AFR varies by gear

[ryancyates]

Euro S50B30 turbo, E36 G4X plug and play.

Today is hot here in Florida so I thought I would get around to tuning the IAT correction table.  I've done most of my tuning at night with an IAT of 80-88*.  Today I'm getting 107-115* IAT.

I've been doing my nighttime pulls in 3rd but since I can see during the day I've been doing 4th gear and noticed a difference in AFR.

I'm awfully nitpicky with my tunes since I have unlimited time to mess with them and there's no reasonable situation for me to be in 4th gear at 2000 RPM but I'm just simulating what I would do on the dyno.

Anyway here's two screen shots of 3rd and 4th gear after making some fueling modifications in 4th gear.

Ignore the acceleration spikes, I'm still working through that with the ITBs.

You can see the 4th gear graph is relatively consistent, still rich, but following the general AFR target.  I could just use some minor cell adjustment and pulling a bit from the IAT table.

Now, with the fueling altered in 4th gear if I do a pull in 3rd its rich on the low end but near on target under full boost.

I understand real world conditions and mechanical load can affect things I'm just wondering if I'm missing something.  Or if it's latency due to cell speed between 3rd and 4th.  Its pretty safe, just more so wondering if I'm overlooking something.

[0x33]

Transitional loads through various gear will affect fueling like this. You could set up a bunch of adjustment maps based on gear and load if you have enough time but the possible variations and enviornmental factors will take a while to account for, you might find better results dialing in the closed loop fueling control to keep you on target for these small discrepancies a much better use of time. 

[ryancyates]

11 minutes ago, 0x33 said:

Transitional loads through various gear will affect fueling like this. You could set up a bunch of adjustment maps based on gear and load if you have enough time but the possible variations and enviornmental factors will take a while to account for, you might find better results dialing in the closed loop fueling control to keep you on target for these small discrepancies a much better use of time. 

That's pretty much what I figured.  This is the first turbo ITB car I've tuned as well as my first time using LinkECU and then throwing the variable cam timing on top of that I've really been rattling my brain the last few weeks.

The major discrepancy is happening between 2000-3000 in 3rd and 4th which isn't an issue while driving normally.  There's just so many correction and compensation maps in Link I wasn't sure if I was missing something like have been every step of the way so far.

[Adamw]

Can you attach a copy of your tune and the actual log file, its pretty hard to tell anything from a picture but it doesnt look too far out of the ordinary to me.  

Without the log and just eyeballing the pics it looks like the logs show something like this:

RPM                     3000      4000      5000      6000

3rd gear              12.3:1      11.1:1       11.25:1    11.25:1

4th Gear              12.3:1      11.4:1      11.0:1      11.25:1

So you have a max of about 3% difference in AFR between the 2 runs?

What wideband controller do you have? - it looks like you are only getting about 7 updates a second, that's not going to do you any favours.

[ryancyates]

1 hour ago, Adamw said:

Can you attach a copy of your tune and the actual log file, its pretty hard to tell anything from a picture but it doesnt look too far out of the ordinary to me.  

Without the log and just eyeballing the pics it looks like the logs show something like this:

RPM                     3000      4000      5000      6000

3rd gear              12.3:1      11.1:1       11.25:1    11.25:1

4th Gear              12.3:1      11.4:1      11.0:1      11.25:1

So you have a max of about 3% difference in AFR between the 2 runs?

What wideband controller do you have? - it looks like you are only getting about 7 updates a second, that's not going to do you any favours.

I just compared to two and yes they are actually very similar in AFR, interesting.

So, the obvious difference in the two logs is the spool up rpm in 3rd vs 4th gear.  I'm using TPS x RPM for fueling and open loop lambda control.

Is there a reason why the AFR isn't following the target in this situation?  Either way I can live with it because its fine during regular driving.

And I'm using an AEM wideband wired to sensor ground at the ECU and stock O2 channel for signal.

PC Datalog - 2023-04-26 2;14;42 pm.llgx PC Datalog - 2023-04-26 2;16;17 pm.llgx

[koracing]

FYI there have been about 4 million AEM widebands - so it's best to include the actual model part number of the wideband controller when saying "AEM wideband".  Current models are the X-Series (with CAN comms and a ground reference on the analog output) which work pretty well, and the "classic" 30-4110 which no one should be buying to use with an ECU as the primary tuning device at this point.