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Larger oil cooler

Posted: Thu Sep 26, 2019 4:26 am
by scociu
I am looking into options to install a larger oil cooler as the slightly larger than OEM Mocal unit I have now is not up to the task. Oil temp (Stack oil sender and gauge) constantly reaches 120 C after a couple of hot laps.

After reading some articles, I concluded that I want a radiator with more rows instead of longer rows, to minimize the pressure drop. Basically a taller one mounted in front of the water radiator.

Two questions:
1. Am I right to assume that I need to increase the oil quantity I put in the engine by the difference in capacity between the two radiators?
2. Will the dip stick reading be still relevant? Or, in other words, does the oil in the radiator partially drain back to the sump when the car is stopped?

Re: Larger oil cooler

Posted: Fri Sep 27, 2019 2:37 am
by MD
First you need to tell us if it is a dedicated track car because too much cooling will be detrimental to a street application. Failing that, just switch to a full synthetic oil which will handle that temp and do nothing else.

Re: Larger oil cooler

Posted: Fri Sep 27, 2019 3:33 am
by scociu
Yes, the car is used exclusively on track.
Already using a full synthetic oil. Amsoil, but i would prefer not to turn the thread into a which oil is better debate.

Re: Larger oil cooler

Posted: Fri Sep 27, 2019 1:29 pm
by KevinR
Main issues with high oil temps on a good quality oil is the effects on rubber seals. ( from what I have been told) . Out of interest how long does it take to get to that temp ? What type of radiator you using ? ( for water) . What's the size of your pipe work? And the ID of your fittings.
Jims book had great info there.
I never knew the longer thinner cooler drove down the pressure as I run the BMW M3 rad which is very thin and firs in the bumper registration plate slot . I cut bumper out and used mesh. My min diameter on fittings I think is 8mm and 10mm on pipe. I need to check . Even on the hottest race days in SA with 50 degree track temp I got to 110 degrees. I also run a thermostat modified mocal filter adaptor.
As far as I know the group 1 race GTV 3.0 that race 2hr indurance races in SA in extreme heat were not allowed coolers. They did have much thicker water radiators and deeper front spoilers to get air in.

Re: Larger oil cooler

Posted: Fri Sep 27, 2019 1:45 pm
by MD
Two things:-

The brand of oil is largely irrelevant. Penrite is just an example commonly used here is Oz.
The quantity of oil required is the usual capacity of your sump PLUS the capacity of the oil in circulation outside of the sump.

You should mark your dipstick to reflect this new level on initial cold engine fill.

Re: Larger oil cooler

Posted: Mon Sep 30, 2019 12:44 am
by scociu
KevinR wrote:
Fri Sep 27, 2019 1:29 pm
Out of interest how long does it take to get to that temp ? What type of radiator you using ? ( for water) . What's the size of your pipe work? And the ID of your fittings.
Jims book had great info there.
It takes 2 hot laps to go above 120 deg. That would be 4-5 minutes of running.
Water radiator is way larger than stock. I estimate 50% larger capacity. Water temp never goes above 95 degrees.
I would have to check the size of the oil cooler pipework.

MD wrote:
Fri Sep 27, 2019 1:45 pm
The quantity of oil required is the usual capacity of your sump PLUS the capacity of the oil in circulation outside of the sump.
You should mark your dipstick to reflect this new level on initial cold engine fill.
Thanks for confirming!

Re: Larger oil cooler

Posted: Mon Sep 30, 2019 12:56 pm
by MD
A number of things are not known regarding your situation. Some photos of your installations would help diagnose your problems.

Info we are looking for:-

1 I must assume that your engine is correctly tuned. Simply running lean mixtures will raise temperatures. Confirm state of tune.
2 Are you using an electric water pump or the original one. Are the original pump impellers sound or worn/ damaged.
3 If it is an aftermarket radiator, what is the fin density of the raditaor. Is it greater than 12 fins per square inch.
4 Have you tested the thermostat for full opening
5 Is the radiator free flowing with an absence of mineral deposition in the coolant galleries
6 Is the water pump belt slipping
7 Where is the thermo couple temp sender unit fitted to kick the fans in. On the radiator, thermostat, engine head.
8 What temperature does the switch kick in the fans. Consider changing the sender to one with a lower temperature fan trigger to start the fans earlier and help pull the temperature back sooner.

Regarding the oil cooling, tell us more about the dimensions of your existing cooler and its exact location.

Without this info, we are trying to diagnose the colour of the cat in the bag. Only Kevin could do that after after a six pack of Heineken :D :D

Re: Larger oil cooler

Posted: Tue Oct 01, 2019 9:45 pm
by 75evo
What about air flow? I’m just afraid a bigger cooler may mean lower oil pressure. If you get rid of the CF3 catted headers and vent the hood, the could solve engine bay heat. Then a repositioned oil cooler, in front of the radiatior would ensure the airflow is good.

MD, any chance polish gherkins might be stuck in the oil cooler passage ways? :mrgreen:
Oh I didn’t know Penrite oil was established in 1926, were you around 16 that year? :wall:

Re: Larger oil cooler

Posted: Tue Oct 01, 2019 10:29 pm
by MD
Hey Zeefa. Yes I was around a lot of things at that time but mostly hot chicks trying to entice them with my gherkin. 8) :mrgreen:

Re: Larger oil cooler

Posted: Thu Oct 03, 2019 10:05 am
by Jim K
I didn't hear anyone ask about bearing clearances. Its the biggest factor in oil heating.

Jim K.

Re: Larger oil cooler

Posted: Sat Oct 05, 2019 7:04 am
by 75evo
I believe his engine is standard, so factory clearances. Are you saying it also depends on which on the factory allowed spectrum his bearing clearances are? If only the tighter end, temp increase will be significant? Usually for me if plastigage says it’s within spec, I slap it on and go. I won’t bother getting all the clearances to either end of the allowed factory limit. Like if you go towards the looser end of the allowed tolerance it would lower oil temps?

Re: Larger oil cooler

Posted: Sat Oct 05, 2019 11:02 pm
by Jim K
If you restrict oil flow (tight clearance) oil spends more time in contact with hot surfaces, it therefore heats up more. Loose clearance allows faster oil flow and the heat is transferred away with a larger oil volume. Which brings us to another related discussion: what do you prefer, higher oil pressure or higher oil flow? The purpose of reworking the pump is to increase oil volume. Bigger bearing clearances allow this higher flow and the result is lower oil temps with lower pressure. Notice also -if you are knitpicking- that higher oil pressure detracts from power available -whatever number this may be. I like max hot pressure to not exceed 4-4.5bar (~63psi) and idle can be whatever it sets to. My blocks are align-bored, main bearings are .04-.05mm and rods .05-.06mm. This is for a street/trackday engine. For race jobs, a good rule of thumb is .001" for every 1" of journal diameter, or .01mm for every cm in metric. I have seen ungodly clearances in std new engines, as low as .01mm and as large as .1mm!! These were production engines, so don't believe factory manuals! To close this, I believe align-boring and crank checking/straightening to be the most important factors in engine longevity.
Will someone please read this to MD? Make sure he understands...fart once for 'yes' and 14 times for 'no' -make sure windows are wide open! :wall:

Jim K.

Re: Larger oil cooler

Posted: Mon Oct 07, 2019 1:06 am
by scociu
MD wrote:
Mon Sep 30, 2019 12:56 pm
I must assume that your engine is correctly tuned. Simply running lean mixtures will raise temperatures. Confirm state of tune.
Good point. An AFR vs RPM chart i have shows the mixture starting at 13 and enriches to around 12 at the top end. It is fairly old though, car got a few bits that could affect it since then: new (OEM) injectors, JK 10.3mm lift camshafts and tune adjustment since then. So it would be a good idea to redo it.

Regarding the oil cooling, tell us more about the dimensions of your existing cooler and its exact location.
It is a Mocal unit: 19 row 235mm matrix.
75evo wrote:
Sat Oct 05, 2019 7:04 am
I believe his engine is standard, so factory clearances.
Correct.
I attached a photo showing its current location. It is not ideal in terms of air flow.
Larger photo here: https://drive.google.com/file/d/1UawzOk ... khVRv/view
f9880e18-3e6d-4a55-9034-2c63eb6ea83e (1).jpg
f9880e18-3e6d-4a55-9034-2c63eb6ea83e (1).jpg (165.44 KiB) Viewed 640 times

Re: Larger oil cooler

Posted: Mon Oct 07, 2019 4:49 pm
by 75evo
Well Sociu from what JK has said the factory build itself COULD be suspect as far as bearing clearance goes. Might be ok for a street engine, but won't last very long as a race engine. Who knows...maybe you have an engine with a very tight bearing clearance, within spec, but on the tight side. I'm not sure if it's worth the effort to tear it down though. Maybe if you have a spare 3.2 for a future build. Although If you had a spare, I'd as OKTech to build you a 3.7 :)

But I'd definitely go with a repositioned big local cooler