VAG active COP weak spark -SOLVED-

[Ignitec]

I have wired 115c VAG COPs on fiat 20vt engine and I have pretty weak spark on plugs, causing misfire in boost, but depends on dwell. More dwell - less misfires, but for 180kPa I need more than 3ms. These should be older type COPs, so I didn't add parallel resistor. Newer type of COPs tried today, no spark at all (thus no parallel resistor). Wold it help if I add 500 Ohm resistors in parallel on older COPs to get stronger spark? Stepper out is out of question, because of 5cyl engine that cannot run wasted spark.

Thank you,
Ninoslav

[rob@vems.co.uk]

What's wrong with running more than 3ms?

[Ignitec]

Isn't that too much? I'd like to run 250 kPa or more, and for example 5ms looks a bit insane for me... Can it hurt anybody if I try to add parallel resistors to lower resistance between vems and COPs? Could I get better spark that way?
Now spark isn't strong enough for gap of 1.2mm out of engine with 2ms dwell...

[mattias]

What ignition plugs do you run and what plug gap ?

NGK BCR7ES with 0.5-0.6 mm gap has worked well for me with AAN.

I tried 115R coils on one Audi, works ok with 2 ms dwell - any more and they break (over-heat) or mis-fire.

[Pet]

I've measured dwell on 115R and 3ms dwell gives around 13.5A/12V on primary side and pretty nice strong spark!! Source of the signal was 0-5V/25mA through 165R (2x330R in parallel). 330R was too high resistance to ignite the spark.
Anyway the COP was quite hot after a few minutes of testing.... When you want to use it in wasted spark mode (2x more sparks), AFAIK there is good idea to lower dwell to 1.5ms (due COP reliability)

[Ignitec]

I've tried NGK BKR8E, BCR8ES and many others, with gaps from 0.5 to 1.2mm. Maybe 115c coils are not good for boost? I think they are from some 4.2l engine. Is there any chance to get anything better with resistors?
Today I'll try one new coil (115r i think I have) with resistor to visually compare strenght of spark.

[lugnuts]

I have used the 4 wire VW COP coils on other brand ECU for years now. I have several cars making 500-600-700 and even 811 wheel HP at 40+ psi of boost with these coils. I use slightly less than 3ms dwell, and .020" spark gap with NGK non extended tip plugs.
As far as minimum dwell they will run at idle to as low as .5ms.

With the VEMS I have never got the cop coils to work with the logic level ignition outputs, I believe my spec was 255 ohms but that did not work so I used stepper.

Is it possible to use IGBT outputs pulled up to 12v for these coils?

[GintsK]

lugnuts, didn't you get any spark? Or spark was weak?

What signal level OE ECU use  for these coils?

Problem is VAG coils inside has pulldown resistor. In any case if feed 5V to the coil through any resistor there is something lower than 5v at the end.

Gints

[Ignitec]

Today I tried to run coupe with a pair of 500Ohm resistors. It's much better! Now I have pretty strong spark with 1.8ms dwell. Tomorrow we'll see whats going on in boost

On daylight it almost wasn't possible to see spark with 500ohm, and now it's very strong and clearly visible even in direct sunlight. Thanks to all!

[Ignitec]

No problems even in 250kPa with 2ms dwell! 

[altz1]

How did you connected these resistors? How many of them? Every coil has one? Sorry for dumb questions.

[Ignitec]

Sorry for late response!

I soldered resistors in paralel with existing ones, there are empty solder pads on board, top side, near IGBTs.

Every channel have one resistor, and one empty solder pad, just before IGBT gate. You just take one 500ohm SMD per channel and solder it on pads.