MAF tuning question

[AADrcw]

Alright let me start out by saying I am a newbie and all this and trying to take my time learning. So far everything has been going decent (I think), I have been following the sd tune guide in the hp tuners help section and also have been using this guide here http://www.michigansnowmobiler.com/h...ons%20rev2.pdf.

My car is a completely stock 2004 GTO M6, The only "mod" to the car is a k&n drop in factory replacement filter the PO put in. I started by doing the VE table like the guide said, After a few logs and changes I realized that adding 15% to the VE table to start was a bit much since this was a stock car. I tried logging with the completely stock VE table and it was very lean. I then added 5% across the board to the stock VE table and that got it very close. I tuned the VE as close as I could get it, Mainly -2 and -3 through out with a decent amount of 0s, and from that point it seemed like any change made it worse. I also found out that my car seemed to hate the table being smoothed (probably me not doing something right) But table looks close to the stock table in terms of smoothness.

After I got it close as I could I moved to maf tuning. I followed the steps in the HP tuners help guide first, Upon starting the car the afr was very high, Like 16-17 at idle and slightly higher while cruising. (I didn't drive far like this, didn't want to risk damage to the engine). So I came back and tried using the second guides method of tuning in maf only mode, this gave the exact same result. Very high afr at idle and cruise. I ended up adding 15% to the entire table to get it to be in the -2 to -4 range just so I felt comfortable logging it in the first place. That is where I am now.

My question is this, First Am I doing this right so far? Second, Should the factory tables be that far off on a stock car? Third, Could the k&n drop in really flow THAT much more then a stock filter to cause this or is there something else causing the factory tables to be off?

Just to add, When I first got HP Tuners I did some logs messing around with it to get the hang of the scanner and what not and on my test logs I saw my LTFTs go from 5% all the way up to 16% at some points. Those numbers were seen on the car running the completely stock tune and nothing changed.

Thanks in advance for any replies, I can post my stock tune and the one I am currently using if needed.

[5FDP]

When it MAF only mode, the AFR should still stay around stoich. It should never be super lean if the MAF is working correctly.

I followed that same thing you posted for SD and MAF tuning and it works pretty good. I followed and made the OLMAF tune to a "T" it ran great off MAF only and was maybe off by 2% in stock form.

And the stock VE is normally pretty far off in stock form. My truck had a 15-18% error the first time I went out. It would idle around 16.0, I'd be driving around with it anywhere from 15-17 afr. And because I'm just cruising and not beating on it, running that lean didnt even matter. After logging and making changes it went down to 5-9% in most spots the 2nd time out, after that it went down to 2-4% and I just left it at that.

[AADrcw]

My VE table took about 4-5 logs to get it into the -2% to -4% range, I still have about 3-5 cells in the 1600 range that refuse to go below +1% for some reason but other then that the table is pretty much all 0 to -4%. I'm not sure if it was me causing it or if the car just wanted to be picky but it seemed like everytime I would log then make changes and immediately do a new log the changes had a adverse affect, some cells that were good would be lean or very rich and then ones that were off would magically be right where they needed to be, I never could get all in one area to match up just right.

As for the MAF only, Would the fact I had to add 15% to the entire MAF table to get it away from being lean show the MAF is failing or I have a vacuum/air leak somewhere? The car ran fine and didn't set any codes before tuning. About 2 or so months ago it threw a MAF code (can't remember which code though) and I cleaned the MAF with MAF cleaner and the code went away and never came back.

Should I keep trying to tune the MAF? or should I flash back to stock so I can drive it safely till I figure out whats causing a lean condition in MAF only mode?

If there ends up being a issue somewhere, whether a failing maf or a vacuum/air leak of some sort will that totally throw off my current VE table?

[5FDP]

Can you post your OLMAF tune that you made, perhaps something isnt right.

Because you should never have to add 15% to the MAF table in the OLMAF tune to get it to not read lean. It should read 14.7ish all the time no matter what as the MAF is reading airflow and adjusting everything.

[AADrcw]

Here is the OLMAF tune without the 15% added. This tune also has my modified ve table in it. MY-GTO-MAF TUNE 1.hpt

[5FDP]

Your LTFT are disabled, they should still be on.

I also reset fuel trims before I log data. Otherwise it should be in maf only mode with that tune. I'd clean the MAF again, any oil on the maf doesnt help. Only reason I never run oiled filters.

[AADrcw]

Alright, Would it be a problem enabling the LTFT with the B1S1 o2 removed for the wideband while tuning? If I can enable them would that explain why its running so lean in maf only?

I planned on getting a otr intake after I get a few other things taken care of so I wasn't to worried about it for the time being, I may go ahead and pick up a normal filter anyways though.

[5FDP]

So you have the B1S1 oxygen sensor removed and wideband in place currently??

Because thats a big problem, maf tuning needs both o2 sensor plugged in and working. Without that bank knowing whats going on, the readings arent going to be right. It's VE tuning that doesnt use the o2 sensors.

You'll have to weld in a o2 bung for your wideband before the cat conveter on that bank then.

[AADrcw]

Yes I have B1S1 removed and I am tuning it using a WB.

I am doing the MAF tuning by using MAF-AFR error histogram., If I were tuning it using the trims you would be correct, please correct me if I'm wrong but the computer doesn't use any trims (Long term or short term) in open loop anyways so having the front o2 back in with LTFT turned on would literally make no difference since I am tuning in open loop maf only.

[5FDP]

Seems I mixed myself up there, but anyway when in maf only mod the stock maf curve shouldnt be that far off to cause it to be that lean at idle, that just seems way odd to me. Never heard of someone needing to add 15% to maf just to get it close on a stock vehicle.

[AADrcw]

I haven't either which is why I was so confused when I saw it. A friend of mine suggested that maybe my car had the MAF calibration off from the factory or possibly they get them close enough that the trims will take over. Another thought is (and I'm really reaching here..) that since its an Australian car the MAF table is correct down there and that far off here on the other side of the world.

I think I am going to try to tune it by adding the 15% and get it dialed in, then watch it for a few days/weeks and see if the values float. If they stay correct then it was just that off from the factory.

[jimmyblue]

Aussie cars held onto the 75mm MAF longer than we did,
and that piece has a different cal curve than the 85mm.
Not sure what year GTO had what, maybe the LS1-LS2
transition is where that cut over. Holden Monaro had the
best looking 75mm MAF table in my collection. If the MAF
table runs out to 511g/sec at 12kHz it's a 75mm table.
But there are plenty of malformed ones from GM too.

It's my opinion that, poor hygeine, kooky plumbing and bad
(as in unpopulated or flat-lined, from factory) MAF tables
aside, the MAF doesn't need touching. Of course that K&N
falls under "hygeine problem" and tends to make the MAF
read low. A proper cleaning ought to precede any attempt
to tune AFR and air mass accuracy.

I really do not like all of these "methods" that come and go.
Most of them purport to achieve accuracy but really only
deliver consistency. We do not have the instruments we need
to get absolute in-taken air mass accuracy let alone cylinder
air mass accuracy (!= in-taken, some reversion or shoot-through
is often present especially once you start trying to increase
HP by resonant filling and extraction, raise cam overlap and
so on). All of your AFR-error-based tuning schemes fold fuel
shot errors into the airflow. What do you know about delivered
fuel mass, other than some injector data sheet? Not a damn
thing, yet you're going to jack the VE table around as if it's
the only thing responsible for any error (and you'll willingly
believe the meter, for that, despite it being pretty spoofable).

It's too bad noone offers a straight MAF calibration service
by mail. Or the short term rental of a truly calibrated one.
Tuning air by AFR is one equation, two unknowns, probable
fail (but more likely endless fiddling, changing something
that is not entirely responsible and so never an entirely
satisfactory outcome.

"A man's got to know his limitations" - Dirty Harry, "Magnum
Force"

[Russ K]

Disable the STFT open loop, as it can cause STFT's on the bank that the stock O2 is still in place. As for your 15% AFR Error on a stock engine with a stock airbox, the Maf is most likely failing. Very common on a 10+ year old car. And cleaning a Maf won't fix a Maf code.

Russ Kemp