Choosing the right dry sump oil pump can be a difficult process. Here I break down the steps and factors to help make it a little easier.
Whether you’ve got a few more pennies rubbing together in your pockets, or you’re building a real strip burner producing several hundred horsepower and foot-pounds, you’ve decided that the best oiling/lubrication system for your strip burner’s engine is a dry sump system.
There are a number of companies supplying whole kits as well as bits and pieces. So how do you decide which to get? In my opinion, the major deciding factor, once you’ve come to the dry sump conclusion, is cost. None of it comes cheap, which means you want to be sure you’re getting the right pump for your vehicle. I’m going to lay out the different types of systems out there, as well as some of the more popular manufacturers to help you make a more informed decision.
When to Go with a Dry Sump System
We’ve gone over this before, but there are a few reasons for going with a dry sump system for lubricating your engine. The first one is how much power you expect to be making and what kind of launches you expect to get. If you don’t expect much oil splash, you can technically stick with a wet sump system and put your money into making more power and hooking that power up.
However, if you’re expecting to get funny car or dragster-type launches, especially with wheelstands, you’ll probably need a dry sump system. If you’re building a high-RPM engine, the problem is compounded. All that oil slopping to the back of the engine can seriously damage, if not outright kill that multi-thousand dollar investment known as a drag racing engine.
The original design of dry sump systems was driven by a need for more reliable lubrication systems in high power race cars. Over the years these systems have evolved to the point where they also help engines deliver more horsepower and allow them to be mounted lower, increasing high speed stability by lowering the center of gravity.
What Constitutes a Dry Sump Lubrication System?
As I’ve mentioned before, a wet sump lubrication system scavenges the oil from the oil pan, the sump, keeping the pan as dry as possible. This type of system is made up of the following parts:
- The dry sump oil pump which is a multi-stage pump driven by an accessory drive belt.
- The external oil storage tank.
- The external oil filter and mount.
- An oil pan with scavenge fittings attached.
- Tubing and piping to connect the system’s components.
There are a variety of different types of dry sump pumps made by a number of companies. Pumps are usually identified by how many stages they contain, with these stages numbering anywhere from two to six. At least one stage will be used to scavenge all the oil from the oil pan and pump it to the reservoir. The second stage will pump the oil through the filter and to the engine.
How Many Stages Does Your Dry Sump Pump Need?
For the average strip burner, a two stage dry sump pump should be sufficient. However, if you throw in a good-sized oil cooler and a large oil reservoir-more and cooler oil retains viscosity, thus engine protection-you’re going to need to increase the number of stages.
The guys that get paid big bucks to design and build the engines for the racing teams use expensive programs to help them calculate the requirements of the engine they’re building. Most of us don’t have that luxury, we’ve got to do it ourselves.
Engine and pump designers tell us that two stage pumps should be fine for most engines developing moderate amounts of horsepower. A third stage will be helpful, but most likely not necessary. This tells me that I want three stages, at minimum. If I’m building a huge blown big-block that’s going to spin at high RPMs, I’m going with at least four or five stages.
What about the Different Types of Scavenger Stages?
There are two different types of scavenge pumps/stages used in dry sump pumps. The first, and most common is the gear type. This is composed of two or more gears that mesh together in such a way as to create pockets which trap air and oil. As the gears rotate, the fluid that is trapped is pressurized and moved from one part of the pump to another. Because this type of pump traps less air, it is more efficient.
The second type of scavenge stage is Roots. In this design, instead of gears, we have spinning rotors that trap air and oil between the rotors, pressuring them and moving them further along the system. The Roots type scavenger pump pushes more volume, but it also traps more air, thus decreasing efficiency.
I prefer to utilize a pump with a mix of both gear type and Roots stages. This way I get the best of both worlds. I increase volume using the Roots stage and I increase efficiency using the gear stage or stages. If I’m building an engine that will produce moderate amounts of horsepower, I’ll go with one of each. If I’m building a beast, I’ll go with two gear stages and one Roots. Finally, if I’m building a monster blown big block, that baby is going to have two and two, or three gear stages and one Roots stage.
Another Word on the Differences Between Gear and Roots Stages
Every engine, no matter how much care you take of it, generates some form of debris. This is carried away by the oil and hopefully trapped in the filter or filters. Sometimes we’ll put a strong magnet on the bottom of the oil pan to catch the bigger pieces. This debris causes damage throughout the engine, and the oil pump is no exception. To cut down on the amount of debris floating in the engine, besides the magnets I mentioned above, dry sump pumps have filters in the scavenge tubes, this helps keep the worst of the debris from damaging the pump.
Roots-type pumps are somewhat fragile and susceptible to damage caused by debris floating around in the oil. Gear-type pumps are far less susceptible to damage by debris. Because of this, the filter/screen in the scavenge line can be bigger, allowing smaller pieces to move through the pump and be trapped by the main filter without degrading oil flow.
Some Final Words on Dry Sump Systems
Every pump will have listed on its spec sheet the ideal RPM range, after which the pump will begin losing efficiency due to cavitation-the creation of air bubbles in the oil being pumped. Some dry sump pumps begin cavitating around 4700-5000 RPM. You will need to determine the max RPM of your engine to determine the proper pulley sizes so as to stay within the ideal operating speed range.