I reread my first post and have come to some conclusions since then. Israel, I reference your post to discuss that conclusion which is open to everyone to evaluate.

Let's all agree on a few things first. One, a Bosch O2 sensor will read 0.450V at a few tenths above stoich or slightly lean. If this is the case, then GM has tried to compensate for valve overlap in the PCM program by putting the crossover at 0.425V. This last sentence is only theory but I cannot explain why they did what they did any other way.

Now let's look at your cam. LOTS more overlap than stock. This means that more fresh air is bypassing combustion and going to exhaust. This reads as a lean condition with the O2's...if you have not modified the O2 crossover. So to compensate, the PCM dumps more fuel to get to what it thinks is stoich.

This is separate from the MAF calibration. Remember you are calibrating the MAF in reference to the crossover point set in the PCM memory. Bad crossover point, bad MAF calibration in reference to TRUE stoich.

Try 400 (400mV) as your crossover and PLEASE report back. My big cam wants to know this crossover better.

Here, you need to put in BLM Locker. Get the BLM's to lock on 128 any time you go into WOT. Further, zero out your WOT vs RPM table. Only adjust with your temp tables. On the temp table note, get them all the same in the FULL operating temperature range so there is no variance there.

Do above as well as the O2 crossover and report back.

Ben

 

As far as the temperature tables are you referring to the "%change to fuel/air ratio vs cool temp at WOT"? If so that is all set to 16 in the normal operating range from 56C to 104C.

Or are you referring to the "Open Loop AFR vs Coolant Temp vs MAP" table?

Also were is the table were I can change the crossover? I have looked over all the tables I would think that it would be in in C.A.T.S. tuner and am unable to find this function. This does sound like something that would be useful though.

I'm pretty sure I have the BLM locker in place as anytime I go to WOT it locks the BLMs out to 128 both LT and ST and uses the PE table for referance. However if I keep it from going into PE by setting the MAP threshhold to enable WOT to 255kPa in the constants I can tune strictly the MAF all the way through the RPM range(it won't lock the BLMs out in this mode unless I do some tweeking to two of the constant values in the constant table).

On another note too I emailed Racetronix and am trying to get the offset values given the entire voltage range for my injectors. I may also set my injector constant value a bit higher as well as i think 38.01 is a little low for my 38# Delphi multec injectors. If all else fails I may just use the stock offset values up the constant value and play with the individual fuel trim tables a bit then go back to the MAF tables and see if I can't get the values raised some. Even if I have to change the temperature values to get my MAF values to raise so that my PE/WOT table is not so high I may have to go that route(this is assuming that this will even work in the first place).

Hmmmm........... puzzled as to which route to take.......

 

Yes this is the table.

"Fast O2 Rich/Lean Threshold" is the table.

When PE mode is enabled, the PCM will read 128 no matter what you are really at, if I remember correctly. It has been so long since I tuned without BLM Locker. Better confirm this.

 

Something that worries me is the fact that while datamaster is reading Short term BLM's dead on 128 and Long Term BLM's within 3 plus or minus on both banks my wideband was registering 12.7 + or - .5 throughout the rpm range. My question is is there anywhere in the tunercat settings where the pcm can be adjusted to think that 128 BLM's is a 12.7 AFR? If so how can I get this changed to read accurately?

Thanks.

 

As Blackhawk mentioned above, this is affected by the O2 Lean/Rich Swing Voltage table.

Also, as I mentioned above, the stock O2s will vary depending on exhaust temperature. At WOT, temp. is usually much higher than idle/part-throttle.

 

Ok so based upon the above statement by JSK333 it could be that my temperature is lower and and thus the O2s are reporting leaner than it really is making my true AFR richer than stoich(verified by the wideband). My O2s are located about 6 to 10" from the LT header flange down the exhaust stream.

1) Could this in fact be a great enough temperature drop without a catalytic converter to cause this effect?

2) Is the initial statement I made based on the quote correct?

 

What Solomon said is correct but I am pretty damn sure that it would not make your final AFR be off by 1.5 points.

 

This is something that I have been dealing with lately and I have to think that you are going to have a hard time dialing those injectors in without a LOT of trial and error. I tried to find a spec sheet on Delphi's site and it doesn't look like anything is available for the general public. You might ask them directly.

Here is a link to my method for scaling injectors with well-known data into the LT1 PCM. It seems to be working because the car is VERY easy to tune and idles perfectly (with a basically stock engine and SD 63# injectors at 59psi -> ~73# actual):
http://www.impalassforum.com/vBullet...d.php?t=236016

The issue isn't centered around the coordination of the squirt timing versus valve opening. The real issue is the PCM's ability to accurately predict how long it needs to open the injector for the required amount of fuel at all loads. Here is another even more detailed read on the subject:
http://calibratedsuccess.com/Assets/...%20Article.pdf

 

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