Combined or Separate VE and AFR tables

[devastator]

Maybe it's just me, but I can't find a good explanation of the difference between "Use combined VE/AFR table" or "Separate VE & AFR table w/NB EGO" and "Separate VE & AFR table w/WB EGO" in the Megamanual. I've read a few posts that suggest changing from one to the other, but nothing that describes the difference between them and when you should use 1 of them compared to another. Could someone explain them to me or point the way to the proper place in the manual?

[devastator]

Ah. Thanks Lance. I wasn't looking in the MT manual. That read only slightly clarified things for me. So I guess I should just leave it at "Use combined VE/AFR table" then?

[grippo]

The bottom line of this is pw = ve/14.7 x other terms. or pw = ve/afr x other terms. In the first case you only have to tune ve and afr only comes into play if you use WB O2 control, in which case the other terms includes a WB O2 correction. In the second case, you can tune both ve and afr and you can still use WB O2 control. In theory the second form is more correct because VE is inherent in the engine and wouldn't change very much if you switched fuel (unless unburned residual gas was very different). AFR however could change sigmnificantly. But you would know what the change was from ther chemistry and would only have to change the afr table. It is more convenient for people who have a dyno that can independently come up with the VE values. Then they just put in the afrs that give them what they want where they want - generally good economy at cruise and power at wot. For the average person, the second method is difficult because he doesn't have a way of measuring VE independently. So it's easier to just tune the one ve table. But when the car is tuned, you end up with the same PW. Pw x 6 is the same as PW x12/2.

[devastator]

That makes sense to me now. I didn't think that the combined method would work for me, even on a dyno, because I'm running E85. But now I think it would work just fine, since I've programmed my LM-1 to output 1 Lambda as 14.7:1, instead of the actual AFR for E85. So far, this has made tuning much easier, but I'm investigating logging some dyno time in the future.
Thanks guys.