I am off to a fresh start using the AUJP bin because I am running iron heads (versus AHNT and aluminum heads). After tweaking my FP and running all the normal checks, I ran some idle runs in park with the scanner. All my BLM values were between 108 and 114. So I am rich--that part is obvious. Inj pulsewidth hovered between 1.6-1.8. FP with vac line connected was 32 PSI, with no leakdown after testing.

Using the formula of ((Current BLM/128)*(current VE in cell)) which approximates the needed VE value, all of my lower table will be at least 10-15% lower than what was prog'd from the factory.

I can understand this up to a certain point...a more radical cam grind will sacrifice lower VE for increased upper VE. I expected to be rich at low RPMs, but not this rich. Like I said, FP is 32 at idle with vac. connected and pulse width doesn't seem too excessive.

I think I am starting to depress myself on how bad my camshaft/heads/induction combo really is. If my fuel delivery is not excessive, which it doesn't appear to be, is this really what I am finding out? The stock VE table can be seen here



and the suggested modification with my spreadsheet analyzing 5000 frames of BLM vs MAP vs RPM (using only values that had been obtained from BLMs after they had stabilized) can be seen here.



Notice how much of a drop I would need to make to my VE table. Of course, there are not enough data points running at idle to smooth out the entire table, but I hesitate to drive it and come up to a stoplight with it bottoming out the BLMs. It appears that in all reality, I should scale down my entire table by 12%. I realize I can not base my tuning on one run, but this is a ballpark of where this tuning session led.

Since the ECM uses MAP, VE, EGR, Intake temp, and engine constants into consideration when calculating air intake, and considering all of those sensors are correct, it looks like VE is the only thing that is causing this table to be all lower than I would want it to be.

I also ran the engine combination on Desktop Dyno and this is what also makes me think the offset is needed. None of the calculated VE values by the software were above 82%. I noticed that in the AUJP and AHNT that GM is using values close to 93% for max VE at WOT.

Advice, comments, suggestions? I am trying to forget about the actual revisions first and just trying to understand what the scanner is showing me. I think I already have some to the conclusion that my combination is an inefficient air pump. With that being said, does my above logic make sense about scaling the entire table?

Whew, that was a long one. If you made it this far, thanks! -Matt-


[Modified by HighHopes85, 4:11 PM 12/20/2001]

 

Sorry if this sounds stupid, but ...

why do you want your new table so ... rough?

and why is there a peak in the middle of it?

 

Actually, I am not crazy enough to put a table that is that rough into the BIN.

The reason that table is so rough is that I only had data in those regions that were lowered. In other words, if I went for a spin with the scanner hooked up, I would have had data in more MAP vs RPM ranges and more of those data points would have changed. The data was limited to being in park and drive with my foot on the brake. So the table titled 'New VE Table' is just to show me what changes would be suggested for the RPM and MAP conditions that I encountered. Make sense?

I just got a pretty good lead on this though. I am rethinking (scary I know) my process of why my readings are like they are. I *think* I understand what is going on, but don't want to post it because I could be way off in left field. -Matt-

 

can you have a passenger take the data reading wheile driving?

I did that with mikey going down a drag strip! :D

Down in Dallas we tuned the Ferraris by holding the engine at a given rpm.
50mph first in one gear then another, etc.
to get the various throttle responces.

of course nothing beats a dyno!

 

I have looked at GM VE tables and compared them to desktop dyno. The actual numbers in the stock VE table are nothing like what I was expecting.

Brian is right, you need to take snap shots of various points and use those to start the new table. Then smooth in the areas between the points. Then go back and take new snap shots of the points near the old ones and see how the previous values worked and fill adjust as needed.