Accumulators have been around for years. Many racers have the idea an accumulator is someone who has a collection of dusty race car parts lying around the shop. If that's the case, I guess I'm an accumulator, but that's not what we're talking about. An accumulator on a race car engine is a totally different animal. It helps keep the oil pressure up when the going gets sideways. Just to be safe, I've used an accumulator on all of my own race cars for the last 20-odd years.
Any race car engine which uses a wet sump oiling system can benefit from the installation of an accumulator. When oil sloshes around in the pan, such as during a hard left turn, it will sometimes uncover the oil pump pickup. This action allows air to enter the oil system. When air enters the oiling system of a race engine, there will be a problem with lubrication.
The oil accumulator is a chamber that, as the name implies, accumulates pressurized engine oil. The accumulator holds it there until a time when oil pressure in the engine falls. Then, it feeds the oil back to the engine while the pump is rebuilding pressure. At this point, the pump also refills the accumulator and the cycle is ready to begin again. Keep in mind this may all happen in a fraction of a second.
Race car classes that require the use of stock-type oil pans can benefit most from an accumulator. They have no baffles to help hold oil in place. Also, the track surface is a key consideration. The flatter the track, the more benefit from an accumulator. For those of you who run claimer classes, keep in mind that an accumulator does not go with the engine in a claim.
I stumbled across the need for an accumulator when I once installed an oversized line from the engine to the oil pressure gauge. This allowed pressure variations to show up instantly. I was horrified to watch my oil pressure drop from 65 pounds to near zero. This happened just as I was applying full throttle to a groaning 454. Granted, it returned to normal in a moment or two, but there was that period of time with no oil flow.
Let's consider this. If you run a 26-week race schedule, you might run at least 40 laps at race speed each night. There would be two corner sequences for each lap. This adds up to your engine suffering 2,080 moments of close to zero oil pressure each season. All of this is happening while the engine is running full throttle, too. When you think about it, it's hardly the way to extend bearing life.
Moroso manufactures the engine oil accumulator we currently use. There are two distinct types. One must be installed in the vertical position and has no moving parts. It depends on gravity to separate the oil and the air. The other type has a moveable piston to force the oil back into the system. Pressurized air provides the force to move the piston. This type has the advantage of being able to be installed in any position, which is important when space is tight.
I have used both kinds and have seen no difference in their performances. The vertical mount unit is generally less expensive and lighter. With no moving parts, it has to be reliable. This one is my choice where there is room to mount it. Obviously, the accumulator will have to go where it is best going to fit. You should try to locate it as close to the engine itself as possible.
A valve at the accumulator is strongly recommended. It can be manually operated with a push/pull rod. In some applications, an electric solenoid valve might be preferred. On a race car, the manually operated valve is usually better. The reason for the valve is to allow the accumulator to hold oil when the engine is shut down. At the moment the engine is to be restarted, pressurized oil can be released. This gives oil pressure to the bearings before the starter begins to turn the engine.
Let's say you start the engine about 300 times per season. Utilizing the oil accumulator, your high compression engine will be started 300 times with oil pressure already flowing to the crankshaft. Along this line of thinking, an accumulator for your hauler might not be a bad idea either. The electric solenoid valve would be good in this application.
Installation is not difficult. Our guinea pig car belongs to Michael Bowles with an engine that was due for a rebuild, but still showed good oil pressure. Bowles purchased his accumulator from Performance Auto Supply in Mesquite, Texas.
We were able to utilize 85 Speedway for a test. A video camera mount was welded to the rollcage and a camera was secured by duct tape. The car was not equipped with an accumulator for this first run. A 3/8-inch line was plumbed to the oil pressure gauge to make it react quickly.
And react, it did. As expected, the camera showed about 60 pounds of oil pressure down the straight. In the middle of the turn, at the point where the throttle was mashed, pressure dropped to between four and five psi. It came back, building to almost 60 pounds, in about 130 feet.
The unit was installed in an about an hour. There is a factory oil passage drilled and threaded into the block near the pump. On the Chevy engine, it is at the rear while Ford engines have it located in the front. The outer is a 1/4-inch pipe thread where a fitting was screwed in for one end of the hose. A push-on hose was chosen for the project. "It's easy and it works" were the reasons given.
Michael's dad, Kevin, did the installing and track testing. He used Loctite on the fitting to the valve and accumulator. This is necessary since the push/pull action to open and close the valve will try to twist the fittings. With accumulator assembled (valve, fitting, and hose), it was then bolted in. Now, it becomes a simple matter of pushing the hose on the engine fitting.
A variety of hoses are available, each with their own type of fittings. Braided stainless steel looks good and wears well. Less expensive and quite adequate for the job is a hose made by Aeroquip. Called AQP Socketless, this hose makes installation simple and easy. Blue in color, it uses special fittings, but needs no clamps. In fact, it is a mistake to put a clamp on it. Doing so may cut the inner liner and reduce the performance capabilities.
We used the Aeroquip hose in our installation. Never make the mistake of using rubber fuel line or any other hose not rated for several hundred pounds of pressure and higher temperatures.
The accumulator must be securely clamped in place in the car. If possible, it should be attached to a chassis member rather than the sheet metal firewall. It needs to stay in place in order to do the job. To further secure the unit, Kevin welded a steel bracket onto an upright near the left rear of the engine. The hose was less than 18 inches long in this case. A hole was drilled in the firewall for the pull rod to actuate the valve. Kevin found a 1/4-inch rod to be adequate.
With the installation complete, it was time for everyone to clean up and head for the track again. The video camera again focused on the gauge. Michael and Kevin were all smiles when the video showed nearly constant pressure with the accumulator installed. The owner of the camera smiled when the borrowed unit returned in one piece.
A final word of advice. Install your accumulator where it can be seen and paint it a bright color. You may be amazed at the number of racers who come by and want to know what that is. Tell them it's your insurance agent...you keep him in a can.