IROCZ28dan

Current setup is 350 tpi, vortec heads, lt4 hotcam, 24# injectors.

Maf setup running 6E definition.

Max timing is set at around 23-25 degrees.

At WOT, I have my PE set to 13.7 commanded, and recieve a 12.7-12.9 actual on my wideband (LC-1). I have tried messign with the MAF tables and their corresponding scalars, I have tried adding/subtracting timing...no matter what I do I just cant seem to bring the two any closer.

Idle, part throttle, and cruise are all in the 126-130 BLM range for the most part.

Any insight is appreciated, I'm at a loss on where to go from here...

19doug90

if im understanding your question right i think this might be what youre looking for, but my only experiences are with speed density so youll have to bear with me

PE basically takes your VE table which ideally should be shooting for 14.7, and changes all of the values by whatever % you put in.

so if your tables are for X % of change from 14.7 that should put you at 13.5 but your ve table is richer then that, you just get whatever % change you put in

id also like to point out that 12.9 is a pretty healthy a/f for WOT 13.7 is getting pretty lean

IROCZ28dan

Thanks, but, that didnt help at all. I don't think you are understanding my question correctly.

Granted every engine has its own sweet spot, but I know as a rule of thumb 12.7-12.9 generally is on time for peak HP. I know 13.7 is pretty lean, but thats what my commanded A/F ratio is, my actual is in the 12s. I'm trying to make it so my PE commands 12.8 and I see 12.8 on my wideband.

Currently if I command a 12.9 AFR I will get something in the neighborhood of 11.3.

Something in my setup is way off, I'm trying to figure out what it is.

RBob

iTrader: (1)

I see two things that require changing. To get the commanded AFR richer the PE % AFR ratio needs to be changed. This is tricky as it is a percent change from the stoich value. And is a combination of two tables:

One vs CTS and the other vs RPM

Look for posts by traxion, he explained this rather well and IIRC released a small program to combine the tables and stoich to the commanded WOT AFR.


To get the actual AFR to match the commanded AFR is the MAF tables. However, there are catches to this. Need to be sure that the MAF isn't being ignored and the ECM is creating a default value. Compare the two airflow values in the ALDL stream to each other. One is the raw value while the other is the one used by the ECM. If they don't match then something is up.

Then change the MAF tables & scalars so that the commanded AFR matches the reported AFR. Of course this depends upon whether the WB is reporting correctly.

RBob.

IROCZ28dan

This is where it doesnt make any sense to me.

For the record, both MAF raw and MAF gm/sec are reading right on with eachother, LV8 is reading close to the MAF input as well.

Now, I tried to globally adjust the upper tables, originally trying to lean "stoich" out and make it so my PE added fuel and the commanded/actual came closer. Well, when i moved each value from table 4 and 5 back 1 spot, somehow my actual AFR became more rich, reporting a 12.2.

I followed all instructions with my wideband as far as calibrating goes, and it is installed just downstream in the y-pipe of where the 2 banks meet, pre-cat by about a foot. As far as I can see it is calibrated...it fluctuates around stoich during all driving and idling, and reads fluctuates around 15.5 on the highway (where my highway mode fuel afr is set).

Perhaps I need to move the tables around more?

I cant think of any way to really do the upper tables without being on the track or dyno...its hard for me to reach 150-225 gm/sec and stay there consistantly on the street without breaking multiple laws.

RBob

iTrader: (1)

When you made the global change to the upper MAF tables, which way did the injector PW go? That would be the tell-tale sign of whether it is being leaned or made richer.

RBob.

RednGold86Z

iTrader: (1)

If you're getting 12.8 while you commanded 13.7, you have about 9% error at that point. You are getting more fuel than what you need, which means the MAF voltage is corresponding to a too high actual airflow at that point.

So, you need to reduce the MAF air flow at the higher voltage levels by 9%, and increase your commanded PE enrichment by 9%, and you'll see commanded be 12.8 and actual be 12.8, ish...

It will take some blending to get it from the good points to the bad points.

Just be sure you really trust your wideband.

IROCZ28dan

Thank you both for your input.

RBob: I didn't even think to look at PW...must have had a brain fart.

RednGold86Z: Thanks for your input. I do trust the wideband, its been in the car for only about a month and a half right now. My MAF has been modified (no screens, and a few fins have been removed) so I know it needs recalibration.

Any thoughts on timing with the vortec heads? I have been told no more than 25 degrees due to the heart shaped combustion chamber being very efficient...however I have seen other timing tables on this website that show people having upwards of 30 degrees advance. I dont know if those people are masking detonation with too much fuel or if they just are that good...

Any more advice is appreciated...

RednGold86Z

iTrader: (1)

My first calculations were a tad off. 12.8/13.7 = .934, which is 6.6% error, not 9%. Not sure what I was smoking when I came up with 9%.

I'm surprised that the screens off made it richer. Common sense says it should have more air that is not reported, and thus be leaner than commanded.