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?

 

The PE table is triggered by throttle position as you know.
The PCM will choose the richer setting between the OLFA table and PE.

I set the high map portions of the OFLA to an EQ of 1.
Then set the PE table to the EQ ratio of your choice.

I like to set the PE table to a convenient value across the board. A safe value like 12.5:1 AFR.

Then tune the VE as you described. Sort of sneak up on the AF vs RPM at WOT. Gradually increasing rpm after each tuning drive.

When you have commanded and measured matching, you can then go back and create a fuel curve in the PE table.


Ron

 

Okay. I've read that before that 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 whenever I'm coasting, it'll lean back out to the values in the OLFA table (which is what I want).

Here is my current tune, btw. I used a VE table from a similar cammed/heads/FAST102 setup as I figured it would be a good starting point rather than using the stock tune increased by 15% across the board as the VE is different for high overlap cams where they are basically in the toilet at idle and at part throttle.

 

Looks fine.
I don't think anyone can look at a VE table and tell you if the values are correct for a modded engine.
And you are correct about the idle and slow speed areas. In fact, with your mods, the whole table will need attention.
Get used to living with the lap top in the car!


Ron

 

Already there! lol

 

Ha!
You are picking this up pretty fast.
Ron

 

I still have a lot of questions. But I just got the software end of last week. It's not as hard as I imagined. But some things I have had a hard time understanding, i.e., why the PCM does something vs something else. GM built failsafes in and the overlap can be a bit confusing.

 

Good advice so far. I set my PE to 12.8 across the board absent of dyno and track tuning. I see your PE enable KPA is 10 , which in my opinion is kind-of low. I like it to be well above anything I would see in part-throttle driving. Mine is at 60 kpa, about 5 kpa higher than idle. I also run my enrichment ramp at 3 to avoid a lean spot when PE enables, especially because of my higher PE enable KPA, and I notice yours is at 1. I'm surprised how close your VE table is to mine...but of course, this means very little as every combo is different!

To the root of your question, are you looking to create a lean-cruise? Right now my OLFA is set to 1 across the board and .9 between 25 and 40 kpa at 140 degrees to 212. I also increased timing to 44 or 45 degrees in the matching rpm/cylinder airmass section of the main spark table. I used a modified C5 Zo6 table. This gives me 16.4 afr at cruise without surging or bucking. It looks like this:



I do plan on taking a day to change all the 1s in the lower temp ranges to something else because it does run a touch lean while warming up. I have a custom histogram set up for that. It logs AFR error against MAP and ECT. That allows you to figure out what to compensate by with your OLFA during warm-up. The trick is, you can only really do this once since changing the OLFA and charting AFR error during warm-up will make you constantly chase a moving target! I'm actually reluctant to try it. Yours appear to be pretty stock right now under 140 degree temp, and that's ok.

Are you really running 28 degrees advance at idle?

 

Yeah, and part of the tuning, especially when going OLSD, is the elimination and zeroing-out of many 'features' no longer required or cared about. I think most people have a goal of simplifying their tune to achieve the exact results desired.

 

28 degrees. It likes it there. Timing of 22-24 gives me a kPa of 75 and at 28 it's 70. Tho the adaptive spark will sometimes add 12-14 degrees (which I've tuned down a bit) and that will sometimes kill idle if it jumps over 42 degrees. It advances the flame front so much it quells the spark. I was using basically the base tables, but need a little less aggressive spark control.

As for the kPa adjustments on the PE mode... that's an interesting call. I know others have complained about lag and enabling it sooner helps with that. I'll play with it tho since I don't need PE engaged at part throttle. I've also changed my TPS now. In the 1600-2800 range, I'm going to command about 38% TPS. If I keep the kPa low, then throttle will determine when PE is engaged. And it doesn't need to be in the slip range of the converter. I'm not putting a huge load on the motor. Once I get up over 3200 the slip becomes less and 27% might be enough to engage WOT. I'll play with it based on how I drive and what the log shows.

I changed the table as follows as the new baseline:

64.0 64.0 64.0 64.0 38.4 38.4 38.4 38.4 27.0 22.0 17.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0

 

Jake, are you running CL, or OL always...?

Some comments/observations:

OL: PCM selects richest of active tables (i.e. when PE enables, PCM selects richest of PE or OLFA).
CL: OLFA is not active when you go WOT (going from CL to WOT does not enable OL), so PE table is the only one active.

Unless you have dyno access to "shape" the PE curve for TQ and HP, then do as Ron said set PE EQR to safe value straight across.

Active tables: watch out for other tables/modes that may come active, since PCM selects from richest of the active ones (e.g. EPM, PPM, COTP).

 

OL for now since I have a wideband in the car. Eventually, I may turn on CL and enable the narrowband O2s - I'll cross that bridge when I come to it. But for tuning, it's def OL for now.

And that's what worries me. There are so many tables. I'm trying to understand when or why they may be active.

And I'll go ahead and set the PE for 12.5:1 across the board. Should be good with E10.

 

The good thing is that whatever table is selected (its cell being the richest of the active tables), the fuel it commands shows up in the pids AFR and EQIVRATIO... so tuning VE and MAF boils down to comparing wideband to these pids.

There is a parameter for setting the stoich AFR... E10's stoich AFR is 14.2... if you can set this, and if you can work with EQR (rather than AFR), then PE set to EQR 1.165-1.175 is correct regardless of stoich AFR.

i.e. EQR 1.165 gives AFR 12.61 based on E00 (stoich 14.7), and AFR 12.19 based on E10 (stoich 14.2).

 

Thanks, Joe. I hadn't changed that yet, but had looked at it. Everything here is E10 on the pump. So I'll make that change.