• Mercury Racing Blog: 565: How’d We Do That – Part 1?

    Mercury Racing’s 565 - with digital throttle and shift (DTS), better fuel economy and more grunt – prompted more than a few questions. Mostly variations of: “How’d you do that?” We agreed to blog and provide some answers. In Part 1, I’ll discuss about torque and power. Part 2, fuel and DTS.

    Torque. How big are the bombs and where do they push?

    As I said in discussing our QC4v 1350, “The Valve Train That Could,” bigger bombs make more power. We pack more air because we designed the heads and inlet valves to flow better. Admittedly, they’re still two valve heads and not as free flowing as our four valve engines, but they’re better than our previous two valve designs. With more air, more fuel is added for combustion and makes a bigger bomb. Yet, fuel economy is better! How? Improved and more precise fuel delivery to each combustion event makes less wasted (unburned) fuel. Easy to say; hard to do – but we did it. (More about that in Part 2.)

    565 crankshaft (pictured) has 4.25 inch stroke compared to 4.00 of Racing’s 525 EFI. Photo: Mercury Racing

    The 565′s greater torque is due in part to its longer stroke. The lever arm (from center line of the crank to the center line of the rod’s big end) is 4.250 inches compared to 4.000 for Racing’s 525 EFI. When combustion force pushes on the connecting rods with their “big end” farther from the crank center line, it develops more leverage yielding greater torque (defined as “force acting at a distance from a fulcrum”).

    Read the full blog post here >>
    Comments 1 Comment
    1. nthdegree's Avatar
      nthdegree -
      he means the "lever arm" is 1/2 those dimensions...