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Time between trigger sync and Inj Pulse

Mario Schneiderbanger

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I’ve been trying to optimize how long it takes for my engine to fire. I’ve attached a log.

03 S2000 F20C all stock.

If you turn on the following parameters:


DI2 - Starter Switch

Crank Enrich

Prime Pulse

Inj Pw

Trigger 1

Trigger 2

You will see at 9.4 seconds my ignition switch goes active and prime pulse does as well. By 9.6 my triggers show active but the injector PW doesn’t show anything till 10.4 seconds. A full second after hitting the starter. ALSO you will see that RPM doesn’t start reading 200rpm until 10.4seconds. Is this normal and is there a way to decrease this because if that’s as good as it gets then that’s fine but if the injectors were to start pulsing right as the triggers arm as I thought they would then the engine would start a whole second faster. Ive been chasing faster starting by working on the Start fueling for a couple days now but Im thinking now that this is as good as it gets.




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This sounds about normal for this engine.

The S2000 has a very basic trigger pattern with just 12 evenly spaced teeth on the crank - there is nothing unique on the crank to identify where TDC is.  The ECU needs to see nearly the full cam revolution to "sync".  There are 3 odd positioned teeth on the cam so the ECU needs to see at least two of the 3 to distinguish where it is.  That means worst case scenario depending on where the engine stopped it could take up to nearly two full crank revolutions before it can fire a spark.  That is potentially about 1-1.5seconds depending on how quickly the starter motor accelerates it from 0 RPM.

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What if i switch to the AP2 trigger wheels? would that help? Photo attached 


I also found a thread where they opted to grind off 2 of the 3 cam trigger teeth to get the same result. Last few posts here: https://www.s2ki.com/forums/s2000-engine-management-231/crank-trigger-wheel-interchange-ap1-ap2-1177340/


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Yes, this is what we call "K20 VTC" trigger mode.  Since it has a unique index tooth on the crank it would need a maximum of about 1 crank revolution to sync.  Im pretty sure it uses hall effect sensors though so it would mean running power wires to the sensors also.

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Adam, would it be plausible to:

- use the ap2 trigger wheels “cam&crank”

- switch to k20 vtec trigger mode

- but keep the trigger type on Reluctor


this eliminates the need to add the additional wiring for the hall sensors.

The only issue that may cause is that the tooth width isn’t optimal for a reluctor at which my next question will be what if i had a custom trigger wheel made with the same tooth width as the ap1 wheel but with the addition of the extra teeth



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