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Arouse the DAMPFHAMMER!
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I am wondering if anyone knows how effective the OEM K20/K24 oil cooler/warmer is compared to nothing. I am building a JDM K24A for my Civic and I would like to have some type of oil cooler/warmer like I have on my D17 to help warm the oil up quicker and keep it from getting too hot, but I question the effectiveness of that little OEM thing
It definitely helps to raise oil temperature more quick as it also cools better then non oil-cooler versions built's. I have no before and after measurements, but I know a few K-swapped 2-Liter Chassis, running fast laps at Green Hell at around peak at 106-110 °C oil temperature and main around 98-102 °C, which is acceptable on a 30 °C day. The 2.4 Liter likely doesn't produce more waste heat when it has the same power at flywheel, so the same would apply for it. So my assumption is, for a faster heat up and a more stable oil temperature the K20-oil-water-heat exchanger is worth the effort.

For my DAMPFHAMMER engine, which is in a rear wheel driven chassis, is supported by the by @Lotus mentioned thermostat and a Laminova ECD54-182. This is a result of the possible oil cooler locations, safety, clearance for water pump location and controllability of oil temperature, it is not a must for an DD, but for my race car concept.
 

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I was thinking about this the other day. what would be considered too low of an oil temp? There has to be a limit to how off the wall the oil cooler system can be. I am sure in the Jetsons TV show they were using a programmable cyro oil cooler that was self regulating.
 

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Discussion Starter · #23 ·
I was thinking about this the other day. what would be considered too low of an oil temp? There has to be a limit to how off the wall the oil cooler system can be. I am sure in the Jetsons TV show they were using a programmable cyro oil cooler that was self regulating.
Great question! From all the research I did, I think as long as the oil is up to 140 degrees or so you are safe to floor it. However, the it needs to eventually get hotter than that to burn off condensation and fuel that ends up in the oil, I'd say 180+ degrees would be ideal.
 

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Discussion Starter · #24 ·
It definitely helps to raise oil temperature more quick as it also cools better then non oil-cooler versions built's. I have no before and after measurements, but I know a few K-swapped 2-Liter Chassis, running fast laps at Green Hell at around peak at 106-110 °C oil temperature and main around 98-102 °C, which is acceptable on a 30 °C day. The 2.4 Liter likely doesn't produce more waste heat when it has the same power at flywheel, so the same would apply for it. So my assumption is, for a faster heat up and a more stable oil temperature the K20-oil-water-heat exchanger is worth the effort.

For my DAMPFHAMMER engine, which is in a rear wheel driven chassis, is supported by the by @Lotus mentioned thermostat and a Laminova ECD54-182. This is a result of the possible oil cooler locations, safety, clearance for water pump location and controllability of oil temperature, it is not a must for an DD, but for my race car concept.
Thank you so much for the information! Sounds like the OEM cooler/warmer is likely adequate for a daily driver.

Not sure whether a K20 or K24 would heat the oil more. K20 revs higher but K24 has a longer stroke and balance shafts in stock forum unlike most K20's. I would think the balance shafts spinning through the oil at 2X engine RPM would add measurable heat, but I think whether the engine has piston oil cooling jets or not would probably make much more of a difference than 2.0 or 2.4 liters. Directly spraying oil right at the bottom of the hot pistons would have to add a lot of heat.

I'm also very curious why the European/Australian K24A3 comes with an oil cooler while the USDM/JDM K24A2/K24A does not. Here in North America we see temps varying between -50 degrees and 120+ degrees too so why would they benefit from it but we wouldn't? :unsure:
 

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Arouse the DAMPFHAMMER!
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what would be considered too low of an oil temp?
Depends on a few parameters, like application, cylinder pressure, engine speed, ... and ... and ... and so on. Finally it is all about the tribological performance. At MTU, maybe the oldest engine series producing company of the world, we heated up the engine at 10 % load till oil squirter gallery was opened at a 2.5 bar. This happened at around 80 °C (= 176 °F). These engines endures 80.000 h of WOT, which means 3.5 bar of boost at 1500 rpm (single range oil + electrical preheating of coolant). On a race engine I would do the similar. On a DD multi range oils are used as there is no focus of generic drivers on durability with respect to engine oil temperature. But also here I would see engine speed and load limited as long as oil is below 70 °C (= 158 °F), for example as limit 3500 rpm and 50 % load incl. smooth transient driving. Those so called race thermostats, which opens up at already 72 °C wouldn't follow that procedure in a DD. They are made for not proper designed cooling circuits. My aimed temperatures for oil are 105-115 °C. I choose my oil with respect to that range to have a stabile chemical consistency for e.g. the hill climb application. For an DD I would aim for at least 85 °C. I had customers who bought non-OEM thermostats which opened at around 65-70 °C. I refused to tune those engines, and forced them to by an OEM thermostat.
 

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Arouse the DAMPFHAMMER!
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I'm also very curious why the European/Australian K24A3 comes with an oil cooler while the USDM/JDM K24A2/K24A does not.
Just guessing: customer acceptance if an oil gauge is installed. Otherwise an emission regulation could also lead to have a faster heat up of the oil temp. to get faster in an efficient operational modus. Just guessing...
 

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Discussion Starter · #27 ·
Just guessing: customer acceptance if an oil gauge is installed. Otherwise an emission regulation could also lead to have a faster heat up of the oil temp. to get faster in an efficient operational modus. Just guessing...
Good thoughts. I wonder if keeping temps acceptable during sustained high speed driving on the Autobahn has something to do with that also in the case of the European models. Here in America, we are limited to 85 MPH at the highest and usually around 65-70 MPH and Japan is even lower so that may have something to do with it as well.

I wonder how much the oil cooler actually does help fuel efficiency/emissions. Obviously warm oil is thinner and more efficient, but when I installed a large oil to coolant heat exchanger on my D17 powered Civic I noticed that the oil heated up much faster and the temp was much better controlled, but that had the side effect of causing the coolant to take noticeably longer to warm up since the cold oil was cooling the coolant during warmup, which surely negates some of the efficiency benefits of warmer oil although there was no measurable difference in fuel efficiency either way. I'm sure that's still a good tradeoff for engine longevity though and I like seeing a stable oil temp that's almost unaffected by ambient temp and driving conditions.
 

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Arouse the DAMPFHAMMER!
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I wonder if keeping temps acceptable during sustained high speed driving on the Autobahn has something to do with that also in the case of the European models. Here in America, we are limited to 85 MPH at the highest and usually around 65-70 MPH and Japan is even lower so that may have something to do with it as well.
Good point, definitely if you run your car with 160 mph over the Autobahn, an oil cooler would help to keep things easy.

but that had the side effect of causing the coolant to take noticeably longer to warm up since the cold oil was cooling the coolant during warmup, which surely negates some of the efficiency benefits of warmer oil although there was no measurable difference in fuel efficiency either way. I'm sure that's still a good tradeoff for engine longevity though and I like seeing a stable oil temp that's almost unaffected by ambient temp and driving conditions.
The only thing which really need to be on spot regarding temperature is the oil, as it's properties are somehow bounded to temperature and the cooling water has just to cool. The cooler the coolant, e.g. the less knock will happen. Also from a standpoint of efficiency, oil counts, coolant isn't of that interest in the same magnitude of importance and significance. Concluding in a rough conclusion, oil heat up time is what counts, water heat up has to support this. Therefore the small circuit of the coolant has a major role for emissions, engine durability and efficiency. A smaller volume get faster heated up to aimed temperature to heat up the metal and the fluids to setpoint. So I think it is ok coolant warms up slower.

The trade off is solved by the volume of it and the heat capacity of water is 4.19 kJ/kgK, with anti-freeze (Glysantin) around 3.5 kJ/kgK for a 1:1 mixture. That means a 1:1 mixture takes up 3.5 kJ energy per 1 kg to heat it up another 1 K (°C), e.g from 35 °C to 36 °C. So it is easy to see the volume is a major player in that game. If enough heat flux is available a big heat transfer from combustion into the water is necessary, therefore the moving of the water by the water pump plays also a bigger role. So 3 parameter are left: volume, water content, heat transfer into coolant by a huge transfer surface and an adequat flow velocity through the engine.
 

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Discussion Starter · #29 ·
Good point, definitely if you run your car with 160 mph over the Autobahn, an oil cooler would help to keep things easy.

The only thing which really need to be on spot regarding temperature is the oil, as it's properties are somehow bounded to temperature and the cooling water has just to cool. The cooler the coolant, e.g. the less knock will happen. Also from a standpoint of efficiency, oil counts, coolant isn't of that interest in the same magnitude of importance and significance. Concluding in a rough conclusion, oil heat up time is what counts, water heat up has to support this. Therefore the small circuit of the coolant has a major role for emissions, engine durability and efficiency. A smaller volume get faster heated up to aimed temperature to heat up the metal and the fluids to setpoint. So I think it is ok coolant warms up slower.

The trade off is solved by the volume of it and the heat capacity of water is 4.19 kJ/kgK, with anti-freeze (Glysantin) around 3.5 kJ/kgK for a 1:1 mixture. That means a 1:1 mixture takes up 3.5 kJ energy per 1 kg to heat it up another 1 K (°C), e.g from 35 °C to 36 °C. So it is easy to see the volume is a major player in that game. If enough heat flux is available a big heat transfer from combustion into the water is necessary, therefore the moving of the water by the water pump plays also a bigger role. So 3 parameter are left: volume, water content, heat transfer into coolant by a huge transfer surface and an adequat flow velocity through the engine.
Thanks for taking the time to explain! I always thought of coolant temp as affecting efficiency somewhat more than oil temp due to factors like the richer air fuel ratio and worse fuel vaporization, but obviously oil temp is important as well since cold oil is thicker and creates more drag. I know that hot vs cold oil can make a several HP difference because of the difference in viscosity.

Good point about the volume. If I remember correctly my heat exchanger holds about 1 cup (~250ml) of coolant, but I don't think that's what made most of the difference I saw in warmup time. When I first installed the heat exchanger, I connected the coolant side and then had to get different AN fittings for the oil side because of leaks. For the week or so that I drove it around with only the coolant side connected, I didn't notice any differences in the coolant warmup time. I noticed the coolant taking a little longer to warm up after I connected the oil side.
 
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