Dry Sump vs. Wet Sump
Most street engines have wet sumps, a term that means that the entire oil supply for the engine is contained in a pan, or sump, under the block. Because oil naturally drains to the lowest point in a system, the sumps are considered "wet" because they are typically full of oil.
Some street engines (Porsche 911, and Corvette Z06, for example) and most track-oriented or race engines have dry sump systems. These systems have pumps, external tanks for oil storage, and typically, very shallow oil pans (since the pans do not have to store much oil- it is typically in the external tank). They are called "dry sumps" because an oil pump constantly pumps oil from the very shallow sump back to the tank, where it can be de-aerated and made available for replenishing the engine; thus the sump is mostly relatively dry of oil, compared to a traditional wet sump.
The following chart outlines the pros and cons of wet sumps vs. dry sumps:
|Feature||Dry Sump||Wet Sump|
|Power||Generally "makes power" compared to a wet sump, due to reduced drag on the crank throws and rods from oil in the sump, especially in corners.||Drag on the crank, rods, etc., from oil in the sump costs power, especially at high RPM. The difference between a wet and dry sump on a domestic V8 engine can be around 10-25 HP.|
|Oiling||Better oiling, since the oil source is a deep tank, not a pickup that can be uncovered in cornering.||In extreme cornering, the oil pickup at the bottom of a wet sump can be uncovered, drawing air instead of oil. The result is usually catastrophic engine failure.|
|Complexity||More complex, potentially more failure points||Less complex, very well understood, so potentially more reliable.|
|Cost||Because of the complexity and extra parts associated with a dry sump, the cost is always higher compared to a wet sump system.||Fewer parts cost less, making wet sumps the dominant choice in street cars where racing or extreme cornering loads are not anticipated.|
|Capacity||Oil capacity can easily be increased merely by a larger tank, assuming there is room. Generally, more oil capacity means a greater reserve when extreme cornering loads are present.||Making the oil capacity bigger in a wet sump means a deeper pan, which has a host of packaging, cost and handling issues.|
|Aeration||Air is frequently introduced in oil in high performance engines under extreme cornering load. This tends to cause engine failure, as oiling is impaired. A typical well-designed dry sump tank is round, and tall. With the correct oil intakes (set on a tangent to the inside of the tank, at the top), oil is naturally de-aerated, so the pickup at the bottom of the tank only gets oil without air.||Wet sump engines are more susceptible to failure from oil aeration. Windage trays, scrapers, and other devices have been designed to minimize this tendency, but they are normally not as effective as a true dry sump.|
|Packaging||Because a dry sump pan is very shallow, engines can be mounted much lower, providing better handling due to a lower center of gravity. This is a key consideration for racing, and in some other cases where packaging constraints limit overall engine height.||A wet sump will always have a deeper pan, all things equal, than a dry sump. Thus the engine will have to be mounted higher, with a higher CG, which makes handling worse, and can complicate packaging since the overall engine height is taller.|
LS Series Engines
Almost all variants of the LS engine family have wet sumps. A few of the LS series engines- notably the LS7, LS9 and a very few LS3 engines were equipped from the factory with a dry sump system. The dry sumps from GM are sometimes referred to as "semi dry sumps" because unlike racing dry sumps, they don't have as many suction points on the pump. As such, an SL-C that is actually wheel-to-wheel racing should use a 4, 5 or 6-stage pump and system as provided by Dailey, ARE and others. But for track days, and extreme street use, the GM dry sumps are fine, especially when paired with large capacity, well-designed tanks as from Peterson. Most SL-C owners with LS engines and a dry sump (GM or aftermarket) use the Peterson 08-0009 tank, also used in the factory 01 championship-winning SL-C.
It's interesting to note that years ago when people first started tracking and racing the C5 generation of Corvette, there were so many engine failures from improper oiling that the SCCA and other sanctioning bodies permitted them to add a dry sump, even though they would have normally been prohibited in the stock classes. The newer cars were generating so much cornering load that a dry sump was considered the best solution, and so special permission was granted to allow the cars to race without blowing engines.
For street use, a dry sump on an SL-C is probably not really necessary. If you have installed an LS7 though, it already comes equipped with the right pan and pump, and expects a dry sump, so everyone adds the rest of the parts required. Plus, it makes power, and adds a safety factor. It may even look cool- or so we are told... For other LS engines that see only street duty, it really isn't necessary, unless you want the extra power and safety margin that a dry sump provides.
If you have an LS7, LS9 or other LS engine with a factory dry sump, you need the following parts to finish the task:
External tank Peterson 08-0009 or similar tank, 3 gallon. Fits neatly in several places in the SL-C and used in the factory 01 car, as well as many street cars with dry sumps.
Pan adapter You'll need to convert the factory GM outputs on the pan to allow you to make hoses with AN fittings to go from the tank to the pan. These are available at several places, including Peterson. Use part number 08-0502.
Breather These tanks require a breather. Several have used the Peterson breather with success- use part number 08-0400-ATS
Of course, you'll also need to fabricate your own lines from the pan to the tank, with the correct AN fittings.
If you'd like to improve the performance of the stock "semi-dry" sump LS7 oiling system without dealing with the cost and complexity of a full dry sump system you might consider one or both of the following:
- Upgrade the pan: ARE makes a popular aftermarket pan that is compatible with all the parts listed above.
- Ported pump: Katech provides ported OEM oil pumps for the LS7 and LS9 which they claim have 30% greater scavenge capacity/20% greater pressure capacity. <If you have a LS7 you may want to use the LS9 pump -- need to validate>
Peterson 08-0009 oil tank
A: Connects to oil pan in
B: Connects to oil pump out
C: Connects to breather (see D below)
Use -12 fittings and hose for all three connections
What is fitting size for E&F?
Oil pressure sensor?
Oil Temp sensor?
Peterson 08-0400-ATS breather
D: Connects to oil tank (see C above); use -12 fittings and hose
E: Connects to valve cover one
F: Connects to valve cover two