Got a couple questions about the LS7
04-19-2006, 05:45 PM
#1
Got a couple questions about the LS7 Hey guys I was reading some of the stats on the LS7 and I understand that a lot of racing technology has been put into it but I dont understand some of it so I was wondering if you guys could quickly expain a couple things to a noob. Maybe this will help others out as well
For one the LS7 has sodium filled exhaust valves.... sodium?? like salt? When I was talking to someone who had a WRX STI I remember them saying something in their engine was sodium filled as well. What advantage does this provide?
2. And this is one I should know but how is the dry sump oiling system different than a avg passenger car oiling system and how does it make sure oil is flowing through the engine even under accelerative, braking and cornering forces?
3. the LS7 uses titanium connecting rods. I understand the weight savings titanium would have and how important saving weight is in all reciprocating mass in your engine and drive train but for the most part isnt it better in high stress applications to make the componets that are dealing with the forces of combustion out of a alloy that can expand and contract slightly like iron? Obviously the block is aluminum which is also known for being quite rigid so very rigid materials can be used, but isnt titanium the most rigid alloy you could use? Doesnt this meen that if the rod goes it will more than likely shatter complelty tearing appart everything in that cylinder from the piston to the sleeve to the head?
Sorry for the noob questions
Thanks
For one the LS7 has sodium filled exhaust valves.... sodium?? like salt? When I was talking to someone who had a WRX STI I remember them saying something in their engine was sodium filled as well. What advantage does this provide?
2. And this is one I should know but how is the dry sump oiling system different than a avg passenger car oiling system and how does it make sure oil is flowing through the engine even under accelerative, braking and cornering forces?
3. the LS7 uses titanium connecting rods. I understand the weight savings titanium would have and how important saving weight is in all reciprocating mass in your engine and drive train but for the most part isnt it better in high stress applications to make the componets that are dealing with the forces of combustion out of a alloy that can expand and contract slightly like iron? Obviously the block is aluminum which is also known for being quite rigid so very rigid materials can be used, but isnt titanium the most rigid alloy you could use? Doesnt this meen that if the rod goes it will more than likely shatter complelty tearing appart everything in that cylinder from the piston to the sleeve to the head?
Sorry for the noob questions
Thanks
Last edited by sciff5; 04-19-2006 at 06:26 PM.
04-19-2006, 08:06 PM
#2
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I believe the sodium crystals, (I think it's in crystal form) in the exhaust valve stem conduct heat away from the exhaust valve head giving the valve longer life. Some of the racing valves used by Porsche and probably many other racing programs are sodium filled. The intake valves, which are quite large in the LS7, are solid (I think) titanium to lighten them up. The hollow stem sodium filled exhaust valves are undoubtedly lighter than solid stainless valves too. Lighter moving parts = more hp due to less friction and less parasitic drag. Many, most, serious racing engines are dry sump for some of these reasons: 1. They can run a greater volumn of oil because it is stored in a seperate oil tank, 2. The oil accumulating in the deepest part of the oil pan is sucked, scaveaged, out quickly so excessive oil doesn't "rope" around the crankshaft creating hp robbing drag, 3. There is a reduced tendancy for the engine to be starved of oil under all conditions because there is a ready supply in the seperate oil tank. I'm not a metallurgist but I think the titanium rods are pretty much just for hp freeing-up weight savings in the rotating assembly. There are numerous titanium alloys and I'd expect these rods are made of pretty tough, not brittle, stuff.
04-19-2006, 09:50 PM
#3
Originally Posted by GMW-CSL
I believe the sodium crystals, (I think it's in crystal form) in the exhaust valve stem conduct heat away from the exhaust valve head giving the valve longer life. Some of the racing valves used by Porsche and probably many other racing programs are sodium filled. The intake valves, which are quite large in the LS7, are solid (I think) titanium to lighten them up. The hollow stem sodium filled exhaust valves are undoubtedly lighter than solid stainless valves too. Lighter moving parts = more hp due to less friction and less parasitic drag. Many, most, serious racing engines are dry sump for some of these reasons: 1. They can run a greater volumn of oil because it is stored in a seperate oil tank, 2. The oil accumulating in the deepest part of the oil pan is sucked, scaveaged, out quickly so excessive oil doesn't "rope" around the crankshaft creating hp robbing drag, 3. There is a reduced tendancy for the engine to be starved of oil under all conditions because there is a ready supply in the seperate oil tank. I'm not a metallurgist but I think the titanium rods are pretty much just for hp freeing-up weight savings in the rotating assembly. There are numerous titanium alloys and I'd expect these rods are made of pretty tough, not brittle, stuff.
The valves are filled with the element sodium, not salt (Sodium Chloride). The primary purpose of a lighter valve is to maintiain control due to less inertia.
The primary purpose of the dry sump system is to have a ready supply of oil to the pressure pump, particularly under high-g cornering. Reduced windage is also a horsepower-saving advantage.
04-19-2006, 11:31 PM
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Originally Posted by Katech
The valves are filled with the element sodium, not salt (Sodium Chloride). The primary purpose of a lighter valve is to maintiain control due to less inertia.
The primary purpose of the dry sump system is to have a ready supply of oil to the pressure pump, particularly under high-g cornering. Reduced windage is also a horsepower-saving advantage.
The primary purpose of the dry sump system is to have a ready supply of oil to the pressure pump, particularly under high-g cornering. Reduced windage is also a horsepower-saving advantage.
Sodium filled valves allows much greater heat dissipation... That is the primary reason for using them. The weight savings is just an added benefit.
04-20-2006, 10:09 AM
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Originally Posted by Dune-LS1
Sodium filled valves allows much greater heat dissipation... That is the primary reason for using them. The weight savings is just an added benefit.
04-20-2006, 01:07 PM
#6
TECH Apprentice
The sodium bounces/flows up and down inside the valve stem, as the valve moves thus transferring heat from the very hot valve head right up into the guide and no doubt the oil wet collets.
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