MAF & Boost

[OneMeanZ]

Hey guys, I was told on Tech I may get a better response here. I've been reading the Ls1Tech forum stickies and this forum like crazy the past few weeks trying to understand this thing you guys call "tuning" Haha. I've been reading a lot about calibrating the MAF and what that entails, and I thought I was following along but now I'm a little confused as how this applies to FI applications.

In reference to this post from one of the threads in the stickies:

basically gm plops in ve tables & maf tables from year to year to match the stock motor...when you change parts & airflow basically things change...your ve table changes as well as your maf calibration to some extent...what many of us(including myself) do is calibrate the ve table then re-enable the maf & calibrate that...in the end your wot fueling table should be equal to your actual wot fueling verified via wideband o2 sensor. You will hear from people its not necessary & to be honest it probably isnt necessary but it gives me that warm fuzzy feeling inside knowing all of my tables are accurate rather then tricking the pcm in one direction or another.

This is how I assumed you would start tuning an FI car, but as I started reading more stickies I kept seeing people say to run a 2 bar speed density setup. So I'm starting to get confused again...

My question I guess is can you get a 2 bar MAP, tune the car in SD to get your VE tables correct, then dial in your MAF? Or once you go 2 bar is the MAF pointless?

If anyone get shed a little light to help my cluttered brain it would be greatly appreciated, thanks!

[Twitch]

Can't help you, but I'm interested to see where this goes.

[Dozer]

My question I guess is can you get a 2 bar MAP, tune the car in SD to get your VE tables correct, then dial in your MAF? Or once you go 2 bar is the MAF pointless?

If anyone get shed a little light to help my cluttered brain it would be greatly appreciated, thanks!

With 1bar or 2bar tune your MAF is limited to 512g/sec of air flow for fueling so after 512g/sec lets just say weird things start to happen. In most cases 6-7psi will keep you under that limit. Most people run more boost then that so the maf gets disabled and they tune 2bar SD.

There are ways to keep the MAF when going over512g/sec but you need to control those "weird things" to get fueling correct. Once the MAF is maxed you begin fueling X rpm=X fuel and the tune dose not account for more or less air flow at that rpm it just knows at that rpm to fuel this much regardless.

I prefer 2bar SD no maf it is very straight forward tuning and the tune can reference the correct air flows vs rpm for fueling purposes.

[Atomic]

So say you put in a 2bar os, will the MAF still work normally until you reach the 512 g/s limit? I am adding a supercharger soon and plan to run 7-9 lbs of boost, and would like to keep the MAF if at all possible.

[angrygoat]

Depending on the rest of your setup, you might be able to keep the MAF with 7-9lbs. Hard to say until your logging it. If you plan on keeping the MAF, I wouldnt upgrade to the 2bar. Any particular reason you want to keep the MAF?

[Atomic]

I see a pretty big temperature swing throughout the year (20 - 100) with lots of humidity (alabama) and would rather not have to retune the ve table every few months. Plus I like the idea of an actual sensor telling the computer whats going on instead of a calculated value from many other sensors.

[angrygoat]

You could always disable VE and run just on MAF alone. A few people are doing this with success

[RonnieW]

You could always disable VE and run just on MAF alone. A few people are doing this with success

Are they using the stock MAF or is there one on the market that goes above the 512 range?

[lickeyman]

You could always disable VE and run just on MAF alone. A few people are doing this with success

Would also like to see this

[Z06SUPERCHARGED]

You could always disable VE and run just on MAF alone. A few people are doing this with success

I do this and works just fine. When I had car perfectly dialed in both VE and MAF I saw no real benefit from all my logs to run with the VE table. MAF is much smoother and fuel trims more stable in all temps.
Yea I hear all about how VE table is absolutely needed for fueling transitions when you nail the throttle down low (and believe me I do that ALOT)...but
logs dont lie...it isnt needed.
People also say you cant run a MAF with lots of boost...sure you can but I recommend you log every time you drive which I do to make sure AFR's stay within check especially if you drive in large temperature swings (which I dont). I just havnt bothered to switch over to SD yet and since ive been running like this for 10K+ miles it seems to work just fine for me.

Also (at least on the C5 Vettes) the 512 limit is hard coded in the PCM and cannot be gotten around. Newer C6 PCM's depending on engine do go higher though I think.

[angrygoat]

I do this and works just fine. When I had car perfectly dialed in both VE and MAF I saw no real benefit from all my logs to run with the VE table. MAF is much smoother and fuel trims more stable in all temps.
Yea I hear all about how VE table is absolutely needed for fueling transitions when you nail the throttle down low (and believe me I do that ALOT)...but
logs dont lie...it isnt needed.

I have seen in GTOs where this is does not hold true. I was helping a friend tune a 408 N/A GTO in SW FL over the phone and he was getting knock retard at cruising situations. We looked over the graph and the knock retard occured just after a mild to large MAP change. We looked over the tune and the shop left it in MAF only. We reactivated VE and the knock went away.

How do you account for sudden airmass increases? Do you tweak the transient fuell settings? Just curious how you were able to get around it or if it was ever a problem

[Frost]

I see a pretty big temperature swing throughout the year (20 - 100) with lots of humidity (alabama) and would rather not have to retune the ve table every few months. Plus I like the idea of an actual sensor telling the computer whats going on instead of a calculated value from many other sensors.

Let get of the inner-web urban legend; it works better (than static maxed MAF fueling) when you do it right.

[Frost]

I don't know why people dig their heels in and act like VE tuning is some crazy difficult time consuming thing... IT'S NOT. There is no other great reason to run MAF only unless you are driving a Ford and have no choice. Disabling the VE is disabling a large portion of the available control.

SD will ALWAYS be more responsive than MAF tuning for the GenIII's when done right.

[brianfromhawaii]

to tune boost i always do VE... 2 bar or 3 bar.... no maf.. the maf is OUT of the equation, it is removed and disabled in the computer

[Z06SUPERCHARGED]

^ Steve is correct!


ve is not hard at all. copy - paste - done

Never said it was hard....logs just show with or without it works just as good for my application. If it showed anything weird at all in logs or got KR* as mentioned above in heavy transitions id surely turn it back on.
I used VE/maf for a year and just decided to try it without it is all.

[Frost]

Never said it was hard....logs just show with or without it works just as good for my application. If it showed anything weird at all in logs or got KR* as mentioned above in heavy transitions id surely turn it back on.
I used VE/maf for a year and just decided to try it without it is all.

I didn't mean to seem to single you out, really not my intent.

It was a more general rant


These internet myths need to be laid to rest though:
1. SD doesn't adjust well to XYZ...
2. VE tuning takes a large amount of time/is hard.

[Z06SUPERCHARGED]

I didn't mean to seem to single you out, really not my intent.

It was a more general rant


These internet myths need to be laid to rest though:
1. SD doesn't adjust well to XYZ...
2. VE tuning takes a large amount of time/is hard.

No offense taken at all. You have helped me in the past many times in threads and in PM's.

[Reucroft]

The guy from Hawaii is right.

If you run the 2 bar operating system in HP Tuners then you have to disable the MAF. Read the installation instructions for the 2 bar in the help menu - it's speed density tuning only for 2 bar. No MAF.

Now, I don't know why you can't run the MAF for boost applications in HP Tuners, since 5 - 6 lbs of boost should not max out the MAF - I assume its a programming thing????

[S2H]

I see a pretty big temperature swing throughout the year (20 - 100) with lots of humidity (alabama) and would rather not have to retune the ve table every few months. Plus I like the idea of an actual sensor telling the computer whats going on instead of a calculated value from many other sensors.

get your temp bias table correct and you dont have to worry about the swings in temps changing your VE

if you have an issue with your tune changing with the weather, you havent fully tuned your vehicle.

I used to run a 10.7x daily driver in SD.... no issues... 95% of your temp swing issues can be solved with the complex cylinder charge temp bias tables

[miker2]

get your temp bias table correct and you dont have to worry about the swings in temps changing your VE

if you have an issue with your tune changing with the weather, you havent fully tuned your vehicle.

I used to run a 10.7x daily driver in SD.... no issues... 95% of your temp swing issues can be solved with the complex cylinder charge temp bias tables

this is great info--can you elaborate a little more and maybe show an example table that you've done ?