[s-cars] 1.8Tcoil pack symptoms

[John Tilden]

Hi Paul,
Well, that makes sense!
So why me and not everyone else?
I do have a chip in the car, but I doubt that the dwell time was changed any
differently than anyone elses if at all.
Timing yes, dwell why?
But I appreciate your ideas especially since the coil/core is significantly
different from the original.


Hope you don't mind me forwarding your post to the list.

Javad, Any comments or thoughts?
How about a new chip to modify the dwell if required?
My coils get very hot, but I thought it was from the proximity to the valve
cover (like inside!).

John

John Tilden
Tilden Consulting Services
2820 164th Ave N.E.
Bellevue WA 98008
(425) 881-2895 Office
(206) 240-5318 Mobile
j.n.tilden at comcast.net

----- Original Message ----- 
From: "Paul Gailus" <gailus at mindspring.com>
To: "John Tilden" <j.n.tilden at comcast.net>
Sent: Thursday, June 01, 2006 6:37 PM
Subject: Re: [s-cars] 1.8Tcoil pack symptoms


> John,
>
> I'm guessing that your coils could be getting hotter because
> the drive signal from the AAN ECU probably has a higher
> dwell time than the signal from a 1.8T ECU.
>
> Most pencil coils like the 1.8T ones have a lower inductance than our
> OEM coils which use the traditional E-I core lamination format.
> So because V=LdI/dt, the dwell time needed for the 1.8T coils
> to ramp up to full current is probably smaller.
> I'm guessing that it's in the 1 to 2msec range vs. about 3msec for
> our OEM coils. It would be interesting if someone could verify this
> by measuring the drive signal from the ECU on a 1.8T car.
>
> The 1.8T coils very likely go into current limit once the current
> has ramped up to a preset value (probably about 10 amps or so).
> To achieve this current limit, the voltage drop across the internal pass
> transistor has to increase substantially in order to allow the voltage on
> the coil primary to be correspondingly reduced.
> This will increase the power dissipation on the transistor.
> If someone could put a current probe & scope on the supply line to a 1.8T
> coil conversion, it could be verified whether this behavior is happening.
>
> I'm not sure if the dwell time on the AAN Motronic ECU can be adjusted
> or not. I seem to remember someone mentioning that there may be a
> custom timing chip on the board.
> Alternatively, one could use a monostable circuit and some logic to
> eliminate some of the beginning portion of the ECU pulse
> while leaving the end time of the pulse essentially the same.
> This would reduce the dwell without affecting the timing.
>
> Running the 1.8T coils on something less than full battery voltage
> could also help, but this would require a voltage regulator of some type
> to do it properly.
>
> Regards,
> Paul
>
>
> -----Original Message-----
> >From: John Tilden <j.n.tilden at comcast.net>
> >Sent: Jun 1, 2006 1:20 AM
> >To: s-car-list at audifans.com
> >Subject: [s-cars] 1.8Tcoil pack symptoms
> >
> >My car, after the 1.8 T coil conversion, has been dying after running on
> >warm days,
> >It starts to die at stop lights and as the car slows between shifts and
then
> >finally dies an refuses to start again until it has cooled off.
> >
> >It started doing this immediately after the update, I was/am convinced it
> >has nothing to do with the coils, but my mechanic is convinced it is due
to
> >the coil swap.
> >
> >We replaced both the timing sensors at the flywheel and I got a good week
> >plus out of it before it died again, of course today was the hottest day
in
> >a week in Seattle, you know, 75F!
> >
> >It appears to lose spark, fuel pressure is OK, but no spark until cool
down.
> >
> >I haven't notice the cold start problem that others are reporting.
> >I have removed the Coil cover.
> >
> >Any ideas?
> >
> >John
> >
> >John Tilden
> >1995.5 S6 Avant Europa Blue
> >Bellevue WA
> >j.tilden at verizon.net
> >
> >
> >_______________________________________________
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>
>