The information about these pistons as they apply to use in hybrid engines that's being given out is jus tplain wrong. People seem to think that because an engine has a given compression ratio that the numerical value follows that piston everywhere it goes. This may be in large part because the aftermarket piston companies advertise pistons by their compression ratios instead of dish/dome volumes. They are usually selling to a specific application, not something that's going to be used in a custom setup. It's generally a lot easier for them to do it this way. So what does this mean for us? Well, it means that if I were to look up information about building a hybrid J-series with a J35A3 rotating assembly beneath J32A2 heads I would usually find information telling me about the necessary piston changes I would need to make. I would be told that the "RL" pistons from the J35A8 would yield 11.0:1 compression and that if I wanted to play it a little more safe that I should use "CL-S" pistons from the J32A2. Ignoring the nomenclature by which these pistons are referred I'm left to think that the person(s) giving this information out have simply never been inside an engine before. Let's assume that you have a given engine X with known, constant dimensions. Let's say that it's a 6-cylinder engine with an 89mm bore and an 86mm stroke giving it a 3210cc displacement. The crankshaft throw is 43mm (stroke/2), the rod length is 162mm, the compression height is 30mm and the piston-to-deck height is negligible for this particular exercise. The piston dome has a volume of +2cc and the combustion chamber is roughly 58cc once a 4cc headgasket volume is factored in. Those numbers would all equate to a bottom dead center (BDC) volume of 591.2cc and a top dead center volume of 56.1cc. If we agree that a ratio is a comparison of numbers then the definition of a compression ratio worded "the ratio of a cylinder's largest volume (BDC) to its smallest volume(TDC)" is easy to understand. In this case (591.2cc/56.1cc) equals roughly 10.54:1 CR. Again, this is engine X, our basis for comparison. Now, suppose we want to increase the performance of the performance of engine X by increasing its stroke. A 93mm stroke sounds nice. Since the throw of the crankshaft is now 3.5mm longer then either the rod length, compression height or piston-to-deck clearance will have to change in order to accommodate. Possibly more than one or all three. Let's just assume that it's the rod length alone to keep things simple. This will force us to use a 158.5mm-long rod. So again, we have a 6-cylinder engine with an 89mm bore and a 93mm stoke giving it a 3471cc displacement. The crankshaft throw is 46.5mm (stroke/2), the rod length is 158.5mm, the compression height is 30mm and the piston-to-deck height is still negligible. The piston dome has a volume of +2cc and the combustion chamber is roughly 58cc once a 4cc headgasket volume is factored in. Since the piston is unchanged from the previous assembly many would assume that it has the same compression ratio. However, since the crankshaft has now moved the piston an additional 3.5mm further down the cylinder the volume at BDC has increased another 43.5cc. Add that additional volume to the original BDC and you get 634.7cc at BDC. Divide that by the volume at TDC which has remained unchanged and you know have somewhere near 11.3:1 CR using the same pistons in a 93mm-stroke combination vs. the original 86mm. What does this mean? It means that the entire time you've been told that the "CL-S" pistons were the safer option in a hybrid build because they were 10.5:1 vs. 11.0:1 you were being fed incorrect information by people who had no clue what they were talking about. You were actually using pistons that had an even higher compression ratio than the ones you thought best to avoid. Or, if you chose to go to the "RL" pistons for a higher compression ratio, then you wasted the money as you likely already had a J32A2 base that this was being built on. If not, then the J32A2 pistons would certainly have been the cheaper alternative. The incorrect information has been "common knowledge" for way longer than it should have been.