AFR Changes and Open Loop Multiplier Table
#1
AFR Changes and Open Loop Multiplier Table
I have been messing around and noticed that when you change back to the stock OL AFR Table, your air fuel ratio doesn't correspond like it should. ie. When you command a AFR of 12.96 (1.13) and get the cells to match, then switch back to the stock table (1.08-1.13) they are off.... I was under the impression that once you get the VE table dialed in to 12.96 (1.13) and set the table back to stock, all will fall in line. Why don't they?? I see this problem a bunch at idle. I had it set to 12.96 and now it is set to 14.7, but the AFR still shows 12.96 so my AFR % is off.
#6
Kleeborp the Moderator™
iTrader: (11)
Damn it Chad...I'm putting on an 85mm truck MAF this weekend, and was just going to get a good SD tune on it until I can figure out what to do with the MAF table (as in I'd want to have HPT 2.0 with custom histograms).
You suck. Get this figured out. Can you verify you are in closed loop?
You suck. Get this figured out. Can you verify you are in closed loop?
#7
I am in open loop as my car will never see closed again. The MAF table has nothing to do whth this as it is back to back tunes, just changing the open loop afr table multiplier. I still think it has to do with the air coming into the car and a calculation the PCM uses. My only recommendation is to set the open loop table where you want it and adjust accordingly. If you are using a wideband and setting the ve up with open loop, I would scale the VE table by a factor of 1.00(14.63) up to 70 kPa and 1.13(12.96) from 75kPa to 105kPa. This ensures you see a commanded afr of 14.63 at cruise and part throttle, but is still safe at 12.96 when you go WOT to tune.
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#8
Kleeborp the Moderator™
iTrader: (11)
Hmmmmmmmm...I guess I'm gonna try doing something a bit different from you then. I'm gonna try a closed loop SD tune (verify VE in open loop, close the loop and let it trim as needed, leave MAF fail freq. set at 0). My O2s seem to be doing alright for the time being...
#9
Kleeborp the Moderator™
iTrader: (11)
I would also wonder what else the PCM looks at in addition to the Open Loop A/F table...have you tried setting the whole table to something like 13.5 (not just sections) to see if it gives you that? Maybe it interpolates kinda like the VE table with more than one value?
#11
Originally Posted by MeentSS02
Hmmmmmmmm...I guess I'm gonna try doing something a bit different from you then. I'm gonna try a closed loop SD tune (verify VE in open loop, close the loop and let it trim as needed, leave MAF fail freq. set at 0). My O2s seem to be doing alright for the time being...
#12
Originally Posted by MeentSS02
I would also wonder what else the PCM looks at in addition to the Open Loop A/F table...have you tried setting the whole table to something like 13.5 (not just sections) to see if it gives you that? Maybe it interpolates kinda like the VE table with more than one value?
#13
Originally Posted by WS6FirebirdTA00
are there any other hidden tables that would change it for conditions? like the ect correction and iat that we talked about?
#16
Kleeborp the Moderator™
iTrader: (11)
Hmmmmmmmmmm...something is not right here. If you are commanding an AFR, you should be getting that AFR. Something is adding in to this equation somewhere...I'm sure it isn't your trims (that's too elementary to have slipped past you). Grrrrrr...let me think about this.
#17
Originally Posted by MeentSS02
I understand where you are coming from, and in theory, you are right. I just think there is more to this story than that...I really need my software here to make any more guesses.
#18
TECH Senior Member
iTrader: (33)
that sounds like a legit reason, so the comanded afr stays the same then? have you tried to change the ve in those spots and try to see waht it changes? i would think whatever you set it at it should hover right around there reguardless the ve settings, but it may mix it up. id like to see if the ve was decreased the same amount what woudl happen.
#19
Kleeborp the Moderator™
iTrader: (11)
Hmmmmmmmmmm...something is not right here. If you are commanding an AFR, you should be getting that AFR. Something is adding in to this equation somewhere...I'm sure it isn't your trims (that's too elementary to have slipped past you). Grrrrrr...let me think about this.
#20
Kleeborp the Moderator™
iTrader: (11)
Originally Posted by Black02SS
When you are in open loop, you work off of the Open loop multiplier Table whatever that value may be. If you tune off of closed loop (oxygen sensors) you don't use that table, you tune off of stoich (14.63). So why would you tune in open loop for a commanded afr of 12.96(1.13) if you are going turn right around and throw it in closed loop with a commanded afr of 14.63? Why not just tune the open loop afr table too 14.63 to start so there isn't this issue. Granted, it doesn't really explain anything but just makes more sense to tune the car for the desired AFR the first time then the other?
So, here's what I'll do:
1. Disable the MAF (fail freq -> 0), disable DFCO, disable PE.
2. Get the VE table dialed in to an Open Loop F/A of 1.13
3. Once it is dialed in with the wideband, I'll re-enable closed loop, but still in speed density (MAF fail still @ 0). Re-enable PE and maybe DFCO (depending on my mood).
4. Once I find a decent method for tuning the MAF, I'll get that back in line.