wwentzler
New member
- Joined
- Jan 4, 2017
- Messages
- 152
Well this all started with a theory, that maybe engines with a longer rod to stroke ratio, such as a deckplate engine, could be more efficient at delivering downward piston force, into raw crank torque. Ill start off by saying, the calculator shows the differences are negligible and my theory was wrong.
The calculator does however show the raw data, so I felt as though maybe others would find this interesting.
Basically how it works, is I have run the calculations as to what percentage of piston force is turned into crank torque at each degree of the crank, 90* being TDC, and I only felt necessary to show through 180*, which is where the crank forms a right angle with the cylinder. I showed the data for 4 different common cummins engine characteristics. If you care to look at the math, its all there i just hid the columns. Theres a graph on the second sheet that shows all 4 curves as well.
For those that dont follow, cylinder pressure creates a piston force stright downward, and through a connecting rod, that force is turned into a rotational force (torque). However, that force is not transferred 100%, some is lost to the sides of the cylinder walls, as well as the bearings.
Some interesting things I noticed with the data, is this shows how important timing is, as well as ROI. As you can see, massive cylinder pressure in the early degrees after top dead center does not translate to much crank torque, aka headgasket gets alot of that force, as well as the rod and crank.
Also if you dig through the hidden columns youll find rod angle at each degree, notice there is virtually no difference between a stock 6.7 rod angle and a 6.4L, so the rod angle thing is myth(bending rods)
Feel free to check my calculations, i could have easily made errors. If there are any questions feel free to ask. Enjoy! :rockwoot:
The calculator does however show the raw data, so I felt as though maybe others would find this interesting.
Basically how it works, is I have run the calculations as to what percentage of piston force is turned into crank torque at each degree of the crank, 90* being TDC, and I only felt necessary to show through 180*, which is where the crank forms a right angle with the cylinder. I showed the data for 4 different common cummins engine characteristics. If you care to look at the math, its all there i just hid the columns. Theres a graph on the second sheet that shows all 4 curves as well.
For those that dont follow, cylinder pressure creates a piston force stright downward, and through a connecting rod, that force is turned into a rotational force (torque). However, that force is not transferred 100%, some is lost to the sides of the cylinder walls, as well as the bearings.
Some interesting things I noticed with the data, is this shows how important timing is, as well as ROI. As you can see, massive cylinder pressure in the early degrees after top dead center does not translate to much crank torque, aka headgasket gets alot of that force, as well as the rod and crank.
Also if you dig through the hidden columns youll find rod angle at each degree, notice there is virtually no difference between a stock 6.7 rod angle and a 6.4L, so the rod angle thing is myth(bending rods)
Feel free to check my calculations, i could have easily made errors. If there are any questions feel free to ask. Enjoy! :rockwoot:
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