VersaTune User Forum

Hello all,

I am continuing my self-tuning “journey” and once again come to yall for help.

In my tune, I have set the WOT AFR to decrement to .782 (11.5:1) by 3k RPM and hold throughout the run. When I do a pull and take a log, it seems the ECU requests an AFR value much richer than .782 and don’t know why. I have seen .72, .74, .76 but it doesn’t ever just stay at .78, does anyone know why?

(also it appears the ignition timing is doing the same thing, ECU commanding timing values lower than what i set in my tune, but I have been trying to focus on one thing at a time...)

I have tested the following:
-setting “knocking” and “overload” AFR tables to the same values
- “0”-ing the last 3 cells in the “warmup enrichment” and “warmup enrichment decrement” tables
-setting the Open and Closed loop partial throttle AFR tables to something similar to WOT at the expected load values (~2.1 with my current WGDC)
-I can set “min desired lambda/afr” to .782 but then the ECU looses the ability to richen the mixture in the event of knock (or something else important that requires enrichment)

In a previous post (viewtopic.php?f=13&t=4568&start=10) mituc mentioned the following when discussing target IDC:
“95-98% IDC may be still safe. Usually once you go above 90% you need to inspect the sparkplugs from time to time to make sure all the cylinders burn right and get the right amount of fuel. You still need to leave some IDC room in case the fuel demand increases momentarily (knock, inputs from stability control module, fuel enrichment because of high temps, and so on) so tuning your engine for more than 95 may have some implications in certain situations which can only occur like once or twice in the life of the engine (because after such events usually the engine is done).”

-i have already unplugged my SWAS, so I don’t think there should be any inputs from stability control. Do I also have to press the DSC button? I think I tested that but I honestly don’t remember, need to go back out and try again I guess.
-follow up to the previous: I saw something on other forums about just pressing the DSC button while the engine is off vs holding the button prior to starting the car. Some say it doesn’t change anything, others say just pressing the button with the engine on does not fully turn off whatever systems. Did we ever come to a consensus on this?
-“fuel enrichment because of high temps” : huh… maybe this is something. Is this BATs or coolant temp? and is there a table in VT I can see/edit regarding this for testing purposes?

*note: I will try uploading my tune and a log but have had issues in the past with this, might post a dropbox link or something
*note 2: mods: built engine, CST4, catted downpipe, 3 port EBCS, 3.5 inch intake, 3.5 bar MAP, HPFP, no Aux fuel, California 91 octane

yep... still having problems directly uploading files

Dropbox link: https://www.dropbox.com/scl/fo/to9r6okk ... g48lv&dl=0
Google Drive link: https://drive.google.com/drive/folders/ ... sp=sharing

SandSoldier wrote: ↑September 11th, 2024, 3:07 pm -setting “knocking” and “overload” AFR tables to the same values

This is one of the reasons why the Cobb OTS tunes blow up stock engines making less power than the stock tune. Don't do that.

SandSoldier wrote: ↑September 11th, 2024, 3:07 pm -I can set “min desired lambda/afr” to .782 but then the ECU looses the ability to richen the mixture in the event of knock (or something else important that requires enrichment)

Exactly. Do not do that.

SandSoldier wrote: ↑September 11th, 2024, 3:07 pm -i have already unplugged my SWAS, so I don’t think there should be any inputs from stability control. Do I also have to press the DSC button? I think I tested that but I honestly don’t remember, need to go back out and try again I guess.

There are continuous inputs from the stability control module, including inputs from a freaked-out stability control module when the steering angle sensor is disconnected. The ABS sensors will still work so the stability control module will still have input and provide input to the ECU, even though the "stability control" part will be cut out without the input from the SWAS.
On a gen2 press the DSC button for 8 (or 10?) seconds to completely disable DSC, you will still have ABS. If you lose traction (or if you're at the limit of it) the SWAS doesn't matter, the stability control module will still sense that and there will still be some enrichment, even though not as much. If you're on a gen1 speed3 then pressing DSC once will do, you do not have to disconnect the SWAS.

SandSoldier wrote: ↑September 11th, 2024, 3:07 pm (also it appears the ignition timing is doing the same thing, ECU commanding timing values lower than what i set in my tune, but I have been trying to focus on one thing at a time...)

It does what it is supposed to do when the BAT and/or ECT goes up. It works as it should.

Going back to the title of this topic, in your tune you're asking for AFR of 11.5 and you're getting 11.3-ish while the BAT temperatures get pretty high. This is pretty good, almost spot-on!
However, there may be some fuel enrichment tables which we may not have access to and that work similarly with the high bat/ect ignition retard tables, and they're not the warmup-enrichment tables which are in effect when the engine starts and shortly after (as far as I know until the primary O2 sensor comes to life).

P.S.: with those load and APP settings I reckon the car feels quite "bumpy" at low/mid speeds and loads, especially when moving slowly like in parking lots...
P.S.2: APP req knocking - DON'T DO that When you have knock you do not want to still target out of the roof load. this is Cobb AP OTS tunes shit, do not import that in your tunes!
P.S.3: you can safely run more timing. 6 degrees at 6000rpm is 87OCT gas territory. Increase the timing by 0.5 increments for load 1 and above and see where it goes.

As per usual, life gets in the way of hobbies... but I'm finding a little bit of time to chew on this

Thanks for your reply Mituc, your comments make sense and I have decided to rework lots of tables including finally stepping into the load tables rather than leaving them at 3 and playing with WGDC tables.

I have decided to set Absolute limits > Max Injector DC to 90% but try to target load/AFR that'll get me to ~87% (to allow some enrichment like you talked about previously)

I am working on reverting "knocking" AFR table to something more reasonable, do you have a suggestion? if im targeting 11.5:1 at normal operation, maybe dropping to 11.0:1 (pump gas 91 OCT, but same question on an Ethanol blend)?

also, I'm thinking about the "overload" AFR table. If I have realistic overload spark retard and fuel cut limits and WGDC tuned to reduce overload, is there any benefit to richening AFR during an overload scenario (especially if im already at a high IDC)?

mituc wrote: ↑September 11th, 2024, 4:40 pm P.S.: with those load and APP settings I reckon the car feels quite "bumpy" at low/mid speeds and loads, especially when moving slowly like in parking lots...

Oh absolutely, its horrible! I changed so much at once (basically said screw the scientific method lol) that i couldn't track what table made it do that! I plan to pull some load out of it at lower RPM but was hoping with my engine build and turbo choice, I could still get some low end tq out of it. What APP settings are you referring to? "APP Mapping xxx Gear", "DBW Throttle xxx Extended", something else I'm not thinking of?

thanks a ton!

SandSoldier wrote: ↑October 26th, 2024, 7:22 am I am working on reverting "knocking" AFR table to something more reasonable, do you have a suggestion? if im targeting 11.5:1 at normal operation, maybe dropping to 11.0:1 (pump gas 91 OCT, but same question on an Ethanol blend)?

For a pump gas tune I'd leave the Knocking AFR tables the same as stock. The values in the stock knocking tables are still reasonable, you will not flood the engine with fuel, so I'd use those even on an ethanol blend.

SandSoldier wrote: ↑October 26th, 2024, 7:22 am also, I'm thinking about the "overload" AFR table. If I have realistic overload spark retard and fuel cut limits and WGDC tuned to reduce overload, is there any benefit to richening AFR during an overload scenario (especially if im already at a high IDC)?

To be honest, in my opinion the best strategy is not to have to run into those situations where you need to use the overload table values. I would tune the main tables properly and retard the timing and enrich AFR accordingly when the load goes past a value that I'd consider safe for the setup rather than tuning multiple tables for various situations you should realistically not run into.
And then just have the overload tables the same as the normal tables, and set the overload limit to a value that it's hard to reach on your setup.

SandSoldier wrote: ↑October 26th, 2024, 7:22 am Oh absolutely, its horrible! I changed so much at once (basically said screw the scientific method lol) that i couldn't track what table made it do that! I plan to pull some load out of it at lower RPM but was hoping with my engine build and turbo choice, I could still get some low end tq out of it. What APP settings are you referring to? "APP Mapping xxx Gear", "DBW Throttle xxx Extended", something else I'm not thinking of?

It's a combination of several things, but the most important is the acceleration pedal calibration tables which with those values in the low APP part will make the car jump all over the place. I would leave those stock for now until you figure out what does what.
And then it's the fact that you are trying to create a boost-target type of tune and totally murdered the load control in the tune while not setting either proper boost targets nor EBCS boost target corrections.
So basically your car now drives only based on how you push the throttle (which is not great because of the too aggressive APP calibration settings) and then past some point it will try to target boost somehow but the boost settings are left to stock. I don't think your car understands what you want from it at this point