Racing valves

[Commuta_Busa]

Every so often I post some semi obscure question. Sometimes I don't really get an answer but it never hurts to put it out there.

I know of only a few people that have gone to Inconel alloy (IN-751) valves. I also know that some go with Nimonic 80A but I don't see what the advantage is over Inconel since they have very similar heat fatigue limits/creep resistance. Maybe it's the additional corrosion resistance.

My question is if anyone has heard about anyone needing to go with Nimonic 90 yet or is considering it? ??? I know that some "motorcycle teams" use them but because of confidentiality blah, blah names can't be mentioned.

 

[m_ridgeway]

http://www.suppliersonline.com/propertypages/Inconel751.asp

heres a sheet on inconel, just for info sake

 

[m_ridgeway]

sheet on the other

http://www.suppliersonline.com/propertypages/Nimonic90.asp

 

[m_ridgeway]

only diff i see is thermal conductivity and expansion. which is probably why the like the nimonic in high heat place such as turbines, maybe transfering same to the bike?

 

[Commuta_Busa]

thanks, yea I know the properties/specs, I even know some of the companies making them for motorcycles and others. They have a much higher tolerance and are ideal for turbo engines. The problem is no one can share any points of contact. I contacted a "race team" I suspect uses them and when I started asking about them they would only say that they know what they are and that's it.

 

[m_ridgeway]

points of contact? are you trying to figure where to get them?

 

[Commuta_Busa]

just trying to understand why some have switched to them or if they are considering it what their reasons may be. Better thermal resistance is a good reason but you can also coat valves and chambers to increase their durability so there may be more than one reason to swap over to Nimonic. I just can't dig up someone who will talk about them in a specific race application. I could probably chat for hourse with a diesel guy why they use them but the application just don't fit well.

 

[m_ridgeway]

i dont know man but just for conversation. maybe the expansion has something to do with it. say if one expands more youll lose some seat pressure and at high boost you need all you can get?

 

[Commuta_Busa]

yes, it's all about optimizing durability and the weight of the valves. If you wanted to ignore durability and were swapping valves after each sprint you could run titanium with just a thermo coating. To make things more durable you've got Stainless Steel but they're heavy. Hmm more weight, more spring pressure, etc.

 

[m_ridgeway]

heres a quote from someone that sales them

Nimonic 80A has an increased operating temperature over 214N and higher corrosion resistance.

looks like youre pretty spot on with durability.

 

[Draco1340]

The material property that I would think would be most important is thermal conductivity. The only way that a valve sheds heat is through the stem and into the guide, or through the valve seat area and into the guide. The valve seats contact area on a modern race engine is so small that very little heat gets out that way, so the stem is the dominant heat sink. Back in the days of massive 16 cylinder aviation - piston engines, the valves were big enough to actually fill them with sodium and have the heat transfer be done with liquid sodium out through highly conductive guides. The materials listed have pretty poor thermal conductivity meaning they have to operate at close to combustion temp. Even Stainless has crappy thermal conductivity values of around 20 W/M-k . Thus the heads sometimes melt right off.