Guys,
Thought I would add to this topic. I am currently overseeing the build of a 100x71 type 4, 964 P&Cs, programmable EFI, DIS, Jenveys, Porsche 964/BAS cooling system and exhaust, mildly modified heads. The owner has a dry sump pump to go with it and this would be my first dry sump so I am doing my home work.
First off, we can't easily alter the shape of the original oil sump similar to the in-line and V engine guys with bolt-on sumppans do. That means the little oil that will be in the sump will be way below any moving parts. Porsche published a tech bulletin for the connecting rods, they should be notched for additional cooling/lubrication of pistons and wrist pin. I can see how this becomes even more problematic in a dry sump set-up.
In-line and V engines mostly have one or more OHCs, or at least a cam that is above the crankshaft. This will establish more oilflow in a dry sumped in-line or V engine than in our boxer engines. This still creates enough splash lubrication, even enough for the in-line and V engine guys to be wanting to reduce windage even more. Some go as far as to alter the oil return paths so less oil will find its way to the crank. Our boxers have relatively little oil travelling to the heads and most of it will flow back into the sump without ever touching the crank. The need for additional camlobe lubrication has come up here and there, so -expecially- because we cannot change the dimensions of the crankcase easily so its walls keep oil closer to the moving parts like it would in a 911 case. Additional oilers/jets for piston cooling/wrist pin lubrication are not easily fitted in a type 4. I only ever saw one case that had this done and it had an incredible amount of welding done to it.
This engine does not have a mechanical fuel pump or distributor drive, but those could be possible problems for others who are dry sumping with those parts in place.
I know a type 1 with additional sump will run considerably hotter (no exact data) when ran with an oil level upto about the original oil pick up vs. stock configuration.
We have the Schadek pump. I enlarged the exhaust ports of the pressure side to 11mm. This pump still does not make me very happy. I am leaning towards recommending a 2-stage Autocraft pump but any info/experiences with quality DS pumps is welcome. I am also leaning towards wet sump in this case. This is a non track driven Bus.
Any thoughts or data on this would be greatly appreciated.
Brian
www.karrera.net