STU666V
Active Member
How can you tell from a stroker crank and a standard crank?
Found this info but how do you tell by looking at one?
Found this info but how do you tell by looking at one?
WHAT THE HECK IS A STROKER? The term 'Stroker' means that someone has increased the stroke of their engine. Displacement is determined by BORE (the size of your piston) and STROKE (how far that piston travels up and down). There are two ways to increase displacement: You can increase bore (with a larger piston), and/or you can increase stroke by moving the crank pin (the pin holding the rod to the flyweights) further outwards on the flyweights. If you aren't familiar with general engine operation, check out some diagrams: WHY STROKE INSTEAD OF JUST GO BIG BORE? Okay, so we've increased the stroke. You now have more power from the displacement increase, but you've also gained more torque. Why? Because moving that pin location outward on the crank is just like using a longer wrench to remove a stubborn bolt. You've given the engine more leverage. This allows the engine to generate power at lower rpm much more easily. Another good thing about increasing the stroke is that with any engine that you plan on really going big, it makes more sense to increase bore and stroke, rather than just stick in a whopping large piston. In most cases, keeping the bore and stroke increases relatively equal, you will end up with a powerhouse that's more reliable and delivers power more evenly. GREAT, WE'VE STROKED THE CRANK, AND THE PISTON'S HITTING THE HEAD, NOW WHAT? Ok, there's a few ways to solve the problem:
There are also some engines which have a weak rod design. We replace those stock rods with our own heavy duty rod which is the correct length. CAN'T I JUST REPLACE THE ROD WITH A LONGER ONE? Rod length has nothing to do with displacement. Really. Trust us on this one. Here's the best way to figure out why this is true. You've probably got a glass of your favorite beverage sitting in front of you right now, don't you? Okay, lets say that glass is 1/2 full and has 10 oz of liquid inside. Now, pick up the glass and hold it up in the air. Is there more liquid in the glass? Nope. Same amount, it's just in a different location. Now, put the glass back down. Same amount of liquid? Of course -- unless you cheated and took a swig on the way down. The rod does the same thing that your arm just did. It only changes the location, but not the displacement. Changing rod length can change the way an engine produces power, but it will never change the actual displacement. Okay, take a drink of the stuff in the glass, you deserve it! WHAT IS DISPLACEMENT? Displacement is another term for engine size. It means 'how much volume is displaced by the piston travel'.
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HOW TO DETERMINE THE CC'S OF YOUR ENGINE Since most people don't want to go around pouring fluids in their cylinder to determine cc's, there's a formula you can work to figure the displacement of any engine.(WITHOUT FILLING IT FULL OF WATER) BORE (in cm) X BORE (in cm) X STROKE (in cm) X .7854 = Cylinder cc's Of course, if you have an engine with more than 1 cylinder, you X's the number by the amount of cylinders.Here's the formula at work. You've got an engine with a piston size of 47.5mm, and a stroke of 50mm. Converting mm to cm is a cinch - just move the decimal point to the left one spot (heckuva lot easier than fractions, huh??). 4.75 x 4.75 x 5.0 x .7854 = 88.60 cc's If this happened to be a V-twin engine, then we'd times that number by 2. 88.60 x 2 = 177.20cc's And yes, you can use this formula to determine the volume of any cylinder. Go measure your beer mug or Starbucks thermos - the formula's the same - as long as it's a straight cylinder - tapers are different! |
