19doug90

Why in the world in my stock tune does pe vs rpm go -15 at 3200 rpms, above and below that are also negative then at higher rpms its the 14-16 that id expect

why the heck would gm put my motor at 16:1 at 3200 rpms...going right into peak power area.

i basically just copy and pasted my open loop afr vs map table into the pe vs rpm one because thats how i think it should be

trying to understand why the stock tune was like this tho

Section162

If you're using the stock ecm (730/$8D) then this table doesn't work the way you think it does. AFR's do not go in this table. The ecm uses both the PE vs. RPM and PE vs. Coolant tables to calculate the AFR with a (complicated) formula. I would do some searches and look in the stickies for the AFR Tuner program.

19doug90

the actual table for 8d is enrich power change to AFR vs rpm. So that is the % change in target afr when in PE.

Yes the coolant table also plays a role, but at temp its going to run off the rpm table mainly.

Which means at 3200 rpms, in pe (stock set above 50% tps) its shooting for around 16:1

EDIT: okay so i didnt look at the coolant version of the table, at temp it asks for a 22% change in afr, which puts you at im going to guess around 12.3

the stickies dont have a lot of info on this, i really dont understand what happens when one table is telling the computer to make a positive in change in afr by 20+% and a contradicting table is telling it to make a -15% change at the same time

gta324

I tune WOT with the engine at working temp first via the AFR vs RPM tabel, see it just as a adjustment +/- to get the correct AFR. Then you can adjust the AFR vs temp if you like to tune @ WOT at diffrent engine temps.

In most cases there are many tables/constant involved in BPW/SA calculations and you can change one or another and you will still get the same results in the end.

/N.

Section162

No - that's not correct. It sounds like you're putting meanings into the tables that may or may not be there, based on what the label says. In this case, it might be helpful to know exactly how the ecm is doing its number-crunching.

gta is correct, at the end of the day everyone has their own method that works for them. And you're right, I don't think the stickies have much info on this, so you'll have to do more searches, or I might be able to post some info later today.

RBob

iTrader: (1)

Check this entry from the Tuning Guide Book sticky:

P730: BPW and Target AFR, how it is used and calculated at WOT in PE Mode (P730: Target AFR and how it is used in PE Mode)

Traxion moderated this group for quite a while.

RBob.

19doug90

how am i misinterpreting "enrich power change to AFR vs rpm". That to me means the change to target afr, at given rpms in the table, when in PE

the issue is at 3200 rpm it has a -15% change, where as the pe % adjustment when above 30 celcius is 22%, they contradict.

Thanks rbob ill check that out