What size AN fitting for oil system?

[TouringBubble]

Just curious what everyone is using?

All of the fittings for my oil system parts are 3/8 NPT. They are all aftermarket as there are no external oil parts stock.

I've got -6 AN fittings for the fuel system already, and was planning on -8 AN for the oil system. But, I'm reading that the ID of 3/8 NPT is approximately the same as -6 AN. Is running -8 AN overkill, or would -6 be a bottleneck if I went with that from the 3/8 NPT adapters?

What do you guys use?

[JohnW8]

-6 for my fuel and -8 for the oil cooler as well.

[Chuck Baader]

-6 fuel, -10 oil cooler/filter. CB

[TouringBubble]

Exactly what I was thinking. Thanks!

[Fusion Works]

It will depend on your oil pump and its capabilities. How long will the lines be? 8AN is the minimum, 10AN would be preferred, especially if you have a long run from the engine to the cooler. It will also depend on whether or not you are using a good oil cooler or a junky automatic transmission cooler that many people use.


What is the application and what parts are you using that have 3/8NPT fittings?

[TouringBubble]

This is for an aircooled VW engine. 2.1l build with a 30mm upgraded oil pump. I'm not sure the flow rate of the pump in comparison to other engines. All aftermarket accessories for the VW have 3/8 NPT fittings. It's just the standard people have used for them since the '60s.

I don'[t have the specs on the cooler as it's in GA with the rest of the chassis currently. It is an oil cooler though, not a small trans cooler.

Why is -10 preferred for a longer run to the cooler? I have to run about 3' to the cooler (estimate) from the engine. From the pump itself is more like 6' total. Again an estimation because I haven't decided on a location for the filter yet.

The pump pulls from a deep sump added to the engine, out to the external filter, through the engine, out to an external thermostat (to aid in proper warmup) then up to the cooler mounted in the rear window area.

In all honesty, as I'm certain the drag on the pump with increased volume of oil will sap torque output, If -8 is sufficient I'll likely stick with that. Plus, with the inherent small size of most all VW parts, including this oil pump, I don't know how it would like pumping the extra volume of 8'+ of -10 line.

[Cholewa]

I think the lines on the volvo that run to the cooler are -8. The drain from the turbo is the only -10 line in the car. And the oil cooler runs from the passenger side of the block over to the drivers side of the radiator, so it's a good 3-4 feet and back.

[TouringBubble]

Got ya. Yeah, I have the biggest pump you'll find without going dry sump, but it still only meant to pump through the ~24" through the case. So, I'm thinking -8 will be plenty of volume without putting too much stress on the pump/engine.

Being a rear engine setup, I've got the joy of also pumping about 2.5' vertically to the cooler. Oil is heavy. I'm hoping the thermostat I'm adding will help resolve any issues that shoving cold oil up to the cooler might cause.

[Fusion Works]

On 914s with four cylinders we use 10AN for front mounted coolers. You can get by with 8AN, but I wouldn't go any smaller and think you would be better off with 10AN. Remember on an oil system, flow is very important. Flow allows the oil to carry heat away from critical parts. I would tray and get all the fitting to 10 AN. That will allow more flow.

You are running a bigger pump than stock VW and you are running more cubic inches. More cubic inches = more heat. More HP= more heat. VW engine are air AND oil cooled. While it is not as critical as a 911, the oil is absolutely essential for removing excess heat from the engine. You won't stress the oil pump by adding in a cooler and remote mount full flow oil system.

I would mount the cooler in the front trunk to assure clean cold air passes through the cooler. Yeah I realize there is more hassle, but it is worth it. There is a reason Porsche mounted the bigger oil coolers in the front of the 911, it does a better job.

[TouringBubble]

I have the cooler in the rear window with two 3" naca ducts feeding air to it. We will see how it works.

[Fusion Works]

I have the cooler in the rear window with two 3" naca ducts feeding air to it. We will see how it works.

Where are you dumping the air that passes through the cooler?

[TouringBubble]

The rear window is louvered.