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Pinto Ignition & Dwell


Thrashed

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Hi all

 

I need some education!

 

I have a pinto running an FR32 cam and raised compression with ported head and a few other tweeks.

 

Running the ignition i have the accuspark stealth blackbox. The dizzy is a accuspark and is locked out with no vacuum advance.

 

On our run out yesterday, it was very difficult to get started and was what felt like misfiring.

 

At the end of the run at Richys we pulled the plugs and they were covered in a black velvety soot. From my research, this could be fueling, but i done think so as on the rolling road it had perfect afr readings, so other possible cause is ignition timing.

 

I swapped the plugs for apr7fs and have them gapped to just under 1mm. As per previous post, the standard apr6fs should be 0.7mm, so should the gap of about 0.9mm be to big?

 

This is the `map' i have on the blackbox at present. Does this look right?

 

I understand the basics of what ignition does and but that the dwell does and how/ why i have no understanding

 

What i believe is that the number in the box under dwell next to the rpm are the percentage numbers for the coil draw? i have no idea if these are even close as i have not been able to find any information on what coil draw a pinto should have. The software limits the combined advance and dwell to 90, but again i have no idea what 90 means?

 

Can anyone explain this in a dummys guide for me.

 

Thanks

 

Steve

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Having done some further testing i have checked the resistance of the coil.

 

I have the intermotor 11330 coil, which is just a standard coil. The resistance reading between + and - is 1.3 ohms, but the haynes manual says it should be 0.72-0.88ohms.

 

The secondard windings are reading at 6810, which accord to Haynes should be 4500 - 7000ohm, so right at the top end.

 

Am i reading this right and the coil is duff or am i worrying about nothing?

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Measuring resistance below about 5 ohms realy needs a 4 wire meter to eliminate lead and contact resistence.

With a normal 2 wire meter you can guess lead resistance by reading with the leads shorted and taking that reading from the coil reading but you are still approximate.

With the points closed the current in the primary (low voltageside) of the coil is building up, when the points open this causes an abrupt change in the current and produces a high voltage in the secondary which breaks down the gas in tthe spark plug gap producing a spark and ignition. A bit simplified and no mention of the compromises required to make the whole thing work.

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Measuring resistance below about 5 ohms realy needs a 4 wire meter to eliminate lead and contact resistence.

With a normal 2 wire meter you can guess lead resistance by reading with the leads shorted and taking that reading from the coil reading but you are still approximate.

With the points closed the current in the primary (low voltageside) of the coil is building up, when the points open this causes an abrupt change in the current and produces a high voltage in the secondary which breaks down the gas in tthe spark plug gap producing a spark and ignition. A bit simplified and no mention of the compromises required to make the whole thing work.

Thanks Ian

 

The resistance on the leads is 0.6ohms, so if my reading is 1.3, does this mean my read coil reading is 0.7ohms?

 

Thanks for the explanation on points. starting to make sense as what is meant to happen,

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Has an Accuspark got points?

No, but trying to understand what the box is trying to do.

 

I now understand that the car has 90' of dwell per cylinder. the next part to understand is how long should the points be closed/ opened during the 90' cycle? obviously 45' would be 50%, which from my map starts to make sense on how long the dwell is but i dont understand if this is correct or ideal?

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If you don't have points dwel is imaterial.

The idea of dwel is to give time for the resistance to breakdown and jump the gap.

Electronic ignition fires the spark accurately when you need it so you don't need to allow for the slack in a points system just use the map to fire the spark at the required time

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