Rivals Automotive Performance
Expanding the Worlds Automotive Knowledge
Crank Design
vs
Sound
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WHY DO CARS SOUND DIFFERENT EVEN IF BOTH ARE 5.0L V8S?
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WHY DO AMERICAN V8S SOUND DIFFERENT TO EUROPEAN V8S?
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WHY DO V8S SOUND DIFFERENT TO V6S AND I4S?
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V8 CRANK DESIGNS
MOST AMERICAN V8'S WILL HAVE A CROSS PLANE CRANK WHILE EUROPEAN V8'S TYPICALLY HAVE A FLAT PLANE CRANK.
THIS DESIGNATION IS ABOUT THE ORIENTATION OF THE PINS WHERE THE PISTON'S CONNECTING ROD CONNECTS TO THE CRANKSHAFT.
V8'S USUALLY HAVE 2 CYLINDERS ON EACH OF THESE PINS, MAKING 4 POINTS
WHEN YOU LOOK AT THE CRANKSHAFT FROM THE FRONT BALANCER TOWARD THE TRANSMISSION, A CROSS PLANE CRANK WILL HAVE THESE PINS AT 4 DIFFERENT PLACES SEPARATED BY 90 DEGREES, AND A FLAT PLANE CRANK WILL HAVE THESE PINS IN 2 PLACES SEPARATED BY 180 DEGREES.
FIRING ORDER
BECAUSE THE CRANK PINS ARE AT DIFFERENT LOCATIONS, THE PISTONS WILL MOVE IN A DIFFERENT ORDER.
FOR FLAT PLANE CRANKS THE TYPICAL FIRING ORDER IS:
1-5-4-8-3-7-2-6
FOR CROSS PLANE CRANKS THE TYPICAL FIRING ORDER IS:
1-8-7-2-6-5-4-3
DUE TO THIS FIRING DIFFERENCE, THE CYLINDERS FIRE EVENLY IN A FLAT PLANE CRANK, SWITCHING BETWEEN BANK 1 AND 2.
BUT IN A CROSS PLANE CRANK YOU WILL PERIODICALLY HAVE 2 CYLINDERS FIRING FROM BANK 1 AND THEN FROM BANK 2 (CYL 2/6 AND 1/3)
BENEFITS TO CROSS PLANE AND FLAT PLANE
A FLAT PLANE CRANK WILL TYPLICALLY BE MUCH LIGHTER AND CAN REV HIGHER, BUT THERE ARE MORE UNBALLANCED FORCES THROUGHOUT THE POWER BAND. THIS CRANK DESIGN IS BETTER FOR SMALLER DISPLACEMENT ENGINES THAT AIM TO PRODUCE PROWER THROUGH HIGH RPM'S.
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A CROSS PLANE CRANK WILL TYPICALLY BE HEAVIER DUE TO HAVING MORE COUNTERWEIGHT, BUT THERE IS A MUCH SMOOTHER BALANCE IN THE LOWER RPM'S. THESE ARE USUALLY USED ON LARGER DISPLACEMENT ENGINES THAT REQUIRE LOWER END TORQUE.
EXHAUST NOTE DIFFERENCES
FLAT PLANE V8
-SMOOTHER PULSES
-HIGHER PITCH (MAINLY FROM CYLINDER SIZE)
-"RACECAR" SOUND
-SMOOTH IDLE
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CROSS PLANE V8
-RUMBLING
-UNEVEN
-BURBLING
-AGRESSIVE IDLE
V6 CRANK DESIGNS
MOST V6 ENGINES WILL BE A 60 DEGREE BLOCK WITH A 120 DEGREE OFFSET ON THE CRANK PINS. THIS MEANS A CLYIDER REACHES THE TOP OF EACH CYLINDER EVERY 60 DEGREES.
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SOME V6 BLOCKS WILL BE BASED ON THE 90 DGREE V8 BLOCKS AND WILL HAVE "SPLIT" CRANK PINS.
THIS MEANS THAT THE TWO PISTONS THAT NORMALLY SHARE A PIN, WILL HAVE 2 OFFSET PINS TO ACCOUNT FOR THE EXTRA 30 DEGREES NEEDED TO MATCH THE BLOCK ANGLE.
THE SPLIT CRANK PIN METHOD IS RARELY USED DUE TO COMPLEXITIES WITH BALANCING AND LIMITED STRENGTH, BUT THEY ARE USED BY SOME MAJOR MANUFACTURES LIKE JAGUAR WHO WANT TO SAVE DEVELOPEMENT COSTS.
EXHAUST NOTE DIFFERENCES
TRADITIONAL V6 ENGINES WILL SOUND VERY SMOOTH THROUGHOUT THE POWER RANGE, AND CAN EXPERIENCE A TRUMPETING SOUND AS THE EXHAUST WAVES COMPOND.
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WITH UNEQUAL LENGTH HEADERS A BURBLING SOUND LIKE A CROSS PLANE V8 CAN BE ACHIEVED.
INLINE ENGINES (I4, I5, I6)
VARIANCES IN CRANK DESIGN DO NOT USUALLY HAPPEN, BUT THERE ARE SOME INTERESTING ENGINES THAT DID.
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