-12 or -16 hose

blue82coupe · 12-02-2004, 01:52 PM

When I added a 6"x22" mocal spoiler mounted oil cooler , to my carrera cooler,I used -12 hose. Am I flirting with disaster,or should I switch to the -16. The cooler was added during a 3.6 engine swap. Dan

Chuck Moreland · 12-02-2004, 02:09 PM

The problem with -12 is the size of the hose ends. They have an ID of about 14mm. The factory bits had 19mm ID, which represents about 50% greater flow capacity.

There is a huge volume of oil flowing, check this recent thread on the topic.
Oil Pump Rating

The pump has to work 'hella hard to move that oil, and small orifices make it work even harder. This saps usable HP and shortens the life of the pump. The problem is compounded when you put coolers in series since the back pressure is additive.

This is why I like to use all 30mm metric fittings throughout the oil cooling system, no AN adapters or undersized fittings.

That said, the car has a positive displacement pump which means it will move the same amount of oil despite the small oil lines. It just has to work extra hard to do it.

So do you pull it out and replace it? Up to you. But for anyone starting from scratch, do it right the first time.

blue82coupe · 12-02-2004, 02:27 PM

Chuck. You'll be hearing from me sometime over the next few days. Dan

Tinker · 12-02-2004, 04:24 PM

Blue82,

When I originally added my front cooler, I was running on -12 lines. I had discussion with a few shops and their consensus and comments suggested that since the oil cooling is done on the scavenger side and not the pressure side, it doesn't present much of a problem.

Chuck is (quite) a bit more knowledgeable than myself and ideally you are probably better off with the -16 to begin with but I wouldn't worry to much about it. I don't recall the -12 hose end being squeezed down to 14mm. That seems very small.

It is interesting to note that when I added the factory Carrera finned cooler in the front fender, it came with factory adapters that screwed into the cooler so the flexible rubber lines could connect. If you look at those FACTORY adapters, you will find that their inner diameter is significantly smaller than the hoses that connect. I drilled mine out a few mm to add a little flow without compromising their strength.

Tinker

Chuck Moreland · 12-02-2004, 04:56 PM

Tinker,

The carrera coolers as equipped on the '80s 3.2 cars had welded fittings that actully had 19mm ID fittings. The replacement carrera coolers available today have threaded fittings with 14.5mm ID.

I will correct my earlier post. AN-12 hose ends have an ID that is about 14.5mm. Missed it by that much [fingers held 0.5 mm apart].

blue82coupe · 12-02-2004, 04:58 PM

Tinker,
I'm a Chicken ( as you can see by my avatar). Actually a Rooster. I've started the swap to -16 . I was hoping for a unanimous response....that -12 hose was ok. Dan

Tinker · 12-02-2004, 05:44 PM

Blue chicken,

Don't feel too bad, I also swapped mine to -16 for piece of mind.

If you look at a few of the aftermarket coolers, several of them come with -12 to bridge the hard lines.

Chuck,

Wouldn't that taper in the adapters present a similar problem? The adapter is a Porsche part?

Tinker

Chuck Moreland · 12-02-2004, 07:24 PM

Tinker, I assume you mean the taper in a 30mm to an-12 adapter? I like to eliminate the adpaters too, 30mm all the way.

blue82coupe · 12-03-2004, 03:36 AM

Chuck,
If I send you my existing -12 hose ,will you build-up a new set with -16 , using the old set as a pattern .Dan