Someone recently asked, “Why a longer rod?” Someone else answered, “Longer dwell time.” I never really thought about it before, so I thought I’d look into it. Using some basic math, we can prove that a longer rod does indeed create a longer dwell time around top dead center.
As you can see in the diagram, the piston with the longer conrod spends more time around top dead center (0 degree crank angle) due to a slower acceleration rate towards and away from TDC. A longer dwell time around top dead center makes better use of the combustion pressure and turning the pressure into torque; a rule of thumb is that you want peak combustion pressure around 15-17 degrees after TDC. Furthermore, the combusiton pressures are higher while the crank angle is lower resulting in less side loading of the piston into the bore. Less side loading results in less friction between the piston and bore freeing up power and reducing wear. The reduced piston acceleration also improves piston ring life as the lower acceleration equals less force on the rings (remember F=ma?).
Read the rest of the article at Moto IQ
Related Articles
Unitronic Adds UniLOCK Immobilizer Feature to UAF App
Ferrari Reveals the Amalfi Spider Convertible
RAYS Introduces New Super Dark Gunmetal Finish for HOMURA 2X9R Wheels
Honda Cancels Three Upcoming U.S.-built EVs
KW Suspensions Debuts HLS Evolution Lift System for Extra Ground Clearance on Demand
The GRIDLIFE Deal Everyone’s Talking About—and Why Racers Should Care
