Some updates.
The 2.9L engine parts are almost completed. This engine config uses a different piston forging as the 93.00mm bore allows the use of the lighter bridged forging. This forging also allows for a much shorter compression height making the piston lighter as well.
The biggest gain had in this engine is the connecting rod. Its a lot longer than stock and lighter. They are coming in, sub 480 grams. The first prototypes are close to been finished and tested. Once we have this completed they will go into production.
There is only so much you can expect these small displacement engines to produce. Heads have limited port sizes, valves sizes are dictated by cylinder bore size etc, so component weight and friction are two areas that gains can be had. We know how much these engines can theoretically produce with the energy contained in the fuel, and by subtracting all of the loses known in 4 cycle engines we end up with a number between the actual measured BHP and what the calculated HP is. This amount of HP is what we can influence with component design, component weight and lowering parasitic losses.
Friction is a huge loss in small engines so anything that can be done to lower this is a huge help. Anything that slides against something creates friction and heat and this energy is lost is just turning the engine over.
The work involved and these parts come at a cost. They are not cheap and not intended to take the place of current parts sold by other vendors. They are intended for those that what a more modern interpretation of these earlier 911 engines with components that are engineered and designed to extract more performance.
There are new pistons in design for single plug versions of both these engines and as soon as they are completed I'll post photos. Included are pistons for the 98.00mm bore as the 3.4L conversion from 3.2L seems quite popular. The new design is a compete departure from the ancient wedge type sold currently for these engines.