Wunderladen Racing's Oil Pan Baffle - A Look Into Design

Recently we've started a deep dive study of the Honda L15B7 engine found in many newer Honda models. One note we made immediately was the lack of any baffling in the oil pan!

Before we go into the how we're going to cover the why. So why is no baffling a concern and what are the possible consequences? Most production car engines use what is called a wet sump oiling system. This means that all of the oil is stored in the bottom of the engine in the oil pan, also referred to as the oil sump. The oil pump sucks oil from the sump and feeds it to the engine to prevent metal on metal contact between moving parts. Once the oil has done its lubrication job it then drains via gravity back to the sump and the cycle repeats. Since there is always oil being pumped throughout the engine and there is always oil draining back, the pan is never truly full while the engine is running. As engine RPM increases so does oil pump speed so more oil is sucked up. Since gravity doesn't care about engine RPM the rate at which oil drains back is largely unchanged, so as RPM increases the operating oil level in the sump decreases.

The problem arises when we get into sport driving or driving on track. When taking turns at high G's the oil in the sump will slosh in one direction or the other. On left hand turns the oil will slosh right, and on right hand turns the oil will slosh left. The combination of lower operating oil level at higher RPM and the sloshing in one direction or the other means there is a possibility of the oil pump pickup tube becoming partially or entirely uncovered. When this happens the oil pump sucks up air, which compresses, lowering oil pressure, and thus oil supply to the engine decreases. The best outcome in these scenarios is accelerated engine wear, the worst outcome is a sudden catastrophic failure of moving parts that did not receive sufficient lubrication.

So what can we do to save our engine from an untimely death? We can add a baffle of course! The purpose of a baffle is to allow oil to flow towards the pickup tube and restrict oil from flowing away from it. This helps create a localized higher oil level around the pickup tube which decreases the possibility of the pump sucking in any air. It's a simple device in theory but executing that job effectively in the real world is not the most straightforward deal, so we figured we'd give a sort of "behind the scenes" look into how we've developed our pan baffle as well as how we'll be validating it's effectiveness in future posts!

To start we'll look at the factory pan. The factory pan features a windage tray (not to be confused with a baffle) at the top. The purpose of a windage tray is to reduce the amount of crankshaft windage, or more simply the air "gusts" or "disturbances" created by a spinning rotating assembly, that interacts with the oil in the sump. When windage interacts with oil it turns the liquid oil into an oil/air froth mixture. If the pickup tube sucks up froth it has the same result as if the pump ingests air. So the factory pan does an okay job of reducing how much windage can get into the sump, although that could also be improved *wink wink*.

Once we remove the windage tray we can see the pan is relatively open. The shape of the pan is one that is fairly rectangular and much longer than it is wide; also the floor on the left side is raised to allow the exhaust to pass underneath the engine. The pickup tube sits in the area highlighted in red, which is good because that puts the pickup tube fairly central in the area of the pan that is deeper.

With this information we can go forward with measuring and designing. Since the pan has many organic faces that are not easily measured with conventional measuring tools we opted to use our 3D scanner to scan the inside of the pan. With scan data we are able to accurately model a baffle that will closely hug the walls of the pan, making it more effective in controlling oil flow.

Since we wanted to improve the windage tray as well we decided to do a windage tray/baffle combo that replaces the factory windage tray. This meant we would be mounting the baffle using the factory windage tray mounting points. With those mounting points located we can use the scan data to create a windage tray which covers more area of the top of the pan to reduce the amount of windage which can get past it. The large slot on the right is to clear the factory pickup tube and the the bent slats covering the left side are there to provide effective drain paths for oil but keep windage from passing through easily. The small slot on the left is for the trigger wheel on the crankshaft to pass through the windage tray.

With the new windage tray complete we can start working on the baffle plates. We decided since the pan is much longer than it is wide we would focus on baffling which would control oil flow in the lateral directions as there likely won't be any issues with slosh in the aft direction, and there won't be any starvation in the fore direction (under braking) because the pickup sits right against the front side of the pan. After identifying a left and right location for these baffles we once again used the scan data to shape them and figure out how much clearance is adequate to allow some oil to flow past but not large amounts in a short period of time. This helps ensure that all oil is drained when the oil is changed.

On the right side baffle there is a cutout for oil pickup tube clearance just like the windage tray has. Below that cutout are 2 holes which are covered by trapdoors; these trapdoors allow oil flow in one direction but not the other. In this case we are allowing oil to flow from the right cavity into the center cavity but not from the center to the right cavity. Oil can still flow both directions through the pickup tube cutout but the cutout is located high enough up that if oil is flowing through there then the pickup tube is definitely submerged in oil.

On the left side baffle there are 3 semicircles at the top, this allows oil at the top to pass across the baffle when oil needs to flow into the center cavity to get to the pickup tube. This is important since the left cavity is where the floor of the pan is shallow so allowing oil to pass at the top of the baffle ensures there is adequate flow into the center cavity, this is similar to the pickup cutout on the right baffle, where flow in both directions here is fine because it means the pickup is definitely submerged. Again, on the left baffle there are 2 trapdoor holes which allow oil at the bottom of the baffle to flow from the left cavity into the center cavity but not vice versa.

Speaking of trapdoors, we opted to use rubber trapdoors as opposed to door hinge style units because they are simple, don't make noise in operation, allow the baffle to easily be disassembled in case it needs to be cleaned, and are easily replaceable if they are ever damaged.

So here's what our completed prototype baffle looks like! We went back and forth about a lot of details but ultimately this is the design we settled on and we are excited to get it on our development car to see how much of a difference it makes. In the next chapter we'll cover all the details of how we validate the baffle!