Benefits of valve jobs on FSI engines

[obi_waynne]

Are the benefits of a 3 or 5 angle valve job still worth doing on FSi (direct injection) engines?

I'd be very interested to hear your comments on this as more an more makers are using direct cylinder injection fuel systems.

 

[HDi fun]

What is a 5 angle valve job? Is it just multiple radii for the perimeters of the valve seats?

 

[obi_waynne]

Yes that is the idea, the angle increases on each cut. The more cuts the merrier, a 5 angle is pretty much a smooth curve. 3 will usually suffice.

 

[HDi fun]

As long as the valves seal effectively and without burning or other damage I really cannot see the point at all. Regardless of the fuel delivery system.

 

[obi_waynne]

Generally a valve job allows significantly more air into the engine as it fills the cylinder more efficiently. It also allows fuel to mix better hence the question about FSI engines, where the fuel is not delivered with the air charge but rather directly into the cylinder.

 

[HDi fun]

Ahh - OK so you're thinking of smoothing off the valve seat edges in the interests of airflow. In which case yes, and car will benefit.