Now that my LS Hombre is on the road, I'm going back through the first of two Greg Banish books I have regarding tuning. So far, I've been logging my 02 Camaro and 00 Hombre focusing on the VE tables. Recently I decided I need to work on my fuel system on my Camaro because I think I'm seeing symptoms of restrictive fuel lines... but that's another discussion...

I need some guidance working on my VE table. Among several other issues, perhaps the most glaring one to me is that I've been targeting 14.7 throughout the table to this point. This is because I was told we can get the heavy throttle cells enriched with PE. Well yesterday, I'm reading through the book and I decide to poke around the editor to put the knowledge to work. Then it hits, I discover that I've been aiming at 14.7 AND PE IS ACTIVE! PE is set at around 1.14/1.15 for what I assume was a target of 12.8 by the previous tuner. Sure enough, PE is active above 15kPa and 0 torque at throttle positions above 64-28 from 800-8000RPM.

So correct me if I'm wrong, but doesn't that mean that I've been targeting 14.7 WITH enrichment? And if for some reason I find myself in a different DA, I could potentially hit a cell where it was tuned with PE in mind, but PE doesn't kick in (due to denser air or whatever) and I can spike lean?

Now I'm reeling... thinking this whole time I've been approaching VE table development wrong. Should I turn off PE (set to 105kPa) and develop a VE table at 14.7, then go back and activate? Or should I continue on this current method, which I'm thinking could potentially be catastrophic if I travel to a different area with a much different DA?

Sorry for the essay, but I guess my overall question is, what should I be targeting for my VE table development without PE? And if it's 14.7, how do I safely get to the upper RPM and MAP to target 14.7 without PE? Thanks in advance!

 

Are you going to keep it in SD mode when done? If not them just tune the VE until the point where it is going to use the MAF 100% Set PE Enable parameters so it doesn't enable for tuning low load areas them re enable it when done. Turn off DFCO too. If using a wide band then run it in open loop. If using fuel trims then keep closed loop enabled. Make sure MAF is failed. That's about it.

 

When PE kicks in, commanded AFR shows this, and since PE kicking in would occur on throttle transient, as long as you filter out throttle transients you will be ok (i.e. VE is regardless of commanded AFR).

(i.e. you want to filter out transitions to/from PE which occur when the TPS enable curve is crossed, i.e. on throttle transitions, which you want to filter out anyway).

If you're intending to run SD only then you have to be careful to be suitably rich at significant load, i.e. let PE kick in, or ramp up the OLFA table (but doing this makes it harder to filter out any gradual transitions).

Otherwise if you're intending to run VE+MAF then do what 2xLS1 said (but if your MAF ever failed then you don't have a tuned upper VE to fallover on; but it probably won't fail).

 

It sounds like you are wanting to tune your VE tables in the upper RPM range and upper load range to target 14.7 so that your PE is enriching it to 12.8 at WOT?

I tuned my VE tables below 3600rpm and then used PE for everything above that. I made slight adjustments to VE above 3500 so that my AFR went from 12.4 at peak torque to 12.8 at peak horsepower.

You aren't going to get to the upper RPM range without PE safely. Generally above 4k rpm your going to be at WOT, and you don't want to be at 14.7. You can set your scanner up to log commanded vs actual AFR (your PCM will show the commanded AFR that includes PE) and try to tune your VE tables and MAF table by using % error. The bad thing is that you're in each cell for such a short period of time, that getting a good average is difficult.

Generally I just scan WOT throttle runs and adjust my PE tables accordingly to get my desired AFR at WOT versus trying to tune my upper load and rpm portions of the VE table.


I hope that all made sense.....

 

Guys, thanks for the feedback. Looks like I was definitely missing some critical parts of the process, hopefully I haven't done any serious damage.

On the Camaro I intend on keeping it SD. I tried a 100mm MAF and had success, but when problems arose, it was always at the MAF. That said, my Hombre has the stock ported MAF from my '00 B4C and a SaxonPC screen. I feel MAF is around the corner for the truck. So you're saying to set the PE so it's out of the way of my low load tuning, I believe it is but I'm bumping up against that threshold now. And I am in open loop, MAF failed so sounds like at least most of my efforts were in the right direction.

So let PE kick in, just filter it out... I hadn't thought about filtering out transient conditions, how would I go about doing that in HPT? I have a cell on my truck that I was suspecting was resulting from clutch in transient conditions, it's down around 35 right now and the surrounding cells are in the 50-60 range... I'd love to get those cells straightened out! So how do I go about filtering out transient conditions, and how do I filter out PE enrichment when adjusting tables?

That's right, aiming for 12.4 to 12.8 but want to tune for the VE table to represent 14.7 across the board. But it sounds like you use the PE strictly on RPM rather than RPM and MAP?

As it is today with TPS involved, it seems like if I drew the transition range from non-PE to PE on the VE table, I would see a band of cells in a diagonal upward to the top right.

I think I detected an interesting point there at the end... commanded vs actual. Commanded is adjusted with PE, right? So if I start tuning against commanded AFR (as long as that incorporates PE), I can basically add my PE and safely get to the upper range, going along around 12.6 or so, right? Then I can adjust the VE using a lambda and my PE will remain constant?

I think I see the light at the end of the tunnel!

 

Ways you can accomplish it:

Set your PE EQ ratio to 1 across the board. This prevents you from getting any PE enrichment while tuning VE tables.

Set your PE enable Hot/Cold tables to a TPS % that you know you won't cross while tuning your VE tables.

Just keep your foot out of it while tuning your VE tables.

I personally use long term and short term fuel trims to dial in my VE table for closed loop operation. If your keeping your tune a closed loop tune, the O2 sensors are going to determine your fueling anyways, not your wideband. I like to see all my fuel trims a little negative, because I've have read that positive fuel trims will be added to WOT operation (have not been able to verify this in scans).

Once the part throttle area of the VE table is good (below 3600 rpm for me in an automatic) I do the rest with PE and some VE tuning.

There are different ways of doing it, but that's what works for me. Your end goal is correct fueling and there's more then one way to get there.

I will say I personally prefer running Hptuners 1 bar SD OS. Tuning is easier and having the restriction of the MAF gone picked up some speed for me at the track.

 

Here is the table that is mainly responsible for putting you into PE mode. It is a function of TPS% and RPM.

Example: if you are cruising at 2k rpm it would take a TPS% above 64% to enable PE.

 

And once you are in PE mode this table determines how much additional fuel over targeted AFR is going to be.

Example: 14.68 AFR / 1.15 multiplier = 12.77 AFR

Now here is the rub some people have. If your VE table is off your commanded AFR is not going to match your actual AFR. You don't have the fuel trims adjusting your fuel to 14.68 at WOT because your now in open loop operation. So your options are:

Tune your VE/MAF tables in the WOT/Openloop regions to be correct so that your PE enrichment is spot on and your commanded AFR and actual AFR match, or to adjust your PE tables to give you a good actual AFR when in those regions.

I use the latter method because holding my engine in those high RPM high load regions long enough to get a stable average is scary to me.

 

Those are the tables I saw that scared me into stopping the tuning and coming to the forum. My values are identical to what you posted, too. It appears all I need to do to get my Camaro into the right neighborhood is tune using percent error for lambda rather than my current method of aiming at 14.7 with my VE adjustments. And for my Hombre, I'm probably close enough to throw it in closed loop and use the fuel trims to get it right.

I'm sure I'll have more questions... but for now, I feel good about my next steps.

Joecar, I would still like to know about filtering out transient data if you could shed some light on that.

 

Filter out just the transition into or outof PE (which happens to occur on throttle transient)... I'm not sure how to do it in HPT.

 

Ok, keep these things in mind while tuning:

VE is the cylinder fill airmass, regardless of fueling.

Fueling is the desired proportion of fuel to air, regardless of VE.

i.e. fueling is on top of VE, and orthogonal to it.

Fueling is determined by the OLFA table in OL, and by the PE table in PE (and when multiple tables are simulaneously active, the PCM selects the richest at the current operating point).

The commanded/desired AFR pid shows PE when PE is active (i.e. it shows the commanded fueling of whatever fueling mode is active).

 

In EFILive you can set a filter to filter out data frames where TP is moving more than say 5% in 0.2 seconds... I haven't fully played with HPT, but I know it has a similar feature.

 

You're not aiming for AFR 14.7, but rather you're aiming for the commanded AFR (from whichever active fueling mode is producing it)...

i.e. you're aiming to adjust VE such that measured AFR is same as commanded AFR, regardless of what value that AFR has.

 

I hate to admit this, but indeed, that was the fundamental problem. PE was activated at times, but I was tuning EVERY cell to 14.7. Oh it hurts to think of what I did... if you can believe it, I got some knock on the way to school yesterday. Looking through the log, I got 1.4 kr... at 1660RPM, 14.4 AFR, 26% TPS and 91kPa! I was at 71MPH at the time, and I was just giving it a little in 6th gear to get past a slow vehicle. Oof.

So when I figured out the issue, I looked at my next histogram and found the error table. That cell? 1.15 off. Indeed, the entire curve showed fuel to add above around 60kPa.

Now, I'm still not happy with this scenario. Ideally, I'd like PE to activate when I need it, not at the arbitrary settings I have where I would just make up for error in the VE table. As you can see, I can get some really good manifold pressure with minimal throttle with this 102LSXRT and 102TB in south MS. Seems like my PE should enter earlier. How do I determine where it should be?

Also, I found a filter cell on the histograms that looks like it needs some form of a code string to filter out transient data. Still have to figure that out...