Mass Airflow for DCX

dcweber56 · Post by **dcweber56** » Mon Dec 07, 2009 10:33 am

Boosted 09 Challenger- Just trying to find a PID that has comparable numbers to the throttle body flow tables so I can make sure I'm in the ball park.
PID "Mass Airflow"
When I go WOT it reads 16,xxx g/s for a split second and then drops to ~2,500 g/s for the rest of the pull. Whats the deal?

jimb · Post by **jimb** » Mon Dec 07, 2009 4:15 pm

I assume your referiing to DataViewer? Can you post a log?

dcweber56 · Post by **dcweber56** » Mon Dec 07, 2009 4:31 pm

here you go....

jimb · Post by **jimb** » Mon Dec 07, 2009 6:37 pm

Forums upload is still broken!
Can you please email it to: [email protected]

duster360 · Post by **duster360** » Mon Dec 07, 2009 11:17 pm

Log actually downloaded fine for me,,go figure.

The goofy Mass Airflow spike looks to be just a log anomaly. Other important PIDs(Pratio, IPW,) do not spike along with Mass Airflow, so that tells me the PCM didn't really think there was spike in Mass Airflow.

duster360 · Post by **duster360** » Mon Dec 07, 2009 11:26 pm

Never mind,,,After looking at the rest of the Log, the Mass Airflow PID's values at part throttle just don't make any sense at all.

jimb · Post by **jimb** » Tue Dec 08, 2009 11:03 am

We looked at it and the value doesn't look right. Will need to investigate.

dcweber56 · Post by **dcweber56** » Wed Dec 16, 2009 1:21 pm

So I gave up on the "Mass Airflow" PID and I've been trying to use the "Total port mass flow scaled" and it gets pegged at 512g/s at anything north of 5k RPMs (p-ratio> 1.5). But! I've seen logs of other DCX cars that won't read that high even at higher boost levels... what's the deal?

dcweber56 · Post by **dcweber56** » Thu Dec 31, 2009 10:16 am

jimb · Post by **jimb** » Mon Jan 04, 2010 10:59 am

I looked at this early last week. The range of "raw" values in the log don't look correct and does not appear to be a DV math overflow. I'm still investigating.

jimb · Post by **jimb** » Mon Jan 04, 2010 3:47 pm

UPDATE: I don't have access to an 09 Challenger and unable to find any issue using an 07 DCX ECU on the bench using u7135-9r21. According to DCX info; The range should be 0 to 1638.375 g/s. Can you collect a log of just MAF with key on/engine off? This would provide a baseline of raw ECU MAF values. Also may wish to update to 9r21 as your currently on u7135-9r18.

Mike_Levy · Post by **Mike_Levy** » Sat Apr 17, 2010 3:15 am

Why is there a MAF reading at all? We don't have a MAF sensor, so where does it come from?

duster360 · Post by **duster360** » Mon Apr 19, 2010 4:34 pm

Mike_Levy wrote:Why is there a MAF reading at all? We don't have a MAF sensor, so where does it come from?

The PCM is model based. That means it uses a set of equations that 'model' ei: estimate the mass air flow entering each cylinder(mg/cylinder/cycle).

Once the PCM has a good idea what the mass flow rate is, its relatively simple for it to inject the apropriate amount of fuel.

So the PCM absolutley needs to know the MAF even though it doesn't use an actual(expensive) MAF sensor to directly measure it.

Mass Airflow for DCX

Mass Airflow for DCX

RE: Mass Airflow for DCX