2011 Volvo XC90 Base, FWDFACTORY OEM SERVICE PROCEDURE

Crankshaft Movement

Fig 1: View Of Crankshaft Relationships
GLL154236Courtesy of VOLVO CARS CORPORATION

To achieve an even running and characteristic V8 sound, the ignition impulse interval is 90 crankshaft degrees. To reach this in an engine with a 60 degree angle between the cylinder banks, the crankshaft pins for the opposing cylinder pairs are offset by 30 degrees.

Fig 2: Identifying Crankshaft Pins Offset By 30 Degrees.
GLL154237Courtesy of VOLVO CARS CORPORATION

When the left hand piston is at the top, the right hand piston is halfway between the upper and lower turn points. This is because the crankshaft pins are internally offset by 30 degrees.

Fig 3: Crankshaft Rotated 90 Degrees
GLL154238Courtesy of VOLVO CARS CORPORATION

When the crankshaft has rotated 90 degrees the right hand piston is at the top and the left hand piston is halfway between the upper and lower turning points.

Fig 4: Ignition Impulses Occur Every 90° Crankshaft Rotation
GLL154239Courtesy of VOLVO CARS CORPORATION

When the crankshaft has rotated a further 270 degrees the left hand piston is at the top and the right hand piston is halfway between the upper and lower turning points.

By offsetting the crankshaft pins by 30 degrees in this way the ignition impulses will occur every 90th crankshaft degree.

Fig 5: Identifying Ignition Impulses
GLL154240Courtesy of VOLVO CARS CORPORATION

The Example shows the principle for cylinder 1 and 2. With the firing order 1-8-4-3-6-5-7-2 the following occurs:

  • Cylinder 1 fires.
  • The crankshaft then rotates 360°+270°=630° until cylinder 2 fires.
  • The next ignition impulse, now again for cylinder 1, occurs when the crankshaft has rotated a further 90 degrees.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.