A Cold Heart for the Camaro - Oil Cooler R&D - Part 1: Stock Review & Plans
For the past seven years the 5th Gen Camaro SS has been a staple of track days at Willow Springs, Road Atlanta, Laguna Seca and just about every other road course in America. Another staple of those track days has been a spike in mild heart attacks as those Camaro SS owners glanced down at their oil temperature gauge to find temps in the 290+°F range. Even off the track, though, a hot day mixed with a heavy foot can lead to oil temp related heart problems for both you and your Camaro.
Everything in Balance
When it comes to modern engines and driving, oil temperatures are a balancing act between hot and cold; thin and thick. When straight-weight oil, also known as single-weight oil (like SAE 30), is cold, it's thicker and more viscous. Higher viscosity means that the oil flows slowly and sticks to surfaces longer. This also means, however, that on cold start-up, it's much harder for the engine to move the oil and thus bearings and wear surfaces don't always get the oiling they need until the engine warms up. Oil that is too thick in cold conditions greatly increases engine wear and makes it harder for the engine to start.
The modern solution to reduce engine wear on cold start-up, while maintaining proper oiling when at operating temperature, is mixed-weight oil. This is the oil you normally find on your auto-parts store shelves with a number such as 5W-30 on the bottle. That "W" in the middle stands for "winter" and denotes how easily the oil flows in cold conditions.
Mixed-weight oil starts out life as a straight-weight oil. In order to make the oil mixed-weight, viscosity-improving additives are then introduced. These additives allow the oil to remain viscous at higher temperatures, keeping the bearings and other wear surfaces lubricated. Put simply, a 5W-30 oil flows like an SAE 5 (very thin) oil in cold conditions, but maintains the viscosity of an SAE 30 (thick) oil once the oil reaches operating temperature. Mixed-weight oil allows lubrication to reach the bearings and wear surfaces of the engine quickly when cold and stay there when at operating temperature.
A Thinning Issue
So, what does all of this have to do with Mishimoto and your Camaro SS? Well, it all comes down to the second number on the oil's bottle. The engineers at GM carefully crafted the LS3 and L99 engines' tolerances to play nicely with 5W-30 oil. What's most important about the "30" is that the viscosity is measured at 210°F. As we've determined, oil thins and becomes less viscous as it gets hotter. While the Camaro's engine is happy with a 30-weight oil at 210°F, at temperatures above 210°F those viscosity-improving additives we talked about earlier begin to lose their effectiveness.
As oil temperature begins to climb into the 290°F range, the oil in the engine begins to "shear" down closer to a 20-weight oil or less. As this happens, the bearing and piston clearances are no longer filled with effective oil. GM's engineers planned for the eventuality that their vehicles would be driven hard and oil temps would climb above 210°F, but there's only so much they could do. That's where Mishimoto comes in.
Heating and Cooling . . . and Heating
Mishimoto is excited to share that we've begun the process of designing an oil cooler for the 2010-2015 Camaro SS. Now that we've gotten the scary technical realities out of the way, let's look at the Camaro's stock oil cooler and how we plan to improve on that system.
The stock oil cooler on the 5th Gen Camaro SS is a common, liquid-to-liquid design that utilizes the engine's coolant to regulate the oil's temperature. This system serves two purposes: to heat the oil to operating temperature quickly, and to cool the oil to the temperature of the coolant once the engine is at operating temperature. The first half of that process is a very important one. The engine's coolant heats up much faster than the oil would on its own. This is another measure, on top of mixed-weight oil, that allows the oil to flow throughout the engine quickly on cold starts and reduce engine wear.
The second half of the stock oil cooler process is where it tends to fall short. To save weight, time, and money, manufacturers utilize the already-existing heat exchanger that is the car's radiator to perform the work of cooling both the oil and the coolant. While oil does not directly flow through the radiator, the coolant and oil both flow through separate chambers of the oil cooler. From the oil cooler, the coolant carries heat away from the oil and dissipates it through the radiator (if all of this is a little hard to follow, check out the diagram below for a visualization of how the stock system works). While this may sound like a simple and efficient means of regulating oil temperatures, the stock oil cooler has its advantages and disadvantages.
Pros and Cons
One advantage, as we discussed earlier, is that the coolant heats the oil much faster than it would just circulating through the engine. It also means that the oil remains at operating temperature throughout normal driving, keeping wear surfaces properly lubricated. The main disadvantage, however, appears when the engine is pushed beyond normal driving conditions.
At the track or during spirited driving, or even just sitting in traffic, the coolant temperature can increase beyond 210°F, the temperature at which the oil viscosity is tested. The main purpose of coolant is to carry heat away from the head, block, and cylinders of the engine to prevent damage. Problems occur when the stock radiator and oil cooler cannot dissipate the heat generated by the engine. That is where a standalone oil cooler comes into play.
Plan for the Worst, Cool like the Best
For the 5th generation Camaro SS we plan to retain the factory liquid-to-liquid oil cooler but also introduce a liquid-to-air oil cooler, similar to the factory radiator. Incorporating the stock oil cooler will mean that the oil will still warm up quickly and should make cold starts as easy on the motor as stock. Once the oil warms up, the Mishimoto oil cooler will take over the duty of cooling the oil within operating temperature.
We plan to mount our oil cooler behind the grill for maximum air-flow and efficiency, while still leaving room for forced-induction intercoolers. In order to tap into the flow of oil, we will be incorporating an oil filter sandwich plate to divert oil into the cooler. To help regulate the oil temperature once hot, we will be offering the oil cooler with both a thermostatic sandwich plate, for those who will both daily-drive and race their cars; as well as a non-thermostatic sandwich plate, for those who plan to primarily race their cars. Finally, as with all of our direct fit oil coolers, this kit will be bolt on, with everything you need to install and go (except oil).
Now that we know how the stock oil cooling system works and how we plan to improve on it, we'll be looking at mounting options. Keep an eye out for the next post and as always, feel free to let us know if you have any questions or comments!
Thanks for reading!