I'll give you the Cliff Notes version.

Basically, the oil for your engine is held in a remote reservoir instead of the oil pan. The advantage is being able to run a lot of oil without fear of over-filling the crankcase, which increases crancase pressure. Also benificial in racing where excessive G-force might cause the oil to pool on the side of the engine thus causing the oil pump to suck air...which is a big no-no.

I don't know the answer to your second question.

 

I'll give you the Cliff Notes version.

Basically, the oil for your engine is held in a remote reservoir instead of the oil pan. The advantage is being able to run a lot of oil without fear of over-filling the crankcase, which increases crancase pressure. Also benificial in racing where excessive G-force might cause the oil to pool on the side of the engine thus causing the oil pump to suck air...which is a big no-no.

I don't know the answer to your second question.

Umm, could you please draw a diagram on the chalkboard for the slower kids in class. Like me. :lol: :crazy:

I took this from howstuffworks.com:

Dry sump systems have several important advantages over wet sumps:

Because a dry sump does not need to have an oil pan big enough to hold the oil under the engine, the main mass of the engine can be placed lower in the vehicle. This helps lower the center of gravity and can also help aerodynamics (by allowing a lower hoodline).

The oil capacity of a dry sump can be as big as you want. The tank holding the oil can be placed anywhere on the vehicle.

(like he said) In a wet sump, turning, braking and acceleration can cause the oil to pool on one side of the engine. This sloshing can dip the crankshaft into the oil as it turns or uncover the pump's pick-up tube.

Excess oil around the crankshaft in a wet sump can get on the shaft and cut horsepower. Some people claim improvements of as much as 15 horsepower by switching to a dry sump.

The disadvantage of the dry sump is the increased weight, complexity and cost from the extra pump and the tank -- but that's a small price to pay for such big benefits!

 

Would it be possible to use the C6 ZO6 dry sump and trans and diff cooling systems on a C5 Zo6?

Bob:
There are dry sump systems for our engines, as the actual C5-R uses such a system on it's similar-familied engine. As to whether it's economically easier to use the C5-R or C6 version, talk with a major player like LPE or Katech, who have experience firsthand with that sort of upgrade.
Tranny and diff coolers are available from GM Performance Parts and others.

 

here's an easy way to conceptualize...

In a dry sump system, oil flows through the motor the same as in a normal system. But, oil returning to the oil pan is sucked out of the pan at a rate that's faster than the rate at which the oil flows through the engine and returns to the pan. This leaves the oil pan "dry", and the "excess" oil is stored in a reservoir separate from the oil pan. The oil supplied to the motor is drawn from this separate reservoir.

The advantages are as listed in a previous reply.

 

Most of the SCCA World Challenge Z06s have dry sump systems. Not sure where they get the parts though. LGM or maybe Phoenix will likely know more about this.

 

Ok, ok...let me start my saying I have an dry sump system on my race car. And I had to re-engineer it after I bought car. So here goes.

Everything Z06drvr said is 100% correct. However, many classes have crank height rules, usually around 9 inches, sometimes higher, that negates some of the advantage.

Before going further, let me discuss the parts. First, there is a tank. It is usually tall. Oil enters along a edge and swirls inside. It drops through some baffles. In a typical 12 qt tank, the oil in a running engine is just over half way up the take, about 1 ft.

Current dry sump systems are vented through the tank (more on that later) to typically an aluminum tank 3" in diameter and about 6-8" tall. There is a breather vent on top and an oil return on the bottom.

A multistage pump mounted on the engine is driven off a pulley on the front of the crank. Typically, HTD belts are now used. Square-tooth belts used to be used. The pump has one pumping stage. It has a screw adjustment for pressure. Tuning is done to achieve about 5 gallons/minutes on an SBC. Pressure is whatever. Current engines run .020 or so clearances all around, and with oil pumped directly into a main gallery (in contrast to the oil filter mount), pressures are usually around or under 50psi.

The pan has a side kick-out on the right. Size of the kick-out varies. There is also a scrapper closely fitted to the crank (the engine builder grinds this to fit on the completed motor. And a metal screen below and to the right of the crank. The pans can be sheet steel, sheet aluminum, or cast aluminum.

Oil is pumped out of the engine my multiple scavenge stages. Rules in limited classes restrict you to two scavenge stages. Otherwise people run 3-5 scavenge stages. Typically the first two go to the pan, the third (if allowed) goes to the lifter valley, and subsequent ones...well, I haven't dealt with that.

Now to the lines. An AN12 (on an SBC) runs from the tank to the pressure side of the pump. Then from the pump to the oil filter, to the oil cooler (typically in mounted in the hot-side radiator tank), to the main oil galley (on the front above the cam gear on an SBC Bowtie). A tap (fitting with two AN4 lines) may route oil to the valve spring oilers in the valve covers.

The lines from the engine are also AN12. There should always be a screen when the oil exits the engine to catch metal shavings. In either the pump or a fabricated manifold above the pump, the different scavenge lines are merged for the return. Some systems use multiple AN12s for the return. Most current systems use a single AN16. Sometimes another filter is mounted on the return. A couple of tanks come with an Oberg filter on the return.

Back to the pump. I have seen older pumps with 3 1.25" sections. A modern rotor pump may have as small as a .8 section for pressure, and 1.7" sections for scavenge. Pumps are wither a rotor or gerotor design. Both in use, although the pump I think is the cats pajamas is a rotor design.

If you think you think about, you can't return more oil than you pump. However, you can return air. A vacuum in the the crankcase can add serious hp. I believe Nextel cup cars draw close to 20in.

To get vacuum you need to seal everything. Different front and rear crank seals. Distributors (on cars with them). the lifter valley. And pumps are now designed for it. The Barnes pump uses two rotors instead of the more common 8 or 10 (it is too late to go into the garage to count), because it sucks more air.

You buy the parts separately. Moroso, ARE, Milidon, Stefs, Canton, etc. make pans. Barnes, Peterson, Moroso, Johnson, SCP (in CA, not NC), and others make pumps. They are usually sold with the mount. Pulleys are part of complete systems from Jones and others. Peterson and others make the tanks. Numerous people make the breather cans, however I like Oval Craft. All of the radiator (C&R, Griffen, Fluidyne, etc.) people make oil coolers in the radiators.

Peterson (petersonfluidsys.com) also makes one way check valves for the breathers (there is also a firm in Florida whose name escapes me). They come to ways. To vent of the pump fails to scavenge enough air. And to vent air in if scavenges too much. I have the first. Nextel Cup cars have both.

There are two other nice benefits. If you go off road (which happens in racing more than we would like to admit), the shallower oil pan (further off the ground) is less likely to develop a new drain hole. And using neat little bolts from peterson to hold the pulley on the pump, you can easily prime the engine with an air ratchet.

Typical Tank:

Typical pump:

Typical pan...actually an LS1 pan:

 

So why so much oil? I've seen references to 12 quarts.

I'd think that at some point the benefits of more oil capacity would be outweighed by the additional weight of the oil and size of the tank, and that that point would be reached before 12 qts. What am I missing?

 

Dry sumps have a larger oil capacity for a nember of reasons:
- most dry sump pumps run at a higher flow rate, this allows:
- higher system pressure
- higher volume of oil pumped, so you get:
- better oiling
- better cooling
- less oil break down or slower oil break down
- increased HP by removing the oil from the crank
- less windage in the pan area so you have:
- less aeration at the crank.

- Above all you need to run a high volume so as not to uncover the oil pick up

However the more pan outlets you have or pump stages you have increases aeration so:

- The reservoir not only acts as a reservoir but an air/oil seperator by swirling the oil as it enters and by using a series of baffles. However the best way to seperate the air from the oil is by time in the reservoir to allow the oil to debubble. Hence a larger oil capacity allows this.

Note that most reservoirs are run 2/3 full to allow the swirling and baffles to work in the upper portion.

I recommend the Petersen Fluid Systems reservoirs and inline filters.

 

BTW the C6 Z06 will be a single stage 8 qt. system, which is relatively small but will offer a higher system pressure than current OEM wet sump systems.

 

David,
Great writeup, thanks.

DJ,
Excellent info as always. :cheers:

 

Dry sumps do not flow more oil...however the tank is larger then the tank in a wet sump, and there is more oil in the lines.

A racing wet sump will be a 7 qt system. While the tank is nominally 3 gallons (12 quarts) for a SBC dry sump, typically you only use 10 qts. More loses the deaeration features of the tank and blows excess oil into the breather tank.

Current systems are designed to flow around 5 gallons/minute. So the pressure is a function of what is needed to get that rate. I think peterson even sells a little flow meter. However that is just a dyno piece, not used during a race. And the Peterson one, if I recall correctly, doesn't have very good resolution around the SBC flow rates.

David

 

BTW the C6 Z06 will be a single stage 8 qt. system, which is relatively small but will offer a higher system pressure than current OEM wet sump systems.

A single stage is not a dry sump. To have a dry sump you must pump the oil out of the pan. Maybe they only have one scavenge stage.

The pictures of the tank on the LS7 seem to show awfully small return lines.

Many wet sump racing cars use a belt driven external single stage (pressure only) pump. This allows the oil to be feed into the main oil galley (entrance above the cam drive cover) and externally adjust the oil pressure. These engines use gravity to return oil to the wet sump.

Many cars with or without an external oil pump have an external vacuum pump for added power. I have wondered why no LS engines seem to have that.

David

 

David,

You have aptly described a conventional dry sump system. However you have assumed some things and we know what the Marine Corp. definition of assume is.

First of all pressure and flow are directly proportional, especially in a closed or non-vented, non-compliant system while using a positive pressure type of pump. If you increase flow or pump output then pressure rises. When you increase pressure the flow increases.

So a dry sump system with a higher output pump, putting out a higher pressure will flow more oil in the same system than a wet sump system with a lower output pump.

The most common types of pumps used in dry sump system are belt driven positive displacement Gearotor or Roots type which can sometimes be shaft or crank driven as in the LS1/LS6 Gearotor wet sump oil pump and LG Motorsports 2 stage Diff mounted Tranny/Diff cooler pump.

It should be noted that until recently that there were no aftermarket replacement or improvements on the OEM gearotor oil pump. One has just been developed by increasing the size (width) of the internal gearotor and housing. There is a larger displacement of oil with each revolution hence this pump increases pressure and flow over the OEM. Also roots type pumps, such as those produced by Dailey Engineering, are advertised as:

".....our design privides up to 50% more volumetric capacity.".

That would indicate to me that it "flows more oil" and puts out a higher pressure.

Of course a higher pressure does not always mean higher flow if you have a compliant system, an open system or are using a non-positive displacement pump such as a Constrained Vortex type like the Bio-Medicus Bio Pump. In these situations there is a point of deminishing returns where flow and pressure can not over come resistance due to the non-occlusiveness of the pump. This incidently is the kind of pump used on the Heart Lung Machine during Open Heart Surgery whilst perfusing a compliant system, the human body and similarly in water pumps, however with a vaned rotor.

What is interesting is that in GM's pre release info on the LS7 is that it will have a larger displacement Gearotor pump necessitating a different front cover than the LS1/LS6. This would indicate a higher output pump. In addition this pre release info states some other interesting facts:
- "the dry sump is a single scavange, single stage pump providing higher system pressure than in previous models", and,
- "the pressurized 8 qt. reservoir provides a constant flow of oil to a conventional oil pick up in the pan which distubutes oil to the engine , even under racing conditions."

Before making a final judgement on the system until I see the schematics and flow charts next week, my interpretation of these remarks is that we are not dealing with a conventional dry sump system in the LS7. In fact it
- will be a single scavange dry sump with
- a single stage, crank driven gearotor pump with
- higher out put (flow rate)
- higher system pressure
- the reservoir will be a non vented, pressurized unit acting as a reservoir, air/oil seperator and an accumulator (Accusump)
- emptying into a pressurized type of internal surge tank or slosh tank for return to the engine (something like we see in ATL's or Fuel Safe's new fuel cells).

AND it will have a higher system pressure and in fact flow more oil (LPH) than the current OEM wet sump.

 

To the average guy a drysump means he will change oil, air lock the feed line from the tank, and blow the crap out of his engine.

 

The primary reason for dry sump systems is to prevent oil starvation during high G maneuvers period.

Sabot

 

This is all neat stuff I didn't know before.

 

This is all neat stuff I didn't know before.

Totally agree! I learn something new each time I log on here...thanks for sharing the knowledge guys :z:

 

DJWorm,

You are absolutely right, pressure and flow are related. However, in race cars the current technique is to calibrate the pressure to get the desired flow. And pressures under 50psi are common. One of the key points that became common knowledge a few years ago is that the pressure doesn't affect the bearing lubrication. That is a dynamic action from the shaft rotation.

To keep the flow where they want it with 5-30 or 5-20 synthetic racing oil pressures are typically 50psi or less.

Now to the LS7. It appears to be a two stage pump, one pressure and one scavange. The pressure side is sent to the existing oil pickup (cheaper) rather than the main oil gallery (better). The single scavange (just moving oil, no significant air movement) returns oil to the tank.

In a race engine constant oil pressure is only one goal of a dry sump. And these days not really the most important, as wet sump pans can be made to work in most cars. However, for the LS7, it appears to be the main reason. My guess is with all those expensive parts, they didn't want to leave anything to chance. They probably also coated the bearings, which is pretty common in engines with lightweight internals.

This the quote from the release. I don't see anything about increased pressure:

Dry sump oiling system The LS7 has a dry-sump oiling system designed to keep the engine fully lubricated during the high cornering loads the Corvette Z06 is capable of producing. An engine compartment-mounted 8-quart reservoir delivers oil at a constant pressure to a conventional-style oil pump pick-up at the bottom of the engine. The pressurized oil feed keeps the oil pick-up continually immersed in oil at cornering loads exceeding 1 g. Oil circulates through the engine and down to the oil pan, where it is sent back to the reservoir via a scavenge pump. The large-capacity reservoir, combined with a high efficiency air-to-oil cooler, provides necessary engine oil cooling under the demands of the engine’s power output. With the dry-sump system, oil is added to the engine via the reservoir tank – which includes the oil level dipstick.

 

Bob,

Great post!

Everyone else,

Great lesson!

I had my own guesses about some of the parts but it's all clear now.

Thanks!!

 

Some more info. ARE makes cast aluminum pans for a variety of engines, including LS1. One of their offerings, their stage 1 kit, uses the stock oil pump for pressure and a two stage scavenge externally. Since it is only the scavenge, they are able to drive it with the serpentine belt, I think replacing the A/C.

It is probably a version of this system (with one scavenge stage and the pump probably mounted in conjunction with the power steering pump) that is on the LS7.

Their link is **edited**

 

" The new Z06 has a new gauge cluster; to reflect the 7,000 RPM Tachometer and a revised Oil Pressure Guage to reflect the HIGHER SYSTEM PRESSURE of the Dry Sump System."

 

I suspect that GM runs the system at a higher pressure as a way to incrementally extend its G rating for a given time period with minimal cost. Higher pressures compress entrained air and bring the behavior of the oil closer to that of an ideal fluid.

The old 10 psi per 1000 rpm rule for wetsumps is a heuristic based on the same situation. It does work up to a point.

 

With the dry sump system, must you take any special precautions to avoid getting air in the lines when changing oil?

BTW, good stuff presented above. Thanks.

 

I saw the engine today and although we did not discuss the oil change procedure, I did notice a drain valve on the engine oil pan as well as on the bottom of the reservoir. I might surmise that it would follow somewhat like:

1. Drain Reservoir
2. Fill Reservoir
3. Drain Engine, Remove and replace filter (should be oil filled)
4. Bump Starter but Do NOt START, to prime engine and lines.
5. Top Off reservoir
6. START Engine, run 1 minute
7. Engine OFF
8. Check & Top Off Reservoir
Recheck Reservoir level after next run time.

Most systems will de-Air thru the scavange circuit into the reservoir and breather vent. However if this is a closed system it should be interesting.

 

Picture references of the LS7 Dry Sump system are now in the C6Z06 Section.

The Pump is a single crankshaft mounted Gerotor with 2 stages (2 gerotors and internal channels

Flow schematic appears to be:

-> Pan Sump -> Pan Scavage Pick UP -> Internal Pan cast Scavange line -> Pump Scavange Boss -> Pump Scavange Stage -> Pump Outlet Pan Boss -> Internal Pan cast Outlet port -> Pan Outlet Boss -> Inlet Line to Engine Oil Cooler -> Engine Oil Cooler -> Oil Cooler Outlet Line -> Reservoir Inlet Boss -> Internal Riser Tube -> Deairator baffles -> Reservoir -> Reservoir Outlet Boss -> Engine Oil Return Line -> Pan Inlet Boss -> Internal Pan Cast Return Line. Pump Pressure Stage inlet Boss -> Pump Pressure Stage -> Engine Inlet Boss -> Internal Engine channel -> Oil Filter Boss -> Oil Filter -> Engine Oil Main Gallery Boss Wngine Main and Supplemntal Galleries ->

It appears.

 

***edited***
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