Simple MAF/DYNAIR pid question.

[acomp917]

Hello All,

I have been graphing SAE.MAF to GM.DYNAIR in an effort to see if the VE air flow/mass matches the MAF. I'm noticing that during tipin the VE shows reduced flow(in comparison) and the opposite during tipout. This indicates that the slope of the VE table needs increased(with respect to vac).

Question:
Is it reasonable to assume that if I calc.pid MAF/DYNAIR and apply the resultant factor to the VE table, that would create matching and working air mass calculations?

I assume that ALL modifiers(IE temp) are consistent to both the MAF and DYNAIR pids at any given moment.

Starting simply,
S

[joecar]

Also compare with GM.MAF.

[WeathermanShawn]

Question:
Is it reasonable to assume that if I calc.pid MAF/DYNAIR and apply the resultant factor to the VE table, that would create matching and working air mass calculations?

I assume that ALL modifiers(IE temp) are consistent to both the MAF and DYNAIR pids at any given moment.

S

Its that second assumption that is not necessarily correct. The DYNCYLAIR (SD) does not take into account all the temperature modifiers.

Don't know if that is what you are asking, but I ran into that reality lately. Are we talking about the same PID(S)?

[acomp917]

Thanks Shawn,

I know the platform is not open, but could you tell me how you determined that the density modifiers are not used on SD. That is a basic prerequisite of SD.

S

[WeathermanShawn]

I will do my best. I want to first make sure we are describing the same PID(s).

1. GM.CYLAIR.DMA Air Flow Grams/Cyl ..MAF Airflow
2. GM.DYNAIR.DMA Air Flow Grams/Cyl..Speed Density

If those are the same PID(S), I have logged each but I have not found that the GM.DYNAIR.DMA reflects the Airflow after all of the charge temperature calculations, modifiers etc., have been calculated.

It appears to be the dynamic airflow prior to the modifications. As always, Joecar can explain a lot better than me. But, I can certainly provide numerous logs that show the same dynamic airflow..regardless of charge temperature, filters, etc.

Again, I want to make sure we are talking about the same thing. But I recently ran into a huge roadblock trying to figure out the same thing.

[acomp917]

Shawn,

Not cylair or variant. just gm.dynair vs. sae/gm.maf. Those are measured in gm/sec. They are calculated from VE table and measured from MAF. I have some difference(see Post#1) btwn the two and would like to simply factor the difference into the VE in order to make both the same.

In my short sight, I trust the MAF cal. I will use it to create VE table. I will adjust IFR in an effort to set AFR with consideration to new timing map. This is a stock system. It seems to be a simple method of balancing the tune. It has already responded favorably to my harsh adjustments.

S

[WeathermanShawn]

Sometimes these PID(S) are simply reflecting a Table look-up (user-input).

I have just learned to distinguish between what is being calculated, and what is just simply a Table Look-up.

We are probably talking about two different things.

Hopefully you got it straight.

[redhardsupra]

Shawn,

In my short sight, I trust the MAF cal. I will use it to create VE table. I will adjust IFR in an effort to set AFR with consideration to new timing map. This is a stock system. It seems to be a simple method of balancing the tune. It has already responded favorably to my harsh adjustments.

S

you mean IFR hacking because you changed spark? How does spark affect IFR or any of it's components?

[acomp917]

RHS,

I'm using SSpdDmon's method of leaving the MAF cal stock. The only method that I know to change the LTFT's in a MAF system is using IFR. There was a considerable change (10%) from factory IFR as an initial hack. With original trim(6%) and timing changes(another 2%), plus 2% to put the trims in the ~-2% range. I have only done preliminary changes, now the real tuning can take place.

I have the first impression that this is a simple and good way to proceed. I also think the VE cal factor can be created by a simple MAF/DYNAIR calc.pid.

To be honest with you, this PCM is very easy to tune. The EFIL system is very good and the forums are full of helpful info. I first thought I'd hate not being able to "real-time" tune. I'm thinking that this method is better, maybe more scientific.

S

[ScarabEpic22]

...
To be honest with you, this PCM is very easy to tune. The EFIL system is very good and the forums are full of helpful info. I first thought I'd hate not being able to "real-time" tune. I'm thinking that this method is better, maybe more scientific.

S

If you want to tune in Real Time, buy a RoadRunner PCM from Moates. Can update everything on-the-fly.