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How does dwell timing work for logic level ignition outputs?

 
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William_Irani



Joined: 04 Jan 2018
Posts: 2

PostPosted: Sun Jan 07, 2018 6:43 pm    Post subject: How does dwell timing work for logic level ignition outputs? Reply with quote

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 BIP373. 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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David Ferguson



Joined: 21 Aug 2006
Posts: 57
Location: Paso Robles, CA

PostPosted: Mon Jan 08, 2018 7:43 am    Post subject: Reply with quote

The amount of time the signal is 1 (high) is the dwell time (the time the coil is fluxing), when the signal goes to zero, then ignitor will release the ground going to the coil and the magnetic field will collapse causing a current spike on the secondary and the plug will fire.

Some of the ignitors monitor the dwell time and coil current consumption and apparently can vary the dwell time the coil actually sees. I use the simpler Bosch ignitors (i.e. 211) and control the dwell time directly.
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joe90



Joined: 19 Mar 2013
Posts: 372
Location: under the car

PostPosted: Tue Jan 09, 2018 11:13 pm    Post subject: Reply with quote

You'll get confused for ever by all the marketing BS.
All ignition systems use logic levels, they're all either on or off, high or low.
The marketing people want to confuse everyone, that way they make more sales.
No ignition systems use 5 volt logic for the ignition.

There 's TTL logic...no, not that.
There's CMOS logic....not that either
There's relay - relay logic...not that either.


Most ignition amplifiers make the spark when the coil current stops which is an input of zero volts to the amp from the ECU, as in an earth input.
The coil turns back on when the input voltage rises to about 3 ish volts.

But there's no set rule as it varies with the unit used.

Most (all) ignition amplifiers have inbuilt current limiting for protection.
The dwell part of it normally comes from the ECU but not always.


Rule no 1........coils don't charge.
Capacitors DO charge.
Coils "flux".


It's the fundamental difference between an electric field and a magnetic field.


That's what you should be studying.
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