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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Tue Jul 10, 2018 11:24 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2900
Location: Norn Iron
ECU Model: No ECU
Rob Stevens wrote:
I don't think a +ve or -ve spark is going to make much odds this side of an F1 team :) :)


Unless it is causing interference as most engines are not firing 2 plugs in the same cylinder....because most engines do not have 2 plugs in the same cylinder.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 5:09 am 
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Joined: Mon May 10, 2010 5:09 pm
Posts: 214
ECU Model: S80 Pro
Firmware Version: 61
I'm guessing that the ford coil pack is a wasted spark unit? ie the spark travels from one side of the coil to a spark plug through the engine to the other spark plug back to the coil? this is how the wasted spark coils I have used before have worked....

if this is the case having 2 coils firing at the same time might be causing a change in potential across the engine?


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 6:00 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2900
Location: Norn Iron
ECU Model: No ECU
How close are the 2 plugs together ?

What about a modern coilpack where ones mounts on the plug and has a flying lead for the other plug of it's firing pair ?

A few cars use that setup...then you'd have 1 dedicated ecu output to each cylinder ( coils would need to have integral ignitors probably )

Or go down the route of 8 coils, although that would add costs.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 6:01 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 852
ECU Model: S100 Pro
OOh interesting idea. so to simply check just change the spark offset to something other than 0.0 but I can't honestly see it being anything like that.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 6:04 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 852
ECU Model: S100 Pro
he only has S60 so can only do 4 coils and until you know better id like to try different spark offsets. So he has the best setup for this now. As ever I'm sure its a simple fix.
Can you post your map up?


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 12:51 pm 
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Joined: Sun Jan 27, 2013 6:08 pm
Posts: 262
ECU Model: S60 Pro
Firmware Version: 29
I've seen a few variations of 8 plug heads on 4 pot bike engines - they ain't a problem! If the regular twin output bike coil is 3 ohm you replace that with two 0.7 ohm twin output coils wired parallel, I believe, and they worked - it needed the correct ignition amp due to the low resistance coils but no reason two 3 ohm types wouldn't work equally well with regular ignition.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Wed Jul 11, 2018 2:05 pm 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2900
Location: Norn Iron
ECU Model: No ECU
Rob Stevens wrote:
he only has S60 so can only do 4 coils and until you know better id like to try different spark offsets. So he has the best setup for this now. As ever I'm sure its a simple fix.
Can you post your map up?



You could connect half a dozen coils with built in ignitors to each ecu output if you wanted.

You could not connect half a dozen inductive coils though.

So he could easily run 8 coils of the correct type, with 2 wired to each ecu output.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Thu Jul 12, 2018 2:35 am 
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Joined: Tue Aug 02, 2011 2:05 am
Posts: 33
Location: The Netherlands
ECU Model: S60 Pro
Firmware Version: 63
Rob Stevens wrote:
OOh interesting idea. so to simply check just change the spark offset to something other than 0.0 but I can't honestly see it being anything like that.


Update: I actually just entered this idea into the ecu and gave in 2 degrees off-set: problem gone! :shock: :mrgreen:

Did 2 perfect full WOT runs on a 'closed of piece of highway and she was flying at just 0,65 bar boost!
I am a little afraid though that off-set might jsut negate the purpose of twin-spark all-together. Depending on how much off-set you use of course, but alas I can't see into the combustion process...

So, what does this tell us? S60 can't handle 2 high output coils in twin-spark mode with zero off-set?
Alex, did anybody you know of, tried this before succesfully on a boosted application?

_________________
11.06 @ 124.5 mph
'74 VW Beetle turbo S60pro


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Thu Jul 12, 2018 5:04 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2900
Location: Norn Iron
ECU Model: No ECU
I would doubt they are particularly high output coils compared to some stuff.

Both coils are still charging at the same time, the firing instant is just slightly different.

Again, I would ensure both coils are mirrored exactly in terms of wiring and firing, both plugs for1 cyl 1 connected exactly the same so they're both firing on the same polarity.

And if they are currently like that...flip them around so they arent and one is a pos and other neg firing

How low can you make the offset before the problem appears ?


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Thu Jul 12, 2018 6:48 am 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1116
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
It's not an ECU issue. We have loads of 4 cylinder cars running 4 COP in wasted spark mode.

Some maths will help.
Assuming you're revving to 7200 RPM, that's 120 revs per second, or one revolution every 8.3ms.
You've moved the second spark plug firing point 2 degrees, which is approximately 42 microseconds later (8.3ms / 180).
Dwell time is 3ms.
Even if you halve that to 3600 rpm, your coils are still charging at pretty much the same time.

It's simply a function of the combustion event.


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