Leans way out at idle, way rich on throttle, VE table looks rediculous

[ninjai_ruken]

Catalyst and/or post-O2 tests are trying to run over and over, because you have no cats and have, I assume from looking at the file, totally removed the rear O2s. These tests can't be disabled in the Gen3 PCM. When it can't get a result from the test it keeps trying again and again anytime the conditions are met (one test runs at idle, other test runs while driving in a window of certain conditions).

If the tests are able to run and fail, they will stay failed and it will stop running the tests until it thinks the problem has been repaired (or codes cleared - even though it does not set codes when P0420/P0430 are disabled).

The solution is to plug some rear O2s back in, something most people really do not like to hear because they already chopped all that wiring out of their super-slick custom reworked harness and threw it away.

You can't tune around this. As you found if you try to make it richer while it's intentionally commanding it lean for the tests, it's too rich when the tests stop. And you can't force it to not run those tests other than by letting it run them and then fail, and it can't do that if there are no rear O2s plugged in.

Description of how this all works doesn't exist in the service manual since these tests do not have their own DTCs and aren't part of the other cat/rear O2 codes that have been disabled. But from the description for P0420/P0430:

I bet this is the issue I am having, I thought maybe it had to do with a temperature multiplier somewhere because some days AF would be spot on. And on other days it would be off and my symptoms although not identical are pretty close to the Original Posters. I also do not have Post-Cat 02's. I was always taught they have nothing to do with AF and are just a sanity check to ensure the cat is functioning correctly.

[AdsoYo]

Did you confirm, by some fashion, that you had a P0103, which is needed before you can say 'yup, it's in SD'? Just because it doesn't show up in the log's 'Details' tab isn't a reason to say it wasn't set, sometimes they don't if it's the first run cycle after a reflash even though it's there if you read DTCs with the 'Diagnostics and Info' button. Just asking if you checked. If you did, and it was, then fine. If you didn't and don't know if it was or wasn't, maybe think about starting over.

There's all kinds of cool shit you could be logging. Like MAF Status: Fail/No Fail, for just one tiny one. I know you don't want to mess with anything you don't see as directly related to the one specific thing you're trying to do, but there is stuff that will help you do that one specific thing if you just spend some time looking through what channels are available to you. I don't know how to read a log without TPS, for instance. It feels like wandering around a dark room wearing a blindfold and earplugs and big puffy mittens.

No I didn't disable the MAF, I totally forgot about needing to set the fail frequency way low to disable it. I mistakenly thought setting the "high rpm disable" to 9999 was enough.

Along the line of things I COULD be logging, is there a way to log when the PCM is performing the rear O2 test and then tell hptuners to ignore that data? That would be dy-no-mite.

I'd be interested in your Scanner config. Do you have one to share?

Also, what's the reasoning for leaving DFCO on? I can understand PE left on given this method (new to me) of doing the VE table with a wideband. Is an AFR commanded during DFCO?

I left DFCO on due to laziness. Yes I have a config on my laptop I can share. I'll edit this post later with the attachment.

That VE table doesn't look correct at all.

Just to be on the same page.. you fail the maf by unplugging or setting the diagnostics low were it will fail, see that a 101,102, 103 code is active so you know it is in speed density, then tune the VE tables

Correct?

This looks like you've been making VE changes with the MAF active

Yes you are correct. I forgot that detail and wasted hours this weekend.

[AdsoYo]

I bet this is the issue I am having, I thought maybe it had to do with a temperature multiplier somewhere because some days AF would be spot on. And on other days it would be off and my symptoms although not identical are pretty close to the Original Posters. I also do not have Post-Cat 02's. I was always taught they have nothing to do with AF and are just a sanity check to ensure the cat is functioning correctly.

That's what I thought too! Deleting the rear O2's is so popular how is this problem not more ubiquitous? And this wasn't happening when I was tuning my LT1 with the same PCM and same software. The only difference I can think of now is hptuners has been updated a few times. Otherwise the PCM is getting the same inputs as the LT1.

[2xLS1]

High rpm disable is the RPM where blended MAF/VE switches to MAF only.

[blindsquirrel]

The rear O2s do not control fueling. But the PCM does intentionally command a lean mixture and then a rich mixture to test the rear O2s. That does not mean the same thing as if the PCM were using rear O2s for feedback control. Read the page for P0420/P0430. The cat test/post-O2 test, or whatever these Gen3's are doing (don't really know if it's only one or the other or both, since there's no settings visible to change them, but Gen4's have both tests) is related to but not part of the P0420/P0430 diagnostics, so disabling those codes does not totally kill off the whole strategy.

Does the scanner show Commanded EQ change when it does these tests? It must, right? So if you're tuning with fuel trims, just set up a filter to exclude anything from your Graph when EQ isn't 1.00. Or plug in some damn O2s so it will stop doing stupid shit.

[AdsoYo]

The rear O2s do not control fueling. But the PCM does intentionally command a lean mixture and then a rich mixture to test the rear O2s. That does not mean the same thing as if the PCM were using rear O2s for feedback control. Read the page for P0420/P0430. The cat test/post-O2 test, or whatever these Gen3's are doing (don't really know if it's only one or the other or both, since there's no settings visible to change them, but Gen4's have both tests) is related to but not part of the P0420/P0430 diagnostics, so disabling those codes does not totally kill off the whole strategy.

Does the scanner show Commanded EQ change when it does these tests? It must, right? So if you're tuning with fuel trims, just set up a filter to exclude anything from your Graph when EQ isn't 1.00. Or plug in some damn O2s so it will stop doing stupid shit.

Commanded AFR stays at 14.73 throughout my logs. Or is that not the proper/ correct "channel" I should be using? I noticed there's also a "commanded equivalence ratio" channel. If the weather isn't stormy later this week I'll attempt another round of data gathering. Thanks for giving me a direction to move in with this issue.

Sirius, thanks for the heads up about the coil dwell time. I compared tables between LS3 and LS1 and they are quite different. I'm also going to attempt different fuel tables I think. Basically just copy/paste directly from the stock LS3 Corvette file.

[SiriusC1024]

You're welcome.

There's a gen4-gen3 fuel table conversion sheet floating around out there somewhere.

[blindsquirrel]

Trying to stick with Ye Olde AFR when the PCM is using EQ is like trying to make your MAP sensor display in inches of mercury...

[AdsoYo]

You're welcome.

There's a gen4-gen3 fuel table conversion sheet floating around out there somewhere.

Yes I have it (I think). I wasn't comfortable using some tables because it assumes LS3 injectors are 41.7 lb/hr but I also found conflicting information that they are 39 lb/hr. So far I've been treating them like 39's but I think I'll load up the 41.7 tables for shits and giggles.

[blindsquirrel]

Gen3 12576341 58psi non-referenced.hpt

screenshot.02-05-2023 19.22.51.png

[SiriusC1024]

Yes I have it (I think). I wasn't comfortable using some tables because it assumes LS3 injectors are 41.7 lb/hr but I also found conflicting information that they are 39 lb/hr. So far I've been treating them like 39's but I think I'll load up the 41.7 tables for shits and giggles.

Ah yes, I just worked on that problem. It's rated 39lb on various websites due to being flowed with n-heptane. So that's where the accounting comes in. The GM flow ratings are for gasoline, and they have factored in the density and viscosity differences between gasoline and n-heptane. I think that these measurements are taken at 40C. On the LS1/LS6 that difference is about (n-heptane flow rating) * 1.04. Here it's a little higher at 1.07. It may be due to gasoline mixture differences between the two periods of time when the calibrations were made, but I'm speculating there.

Regardless, the spreadsheet that converts GM data to GM data is correct enough. Use it.

Fun fact: Fuel Injector Clinic is especially accurate. They generate GM data with Viscor-16B instead of n-heptane. This is the fluid used by OEM's like Bosch and Siemens to do injector testing. Gives a much better approximation to gasoline than n-heptane.

[blindsquirrel]

The injector spreadsheet only gives accurate numbers with pre-2009 files, with the 128-640 axis & 63lb limit. '09-up 128-768 127lb source data is skewed if you convert it with the spreadsheet, which was created in I think like 2006 or 2007 and never updated when the ECMs changed in '09.

Since there are LS3 files from before the change, you can use those as the source and convert with the spreadsheet... but so many of the 'good' injectors come from after the change the spreadsheet is mostly useless now. File I posted above used 2010 Corvette LS3 as the source and was converted to Gen3 by hand.

https://forum.hptuners.com/showthrea...t-doesn-t-work

[SiriusC1024]

Oh yeah. Thanks, blindsquirrel.

[AdsoYo]

Gen3 12576341 58psi non-referenced.hpt

screenshot.02-05-2023 19.22.51.png

Ah yes, I just worked on that problem. It's rated 39lb on various websites due to being flowed with n-heptane. So that's where the accounting comes in. The GM flow ratings are for gasoline, and they have factored in the density and viscosity differences between gasoline and n-heptane. I think that these measurements are taken at 40C. On the LS1/LS6 that difference is about (n-heptane flow rating) * 1.04. Here it's a little higher at 1.07. It may be due to gasoline mixture differences between the two periods of time when the calibrations were made, but I'm speculating there.

Regardless, the spreadsheet that converts GM data to GM data is correct enough. Use it.

Fun fact: Fuel Injector Clinic is especially accurate. They generate GM data with Viscor-16B instead of n-heptane. This is the fluid used by OEM's like Bosch and Siemens to do injector testing. Gives a much better approximation to gasoline than n-heptane.

The injector spreadsheet only gives accurate numbers with pre-2009 files, with the 128-640 axis & 63lb limit. '09-up 128-768 127lb source data is skewed if you convert it with the spreadsheet, which was created in I think like 2006 or 2007 and never updated when the ECMs changed in '09.

Since there are LS3 files from before the change, you can use those as the source and convert with the spreadsheet... but so many of the 'good' injectors come from after the change the spreadsheet is mostly useless now. File I posted above used 2010 Corvette LS3 as the source and was converted to Gen3 by hand.

https://forum.hptuners.com/showthrea...t-doesn-t-work

Guys these are some top quality posts. Tomorrow before the lightning hits in the afternoon I'm gonna load up that injector data, tweak the scanner, and head out to do more driving. I'll report back.

[AdsoYo]

Wow what a difference! Car behaved like its old self, no wacky random ultra lean or rich swings. It was consistently slightly lean for a minute or two after a hot start but it always cleared right up and the car went back to being perfectly predictable. Possibly that rear O2 test? Here are the changes I made to the tune files BEFORE starting my drives for the day:

Loaded up blindsquirrel's injector data from the "Gen3 12576341 58psi non-referenced" file he posted above.
Created two separate files to use. One for MAF tuning, one for VE tuning. For the MAF file I disabled PE and closed loop. For the VE file I disabled PE, closed loop, set MAF fail to 0hz.
I was able to dial in both the MAF and VE tables to within 5% for all my most frequently used cells during normal driving and accelerating. For the cells outside those conditions, MOST are within 5% or close enough for me.

I attempted to place filters but quickly realized it was going to require lots of reading and Youtube videos and I was burning daylight.

I think the injector data is what made all the difference. The only other changes I made were copy/pasting LS3 dwell data and turning off closed loop in the tune as opposed to using the special feature in the scanner. The VE table looks normal again. Thank you all!
bettervetable.jpg