Important note re VAG COP units

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elaw
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Important note re VAG COP units

Post by elaw »

I recently got my hands on some VAG COP (coil-on-plug) coils and was fooling around with them on the bench - I was using the pinout shown in the MS/Extra manual here: http://www.msextra.com/doc/ms2extra/MS2 ... m#copsetup. They seemed to be exhibiting some strange behavior, so I did some investigating. I found a diagram on the web that showed a different pinout from what's in the Extra manual, and I think at least the coils I'm using have this alternate pinout.

The MS manual references VAG partnumber 06B 905 115 and shows the pinout as 1=+12, 2=signal ground, 3=trigger signal, and 4=power ground.

My coils, which are partnumber 077 905 115Q, the pinout appears to match the one given on the other site where 1=+12, 2=power and signal ground, 3=trigger input, and pin 4 is connected to the ground side of the HT winding, along with the metal shield on the exterior of the coil.

There are two reasons why I believe the 2nd pinout is the correct one for these coils: first, using an ohmmeter there is no continuity at all between pins 2 and 4. However pin 4 measures 0 ohms to the outer shield, and a few tens of K to the HV output terminal. And second, if you hook up an ammeter, the current flowing into pin 1 when the coil is energized matches the current coming out of pin 2, where pin 4 reads 0 current. Also hooking a floating +12 supply to pins 1 and 4 does not make the coil work, but moving the ground to pin 2 does make it work.

So if you're using this type of coil, I'd highly recommend NOT connecting pin 2 directly to the Megasquirt signal ground. Doing so will make all the current flowing through the coils go into that ground and most likely cause noise problems. I'd suggest instead grounding pin 2 of each coil to the block near where the Megasquirt is grounded.

Indicentally these coils also have a 390-ohm input impedance, so you need to use the "5V PNP drive" circuit with them.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking

Be alert! America needs more lerts.
jsmcortina
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Re: Important note re VAG COP units

Post by jsmcortina »

Good info. Any chance you (or someone else) could repeat this test with the exact coils shown in the manual to confirm if the manual is in error for all these coils ?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
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elaw
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Re: Important note re VAG COP units

Post by elaw »

Unfortunately I can't... as you may or may not know there are a *ton* of different VAG COP coils - not just different units for different engines, but also revisions upon revisions as they've had many reliability problems over the years. Even the coils I have are outdated - but they were $5.00 each (used ) so I just couldn't say "no"! :lol: But they're the only VAG coils I have, or have access to.

Except... for testing and comparison, I do have another coil on order, a brand-new 07K 905 715F. That one is a current revision and is also pretty reasonably priced ($20.00), when I test it I'll post my results as it may have appeal for other users.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking

Be alert! America needs more lerts.
racingmini_mtl
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Re: Important note re VAG COP units

Post by racingmini_mtl »

Wouldn't the solution be to recommend grounding pins 2 and 4 to the block for all of them?

Jean
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savagerocco
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Re: Important note re VAG COP units

Post by savagerocco »

I can confirm issues on the wasted spark Audi I built. Wouldn't run with the 2 terminal hooked up to signal return. Major noise. I ended up grounding to the body. Problem solved. Wondered about that. But my car running the same coils seems fine. Go figure. Might try moving the grounds or at least see where I grounded them
Last edited by savagerocco on Mon Jan 02, 2012 8:31 pm, edited 1 time in total.
Brent Savage
life behind the zion curtain
90 audi RS2 20VTQ 6sp MS3, MSX COP and Sequential and now MAF
87 Scirocco 2.0 ABA 16v EIP tubular cast MSII COP
86 Audi 4K20VTQ MSII
90 Audi 90 sedan 3.6l DOHC V8TT (project car)
89 VW cabbie (bitch basket) 2.0 ABA Turbo MSII
jsmcortina
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Re: Important note re VAG COP units

Post by jsmcortina »

I've updated the MS2 and MS3 manuals to show this change.

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

My Success story: http://www.msextra.com/forums/viewtopic ... 04&t=34277
MSEXTRA documentation at: http://www.msextra.com/doc/index.html
New users, please read the "Forum Help Page".
elaw
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Re: Important note re VAG COP units

Post by elaw »

racingmini_mtl wrote:Wouldn't the solution be to recommend grounding pins 2 and 4 to the block for all of them?

Jean
That makes sense to me!

The funny thing with these coils is, as long as it's properly connected to a spark plug pin 4 really does nothing. The outside shield has "fingers" that contact the spark plug shell to provide a ground. Although I'm sure it's good to have the HT circuit have a "backup" ground, that's not the kind of thing you want to leave floating.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking

Be alert! America needs more lerts.
elaw
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Re: Important note re VAG COP units

Post by elaw »

Hey just to beat this nearly-dead horse a little more... my wife recently got an Audi with the 1.8t engine that uses VAG COP modules. I was poking around the wiring diagrams and found this, that shows the internal wiring of the coils:
Image1.png
Per that diagram, pin 4 is the ground for the HT circuit, and pin 2 is a ground (both signal and power) for the driver in the primary circuit. The OE wiring has pin 4 of each coil grounded to the head, and pin 2 of each grounded to the chassis. I think grounding both to the head should work (and does on my car), but you definitely would NOT want to use pin 2 as a "signal ground" connected directly to the Megasquirt.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking

Be alert! America needs more lerts.
savagerocco
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Re: Important note re VAG COP units

Post by savagerocco »

I can confirm that grounding 2 to megasquirt isn't a good idea..... chassis ground work much better!
Brent Savage
life behind the zion curtain
90 audi RS2 20VTQ 6sp MS3, MSX COP and Sequential and now MAF
87 Scirocco 2.0 ABA 16v EIP tubular cast MSII COP
86 Audi 4K20VTQ MSII
90 Audi 90 sedan 3.6l DOHC V8TT (project car)
89 VW cabbie (bitch basket) 2.0 ABA Turbo MSII
weeblebiker
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Re: Important note re VAG COP units

Post by weeblebiker »

I have both grounds connected to the head aprox 6" apart and seems to be working well.
v2.2 box, ms2, dual wheel, sequential ignition, staged injection, boost control, maf
'87 VW scirocco, 2L16V, TD0-14T turbo, itbs
elaw
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Re: Important note re VAG COP units

Post by elaw »

Same here. Pin 2 grounds under one valve cover bolt, pin 4 grounds under another.
Eric Law
1990 Audi 80 quattro with AAN turbo engine: happily running on MS3+MS3X
2012 Audi A4 quattro, desperately in need of tweaking

Be alert! America needs more lerts.
16vboost
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Re: Important note re VAG COP units

Post by 16vboost »

I have the VAG 06E 905 115 E COPs and I have bad noise issues. I ground pins 4 and 2 at the head, but pin 2 is on the same bolt that my MS grounds to. Moving the pin 2 ground to he bolt where pin 4 is grounded gives the same results. My only workaround so far has been to solder a capacitor in the COP harness between +12V and pin 4 ground. But this capacitor doesn't live long :(

-Alex
savagerocco
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Re: Important note re VAG COP units

Post by savagerocco »

Are you using resistor plugs? Have you removed the metal shield that goes around the spark plug? That is the return for the secondary spark.
Brent Savage
life behind the zion curtain
90 audi RS2 20VTQ 6sp MS3, MSX COP and Sequential and now MAF
87 Scirocco 2.0 ABA 16v EIP tubular cast MSII COP
86 Audi 4K20VTQ MSII
90 Audi 90 sedan 3.6l DOHC V8TT (project car)
89 VW cabbie (bitch basket) 2.0 ABA Turbo MSII
16vboost
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Joined: Thu Apr 22, 2010 9:10 pm
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Re: Important note re VAG COP units

Post by 16vboost »

I'm using NGK BKR7E plugs which I believe are resistor plugs. The metal shield around the coil pack is there and makes a nice scraping engagement with the plug hex when installing them.

I just checked one of my COPs and I have zero resistance between pin 4 and the shield and open between pins 2 and 4.
savagerocco
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Re: Important note re VAG COP units

Post by savagerocco »

I know resistor are very necessary! I think my coil packs are grounded on a bus bar that shares my megasquirt grounds. I'll have to look at the wiring.
Brent Savage
life behind the zion curtain
90 audi RS2 20VTQ 6sp MS3, MSX COP and Sequential and now MAF
87 Scirocco 2.0 ABA 16v EIP tubular cast MSII COP
86 Audi 4K20VTQ MSII
90 Audi 90 sedan 3.6l DOHC V8TT (project car)
89 VW cabbie (bitch basket) 2.0 ABA Turbo MSII
16vboost
Master MS/Extra'er
Posts: 478
Joined: Thu Apr 22, 2010 9:10 pm
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Re: Important note re VAG COP units

Post by 16vboost »

Resistor plugs? Or resistors between grounds? I measured the resistance across the electrode of a plug and its 4.5k ohm.
savagerocco
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Re: Important note re VAG COP units

Post by savagerocco »

Sorry resistor plugs. Don't have any noise caps on my setup. What kind of issues are you having?
Brent Savage
life behind the zion curtain
90 audi RS2 20VTQ 6sp MS3, MSX COP and Sequential and now MAF
87 Scirocco 2.0 ABA 16v EIP tubular cast MSII COP
86 Audi 4K20VTQ MSII
90 Audi 90 sedan 3.6l DOHC V8TT (project car)
89 VW cabbie (bitch basket) 2.0 ABA Turbo MSII
16vboost
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Joined: Thu Apr 22, 2010 9:10 pm
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Re: Important note re VAG COP units

Post by 16vboost »

Without the cap, I get wild fluctuations in AFR (in MS and on my innovate gauge) and sync loss. This happens at idle and up without the cap. With the cap, everything seems to go away but I will log a few sync losses during a 30 minute drive. At the track, something changed and high load situations caused sync loss. New capacitors after that event fixed the sync loss again, but only for 30 minutes. Once again, high boost, high rpm causes sync loss. Removing the caps results in not even being able to idle without constant sync loss.

I'm convinced that this is a grounding issue. The same trigger wheel / hall sensor setup worked flawlessly with the old distributor and bip373.
16vboost
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Re: Important note re VAG COP units

Post by 16vboost »

Update: I moved the pin 2 ground from the head to the chassis on a bolt that does not share a ground with any harness. I still have the old capacitors installed which may be damaged, but so far, no sync loss :yeah!:

So my take on the matter is ground pin 2 to the chassis on a bolt not shared with any other grounds. Ground pin 4 at the head. Add capacitors between pin 1 and 4 to taste. I'll also update in my other thread.http://www.msextra.com/forums/viewtopic ... 01&t=57615

Now I need to get to the track for the ultimate challenge.

-Alex
weeblebiker
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Re: Important note re VAG COP units

Post by weeblebiker »

that's still a wierd issue.
your not doing anything funky like not running an alternator or have the battery in the trunk with paired pos and neg cables up to the engine bay are you?
v2.2 box, ms2, dual wheel, sequential ignition, staged injection, boost control, maf
'87 VW scirocco, 2L16V, TD0-14T turbo, itbs
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