How does dwell timing work with logic level spark outputs?

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How does dwell timing work with logic level spark outputs?

Postby William_Irani » Sun Jan 07, 2018 6:58 pm

Hi,

I’m in the process of doing an engine conversion, haven’t yet decided on a ECU but have decided the coils I will be using. They are high current coils with no built in drivers (2 wire).

What i’m finding difficult to understand is how dwell timing is controlled when using an external driver like a Bosch 211 or multiple BIP373s. From what I understand, the logic level signal from the ECU is at 1 (+5v) when the coil is charging and switches to 0 (0v) for the coil to fire, events which spaced by the duration of the ignition timing. Am I correct?

What i’m Struggling to understand is where is the capacity in this logic level signal to include information about the dwell timing aswell as ignition timing? I’m rather confused. If anyone can help that would be greatly appreciated.

Thanks in advance.
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Re: How does dwell timing work with logic level spark output

Postby Matt Cramer » Mon Jan 08, 2018 8:13 am

William_Irani wrote:What i’m finding difficult to understand is how dwell timing is controlled when using an external driver like a Bosch 211 or multiple BIP373s. From what I understand, the logic level signal from the ECU is at 1 (+5v) when the coil is charging and switches to 0 (0v) for the coil to fire, events which spaced by the duration of the ignition timing. Am I correct?


Precisely. The dwell time is the difference between the time the signal goes high and the time the signal goes low. It is effectively the pulse width of your ignition signal.
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Re: How does dwell timing work with logic level spark output

Postby elutionsdesign » Tue Jan 09, 2018 6:42 am

And the ignition timing is when the signal goes low. Signal goes low, current stops flowing through the primary, primary collapses into secondary and plug fires.
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Re: How does dwell timing work with logic level spark output

Postby jsmcortina » Wed Jan 10, 2018 4:29 am

Is the OP perhaps thinking of a "dwell meter" where dwell is reported in degrees? That representation doesn't apply to EFI controlled ignition coils.
For inductive coils at a given voltage, the required dwell is measured in milliseconds as the other posters have mentioned.

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