RedHardSupra

iTrader: (1)

ugh..that was a joke people, see that smiley at the end? haven't i repeated myself enough times to know that i refuse to dick with ifr for anything but injector sizing? i've made my points already, i'm not repeating the rants again

SmokingWS6

iTrader: (1)

Might as well solder resistors in your o2's or switch to synthetic blinker fluid.

Time GM spent caculating ifr = years
US = few hours

I trust gm knew exactly what our injectors flow so i'll stick to ve and other metods too.

way2slow

Back to my question about the weather. Assuming you can get a close VE table and MAF table in mild climate conditions or just a couple tunes for different times of year, wouldnt this be sufficient? In stock form GM had to account for changes in climate somehow. There has to be an assumed amount of error involved with a MAF calculation for the car to survive for 100k miles right?

Does anyone know how GM calculates MAF tables? Someone mentioned that the Monaro had an intake tract that was a straight shot, similar to the F-body. If this is the case and GM calculated the MAF in realworld situations(i.e. in the car) then it would make sense that my new calculated MAF values are very similar to the Monaro and why would I not use these new values or the Monaro table? If part of GMs calculation included the airbox, bellows, and all other intake tract pieces then my new modified intake tract should have its own calibration correct?

Bink

Flow rates aren't exactly rocket science- at least for most of us.
I guess square roots might be intimidating to some.

I can solder, do basic math and spin a wrench.

Amazing how people react to facts.

jimmyblue

iTrader: (11)

I'm pretty sure GM fudges the MAF tables to make things
"best fit" to the vehicle. For example all of the trucks use
the same Delphi MAF but you will find different tables on
various models. The second-order effects like airflow bias
have to be taken out of the MAF's delivered signal and
the table is the only handy place to do it.

The Holden MAF is, near as I can tell, the same one used
on the F-bodies, the tables are similar as far as the F-body
goes but the Holden doesn't "dead head" it at 11250Hz -
it goes right up to 511.9g/sec and 12kHz. Funny how the
MAF hits both of the PCM code limits simultaneously. Almost
like on purpose.

Speaking of flow rates, I was looking at a chart I plotted up
of the IFR tables vs sqrt (vac kPa + 400) and damned if it
isn't just perfectly linear. Like there is no fuel fade in the
system. That's an "interesting" approximation. Dunno how
you'd address that properly, I guess people just cheat it
with the PE vs RPM or something. Or a return style FPR.
Something to think about, though; just how close and
stable is your real, rail pressure to what's embedded in
the fuel-side calculation, across fuel demand?

P Mack

iTrader: (6)

It's funny that last year everyone was trying to calculate ve tables from the maf and now it's the other way around. I know that's a useless comment, but I do have 2 things to add.
- Somebody posted that they had better results with VE when they moved their IAT sensor to right before the throttlebody instead of the lid. Don't remember who it was but it might help the inconsistencies you're seeing with weather.
-Has anyone compared Dynamic airflow to MAF airflow on a stock car with stock lid and everything else? I'm thinking they might not match as well as you guys think.

Another_User

1) That would make sense, especially if you re-tuned after moving the IAT.
2) Of course I noticed. And you are right. It is a little odd.

Anyways, I have new results from my testing over the last few days:
1) Scaling the entire MAF table makes the upper frequencies run rich.
2) Shifting the MAF table left makes the lower frequencies run rich.
3) With some tweaking, there appears to be a comfortable middle-ground. i.e. shift the table to the left, then multiply the entire table. It requires a lot of "fudge factor", but I have gotten MUCH MUCH better results by doing this than any other method. I have a fairly pretty trim table to post later.

P Mack

iTrader: (6)

AnotherUser, are you judging your results of your changes based on fuel trims, or on how closely dynamic air matches maf airflow? Also has anyone tried playing with all the new dynamic airflow parameters like map deltas and ve correction factors?

Another_User

Fuel trims. If I touch those other tables...crap....who knows what will happen?

SmokingWS6

iTrader: (1)

I noticed my caculated engine load at WOT is 70-80% Sounds like a good canidate for a new maf table to me.

P Mack

iTrader: (6)

Maybe you should try getting maf to match dynamic air instead. If you just use fuel trims you could possibly have rich ve and lean maf and when they are weighted together it comes out right. But other times when the weights are different you have problems. Maybe that would be unnecessary but it's something to look at.

Another_User

I tried that. The MAF table I made sucked. Also, the SD airflow is by MAP and RPM, so it should not be affected by the MAF airflow, it should be affected by the trims though.

way2slow

In general, will an increase in MAF table values bring positive LTFTs closer to 0?

RedHardSupra

iTrader: (1)

think about it in generic proportions: lets say your stock flow is 10 units. you port your maf, and you really flow 12 units. your stock calibration still says you have 10 units, while you're flowing more, not reporting some extra air that you got coming in. that causes lean condition. so increasing maf values generally should cause richening up the mixture, as the computer is trying to compensate for more air coming in.

SmokingWS6

iTrader: (1)

To me thats why it seems maf should be done before ve tuning. Or else you'd be rich from correcting the VE table and then dumping in a higher count maf table.

HumpinSS

iTrader: (1)

What would be even better would be a way to force MAF only usage like we force SD usiage.

P Mack

iTrader: (6)

I don't understand your reasoning. You can do the ve table by itself so the maf doesn't interfere, but you can't do the maf table without the ve table being figured into the airmass calc.

Or are you talking about not going mafless to get your ve table cause you have an auto?

Another_User

I have been thinking about that. I would *think* it would use MAF only to determine fueling if you unplugged your MAP sensor. Or somehow programmed it to fail the MAP with it plugged in.

As far as fixing your MAF table first, with the VE table being used for fueling, it won't work. It can't work. You VE table affects fueling up to 4k rpms. VE first (until we find a way to fail the MAP sensor, or determine if the PCM will use MAF only with the MAP unplugged).

txhorns281

iTrader: (12)

That's why for VE tuning people always say disconnect your MAF. That way it's not biasing any fueling operations. Once the VE is correct then you align the MAF to that. The way you record data for recalibration is still in SD mode.

God Forgives I Dont

I've ran with my MAP unplugged by accident for about 5 weeks (well may have been intermittently disconnecting not sure sense some of the time it felt OK). I found it bogs really badly until 70-80% TPS then it kicks in full force and try's to jump out from under you. Not to mention it didn't want to down shift when WOT, unless I manually shifted it down. Didn't have tuning software at the time and wouldn't have known to scan it for that anyway. Interesting Idea though if it would allow us to calculate MAF Pre VE tuning!