I figured out a way to systematically lean out the fuel table. This is probably useless for advanced tuners, but it might help beginners (like myself). I started by entering my stock high-octane fuel map into excel, then I used a formula to calculate the new values.

=14.7*(X/14.7)^0.8

where X is the cell from the original map. This effectively "curves" the values similar to the way a teacher may curve grades to help the slackers. The richer the factory setting, the more it will lean it out. The stoichiometric cells (14.7) are unaffected. I used 0.8 as a starting point for my "curve factor." At most, it leans out values by a full point. With this method, it's possible to systematically adjust the whole table with just one parameter. It's a pain to manually type in all the values, but at least it's better than blindly trying to make the table smooth one cell at a time.

Here's my excel file: fuelcurving.xls

Note: If you have an VIII, you will have to change the load axis since VIIIs only go up to 260.

I'm going to log some highway pulls tomorrow night with the new map to make sure I'm not getting any knock. If I don't see any knock, I might lean it out some more by lowering the curve factor.

 

good post.

 

Interesting stuff..:-d

 

An interesting concept. However, I don't think it would be wise to apply that formula to the entire fuel table. I suspect that some cars will not take well to that kind of leaning out in the (3000,100) to (4000,160) range.

l8r)

 

I agree with Ludi,

My own experience has shown that you tend to lean out the upper rev ranges and possibly richen up the midrange / spool up area, so applying an adjustment like that across the board would only work for something like scaling or bulk adjustment of afr's once you establish the proper curve.

Good Idea, just be carefull, and log your afr's with a good wideband.

 

This formula isn't really going to give you the results you expect, for the very rich areas it'll help, but the midrange and lower load portion of the maps it will result in being a little too lean, ESPECIALLY if your running higher than stock boost or have aftermarket intakes and whatnot (which already cause it to run leaner than stock)

 

is there any way to just apply the forumla to the top end?

 

Good idea in principle, and you may see some results. One thing to keep in mine however is that the stock map is not very smooth or consistent.

 

would be a great way to establish a better then stock tune or a low octane fuel map

 

Also, it might be better to adjust using 11 or 11.5 as the base value ... =11*(X/11)^0.8. We aren't tuning for 14.7 where most changes are being made. Good idea though ... I like it.

EDIT :: Okay, I see what you are doing now ... the change I mentioned would only work if you applied the change only to the boost area of the map.