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
Throwback: 5 MORE Vehicles from PASMAG in 2009
Toyo Tires Unveils New Proxes Sport 2
Eaton to Showcase GM and Jeep ELocker and Detroit Trutrac Differentials at SEMA 2024
Yokohama Tire GEOLANDAR M/T G003 SxS
Hyundai N and Toyota GR Team Up for Unlikely Collab Event
Subaru's BRZ Series.Purple is an Exciting Limited Edition
