BMEP refers to the term "Brake Mean Effective Pressure" and is a theoretical but simple way to compare the performance of similar engines as well as evaluating "Performance Claims" of parts and or engine builders. A engine designed for reliability that is naturally-aspirated and gasoline-fueled would normally have a BMEP of under 205 psi. Anything above that would require a very expensive engine development program. (ie: WSB, Formula 1) The formula for BMEP (psi) = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (Cubic Inches). Looking at our example above and plugging in the numbers - The 200HP is at the rear wheel so we need to add a very reasonable 15% on top because BMEP is calculated at the motor. So that means 230HP peak at the engine at aprox 12,000 rpm which calculates back to 100 ft lbs of torque at 12,000 rpm (HP = Torque X Rpm / 5252. So BMEP of thi phantom engine would be 150.8 x 100 / 61 = 247psi. Somebody is lying....
If we Plug in the numbers for a stock R! as pictured in the Dyno graph below we can see it is a much more reasonable figure of aprox 190 psi. If we use a BMEP number of 205 psi @ say 12,000 rpm you can see that a realistic potential HP for a modified R1 would work out to 83ft lbs of torque or 190 Hp and that is at the motor! Rear wheel would be aprox 15% less at 162hp.
I have been involved in mechanics and motorcycling from a young age. I formed Cycle Improvements in 1981 and still have the same passion to learn today as when I started. Hope you find this blog interesting and educational.