I have a 95 Z (M6) with a CC Xtreme Energy 224/230 w/ 112 ls cam and stage II ported heads. I've been running the factory tune for over a year, but I would like to work more on getting the full potential out of my current mods. I've read several tutorials, and I have the basics down.

Using Freescan, I found most all of my BLM cells to have values in the 140-150 range. I tried messing with VE tables, but it didn't seem to make much of a difference.

In the end, I changed the injector values from 24 lbs to 22 lbs to make the A/F ratio richer. Now, most of my BLM's are closer to 130, with the idle cell at 138 or so. This could mean a vacuum leak or maybe the cam is allowing enough air scavenging at idle to make the mix look lean to the PCM, when in fact it is rich?

I don't like the idea of changing the injector size, but it seems to have worked. Is there a better way?

Knock is minimal - and I know this can be reduced more by reducing the timing advance.

So, what is next? Any tips?

 

what you can do instead of changing the injector size...which i dont personally like..is to change the MAF tables. your O2 sensors are sensing too much O2 telling your PCM to add fuel. so what you need to do is calibrate your MAF tables so it doesnt read as much air coming in by scaling all the values down by 10% or so until youve reached acceptable BLMs...around 128.

 

With a cam and ported heads and a stock program I would expect to see leaner than stock conditions....the pcm is compensating for that. Ihe Injector constant is one way to tune for that(by tune I mean get closer to 128 BLM)....Adjustable Fuel pressure regulator is another.

I would also recommend a wideband dyno to see where you stand at WOT.

 

Are your o2s sensing too much air? Or are they simply sensing a lean condition that requires more fuel because of the fact that the bigger cam and ported heads are pulling more air thru the MAF. Why recalibrate the MAF so that it doesnt read the correct air flow. If the pcm doesnt see the correct air flow how can it calculate anything else correctly .Does the extra fuel you need still get added? Im not saying your wrong ....Im just trying to understand the relationships here and determine the best method to use.

 

My BLMs in Cell 15 are actually 128/128 (Left/Right), which would be used at WOT - correct? If I trust the O2 sensors to be accurate, I think I'm ok, but I'd like to hear opinions of others with more experience.

Here are the BLM cell values for over 2000 RPMs:
Cell 3: 125/133
Cell 7: 125/125
Cell 11: 126/127
Cell 15: 128/128

Cell 17: 130/139
Cell 18: 137/143

Are the Split BLM's in Cell 17 something I need to worry about?

 

it doesnt matter how big a cam is or how much the heads flow b/c the MAF should know how much air is entiring the motor reguardless, which the PCM then uses to figure how much fuel it will need to obtain the correct stoichometric A/F of 14.7:1.

yes the O2 sensors are sensing too much air, which is a lean condition...not sure where you are going with that.

the PCM doesnt see the "correct" air flow b/c the MAF is telling the PCM there is less air entiring the engine than is actually there. and the extra fuel that was being added before will still be there but you wont see it as "extra" fuel b/c your BLMs wont be above 128...understand?

in closed loop, your car will run perfect unless the BLMs are 108 or 160 which is the range the PCM will correct outside 128. all the BLMs tell you is if the computer is adding or subtracting fuel but as long as they are greater than 108 and less than 160, you wont have any problems until you go to WOT. at WOT the PCM will take the highest BLM value above 128 and lock on that....if the value is ANYTHING under 128 then it will lock on 128/128 at WOT which could cause you to run extremely rich (ie. BLMs of 108/108)