jub jub

I've read so much about adjusting the MAF tables that I don't know what to believe. I need to ask this again, even though there is more information out there than you can read in a month but the question is this...

If you retain the stock MAF, but add a high flow filter, do you need to adjust the airflow vs. frequency in the MAF table, and if so why?

Could someone who really knows their sh*t please explain!

Thanks.

jub jub

Nobody?

Let me ask it this way, can you get a good tune by just adjusting the VE tables and leaving MAF alone?

12secSS

iTrader: (30)

Next time give people more than 2-3 hours to respond to your question.

Now, as for your question ... if you just add a high flow air filter to your vehicle, you do not need to modify the MAF table. Hell, the VE table might not need much adjusting either. If you port your OE MAF, replace it with a larger MAF, or have mods that affect the A/F ratio as seen by the ECM (say long tube header), then yes you would need to recalibrate your MAF Table.

jimmyblue

iTrader: (11)

Stock screened MAF is pretty tolerant of any
lid/filter changes.

Descreened MAF response may be altered by
any change to the airflow pattern / distribution
across the face. An air filter is unlikely to do
this but some lids (especially very curved air
plumbing) will. Corvettes and trucks seem to
have it worse than F-bodies.

A "high performance" air filter which is an oiled
type, over time will deposit some of that oil onto
the MAF sense elements. This disturbs the thermal
characteristics and the MAF output drifts. It's
worsened by over-oiling.

You want to adjust (or not) the VE table and the
MAF table based on what you know to be wrong.
In general you only need to mess the MAF table
around, when you change the MAF physically or
(perhaps) change the airflow distribution right in
front of a descreened unit. MAF is pretty self-
contained. VE however is the sum representation
of everything back of the intake main plenum,
which is a lot of ground to cover and a lot of
mods affect.

jub jub

OK, I understand what your saying but theoretically speaking, let's say the stock filter remains unchanged, why would you still need to calibrate the MAF if you added a cam and headers?

Since a MAF measures the X amount of airflow across it's resistors and reports back to the PCM with "X" frequency. Then adding a cam and headers helps the VE of the engine and the MAF should register that as increased airflow at a given RPM. Correct? This is taking into consideration that the MAF and everything in front of it is "factory"

I guess what I'm trying to figure out is what causes the disparity that adjustments need to be made to the MAF table if the MAF is stock. Is adjusting the MAF just another way of getting around a tuning problem?

jimmyblue

iTrader: (11)

The only fly in that particular ointment is, a big cam's
airflow reversion may fool the MAF if it's enough to
pulsate all the way out the throttle body; sort of
double-counting the air, I guess.

Other than that, you shouldn't have to.

Cam and headers should affect the VE much more
than the MAF but low RPM is a combination of the
two and people may be tempted to fix the wrong
element. But at low RPM where reversion exists
a little MAF tweaking may be the icing that makes
the cake.

jub jub

Gotcha! OK, I'm beginning to slowly get the jist of this. Thanks guys!

Patrick G

iTrader: (14)

Why even run the MAF if you have the tuning software? The only reason I can see is if you want to run a Dry Shot.

DWillTA

iTrader: (3)

Is adjusting the VE table from 4000 to redline easier and the most accurate or is sticking with the MAF sensor for 4000 to redline and adjust the PE & commanded AFR more accurate?

I have started to tune my car after a cam install and weather permitting will be at this crossroads soon. I feel no ill effects running the car in SD mode for tuning. I understand the VE table needs to be close all the way to redline for SD to be accurate.

What are the recommendations of the people running SD and why? I like SD for the simple fact it eliminates the possible inaccuracy's of the MAF to report airflow correctly.

I maybe totally off base. I am still learning myself, so any insight is welcome.
Thanks

WS6FirebirdTA00

iTrader: (33)

i have been running SD without issue since feb this year. IMO, the way the maf works can give split seconds of false feedback as well as inaccurate information. after studying fluid flow in my fluids class and seeing what needs to be done for perfect laminar flow, i will not go back to a maf. turbulance in the air stream can cause false readings, they could be there, may not be but who know? but there is a chance, very good chance, there is some turbunace n there at some point in time, that is enough to give false readings. for me, i like to tell the computer what it really sees. is the maf accurate? i am sure it is or gm wouldnt have used it, but i cannot comment or give my opinion becuase i have never took the time to really determine how accurate it is in unsteady state conditions that our cars ACTUALLY see from day to day.

i just find better throttle response wtih the maf gone, also the restriction of the stock maf is no gone since it is replaced with a pipe. and no my trims dont go crazy with temp changes either, the car is equipt with enough sensors to make proper changes, whether is it 100 or 50 deg out i get the same data in my logs. a lot of people say sd is better or maf is better without any info to back it up. this is my reasoning, may not be 100% right but its worked so far so im going to stick with it...

jub jub

Ahhh...what a breath of fresh air! Kind of like the good ol' days when you picked a good day to jet the Holley for good 1/4 mile times! Of course, all we ever worried about was WOT!

y2k_ta

iTrader: (80)

If you're tuning the car or having it tuned, just delete the MAF and be done with it.

redtail2426

iTrader: (10)

i dont think the computer uses much of the info from the MAF during unsteady airflow periods.Like throttle transitions and lower rpm it uses mostly VE.But on the high end of the rpm and power scale the MAF is used because it is very accurate at measuring steady high flow situations.I am leaving it on my car.It can be run without but make sure your VE is dead on.

WS6FirebirdTA00

iTrader: (33)

the only seady state the car will see is 0 mph at a fixed rpm. our cars NEVER see steady state conditions. as rpm increases and speed increases airflow velocity and pressure changes, these changes mean its not steady state, which introduce error in the maf, at rpms over 4000 it only uses the maf so the errors are real and not accounted for seeing it goes directly from the maf, yet another point i have to not run the MAF.

every gear change or let off of the throttle for an shift with screw with the air at the MAF. and when you change gears when you are romping on it how often do you go below 4k rpm? you dont because from 1st to 2nd is the lowest rpm you will see and that is right at 4k, then you have slight wheel spin, rpm fluctuating at constant throttle, more error...

redtail2426

iTrader: (10)

by steady i mean not turbulent i should not have used the word steady i mean airflow that will not induce any turbulence like slow moving airflow and quick throttle transitions.The air is smooth flowing at higher load conditions

redtail2426

iTrader: (10)

I think with hp tuners 2.0 MAF tuning will be super quick and easy also especially with a wideband.

WS6FirebirdTA00

iTrader: (33)

airflow will be turbulant still. as you change the velocity of the airflow, the boundary layers move and can separate, when they separate you get turbulance. when you get turbulance the resistors cant be properly or consistantly cooled for accurate readings.

and dont think i am arguing here im just giving up the reasons that i ditched the maf. plus not many people come on with many real reasons to ditch it. yeah 2.0 makes it easy to tune it now its great.

Bink

Listen to WS6FirebirdTA00's logic (and excellent info) and keep in mind the MAF input is heavily crutched by the PCM under 4000 rpm. If it was accurate below 4000 it wouldn't be crutched.

I was once one of the stubborn MAF holdouts ( HumpinSS will vouch for that ). If you have a decent size cam SD is the way to go - throttle response alone convinced me.

RedHardSupra

iTrader: (1)

i'm a weirdo: i drive in SD, but i kept my MAF. why? double checking, i always compare how the two air readings compare. i like maf for dry spray and drag in general (very steady state).
for roadracing, i prefer SD, throttle response is nicer. also, i worked on few cars that have reversion issues, and SD was the only way the car would run.

so it really depends on what you got and how you wanna use it.

jub jub

I'm going to try Speed Density tuning. Can I just shut the MAF off using the software without physically disconnecting it?