Desired AFR 14,7:1 in WOT? Why?

Tuning discussion for all second generation Mazda 2.3 MZR DISI Turbo powered vehicles
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MiPil
Posts: 23
Joined: December 5th, 2019, 2:19 am

Desired AFR 14,7:1 in WOT? Why?

Post by MiPil »

Hello all,
In gen2 tuning I see sometimes this issue:

In WOT jump the desired AFR to 14,7:1 (in tables are f.e. 11,5:1) and the actual AFR falls to 8-9:1.

I see this in two different cars:

Car one:
- stock, only 2nd cat removed
- this issue is when you kick down the pedat under 2k rpm (f.e. 1995rpm is problem, 2050rpm is all right)
log: afr_fail_example1.csv -in log more WOTs (see log time), some good, some with issue

Car two:
- forged, CST4, decat
- disable swas by Versa and disable DSC
- this issue is when comes traction problem. Next situation is afr to 8:1 -> too much injector DC -> Injector DC safety function
log: afr_fail_example2.csv -its from street driving, but when you see to load higher then 2, you will see this issue.

Is this normal? Is this some safety function? Is possible control it?

Thank you for answers
Michal
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2006 MS6 - BNR S4, FMIC, BigBrakes
MiPil
Posts: 23
Joined: December 5th, 2019, 2:19 am

Re: Desired AFR 14,7:1 in WOT? Why?

Post by MiPil »

Hi Mituc,
thank you for your answer.

Car #1: Stock intake, stock maf settings. All values are correct- afr desired=afr actual in WOT. HPFP is not upgraded, but all pressure values is ok, when the ECU holds desired ARF.
This car is not clutch slipping, not bad MAF cal, not tyre slipping.

Questions are:
- is this behavior safety function (desired afr 14,7; real afr 8-9)?
- if yes, is posible to start it with kick down pedal under 2k rpm?
- why this state ignore all tables (include Min desired lambda in Absolute limits)

Car #2:
Fully forged engine, single mass flywheel, carbon ceramic clutch with racing pressure plate, slick tyre, big brakes, etc... The intake is CS 3", the CS table with calibrations is good - in normal wot arf match.
The log is crazy - I know :-) In normal WOT all looks great. But in ,,little sport driving" (corners in mountain) the ecu makes this.
Go full engine torque to first 2 gear is required - this car wil be for adrenalin and tyre burning in low gears is required.
Questions is why ecu dont follow the desired afr, set f.e. 8,5:1 and ignore Min desired lambda in Absolute limits and other tables.
2006 MS6 - BNR S4, FMIC, BigBrakes
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Desired AFR 14,7:1 in WOT? Why?

Post by mituc »

No, it's not normal (like nothing in these logs is, but let's focus on your question for now). I've seen this happening in several situations:
- when the MAF calibration is too much off and the ECU is struggling to keep up the fuelling on par with the values from the MAF calibration;
- when the clutch is slipping
- when the car looses traction.

Probably at least for car #2 all 3 are happening. I'm not sure what one would expect to send 500+ Nm at the wheels in 2nd gear (hint: we have per gear load targets/limits).

P.S.: At this point it's hard to tell if the car from the 2nd example, forged or not, will live a shorter life than the one in 1st example because of the chaotic tuning/setup, or if the car from the 1st example will blow first because it has no fuel pump internals and will throw its guts out in the midrange during a pull. Also the clutch from the 2nd car is slipping.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Desired AFR 14,7:1 in WOT? Why?

Post by mituc »

MiPil wrote: December 28th, 2022, 10:59 pm Car #1: Stock intake, stock maf settings. All values are correct- afr desired=afr actual in WOT. HPFP is not upgraded, but all pressure values is ok, when the ECU holds desired ARF.
Change the unit for fuel rail pressure from mPa to PSI to get a better resolution. You will see the fuel rail pressure dropping to 1400-1450 in the mid range, because that's 10mPa.
The fact that the O2 sensor still sees the target AFR may be a combination of misfire (resulting in lean mixture) and after-burning during the exhaust stroke. I would not take any chances and just assume it's ok, when the above happens you will get some crispy pistons and some cracked ringlands in no time.
MiPil wrote: December 28th, 2022, 10:59 pm - is this behavior safety function (desired afr 14,7; real afr 8-9)?
Normally you'll see the AFRs dipping into the high 8s when traction is lost for several seconds in a row. the ECU enriches the mixture to make less power. The values the desired AFRs go when that happens become irrelevant, and on the cars I've tuned and had this happening I've either seen the desired AFRs staying around the target or dropping slightly towards or even below the min desired AFR, but never matched the actual (actually it was off by 0.5 to 1.0AFR).
MiPil wrote: December 28th, 2022, 10:59 pm - if yes, is posible to start it with kick down pedal under 2k rpm?
I go WOT in all cars below or around 2k RPM during the tuning process all the time. The purpose of this is to tune the response and limits in that area since it's well known for ZZB.
MiPil wrote: December 28th, 2022, 10:59 pm - why this state ignore all tables (include Min desired lambda in Absolute limits)
Because it's an ECU safety thing, in these cases it will communicate with the stability control module. Deactivate DSC and TC when you go for spirited driving. The procedure to completely disable stability control (DSC) in BLs/gen2s is different than for BKs/gen1s.
MiPil wrote: December 28th, 2022, 10:59 pm The log is crazy - I know :-) In normal WOT all looks great. But in ,,little sport driving" (corners in mountain) the ecu makes this.
In this case the transition tables and comp tables are tuned wrong.
Also the clutch is slipping on this car which makes ECU go nuts while already went nuts 2 cpu cycles ago.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
MiPil
Posts: 23
Joined: December 5th, 2019, 2:19 am

Re: Desired AFR 14,7:1 in WOT? Why?

Post by MiPil »

Thank you Mituc for your answers.

How is please correct way to disable DSC in gen 2?

We try a ,,brutal force test" - remove a ABS fuse. This enrinchment is stopped and actual afr follow desired afr in tyre slipping condition -> it's real a DSC function.
2006 MS6 - BNR S4, FMIC, BigBrakes
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Desired AFR 14,7:1 in WOT? Why?

Post by mituc »

MiPil wrote: January 2nd, 2023, 12:59 am How is please correct way to disable DSC in gen 2?
As far as I remember you have to press the DSC button for 8 or 10 seconds. Pressing it only once will only allow you some wheel slip at low speeds, but if you turn the wheel or if the speed goes above a certain threshold it will start doing funny stuff with the AFRs and ignition (which you will see as knock retard, but it's just ignition retard induced by the stability control).
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
MiPil
Posts: 23
Joined: December 5th, 2019, 2:19 am

Re: Desired AFR 14,7:1 in WOT? Why?

Post by MiPil »

Thank you Mituc :-)
2006 MS6 - BNR S4, FMIC, BigBrakes
mituc
VersaTuner guru
Posts: 1324
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Desired AFR 14,7:1 in WOT? Why?

Post by mituc »

MiPil wrote: December 28th, 2022, 10:59 pm - is this behavior safety function (desired afr 14,7; real afr 8-9)?
Coming back to you on this: yes, this is what gen2/BLs will do, indeed. The ECU won't give a shit about the min desired AFR, it will just spray fuel like a maniac. However the AFRs will go into low 9's or high 8's only when the traction loss is massive and prolonged.
Funny thing though is that the desired going as high as stoich is a tentative of correcting those super rich mixtures, making me think that the ECU is somehow forced into enriching the mixture. So I guess these BLs don't really know what they want, do they?!
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071 gen2, ~509BHP @34PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 330-ish BHP
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