BRZ GT86 ECU help

[Draven]

I have a hybrid situation going on where i have the GT86 ecu running a 2021 FA24 using the factory 2013 wiring harness.

I flipped the crank sensor to hall effect in the software and am using the EJ20 QUAD AVCS trigger mode but I believe there is a slight difference in the cam triggers which is leading me down the wrong path on my issue.

 

Cold start no matter how hot it is outside the car will start.  If i then drive someplace it'll crank but won't fire.  This lead me to believe it was a heat soak issue I adjusted the crank enrichment table from 194F onward and thought I had it but still would crank and no start but seemed to only require a few starts to get it to fire where as before i was just stuck there.  I also adjusted the charge air temp table to use ECT more than IAT when trying to start.

I guess my question is, am I having weird cam trigger issues when it's warm or heat soak or both?  Attached is a log of it starting and one not starting.

 

Can't be as simple as running the calibration mode in the VVT settings?  I did it yesterday but i just saw it needs to be out of lock out and in some RPM to have it set itself?

 

start log file PC Datalog - 2024-08-30 10;07;29 am.llg5 brz tune file.pcl5 no start log file - 2024-08-30 10;51;29 am.llg5

[Adamw]

It sounds most like a mis-sync issue to me, so a trigger scope capture during a no start would be useful.   

The other thing I would suggest is temporarily set your staged injection staging table to 100% so it using the port injectors only, during start up, as a quick test to rule out all the DI related variables that may be different in the FA24.  

 

2 hours ago, Draven said:

Can't be as simple as running the calibration mode in the VVT settings?  I did it yesterday but i just saw it needs to be out of lock out and in some RPM to have it set itself?

VVT needs to be outside of the lockout conditions to calibrate, but VVT is not involved in the trigger synchronisation or any start-up functionality so isn't related to your issue.  

 

[Draven]

This should be a scope 1st start of the day and then the next is from a 50 minute drive and a no start immediately after shutting it off and trying

starting Trigger Scope - 2024-08-30 10;08;04 am.llg5 no start 1 Trigger Scope - 2024-08-30 10;51;49 am.llg5 no start 2 Trigger Scope - 2024-08-30 10;52;24 am.llg5

[Adamw]

Ok, so these scopes show the problem.  The cam wheel on these has a 4-1, pattern, so the ecu expects to see 2 edges 180deg apart then a 360 deg gap until the next edge.  Your good scope matches this correctly.  You have trig 2 edge set to falling, so I have marked the falling edges that the ecu is looking at: 

 

Now if we look at the "no start scope" you will not see this pattern.  You might also notice most of the teeth are inverted compared to the scope above: 

 

In engines that have sensors that invert like this, you will usually find 1 edge will give the correct position while the other edge moves.  In this case it looks like the rising edge is the correct one.  If I mark the rising edge on trigger 2 on the same scope then it looks more like the expected pattern:

 

So, in the trigger settings, change trig 2 edge to rising will likely solve the mis-sync issue.   This "flip" often occurs around idle speed, so if you see any weird VVT behaviour on ay of the other cams then swap the active edge on those also.  

 

[Draven]

Well you might have nailed this because I do see weird VVT behavior at idle.   I'll go do this today and report back.

 

So why would it be able to catch the correct singles on a first start and then have the issues once it's warm?

[Adamw]

7 hours ago, Draven said:

So why would it be able to catch the correct singles on a first start and then have the issues once it's warm?

It may be that temperature or battery voltage affects the RPM at which the sensor inverts its signal, or possibly the signal may never be correct, so it just syncs on the correct phase by luck rather than by design.

[Draven]

I flipped it to rise and now it starts as expected every time.   Thanks so much for the help!

The cams vvt also track now correctly as well at low RPM where as they would not before.