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Hot Start vs Cold Start


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I've been trying to tune my cold start for quite some time. Trying to shave off miliseconds with no luck.

I've analized the hot start vs. cold start and seems that there is a different behavior. 

I do understand that cold start will always require more fuel and will take longer.. 

but.. 

 

When you look at the log, the hot start dwell charge starts at the same time as fuel injection thus an instant start.

With cold-er engine fuel injection starts earlier and 1.1 second later the dwell kics in .. why ??? 

 

 

 

2020-05-30 22_26_38-Greenshot image editor.png

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It cant spark until the trigger has synced so it knows which coil to start dwelling (Sync is usually the point where the RPM jumps up so dwell should jump up at about the same point).  You dont need sync for fuel to be injected so this should happen earlier.  The first crank enrich should happen as soon as it sees the first few crank teeth - so the cold log shows the expected behavior.  1.1 seconds would be a fairly typical sync time (up to 2 crank revolutions). The PC logging has a low priority at start up so I suspect the point where the PW jumps up in the hot log probably isnt very reliable.  

Depending on the trigger sensors you may get some improvement by dropping the arming threshold so it detects teeth at lower speeds.

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