going high versus going low vag coil issues

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savagerocco
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going high versus going low vag coil issues

Post by savagerocco »

Ok, I have been running vw/audi coil packs on my car since MS1 days. Originally I had to run an inverter to drive the coils because they use a 5 volt going high to charge the dwell and then fire when the signal goes to 0v. Once I changed over to MS3 I tried driving the coils directly from the msx card but had issues with "drifing timing" where the timing would advance with rpm even when the advance was set to 10 degrees. I swapped back to my coil driver setup and left the coil control in megasquirt to going low.
I figured that there are plenty of people running logic coils by now and they aren't having any issues. So, I took my driver board out and just ran the msx logic output to my coil inputs and swapped from going low to going high. Now here is the strange part. It fired up and ran, and I drove it to the local napa on an errand, it seemed to run ok, but the power was low, like maybe retarded timing.. Once I left and fired the car back up, it barely ran. I ended up having to coast into a gas station and replace my ignition coil driver board and swap back to going low. I didn't change anything else in the sowftware. The only thing I can figure is that maybe base timing changed, i'm really not sure. I would prefer to be able to ditch my extra coil driver board and clean things up, but im not sure what happened.

background. I have 5 pnp transistors that have 1k resistors hooked up to msx spark outputs. i am running sequential cop and have going low as output, standard dwell. the spark signal turns the PNP transistor on and creates a 5volt signal that charges the coil and fires when turned off.
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
elaw
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Re: going high versus going low vag coil issues

Post by elaw »

If you're using the VAG coils with the low-impedance input (a few hundred ohms), you're never going to have happy motoring without a driver circuit - the MS3X card just can't supply enough current to make those coils work properly. AFAIK everyone that's using them successfully is using a PNP driver or something equivalent, and that group includes myself!
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: going high versus going low vag coil issues

Post by savagerocco »

That would make sense. Guess I will have to see what happens with the lower impedance coils
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
dontz125
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Re: going high versus going low vag coil issues

Post by dontz125 »

Take a look at this schematic; this is now basically what is in the manual for this sort of install. Apparently, it works well with VAG COPs.
QuadraMAP Sensor Module -- PWM-to-Stepper Controller -- Dual Coil Driver
Coming soon: OctoMAP Sensor Module
TTR Ignition Systems
savagerocco
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Joined: Thu Oct 20, 2005 11:09 am
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Re: going high versus going low vag coil issues

Post by savagerocco »

I've been running these coils since ms1 days and that is back to 07. My coil driver works well, I just hoped the problem I had with the max card was software and I forgot that the drivers in the msx weren't up to the coils I am using that is what happens when have been doing this so long you forget what you already figured out.
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
savagerocco
Master MS/Extra'er
Posts: 756
Joined: Thu Oct 20, 2005 11:09 am
Location: Ogden UT USA
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Re: going high versus going low vag coil issues

Post by savagerocco »

Those do look slick though. Too bad they only come in even numbers, guess that would leave a spare driver for us 5 cylinder guys.
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
savagerocco
Master MS/Extra'er
Posts: 756
Joined: Thu Oct 20, 2005 11:09 am
Location: Ogden UT USA
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Re: going high versus going low vag coil issues

Post by savagerocco »

I just ordered the tc4427 gate drivers and extra 5volt regulator. I have been experiencing some strange behavior that might just be related to this. I get some knocking at times and other times nothing. I am wondering if my 5volt signal is dropping enough to fire the coil early cause the strange knocking. I had never thought that the signal might drop enough to cause early firing.
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
elaw
Super MS/Extra'er
Posts: 2926
Joined: Fri Oct 16, 2009 6:20 am
Location: Wilmington, MA

Re: going high versus going low vag coil issues

Post by elaw »

Way back when I hooked one of my 077 905 115Q coils to a pulse generator and did some fooling around to see what triggering voltages and dwell they liked.

The "high" / "on" threshold was very high... I can't recall the exact number but they started to do strange things with voltages below about 4.7 or 4.6. That's a much higher threshold than you'd expect - I think a standard TTL input switches around 2.4 volts.

Finicky things, them thar coils! :?
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
Master MS/Extra'er
Posts: 756
Joined: Thu Oct 20, 2005 11:09 am
Location: Ogden UT USA
Contact:

Re: going high versus going low vag coil issues

Post by savagerocco »

That doesn't make sense to have a 5 volt logic that triggers with that high a voltage. But maybe it is where my knocking has been coming from.
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
savagerocco
Master MS/Extra'er
Posts: 756
Joined: Thu Oct 20, 2005 11:09 am
Location: Ogden UT USA
Contact:

Re: going high versus going low vag coil issues

Post by savagerocco »

I got to thinking some of my issues might be dwell/trigger related. The car seemed to run better when cold. I looked in my ignition settings and saw that I had my dwell set to 6ms. I decided to drop that down to 4ms and have been able to run 6 to 7 more degrees timing and have zero knock under boost. I will have to run some logs and see how this hold out but I am hopeful. Still have the gate drivers coming too butane found my problem.
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
savagerocco
Master MS/Extra'er
Posts: 756
Joined: Thu Oct 20, 2005 11:09 am
Location: Ogden UT USA
Contact:

Re: going high versus going low vag coil issues

Post by savagerocco »

Well, after about a week of driving on the new dwell setting I can say that it runs much better. I have almost doubled my ignition advance and knock is almost non existant. My digikey order showed up and apparently I didn't get the tc4427 gate drivers in there for whatever reason, so they are on order again but I don't expect any improvements from them.
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
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