I have a question for everyone. I have read a ton of posts on tuning maf, and opinions vary alot. Some say to use the maf tables, some say not to, and some used to use the maf tables, but do not anymore. My question is if you dont use the maf tables, how can you selectivly put in fuel? the inj constant will be everywhere, fuel pressure, same. My car idles like crap, and I was ready to use kvu's maf table advice, then I read him saying he now feels it is wrong. I'm still searching the archives for info, but would like to see this thread get active, with good ideas and suggestions. I think I'm gonna try the batt voltage correction, as my prob is mostly at idle at the moment, and my voltage does drop some, so I'll maybe try that first.
Thanks
Bob

 

I moved the lower MAF tables and it worked great.

 

I don't think what I did was wrong.It's what worked for my car.But grumpy is right,don't use the maf tables as a "fuel table".The only reason to change the maf tables is if your screens are removed and such.But then it's a guessing game.It seems others have sucessfully used the maf table for idle correction.The advice I gave was on a modded maf.If you have a good maf unmodified then use the batt correction table.If it's modded then try the maf table.You can use the spark table to make fine adjustments.

 

I really don't see any reason to not use the MAF tables,if it can trim your fuel to 128/128 then why not.
I feel like its the comparable of a VE table just not as easy to
find the sweet spot.
Although i dont have yrs of tuning under my belt ,people are just
scared of what they cant understand i think.

 

goneracin,

the batt voltage correction table is the best way that I found to adjust the idle to 128/128. (well, I'm more like 126-132, but it's good enopugh for me)

This is because the injector pw is so small at idle, and very few other places... have a look at your scanned data. my pw was around 2.2ms at idle, and I was running lean (136-140). I adjusted the pw battery correction to bring it up to about 2.3ms, which gets me in the right range.

Have a look at the other pw in the other rpm/lv8 ranges. It's much higher, and this means that the correction doesn't effect it at higher rpm.

Right now I'm playing with the spark table to approach 128/128.

I found the best way to look at things is save all the data with CM program, and load it into excel. I get rid of all the bad data (injector pw = 0, PE mode, 125 < int < 131, etc.). Then I graph the BLM cell vs. BLM values.

This gives me a nice view of where I'm rich/lean. The BLM cell boundaries provide a place to decide where to adjust the spark table, and I go from there.

Confused? I've got a graph saved at work and I can post it tomorrow.

 

Alex, please post the graph. Why are you changing spark tables to influence A/F ratio?

 

be careful what you hear and read , you may be getting confused over the controversy with the LT1 which has a VE and a MAF table.

As I understand it - and I may be wrong cause I havent played with it enough yet - the proper way to tune a LT1 maf system is using maf / Inj mult table and you use the VE table IF the system is running in MAP mode with MAF removed.

 

It's up at http://www.alexharford.com/misc/blmvscell.xls (I hope you have excel).

More spark advance means more fuel burned, to get a leaner AF ratio.

I know the RPM range for a cell, that's in the BLM RPM Boundary (in WinBin) and I look at the load values in the sorted excel sheet.

So from the graph above, it looks like I need more advance in cells 1, 2, 6, 10.

The graph isn't entirely accurate, because many dots can appear in the same coordinate. I have a look at how many times a certain BLM value occurs before I decide if the cell is rich or lean.

 

kvu, I didnt mean you were wrong, I had just seen where you are using different methods now, as per gurmpy's advice, and was wondering what some of them were. I'm just looking for the best area to add/subtract fuel, say in part throttle cruise. If blm's are 140 say, and I need to richen it up, (not talking idle now), where is best place for fuel? I'm new at this, and if there is a "fuel table", I havent seen it thus far. btw, I'm not using arap, as my file must have had bugs, I'm using the stock abwn 87 350 bin, with moates adapter and a flash. I'm using the $32b ecu file on winbin. Gonna try to use arap again tho, as the winbin $6e definition file has more adjustment parameters. Thanks everyone for the ideas, and hope to read more on this subject.
Bob

 

Because, there is a better way.
The less you mess with the MAF tables the fewer long term problems you'll have.

OK, you're looking at just the 128 stuff, OK, what happens to all the delta LV8 calculations?, when you dink with the MAF tables?.

It's like setting all the timing tables to 50d. Heck the Knock Sensor will save the engine, and then you'll be a the knock thershold like so many guys like to tune for.

 

"More spark advance means more fuel burned, to get a leaner AF ratio. "

Hmmm....

Doesn't conventional thinking say that spark timing changes the relationship between the combustion event and piston movement and therefore when best average cylinder pressure is obtained? It'll be interesting to see if this works, but I have to admit that I have my doubts.

Winbin shows another 3-D table (BPW Fuel Vs. Load (msec)) where fuel can be changed. I've not tried this but it looks like it might work. Personally, I've just had to change injection constant and I mostly worry about cells 14,15 as usually the ECM is there when PE is engaged.

 

What about if you go into the tables and zero out PEnrichment and all the fuel trim tables, and lock your BLMs. Then you could back out the INT -vs- MAF to properly calibrate the MAF tables.

Once you've done that, I mean tune the MAF tables independent of other fuel trim adjustments, you should be able to have a solid basis to start with and then go back in with your PEnrichment & enrich -vs- LV8 & all that.

I don't know, just trying a different angle by separating variables.

 

No timing doesn't change the AFR.
Timing can influence the reported AFR to a slight degree.

Lean mixtures take longer to react, so they need some extra timing, iw lean cruise, and highway spark kind of run together.

Following the logic of more timing generates more fuel burned we should be trying to 90d BTDC ignition timing.

 

Point is you're not going to do as good of job as GM did.
Unless you physically mess with the sensor you shouldn't need to change the MAF. If you've changed injectors, I really really really doubt you'll find a set that match the operating times of the oem ones, and that is the battery voltage correction.

Remember, KISS.

For what the limitations are of the oem MAF there is just no good cause to tinker with the MAF table other then to say, I did it.

Now for the 400th time, there is a reason to rescale it, but so far everyone's wanting to do it for the wrong reasons, and or they don't want to put the time into doing it right.

 

The maf table is converting voltage to gr/sec.Just like a coolant sensors output is voltage,converted in code to coolant temp.




I thought,"generally" the more spark the less unburnt fuel.

 

I believe that insufficient spark energy can influence air/fuel but timing alone will not have any significant effect. Combustion dynamics is very complicated but in a nutshell, all we're trying to do is get the best overall force on the piston, for the longest period of time. If ignition starts too soon, too much energy will be lost against the still-compressing piston; too late and there won't be enough time to develop max cylinder pressure until the crank-angle is suboptimal

 

timing will not influence the actual air/fuel ratio in the engine, but it can influence the air/fuel as seen by the O2 sensor. If the timing is late, the O2 will see the unburned fuel in the pipe as rich, and reduce the fuel given to the engine. So the timing can actually influence detected a/f ratio.

 

Makes sense, but I'm not sure how much of a difference that will make. None of the burnt charge escapes until the exhaust valve starts to open and that stays the same.

 

Like I said, it will not directly effect the air/fuel in the engine, as that is whatever is in at the time, but it will effect "future" a/f, as the O2 sees unburned fuel as rich, and tells the computer to take some fuel out. The O2 is not seeing direct a/f, but it sees a/f as the result of combustion, and the timing will effect the amount of fuel that goes unburned into the pipes, so in the case of late timing, it will see the unburned fuel in the exhaust, and tell the comp to remove some fuel next cycle. But, to agree with grumpy, you cant just load a ****load of timing, and have the computer just keep adding fuel. Agreed, it is probably a minimum effect, but it would be seen mostly at idle/lower rpms.