Inside an Oil Pan at 9,000 RPM
By Carlo "Ollie" Volpe
When you are dealing with a racing engine, it reinforces the axiom “that there is nothing new under the sun”! There are factors that affect the efficiency and horsepower output of an internal combustion engine that will always be true. Having been around drag racing for more than 50 years I’ve had the opportunity to see the same tuning and engine building “tricks” be rediscovered more than a few times. If it increased engine longevity to pre-heat an engine in the 1960’s it still helps in 2014! However, the method by which you accomplish the task is different and hopefully easier or quicker.
I had the pleasant experience of being able to work at a great company, for a good friend, on assignments that didn’t seem like “work”, for a big part of my career. My good friend, Dick Moroso, who I met in 1962, succumbed to cancer in 1998, and he has legions of friends who still miss him. His son Ricky continues with the family passions for racing, fast cars, and manufacturing innovative race parts. Dick hired me from Reher Morrison Racing Engines in 1984 to develop race components in his R&D department, and as they say “the rest is history”!
The oil pan test that you're about to watch was conducted at Bob Ingles’ shop in New York, December 1996. Until now only a very few racers and engine builders have had access to the information, or been able to view, what is contained in this video. Although it is almost 20 years later the dynamics of what occurs inside of an oil pan is the same now as they were then, and the results will also be the same! The engine that was used was one of Bob's NHRA Pro Stock bullets, except that it had a little less compression ratio than a National-Event race engine. It was a power plant that he used to try different cams, and cam timing. To enable this, the pistons had more notch than normal, ergo the slightly lower compression ratio. The pan was Moroso's latest design NHRA Pro Stock unit, identical to the pans that Warren and Kurt Johnson had debuted that September, at the NHRA Indy Nationals. The entire test took 3 days. We spent the first day experimenting with camera and light placement, as well as watching where the oil naturally wanted to go. The next 2 days, based on what we saw, we tried to force the oil to go where we wanted it to go, and thereby increase horsepower.
Once the pan was built, Bob Mayerle at Pro Glass, built the dies to mold the clear
Glass panels that were installed on; both sides, the complete front, and under the
rear pickup tube. We had conducted similar tests in 1986 on Moroso's dyno.
The main difference was that originally we used a SBC pan core, with angle iron
corners and flat sheets of Lexan for the front and sides. For the latest test we
utilized a complete pan with all of the correct dimensions, including depth, width, corner radii, plus the exact inside treatment as an actual race pan. This gave
us a chance to see how different radii effect oil control.
Throughout this narrative there will be descriptions of events occurring inside the oil pan. These will be accompanied by a time on an imaginary clock. Imagine that there is a clock mounted on the front of the crankshaft and with the hands being centered on the crankshaft. Therefore when 6:00 is mentioned, it will be straight down below the crankshaft. Nine O’clock, as you are facing the engine would be on the left side (the actual right or passenger side) of the engine ½ ways up.
This is a brief description of some of the features and benefits of this pan which will make it easier for you to follow the path of the oil. I call this a 1-2-3 pan. There is a 1"
radius in the top right side of the pan, a 2" radius on the bottom right side, and a
big 3" radius on the bottom left side. The pan has 4, radiused inlet, pickup tubes,
placed almost a full 1/2" off the floor. The pickup tubes are located in the center
of the pan (left to right) under the #2, #3, #4, and #5 main caps. The rear three tubes had a baffle behind them, running from the right wall, straight across to the
wrapper/backstop where the tubes exit the pan. These baffles create a
"segregated sump" effect with one stage of the oil pump drawing from each of these little sumps, except for the front pickup tube which shared the sump with
the second pickup tube. As the left side of the pan comes across, at the bottom
of its 3" radius, it becomes a sloped down, overhanging roof, covering the pickup
tubes. There are 4 louvers in this overhanging roof, one by each pair of
connecting rods. There is an open weave, wire cloth screen that starts on the left
side of the pan, about 3/4" off the floor, goes across the bottom, then curves up
on the right side of the pan, ending 1" down from the pan rail. There are 3
passive scrapers bolted to the screen at approximately the 6:00, 7:00, and 8:00
position. They are attached to the screen at a 60-degree angle tangent to the oil
coming off the crank. Whatever oil isn't caught by the front of the scraper, is
sucked through the screen on the backside of the scraper, by the low pressure
area caused by the 60-degree angle. Let's watch the video.
This view is into the front of pan, right side kickout pouch, before the engine is
started. Remember that since we are looking in the front of the pan, the RIGHT
side of the engine will be on the LEFT side of your TV screen. Pickups run
down the center of the pan, under an overhanging floor with louvers. Two of the
scrapers bolted to the screen are visible. It's a good idea to pause the tape and
get oriented to where all of the oil pan components appear on the screen before
the testing starts. You can see the baffle that is behind the second pickup tube.
The dark line about a 1/4" down from the top of the baffle, is the oil level.
The engine starts. Observe how quickly the oil level drops. Though the
pickup tubes are almost a 1/2" off the floor the oil level at all times is only about
an 1/8" deep. This is due to the radiused inlets on the pickup tubes. If you just
have a milled slot in the pickup tube, the sharp edge of the milled slot, which is
found in almost all other manufacturers’ pickup tubes, will separate the "boundary layer.” You will suck only air until the level of the oil is higher than the sharp edge in the milled slot. That is why oil pans without radiused pickups need to have the pickup tubes mounted so close to the oil pan floor. With a radiused inlet in the pickup tube, the oil is scavenged from the pan in a slurry (mixed air and oil), right off the floor, and separated in the dry sump tank, like it should be.
These next few minutes are the warm up period for the engine. While you are watching this video I will point out actions that I think are very important, and I’ll ask you to observe. These events will help you to understand the internal dynamics of an oil pan and therefore draw conclusions to aid you in developing a theory to design YOUR perfect oil pan. Notice the amount of oil, running like a river, from the scrapers. Even at a low RPM there is an unbelievable amount of oil being pulled from the rotating
assembly by the passive scrapers. The way that the pan is configured now, the
scrapers are more than an inch from the rotating assembly. Take a look at the
"rain" coming down on the right side of the pan. Can you see the oil "pinging"
across the floor of the pan from the right wall to the pickups in the center?
Putting heat in the engine and pull to 7,000 RPM
Putting heat in the engine and pull to 7,000 RPM
Putting heat in the engine and pull to 7,000 RPM
Notice during these pulls that as the RPM goes up, the point where the oil exits the rotating assembly moves higher up on the right side of the oil pan. At high RPM the
oil wants to stay on the crank until it reaches the pan rail. Notice the dark sections in the cloud of oil coming off the crank. These heavier quantities of oil are located at the scrapers. This gives visual proof of the effectiveness of the scrapers. Notice once again the river of oil coming off of the scrapers, even though, at this time, they are far from the rotating assembly. Once the engine reaches about 6,000 RPM, the oil follows a path that looks like a counter-clockwise rotating cloud that starts at the pan rail, runs across the top of the kick out pouch, hits the 1" radius in the top right corner, is pushed to the bottom right corner, where the 2" radius directs it across the pan floor, under
this is a view through the window in the right side kickout pouch.
You should pause the video and get re-oriented to the location of the various components on the screen. Find the pickup tubes, under the roof, high off the floor, with baffles behind them. Can you see the louvers in the overhanging roof? Once you start the tape again, you can see the oil coming through the louver, making a U-turn in mid-air without even hitting the floor, and going right out the pickup tube. As the pull commences, the first scraper is working, sending oil in low, down in the pouch. As the engine RPM rises, the next 2 scrapers start working, flinging oil right at the window, causing it to appear as if there is a cyclone inside the pan. As the RPM climbs it causes the oil to come off of the rotating assembly higher, up at the pan rail. In the last few seconds before the pull is terminated, the oil begins to follow the intended
pattern. You can see it running down the glass in sheets, hitting the bottom
radius, and exiting the pickups. In a future test I'd like to hold the engine at this
RPM for a little longer, so that this side view can better illustrate how well the oil
is controlled at high RPM.
After viewing the tape a few times Bob and I discussed changes that we thought
might help to better control the oil in the engine, and possibly increase the
horsepower. We were amazed at how much oil came off of the rotating assembly
up high, at the pan rail, especially at the high RPM where a drag race engine
spends most of its time. He suggested that we install a block high pan scraper,
like the ones that were so popular years ago. A lot of racers stopped using them
because they took so long to fit. Working upside down on a dyno stand, I didn't
even want to tackle that project! Ingles theorized that since we had multiple
scrapers in the bottom of the pan, the one at the pan rail didn't have to be fitted
as close as originally thought. He took a fitted scraper from a similar engine, tried
it on our dyno engine and said that it fit within a 1/4" of the rotating assembly. At
least it was something that stuck out at the crank parting line, to more easily direct the oil into the kickout pouch, and start it on its circular, peripheral route to the pickup tubes.
I was impressed by the huge amount of oil and air directed away from the rotating assembly by the passive scrapers, even though they were so far away from the crank and rods. I wanted to try extending them until they were within about 1/8" to 1/4" from the rotating assembly. As you’ll see in the next shot this is what we did. We installed Bob's scraper up at the pan rail and extended the 6:00 scraper to within about 1/8" from the rods. These 2 changes produced an increase of FIVE average horsepower from 7,000 to 9,000 RPM! From 8,500 to 9,000 it was actually worth TEN average HP.
Long 6:00 scraper, Pan rail scraper, Higher RPM pulls
