Lemans
Well-Known Member
Spreadsheet ‘4-stroke’ horsepower
For those who are planning on converting a 4-stroke engine, here is a spreadsheet
witch is really easy to use. It’s in metric units so I added the usual converters for
torque and displacement.
Why this spreadsheet?
I know there are a lot of claims out there who are based on wishful thinking and sellers talk. This spreadsheet will give you a fair idea if power-claims for 4-stroke engines are possible. I know that every engine is different so I added my so called ‘combustion efficiency’. This factor includes the correct percentage of volume aspirated by the engine, form of combustion chamber, used fuel, etc…
‘Combustion efficiency’ is directly related to specific torque – figures we can find easily on engine specs – industrial/cars/airplanes/motorcycles – and they are all related more closely then we expect.
I took the freedom to compare European car specifications to distillate a specific torque history throughout the years. We can see that the car industry is gaining no more than 0.5Nm a year… In production engines, records are held by the BMW M* series with a specific torque of 113Nm (CE-98%) and Yamaha R6 with 115Nm.(CE-100%)
It’s obvious that you can’t predict your future engine power if you don’t know witch CE value to fill in for your engine.
If you are counting on adding a correct ignition system, correct compression ratio, good timed camshaft and correct intake system, a CE of 75% for an industrial based engine is realistic as is a CE of 80% for car based engines.
You will noticed that high power is only possible in the very high RPM’s.
Example is an F1-Engine who delivers nearly 900 HP with a CE of 113% (@16000RPM)
Enjoy playing with CE – RPM and engine displacement.
By the way: 600cc is written as 0,6 liter - notice that it's not a point in the middle!
For those who are planning on converting a 4-stroke engine, here is a spreadsheet
witch is really easy to use. It’s in metric units so I added the usual converters for
torque and displacement.
Why this spreadsheet?
I know there are a lot of claims out there who are based on wishful thinking and sellers talk. This spreadsheet will give you a fair idea if power-claims for 4-stroke engines are possible. I know that every engine is different so I added my so called ‘combustion efficiency’. This factor includes the correct percentage of volume aspirated by the engine, form of combustion chamber, used fuel, etc…
‘Combustion efficiency’ is directly related to specific torque – figures we can find easily on engine specs – industrial/cars/airplanes/motorcycles – and they are all related more closely then we expect.
I took the freedom to compare European car specifications to distillate a specific torque history throughout the years. We can see that the car industry is gaining no more than 0.5Nm a year… In production engines, records are held by the BMW M* series with a specific torque of 113Nm (CE-98%) and Yamaha R6 with 115Nm.(CE-100%)
It’s obvious that you can’t predict your future engine power if you don’t know witch CE value to fill in for your engine.
If you are counting on adding a correct ignition system, correct compression ratio, good timed camshaft and correct intake system, a CE of 75% for an industrial based engine is realistic as is a CE of 80% for car based engines.
You will noticed that high power is only possible in the very high RPM’s.
Example is an F1-Engine who delivers nearly 900 HP with a CE of 113% (@16000RPM)
Enjoy playing with CE – RPM and engine displacement.
By the way: 600cc is written as 0,6 liter - notice that it's not a point in the middle!
