Low oil pressure after fitting oil cooler

[Brigsy]

Evening all.

Installed a mocal oil cooler kit to a megane r26 F4R today which caused oil pressure drop.

Pre oil cooler fitting with oil temp around 80deg, it was doing around 1.5bar on idle, 3.5k rpm 4bar, poss slightly more with more rpm, engine sounds fine so assume its all good where it counts.

After fitting the oil cooler (16 row 235mm iirc) with thermostatic plate, at 80deg oil temp i was seeing 1.8bar on idle, and max of 2.8bar at 3k which does not go any higher with additional rpm. 10/50 millers fully synth oil.

Ive binned it off and went back to oil filter direct to block and pressure is back to normal/previous readings, as not happy with the higher rpm pressure drop.

Due to space constraints im running 90deg bends off the sandwich plate, and 90deg fittings at the oil cooler, takeoffs on oil cooled facing up so no issues with flow direction as far as i know. Hoses from memory are either 1/2 id or 5/8, need to verify.

Is the pressure drop due to restriction through the hoses, bends or oil cooler itself? Is this a common issue on f4r?

 

[dann2707]

May sound stupid mate but after you ran the engine for the first time after fitting the cooler did you fill up with more oil to account for the oil in the cooler?

 

[Brigsy]

I did indeed, i primed up the oil system before starting which fills the cooler as it bypasses the stat slightly. Took approx 1ltr more oil than usual to get to the max, and checked again after running up.

Ive fitted a few mocal kits to other/shitter engines and not had this issue before so bit baffled.

 

[R3k1355]

How was the pressure when cold? Assume it was normal?

 

[Brigsy]

Looking at the datalogs for before and after its down by 0.2bar after fitting oil cooler on initial startup.

Im swinging towards lines restrictive/length of lines at the moment causing the pressure drop.

Im going to log oil temps to see if it needs a cooler for street use, as when driving last night oil temps mirror coolant temps under normal driving.

 

[green]

I’d of thought an increase in length of the oil system would drop the pressure.
I know some people have modified the oil pump to increase pressure.
I’ve had a 16 row cooler fitted for years on F4R Clio and had no problems but it may have an effect on your turbo charged F4R. I’d be looking at modding the oil pump but don’t know how.

 

[Brigsy]

Done a bit of digging and it does seem to be an issue with many cars with aftermarket oil coolers fitted. I guess a lot of people fit them and do not even check pressure assuming all is good.

Its got to be down to the length of the lines or the 90deg fittings. On other setups ive fitted the oil cooler hoses were syraight out of the sandwich plate so no restriction at all. Unfortunately space is real tight on this one so will need to look at another approach if it really needs a cooler fitting.

@NorthloopCup any thoughts on this? Ive seen your battles with F4R oil pressure in the past.

 

[NorthloopCup]

Done a bit of digging and it does seem to be an issue with many cars with aftermarket oil coolers fitted. I guess a lot of people fit them and do not even check pressure assuming all is good.

Its got to be down to the length of the lines or the 90deg fittings. On other setups ive fitted the oil cooler hoses were syraight out of the sandwich plate so no restriction at all. Unfortunately space is real tight on this one so will need to look at another approach if it really needs a cooler fitting.

@NorthloopCup any thoughts on this? Ive seen your battles with F4R oil pressure in the past.

Well if anything, the 90deg fittings would create a restriction and increase pressure, so I wouldn’t worry about the fittings mate. Hoses should be -10. They will contribute to a lower pressure, but they will also increase the flow, so as with everything, always a trade off.

The one thing that I can tell you though for definite, is the f4r is absolutely horrific for making oil pressure. One thing we found was the oil squirt jets stick open and they bleed off pressure. Also, exhaust cam journals wear more than the inlet - again, they bleed off oil pressure.

We found a few ‘fixes’ to help the engine out, but none of them are a permanent fix as items still wear.

On my hybrid engine build I ran a laminova oil cooler setup with no thermostatic sandwich plate (warms engine and coolant up at the same time) on -10 lines, 5w/40 oil, brand new squirt jets and modified oil pump. Had to take the shims out the oprv as it was doing 120+ psi at cold idle. 🤣 Hot idle was the best I’ve personally ever seen on a f4r too (over 40psi from memory).

 

[Brigsy]

Ive been thinking and your right, any restriction will increase pressure. Additional volume of oil needing to be moved and pump cant handle the demand maybe, oil cooler not that restrictive so not helping things.

Do wonder if pressure drop like this without logging has caused a few bottom ends to fail prematurely.

Ive had a similar high cold oil pressure on an r5gtt engine when i shimmed the prv a little too much. Popped the oil filter seal when fired up.

 

[NorthloopCup]

Ive been thinking and your right, any restriction will increase pressure. Additional volume of oil needing to be moved and pump cant handle the demand maybe, oil cooler not that restrictive so not helping things.

Do wonder if pressure drop like this without logging has caused a few bottom ends to fail prematurely.

Ive had a similar high cold oil pressure on an r5gtt engine when i shimmed the prv a little too much. Popped the oil filter seal when fired up.

On a bottom end that’s already seeing low oil pressure will, undoubtedly be put under greater strain and have the potential to suffer from premature failure.

Lol! Even at hot oil temps I was seeing north of 100psi under load until I dropped all the shims out the oprv. Managed to get it to drop to about 70psi iirc at the same rpm load.

 

[Brigsy]

100psi under load when hot is epic. Be good for 10000rpm that😆

 

[dann2707]

I'm wondering if the lines have increased the pressure which is in turn opening the pressure relief valve on the pump? What do they open up at?

Just sounds like it as its not getting over a certain pressure no matter what the revs.

 

[Clio.lee]

It depends where the oil pressure switch is. The 90 will only increase the pressure if the pressure switch is located between the pump and the fitting

 

[Brigsy]

Oil pressure sender is in stock location. Ive just checked the hoses and the i.d is 12mm (an8) wonder if thats the issue.