Question about VE air, MAF air, and Dynamic air

[cc-rider]

I'm logging VE air, MAF air, and Dynamic air (all in lb/hr). I've got a question about these...

Funadmentally speaking, if you've got your VE table dialed in perfectly, and your MAF dialed in perfectly....should all 3 of these be reading exactly the same?

[schpenxel]

During steady state, yes. During quick changes, no. MAF doesn't react instantly so it can be "behind" during quick changes, in theory anyways.

[cc-rider]

So its funny you say that. I've been fighting knock when shifting hard. Tried to get burst knock working. Then GHuggins hooked me up with some injection timing changes to try and help with it. Took it out for a run with my SD tune. Still got some big KR during hard shifts. Finally decided to tune in my MAF. Whamo....no KR on hard shift when running MAF only.

Which made me take a look at my logs of VE and MAF air. What I found is that my VE air lagged behind my MAF air. Seems the MAF was increasing quicker on boost transitions. So I may have my VE table a bit low in the transition region.

[schpenxel]

Yeah, VE might be off somewhere in between, would be my guess.. MAF's are a lot faster than they used to be though too

[mowton]

For dialing in the MAF you need to use the MAF data as it represents the transform from air to Hz that the PCM needs to know. For VE, I delete the MAF entirely from my channels and just use Dynamic Airflow to set the VE. As Dynamic Airflow is the "final answer" from the PCM as far as the Airflow model, I log it all the time as well as develop a cylinder airmass derived from it, not the MAF for all the reasons you guys touched on above. This then shows a more accurate spark table axis to better represent the timing during the transient periods when the MAF/Dynamic are diverging. You will be surprised where in the spark table you really are :-)

Ed M

[cc-rider]

So you are using dynamic airflow, MAP, & RPM to build a VE table for you? Interesting idea...I never thought of that. I have been using AFR error to build it in. But I have not been removing the MAF signal from my PID's. I've been failing the MAF...but not removing it from the table.

[GHuggins]

So its funny you say that. I've been fighting knock when shifting hard. Tried to get burst knock working. Then GHuggins hooked me up with some injection timing changes to try and help with it. Took it out for a run with my SD tune. Still got some big KR during hard shifts. Finally decided to tune in my MAF. Whamo....no KR on hard shift when running MAF only.

Which made me take a look at my logs of VE and MAF air. What I found is that my VE air lagged behind my MAF air. Seems the MAF was increasing quicker on boost transitions. So I may have my VE table a bit low in the transition region.

From my experience, especially with boosted motors, the MAF will read quicker and more accurate in the higher rpms. In other words it sees and can translate the increase in air flow quicker than the map sensor can. Because of this, even with the VE dialed in, on blower applications and especially where its been turned up speed wise, I lower the dynamic settings down in the teens to even as close as a thousand rpm's.

On a side note - injection tables working good for you?

[GHuggins]

So you are using dynamic airflow, MAP, & RPM to build a VE table for you? Interesting idea...I never thought of that. I have been using AFR error to build it in. But I have not been removing the MAF signal from my PID's. I've been failing the MAF...but not removing it from the table.

It has to be gone for accurate logging when SD tuning.

[cc-rider]

The injection tables did indeed seem to work great for me. Thanks for your help there. Just yesterday I finally got out and turned my MAF back on and tuned it in. Still a bit to go. But I now can pound gears pretty hard without any KR. May even start to add a degree or two back in to see what happens. I'm running about 12 degrees right now (@ 9 psi).

[mowton]

So you are using dynamic airflow, MAP, & RPM to build a VE table for you? Interesting idea...I never thought of that. I have been using AFR error to build it in. But I have not been removing the MAF signal from my PID's. I've been failing the MAF...but not removing it from the table.

I still use the WB error vs MAP/RPM. The Dynamic air is used to know exactly what airflow the PCM is using and to support the Dynamic Cylinder Airmass parameter en lieu of the MAF based cylinder airmass.

And I agree about moving the High RPM Disable lower....

Ed M

[JBZ]

It has to be gone for accurate logging when SD tuning.

I didn't know that. good info.

actually this is all good info in this post. I found an old thread about back calculating cyl airmass in both VE and MAF and using that to help dial in both of them at the same time. although I was able to make the PID that redhardsupra work I noticed that it got some pretty funky numbers and if I would paste it into my VVE table it would kind of go crazy. of course I stuck with just using my AFR error.

[Michael_D]

I still use the WB error vs MAP/RPM. The Dynamic air is used to know exactly what airflow the PCM is using and to support the Dynamic Cylinder Airmass parameter en lieu of the MAF based cylinder airmass.

And I agree about moving the High RPM Disable lower....

Ed M

First I heard about all this.... Sonofabitch. Guess it's back to VE cal. And just when I thought I was done. huramp!

So how far do you lower Dynamic Disable? I'm thinking there's gotta be a better way to determine what to lower it to than guessing. N/A application with a rowdy camshaft for example?

[redhardsupra]

I have beaten it to death 8 yrs ago. What do you need to know?

[mowton]

I have beaten it to death 8 yrs ago. What do you need to know?

Yes and some of us listened :-)

Thank you Marcin for all your great insight and knowledge.

Ed M

[Michael_D]

I have beaten it to death 8 yrs ago. What do you need to know?

Just a logical method to determine what rpm dynamic air flow will respond quicker than MAF. That's why there is a hybrid MAF/VE system, isn't it?

[redhardsupra]

you mean this: https://redhardsupra.blogspot.com/2010/02 ?

[Michael_D]

Holy shit..... I have a ton of reading to do. I guess I live under a rock, because I was not aware of your blog. It should be mandatory homework for any aspiring wannabe tuner.

[mowton]

Holy shit..... I have a ton of reading to do. I guess I live under a rock, because I was not aware of your blog. It should be mandatory homework for any aspiring wannabe tuner.

Dude, Marcin has been teaching us the details of this tuning shit for years.....he along with others like Banish, Ross/Simon/Joel from EFI Live, Doug (EC_Tune), Russ Kemp (RussK) and more recently Dave Steck (DSteck) to mention a few have provided much of the missing detail (and math) which has allowed, at least as far as I, to proceed to the level I am at.....and that isn't very far up the knowledge pole for sure. I have computers filled with theirs and other excel, word etc files providing all the tools I use (and use to teach) today.

Ed M

[JBZ]

you mean this: https://redhardsupra.blogspot.com/2010/02 ?

that's good stuff, ive also read another few of your blogs. smart man...and thanks for putting that stuff up. although im more or less a noob around here I have studied a lot of this stuff...for me this thread and blog in-particular http://www.hptuners.com/forum/showth...2-Help-With-VE
and this http://redhardsupra.blogspot.com/200...odels.html?m=1

I used what you posted here to back calculate the GMVE table but of course as you have said in the blog that pertains to the same equations it kind of goes bonkers in some areas. and I assume that's because with the map/RPM range being to broad it cannot pinpoint a MAF vs RPM that is relative enough due to the loss of not only whole numbers but decimal points? and also using mean values in the histogram. but it was a great read and great experiment as well.

I know by reading some of this that quite a few of you guys have figured out how to tune both MAF and VVE at the same time...but that is well beyond my knowledge. maybe at some point I will figure out how...not for lack of trying but for lack of enough usable brain cells

[rjw]

I have beaten it to death 8 yrs ago. What do you need to know?

as much as I can absorb....