VCDSstart_zpse122c8c4.jpg
Check for Fault Codes
Step 3: Before you start logging, ensure there are no fault codes. Press the “Auto-Scan” button on the VCDS main menu.
Step 4: Once in the Auto-Scan section, press the “Start” button to scan for codes. The scan will take a few minutes as it scans all modules. If there are faults, I would recommend saving the scan results (copy/paste, save, print), and then clear the faults with the “Clear all DTC’s” button. Once this is done, “Close” the Auto-Scan section, and return to the main menu.
http://i570.photobucket.com/albums/ss146/jran76/VCDSautoscan_zps2e94133c.jpg
Logging Setup
Step 5: Under “Select Control Module” press the “Select” button.
http://i570.photobucket.com/albums/ss146/jran76/VCDSstart_zpse122c8c4.jpg
Step 6: Under the “Common” tab press the “01-Engine” module button.
http://i570.photobucket.com/albums/ss146/jran76/VCDSmodule_zps5dbd824b.jpg
Step 7: In the Engine Controller module, press the “Adv. Meas. Values” button to access the logging section.
http://i570.photobucket.com/albums/ss146/jran76/VCDSengine_zps1564e92c.jpg
Step 8: Select the “Ambient Air Pressure” value from the parameter list. Record the value displayed for future reference, and then uncheck the box. The ambient pressure value will be used later to calculate boost related values.
http://i570.photobucket.com/albums/ss146/jran76/VCDSambientairpres_zps1dceb3fa.jpg
Step 9: Select the parameters you would like to log from the list.
*Notes:
-VCDS will let you select a maximum of 12 parameters, or 10 parameters if you use grouping (which is a must for good logs as we’ll cover below). So, concentrate on the parameters that are most important for this particular logging session. Fewer parameters logged will yield higher resolution logs.
-For general performance logging, I recommend the following parameters, but you can pick the appropriate parameter for your needs from the list:
Location Number- Parameter Field- Units- (details)
002- Accelerator position- in %
009- Charge air pressure specified value in hPa (specified boost+ambient air pressure)
018- Engine speed- in RPM
089- Air mass- in kg/h (intake)
186- Ignition angle; actual- in degrees
188- Intake air temperature- in degrees C
190- Intake manifold pressure; absolute- in hPa (actual boost+ambient air pressure)
418- IGA_AD_KNK[0]- in degrees- (knock detection/timing pulled on cylinder 1- Just pick 2 Cylinders to log)
419- IGA_AD_KNK[1]- in degrees- (knock detection/timing pulled on cylinder 2- Just pick 2 Cylinders to log)
420- IGA_AD_KNK[2] -in degrees- (knock detection/timing pulled on cylinder 3- Just pick 2 Cylinders to log)
421- IGA_AD_KNK[3] -in degrees- (knock detection/timing pulled on cylinder 4- Just pick 2 Cylinders to log)
422- IGA_AD_KNK[4] -in degrees- (knock detection/timing pulled on cylinder 5- Just pick 2 Cylinders to log)
423- IGA_AD_KNK[5] -in degrees- (knock detection/timing pulled on cylinder 6- Just pick 2 Cylinders to log)
540- RFP_AV (bypass valve percentage)
http://i570.photobucket.com/albums/ss146/jran76/VCDSloggingfields_zps77230125.jpg
Step 10: Save the parameter list so you can easily access it at a later time by clicking the “VCDS” icon in the top-left corner. Name the file “performance” or similar. If you have parameter files for other types of logging, name them appropriately.
http://i570.photobucket.com/albums/ss146/jran76/VCDSloggingfieldsave_zpsb4c2abf2.jpg
Logging
Step 11: This step is very important for capturing good logs. Press the “Turbo” button, and check the “Group UDS requests” box at the top of the screen. This will speed up the logging, and also group all 10 fields to the same timestamp. This is the only way to get useful logs (otherwise, each parameter will have a different timestamp).
http://i570.photobucket.com/albums/ss146/jran76/VCDSlog_zps04769222.jpg
Step 12: Press the “Log” button to initiate the logging session. This will not start the actual logging process
*Note: Your car should be running if it is not already.
Step 13: When you are ready, press the “Start” button. This will start the actual logging process.
*Notes:
-Logging should be performed in a controlled area where you can safely reach 85-90 MPH. The drag strip or dyno are the best options, but in places like Texas there are some pretty safe places to do this on the road (I do it late at night in traffic free areas with 70+ MPH speed limits).
-Logging runs should capture a full 3rd gear pull at a minimum. 4th is probably a little better, but that should only be done at the drag strip or on a dyno. A full pull is around 3000 RPM to 7000 RPM. This can be tricky on a DSG car because you need to avoid triggering the kickdown switch at lower RPM’s. Play around with what works best, but the sooner you can get to full acceleration the better.
-When logging, the A/C and radio should be OFF, the windows UP, car IN dynamic mode if available, and traction/ASR OFF (hold traction button for at least 5 seconds to turn both off).
-Logging should be done on a flat surface, and if done multiple times it should be done at the same location and in similar conditions if possible. This makes comparing data more accurate.
http://i570.photobucket.com/albums/ss146/jran76/VCDSlogstart_zpsb7d252fc.jpg
Step 14: Once you have captured the needed logs, press the “Stop” button to stop the logging process, and “Done, close” when finished. The logs will be saved to the Ross-Tech/VCDS/Logs folder as a .CSV file (typically on the C:/ or wherever the Ross-Tech software is installed). It can be opened with Excel or similar.
http://i570.photobucket.com/albums/ss146/jran76/VCDSlogstop_zps68e72dfe.jpg
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That is it for capturing basic performance logs. Below I cover some of the basics in regards to interpreting the logs.
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In addition to logging the basic performance parameters listed above, VCDS gives the option to log many many other things.
*Some examples:
-If you are experiencing timing being pulled due to engine knock detection, you may want to log knock on each individual cylinder instead of just the 2 covered above. In that case you would want to log something like: accelerator position, engine speed, ignition angle; actual, and IGA_AD_KNK[x] on all 6 cylinders. Those 9 parameters may point to an issue with a specific cylinder.
-As you can see, accelerator position and engine speed are really needed every time so you have some reference point in the logs. Intake air temperature is also good to log as it will give a good idea on the conditions.
-More fields and examples are below (updated below).
Update with additional fields:
Misfires:
If you are experiencing misfires, you may want to log misfires on all 6 cylinders to see where the problem is coming from. In that case you would want to log accelerator position, engine speed, misfires all cylinders, misfires cylinder X on all 6 cylinders. These 9 parameters may point to an issue with a specific cylinder, or a more general problem.
Some (low number of) random misfires that DO NOT result in a fault code are fairly normal. I see it on most 3.0 TFSI engines stock or tuned. With that said, Audi has dumbed down the misfire reporting threshold, so it is possible misfires could be causing a performance issue, but also not trigger a CEL. I don’t have an answer on what constitutes a real problem… Maybe others can chime in. In the most basic sense, if you see a CEL due to misfires, there is definitely an issue. If you see a low number of misfires and no CEL, it may be normal. If you see a high number of constant misfires, but no CEL, blame Audi for dumbing down the threshold and try to figure out the problem.
251- Misfires all cylinders per 1000 rpm 0
253- Misfires cylinder 1 per 1000 rpm 0
255- Misfires cylinder 2 per 1000 rpm 0
257- Misfires cylinder 3 per 1000 rpm 0
259- Misfires cylinder 4 per 1000 rpm 0
261- Misfires cylinder 5 per 1000 rpm 0
263- Misfires cylinder 6 per 1000 rpm 0
Lambda/Air:Fuel/EGT:
Lambda or Air:Fuel ratio is important to understand for a couple of reasons. The most basic is to ensure your engine tuning is optimal. This is obviously more important with aftermarket (non-OEM) tuning. If you want to see what “normal” is, log your car with the stock tune, and the specified values will give you a pretty good idea for different scenarios. Assuming fueling is sufficient, specific and actual should be fairly close. If the actual number is higher than the specified value, you will start running into issues (not good).
On that note, if you are running E85 or the fuel system near maximum capacity, it is a good way to determine if fueling needs are being met. Again, E85 or if you are mixing E85 with regular gas, could present an issue on the stock fuel system. E85 has (about 33%) less energy per part compared to regular high octane fuel, so it takes roughly 33% more of it to run your vehicle. This can tap out the stock fuel system pretty quickly if too much is used. To run strait E85, and upgraded HPFP would be required. The advantage of E85 is the higher relative octane (close to the equivalent of 105 octane).
020- Exhaust temperature 1 bank 1 460.0 ∞C
021- Exhaust temperature 1 bank 2 459.5 ∞C
238- Lambda probes actual; bank1 0.9971
239- Lambda probes actual; bank2 1.0049
244- Lambda probes specification; bank 1 0.9971
245- Lambda probes specification; bank 2 0.9971
246- Lambda probes specified; bank1 0.9971
247- Lambda probes specified; bank2 0.9971
(note that 244-247 seem to be the same thing, the specified Lambda value, so logging one is likely sufficient).
Table to convert Lambda to Air:Fuel ratios:
http://i570.photobucket.com/albums/ss146/jran76/LamdaVsAFR_zpsj6s7ctd1.jpg
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Understanding the Logs
Accelerator position (%): Pretty self explanatory. In terms of performance logging, we typically want to look at what the car is doing under wide-open throttle (WOT). On most cars this is in the 93-95% range. It is perfectly normal for the car NOT to hit 100%. The car will adapt to the given range on each vehicle for accelerator and throttle positions.
Engine speed (RPM): Again, pretty self explanatory. This will give a good reference point in the logs when the car is at maximum performance/higher RPM’s. Like WOT, the best indicator of performance is going to be what the car is doing at higher RPM’s; say 3000-7000 RPM.
Charge air pressure; specified value (hPa): This is essentially what the ECU is requesting in terms of air pressure or boost in the case of the B8 S4 engine. This value is in hPa, and needs to be converted to PSI for more common interpretation. You also have to subtract the ambient air pressure to get the actual requested boost number.
*1 kPa=10 hPa
*1 hPa=0.014503774
So, to calculate the requested/specified boost:
Requested boost= (Charge air pressure; specified value hPa) - (Ambient air pressure kPa x 10) x 0.014503774
*On a stock tuned car, this value will be in the 12 PSI range max. Any boost over this amount will trigger the bypass valve, and be bled off.
*On a tuned car, this value can be as high as 17-18 PSI. The tuned cars request more boost than is possible to ensure there is no bypass. The goal of a tuned car is to use all the boost available without opening the bypass valve.
Intake manifold pressure; absolute (hPa): This is the actual amount of pressure in the manifold where the specified is the requested. So, like the specified value, it needs to be converted to PSI, and subtract the ambient pressure. The amount of actual boost will depend on the size of the pulley, and losses due to belt slippage or leakage, environmental conditions, elevation, etc.
Actual boost= (Intake manifold pressure; absolute hPa) – (Ambient air pressure kPa x 10) x 0.014503774
*A stock car will see boost in the 10-11 PSI range, but it will bleed off at higher RPM’s.
*A stage 1 car will see boost in the 12 PSI range, but it should not bleed off at higher RPM’s
*Stage 2 cars can see as much as 16-17 PSI. I have seen a max of 15 PSI, but that is in really high DA’s and we’re at about 600 ft. above see level (hotter/less dense air will make slightly less boost).
Air mass (kg/h): This is the amount of air the car is taking in via the intake. The environmental conditions and type of intake you have will effect this value. Obviously, more air can equate to more power, so the higher the better.
*I have seen the stock intake have around 1100 kg/h maximum in my logging (70F, 50% humidity, 2000 DA). Aftermarket intakes that use the stock airbox are in the 1100-1200 kg/h range, and aftermarket open intakes like the Roc-Euro and CTS are in the 1300-1400 kg/h range.
Intake air temperature (degrees C): Another one that is pretty self explanatory; just note that it is in Celsius. IAT’s have a big impact on performance. Higher IAT’s mean less dense air, less timing, and the chance of more knock/timing being pulled and other bad things like misfires. The lower the IAT’s, the better.
*During my logging (see conditions above), I typically see a max of upper 60’s with the stock airbox. With the CTS intake (open filter with heat shield), I typically see in the upper 50’s.
Ignition angle; actual (degrees): This is the total actual timing.
*A tuned stage 2 car on 93 octane should typically sees total timing in the upper teens or low twenties at higher RPM/WOT. On race gas those numbers can be in the mid to upper 20’s in some cases.
ING_AD_KNK_x (degrees): This is the amount of timing being pulled from the given cylinder (x) due to knock detection. The amount will wholly depend on the gas you use, the condition of your car, and environmental conditions. It is very possible (and good) not to see any timing being pulled.
*Something in the -3 to -4 degree range is “normal” in hot temps or with lower quality gas. I have seen timing pull as high as -7 to -8 degrees on my car which will absolutely kill power. High IAT’s are usually the most likely cause. Once IAT’s get into the 60C range, you will typically see some timing pulled, and you’ll see those higher numbers when IAT’s reach into the 80C range; especially when mixed with lower quality gas or lower relative octanes.
RFP_AV (%): This is the bypass valve opening percentage.
*A stock car will see significant opening because the car will typically make more boost than requested at higher RPM’s, and the rest is bled off—this is why stock dynos die off after 5000 RPM.
*A properly tuned car should see nothing here; 0%. Anything else means the car is not making max boost/power. There are some instances where a tuned car may bleed off boost. I’ve seen this happen on my 1-2 shift when I get wheel spin, and others have reported it when IAT’s get extremely high as a protection mechanism (Revo tunes seem to prefer this method as opposed to retarding timing).