2JZ-GE VVT-i first start difficulty

[traingeek2000]

Trying to get my 2JZ started up, it's beginning to kick over but just barely. Lots of smoke from the exhaust, maybe too much fuel? My base timing offset seems out of line with what other JZ VVT-i users have posted about, but with a timing light I verified 245deg offset compared to the ~205 that most users had posted online. I've attached my startup map and a log file. It could also be that the 150RPM that my starter can manage is just too slow.

supra map1.pclx PC Datalog - 2023-05-14 8;46;07 pm.llgx

[Adamw]

1 hour ago, traingeek2000 said:

but with a timing light I verified 245deg offset compared to the ~205 that most users had posted online.

Neither is correct I woiuld say, everyone I have started is very close to 0 offset. 

[traingeek2000]

I was going off of this response of yours and some others with similar numbers, but another search on this forum finds posts suggesting ~0 offset. Was ignition strategy for JZ VVTi changed between G4+ and G4X? Aside from that, everything else look good in the start map? 

 

[Adamw]

That post is for a G4, almost nothing in common with a G4X.

[Hodgdon Extreme]

For what it's worth, my 2JZGE-VVTi required a -155* trigger offset. I have an ATI damper, and have checked timing with a light multiple times. ECU is AltezzaLink G4x.

[Adamw]

50 minutes ago, Hodgdon Extreme said:

For what it's worth, my 2JZGE-VVTi required a -155* trigger offset.

That would suggest you are using the wrong trigger mode, possibly the multitooth/missing mode?  The correct trigger mode for this engine is "1JZ VVTi" and the offset should be near zero.   You will have unreliable sync/no start/long startup and sometimes VVT errors if you are trying to use "cam pulse 1X" sync mode with a 3 tooth cam. 

[Hodgdon Extreme]

9 hours ago, Adamw said:

That would suggest you are using the wrong trigger mode, possibly the multitooth/missing mode?  The correct trigger mode for this engine is "1JZ VVTi" and the offset should be near zero.   You will have unreliable sync/no start/long startup and sometimes VVT errors if you are trying to use "cam pulse 1X" sync mode with a 3 tooth cam. 

Don't I feel dumb; but boy am I glad I spoke up in this thread...

You are correct indeed that I have been using multi-tooth/missing trigger mode. Haven't seen any VVT errors, but have noticed some trigger errors here and there.

Until you mentioned it, I hadn't pieced it together that my inconsistent starts were linked to those trigger errors.

I just spent some time with it and noticed when it starts perfect - no trigger errors. When it won't start; but rather just cranks - followed by a big backfire out the exhaust when I quit cranking - trigger errors.

I've tried wildly different start fueling via adjusting engine capacity to 2500cc, 2000cc, 1500cc, 1000cc... sometimes it starts right up, other times just cranks followed by the backfire.

Adjusted my trigger type to 1JZ-VVTi and offset to zero - started perfect 20 times in a row with zero trigger errors with ECT ranging from 130F to 185F.

Thanks for sharing your knowledge!

I didn't have a timing light with me tonight so that needs to get done ASAP. What else in my calibration do you think I need to go back over after making this trigger type change? Arming thresholds? Ignition delay? Knock thresholds? VVTi PID settings?

[Adamw]

Set base timing and redo the VVT cam angle calibration will likely be the only thing needed.

[Hodgdon Extreme]

For educational purposes, can you explain what's happening in the background firmware that caused my inconsistent starting and backfires on account of choosing wrong trigger type?

I had trigger 1 set to 36-2, which I'm pretty sure is correct. I think the issue is in this mode, trigger 2 defaults to single pulse and cannot be changed to 3X... So any time you crank, the ECU has a 1 out of 3 chance of picking up the correct synch tooth on the cam...??

Could I have theoretically made this work right by grinding the other 2 teeth off my camshaft?

I get how that would cause a no-start condition, but I don't understand why that would cause the big backfire. Is it because the  ECU was synching - but doing so in the wrong position and therefore causing wildly incorrect ignition angle?

...I like to fully understand my failures...

[Adamw]

The issue is your sync mode "cam pulse 1x".  It is sometimes mis-syncing, the crank alone only tells the ecu where TDC is, so will be sparking at TDC exhaust stroke instead of TDC compression stroke.  There are two crank revolutions for a 4 stroke engine cycle, with a missing tooth trigger wheel on the crank the ecu can determine crank position within a 360deg window but it doesnt know if the crank is on its first rotation or 2nd rotation.  I dont know off the top of my head what the 1JZ vvti trigger mode uses to sync as there are many different strategies we use, but one example may be a simple tooth count sync.  The ecu will have a fixed position on the crank wheel where it performs its "sync test", this sync point will be somewhere where the ecu can observe something different occur on the cam for each revolution.  You have 3 evenly spaced teeth on your cam so the ECU will do something like check if it received 2 cam teeth or 1 cam tooth over the last crank revolution.  It may also use a cam window sync where it looks for a cam tooth within a given crank angle window, that tooth will be present on one revolution and not on the other.  

[Hodgdon Extreme]

I just wanted to follow up on this again.

Using the correct trigger setting completely fixed my inconsistent starting; and I've not had a backfire since.

I found I needed 6º of trigger offset (extra advance) to get my timing light to match my reference timing.

I found I needed 105 uS of ignition delay to get my timing light to show the same results at 1000rpm and 6000rpm. My default value was 80uS, which was retarding timing about 2-3º at 6000rpm.

For reference, I am using an ATI harmonic balancer and the stock Toyota timing marks on the front cover. I have not verified the angularity accuracy of these parts; I've just been assuming they're correct. Also, the ATI has marks all around the front edge. I put a paint mark on the rear edge of the balancer, even with the 15º mark, and I'm shining the light down the crevice between the front cover and the coolant expansion tank. Using an old Actron roll-back timing light, but rather than trusting the electronics of the light, I set it to 0º and relied on the marks on my ATI and front cover.

Hope this helps somebody else get up and running easier!