Data Logging/OBD II

[Cortes2141]

I recently bought a a nice OBDII bluetooth dongle and I am trying to start data logging on my z4mr, however, there are some vehicle specific values I don't know. For example, what is the idle MAF rate, throttle position, and timing advance for our cars? I also installed the base Evolve tune (no headers/mods) which I'm guessing changed the factory timing advance. Any data loggers or pro mechanics out there that can help point me in the right direction? Also would be interested to hear Sal's point of view... Thanks!

[Cortes2141]

Oh, a couple things I forgot to mention. My car, prior to the Evolve tune, had been randomly bogging down and occasionally stalling out at stop lights. I researched it and it seems numerous people have had the issue. It also seems like my gas mileage has significantly decreased from roughly 27mpg to about 15, but my LTFT seem to be fairly normal (around +4%). I have been doing a lot more city driving but not sure that would acount for 12mpg loss?

[Small Yellow]

Correct me if im wrong guys.

MAF = Mass airflow sensor

Throttle position sensor = how much opened are the throttle bodies/butterfly

[Cortes2141]

Originally Posted by Small Yellow

Correct me if im wrong guys.

MAF = Mass airflow sensor

Throttle position sensor = how much opened are the throttle bodies/butterfly

That's correct...I am wanting to know the values those sensors read..for example at 1000rpm I'm currently sucking in about 27cfm with the intake temp at 91F and my throttle position is 7.45%.... However, with out having the baselines I don't if I have reduced airflow or better than normal.

[StickMon]

My throttle position at idle is 6-7%. You'll find out that at anything up to about 6k rpm it maxes out at 75%
I'll check MAF and advance on the way home tonight.

[StickMon]

At 870-880 rpm, MAF = 0.4 lb/min, timing = +12

[Cortes2141]

Originally Posted by StickMon

At 870-880 rpm, MAF = 0.4 lb/min, timing = +12

Wow then if my calculations are correct I am sucking about twice the air you are (not factoring in exact air temps and humidity). My timing is also +12 and my throttle position does hold around 7% as well. I also noticed it caps out at about 75% and thought it was rather odd.... Thanks for the response!

[exdos]

I've just looked through some of my datalogs for you.

In OEM guise, at idle of around 870rpm airflow is 0.41lbs/min and Absolute Throttle Position is 7.1% that's with an intake air temperature of 80 degs F.

In 3rd gear at full throttle, the Absolute Throttle Position reads 76.1% and the maximum airflow is 30.77lbs/min.

If you can record your OBD monitoring and save the files in .csv format, I'd be happy to compare them to my own records for you. I find that recording Engine RPM, Airflow through the MAF, IAT and vehicle speed, simultaneously, to be the best general parameters to record unless you are wishing to look at anything specifically.

[Cortes2141]

Awesome, thanks for the values. I'm using Torque which only measures MAF in CFM or gramme/sec..How are you guys getting Lbs/m? Also out of curiosity what kind of MPG are ya'll getting with heavy city driving? ...I am surprised more people aren't responding to this thread. Not many people out there datalogging?

[exdos]

Originally Posted by Cortes2141

Awesome, thanks for the values. I'm using Torque which only measures MAF in CFM or gramme/sec..How are you guys getting Lbs/m? Also out of curiosity what kind of MPG are ya'll getting with heavy city driving? ...I am surprised more people aren't responding to this thread. Not many people out there datalogging?

I've been using Auterra's DashDyno for over 7 years now and you can set it to record in either Imperial or Metric. I find the files most useful if they're saved in .csv format so that they can be imported into Excel where I can make formulas and graphs from the raw data. From the 4 parameters that I gave in my last posting, I can use the data to calculate Volumetric Efficiency which is very useful to see what improvements, if any can be obtained from modifying the air intake and exhaust systems.

It also surprises me that more people don't seem to be into datalogging, especially with the hardware and software that works with phones and tablets being so cheap now.

I don't do any city driving so I'm afraid I can't help you with MPG figures.

[Cortes2141]

Originally Posted by exdos

I've been using Auterra's DashDyno for over 7 years now and you can set it to record in either Imperial or Metric. I find the files most useful if they're saved in .csv format so that they can be imported into Excel where I can make formulas and graphs from the raw data. From the 4 parameters that I gave in my last posting, I can use the data to calculate Volumetric Efficiency which is very useful to see what improvements, if any can be obtained from modifying the air intake and exhaust systems.

It also surprises me that more people don't seem to be into datalogging, especially with the hardware and software that works with phones and tablets being so cheap now.

I don't do any city driving so I'm afraid I can't help you with MPG figures.

Interesting, I'll see if there is any other way to convert to lbs..I would think cubic feet/min would be considered the US/Imperial. I'm not even sure of the exact conversion to lbs/min. As far as the VE goes I believe Torque will actually just monitor that as is, I will have to turn it on and try it out. What are you able to gain/tweak from that knowledge?

[angelr]

I'll be logging mine soon to hopefully determine why it's going flat at around 6k with the ess tune. Very consistent and feels like it's down about 25-30 hp at the point before it picks back up again towards the rev limiter at 8.2k. Not sure if it's timing, fuel , egt or vanos related but it's noticeable from the passenger seat if you have a calibrated arse. Feels great everywhere else and I'd like to pinpoint it before I do a retune.

[exdos]

Originally Posted by Cortes2141

Interesting, I'll see if there is any other way to convert to lbs..I would think cubic feet/min would be considered the US/Imperial. I'm not even sure of the exact conversion to lbs/min. As far as the VE goes I believe Torque will actually just monitor that as is, I will have to turn it on and try it out. What are you able to gain/tweak from that knowledge?

You can use something like the calculator found here: http://www.denysschen.com/catalogue/density.aspx
using the figures from a local weather station on the internet. From that you should be able to get the correct air density conversion to change cubic feet/min into Lbs/min or gms/sec.

The Z4MC's VE is around 106% but it can be increased with modification to the air intake and exhaust systems. A plot of VE virtually mirrors the Torque curve therefore anything that might increase VE will increase Torque and HP.

[Cortes2141]

Originally Posted by exdos

You can use something like the calculator found here: http://www.denysschen.com/catalogue/density.aspx
using the figures from a local weather station on the internet. From that you should be able to get the correct air density conversion to change cubic feet/min into Lbs/min or gms/sec.

The Z4MC's VE is around 106% but it can be increased with modification to the air intake and exhaust systems. A plot of VE virtually mirrors the Torque curve therefore anything that might increase VE will increase Torque and HP.

Ok so unless I'm just crazy, I am still calculating my air intake to be like 1.2lbs/min at 90F and 40MSL...which seems insane when most of you seem to be pulling .4lb..something has to be off.

I know a dirty MAF can cause erroneous numbers but that typically errors on the side of reading less air than is actually going through. Any thoughts?

[exdos]

Originally Posted by Cortes2141

Ok so unless I'm just crazy, I am still calculating my air intake to be like 1.2lbs/min at 90F and 40MSL...which seems insane when most of you seem to be pulling .4lb..something has to be off.

I know a dirty MAF can cause erroneous numbers but that typically errors on the side of reading less air than is actually going through. Any thoughts?

I'm not very familiar with Torque but I've had a look at it and had a little play. If you look in the "Vehicle Profile" what have you got the Volumetric Efficiency set at?

Have you tried connecting the application to a different car and checking the results for comparison. Can you send me a recording of the following 4 PIDS recorded simultaneously:
1. Airflow through MAF
2.. Engine RPM,
3. Intake Air Temperature
4. Vehicle Speed from ECU

and then I'll compare your results to my own data.

When you say your gas mileage has gone down, is this what you notice when you're buying fuel at the pump or is this coming from Torque?

[Cortes2141]

Originally Posted by exdos

I'm not very familiar with Torque but I've had a look at it and had a little play. If you look in the "Vehicle Profile" what have you got the Volumetric Efficiency set at?

Have you tried connecting the application to a different car and checking the results for comparison. Can you send me a recording of the following 4 PIDS recorded simultaneously:
1. Airflow through MAF
2.. Engine RPM,
3. Intake Air Temperature
4. Vehicle Speed from ECU

and then I'll compare your results to my own data.

When you say your gas mileage has gone down, is this what you notice when you're buying fuel at the pump or is this coming from Torque?

I can't seem to attach a CSV file, it says invalid file type. My VE is set to 85% in the profile section, but what does that mean exactly vs. the actual VE reading from the ECU? Also I have not tried attaching to another car to check. Honestly I wouldn't know what would be considered normal on any other vehicle either.

As for the gas mileage I am using the actual car itself, switching through the computer with the blinker knob then holding it down to reset it after each fill up. It estimates around 17mpg right now. But, to be fair I am comparing it to what I was calculating based off resetting "trip" at each fill up. I do know that I do a bit more city driving now though.

[exdos]

Below is some data from my Z4MC in OEM state. The VE has been calculated in Excel from the published formula but the parameters of: Engine RPM, Airflow rate through the MAF, Intake Air Temperature and Vehicle Speed have all been recorded from the ECU. As you can see the VE is in the order of 100% and the published figure for the S54 engine is 106%.

Because the OEM air-intake system is sealed, the intake benefits from the "ram effect", so at higher speeds in higher gears (with lower rpm), the air pressure gets above ambient pressure and consequently the cylinders fill with air at a pressure above ambient, and that is the reason why it can produce a VE of above 100% as a NA engine.

Other vehicles that I've datalogged normally produce VEs of around 85% though.

The data




The same data as a graph

[Cortes2141]

Ok, so since we can get up to %106 VE should I change the profile settings in Torque to 106 rather than 85? And if so what exactly is it changing? I would guess it changes the equation slightly that the app uses to calculate my VE from the ECU, but I don't know. Since for some odd reason Torque doesn't display in lbs/min the formula you use wouldn't work for me to cross check. I will do 2 more runs displaying VE in the data log, one at 85% setting and then another at 106% to compare, then take a screen shot and post it.

[exdos]

lYou can set up Torque to record airflow in gm/secs, which easily converts to lbs/min.

[Cortes2141]

Ok, so I did a leisurely run with my profile set at 85 VE and then at 106 VE, also I changed it to g/sec. Hopefully these screen shots are view-able.

[exdos]

Looking at your second spreadsheet and using Row 11, where the Engine RPM is 7380 revs and the MAF rate is 213.37gm/sec: this converts to ( [213.37 x 0.002204622622] x 60 = ) 28.22lbs/min which is about right.

The sampling rate from a Z4MC with an OBDII data logger is just over 6 PIDs per second, and the data logger rotates through the samples as it logs them, so there is a slight interval between all samples logged. This means that when the MAF rate is logged, it is not at the exact moment when the RPM was logged, so there is always a bit of laxity between the figures appearing on any specific row in the spreadsheet, especially during acceleration. During steady state, the variations tend to be less, so if we look at, say Row 45, where the Speed and RPM are fairly stable, the MAF rate is 24.57gms/sec, which converts to ( [24.57 x 0.002204622622] x 60 = ) 3.25lbs/min which is normal and not excessive.

[Cortes2141]

Originally Posted by exdos

Looking at your second spreadsheet and using Row 11, where the Engine RPM is 7380 revs and the MAF rate is 213.37gm/sec: this converts to ( [213.37 x 0.002204622622] x 60 = ) 28.22lbs/min which is about right.

The sampling rate from a Z4MC with an OBDII data logger is just over 6 PIDs per second, and the data logger rotates through the samples as it logs them, so there is a slight interval between all samples logged. This means that when the MAF rate is logged, it is not at the exact moment when the RPM was logged, so there is always a bit of laxity between the figures appearing on any specific row in the spreadsheet, especially during acceleration. During steady state, the variations tend to be less, so if we look at, say Row 45, where the Speed and RPM are fairly stable, the MAF rate is 24.57gms/sec, which converts to ( [24.57 x 0.002204622622] x 60 = ) 3.25lbs/min which is normal and not excessive.

Awesome, well glad to know everything is in the normal range. Thank you so much for helping me out with all of this!