Improving TDI Oil Galley Piston Cooling

The original post is from Franko6 on TDI Club here

This is the local copy of that discussion so it's not lost.

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Put this one in your 'annal engine build' files under "incremental improvements for assembling a performance engine".

The advantages of an oil-galley piston and tapered (keystone) wrist pins in our opinion, is an obvious benefit and foregone conclusion. Every diesel engine now produced that is turbo charged, has oil galley and keystone pistons. Both improvements are reasonable, cost effective and improve durability of the rod/ piston assembly. However, when modifying the ALH and AHU engines the oil squirts require your attention.

1) Oil squirts are not all the same size hole. We have checked many oil squirts and the smallest oil squirt hole measured with a Numbered drill set shows that the variation of the oil squirts is as small as a #48 (.0760") or as large as a #42 (.0935"). In this case, we think 'more is better'. We re-drill each oil squirt to the #42 hole size.

2) The original pistons on all of the 1Z/ AHU/ ALH and a few of the PD motors are not galley cooled pistons. this means the oil squirt simply sprays the bottom of the 'dome head' piston. The oil squirt is aimed "UP". The oil squirt must be redirected into the oil hole closest the the 'dog house' cutout in the bottom of the piston, as shown in the pistons below.

This is pair of 79.5mm pistons intended for a large variety of TDI engines. We specifically use these pistons with our beveled connecting rods for all 1.9 liter engines, except the AAZ or it's counterparts. The picture for the Left piston is a little deceiving, as the angle makes the oil squirt hole appear quite large, but the Right piston shows the perspective that the oil squirt would be aimed from. The hole is quite a small target.

Here are a piston set showing Before/ After picture where we have made the approach to the galley hole into a funnel.