Questions about Open Loop Fuel Table (Pic)
03-21-2005, 06:47 PM
#1
Questions about Open Loop Fuel Table (Pic) About 2 weeks or so ago, I decided to play around with my new LM-1 Wideband O2. I haven't intergrated it into my EIO yet but will soon.
I wanted to do a little experiment to see how rich or lean I was with my car at Idle on a COLD START. Car runs fine with the tune I have now, not fully tweaked yet since I am waiting for VER 2.0 to come out and I want to tune with my WB02, basically I'm not in a huge hurry right now on my car. I am using Z06 timing and VE tables.
After I got the LM-1 set up, I installed it into my y-pipe where I have a 02 bung welding in.
A little info about my current mods:
- 226 222 .584 .581 116 LSA +2
- Absolute Speed STG 2 Heads
- Lid
- Jet Hot LT with no cats
- GMMG Cat Back
- Thunder Racing MAF Ends
- SVO 30lb Injectors
- Ported TB
Once I got my laptop out with the scanner and I had my LM-1 ready, I started the car. What I saw on my LM-1 Wideband was amazing, I was VERY rich on a cold start at idle, around 10-1 Air Fuel!!! As the car warmed up it started to lean out some 11-12 to 1 A/F and then all of a sudden it went to 14.7 A/F which it should since the car went into closed loop mode.
I figured I was a little rich on a cold start, but damn, not by that much. Before you even ask, yes I did adjust my VE table in the low RPMs, I think I went with "65 70 75 95" for the first 4 columns. The car starts up great on cold and hot starts, just like a stock LS1. My Ltrims are right around 0 to +5 all the time. Once I get the VE table done in SD mode, I'll work more on the Ltrims to get them in line.
I haven't started to "adjust/tune" the Open Loop fuel table yet, damn weather here in Ohio just sucks, waiting for nicer weather now.
Has anyone done this test and tuned the Open Loop table with a wideband 02 ?
Also, what do all the numbers really mean in the Open Loop Fuel Table? Do higher numbers mean a richer A/F Ratio?
On a cold start, your car is using the open loop fuel table and switches to closed loop once the pre determaned coolant temp switches it to closed loop. During open loop, you are using the MAF, MAP, IAT, & ECT sensors, correct?
I have no intentions of going MAFless but I want to tune my VE table with my wideband in SD mode once VER 2.0 comes out and the weather is nicer.
Any comments/suggestions on this subject?
Bill Wright
I wanted to do a little experiment to see how rich or lean I was with my car at Idle on a COLD START. Car runs fine with the tune I have now, not fully tweaked yet since I am waiting for VER 2.0 to come out and I want to tune with my WB02, basically I'm not in a huge hurry right now on my car. I am using Z06 timing and VE tables.
After I got the LM-1 set up, I installed it into my y-pipe where I have a 02 bung welding in.
A little info about my current mods:
- 226 222 .584 .581 116 LSA +2
- Absolute Speed STG 2 Heads
- Lid
- Jet Hot LT with no cats
- GMMG Cat Back
- Thunder Racing MAF Ends
- SVO 30lb Injectors
- Ported TB
Once I got my laptop out with the scanner and I had my LM-1 ready, I started the car. What I saw on my LM-1 Wideband was amazing, I was VERY rich on a cold start at idle, around 10-1 Air Fuel!!! As the car warmed up it started to lean out some 11-12 to 1 A/F and then all of a sudden it went to 14.7 A/F which it should since the car went into closed loop mode.
I figured I was a little rich on a cold start, but damn, not by that much. Before you even ask, yes I did adjust my VE table in the low RPMs, I think I went with "65 70 75 95" for the first 4 columns. The car starts up great on cold and hot starts, just like a stock LS1. My Ltrims are right around 0 to +5 all the time. Once I get the VE table done in SD mode, I'll work more on the Ltrims to get them in line.
I haven't started to "adjust/tune" the Open Loop fuel table yet, damn weather here in Ohio just sucks, waiting for nicer weather now.
Has anyone done this test and tuned the Open Loop table with a wideband 02 ?
Also, what do all the numbers really mean in the Open Loop Fuel Table? Do higher numbers mean a richer A/F Ratio?
On a cold start, your car is using the open loop fuel table and switches to closed loop once the pre determaned coolant temp switches it to closed loop. During open loop, you are using the MAF, MAP, IAT, & ECT sensors, correct?
I have no intentions of going MAFless but I want to tune my VE table with my wideband in SD mode once VER 2.0 comes out and the weather is nicer.
Any comments/suggestions on this subject?
Bill Wright
03-21-2005, 08:09 PM
#2
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You're supposed to burn richer on cold starts just to get the engine going and such.
The way the OLFA table works is you take stoich AFR and apply the multiplier you see as in this example:
stoich AFR/OLFA Multiplier = commanded AFR
Commanded AFR = actual AFR when your VE is tuned well
As a matter of fact, when you do SD tuning it's easiest to tune in open loop with a wideband. You do this to take away any MAF bias or trim bias (o2s) mainly to get the VE table where it needs to be. Then you reactivate closed loop and recalibrate any miscues your sensor biases to keep fueling in a good place. Keep in mind that the whole point of doing this is to command AFR and get what you're asking for. There's way too many threads about this to keep rattling on here...
The way the OLFA table works is you take stoich AFR and apply the multiplier you see as in this example:
stoich AFR/OLFA Multiplier = commanded AFR
Commanded AFR = actual AFR when your VE is tuned well
As a matter of fact, when you do SD tuning it's easiest to tune in open loop with a wideband. You do this to take away any MAF bias or trim bias (o2s) mainly to get the VE table where it needs to be. Then you reactivate closed loop and recalibrate any miscues your sensor biases to keep fueling in a good place. Keep in mind that the whole point of doing this is to command AFR and get what you're asking for. There's way too many threads about this to keep rattling on here...