Weird Rich->Lean Light Throttle G4X

[wastegate]

Have a weird little issue that has been tickling my annoyance. When cruising on the street, normal 50-60kph light throttle, sometimes I would feel the engine drop off in torque or labour just a tiny bit. I'd look at the Lambda and it would be pretty lean at 1.15 etc. Then restores back to around 1.0 and feels normal.

I've tried to work out what is causing it for a while now and from what I can see in my tune and ecu logs, really nothing is a smoking gun. It just seems to go rich, then Lambda Fuel Correction kicks in, leans it out a bit back to 1.0 then about a couple secs later, bam, leans out where CL Lambda takes out all the fuel it put in. All this while same throttle input, speed and engine speeds. Eg just cruising down a 60kph road.

Engine is a 2JZGTE, 272 Cams, Turbo etc with a A340e Auto. I'm kinda starting to lean on a failing auto maybe putting load on the engine while cruising? I can't find anything in the log to say the ECU is doing it. Just weird it goes mega rich.

Here is a link to the tune file.
https://drive.google.com/file/d/13siHUU6E5GH92eacB36jkLJ6z8c5IkyZ/view?usp=share_link

Here is a link to the ECU log (example of what I'm looking at is at 1:10)
https://drive.google.com/file/d/1TOzDgf1oI7hnyDx7mhaMa7fmD05d8uqt/view?usp=share_link

Any advice is appreciated.

[RyanG]

Following for an update on this one.. I had a look through, but nothing obvious seemed to jump out.

[koracing]

How are you controlling the A340e trans? 

Looking over your tune and you datalog definitely doing some weird stuff - but yeah hard to say if there is something going on due to the trans locking up and unlocking or something else.  Throttle is moving a bit in those areas also but not a ton.  Is that the normal load required to maintain that speed?  You're near to atmospheric pressure there -- more so that I would think necessary for 40ish mph.  No other mechanical drag - rear end, brake system, etc.?

[wastegate]

52 minutes ago, koracing said:

How are you controlling the A340e trans? 

Looking over your tune and you datalog definitely doing some weird stuff - but yeah hard to say if there is something going on due to the trans locking up and unlocking or something else.  Throttle is moving a bit in those areas also but not a ton.  Is that the normal load required to maintain that speed?  You're near to atmospheric pressure there -- more so that I would think necessary for 40ish mph.  No other mechanical drag - rear end, brake system, etc.?

Trans is controlled by a Compushift Sport TCU.

TC is not locked up at that point. I log the TC lockup as well. 

It seems to be repeatable at that speed. Can certainly feel it, at first I thought it was going lean as that was what I was seeing on the dash, but it's going rich then closed loop catching it, then whatever is causing it to go rich stops and CL has to add fuel again. 

I have pretty low vacuum anyway even at idle due to my cams 272, 9.9mm lift. To a point I'm putting a vacuum pump on for my brakes to help.

Just seems puzzling that during that low speed cruise it happens pretty consistently. 

If it is a driveline issue and something in the trans binding up causing a little extra load I should see that extra load in the logs?

[koracing]

One would think it would affect the load/MAP reading if it were loading up differently.  In my experience with larger cams, once you're past idle they still pull a bit more vacuum than you're seeing.  272s are a pretty common size on the 2jz and I've never needed to run a vacuum pump - nor can I think of anyone I know with one running a vacuum pump.  Tuned cars with much larger cams and they still generated *somewhat reasonable* amounts of vacuum/load off idle.  Perhaps a misfire or dropping a cylinder maybe?  Misfires show up as lean in the wideband.  Your dwell looked reasonable to me but maybe try cutting it in half in case the coils are getting hot?  Really not sure what the best next step would be.   Earlier in your log there were several fuel cut events - do you know what was causing those?

[Adamw]

Does it still happen if you change target lambda to 0.95 in that general area?  A target of 1.05 with extra overlap and large injectors may be pushing your luck a bit.

[wastegate]

11 hours ago, koracing said:

One would think it would affect the load/MAP reading if it were loading up differently.  In my experience with larger cams, once you're past idle they still pull a bit more vacuum than you're seeing.  272s are a pretty common size on the 2jz and I've never needed to run a vacuum pump - nor can I think of anyone I know with one running a vacuum pump.  Tuned cars with much larger cams and they still generated *somewhat reasonable* amounts of vacuum/load off idle.  Perhaps a misfire or dropping a cylinder maybe?  Misfires show up as lean in the wideband.  Your dwell looked reasonable to me but maybe try cutting it in half in case the coils are getting hot?  Really not sure what the best next step would be.   Earlier in your log there were several fuel cut events - do you know what was causing those?

Certainly some things to try. In regards to vacuum, it's only an issue with me for the first time after startup with minimal brake asset. I'll have a look at those misfires. Change plugs etc. Running pretty low gap at 0.3 as I'm still running the stock coils. R35 coils are on the plate so i can increase gap again at the power end. 

Will have a look at those misfires, what time stamps are they? I do have a ignition retard on gear change.

 

44 minutes ago, Adamw said:

Does it still happen if you change target lambda to 0.95 in that general area?  A target of 1.05 with extra overlap and large injectors may be pushing your luck a bit.

Will give it a go Adam cheers

[wastegate]

On 2/18/2023 at 7:52 AM, koracing said:

One would think it would affect the load/MAP reading if it were loading up differently.  In my experience with larger cams, once you're past idle they still pull a bit more vacuum than you're seeing.  272s are a pretty common size on the 2jz and I've never needed to run a vacuum pump - nor can I think of anyone I know with one running a vacuum pump.  Tuned cars with much larger cams and they still generated *somewhat reasonable* amounts of vacuum/load off idle.  Perhaps a misfire or dropping a cylinder maybe?  Misfires show up as lean in the wideband.  Your dwell looked reasonable to me but maybe try cutting it in half in case the coils are getting hot?  Really not sure what the best next step would be.   Earlier in your log there were several fuel cut events - do you know what was causing those?

Those fuel cuts are the overrun fuel cut.
 

Messed around a bit today, turned off CLL and can manage to replicate the issue while the car is stationary and just revving to 2000-2500rpm. Goes very rich @ ~0.7 lambda. Then by about 3000 rpm it comes good again. So played with the VE table and can get it a little leaner in that spot but it's a hole in the map deeper than a diamond mine. Something is certainly up.. I wonder if a injector is to fault here.. 

I will change plugs first and check them. Then get the injectors cleaned.

[koracing]

VE resonance can do weird things.  It's pretty common on 3SGTE engines with aftermarket intake manifolds to have VE spikes at 3000-3200rpm where sometimes the VE values create a ridge in the fuel table.  If everything else checks out that you're testing - try adding resolution like every 100rpm around that area and dial it in on the fuel table.  If it runs good/smooth then that's just what it needs.  If you don't have extra columns available on the main fuel table - can always use either the 4D or 5D tables, or the 2nd fuel table in overlay mode as an option if you aren't otherwise using it.

[BigBoiMR2]

On 2/21/2023 at 4:48 PM, koracing said:

VE resonance can do weird things.  It's pretty common on 3SGTE engines with aftermarket intake manifolds to have VE spikes at 3000-3200rpm where sometimes the VE values create a ridge in the fuel table.  If everything else checks out that you're testing - try adding resolution like every 100rpm around that area and dial it in on the fuel table.  If it runs good/smooth then that's just what it needs.  If you don't have extra columns available on the main fuel table - can always use either the 4D or 5D tables, or the 2nd fuel table in overlay mode as an option if you aren't otherwise using it.

Thank you for this info. I've put a large spike into my VE table to deal with a lean spot in my map between 3000 and 3200 rpm on my 3sgte and was wondering if it was a mechanical issue, good to know that its normal.