Are sodium filled exhaust valves the way to go?

thexav

Pro Tuner
Staff member
Points
357
Car
2002 Clio 172
Just been reading up on a new Kia engines and it boasted that it had Sodium filled exhaust valves?

What's the point? Does it make a difference? Is this the future of engine technology?
 

obi_waynne

Administrator
Staff member
Moderator
Points
887
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
They carry the heat away and reduce the risk of premature detonation, often caused by the hot exhaust valves (intakes are generally cooled by the incoming air)

The Sodium liquifies, which takes out a lot of heat but it also allows the valve to cool more effectively by running more heat up the shaft to the valves bed where it is cooled.
 

thexav

Pro Tuner
Staff member
Points
357
Car
2002 Clio 172
When the sodium goes to liquid does it expand? Surely that's not good.
 

obi_waynne

Administrator
Staff member
Moderator
Points
887
From
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
The expansion is not that significant, converting a metal to a liquid does take out a lot of heat anyway, and it transfers heat away more quickly. The added pressure from it being hot will act like a pressure cooker and allow it to reach much higher temperatures (although it's unlikely you'll reach the upper limits and get it to boil in a car engine.)
 
Top