OK, I'm looking for some logs where people have the following logged:

1. load (2-byte preferably)
2. Airflow Hz (2-byte would be helpful, but not completely necessary)
3. Intake Air Temp
4. Baro (atmospheric pressure)
5. RPM (2-byte would help, but not necessary)

I just want to verify if what I thought all along is true...that load in our ECU is really a mass airflow per rev value, such as g/rev. Based on a few quick logs that I had lying around and one I found it seems to hold true, but I need a few to test this out and see if I can figure out a correct formula.

The reason I want to do this is because it will put real units on our load numbers, rather than the arbitrary numbers that we use now. Seeing mass airflow in logs would allow us to see how much mass airflow our turbos are flowing ,etc. For example, if we have the mass per rev, like g/rev, then we can easily calculate the lb/min of airflow, for example. This would tell us how close we are to maxing out a specific turbo's compressor, etc and be able to correlate our logs to compressor maps. People coming from DSMLink will like this since mass airflow is loggable.

I correlated the MAF Hz to mass airflows using the baro and intake temp and RPM in the MAF scaling thread and I have added that formula to my LogWorks, but I think the ECU is already doing it, with it's load variable. So, I want to verify if this is true or not.

Anyway, let me know if anyone has logs with these variables logged. On the couple of logs that I have looked at so far, it looks like we may be able to get g/rev by taking our load and dividing it by around 90. I need a few logs to come up with the exact number and to see if the correlation is there.


Thanks,
Eric

 

I will check back to this link tomorrow if no response I will do some logs for you tomorrow morning

 

I can do some logs this weekend, if that helps things any.

 

As requested. Here's one from tonight.

 

You should also be able to calculate proper psi if that stands true

 

Forgot to mention that 2-byte airflow and 2-byte RPM would help a bit (not completely necessary though). Edited first post.

Eric

 

I have logs from 6:15 this morning on my way to work. A long 4th gear pull to 110 with all of those variables logged. (Minus 2 Byte RPM)

I have a 2005 GSR with a 0011 ROM.

PM your e-mail if you want my logs. The one was done with super-duper-speed too.

 

OK, there is definitely some sort of relationship as you can see in my graph below. What I did was used my equations that I created way back in the MAF scaling work where I found a correlation with Maf Hz, intake temp, and baro to a mass airflow value. This calculation can be a little off since I did it quickly back then.

Anyway, what I did was take the data that PD1 attached and calculated the mass airflow from Hz, baro, and temp. Then, simple math converted that to mass per rev. Then, I graphed the mass/rev * (some constant) compared to his logged 2-byte load. This is because I'm thinking that load is really a mass airflow/rev value.

Here are the results so far:


The error fluctuates through the log, but I think most of this may be because of the stepping of the data, especially RPM, when going on full throttle. Also, I could only do this up to the 1600 Hz mark, as two-bytw airflow wasn't logged.

It does look like there is a strong correlation though. Maybe if the next few logs show the same relationship, we can get a rough formula for our mass airflow from load.


Eric

 

More results from tklemann's log:


I used a constant of *94 for this log and the data seems to be following pretty closely, within the errors of logging I would think. There is a slight break in the graph at the crossover of 1600Hz because the equation that I use to correlate Hz to mass airflow changes there, since 1600Hz is the last value in the Maf scaling table.

What do the disassemblers think? I know Bez has disassembled a ton of this code when he was writing his MAP/SD patch. Based on what I am looking at, it looks like the ECU load value that we log is a value that is already calculated by the ECU that includes MAF Hz, RPM, baro, and intake temp.

When disassembling the areas where the load variables are referenced, is there references to the baro, intake air temp, Maf Hz, and RPM?


Eric

 

OT, that was a quick run! These 9's are fast when done right, even though the gearing is slightly lower, that's logs about 0.1 -0.2 sec faster than mine at 28 psi - just a much greater volume of air/psi

To get it back on topic, just keep that in mind when comparing airflow logs to a 16GVIII

Also keep in mind any noticed inconsistencies in real ECU load and what you know is real can be fine tuned with the smoothing and scaling tables. I'm still fighting to understand their relationship to the baro and temp tables, this would help maintain more stable tune for slight changes in climate since the car was set with such a broad range conditions from the factory

 

Well, now I can't say whether the load value has baro and intake temp involved or not. If I compare the load value with just MAF Hz/RPM * some constant, I show the same relationship, even somwhat better, since I don't have to run the data through so many equations to convert to mass.



Since our baro and intake temps are only changing by a few percent at most, during a pull, I won't be able to tell if the load value has these incorporated or not simply from logged data.

So, I guess I will have to leave this up to the disassemblers to tell us for sure.

On a side note, for a rough approximation (seeing that load may or may not include the baro and temp data) to find your mass airflow (from the limited amount of data) you can do the following:

load/95=g/rev
g/rev*RPM/454 = lb/min or load*RPM/(454*95)

So, 300 load at 4000 RPM:
300/95=3.16 g/rev
3.16g/rev*4000/454=27.8 lb/min

270 load at 7500 RPM:
270/95=2.84 g/rev
2.84g/rev*7500/454=46.9 lb/min

This may be a very rough estimation, but it may be good enough to see how close you are to maxing your turbo, etc. For example, our turbo has a compressor wheel with a rating for about 44 lbs/min, so I wouldn't expect to see anyone with a lb/min airflow too much greater than that.


Eric

 

Eric I will post every log in a zip that I have that fills your criteria when I get home tonight (at work now).

I log:

Boost
2byte load
2 byte airflow
TPS
baro
intake temps
etc.

 

Actually, I think I am good for now. I don't think anymore data, at this point, will really answer my ultimate questions of whether the load variables is calculated with out without the baro and intake included. I PMd Bez on Aktive Matrix to see if he can add anything to this thread.


Eric

 

In LW with logged two 2b hz and 2bLoad channels in two different sessions, overlay some 2bHZ and load logs and you will notice whenever the two different Hz plots cross at the same point and the two different load plots cross at same point in time, there will always be corresponding RPM crossing at same time as well.

There will be some difference of scew resulting from lag we discussed earlier but this is minimal. Anyhow, this more or less confirms your theory above. I've always noticed a similar pattern between the two hz and load, just their rate or direction of change is RPM dependent.

As far as compressor efficiency with a turbo using your new reasonable value as load, would you think the AFR may make subtle changes to the efficiency?

 

Posting tons of disassembly probably not a good idea here - but I'll try to clear things how it works.

1. Recorded MAF pulses per RPM period value..
2.Some smoothings done.
4.SOme filtering done (the value and the previous value are compared -if the difference too high the newly recoreded value is discarded)
5. The maximum allowed mafperrpm(RPM) got from table and compared to value that got. Trimmed if bigger. The result called MAF_SOURCE_MAIN in my disasms...

6. The first load is got by multiplying MAF_SOURCE_MAIN by mafsize (mafsize is available in ecuflash definitions -its actually engine's size).

Then the all LOADS got ....First is ~MAFHZ/RPM*mafsize.
Second ~MAF/RPM*mafsize*BAROMETR
Final Load ~MAF/RPM*mafsize*BAROMETR *Air_temp_density
Airtemp_density got from table based on MAF air tempetature readings.

In routines that gets timing values from table or fuel the procedure GET_LOAD is used wich selects load according on the sensor's functionality- if all ok the third load is used ....If air temperature sensor is down than the second load is used...

To get MAF_HZ, MAF_SOURCE MAIN is then back multiplied by RPM ..
Then Maf_filtering table is used , them maf smoothing , than maf (scaled and smoothed) is barometr and airtemp compensated and a value Air Mass is got (trimmed available through MUT 28)...

So the outcome MAF HZ is close to Air mass but you need a barometr and airtemperature compensation to match...Either in load or in air mass....