What is a Piston Ringland?
The “Ringland” are the slots on the pistons that support the rings and their duties. A standard Subaru EJ piston will have three ringlands.
The first Ringland is located between the top of the piston and the primary compression ring. This ring seals out a majority of the heat and combustion gases from the crankcase.
The second Ringland bridges the primary and secondary compression ring. The secondary ring seals out gasses that get past the primary ring. It also scrapes any oil that gets past the third ring of the cylinder wall.
The third Ringland bridges the secondary and third ring, the oil control ring. The oil control ring is shaped completely differently from the two rings. The ring’s design scrapes oil from the cylinder walls and forces it to oiling holes and the wrist pins.
Why do Subaru “EJ” Ringlands Fail?
What causes Ringland failures stem from these pistons and their supporting rings. In the EJ engine, the pistons are manufactured by pouring molten alloy into a mold. The only advantage of having a cast piston is it won’t expand as much when heated. This will allow the build to be tight and quiet for the engine to last a long time. The downside to this is that cast pistons are not as strong and do not hold up well to the severe stresses of a high-performance engine.
Detonation is what physically damages the pistons. Anything that promotes detonation such as low octane fuel, lack of proper tuning, and prolonged hard driving can potentially cause piston Ringland failure.
What causes detonation in the Subaru “EJ”?
There’s a long list of things that can lead to detonation, but here are a few things that stand out on a Subaru.
Intakes, downpipes, exhaust manifolds, and other common modifications require adjustments to the factory tune to run properly. Intakes are an extremely common modification that requires specific adjustments to the MAF calibration to properly monitor the incoming airflow. This is because aftermarket intakes affect the airflow through the MAF housing.
Pretty obvious that a “bad” tune is not ideal. This is why you should research tuners and make sure they not only have experience with tuning a Subaru, but that you are also doing your part to give them accurate feedback and data, quickly implementing new maps and fixes, and following their recommendations closely. People can be quick to blame a tune for their own mistakes.
Because of the high boosted air temps, the intercooler will steadily get warmer as you accelerate which reduces its ability to cool the airflow, a.k.a. “heat soak.” The result of this is higher inlet temperatures into the cylinders, less power from a reduction in air density, and a greater chance of detonation. This is an even bigger problem on vehicles equipped with smaller OEM intercoolers found on the non-STI cars. They have considerably less size and surface area which means they will heat up faster and shed that heat much slower.
Low Octane Fuel
We recommend the only fuel you should ever put in a turbo Subaru is the highest available octane fuel in your area. End-of-discussion.
Oil vapor in the combustion chamber makes detonation and pre-ignition more likely. The two most common sources of oil vapor are the turbocharger and the positive crankcase ventilation system (PCV). The PCV system allows the pressure built up in the crankcase to be drawn through the intake. Turbochargers are much less likely to cause oil vapor issues, but they can if the shaft seals leak due to old age or wear.
Even the STI is not configured to be driven hard for a very long time. That means the other turbo Subaru are even less prepared. It’s important to know the limits of your vehicle in terms of thermal load, and most of that is going to be based on how you drive the car. Driving it like you are on the last 5 minutes of an Indy 500 race with an Evo on your bumper is incredibly fun, but also incredibly inviting to detonation.
“Lugging” the Engine
This builds a lot of load on the engine and also utilizes portions of the ECU maps that may or may not be ideally tuned for it. So much so that Subaru and other OEMs even warn against it in the owner’s manual. Pre-ignition and detonation are more likely to occur at lower RPMs due to the larger window of time given by the slower piston speeds. Although, generally air temperatures are much lower at these engine RPMs which helps to reduce the chance for detonation.
How to prevent Engine Detonation?
Get proper tuning software
Firstly, the OEM tune provided with your turbo Subaru is designed to be pretty conservative and not necessarily the most optimally for performance. Secondly, to properly get your car tuned, you will need to purchase a COBB Accessport. Available to all turbo Subaru models, it provides the correct software for your car to run a proper tune after modifications were made. And finally, getting pro-tuned on a dyno by a reputable tuner would finish off your car to run the best it ever will. We, at P&L Motorsports, have one of the best Subaru pro-tuners around. The one and only JR Tuned.
Take care of the Heat Soak Issues
As air is pressurized by your turbo, it heats up, not because of the heat of the turbocharger, but because when they’re compressed, the atoms in the air are forced closer together and as a result, move faster and have more energy. That energy itself is heat. The more heat we can remove from the system, the denser the air becomes and that’s what helps eliminate pre-detonation, or ‘knock’, allowing for increased output from your system. Your OEM TMIC does just fine at stock boost under normal use, but as soon as you start putting some real heat into it with a higher boost or harder use, it heat-soaks beyond recovery. There are many variables to consider when selecting a proper TMIC or FMIC setup. Your friendly P&L Motorsports representative can help you make a decision and steer you down the right path.
Let your Engine breathe Air, not Oil
The IAG Air / Oil separator (AOS) vents crankcase gasses back to the turbo inlet. The design is based on years of service on racing and high horsepower Subaru’s. The AOS’s approximate 1-liter capacity, fully heated housing, superior breathing, and unique patent pending baffle design sets it apart from the rest.
Q: Why do I need an AOS?
A: In stock configuration, the un-baffled crankcase pressure is re-circulated back into the intake stream.
This can be harmful for two reasons:
- Oil vapor mixed with the intake air effectively lowers the overall octane rating of your fuel. The more oil vapor that is sucked back into the engine, the more likely you are to experience engine knock (also referred to as detonation) that can destroy an engine.
- Oil vapors cause oil & carbon to build up over time. The intercooler, intake manifold & intake valves suffer the worst. This oil vapor can create air turbulence that leads to various running issues.
Q: What are the factors that cause the oil in the crankcase vent system (CCVS)?
A: There are a variety of factors that determine how much oil will be in the CCVS. The most significant of these factors is boost pressure, piston to cylinder wall clearance, and oil viscosity. Smaller factors include ambient temperature, engine temperature, piston ring condition, and valve guide condition.
Q: Are there any risks to using an AOS?
A: If your AOS is properly installed, there are not any risks.
Q: What’s the difference between a catch can & an AOS?
A: Catch cans are an air/oil separator that does not actively drain the collected oil back into the engine. Most catch cans require you to drain the contents out manually. While acceptable on some engines that produce little oil in the CCVS, the Subaru EJ engine is not this type of engine. By nature, a turbocharged boxer engine will produce significantly more oil in the CCVS than other engines of similar displacement.
Don’t Beat the Piss Out of Your Car!
Plain and simple, unless you get properly tuned by a reputable tuner, take care of your heat soak issues with a good aftermarket TMIC or FMIC (top mount intercooler or front mount intercooler), and get a proper air-oil-separator. DO NOT drive it like you stole it or drive full throttle for long periods of time. You will end up being sorry and have to fork over a wad of money to rebuild your motor.
How “EL” and “UEL” Header is Relevant to Ringlands
Let’s take a look into how a header works and what it exactly does for the engine. Simply put, the header directs hot exhaust gases away from the cylinder and into the turbocharger. An equal length header will release gases at an equal rate per pulse, with exhaust gasses from each cylinder leaving the header at the same time. With an unequal length header, gas from the two long runners will remain in the header longer because it will take longer to reach the collector.
This results in lower cylinder temperature on an equal length header, which can help prevent Ringland failure. Another benefit of equal length headers is equal backpressure, which will improve efficiency and overall top-end performance.
The P&L Motorsports Subaru WRX/STI EJ20 & EJ25 Exhaust Manifold Header is a unique design that effectively minimizes back pressure to increase horsepower and turbo output. Incorporating a 4-into-1 merge design, this system features an equal length runner arrangement to help reduce the amount of exhaust gas backpressure, while still allowing for excellent sound output and tone. An equal length design was chosen due to the increased efficiency over the traditional un-equal length stock manifold. Designed, tested, and fabricated in-house from start to finish, this header will increase horsepower output, when combined with accompanying ECU calibration.
Running Fuel Rails and Lines: Series vs Parallel
The Subaru OEM fuel rails are set up in a series, which means each cylinder gets fuel one after another, and not all at the same time. If you are running anything less than 325-375whp, you should be ok with the stock configuration. Once you go over that level, the series rail setup will not have enough volume of fuel to deliver to the last cylinder efficiently. This would cause the cylinder to run lean, and eventually result in catastrophic failure. The P&L Motorsports Subaru Top Feed Fuel Rail and Line Kit would eliminate this issue. Our fuel kit is set up to run as a parallel fuel system, being able to spend equal amounts of fuel on each cylinder, which in turn, makes sure that each injector is seeing the same fuel pressure. The P&L Motorsports Subaru EJ20/EJ25 Fuel Line Kit and Regulator can handle the most demanding high-flow EFI systems and is capable of supporting applications up to 1000 HP. Manufactured with smooth bore PTFE flexible lines and -6 or -8 AN swivel fittings and you have an all-in-one solution for your fueling needs.
Please feel free to contact us with any questions or concerns about your car. We are more than happy to help you out, and more than capable of making your “car dreams” turn into reality.
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4900 Lincoln Ave.
Lisle, IL 60532