BMW R100 Engine with Rotor C Type Gearbox
1972 BMW 980cc at Cadwell Park
Porsche 3.2 flat six Running E85 Bio Ethanol STF = short term fuel trim; LTF = long term fuel trim 25/23.4% leaner on PJI
During the development in 2001 of the iconic BMW air cooled R-series engine for aviation use, we encountered a few problems that weren't apparent in the motorcycle it was designed for. The first was cooling, in an aero engine we measure cylinder head and exhaust gas temperatures, this gives early warning of impending doom, which is necessary as there are no lay-by's at 3,000ft! We found that if the engine was held at BMW's quoted max continuous rpm of 7k rpm, the EGT's and CHT's just kept climbing beyond component manufacturers specification even with a 68inch 3 blade cooling fan!
The CHT's was simply about altering the flow of cooling air, drawing air over the heads rather than blasting it at them is much more efficient. The EGT's were more of a challenge, not only high EGT's but an awful lot of valve seat recession which go hand in hand. My conclusion was that there wasn't enough TDC turbulence to help propagate the flame...There had to be a better way! The Pulse-Jet pre-combustion chamber was born and the fun of testing different designs began
"Man with fire stick on hand, burn hand, Man with fire stick in clenched fist blows hand off".... Pulse-Jet Ignition, a pre-combustion chamber where a small percentage of the cylinder charge is ignited with a spark, by igniting a small charge in a confined space the pressure and temperature rise very quickly, the emerging explosion from the PJI ports causes a huge amount of turbulence with multiple flame fronts.