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Russell @ BMS 09-11-2013 07:31 PM

Logging Parameters and their Meaning
7 Attachment(s)
Here is a quick reference to the JB4 N54 logging parameters and their general meaning as of ISO v31 firmware. Note that while many of these parameters are also present in other JB4 applications such as N20, N55, and S55 they may or may not retain the same meaning/use.

General things we look at when checking logs:

1) For absolute maps (all E series, F series maps > 2) is boost close to boost target. If no is PWM relatively high. If yes then that indicates a possible boost leak or wastegate issue. If no then it indicates FF adjustment might be required.

2) Is timing relatively stable and sloping up towards redline? Repetitive timing drops especially within the same gear while at wide open throttle this might indicate the boost target is set too high for the octane being used. Increase the octane by mixing in E85 or MMT based octane boosters, or revert to a lower boost map. If not equipped with a back end flash map consider adding in the free PUMP back end flash map.

3) Is high fuel pressure staying above 9? If no is low fuel pressure staying above 55psi? If yes then reduce the fuel demand by reducing the E85 mixture, reduce the boost target, or make the air/fuel ratio leaner via an E85 back end flash map. If no then add in a Fuel-IT stage1 pump upgrade or take one of the other steps above to reduce fuel demand. Adding in methanol, TBI injection, or full port injection, are all viable fueling upgrades if low pressure is OK but high pressure is not holding at higher power levels on E85 mixtures.

4) Are fuel trims sticking above 50? If open loop is less than 90 then raise it. If open loop is already at 90 or if you're getting 29F2 fuel pressure plausibility codes, then reduce fuel demand, or add in a free back end flash map.

5) Throttle. One of the most misunderstood aspects of evaluating logs is throttle movement. Note that throttle should not necessarily stick at 100% open at full throttle. It should be mostly fully open but closing proportional to boost exceeding boost target. Throttle is an active system used along with the boost control PID to regulate boost dynamically. Extended periods of throttle closure of 2 seconds or more and 40% or more closure normally indicates that boost control adjustment is needed. Short throttle movement of less than 30% and less than 1 second are expected and normal.

RPM: Engine speed
Boost: This is the pressure, in PSI, in the charge pipe just before the throttle valve. Under ideal conditions the boost value will within 1psi of the boost set point value (see Target). The factory N54/N55 TMAP sensor is able to read up to 20psi and for reading higher boost levels up to 36psi a 3.5bar TMAP sensor is required. The 3.5 bar TMAP sensor is standard on the N20, S55, and S63tu engines. Note this value does not necessarily represent the boost pressure in your intake manifold. If the throttle body closes more than around 70% it will progressively lower the boost pressure observed by the engine, but also progressively increase the boost pressure read by the TMAP sensor and JB4 logs.
Target: The JB4's target boost. The value is determined by the JB4s internal mapping and many other parameters including engine speed, pedal input, intake temperature, gear, and other internal logic. Typically boost should be close to target when the turbochargers are fully spooled up. Note some systems such as the EWG JB4 applications have additive target maps. With additive maps target represents the boost added to the factory boost target rather than the absolute boost target. If you see a log with a target of 6psi or less then its like an EWG model utilizing an additive map.

If boost is dramatically above or below target additional troubleshooting and setting changes are often required. Refer to PID tuning and duty bias notes: http://www.n54tech.com/forums/showthread.php?t=29893

In addition to the programmed maps there is a user definable map6 that lets you enter the specific boost targets by RPM, which the JB4 then uses along with its internal logic to construct a tuning map based around those boost targets.

ECU PSI: The ECU (Engine Control Unit) is just another name for the DME (Digital Motor Electronics) or engine computer. The ECU PSI is the DME observed boost which is being transmitted by the JB4. When boost is close to target then ECU PSI will be close to DME BT. The JB4 will alter this value above and below DME BT as needed to manipulate the throttle blade.
DME BT: The DME BT displays the current DME boost set point. This is determined by the DME and flash map and will vary from a peak of 10psi on the OEM flash map to as high as 20psi on back end flash maps. This value generally does not effect the JB4's boost target unless it drops suddenly to indicate either DTC intervention or a limp mode.

IAT: Intake Air Temperature is measured in the charge pipe just before the throttle valve and can be thought of as intake manifold temperature. It is measured by the TMAP sensor (Temperature Manifold Air Pressure) combination sensor…. Both boost and temperature in one physical sensor.
Typical values for a car with the stock FMIC (Front Mount Inter Cooler), not running in boost, is 20 degrees above ambient. With the onset of a boost condition, the temperature will rise quickly as boost rises and also with the length of time of the pull. Values quickly go from the normal 20 degree rise above ambient to perhaps a 70 to 90 degree rise.
The best upgraded FMIC will start out with only a 10 degree rise when not under boost and will limit the temperature rise to only about 25 degrees over a several gear pull. Also the lower the ambient temperature is the better the outlet temperatures will be.
Meth/water injection is almost always injected prior to (upstream) of the TMAP sensor location and therefore, results in this value dropping as injection commences. With the nozzle sizes used today (CM 10, 12, 14), a typical IAT reading will drop about 30 degrees from the IAT starting value just prior to going WOT (Wide Open Throttle). IAT below ambient temperature is typical using meth/water injection.

Reading is always displayed in Degrees F and is read from the left hand scale X 10.
Pedal: Gas pedal input. This is the position of the pedal under your right foot with a range of 0-100%. While using cruise control this value will always report zero.

Throttle: Throttle blade position (0-100%). The throttle trend displays the position of the throttle in percent. The DME takes the pedal position signal (or if higher, cruise speed demand) to generate an engine load demand signal. The load demand signal is then used to index most of the internal variables in the DME including the throttle position. N54 engines will normally have this value at 90-100% at full throttle when boost is on target, while with valvetronic engines which do not use a throttle body for load control (N55, S55) will generally reflect 60-90% at full throttle.

PWM: Stands for pulse width modulation but is also known as wastegate duty cycle. Represents the demand for the boost signal going to the vacuum control solenoid(s). The larger the signal the more vacuum is applied to the WG (Waste Gate…. exhaust gas bypass valve) control actuator and the harder the WG plug is forced onto the WG seat. The system is designed to "fail" in the WG open position so that the engine is not subjected to high boost conditions under a failure condition, such as a broken wire or faulty output.

PWM does not actually control the WG position.... but rather the pressure ratio across the exhaust gas power turbine. The WG position actuator has a very weak spring in it and yet controls a WG plug with a large pressure drop across it at high engine rpms and boost levels.
At low to moderate WG demand signals, the vacuum applied to the WG actuator will totally close the WG plug. As rpm and boost build, at some point, the pressure drop across the WG plug will overcome the supplied vacuum force of the actuator and the WG plug will reopen, maintaining the established exhaust gas pressure ratio.... and indirectly, also the boost pressure ratio, with no further action by the DME.
At high WG demand signal levels, the WG demand signal is great enough to maintain the WG plug on the WG seat, ensuring all gas flow passes though the power turbine.
During turbo spool up the JB4 will produce a high PWM to spool up the turbos and then as boost approaches target that value will drop to prevent boost from going over target. Once spooled the PID system takes over the PWM signal and adjusts it dynamically using the FF, RPM specific duty bias settings, and PID gain.
FF: Short for "feed forward" or the fixed component of the PID boost control system. This is the starting point for boost control and the PID will then adjust PWM above or below this value as needed for fine tuning. The user adjustment variable FF / wastegate adaptation value (0 -150) scales the FF value and will adjust itself over time as part of the normal JB4 learning routines. In addition this value can be user adjusted by RPM using the duty bias settings.

DutyC: Dutycycle. This field will vary based on the firmware version loaded and might represent the DME's projected duty cycle, which is not useful as the DME is not controlling boost in the first place, or in newer firmware versions has been changed to reflect calculated engine torque scaled from 0-7000rpm = 0-100lb/ft of torque. Note this is the torque value the DME thinks its producing and has little to do with how much torque you are actually producing.
Ign1: Ignition Advance is the number of crank degrees BTDC (Before Top Dead Center) when the spark is turned on to ignite the fuel/air mixture in the cylinder. Generally higher engine loads/boost levels require less advance because the burning process progresses faster (less time to complete) under higher cylinder pressures. Higher engine rpm generally requires more ignition advance because there is less time for the cylinder pressure to build up before the piston starts it’s downward stroke.
The displayed ignition advance value if for cylinder #1 but the DME can adjust timing on a cylinder by cylinder basis using an advanced knock sensor system with long term (octane detection) and short term (knock detection) trims analogous to a fuel trims. The displayed values can change a large amount under light to moderate loads….. more than 30 degrees on some engines. WOT (Wide Open Throttle) will result in a much narrower range of values….. usually dish shaped with values in the 10 to 13 degree range over the ends of the rpm band and a minimum valley value of about 6 - 8 degrees.

Of more importance is watching out for sharp drops of more than 3 degrees in the engine high torque/power band…. typically in the > 4500 rpm range. Sharp drops of 3 degrees from one scan to the next indicate potential knock activity and are a general indication that the boost curve may be set too high for the available octane. Drops randomly throughout runs especially on pump grade fuels are expected but repeated drops in the same gear indicate an overly aggressive tune.

Also note the DME will raise and lower advance as a function of normal mapping like during traction control events, gear changes, etc, and such drops are completely normal.
The JB4 uses this activity and the overall value of the ignition curve to calculate the Avg Ign (Average Ignition Retard) value. Newer JB4 firmware versions allow you to log timing from cylinders 2-6 in addition to cylinder 1 to provide a more comprehensive view of timing advance and knock. This must be enabled by entering the appropriate 6cyl timing value under the user adjustment page.
Avg Ign: Average Ignition Retard. Note this for E series and some F series models. The B48/B58, N63, S63TU, have boost bank2 shown under iavg instead of this calculation. A JB4 calculated value with a range of 0 - 6 that represents the average amount of timing below the maximum possible curve over a short term window. Lower values indicate a higher overall ignition advance while higher values indicate a lower overall ignition curve. This calculation is used by the JB4 for evaluating octane content by both map 5 (auto learning) and map 3 (methanol injection). Values below about 1.5 result in full Map 3 or Map 5 scheduled boost levels.
Values between about 1.5 and 6.0 result in lower and lower boost targets as an added safety feature for these two maps. As a general rule when using meth, race gas, or heavy E85 mixtures look for values below 2.0. When using pump gas expect values of 5 or higher.
FuelEn: This values changes based on the firmware and engine type. For v31 and newer N54 applications it's now used to represent the amount of fuel being added via the port injection system 0-100%. For most other applications this parameter is not used.

Trims: Fuel trims (0-50). The Trims display shows what the STFT (Short Term Fuel Trim) signal is doing. This value is displayed as 25 = 0% trims, 50 = +33% trims, and 0 = -33% trims.

This signal can be quite variable but as long as it does not spend too much time pegged at 50 (maximum value) then all is well. If pinned at 50 for long parts of a run typically AFR will behind to lean out and tuning adjustments must be made to get fuel trims back within range.
This signal is used to calculate an automatically tuned variable FOL (Fuel Open Loop) or just OL (Open Loop) variable. See OL discussed later.
Meth: Methanol flow (0-100%). The meth display shows a voltage conversion of the JB4 0-5v #15 input. Typically this input is connected to a BMS supplied FSB system which is used by the JB4 to control the methanol pump and measure pump pressure and flow. This signal can also be read from a stand alone 0-5V flow sensor such as the one provided by Aquamist.
When using map 3 the JB4 will transition between a low and a high boost map as a function of "meth" and "avg ign".
The user defined "Meth Flow Scaling" represents the minimum amount of flow to be considered "full flow". In the case of the FSB this value is 60. If methanol flow is half of the full flow value then the JB4 will target half way between its low and high map.
The field "Meth Boost Additive" determines how much boost the high map runs. With a maximum value of 75 representing approximately 20psi.

Typically for pump gas operation a value of 40 should be used here (approx 17psi) while for race gas and/or E85 mixtures values of 60-75 are more appropriate. It is unlikely factory turbos will be able to hit targets higher than 65 so those are generally used only for aftermarket turbos.

AFR: The AFR (Air Fuel Ratio in Lbs air/ Lbs gasoline fuel) trend displays for each bank under AFR1 for bank1 (1,2,3) and AFR2 for bank2 (4,5,6). Typical values are 15:1 at light engine loads decreasing to around 12.5:1 under heavy engine loads and high rpm.

Note: The N54 is a direct injection motor and as such will run much leaner air/fuel ratios than many who have worked with older platforms are used to seeing. It's common to target 14:1 at peak torque and 13:1 at peak HP for example. It is also normal to have the AFR display 20:1 when car is coasting in gear or under a misfiring condition where the DME will cut off fuel to the misfiring cylinder(s).  
FP L: Fuel pressure, low system. Pressure is read on the left hand scale X 10. Otherwise known as the in tank low pressure fuel pump. This value typically ranges from 55-70psi. If dropping below 50psi it indicates a problem with your low fuel pressure pump. Most often that problem is it needs to be augmented with an inline pump to keep up with the higher fuel demands required by ethanol usage.
FP H: Fuel pressure, high system. Otherwise known as the high pressure pump. Note all N54 include this and other platforms can only log this if also equipped with the flex fuel connector. This value represents the voltage of the high pressure 0-5V sensor, where a value of 20 is 5v. Each unit of measure is roughly equal to 150psi. Typical values at full throttle are 10-14, or 1500 to 2100psi. Values of less than 900psi as full throttle indicate a fuel delivery problem and the JB4 will failsafe at 700psi at full throttle. Note when not at full throttle a typical value is 5 or 750psi.
Map: The currently selected map. Refer to the JB4 map guide for additional details. You can use the drop down menu to change maps here.
Gear: Currently selected gear. For manuals 0 means the car is out of gear or the clutch is depressed.
LOAD: Represents the DME's load index and is very useful when working on back end flash mapping to identify where within a flash map table a tuning change is being made.
Clock: An internal JB4 variable used to keep track of various internal loops such as PID evaluations or ADC conversions. The value has no meaning to anyone other than BMS.

FOL: FOL is a bias applied to the HPFP pressure signal that the DME reads to affect the actual HPFP pressure. Higher values of this variable makes the DME see a lower HPFP reading and thus the DME actually raises the true HPFP pressure. If the HPFP or LPFP is weak or the E85 mixture is too high and the FOL value is also high….. typically above 85……. the DME could see a low HPFP pressure and generate a code.

FOL is an autotuning variable based on the TRIMS signal. The FOL value will trend up if during pulls the TRIMS signal is at maximum. Conversely, if the TRIMS signal is staying at zero, the FOL value will trend down.

The autotuning range of the FOL signal is 40 to 90. The maximum range is 0 to 100.

Also read/copy this for information on FU(x) functions and remember to get the latest version (For the software you are actually running) as these functions can change as time goes on. These Notes are specific to each software version so remember to get a copy when you update your specific firmware. The following reference if for the N54 ISO software version 27.8.


Below you will find a series of JPG Logs describing what is normal/typical for various displayed variables. Later I hope to add some of the “typical” abnormal ones also. Note these were made awhile ago so may or may not be relevant to current firmware and settings.

You will note that I also like to view the logs with a 30 unit range on the left vertical axis. The vertical axis range can be modified under the “Settings” Tab “X” Scale 0 - 100.

The latest JB4 N54 information and notes are posted here. Values such as FutureUseD diagnostics change by firmware version so download the firmware notes for addl reference.


Below you will find a series of JPG Logs describing what is normal/typical for various displayed variables. Later I hope to add some of the “typical” abnormal ones also.

You will note that I like to view the logs with a 30 unit range on the left vertical axis.
This scale range fits very well with all variables except the TRIMS value which needs to be view on a 0 - 50 range scale.
The vertical axis range can be modified under the “Settings” Tab “X” Scale 0 - 100.

Steve @ BMS/Fuel-It! 09-11-2013 07:51 PM


Nice job!

Files sent for review and approval;)

iuhutch 09-11-2013 07:54 PM

SICK - thank you AZ (and Boosted for requesting!)!

Can we add this to either thread and make it sticky?

Russell @ BMS 09-11-2013 07:55 PM


Originally Posted by SteveAZ (Post )

Nice job!

If you'd like, we can put in my charts with examples I did in an earlier post. Your call....

Sonds like a winner. Have to learn how to do that....however.:clap:

iuhutch 09-11-2013 07:58 PM

1 Attachment(s)

Originally Posted by SteveAZ (Post )

Nice job!

If you'd like, we can put in my charts with examples I did in an earlier post. Your call....

Yes, please do. Also thought SRanch's log from Terry's recent tune would show good values? Although this car is built to the tilt! :burnrubber:

Russell @ BMS 09-11-2013 08:09 PM


Originally Posted by iuhutch (Post )
Yes, please do. Also thought SRanch's log from Terry's recent tune would show good values? Although this car is built to the tilt! :burnrubber:

Yes LOL...... and, unfortunately for most of us, unattainable values at the current time. :(

bmsportzn135i 09-12-2013 02:58 AM

Thank you.
And its awesome, its a sticky.

nguyenvn 09-12-2013 03:16 AM

Thanks AZ! This was long overdue!

GetSomeE92 09-12-2013 08:09 AM

Many thanks, az335iat. I know that must have taken some time and I know I really appreciate it.

boostedMPLS 09-12-2013 08:16 AM


Originally Posted by az335iat (Post )
Her is the first installment on the parameters and functions included in the JB4 G5 boards and tuning logs.

I hope this helps.

Nicely done AZ and cannot thank you enough! Really nice to see this become a sticky that will provided valuable insight for those looking to further understand the parameters their car is reading.


knissel 09-12-2013 11:57 AM

Awesome thead, I have been waiting for something like this for a long time. I can't seem to find the FP L and FPH in the csv. I can locate it in the JB4 program on the graph but I can't in the csv.

Russell @ BMS 09-12-2013 12:49 PM


Originally Posted by knissel (Post )
Awesome thead, I have been waiting for something like this for a long time. I can't seem to find the FP L and FPH in the csv. I can locate it in the JB4 program on the graph but I can't in the csv.

FP H is "FuelP" in the Excel file.
FP L is "oiltemp" in the Excel file.

Terry is going to update the column header info to match the current log descriptions in the near future. ;)

Terry @ BMS 09-12-2013 01:38 PM

Yes I'll be adjusting the interface shortly so the column names match up. :)

Nugs 09-12-2013 06:20 PM


Originally Posted by az335iat (Post )
FP H is "FuelP" in the Excel file.
FP L is "oiltemp" in the Excel file.

Terry is going to update the column header info to match the current log descriptions in the near future. ;)

I think this is different with the N55 and oil temp is actually the oil temp.

FL335 09-12-2013 07:21 PM

Much appreciated. I am now on the path to enlightenment.

Russell @ BMS 09-12-2013 07:32 PM


Originally Posted by Nugs (Post )
I think this is different with the N55 and oil temp is actually the oil temp.

I do not have much experience on the N55.
If the Excel "oil temp" values go much over 100 then oil temp is actually oil temp for the N55.

Russell @ BMS 09-12-2013 07:37 PM

Glad everyone.....well most anyway..... are on the correct path.:lol

Now all everyone has to do is keep it on the highway. ;)

I also hope to be posting some example trends up in the near future....
with the help of SteveAZ.

Peter @ Pure 09-13-2013 12:30 AM

Tnx alot man!

Tmos 09-13-2013 03:09 AM

Thanks az, very informative and useful post! :)

justnnavy 09-14-2013 04:11 AM

Love the scenario and map combo setup. easy to understand... more examples such as common issues w/ pre and post graphs would be DAS BOMB haha =) EDIT: reread and saw you already plan to cover this...nice

GetSomeE92 09-16-2013 08:01 PM

This thread is a huge help. Thanks again, man. The addition of the sample log graphs with accompanying explanation is a great touch.

Russell @ BMS 09-17-2013 09:03 AM

Thanks..... I hope this helps.

Element 09-18-2013 04:57 AM

Such a great thread. Certainly filled in some gaps in my knowledge bank as far as certain parameters are concerned.

BimmerNFS 09-18-2013 11:36 AM

This is EPIC!

iuhutch 09-18-2013 07:07 PM

1 Attachment(s)
My newest datalog after AA FMIC install. Thought maybe it was worthy of an example post?...esp to reflect the IAT.... :rolleyes2

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