Trigger Mode For Mitsubishi 4A91 Engine

[helijohnny]

Hello,I am try to run fury G4+ with a 4A91 Engine,the engine have 60-2 crank wheel,and 4 cam teeth at inlet cam(VVT Cam 2 wide 2 narrow),i try to use the missing teeth mode + cam level sync mode to stared the engine,but the timing light was diff crazy when idle,and pops in the exhaust.

Today i found the cam and trigger looks like the alloytec II VVT,i try to use this mode,but no changes,any one can help?

Thanks~~

EngineRun But No Stable RPM ROC.llg Trigger Scope LingYue V3 4A91.llg LingYueV3-StartFile-AlloytecIIMode.pclr LingYueV3-StartFile-MissteethMode.pclr

[Adamw]

Cam level sync should work fine with this engine provided the inlet cam can only move in the advance direction.  Your log "EngineRun But No Stable RPM ROC" looks ok to me, no sign of trigger problems in that.  

 

7 hours ago, helijohnny said:

but the timing light was diff crazy when idle

Can you confirm, if the "set base timing" screen is open is the timing stable? Does the timing mark stay aligned if you rev the engine higher - to say 4000RPM?

[helijohnny]

Hi Adamw，Thanks for your reply.

Yes , no trigger erron shown but in the log engine spped ROC,the engine speed look like stable,but it shown -1050rpm / +1980rpm engine spped ROC,with the timing diff and exhaust pops。

it is also not stable in the "set base timing" screen open,the "crazy diff" like radom diff with 10~15deg ignition timing.

i think it run better when rpm rev higher,less pops than low rpm area.

[Adamw]

I think the erratic engine speed ROC is due to the engine running badly, it is not the cause of the engine running badly.  

 

3 hours ago, helijohnny said:

i think it run better when rpm rev higher,less pops than low rpm area.

I wanted to know if the timing mark moves in the advance direction or retard direction when RPM is increased.  One explanation for the problem you have could be the coil triggering off the wrong dwell edge, so this would confirm.   

Do you have access to a standalone oscilloscope with 2 channels or more?

 

From your data so far I dont see any trigger problem and the ecu would be outputting an ignition signal at a constant fixed crankshaft angle when the timing is locked, so there must be some other issue causing the spark timing to be inconsistent. 

Has the triggers on this engine been modified?  All data I can find for the 4A91 shows 36-2-1 on the crank and 6 teeth on the cam like this:

[helijohnny]

1 hour ago, Adamw said:

I think the erratic engine speed ROC is due to the engine running badly, it is not the cause of the engine running badly.  

 

I wanted to know if the timing mark moves in the advance direction or retard direction when RPM is increased.  One explanation for the problem you have could be the coil triggering off the wrong dwell edge, so this would confirm.   

Do you have access to a standalone oscilloscope with 2 channels or more?

 

From your data so far I dont see any trigger problem and the ecu would be outputting an ignition signal at a constant fixed crankshaft angle when the timing is locked, so there must be some other issue causing the spark timing to be inconsistent. 

Has the triggers on this engine been modified?  All data I can find for the 4A91 shows 36-2-1 on the crank and 6 teeth on the cam like this:

the timing mark moves to the retard direction and back again,in stable rpm,it's like i keep the engine run in 2000rpm ,and timing lock mode the timing just move +20 ~ +5 deg something like this.

i did not have 2 2channels oscilloscope at now ,but i can try to get one.

i run the engine today and i can saw the trigger error was show today but even with the trigger error the trigger scope shown normal？

i think it is a chinese 4A91? it run with a bosch ecu in stock

Trigger Scope LingYue V3 4A91 Trigger ERROR RPM.llg Trigger ERROR 4 LingYue V3 4A91.llg

[Adamw]

3 hours ago, helijohnny said:

i run the engine today and i can saw the trigger error was show today but even with the trigger error the trigger scope shown normal？

This is because you have now changed your trigger 1 edge to rising, it needs to be falling for this type of crank sensor.  The multitooth/missing map that you attached earlier was set to falling which is correct.   

 

[helijohnny]

6 minutes ago, Adamw said:

This is because you have now changed your trigger 1 edge to rising, it needs to be falling for this type of crank sensor.  The multitooth/missing map that you attached earlier was set to falling which is correct.   

 

OK I will try to set trig1 to falling，the dwell time gose to 0 also by the trigger error right？

so what should i do next step？maybe the missfire issue by the ignition coil setting？

[Adamw]

46 minutes ago, helijohnny said:

the dwell time gose to 0 also by the trigger error right？

Yes, the spacing between the rising edges in the missing tooth area get stretched out, this will mess up the crank position calculation so it has to shorten dwell to correct it.  

Falling edge gap width is 3 x tooth spacing:

 

With rising edge the last tooth width is longer and the gap is shorter:

[helijohnny]

1 hour ago, Adamw said:

Falling edge gap width is 3 x tooth spacing:

Thanks for your explain,now i know how the trigger edge working super clean.

So first step i need change the Trigger 1 edge to falling.

and 

the cam level sync mode need 1 crank missing in cam level low,and 1 crank missing in cam level high.

i check my trigger scope again and i found the when engine run faster the cam edge will very close to the missing edge can it cause problem？

 

if this not next step i shoud use a oscilloscope to check the relationship between crank and ignition out put？

[helijohnny]

On 6/12/2023 at 1:13 PM, Adamw said:

One explanation for the problem you have could be the coil triggering off the wrong dwell edge, so this would confirm.   

i found the problem today,my coil was 2Pin and driver by 12V,fury look likes only can out put 5V? i try to use a 5V coil and try to set the base timing

the timing light flash stable now. i will try to add a ingiter to drive the 12v coil than i think the engine will run normal.

anyway,thanks for your help adam,learned many things from you in this time

[Adamw]

On 6/12/2023 at 5:13 PM, Adamw said:

One explanation for the problem you have could be the coil triggering off the wrong dwell edge, so this would confirm.   

I said this earlier, it would have been helpful to mention that it doesnt have factory coils.  The factory coils have built-in ignitors.  

[helijohnny]

On 6/13/2023 at 4:14 PM, Adamw said:

I said this earlier, it would have been helpful to mention that it doesnt have factory coils.  The factory coils have built-in ignitors.  

i change my coil to a L15B stock coil , it has built-in igniter,the engine run nice now!

Thank's for your help!