Reducing engine oil temperatures on track

[Ade 517]

15 minutes ago, Ade said: Thats interesting. Mine would sit in the high 90s on the motorway.

How much accelerating do you do? Only time mine went over 95c was under acceleration at the end of 50 zones

Admittedly I never used to keep much of an eye on it stock as I knew it worked, but when I did log oil temp after 30mins or so would sit in the mid to high 90s. Probably in the summer as car used to live in hibernation through most of winter.

[Church 209]

"Ade had a 99C thermostat on his plate and was still seeing oil temps around 80C" - shouldn't engine oil run higher then that normally? After all, it's not generic coolant even if also partially is what removes heat from engine too as secondary function, & i hav seen posts alongside "You want the oil over 100C so the water can evaporate leaving just lubricant on your components. 105-120c is a good operating range for most oils. "

[Ade 517]

"Ade had a 99C thermostat on his plate and was still seeing oil temps around 80C" - shouldn't engine oil run higher then that normally? After all, it's not generic coolant even if also partially is what removes heat from engine too as secondary function, & IIRC i saw mentioned/reading posts that normally it should be >100C, to evaporate possible water moisture leaving just lubricant on components.

Water boils at 100C but still evaporates at lower temperatures - hence why puddles of water dissappear.

According to Mocal, 80C is the desired min temp and thats why they normally use 80C thermostats, but its a generalisation.

[Rich 378]

8 minutes ago, Church said:

"Ade had a 99C thermostat on his plate and was still seeing oil temps around 80C" - shouldn't engine oil run higher then that normally? After all, it's not generic coolant even if also partially is what removes heat from engine too as secondary function, & i hav seen posts alongside "You want the oil over 100C so the water can evaporate leaving just lubricant on your components. 105-120c is a good operating range for most oils. "

Yes, that's the issue. I want to avoid over-cooling my oil when driving normally. Hence thinking an oil-to-water cooler would be good for me since I have the standard coolant stat, so my water temps are close to 95C most of the time.

[AJ124 118]

@Deacon What temp thermostat are you going to use?

[Deacon 1357]

12 minutes ago, AJ124 said:

@Deacon What temp thermostat are you going to use?

@AJ124 I'm still discussing this with Hel but I'm pretty sure it'll be a 99°c one

[Ade 517]

12 minutes ago, AJ124 said: @Deacon What temp thermostat are you going to use?

@AJ124 I'm still discussing this with Hel but I'm pretty sure it'll be a 99°c one

If hel plan to use the mocal sandwich plate be mindful that its really tight getting the lines out next to the airbox. I had a few issues.

1) first issue was the t stat bolt was rubbing one of the high pressure fuel pump metal line so I had to grind down the bolt.

2)Next issue was the 45 degree connectors coming out the sandwich plate. If the plate moves ever so slightly they would rub on the airbox.

This is another reason I went for mishimoto sandwich plate and bonjo bolts.

[Mark@Abbey M/S 235]

2 minutes ago, Ade said:

 

@AJ124 I'm still discussing this with Hel but I'm pretty sure it'll be a 99°c one

 

 

If hel plan to use the mocal sandwich plate be mindful that its really tight getting the lines out next to the airbox. I had a few issues.

 

1) first issue was the t stat bolt was rubbing one of the high pressure fuel pump metal line so I had to grind down the bolt.

 

2)Next issue was the 45 degree connectors coming out the sandwich plate. If the plate moves ever so slightly they would rub on the airbox.

 

This is another reason I went for mishimoto sandwich plate and bonjo bolts.

Issue with banjo and banjo bolts they cause pressure drop

[Church 209]

Ade: but aren't engine oils (& their preferable working temp range) specific to cars/engines? So imho Mocal suggestions should be secondary, just like tire pressures, where car manufacturer suggestions should be used over tire manufacturer ones ..

LOL, though then again what i quoted is also generalization of sorts, not temp range told by Toyota/Subaru (which also may target more policies for generic daily driven vehicles instead for ones used on track).

BTW, if there is higher temp gradient between ambient & oil (or oil to water in forester type coolers) - that also enhances heat transfer per heat exchanger (per same O2W cooler or per same O2W rad), if i remember right physics.

[Deacon 1357]

As I understand it (and it is a limited understanding I'll happily admit) the issue is not the temp leading to degredation of the oil itself but rather that the higher temperatures lead to problems with the oil pressure. 

I'll happily accept I'm wrong though.

[Ade 517]

2 minutes ago, Ade said:  

I'm still discussing this with Hel but I'm pretty sure it'll be a 99°c one

 

 

If hel plan to use the mocal sandwich plate be mindful that its really tight getting the lines out next to the airbox. I had a few issues.

 

1) first issue was the t stat bolt was rubbing one of the high pressure fuel pump metal line so I had to grind down the bolt.

 

2)Next issue was the 45 degree connectors coming out the sandwich plate. If the plate moves ever so slightly they would rub on the airbox.

 

This is another reason I went for mishimoto sandwich plate and bonjo bolts.

Issue with banjo and banjo bolts they cause pressure drop

Mishimoto have data on their website about the banjos and pressure drop.

Its true banjos dont lend themselves to smooth flow but make them big enough for a given flow rate and the restriction can be made insignificant.

Fwiw mocal also do a banjo sandwich plate, but uses M18 centre hole and smaller banjos, so thats why I went with mishimoto because they are M20 banjos.

Here's their impreza wrx oil cooler (which uses the same mishi banjos) long lines but a specially designed low loss core. 5psi loss through the lot.

[Ade 517]

As I understand it (and it is a limited understanding I'll happily admit) the issue is not the temp leading to degredation of the oil itself but rather that the higher temperatures lead to problems with the oil pressure. 

I'll happily accept I'm wrong though.

When oil gets hot it does degrade but most decent oils like milers can handle excess of 150C without damage.

The real problem is lubricating the big end shells. As oil gets hotter it gets thinner and the film strength reduces.

[Rich 378]

@Ade Do you do anything about draining oil from the cooler during oil changes?

[Ade 517]

@Ade Do you do anything about draining oil from the cooler during oil changes?

Nope. The oil lines and laminova don't hold that much anyway.

If you wanted to be anal you could change the oil, start the engine and let it mix. Then drain half the oil out and put fresh in using two 5 litre cans.

On the lexus lfa I believe they do two oil changes but no doubt that has a few oil coolers...

[Church 209]

Hmm, i wonder what should be oil cooling solution placement if one would want complete self-drain. Most probably - placing cooling rad at loop's upper point? With rad inlets pointing down? Opening it somewhere high to let air in? Preferably on rad itself? Modify rad mounts to easily detach rad & put it higher & easily remount it back after flush w/o using instruments?

[Rich 378]

14 hours ago, Mike said:

Daily driving (not motorway) I see about 86/87c, extended driving and motorway, highest I've seen is low 90s. Track is the only time I see it >100C

I did some logging on the way home today. Mostly B roads with a little dual carriageway. Oil temps settled at mid-90s once it was up to temperature. 96C on the dual carriageway at around 70 was the maximum recorded. Temperatures stayed over 90C even when pottering around town after coming off the bypass.

[Church 209]

One should wait for summer with some hot days, to see logs for "worst case scenario". Imho ambient temps for any cooling solution used may play big enough role.

[nerdstrike 186]

In support of what Church is saying, according to Newton's law of cooling, to a first approximation the rate of cooling is surface area multiplied by the difference in external and internal temperature and a coefficient (which is defined by the radiator material and coolant).

So if it's 10 degrees outside and your steady oil temp is 90 degrees, you have an 80 degree difference.

In summer if it's 25 degrees outside, you would need to increase your radiator size by 23% or so to maintain the same heat transfer (read same power output of the engine) under the same steady load. Conventionally cars just run hotter instead and the coolant heats up until the differential is large enough to compensate.

If you allow a higher target oil temp of 110 degrees, you only need 18% more radiator to achieve the same steady state.

This is a super-crude approximation and overlooks the fact that the engine is not always at steady load, as well as the problems from your cooling system being too good such as slow warm-up and less efficient running under regular conditions. However, we can infer that a relatively small increase in additional cooling can make a measurable difference to your maximum temperatures, and that whatever you're reading on the highway at this time of year will go up by the majority of the difference in ambient temperature. 

@Church - so, that Kin Tza Tza eh?

[Mark@Abbey M/S 235]

20 hours ago, Ade said:

Mishimoto have data on their website about the banjos and pressure drop.

Its true banjos dont lend themselves to smooth flow but make them big enough for a given flow rate and the restriction can be made insignificant.

Fwiw mocal also do a banjo sandwich plate, but uses M18 centre hole and smaller banjos, so thats why I went with mishimoto because they are M20 banjos.

Here's their impreza wrx oil cooler (which uses the same mishi banjos) long lines but a specially designed low loss core. 5psi loss through the lot.

Ade, good information , seems Mishimoto have done some development on the Banjo set up.

[Mark@Abbey M/S 235]

19row -10 cooler holds around 0.32litre fluid.

[Church 209]

nerdstrike: aye, one of my favourite sci-fi movies, where absurdity looks way more realistic due humanity most probably being in future with same faults and as stupid as it is now, not some shiny-lights-button princess & knights fairy tale like eg. starwars

As for rad area increase for heat exchange enhancing .. you left fans out of picture. After all, thermostat / engine load & rpms / ambient temps / car & air speed are not the only variables. Once ECU by sensors detects water too hot (and on contrary, switching them off when still too cold), it kicks in fans and/or dynamically regulates their rpms, rising heat exchange from same rad. As oil2air rads are often placed in front of main rad, extra airflow sucked in by fans should affect their efficiency too.

[Rich 378]

@nerdstrike All true, however it's not quite as straightforward as needing a percentage more cooling. Summer oil temps are actually not much above winter oil temps from my observations. Which makes sense when you consider that most of the oil cooling effect at present is dumping heat into the block which is removed by the coolant. My coolant temp is the same year round since the radiator is adequate to maintain it and thermostatically controlled.

The numbers above are really just to get an idea of target temperatures for oil in normal driving. It seems like around 95C is a good temp to shoot for.

[Ade 517]

@nerdstrike All true, however it's not quite as straightforward as needing a percentage more cooling. Summer oil temps are actually not much above winter oil temps from my observations. Which makes sense when you consider that most of the oil cooling effect at present is dumping heat into the block which is removed by the coolant. My coolant temp is the same year round since the radiator is adequate to maintain it and thermostatically controlled.

The numbers above are really just to get an idea of target temperatures for oil in normal driving. It seems like around 95C is a good temp to shoot for.

I think you'll struggle to maintain 95C steady state but high 80s would be my guess.

[Mike 458]

I'm hoping/aiming for 85c+ for daily driving/coasting on motorway, ideally closer to 90c if possible. Might actually do some research before fitting my oil cooler... blasted impulse buys!

[Rich 378]

4 hours ago, Ade said:

I think you'll struggle to maintain 95C steady state but high 80s would be my guess.

Should be fairly close to coolant temperature, which is around 90C with the stock thermostat.