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Engine start time

Richard Hill

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Good evening,

I have a 1uzfe VVTi running on a Thunder, which runs great with all the factory features (DBW, ACIS etc).  

However, it is taking quite a few revolutions of the engine from first crank to start.  I have tweaked the fuel for pre-crank prime and crank enrichment and none of them are improving the time to start.

Is this just a symptom of the triggers and the time required to synchronise from the ECU?  I have installed Link ECUs on engines which have started within what seems like one crank rotation.  I would ideally like this engine to start on the first turn (it just sounds nicer when they fire up that quickly to a rock stable idle)


Thanks in advance,



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Given you've got a few good examples try comparing a startup log from a working engine to this one. Compare the time taken from when the voltage drop/start signal kicks in, then when you start seeing rpm, then how long it shows cranking RPM before firing up.

Compared to the good engine, if its a delay in the RPM showing at all, focus on trigger settings (signal level, correct offsets, trigger1 vs 2 offset) etc. Also try swapping it to wasted spark mode and see if this fires up quicker - this doesnt require cam sync so can be an interesting test.

If the time from crank signal to read RPM is roughly the same as a good engine, then its likely your triggers are fine, and you can focus on fuelling amounts, spark timing, injection timing etc.

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5 hours ago, AbbeyMS said:

@Richard Hill  the VVTI position sensor is that also the phase sensor for the motor?

Does the car start faster sometimes than other times?

The engine has a crank sensor (Trig1), a cam sensor (Trig2) and 2 VVT sensors (inlet) one for bank1 (DI1) and one for bank2 (DI2).  I am using the standard 1uz VVT trigger pattern, engine is bog standard.

It has once started a lot quicker, but most of the time requires 5 or 6 crank revolutions to start.

As CJ suggested, I will have a look at the logs and do some measurements of the time to trigs active from first crank.

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FYI, the sync strategy on the 1UZVVT trigger mode is just like our generic multi-tooth/missing modes - The ecu needs to see the cam tooth before it can sync.  So worst case will be it needs 720deg crank rotation to sync, most of the time it will be a good bit quicker than that.

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