02WS6FREEBIRD

iTrader: (4)

I have QTP headers, so the collectors will throw off the o2 readings some, I understand this, but after tuning the VE and MAF with a AEM WB and the gauge readout for the AFR pretty much matched the HP readout and the WB tune was real close, I bought two new NB's and re-enabled CL, using STFT's only because I thought I had the tune close, with the NB's, and scanning for MAF error percent it has been reading anywhere from ~positive 5 but mostly it's reading negative, and in the lower regions of the maf I have seen it scanning as much as negative ~15 or so....WTF is going on?, the exhaust has two high flow cats at about the mid point of the exhaust and they DO heat up and help, but the exhaust smells strong and I think rich, so are the WB scans that far rich and that much off that the NB's are reading I would say an avg. of negative 8 in the lower areas of the MAF?
Once you get out of the lower areas the numbers are much better, and the NB's are still reading negative, but the most I have seen them off is about 4, does anyone understan what's going on? and what can I rely on?

macca_779

That's totally wrong. If you change any of the tables the changes will occur straight away. VE does NOT take longer than IFR (Not that you should dial in AFR's by fudging IFR anyway)
You would be pretty stupid to not reset LTFT after flashing in a new tune. And when that's done the changes are instant.

The guys that use Roadrunners for their real time tuning would be pretty disappointed if changes to the VE table took 100miles to come through wouldn't they.

02WS6FREEBIRD

iTrader: (4)

I have stock injectors and stock settings for the IFR table, I tuned the VE correctly with a WB in OL, did not use the fuel trims, and then tuned the MAF in OL with the WB, again did not use the fuel trims

LSxPwrDZ

iTrader: (4)

The wideband could also be incorrect. I had an AEM wideband next to an Innovate LM-1 and the AEM was a full point off in certain parts but who is to say that my LM-1 isnt off as well??? Although I have compared my LM-1 to chassis dyno widebands and my LM-1 seems to be right within spec of the dyno readings. Just a thought for you to ponder on.

macca_779

Mate you have no idea obviously. For 1 who tunes off trims anyway. Its not accurate and you can only tune PT off them anyway. This guy has a WB so why are we even discussing this anyway as he should be tuning in OL.

Under 4k is not exclusive MAP. Rather the PCM will be exclusive MAF after 4k. Below 4k is MAF at steady throttle and MAP in the transients.

Your right, resetting doesn't make them learn any quicker. But what is the point on running previous trim data if you have just flashed a new tune in that will run different trims. If one is going to tune off trims its better to use STFT's and turn off LTFT's anyway. That way you don't have to worry about the learning and the logging software can create an average model for you anyway. There are no pros to tuning off IFR mate.. Its just a lazy way for hack tuners to get buy.

Mate if your tuning VE you don't do it with the MAF on.. That would be pretty stupid if you are. Rather you do it with the MAF failed and forced into SD. Like that the VE is the airflow calculation model. You change it, fuel changes. Instantly.


To the OP. If your confident that you have tuned it correctly with the WB to get fuelling accurate. Ignore the NB's. The way they operate is hardly precise and if you have a big exhaust it can wreak havoc with exhaust flow characteristics at idle. Alot of cars I tune with large cams simply wont idle well in CL. Stick it in OL and find an AFR its happy with and run with it.

hymey

the lm-1 is very accurate one of the most accurate i have used. listen to macca, sounds like he is frustrated but for all good cause....

hint- turn ltft off dial in ve with wb and just use stft once dialed in.

Frost

iTrader: (45)

That means what it says; and if you "tune" people's cars by raping the injector table then that says enough about you. You don't need "tuning training" to understand why this is an incorrect approach to tuning. Almost every fuel-related function is based off of the base flow rate. When you lie there, you dick up every subsequent fueling computation.

LSxPwrDZ

iTrader: (4)

I personally would never use the IFR table to change anything fuel related other than the Injector size itself. Why change that when you can change it directly with either the MAF if your running it or the VE if you are SD?

This is what I start of doing, I will turn closed loop off and set the MAF to fault to make the car run in SD. I will then tune all regions of the VE table and get my readings to within 1.5% afr error. Once this is accomplished I then reset the MAF to operate and I proceed to tuning the MAF table to get it within 1.5% as well in all reagion's of the table. Once that is done I will go off and do some idle tuning (which is irrelivant for now) Then I'll turn closed loop back on and let it do it's job. With this process I have never seen the LTFT exceed 3% unless altitude or weather conditions apply.

In 02WS6Freebird's case I think part of the problem may be the wideband. The AEM isnt a very precise wideband for tuning but will get you in the ballpark. What you can do is keep your car in closed loop but make the MAF fault then use your fuel trim's in the histogram to modify your low load portion's of the VE table. This should get your fuel trim's closer to 0 for you and more than likely the narrow band o2's are more accurate at 14.7 than your wideband is anyway's. After you do this turn your MAF back on and setup a custom histogram that calculates your fuel trim's in the MAF table. Now go out and log some data of low load driving and modify your MAF table accordingly as well. This will get your fuel trim's closer to 0 as well. By doing the VE table and the MAF table it takes out any "if" in the equation and should calculate correct fuel delivery. What Macca_779 said about the VCM referencing the VE and MAF (mostly references the MAF when enabled though) is correct. You want your VE table to be as accurate as possible so it will calculate the correct airflow and have the right data to compare to the MAF data.

macca_779

By altering the IFR you are fudging the tune. Frost is 100% correct. Screwing with the IFR might fix your trims, but it will throw out alot of other calculations. YOU DON'T MESS with IFR. Has the flow rate of the injector miraculously changed all of a sudden. NO. If you alter timing has the VE of the engine changed. Hell YES. Thats why you tune VE, not IFR. You say you've tuned 400 cars and yet you still have no idea.

You say before that you leave large cammed cars CL. I guess you've never heard of overlap then and it inherently giving false lean AFR's at low RPM. This is why I tune OL for the bigger cammed cars and run them leaner as they are getting more fuel during combustion than what the O2 sensor is saying. Better stability is a bonus and your not wasting fuel.

You say that you leave the VE alone and only tune off the MAF. I hope you run exclusive MAF then as if you honestly believe that the SD Model is largely ignore below 4k your dead wrong.

Here is the description straight from B0120

If engine speed is less than this value (4000rpm), then the PCM uses a dynamically calculated airflow value to determine grams of air per cylinder.
While the airflow is in a "steady state", then a correction factor is updated based on the airflow difference between the MAF sensed airflow and the MAP calculated airflow.
During rapid changes in airflow, the correction factor is applied to the airflow calculations to compensate.

If engine speed is above this value, then the PCM will use the MAF sensor exclusively (if not disabled by DTCs) to calculate grams of air per cylinder.
No updates are made to the airflow correction factor.

jezzab

Tuning via adulterating IFRs is for "tuners" that need to learn how to tune correctly and look up a bit more about how the PCM works within itself and how data is referenced.

The only time the IFR table should be ever changed is if larger/smaller injectors are added or a manifold FPR is added and then flat lined.

Jez

2002_Z28_Six_Speed

iTrader: (19)

Someone should lock this one down before there is more crap than mertitable info in this thread. It is starting to turn into a pissing match.

edcmat-l1

iTrader: (10)

Ah, the MINISTER OF MISINFORMATION.
As I've said in the past, you should be banned for shear stupidity.

Patrick G

iTrader: (14)

Here's my 2 cents. Fresh narrow band O2 sensors that are fully warmed up are much more accurate to use for tuning when chasing stoich in idle and part throttle tuning. They are much more accurate than WB sensors. This is why the factory uses them. The problem occurs when using NB sensors with long tube headers and no cats. It takes much longer for the NB sensors to give their most accurate readings and they are not to be trusted until there's plenty of heat in the headers and the sensors.

Once fully warmed up, if you're still seeing larger than 2-3 percent swings in STFT, then further tweaks of the VE table are needed. I would NEVER jack with IFR for STFT or LTFT tuning. It affects too many other tables. You'll wind up chasing your tail.

edcmat-l1

iTrader: (10)

Well lookey there, someone has a new title LOL
LAUGHIN MY *** OFF!!!!

Gh0st

iTrader: (3)

This thread was a good morning laugh.

YellowToy/A

iTrader: (1)

Patrick

NB sensors are used because they are cheep and do a good but with finding 14.7 or there about. Your are correct that they must be warm. A wide band has heaters in its O2 sensor. That is why it is better with long tubes.

edcmat-l1

iTrader: (10)

AH, Grasshoppa, NB have heaters too. Although they usually don't work as well because of the LTs. We usually use Vette downstream 02s as they have a higher wattage heater. Sometimes it helps, sometimes not.

YellowToy/A

iTrader: (1)

OK
What I should of said is that NB have heater assist. WB will operate in cold condistions.

2002_Z28_Six_Speed

iTrader: (19)

I have always thought your responses to be frank and sharp and not always right.

I can't say that a NB sensor is cheaper than a WB. That seems like flawed logic to me. There isn't really a price differential. But, a WB "works better" because it is an active oxygen pump cell. Some have a heater designed for aftermarket applications in mind. Stock narrow band is designed for a smaller heater because they know there is going to be a cat close to the engine and it won't need a bigger heater.

NB sensors are nice because of the mathematical algorithms that the PCM does on them and the weighted averages. This math is designed for the target of 14.7 for emissions. This part is COMPLETELY the fault of how the PCM is programmed to handle the NB O2 sensors. I think you can find that NB sensors are a narrow band; not a point measurement. (They are not good for one ratio only. They can handle from about 15.3 to about 14.)

There is some data out there on NB sensors and I am really sure the error on them doesn't instantly go to 100% as you deviate from unity lambda.

YellowToy/A

iTrader: (1)

You can look at the cost of nb sensor vs wb sensor and see that the cost of the wb is 2X the cost of a NB. Then you have to look at the cost of the controller. It is 3 or 4 times more for a WB. System cost to an OEM is somewhere 2X to 3X for a wb. You can calulate this if you want.

As far as "NB sensors are nice because of the mathematical algorithms that the PCM does on them and the weighted averages. This math is designed for the target of 14.7 for emissions. This part is COMPLETELY the fault of how the PCM is programmed to handle the NB O2 sensors."

This is the same to the ECM. No advange to NB or WB. This is all about cost to the OEM. Eletronic hardware and warrenty. WB have more problems then NB.

I think NB sensor will go from 14.9 to about 14.4 at best. I know that they were designed to switched around 14.6 to 14.7. Once you move from here good luck with that.


I like poeple who think they know what they are talking about and treat that as fact. Have fun