Mark Anderson

With so many parts becoming unavailable I wish the effort was put into making those pieces. We have factory caps for $10 https://shop.928intl.com/Used-Coil-P...27-602-801-00/

ROG100

And over 100 sitting in Germany

dukenukemx

Only $10? Ok I feel like I wasted my time.

928NOOBIE

Primary resistance looks good at 0.5 - 0.6. It's heavy, at 1.88 lbs; over twice as much as the Brazil-made part but when comparing the workmanship and finish and quality of parts used (+ and - terminals are brass) I'm good. Oil filled (you can hear it sloshing around in there).
Going in drivers side. Will report back if it starts....haha

Correct coil fitting

Brass + and - terminals

1.88 lbs. Diameter is smaller, around 2 1/4 inches. I am also going to remove the sticker on outside and fit it with some self-adhesive heat sink. I found some copper that I think is bendy enough and reflective. Am also considering doing heat shield.

The Forgotten On

Have you verified that the dwell time on those are similar to stock coils?

If not you will have to tune it to account for that.

928NOOBIE

I was not able to find the dwell specification for this...I went by the primary resistance;

Primary resist: 0.40 Ohms
Secondary resist: 3.8 Kohms
Primary inductance 3.8 Kohms
Secondary Inductance 15 H
Leakage Inductance: 0.50 mH
Turns Ratio: 54:1

Thoughts?

Bulvot

This post has a spreadsheet you can use to calculate the dwell time: https://rennlist.com/forums/928-foru...esistance.html

Plugging in your #'s, I arrive at a calculated dwell time of 2.82ms at 14v to reach 9 amps. Compared with the factory 2.45ms average (as measured from several coils both new and old).

In reality, I've found the theoretical calculations to be a bit off and I have required a dwell time as high as 4.0ms at 14v (dwell then gets adjusted upward for actual running voltage) in the stock implementation (not just bench testing) to reach saturation on the ignition module. The difference can be attributed to a lot of things, but at the end of the day the results are what are important.

In my opinion, the coil that you found will not hurt the ignition module as it looks like it will take longer to reach 9amps than the stock coil, so you won't run the risk of the ignition module holding the amperage for too long and overheating with the stock configuration. And unless you're running forced induction with a lot of boost, the slower current build up shouldn't be a problem and it will probably work fine.

For reference, I've found that over dwelling the ignition module results in missed ignition events as the ignition module refuses to charge the coil until the ignition module has cooled back down. And there is no point to over dwelling it since it clamps the current at 10amps. And dwell time beyond that point just generates heat with no benefit. Likewise, if the coil builds current too slowly, and the stock dwell map doesn't give it enough time to charge, then you'll end up with missed ignition events due to weak spark under high load at high RPM.

Modifying the stock dwell map isn't possible with the SharkTuner's interface. You might be able to edit the dwell map in a bin file with TunerProFree, and then use SharkTuner to upload that bin to a SharkTuner PEM. But, as far as I know, the dwell map on the 928's bin isn't publicly documented or identified. I would guess, though without supporting evidence, that it is identical to the 944's dwell map:



My conclusion...it should be safe to try. To confirm that it's good to go: wide open throttle from 2k to redline in at least 3rd gear (manual). If there are no misses, then it should be fine.

But, don't take my perspective as definitive. Do whatever you're comfortable with.

928NOOBIE

Bulvot: much appreciate your time and thoughts. Inital results feel good.