On the basis that Alan has probably already decided not to go down the 924 turbo route I hesitate to respond, but here goes [
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Narrowing the choice of vehicle down based on the reliability of solely one component of the car may not be the best decision process to follow. I identified three main differences between S1 and S2 924Ts in my earlier post.
When considering reliability, compression ratio is unlikely to be a significant factor in overall reliability, and while the DITC system is theoretically superior to the TCI-H electronic ignition system fitted to the S1 cars I doubt that there is any real difference in reliability here. (Even though I have suffered from DITC pickup sender failure, but not TCI-H failure and the ignition timing on S1 cars can be changed)
This leaves us with only the turbocharger itself as a difference which could cause changes in reliability. Rather than discuss the difference in the compressor housing between mk1/2 and the many breather modifications Porsche introduced throughout the life of the model which can be applied to either model, isn't it better to look at the question another way ?
Are you are better with a good series 1 car, possibly with a recently rebuilt turbo, against any series 2 ? Both of the cars are going to be over 20 years old so maintenance, quality of oil used and oil change frequency are going to be the biggest determinants of reliability of the turbocharger.
Coming back to the comment about 924 speedos...... I have had at least two fail at around the 80,000 mile mark. It's one of the small plastic gears that fails. I would not be surprised to find any car that has covered that sort of mileage to have a replacment speedo.
