I was just having another look at your modifications ... and they don't look very drastic to me. Nothing that the stock computer shouldn't be able to compensate for.

So ... a vacuum leak ... would admit unmetered air into the system ... which would make things leaner ... then the 02s would get out of whack ... then the computer would add some fuel ... just like you first suggested ...

Well, you could take it to a dealer and they will check it for the infamous manifold leak ... they may even do it for free if they think you will give them the work.


Any way ... GL

LWM

 

Wilson, LWM, JGeorger:

You guy have really helped me!

I did as I said I would and put the VE tables back to stock. Then I went and modded my MAF's to read more AFGS. Well that was wrong as I went to 108 on my BLM's in a matter of seconds. So I went the other way and subtracted from my MAF tables.

Turns out the magic modifier was 13% decrease in my MAF tables up to 15 AFGS after that, I graduated the decrease until I reached 0% around 70 AFGS.

I am at 124-129 in all my BLM's now.

I cannot thank you all enough for giving me ideas to go on and try!

One final question: Now that I have my MAF tables correct, should I now unplug my MAF and calibrate my VE tables in SD mode? Is it necessary?

Ben

 

Congrats on getting your BLM's squared off.

As for tuning in SD mode, it would probably be a good ideal cause no one is 100% sure that VE tables arent used in MAF mode. Its probably going to take a few VEMaster runs to get everything squared off. Good luck!

 

If he had to change the MAF readings, doesn't that mean air is getting into the system somewhere else?

I've got the same problem right now (change VE and BLM doesn't move), except I've got a CC305 + stock heads in my car.

Run VEMaster and get it makes X changes, Upload the new version and log another run. It gets the exact same (within 1) O2 Averages. And makes suggestions to lower the VE tables again.

Anyone running a CC305 or Hotcam + stock heads with 128ish BLM's wanna share their LT1Edit File so I can take a look?

 

Not necessarily. You see, the maf can only measure air moving thru the engine, not the air actually being used for combustion. This is particularly evident when you go to a bigger cam, which invariably has more overlap than the stock cam. In this case, both the intake and exhaust valves are open at the same time, and some of the incoming air/fuel mixture goes right out the exhaust. Some have said that the VE tables are used as a correction to the maf. Others maintain that the VE tables are only used when the maf-based fueling is outside some range and the pcm stops trusting it. I have a similar cam to yours (218/230-114) and my blm's were actually quite close to 128. I did try running vemaster a couple of times, but the results were statistically insignificant. Hell, I'm not even sure anymore what the point is trying to get the blm's to 128. Obviously, if you see very high or low blm's that is indicative of a mechanical problem. Also, I don't think the pcm is very good at fueling when it comes to radical cams with lots of overlap. There seems to be a point after which the O2 feedback loop causes more trouble than it's worth.

I should also ask the question: Ben - how does your car run now compared to before? I still don't like the fact you were hitting 108 blm's on a stock cam.

 

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I should also ask the question: Ben - how does your car run now compared to before? I still don't like the fact you were hitting 108 blm's on a stock cam.
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Jgeorger,

My car is running extremely smooth (but it ran almost as well before just ran rich). Just by changing my MAF tables the bit as I did in the lower end, all my BLM's are inbetween 122 and 129.

BTW, I did unplug my maf and try SD tuning. OMG, my car ran so lean (like all BLM's above 140) that it was not worth trying to modify my VE tables - my assessment anyway. VEMaster had me with my lowest VE around mid 50's after one iteration. I concluded since it was running so well anyway that the VE tables are making no difference hence I did not change my VE tables at all.