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Pumped Up For Peformance Oiling Systems
Determining whether to use a wet-sump or a dry-sump oiling system for your racing/performance customers is a question you may never have the chance to answer - it often depends on what the rules allow and the size of the racer's budget.
By Brendan Baker
Most OE engines use a wet sump system, which can be modified for performance applications to improve oil control and increase horsepower. A dry sump system, on the other hand, has been specifically designed for performance applications and is mainly used at the higher levels of racing where oil control is critical for producing maximum horsepower.
For purposes of this article we will concentrate on the wet sump systems designed for racing and performance applications, as they make up the majority of the grassroots-level market.
Performance Oil Pumps
In the past, enthusiasts believed that high volume and high oil pressure was the way to go in a performance application, but today that is not so much the case. Experts say the trend now is to run a little less oil pressure than in the past. In fact, many believe most pumps may be oversized for their application anyway. The small block Chevy pump, for instance, was designed in the late '50s to run 10 gpm oil flow so that on a hot day at 500 rpm you had sufficient lubrication. But when you take the engine up to 7,500 rpm the pump has more capacity than the engine requires. With many racing applications you're bypassing 50 percent of its capacity to the pump. Repumping that oil just puts unnecessary heat into it, according to some experts.
In addition, the high volume pump for the SBC is the same diameter but a little taller gear, so a lot of engine builders are going back to the standard volume pump, especially in restricted classes where builders are looking for every bit of horsepower. One reason for this is because very few race engines are ever at idle and when they are it's at 1,500 rpm instead of 500-600 rpm. Simply put, the engine doesn't need as much pressure at low rpm because it doesn't run there.
"It used to be that people wanted to see 120 psi of oil pressure, then it dropped down to 80 psi and today most customers are really happy with 60-65 psi," says Verne Schumann of Schumann's Sales & Service.
Baker Engineering's Jack Jerovsek says his company modifies a stock oil pump as the basis for the circle track SBC performance wet sump pump, which eliminates all the oil going through the main cap and brings it into the middle of the gears like a dry sump pump.
"Our whole goal is to reduce the amount of bypass the pump has to make and to reduce the aeration of the oil, which inherently reduces the temperature," says Jerovsek.
Jerovsek and others also say you should consider a high volume pump in high horsepower applications where your bearing loads and volume pressures go up and you need a little bit of extra pressure, and if you're running oilers for the springs and flat tappets, or piston oilers and so on, then the extra demand will require more volume.
Schumann's offers three levels of performance pumps, which are based on the same high-alloy 70,000 psi temper heat treated housing. Schumann's pumps are geared for the grassroots strip/street/track market because he says that's 90 percent of the performance oil pump market.
"Unless it's a top notch, high-end race engine, the ET racers and class racers (stock and super stock) sure don't have dry sumps. Unless they're running a Nitro Fuel Dragster or Pro Stock engine, your customers are probably running a wet sump system."
Schumann says his company has completed its SBC line and is now working on Windsor and Hemi applications.
Schumann's SBC pumps have nine additional features over the stock pump. "On the driven shaft in the pump, we're taking the time to machine oil retention grooves the length of the housing, which actually gives the oil a place to flow, so you have a higher change over rate of oil, says Schumann. "And believe it or not, the rotation of the oil pump actually hinders the oil from getting in there as it is being thrown to the outside by centrifugal force. We grind a notch in the bottom of the floor of the pump housing that takes the pressure side of the pump and pushes oil underneath the gear. We chamfer the gear and put an oil groove in the oil hole as well, so we know we are getting oil in there."
The second thing that happens in oil pumps is aeration; all oil has air in it by nature; as it splashes around and picks up air, it cavitates to the top of the pump. With that groove in there, it gives the trapped air in the top of the pump an escape hatch. Also, our preset on our OE Plus series pump is 50-55 psi, which is 15 psi over OE specifications (40 psi)."
Drag Race Pumps
In a typical OE application, engineers calculate the bearing clearances, journal sizes and so forth throughout the engine. From there they can estimate the volumetric requirements for oil. Then they design an oil pump that is 30 percent larger than the maximum requirements. Today's drag racing engines run tight clearances and very light oil, so many experts say they don't need that extra 30 percent volume because it just costs horsepower to pump all that oil through the engine.
Consequently, some oil pump manufacturers have recognized the need for a smaller volume pump for drag race applications. "What some Chevy guys are doing right now is taking the standard 55 psi pump and cutting the gears down and making spacer plates and then selling them for a lot of money because the pumps are handcrafted. We are in the process of developing a high quality, low volume drag race pump that will be affordable to the average racer," says Schumann.
Experts say you need to look at your bearing clearances first to help determine what type of oil system to run.
Mike Osterhaus of Melling Engine Parts explains: "If you're running clearances close to stock or even tighter, then you really don't need a high volume pump unless there are other plumbing or accessories that require an oil feed. Some guys might decide they want to run piston coolers and plumb in coolers or if you run a remote oil cooler or filter where there's going to be more pressure drop to fill that system than there was originally, then you need a high volume pump for that application to compensate."
Instead of lowering the displacement of the pump some engine builders are using a weaker relief spring so they can bypass the higher pressures. This way the pump goes into bypass sooner and uses less power to drive it up into the engine. This is one of the ways you can reduce the system pressure in the engine and get back some horsepower that was lost driving the pump.
On the drag race side, some builders use an oil accumulator to compensate for lack of oil in the pan during the run. And a lot of racers will run the accumulator just to protect the engine if the oil pressure were to go below a certain pressure setting. The oil may be somewhere else in the engine because of the forces involved and end up exposing the pump pickup, say experts.
Melling's new billet oil pumps are designed to fit particular sizes of oil pans according to Osterhaus. The pickup is integral with the pump assembly; yet, Osterhaus notes, that in doing this there's no flexibility for putting different pickups on the same oil pump.
Osterhaus says that one of the reasons his company came out with this billet pump was because of high interest from guys running deeper pans. "It fits into the street strip market as well," says Osterhaus. "Even though this is a performance piece, it will operate well in the high and low rpm ranges."
Keep It In The Pan
Experts say all those tricked out expensive parts you installed can become worthless piles of metal if you don't choose the right oil pan that allows your oil pump to pick up a steady stream of oil under constant gravity forces pushing it away from the pickup.
There are a lot of things going on that can affect the oiling system such as the "rope effect," where oil essentially wraps around the crank and doesn't fall to the pan quickly enough. The oil can become suspended around the crankshaft as it rotates and won't return to the pan where the pickup is located. So, for these issues you really need an oil pan that addresses these issues to better manage the return oil.
Some engine builders will go into the heads and open the passages up to help return the oil into the bottom of the engine. What some engine builders do, according to their own preferences, is try to determine how much oil is needed at the top of the engine and put in an oil block off into the oil galleries in the heads. That way you can keep the oil heading to the bottom of the engine.
"One of the most effective oil system upgrades is the oil pan," says Moroso's Kevin Brown. "We have a series of different oil pans that add capacity and a series of different windage trays in them to help baffle and keep oil off of the rotation assembly. Most of what we do is for racing and the aftermarket, but we also have some pans for OE applications as well."
The sump part of the pan is really what is different on the various pans and applications. A drag racing pan is deeper but not as wide, whereas a circle track pan is offset because of all the loading on the right side. And in offshore racing, for instance, the sump is more centered.
"For drag racing we've got some intricate pans that have pretty interesting windage trays in them. We've seen a 2-3 percent gain on average in our big block applications," Brown says.
"In road race applications we have a lot of different pans that have some trap door baffling in them. Most of our road race pans for the wet sump stuff in particular have four trap door baffles to help control the oil in braking, acceleration and under heavy cornering loads," says Brown.
"The kickout allows you to add a little bit more oil volume, and the recovery pouch on the side of the wet sump oil pan itself allows you to gain more volume, more air space to help control the oil in the pan."
Experts say that if you use adjustable scrapers in the pan it needs to just about touch the crank to remove most of the oil from the rotating assembly.
"Our biggest challenge is to scrape as much oil as possible off of the crank and rod assembly and get it down to the pickup without any air as fast as possible," says Baker Engineering's Jerovsek. "If it's a drag racing application, you need good oil control during acceleration and deceleration type oil control or baffling system in the pan. The baffling system in the pan is designed to keep all the solid oil at the pickup and not have gravity or accelerations/deceleration move the oil away from the pickup.
Drag racing launches so hard so all the oil tends to run up the back of the engine and tries to run out by the distributor (e.g., Chevy). So you need some type of baffle that compartmentalizes the pan so it maintains some of the oil in certain locations and keeps it from running out the back of the engine. So when you get on the brakes hard and all the oil moves forward, and we have a compartment with a trap door that closes and keeps the oil from going all the way forward and keeps it at the pickup."
In oval racing, racers may be pulling over 2 G's in a corner, which really slings oil up the sides of the block. As a result, many pump manufacturers put their pickup on the right side of the pump so the lateral loads move the oil to the pickup.
A street application it is similar to a road race application where you have to set up for both left and right turns, which is why many oil pans for these applications have baffles to the right and left. The other thing you can do to control temperature is increase the capacity, say our experts. That's why a lot of performance pans have a deeper sump on them. An OEM pan is 4-5 quart capacity; performance pans have much greater capacity so there is more opportunity to cool the oil by making the pan longer or deeper so it transfers heat better.