When engine output rises beyond a certain threshold per liter of displacement, an oil cooler becomes more important, critical even. There is a lot to the selection and installation of an oil cooler, so to find out more, we caught up with Zac Beals, a technical sales representative with Setrab USA, a Swedish company that specializes in a full range of heat exchangers and radiators for OEM applications, and oil cooling for motorsport. There are right and wrong ways to add an oil-cooling system, based on application and a number of other factors, but there are two key tenets to follow when adding an oil-cooling system: get expert help and don’t skimp on materials.
“Oil is the only thing preventing metal-to-metal contact, and any high-performance engine is designed with its own optimal oil temperature range based on how much work the oil is doing in that system,” Beals said. “The demands on the oil in a high-revving turbocharged four-cylinder are different from the demands on the oil in a naturally-aspirated V-8, and the differences only get more specific from there.
“What we do know for sure is that most generally, temperatures in excess of a normal operating range will break down the ability of the oil to do its traditional lubrication job,” Beals added. “A rule of thumb is that every 20 degrees in excess heat will half the life of the oil. This has a related effect on every internal component the oil touches.”
An oil-cooling system consists of the fittings and hoses to get the oil out of the engine to the cooler itself and back into the engine. It seems pretty simple, right? Not exactly.
Any fluid flow is restricted by the smallest orifice it flows through. The size of the fittings, the length of the lines and bends in the plumbing system can affect oil pressure and flow. The range of common plumbing sizes range from a AN -6 to a -16, with the majority of fittings falling somewhere in between at -8, -10, -12. For an in-depth story on AN fittings, see the Understanding Performance Fittings – Straight and AN Threads vs. Tapered Thread from March 2017 Speed News Article.
“Finding the ideal plumbing size is a matter of considering the oil flow at the expected RPM in your most demanding situation, considering the distance from the oil source to the oil cooler, how many bends the oil lines might make, whether oil supply is being accessed on the pressure side or return side of an oil system, and can be further determined by the type of oil system, whether wet or dry sump,” Beals said.
There is no one-size-fits all for the plumbing, which also is true for the heat exchanger itself. The efficiency of a heat exchanger is measured in BTUs per hour. What’s really nifty is that any heat relieved by an oil cooler is relatable to some amount of horsepower that is not lost as waste heat in the engine. Beals said the rule of thumb is 1 horsepower equals 2,544 BTU per hour.
To find the right size heat exchanger, the first consideration is power output, then allotted space for mounting it and how the vehicle will be used, and this is where good components are critical. Cheap oil coolers can result in either low oil-pressure drops with poor performance, or adequate performance with extreme pressure drops. Properly designed and planned oil cooling systems can approximate or come close to zero net pressure loss.
To find a suitable place to mount a cooler, Beals advised mounting it on as many points as possible, and isolating it from vibration using dampened mounts. Further, chassis mount points should be such that they vibrate on the same plane, such as a radiator support. If you mount it on different planes of motion, like a linear frame rail and a lateral radiator support, you could end up tearing the mounts off with chassis flex.
It’s also a good idea to flow oil through the filter before routing it through the cooler. Doing it that way reduces restriction by filtering warmer, thinner oil and supplies clean oil to the cooler.
To prevent untethered oil hoses from “whipping,” secure them as close to the cooler as possible. Whipping can stress the oil cooler connection and lead to fatigue over time. For fittings, minimize the severity of bends to make the smoothest curves possible. For instance, don’t use a 90-degree fitting where a 45-degree fitting will do.
While trying to keep the heat exchanger as close to the engine as possible, you also should mount it in a position to maximize air flow. A heat exchanger should be placed most ideally to face directly into the oncoming air stream and, just as importantly, there should be a proper path of exhaust from the rear of the heat exchanger. If you need to use a cooling fan, it’s better to pull air than push it.
“One oil radiator may look similar to another, when there can actually be significant engineering and manufacturing differences between them,” Beals said. “True cost of ownership is really illustrated by the difference between paying less for a less expensive, poorly-engineered and manufactured oil radiator versus investing in a good value.”
Image courtesy of Setrab USA
Contributed By: Enginebasics.com
To put it as simply as I can, an oil cooler is basically a radiator with oil running through it instead of water. Oil coolers are an important tool in keeping any well running motor continually running well even when pushed to the limit. Maintaining a proper oil temperature is important not only to keep the oil at its proper lubricating state, but also to aid the radiator in keeping the motor cool.
When surrounded by Porsche owners, sometimes we hear of “the good ole air cooled days” of Porsche motors. I know that even I thought this was incredible that these high performance motors could stay cool with no water-cooling, but just air, but the name hides the real story. The reality is that these motors ran upwards of 12 quarts of oil, some even as much as 16 quarts, with very large oil coolers. In reality these motors should have been called oil-cooled motors instead of air-cooled. This goes to show us how important an oil cooler can be to cooling a car.
Oil coolers come in many sizes just like radiators. Choosing a proper size is based on a few factors:
1. The capacity of oil in the system
2. The power output of the motor
3. The amount of air flow and space for the cooler
4. The size of the radiator
Each of the following above will play a key roll in deciding the size of oil cooler you will need for your car. As a basic rule of thumb, most drivers will add as big of an oil cooler as can fit in a space that receives good airflow, and then add a thermostat so that the oil can be kept at a proper temperature.
The oil cooler is designed to come in a one pass, two pass, or even triple pass design. This means the amount of times the oil will pass across the length of the cooler before it is aloud to exit. The idea being that the more passes the oil makes across the cooling front, the more heat the oil will be able to dissipate. Another important part of the design is inlet and outlet size. Be sure to choose a size that will not be too small and restrictive, as this will cause a drop in oil pressure. Most find that -8an or -10 an size fittings are sufficient. Also be sure to try and minimize length and number of bends in the oil lines as your run them to the coolers location.
The best place to install an Oil Cooler is where it can receive a maximum amount of airflow, there by making the cooler as efficient as it can be. Most users know this, but I feel it needed to be stated anyway. Next comes running the lines to the cooler from the motor. The best place to tap into the oil supply system is at the oil filter. This is because the filter is just after the oil pump so the oil supply will have adequate pressure to move through the lines and cooler efficiently. Also this gives the oil cooler the opportunity to cool the oil before it is used by the engine, thereby making sure every part of the motor receives cooled oil at the proper temperature. Two of the best methods to adding the oil cooler lines to this part of the motor is by either a:
1. A sandwich plate
Sandwich plates are specific to your application but a quick search on amazon will show you what is out there for your motor:
2. Filter Relocation Kit
1. With a sandwich plate you are basically putting a piece of metal with an input and output barb for the oil cooler, that is sandwiched between the block and the oil filter. This is an easy and great way to add the outputs you need when adding the oil cooler if you have the space to add a sandwich plate on the block.
2. A Filter Relocation Kit relocates the filter to another area. So why do we care about relocating a filter when we are talking about an oil cooler? With a relocation kit you use an adapter to screw in where the oil filter was on the block to run lines to another location where the filter will be. What this does though is gives us output lines, so that instead of running right to the oil filter, we can run to an oil cooler first and then to the filter and back to the block.
A car motor is happiest when it has good, clean, lubricating oil running through it. To do this oil wants to be between 180-210 degrees Fahrenheit. If the oil is too hot, it will start to break down and separate causing the oil to thin, and the oil pressure to drop to dangerous levels. Having oil that is too cold can be damaging as well since the oil will not be up to temperature and not at its proper viscosity level. The best solution is to add a thermostat controlled oil cooler. What the thermostat does is keep the oil cooler closed, and out of the loop, so that oil can be quickly brought up to temperature. Then the cooler is variably opened to maintain proper oil temperatures. If you opt to not install an oil cooler thermostat, just be sure to warm your car up a little before driving to give the oil time to heat up to a proper level.
Some of the brands we have trusted for our oil cooling duties here at EB have been the following:
You should now understand the basics of an oil cooler, and be able to install one on your car. If you have any questions or comments about this or other articles found here on enginebasics.com, be sure to contact us.
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