Hi, i have a tired 1.7 and am planning to build a 2.0. My question is, what size oil lines can the oil pump handle if i mount an oil cool in the front trunk?

depends on pump

-10 is a good size for front cooler (what i used)
-12 is the bomn. if you're pump can handle it. -12 is also the min size for a six conversion. run them once, and you can handle up to a 3.2

Have -10 going to -12.....

same here....

shoulda gone -12...

but everyone responded AFTER i bought it all LOL

is that so?

i'm running -12 for my 3.6L front cooler ...
Andy

just what ive read....
-12 minimum... and i thought -16 was required on a 3.6....
but i didnt stay at a holiday inn last night tho

i've heard otherwise ...

Andy

cool. cheaper to build the lines now lol

I've had -10 lines running to the front-mounted cooler on my 3.0 six for years with no problem. The oil temp never gets much over the 185° opening point of the external oil thermostat, even in 100° heat and slow traffic. Patrick Mototsports says -12 lines are fine for a 3.6.

None of this has to do with engine size. It has to do with the pump(s).

A /6 has two pumps: A pressure pump (which has nothing to do with this conversation) and a scavenge pump (which supplies flow to the external cooler,among other things). The scavenge pump has a high capacity, but the scavenge circuit is GENERALLY low pressure. -12 lines are used to keep the high flow from creating high pressure. The scavenge circuit has NOTHING to do with the pressure you see on the gauge. Low pressure in the scavenge circuit can't hurt your motor.

A /4 has one pump: A pressure pump which must supply both pressure to the engine and flow to the cooler. I would be reluctant to run lines larger than -10 because the external cooler becomes part of the overall pressure system and a /4 pump is only capable of so much.



To review: -12 lines are used on a /6 to keep pressures DOWN, -10 lines are used on a /4 to keep pressures UP. They are completely different arrangements.

For my 3.6 I'm using -12 on the pressure side and -16 on the suction side

I think you mean -12 on the 'scavenge' side and -16 on the 'supply' side.

It's an important distinction for my explanation above.

Yes, you are right, better to keep it technically correct. I was being lazy.....

I'm using -16 on my supply side for my 3.6 and -12 on the output (or scavenge) side going to my cooler. I got a few responses that this would not work and that I needed -16 (or even -20) lines. Well, it works just fine. In fact, the whole oil cooler system seems to work great. I've run at ouside temps of 90 degrees plus and it controls the temps well.

I agree that the T4 has a single pump, but I'm not so sure about the line size/pressure relationship.

The T4 oil pump pressurizes the oil and sends it to the oil filter, the stock oil cooler, and then to the engine. The oil leaves the pump at its highest pressure. As it flows through the various components friction causes a drop in pressure and the end pressure at the crank, lifters, etc., will be slightly less than pump discharge.

When an external cooler, lines and fitings are added, typically via a sandwich plate at the oil filter, additional flow resistance is being added. Flow through the lines and cooler means additional friction and pressure drop. This pressure drop is then added to the stock component pressure drop to determine final pressure.

Pressure drop through the lines and fittings is directly relateded to diameter. The smaller the lines, the higher the flow velocity is, the greater the friction, the greater the pressure loss. It's unavoidable. Larger lines mean lower velocity, lower friction and less pressure loss.

With a T4, if you want to keep the oil pressure up, I think you should go with larger lines and fittings, say -12, especially if you're running them to a front mounted cooler. And this applies even if the sandwich plate has smaller -10 fittings. These smaller fittings may be a restriction, but it's not necessary to add another 25 to 30 feet of -10 line and its restriction to the system.

Having said all of that, I am still unsure how well a T4 oil pump handles an exterior front mounted cooler.

food for thought-

i have a 38mm oil pump on my type 4...its huge. i have lots of oil pressure even with 30 feet of -10.....

stock pump>? meh... duno if i would go over -10 with that, but im quite sure a shadeck or melling can run -12 no problem (26mm and 30mm respectively)

Disclaimer: I don't mean to contradict the recommendations of people with more actual practical experience with coolers than myself.

In theory, anything in the oil circuit between the pump and the engine oil gallery causes some fluid friction and REDUCES the pressure seen by the bearings. The smaller the lines, the more restriction and pressure drop and the lower the pressure will be at the bearings. You can't increase pressure in the motor with a restriction (e.g. small hose) before the oil gallery.

The 964 oil pump delivers 65 liters per minuteof oil to the pressure side.
The scavenge side delievers 1.84 times that amount.
IIRC, the 76-88 oil pump delivers somewhere around 55 liters per minute on the pressure side with a ratio approximately the same on the scavenge side.

The pressure side is limited to around 8-9 bar by the pressure relief valve.
The scavenge side is unregulated. I talked (internet) to a racer that had installed a
pressure gauge on the scavenge side (Aux cooler, no thermostat) as a test. He had responded to my question after I blew up my aux cooler (a plumbing screw up). He got over 160psi on cold startup. Much of the time the scavenge side is suckin' air, but not at cold start up.....you get the full meal deal.

Probably good to explain why to those that don't have a dry sump system. When cold, the oil from the tank (by gravity) works it's way back to the engine, filling the case with many quarts. When the engine fires up, the scavenge pump is pumping it's full volumetric capabilities until the case is again empty and it starts to suck air. During normal running, the scavenge pump only has to remove whatever oil the main pump has put in the engine which is only a fraction of the scavenge pumps capabilities. During those times with hot oil and a running engine, life for the scavenge pump and lines is much easier.

Respectfully, you are incorrect.

Pressure is not created by a pump, pressure is created by restrictions downstream of the pump.

Look at the fuel pressure regulator in your (fuel injected) car.
Look at the oil pressure regulators in your engine case.
Look at the expansion valve on your A/C.
Look at most recirculating hydraulic systems.

Think about the reason you instinctively put your thumb over the end of a water hose to make it spray by raising the pressure in the hose.

Pumps supply volume, regulators create pressure against that flow.

so, for a type 4, if I run a 38 mm pump, i can get away with -12 lines. I guess time will tell.

I agree. The point I was trying to make is that the pressure is only increased upstream of the restriction. Where you care about pressure in a motor (internal oil passages/bearings) is downstream of the cooler lines.



In each of these cases, the high pressure is upstream of the restriction.



OK, say the faucet is the oil pump and your thumb is the main bearing clearance. I you put a kink in the middle of the hose, will the water spray further? I don't think so.

If -10 lines would make more pressure in the engine than -12, why wouldn't -8 or -6 be even better?

-10 or -12 lines will work with a TIV motor with a high volume oil pump just fine. The most restrictive spot on most of these front oil cooler setups is the pancake oil filter adapter and the associated fittings. That is where I have seen the smallest orifaces in these setups.

There may be some pressure loss due to line size, but real world experience shows that any pressure loss due to line size appears to be made up by running cooler (higher viscosity) oil through the engine (which raises the oil pressure).

When we ran with a TIV in the track car with a front mounted cooler, we used -12 lines because that was what was recommended by other 914 guys 19 years ago. We had no oil related problems in the time that we ran the car in that configuration. (2 drivers, track only car).

If I was going to recommend line size, I would go with -12 line.