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Annoying Trigger sync at Idle (Subaru DAVCS)


kaptainballistik
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I'm seeing an issue where at idle the car (Subaru Dual AVCS) will indicate a sync error on the Drivers side intake cam intermittently and the car will give a small stumble at the same time. bring the revs up to above idle and it goes away. Free rev motor.. no issue. CAM triggers have been Calibrated at 2000 RPM, Base timing is set to 10 deg exactly. Cam in question is the Intake cam ( trigger 1)

I'm "presuming" its a slight amount of "slop" in the AVCS units from the tension spring.. I couldn't see any miss triggers in the Trace. 

Secondly, is there a "trick" to getting a Trigger trace to record? I Hit record but it didnt..........

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Possibly your trig 2 arming threshold is too high at idle?  Usually AVCS is disabled at idle as oil pressure is too variable.  Subaru usually enables it around 1300rpm.  

For the triggerscope you just need to click the capture button while it is cranking or running.

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16 hours ago, kaptainballistik said:

I'm seeing an issue where at idle the car (Subaru Dual AVCS) will indicate a sync error on the Drivers side intake cam intermittently and the car will give a small stumble at the same time. bring the revs up to above idle and it goes away. Free rev motor.. no issue. CAM triggers have been Calibrated at 2000 RPM, Base timing is set to 10 deg exactly. Cam in question is the Intake cam ( trigger 1)

I'm "presuming" its a slight amount of "slop" in the AVCS units from the tension spring.. I couldn't see any miss triggers in the Trace. 

Secondly, is there a "trick" to getting a Trigger trace to record? I Hit record but it didnt..........

I dealt with this trying to run my 2011 STi on a Haltech ECU and found this interesting bit of information that seemed to be part of my issue perhaps.  It seems like with the USDM EJ25 dual AVCS engine the LH cam signal inverts itself above 1500 rpms.  I tried to get Haltech to help with that and had no luck so I bought a Motec M1 ECU and it works perfect so I assume perhaps they know about the inversion that happens and have it handled in the sync settings (but I have never been able to verify this).

Now, I am definitely hoping that if this is true, Link will discover this and handle it for dual AVCS EJ25 engines.  They have a trigger profile for EJ20 Quad AVCS but maybe that doesn't do the inversion while the EJ25 QUAD does.  I definitely don't know the complete answer here but perhaps this info is helpful. 

 

file.php?id=1080&sid=f3ca7d654018a8454842421dbac41007&mode=view
 

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Many Subaru and Mazda hall sensors invert at around idle speed and the trigger decoder accounts for this if it is known.  We have been caught out with a few odd ones over the years were we built a trigger decoder based on lacking info from a dealer or whatever but generally if it is tested in house it will be right from the start.  In most of the cases of inverting signals that I know of, generally one of the edges keeps the correct "spacing" while the other one moves so it is just a matter of using a specific edge count rather than "levels" for the sync.  If you look at the example you posted above for instance the falling edge is always showing the correct pattern.  One of our in-house dyno mules is a quad VVT EJ25 so pretty sure we have it right.  

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8 hours ago, Graham BPT said:

I dealt with this trying to run my 2011 STi on a Haltech ECU and found this interesting bit of information that seemed to be part of my issue perhaps.  It seems like with the USDM EJ25 dual AVCS engine the LH cam signal inverts itself above 1500 rpms.  I tried to get Haltech to help with that and had no luck so I bought a Motec M1 ECU and it works perfect so I assume perhaps they know about the inversion that happens and have it handled in the sync settings (but I have never been able to verify this).

Now, I am definitely hoping that if this is true, Link will discover this and handle it for dual AVCS EJ25 engines.  They have a trigger profile for EJ20 Quad AVCS but maybe that doesn't do the inversion while the EJ25 QUAD does.  I definitely don't know the complete answer here but perhaps this info is helpful. 

 

file.php?id=1080&sid=f3ca7d654018a8454842421dbac41007&mode=view
 

I'll tell you on Saturday afternoon how good Link Has it :) .. All things well, Its Saturday Dyno.... (The trigger trace appears to be happy at least)

14 hours ago, Adamw said:

Possibly your trig 2 arming threshold is too high at idle?  Usually AVCS is disabled at idle as oil pressure is too variable.  Subaru usually enables it around 1300rpm.  

For the triggerscope you just need to click the capture button while it is cranking or running.

Filter is set to 1 ( Low) as per default, PWM for AVCS is 250 HZ. (so default...) I've seen some suggested configs indicating 300hz for the AVCS, Is there any advantage to this? (JDM 2L DAVCS motor). AVCS is set to enable at 1200 rpm/50 degrees ECT.
image.png.a8a5d056c9c8a321c742b14c72488dff.png
 So Maybe bump the threshold up by 0.1 until the trigger is stable?

Ill try the trigger record again, ( I hit the record button, Ill blame the laptop... Maybe its a Layer 8 error.....So it could be the operator!.)

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9 hours ago, kaptainballistik said:

Filter is set to 1 ( Low) as per default, PWM for AVCS is 250 HZ. (so default...) I've seen some suggested configs indicating 300hz for the AVCS,

On our V11 test car the factory ecu uses 300Hz, I have tried 300 & 250Hz and not noticed any difference in the control so either is fine.  

 

9 hours ago, kaptainballistik said:

So Maybe bump the threshold up by 0.1 until the trigger is stable?

No I said "too high", but thinking again - is your trigger 2 hall or reluctor?  Obviously my comment doesnt apply if your trig 2 is hall.  

 

9 hours ago, kaptainballistik said:

Ill try the trigger record again, ( I hit the record button, Ill blame the laptop... Maybe its a Layer 8 error.....So it could be the operator!.)

What record button?  You mean the capture button right?  >ECU controls>trigger scope.

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14 hours ago, Adamw said:

 

 

No I said "too high", but thinking again - is your trigger 2 hall or reluctor?  Obviously my comment doesnt apply if your trig 2 is hall.  

 

What record button?  You mean the capture button right?  >ECU controls>trigger scope.

Trigger scope logging: Yeah, That Button :D. ill try it again on Thursday.

Threshold adjust: So I should try going DOWN by 0.1.. after seeing if correcting the filter level on trigger 1 helps (see below)

 

Trigger config:

I am running the 3 wire CAM triggers on the intake., 2 wire on exhaust. ( as per the JDM motor), 2 wire on Crank. (Trigger 1 tis the crank......correct?)

Trigger 1 is set to Reluctor , filter level 2. "Default" by the Help guide says is should be 1...... Can this be part of the issue? ( End user error.. It was 1am when I configured it....) 2 wire sensor... So that should be reluctor.

Trigger 2 is set as optic/hall, as per the DAVCS advisory for Davcs.

Sorry for the possible silly questions, Bashing away at the car after work till all hours! ( sleep? who needs that!) and screwups are slipping in.....

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  • 3 months later...

Back on this one.. unfortunately...

What I'm getting is a fairly random "miss" when the car is idling or at light load, The logs aren't showing any error or issue at the time it has the miss. 

Funny thing is, the ECU will show The intake cam on the Cyl 1 Bank (cam one..) will flash an error, but i cant see anything in the logs. or the trace. occasionally Cam 1 ( the intake cam that ISNT the Trigger 2 "input" and both exhaust cams will flash red when the miss happens (when you are on that page and watching...) Trigger trace seems fine when it happens.....

So i can get a Meaningful log out of the unit, which exact Parameters should I be looking at/logging? 

I'm happy to beaver away at it,  Im kinda stubborn like that..... But im dang well missing something in the logs!

 

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On the OEM ecu I have seen quite a few ej255/ej257 intake cam sensor failures causing weird symptoms. Another problem to look for is the avcs sprocket is sticking and not moving properly causing the camshaft to be advanced. The avcs solenoids also are a wear item since they start sticking too.

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2 hours ago, 02wrx said:

On the OEM ecu I have seen quite a few ej255/ej257 intake cam sensor failures causing weird symptoms. Another problem to look for is the avcs sprocket is sticking and not moving properly causing the camshaft to be advanced. The avcs solenoids also are a wear item since they start sticking too.

If I remember correctly the AVCS units have a mechanical lock, so in theory I should be able to get the oil real hot, turn off avcs, let the motor cool then start it with avcs off and then test. 
 

in theory I think that will make the system locked and I won’t see any “scatter” (I’m seeing a handful of degrees) so if one can is jittering , that’s the issue! (Using a timing light..)

I guess the other question is how much timing jitter for you see with a timing belt in the first place?

I’ll also take the cam sensor off my road wrx and chuck that on too

(I don’t get these piston motor things.. rotaries are MUCH SIMPLER! )

Something else that could be compounding issues could be the thing isn’t getting hot enough for the avcs to actually work properly.. it’s barely getting 80 degrees oil temp with the freaking huge oil cooler it has!.

 

or I could just have a Bad ground somewhere......  it’s going to be a A WTHeck or a Durr issue..... so a full check for earth leakage to radiator Hotwire power/grounds amp meter on power feed stupidity check is also planned!

I’ll also add this motor was a $700 special from a motor that was in a prang (dropped a pile of valves when it shredded the timing belt in the crash and did zero piston damage) so besides a leakdown Test (which was very good) I have never run the motor previously.

 

(anything damaged was swapped with known good bits... )

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Kinda good News... MEGAPOST!

I Swapped out the LH and RH Intake Cam Sensors and the car is much improved. Still a slight background "miss". when the car starts to boost, and its a total pain to start...  Unless the Crank CAS I fitted may have an issue... But once its running it seems fine ( motor wasn't sparking for some reason...All trigger values set as default for a DAVCS Default map.... Reluctor on Trigger one, Hall on Trigger 2)

I calibrated the Triggers and the car is now a pig to start ( wont spark) but will eventually ( and with no discernible reason) decide to run. Trigger traces and RPM is indicated when it does the not starting antics.

10 Deg ignition lock however is rock solid 10 deg from the timing light

Basically I swapped out the Crank trigger, Intake cam triggers, Redid all grounds and Fitted a hotwire to the coils. It appears the CAM triggers had been "smoked" as part of the accident the motor was in, Strange red ooze was found on them coming from a join!!!! 
Exhaust cam triggers show no errors so I'll leave them alone.. for now!

Unfortunately I forgot to email myself the Logs.... but the car hits over 12 pound boost now! (before it lost the plot at 5 PSI)

PICS: 2245 and 2248 is at Idle just after a cranking trigger cal, 2256 and 2258 are at 3000 rpm just after I did the Trigger calibration at 3000... What im noticing is about .5 Volt "hair" on the trigger.

Is the noise on the Trigger 2 "normal" on a Subaru? ( Do i need to go find some ferrite cores?)

I have noticed the Pulley/harmonic balancer isn't the truest in the world ( Probably slightly worse than usual...Subaru pulleys are woeful) So would the trace indicate if i've got a small amount of crank runout?

I doubt it, but I'm chasing weird issues, I cant rule out anything!

IMG_2256.jpg

IMG_2258.jpg

IMG_2248.jpg

IMG_2245.jpg

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Ok, This one is getting .. Wierder...

What appears to happen is the Threshold for the Crank trigger isn't being "crossed" during initial cranking if the battery isn't really well charged ( Just under .7V)

If you don't realise this and do a VVT calibrate it REALLY messes the computer up!

I'm going to add a 200 Rpm /0.7v threshold and see what happens....

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Sounds like you are a bit confused. 

Why would you be trying to calibrate VVT during cranking?  It should be done at fast idle so the cam speed is stable.

You cant adjust the breakpoints for trigger arming thresehold.  500RPM is the lowest breakpoint and below this the threshold is not interpolated.  So whatever value you have in the 500RPM cell will be used all the way down to zero RPM.  It would be typical to have about 0.5V in the 500rpm cell, you can drop it to 0.2 or 0.3V if your trigger voltage is low during cranking.   

 

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Yeah, I am kinda.. perplexed...... The car "normally" starts after a few pokes. 

Cool, I'll try a .5 at 500 rpm (I noticed the Subaru JDM trigger threshold for the crank is 0.5, the DAVCS one is .8, I had verbatim copied the DAVCS settings).

I think the issue is I normally Charge the car if I cant get it to start........ So that a Id10t error......

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  • 2 weeks later...

OK,  So the starting issue got solved with some ... swearing.

Issue comes down to the Odyssey Battery, when fully charged, is Great! What was happening is the Battery charger we were using were switching to trickle mode at 12.3 Volts. Thus the Car was dropping to 10.5V on cranking and thus the Trigger threshold ended up being to low as it frankly wasn't charging the battery. Cheapo Supercheap Battery chargers.... 

I Was using the DAVCS basemap 0.8 threshold at 500 RPM for Trigger 1 as well, Changed to .5 and all good! I did need to De-foul the plugs (Iridium....... bleh) at it had Sooted them like a Manky Victa 2 stroke!

When I put Decent charger (The one from my Garage) on the car and the Battery got a decent charge, 0.8 Threshold isn't an issue. The Battery also had significantly more capacity for cranking and Higher crank Voltage (Over 12v) Quite frankly it starts on the key now!. The Particular charger also had issues charging my motorbike enough.. So Its in the repair pile.

SO the moral is.... Get the right charger for the Battery! :blink:.. And run .5 as the Cranking trigger threshold for Trigger 1...

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  • 3 weeks later...

Ok... Footnote time.

Fired car up on dyno and it made a sorta stuttery 15 PSI pull... ok, lets go with that. The fire it up and do a pull actually hid an issue... 

The car then proceeded to fall on its face on boost.  OK, Take it home and check everything.

So as you do. I picked an end of the car and worked forward. I decided the fuel tank as I was sick of poking sticks at the engine bay. As I started pumping out fuel by disconnecting the rail and turning on the pump it all went fine.. For the first 2-3 litres. then I started seeing air in the fuel..

Unbeknown to me the Submersible "rubber" fuel line was disintegrating..... and the fuel pump was sucking air in. Funny thing is, the car would still build fuel pressure (Gauge read what was expected..)  Changed everything in the tank to 200 Series Teflon and guess what.. Even my off idle soggyness when blipping the throttle was gone... Which considering its a EJ20 in a BRZ, I put down to base maps..... Random staling gone and seems fine!

You learn a new one every day.......
 

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