924Board.org

[leadfoot]

The pistons I have had no directional markings on them so to confirm this for my application; pretty sure I have things right but an experience hand to give the green light would be appreciated.

I took the piston and turned it over to look at the bottom.
measured from the pin centreline to the skirt.
There were two measurements, one small and one large, the pin being offset.
The side with the lower measurement is the thrust side of the piston.
So with an engine turning clockwise, it's on the inside.
Turn the piston over, directional arrow should be to the right with the smaller measurement facing me.
This also need to line up with the directional pips on the rods.

can I get a hell yeah...
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[Smoothie]

Are the pistons assembled to the rods? (If so, maybe can make an educated guess based on the oil squirter position, and which side of the engine they should be on..)
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[gegge]

In this case should the arrow point forward.

The narrow offset - small measurement should be on the major thrust side during the combustion. The thrust side is on the passenger side(EDIT: exhaust/right side ).

If you turn them over you get increased maximum cylinder pressure with risk of pinging and less friction. Could get better MPG?

But seriously, check porsche 928 and 911 and even they mixed it up having the offset different depending on left/right side

Copy paste from the Mahle website:

"Why do most pistons have a pin bore offset?
Due to the rotation of the crankshaft, the connecting rods are at an angle in most positions. This is pressing the piston towards one side of the cylinder bore during its upward movement. At the upper piston dead centre, the connecting rod stands exactly vertical and then starts to form an angle towards the other side. Also the piston begins now to lean towards the other side of the cylinder bore. In order to soften the impact of the piston against the opposite side and to make it as silent as possible, the pin bore is slightly offset to one side. As a result, the piston tilts slightly around the pin axis during this change of leaning direction. The piston does therefore not hit the cylinder bore with its entire length, but touches the cylinder wall first only with the lower skirt end and settles then into a sliding movement against the other side. This reduces not only engine noise, but also the mechanical stress on the components significantly.

The pin bore is usually offset towards the pressure side of the piston. However, there are exceptions to the rule: some pistons are offset towards the other side, however, the effect is the same."


http://www.924board.org/viewtopic.php?p=279091&sid=76c171b801294c4d193d7948f3cafa2a
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[RC]

hell yeah...

The larger offset is on the intake side.

Your drawing is correct, with the arrow pointing forward.
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World`s quickest 924 2L slushbox

[leadfoot]