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Specialist in turbos, quattros, electrics and non-starts

Audi I5 turbo engines - crankshaft measurements and tolerances.

Crankshaft bearing tolerances are measured with Plastigage, manufactured by Perfect Circle. Only PR-1 is essential for ur-quattro measurement - 0.051mm to 0.152mm. PG-1 is sometimes useful - 0.025mm to 0.076mm. This is a calibrated plastic thread which is laid on the bearing surface. The bearing is reassembled to the test torque figure, taking great care not to rotate the bearing. When the bearing is dismantled, the thread will have spread out as a result of the pressure and the tolerance can be read directly using a scale on the Plastigage envelope. The tighter the bearing, the more the plastic thread will have spread.

I5 specific values:

Main bearing test torque: 65Nm
Big end test torque: 50Nm
Tolerances: 0.010mm to 0.058mm new - wear limit 0.120mm
Axial play (dial gauge) 0.07mm to 0.23mm new - wear limit 0.29mm

If the engine is out of the vehicle or the clutch bell housing has been removed, it is a good idea to measure the gap between the flywheel pin and tooth senders. Nominal gaps are:

G4 - TDC (pin) sender - 0.45mm to 1.25mm
G28 - flywheel tooth sender - 0.51mm to 1.24mm

Note the values with the date they were measured and place the document in the vehicle's service book or file. They can be useful sometimes in debugging but are very difficult to measure with the bell housing in place.

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Contact Phil Payne by email or use mobile/SMS 07833 654800