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 Post subject: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 5:00 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
Hi all,

I am experiencing very annoying misfires under (low) boost when the engine is run at twin-spark mode. Boost is just 0,65 ar (10psi-ish).
With one coil unplugged, no misfires at all. Half throttle and even less boost it goes through the revs ok, but WOT and "full" boost is impossible :cry:

Dwell is 3500ms (should be well enough).
One coil supplies the upper plugs, the other one the lower 4 plugs in each cylinder (boxer 4-cyl engine)
Coils are the red MSD replacement Ford Zetec coils.
Wires are MSD 8,5mm pro-thingies ($$)
NGK 7-heat grade plugs are at 0,60mm gap.

I have tried resitor plugs and now regular non-resitor plugs with no difference.
Wires run free, VR sensor cable clears wires with enough space as well.

Diagnostic looks good, not a lot of crank errors (30 or so) and logging of advance and lambda showes nothing unusual at the misfires moment (loud bangs in the exhaust, whole car shakes when that happens).

I am starting to think that the ecu might not supply enough power for these coils?
Is that possible?

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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: Mon Jul 09, 2018 5:51 am 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2901
Location: Norn Iron
ECU Model: No ECU
So this engine has 2 plugs per cylinder ?

Exactly which coils and how are they wired ? Internal or external ignitors ?


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 7:44 am 
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Joined: Sun Jan 27, 2013 6:08 pm
Posts: 262
ECU Model: S60 Pro
Firmware Version: 29
I suspect there are two Zetec coil packs (instead of the normal one?) If so, and wired parallel to the ECU coil outputs the circuit resistance will halve and so the amperage will double. This may indeed be causing the outputs to overload.
Coil packs may not be the best option for twin plug / cylinder - better to use 4No Twin tower bike coils ?


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 8:19 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 853
ECU Model: S100 Pro
Are you using all the 4 coil outputs? Has it ever run properly?
I think the top plugs should be to O/P 1&2 the 2nd coil to O/P 3&4 is that how you have it? That will give you control over the 2nd spark timing.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 8:25 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
stevieturbo wrote:
So this engine has 2 plugs per cylinder ?

Exactly which coils and how are they wired ? Internal or external ignitors ?

Yes, two plugs per cylinder: twin spark.

I use two of these:
Image

They are rated at about 40K Volt each.. too much for the S60?

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11.06 @ 124.5 mph
'74 VW Beetle turbo S60pro


Last edited by Airspeed on Mon Jul 09, 2018 8:31 am, edited 1 time in total.

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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 8:29 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:
Are you using all the 4 coil outputs? Has it ever run properly?
I think the top plugs should be to O/P 1&2 the 2nd coil to O/P 3&4 is that how you have it? That will give you control over the 2nd spark timing.

Thats exactly how it is wired!

It runs perfectly without (too much) boost up to about 5K RPM, where it harshly misfires at just 10psi.. :?:
It is weird that 'full' boost is already there at 4-5K RPM, but just around 5K RPM it seems the neccesary power to keep the sparks coming, are gone..

This what the engine looks like, to get an idea, you can just see the second plug on the underside (red plug wire):
Image

Besides twin spark, its also equal length twin-scroll (EFR7670) and twin-wastegated (Tial MVR) :lol:

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11.06 @ 124.5 mph
'74 VW Beetle turbo S60pro


Last edited by Airspeed on Mon Jul 09, 2018 8:43 am, edited 1 time in total.

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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 8:38 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 853
ECU Model: S100 Pro
Make sure you have a good 12v to the coils and try perhaps reducing plug gaps a bit?
If using the 3d 2nd spark map make sure there isn't anything silly in there.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 8:46 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:
Make sure you have a good 12v to the coils and try perhaps reducing plug gaps a bit?

Yeah, as long as you guys haven't heard of this problem before and Alex doesn't say I am running too much coil, that will be my next step(s), even thought 12V are relatively thick wires.
Quote:
If using the 3d 2nd spark map make sure there isn't anything silly in there.

I didn't even know there was one?
I have just set second plug off-set to zero in 'general engine settings' and thought that was it?
Could it be that there IS s/th silly there as default? Hmm? will check tonite.
Just to be sure: where is this second map located in the program?

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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: Mon Jul 09, 2018 11:10 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 853
ECU Model: S100 Pro
2nd map is map 2, but you have to check that in 'General Engine Settings' at the bottom.


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 Post subject: Re: Twin-spark misfires under boost - ECU power?
PostPosted: Mon Jul 09, 2018 3:54 pm 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2901
Location: Norn Iron
ECU Model: No ECU
So even with only 1 coil and 1 plug/cyl in use, it still does not rev or perform correctly ?

Are you sure tuning is good, and it isnt crazy rich or something ?

What dwell time are you running on the coil ?

Can you try an OEM Ford coil ?

Plug gap ?

All engine grounds good ? Likewise any power feeds to the coil ?


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