Pistons

Removing and installing pistons on 4.8-liter DFI engines

Preliminary work

1. Remove the engine.
2. Remove engine from transmission.
3. Secure engine on assembly support.
4. Drain engine oil.
5. Remove timing chain.
6. Remove cylinder heads.
7. Remove oil pan and oil guide housing.
8. Remove oil pump.

Information

Component overview

Piston, connecting rod

1 - Piston-ring set; oil with engine oil; TOP marking facing upwards; oil scraper ring down
2 - Piston; different on naturally aspirated and turbo engines; combustion chamber recess facing center of engine; left and right different; direction of travel arrow in direction of travel
3 - Piston-pin circlip (positioned at 6 o'clock or 11 o'clock)
4 - Piston pin; oil
5 - Connecting rod
6 - Connecting rod bolt; replace as it must be tightened in the plastic area; oil bolt - Tightening torque: 8 Nm (6 ftlb.) +2 Nm (+1.5 ftlb.) - Tightening torque: 20 Nm (15 ftlb.) - Tightening torque: 40 Nm (30 ftlb.) - Torque angle: 90 degrees
7 - Connecting rod bearing shells; oil with engine oil

Connecting-rod assembly, bearing shells

A - View A (identification area for connecting-rod number; fit connecting rod with identification area facing exhaust side; markings on rod and cap must be on the same side)
B - View B (fit bearing shells flush and press in by hand)
C - View C (fit bearing shells flush and press in by hand)

Crankshaft

1 - Crankshaft
2 - Straight pin, 6 x 20
3 - Spring, 5 x 6.5
4 - Thrust washer (grooves facing out)
5 - Main bearing shell, upper
6 - Main bearing shell, lower
7 - Shaft sealing ring - Do not touch sealing ring lip! Clean crankshaft flange and oil lightly
8 - View of crankshaft flange
9 - Crankshaft bearing classification (example: YYYYY-BBBB; 5 main shaft bearings with yellow marking, 4 double (8) connecting rod bearings with blue marking) - For numbering, see A
A - Direction of travel (main bearing 1 is the first in direction of travel against output)

Identification of pistons

Information
The piston is identified as a spare part by the following characteristics: one dimensional group X, Naturally aspirated or Turbo, cylinder bank 1 to 4 or 5 to 8.

The piston is installed as standard in two additional weight tolerances: + and -.

This information is all engraved on the piston crown. To identify the piston uniquely, the piston must be cleaned carefully (brass brush, ultrasound bath).

Markings on piston crown: Replacement pistons are only available from the Porsche Parts Service in dimensional group X and in two weight tolerances '+' and '-'.

Piston classification

1 - Inspection stamp (supplier)
2 - Arrow marking in direction of travel
3 - Porsche short numeric code without main or middle number
4 - Cylinder bank identification
5 - Marking area for weight group (weight tolerance)
6 - Marking area for dimension group
7 - Barcode 128 (short numeric code (without main group) and weight group)
8 - Direction of travel arrow
9 - Short numeric code (supplier)

1. In the event of repairs, the removed piston must be cleaned and identified. If the piston needs to be replaced, an X piston with the identified weight tolerance + or - for the correct cylinder bank is ordered and installed as a spare part.

Removing pistons

Information
Note the association between the connecting-rod big end and the connecting-rod bearing cap as the cracked connecting rods only fit in one position.
The retaining lugs of the connecting-rod bearing shells are always located on the same side in order to prevent the bearing shells from turning.
The connecting-rod bearing cap and the big end of the connecting-rod bearing have the same connecting rod numbers.

1. Remove oil return (oil plate) under the oil pump.

Oil guide (oil plate)

2. Loosen connecting rod bolts -6- and take off connecting rod caps -5-. Push piston in question out of the crankcase using a wooden rod. Hold it in your other hand or get another person to help. Fit connecting rod cap hand-tight to the connecting rod again using the old screws and set down after marking according to the relevant cylinder.

The connecting rods are cracked and the connecting rod code is facing the exhaust side.

The combustion chamber recess on the piston is facing the injector.

Piston, connecting rod

Information
Connecting rod bolts and bearing shells must always be replaced.
Turn the crankshaft so that the crank pin of the piston to be removed stands vertically upwards.

3. Remove the remaining pistons using the same procedure.

Installing pistons

Information
Connecting rod bolts and bearing shells must always be replaced.
The marking on the main bearings and connecting rod bearings is located on the flywheel flange of the crankshaft.

Information
The pistons must already be pre-fitted (pistons, piston rings, connecting rods and fastening material) before performing the next step.
Fit the number on the connecting rod -A- facing the exhaust side.
When installing the piston in the crankcase, the direction of travel arrow on the piston crown must point in the direction of travel.

Surface with cylinder number marking

The code on the connecting-rod big end and connecting rod cap must be on the same side -A-.
The direction of travel arrow is on the same side as the connecting rod code -A- on the piston shown. Fit the number on the connecting rod -A- facing the exhaust side.

Allocation

The direction of travel arrow must be pointing forwards (in direction of travel) when installed -inset-. The combustion chamber recess -1- on the DFI piston is facing the inner V (center of the engine) when installed -top arrow-.

Installed DFI piston in crankcase

Installing pistons - direction of travel arrow

1. Turn the engine in the engine support so that the crankshaft lies at the bottom.
2. Install the piston. To do this, turn the crankshaft with a wrench (a/f 27) until the corresponding crank pin is pointing vertically downwards.
3. Lightly oil the cylinder, piston and funnel 9784/1 (-1-).

Oiling the piston funnel

Alternatively, a commercially available piston ring restraining strap piston ring restraining strap for 944 - S2 and Boxster and 911 Carrera (996) NR.57 can be used.

1 - Oil the inside of the funnel
2 - Piston and connecting rod ready for installation

4. Align piston-ring set (offset by 120 degrees) and compress piston rings using piston ring restraining strap for 944 - S2 and Boxster and 911 Carrera (996) NR.57. Ensure that all piston rings are correctly tensioned by the special tool -see Figure-. If you are using a funnel 9784/1, slide the piston with connecting rod fitted into the funnel -2-. The collar of the funnel must be facing the crankcase -1-. Slide the piston into the funnel until the piston shank protrudes approx. one centimeter down out of the funnel.

Inserting piston into piston funnel

Piston inserted in piston funnel

Piston with restraining strap

5. Place the piston onto the cylinder from above and slide it into the cylinder using the handle of a hammer if necessary. When doing so, make sure that the direction of travel arrow is pointing forwards -see arrow (Figure shows cylinder 1)-. If you are using the funnel 9784/1, position it flush on the crankcase -3-. Check the position of the combustion chamber recess -1- and the direction of travel arrow when doing this.

Installing pistons

Fitting piston

6. Push the piston down until the connecting rod bearing is sitting on the lift pin. Push it down further using the handle of a hammer if necessary -see Figure-. Do not use force. If the piston is jammed in the tool, oil the tool again if necessary or carefully loosen and turn the piston.

Pressing in piston

7. Oil connecting-rod bearing shells and crank pins.

Information
The piston connecting rods are cracked and only fit in one position (in conjunction with the matching numbers).

Surface with cylinder number marking

Install con-rod code towards exhaust side -A-.

8. Then fit the connecting rod cap with bearing shell (twist lock together). The connecting rod numbers must be facing each other. Fit connecting rod bolts by hand.

Retaining lugs for connecting rod bearings -B and C-

View of matching numbers -A-

9. Fit the opposite piston (cylinders 1 and 4).
10. Fit other pistons using the procedure described above.
11. Turn crankcase on the assembly support until the crankshaft is on top.
12. Tighten connecting rod bolts that have been replaced. Turn the crankshaft until the corresponding crank pin is pointing vertically upwards. Tighten bolts with a multiple-tooth nut.
13. Once all pistons have been correctly fitted and secured, turn the crankshaft in a clockwise direction to check it using a ring wrench (a/f 27). When doing so, watch out for stiffness and irregularities. If the crankshaft cannot be turned or if it is very stiff, check whether the installation direction (arrow) of the pistons, the pistons and the cylinders (markings) and the connecting rod caps and connecting-rod big end all match.

Subsequent work

1. Fit oil guide/oil plate.

Oil guide (oil plate)

1 - Oil guide (oil plate)
2 - Oil return seal
3 - Screw, M6 x 20 - Tightening torque: 10 Nm (7.5 ftlb.)
4 - Bulkhead seal
5 - Joining socket
6 - O-ring
7 - Assembly depth until locking lug engages
A - Direction of travel

2. Install oil pump.
3. Install cylinder heads.
4. Fit timing chain.
5. Fit timing-case cover.
6. Fit oil pan and oil guide housing.
7. Fill in engine oil.
8. Remove engine from the assembly support.
9. Mount engine on transmission.
10. Install the engine.