 Figure 1: European Piston with Flat Top  Figure 2: USA Piston with Dished Top |
Question: I'm rebuilding my 914
motor. I've heard that there are two types of factory pistons & cylinders, USA
& European. What are the differences between these two types? Answer: [For Mahle Pistons] The European pistons are manufactured with a flat top that increases the compression ratio of combustion chamber to 8.0/1 on the 2.0L motor, versus 7.6/1 for the USA pistons. The European 2.0L piston is shown in Figure 1, and the USA type 2.0L piston is shown in Figure 2. This increase in compression ratio results in an approximate increase of 5 horsepower for a total of 100 for a 914 2.0L with the European Pistons. Similar percentage horsepower increases are seen when the 1.7L European pistons are used to rebuild a 1.7 motor. The cost of the European pistons is generally less than the USA pistons. Most rebuilds upgrade to the European pistons for the performance increase. The cylinders are identical between the two types. Several readers have pointed out that the Kolbenschmidt Euro pistons do in fact have a dish. These pistons were also used on stock 914s. The compression ratios are similar to the Mahles shown above. We are currently looking for info and pictures of these pistons. Rough calculations reveal that the final combustion chamber size for the 2.0L motor should be approx 259cc with the USA pistons, and approximately 246cc with the Euro pistons. This means a difference of about 13cc. Assuming that the dish is about 7.5 cm wide and .3 cm deep, that comes out to be approximately 13cc. |
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