Titanium and inconel valves

dank GN

BlackArts Automotive (661)993-8277
Joined
Jan 11, 2009
i have a question regarding the Ti valves in stage heads . I’m not quite sure why they wouldn’t work in turbo applications seeing that the melting point of Ti is higher then inconel . And the whole point of switching the valves is to better hold up to the high exsaust temperatures . According to this the melting point of inconel is 2540*F and the melting point of Titanium is 3040*F. So why are inconel valves better suited for turbo motors?
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The melting point tells you very little about the properties. Inconel retains its strength over a large temperature range compared to titanium and has superior creep and stress rupture properties.


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The melting point tells you very little about the properties. Inconel retains its strength over a large temperature range compared to titanium and has superior creep and stress rupture properties.


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That makes sense . Thanks for the info
 
Why worry about the valves "melting" when alum pistons and alum heads have a MUCH lower melting point?

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Is that the new style low compression piston everyone is talking about?
 
Why worry about the valves "melting" when alum pistons and alum heads have a MUCH lower melting point?

Ouch!

What about various materials rate of expansion & lubricity? Are there certain combinations of valve stem, valve guide materials & clearances that should be considered?
 
Iv seen EGTs as high as 1500*F . I see what you are saying but I belive these temperatures they are staying as melting points are sustained temps . Basiclly the part temps would have to reach that temp for it to begin to melt which is how I am depicting it
 
Iv seen EGTs as high as 1500*F . I see what you are saying but I belive these temperatures they are staying as melting points are sustained temps . Basiclly the part temps would have to reach that temp for it to begin to melt which is how I am depicting it

1500F is low, I been as high as 1800F with no signs of degradation on the pistons or the valves. For me that probably means it wants more timing for the fuel I’m using. Point being that the valve will see much higher heat and it’s only chance to dissipate heat is when it’s on the seat.
AG


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Why worry about the valves "melting" when alum pistons and alum heads have a MUCH lower melting point?

View attachment 310528

Because the exhaust valve has all that heat concentrated onto it during the exhaust stroke. The piston face might be seeing 1000F, but the exhaust valve will be well above that because all the heat that's dispersed across a 3.8" diameter piston face gets crammed past a 1.5" diameter valve. As the air moves through the valve opening during the exhaust stroke, it's actually getting compressed, which raises the temperature even more.

And then the valve has to disperse that heat into the head via the valve seat while it's closed. The piston shares a much larger interface with the cylinder wall (which is itself surrounded by water), rod pin and rod, and gets relatively cool oil splashed up on it from the crank. The pistons are able to shed the heat much better than the exhaust valve can.

Which is why we get away with aluminum pistons.
 
My stage had the egt probe at the base of the turbo...At 27psi, I routinely read 16 - 1700*. C16 fuel.
 
1600-1800 is closer to what you would probably see and is consistent with my data logs.
AG


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I answered before reading to the end of the thread.
Those temps are at the beginning, middle and end? Or just at the finish?
 
I answered before reading to the end of the thread.
Those temps are at the beginning, middle and end? Or just at the finish?

Below is a trace from 2012. I have the marker at the 330 ft mark and you can see from the values in the left column that they are already at 1650+ and get to about 1800 by the 8th. The right hand side of the column will tell you the Absolute max. some were not at 1800. At the start of the data log from just mashing the throttle it started out at 1100 ish.

So basically I would build around, and anticipate 1800F when selecting valve materials for this application.

Edit - I should also add that these were 1/8 non-exposed tip TC's. The are small so they should react fast but the non-exposed tip slows that reaction. IIRC I think the tech sheet on these gave them a 1 second response time so that's pretty slow.
AG.

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