Tuning in OLSD - PE and OL EQ Ratio Values Question

[JakeFusion]

So, I understand the need to adjust the VE table to achieve the desired A/F ratio, but where do you set your desired A/F? Is it in the PE table? Or the OL EQ Ratio Table?

The reason I ask is I know the OL EQ Ratio is what the PCM uses in Open Loop Speed Density (which I'm in). And you can set your ratio by kPA by temp. So it would seem that I would want a value of 1 at kPa values less than 65 or so for ~14.7:1 cruising. And perhaps something like 1.14 in the upper kPa ranges to fatten it up in WOT or high-RPM situations.

However, I know the PE table is used at WOT to enrichen or lean out the base fuel map (which I assume is the OL EQ Ratio map).

So it seems like the best course of action is to set the OL EQ Ratio table to 1 everywhere and then set your PE to 1 at idle (for no enrichment); 1.14 before peak torque, 1.17 at peak torque, and 1.14 the rest of the range when using E10 fuel.

Then when I tune in VE and setup the histogram to tell me how far off I am in A/F, it's not trying to tell me how far off I am from 14.7 (which is the OL EQ Ratio), but how far off I am from my commanded A/F of 1.14 set in the PE table (which is a fuel adder to the OL EQ table). I would assume this is a good approach to use to tune my VE with my wideband showing % difference in the A/F ratio.

And some people enrichen the cold temps of the OL EQ table for safety reasons I would assume so that you don't run too lean? Because your VE is based on RPM and kPA readings and the OL EQ table provides the temperature input.

Right now, I have an 04 Sierra as my base OL EQ Ratio as I've heard it has the best map for the OL EQ. And at 176+ degrees everything is set to 1 (per Speed Density Tuning by William Hoff in the tutorial section), but the mix is richer as the ECT becomes colder.

Is my understanding of how those tables work correct? Will using the 04 Sierra Table with the above PE values provide me with the correct inputs for percentage change using the Wideband for VE tuning?

[CatnipG5Bandit]

I looked at your tune in another thread. You have power enrichment TPS set to 0% in the Cold table. That is likely why it is referencing your PE commanded AFR at idle instead of your open loop EQ table. Set the 0-1200rpm tables to a higher value. Also in your open loop table it is better to set the EQ higher at cold temps because otherwise the vehicle would tend to stall in the cold. The engine is not hot and fuel hitting the walls cannot evaporate so the computer has to compensate by adding fuel in those extreme areas. An EQ of 1.0 at 20*F will likely not start at all, and in my experience even 1.0 as high as 100*F ECT will cause the car to stumble on cold startup

[JakeFusion]

Okay. So my understanding is right.

Yeah, I set those to 0 for some reason on something I saw. But I'll return those to stock.

[POWERZONE]

You are gonna have to post your tune and logs so we can see what you have done.

I can tell you this general info, there are certain conditions that must be met besides just WOT before the PCM/ECM changes its commanded air fuel ratio. Example, I can change the RPM, TPS vs RPM, enrichment rate, KPA, etc... and affect when the AFR commanded changes. You don't have to go WOT before PE kicks in. It can happen before.

If it is true that your AFR error is reading your AFR commanded in PE , then you must have changed something or set the tables in such a way that this is occuring. But the only way we will know is if you post your file.

[CatnipG5Bandit]

Okay. So my understanding is right.

Yeah, I set those to 0 for some reason on something I saw. But I'll return those to stock.

Someone set his entire PE table to 0 and then input the EQ ratio he wanted based on rpm. Maybe that was it? I'd never do that personally when you could simply take the time to understand the ECM in general.

[POWERZONE]

Someone set his entire PE table to 0 and then input the EQ ratio he wanted based on rpm. Maybe that was it? I'd never do that personally when you could simply take the time to understand the ECM in general.

Ok, I just saw it.

Interesting.

I figured something had to have been changed for it to do that.

[CatnipG5Bandit]

Yeah, I think the post where the guy did that was in the fuel economy thread from years ago.

[JakeFusion]

Current tune file. I haven't logged it yet driving around. Getting the wideband today. Hence the reason for my question - wanted to make sure it was setup so I could log effectively. The VE table in here is one from another car that was very similar to mine. I figured it would be a good base to tune from vs the stock VE with 15% added to it.

[CatnipG5Bandit]

You can log your maf and VE effectively even with your previous setup commanding 1.14EQ. The airflow error uses commanded EQ to calculate error. Say your error % is 5% for example. If the commanded EQ is 1.14 or 1.0, the error would still be 5% off. Otherwise WOT MAF/VE tuning would be useless because it would be giving you the error vs 1.0 EQ all the time and you'd never get accurate airflow. The most important thing about logging is to take it easy and be safe. Especially with timing in some cars.

[JakeFusion]

My understanding is the PCM will choose the richer setting between the OLFA table and PE. So, it looks like I'm on the right track then to tune this with the wideband and adjust the VE table. And whenever I'm coasting, it'll lean back out to the values in the OLFA table (which is what I want ~ 14.7:1).