Oil line sizing for 3.2 conversion

sandiego · 11-01-2005, 12:35 PM

The opening (behind the cooler) for oil going into the engine on a 3.2 is 7/8". For a 2.7 its 5/8". I've read that I should go to a dash 20 hose (7/8" ID) with an inner support coil from the oil tank to the engine. The dash 20 has an ID of 1 1/8". I'm trying to understand why the hose has to be so much larger in cross sectional area than the opening. Does this make the walls of the hose less prone to collapsing under high oil demand? Car is a dedicated TT car.

How hard is it to modify the oil tank (on a 914/6) to dash 20 hose? Can it be done without leaving metal particles?

DW SD · 11-01-2005, 01:18 PM

For this application many use as small as -12. If the oil tank is mounted remotely (more than 10 feet away) -20 may be necessary. -16 or even -12 should be more than fine if it is just a few feet away.

Are you building a 914/6 w/ a 3.2?

I have a rear mounted oil tank w/ rear mounted engine and use -12 throughout for my application. I understand mine may be undersized and loading up the sump oil (sump evacuation) pump. My oil pressures don't seem exceedingly high or low, however, but the pressure gauge reflects pressures on the other engine oil pump.

Hope that makes sense.

As for the cross section being so big, the straight sections of lines aren't the problems it is when they go around corners (especially 90degrees or more) that adds "head" to the overall system. Head = load for a pump.

sandiego · 11-01-2005, 03:00 PM

I'm going on the premise that if Porsche enlarged the inlet from 5/8" to 7/8" between the 2.7 and 3.2 liter that they had a reason. Smart Racing in their catalog recommends dash 20 for the input side and dash 16 for the outlet side, although they dont specify the engine size. Otto's told me "dash 20 and go as big as you can".

I believe the 3.2 outlet opening is 7/8", so using less than dash 16 would add restriction over the stock set up.

I'd love to not have to change the fittings on the front cooler and oil tank as well as put in larger lines and a different thermostat, but am nervous about going with dash 12 or 14.

DW SD · 11-01-2005, 03:36 PM

You may want to await other opinions. I suspect Otto and SRP know best.

What is your application? All are not equal. Is it a 914 w/ front mounted oil tank? The application may drive their suggestions.

Doug

sandiego · 11-02-2005, 03:08 PM

For now it is the stock factory tank. If I go to larger lines I will have to modify the oil out fitting and the oil in fitting. Not sure what to do about the filter mount and the filter itself-possibly they cant handle the flow. I new front mounted tank might be no more expensive than all these mods.