Why does my Dynamic Cylinder Air read lower when in Speed Density?

[Bill@HPTuners]

I've seen alot of people when they go to Speed Density mode from Maf mode see their Dynamic cylinder air reading in their histograms or graphs read 1/2 of what it reads in the table display.

This is caused by the maf reading still being in the table display and reading a steady number.

Since dynamic cylinder air can be calculated from maf as well as by other ways when you leave the maf sitting at a steady reading the program still tries to calculate dynamic cylinder air off of this faulty reading then averages it together with the other calculation finally giving you 1/2 of what the real reading should be.

The simple fix is to NOT log MAF(SAE) in your table display when your not using it

-Bill

[redhardsupra]

can we just have 2 separate dyncylair's, one for SD, one for MAF, so it eliminates confusion?

[Country Boy]

guilty.. lol

[Bill@HPTuners]

I know, thats why I made this a sticky

Hopefully this will ease confusion, ie in SD mode just delete the maf pid, when in maf mode keep the maf PID.

[redhardsupra]

what if you're trying to compare the airmass is between the two modes?

[Dirty Howie]

I don't seem to have this issue .........

I am logging MAF while doing my VE only cause i'm too lazy to remove the Maf PID.


DH

[Bill@HPTuners]

Many people remove the maf sensor all together or unplug it yet leave the PID in the table display...this is the most common reason they'll come across this.

[gbounds]

Bill, In studying my problem with a P0101 DTC. I highly believe my MAF is faulty although there is no spikes or dips. I believe the ref. table is the Calc air vs TPS vs RPM. In converting the MAF lbs/min to g/sec then comparing to this table my MAF the value is about 1/2 of the Calc air vs TPS vs RPM. Am I correct to think my MAF has this much error or am I referring to the wrong table.

[EC_Tune]

P0101 means that the difference between Dynamic Airflow (not g/cyl, just grams) and MAF airflow is too great and the PCM diagnoses it as a MAF problem. Sounds like your VE is significantly off.

[gbounds]

Thanks for the correction and I thought I was getting some small grasp with the tuning program. The P0101 started popping up around the time I installed a KandN cold air kit. Although KandN will argue for their kits. the problem was to coincidental. Anyway I've gone back with the stock tune and stock air box just to verify and address the VE. Still got the code.

I'll study and learn the relationship between Dynamic air and MAF.

[EC_Tune]

Hmmm. Might log some data. Could simply be a failing MAF. (MAF value goes to zero or max occasionally)

[gbounds]

Idle runs about 1 lb/min, 55mph is about 5 to 6 lbs/min and WOT pulls about 20lbs/min but no true dips or spikes of zero or max. I guess my next move is to make a scan from a proper working vechile to compare with.

[gbounds]

Did a scan on my 5.3l Tahoe and compared it against my silveradoss. MAF readings seem to be in the ballpark. Maybe my problem is intermittent and hav'nt ran accross a dip or spike yet.

[EC_Tune]

Very possible

[PurplePiss]

So this would affect VE tuning? Is this why the calc'd torque numbers are lower in olsd?

[EC_Tune]

No it won't affect VE Tuning as you have the MAF disabled.

[Alvin]

Bump, Since the latest beta I've been having a problem with this even though all the MAF related items are not in my PID list. Can something else be messing with it??

[Bill@HPTuners]

Alvin, please email support with a vcm suite infolog, your scanner config file you are using, your file named VCM Scanner.cfg, the scanner log you are seeing this issue on(just one is fine) along with a screenshot of exactly what YOU are seeing so we can try to recreate the error.

Thanks,
Bill