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Classic Retrofit

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I just want to say a BIG thank you to Jonny Hart of Classic Retrofit.  He spent a chunk (nearly three hours) of yesterday sorting out a running issue with my car (principally coils - I turned up with a selection and found that operating characteristics vary from one Bosch coil to another, would you believe - and also fuel mixture) to make it run with a mapped CR CDI unit.  I learned a lot, plus I also got to see his workshop and test rigs, which are impressive.  And my car runs better than ever.

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Thanks David.   Sadly. in recent times, it appears not all Porsche parts are created equal!

For those interested in the running issues, David’s car would not idle or rev with our box CDI+ fitted, yet when we fitted the same unit to my car, it idled fine and went like stink.  Our cars are pretty much identical SCs (both have SSI and 964 cams).
 

The car did run on the original CDI unit although closer inspection revealed a hesitation under engine load at low revs.  We later adjusted the mixture a bit richer with better results.  Fuelling on CIS cars with 964 cams will always be a bit of a compromise.

The coil had been replaced with a new Bosch silver coil (as sold by Porsche themselves) which should have the same specification as the original Bosch black coil.

David brought the original Bosch black coil with him so we swapped back and we were in business!

The conclusion is that the silver coil does not meet the spec of the original.   CDI+ exploits the very fast charge/discharge time of the original coils to discharge two sparks in quick succession which gives a cleaner burn.   Sadly, the silver coil could not ‘cope’ with this.   The spark interval is programmable in our units but making this interval larger rather defeats the purpose of multi spark.

 

Polo red - great colour!

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Stripes, plus 20hp. Red, plus 10hp. That thing must be a monster! 😂😜 Lovely car David. 

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2 hours ago, Jonny Hart said:

Yup. 

Quelle surprise 🙄

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