Hello Demetris,
Demetris said:
SydneyRoverP6B said:
Wrapping tubular manifolds with special heat cladding does reduce the amount of heat radiation, but the downside in this process is that the life of the manifolds are significantly reduced. Less than two years being common place so I am informed.
Can you explain why this happens?
Demetris
The tubing, either mild or stainless steel that is used in the construction of tubular manifolds is quite thin, that is to say..the wall thickness. As such the surface temperature of the tubular manifolds in comparison to the cast iron manifolds is considerably greater. To prevent the possibility of severe burns, should unintentional contact be made with the hot tubes, not to mention reducing the significant increase in under bonnet temperatures, wrapping the tubes with an exhaust manifold cladding is sometimes used.
The use of such helps to prevent possible heat damage to the plastic fuel lines and rubber hoses along with electronic ignition components etc. By retaining so much of the heat, the tubular manifolds also work more efficiently in that the exhaust gases maintain a higher velocity, thus exiting the system more efficiently. Cooler exhaust gases by comparison travel with reduced velocity, and the system then works less efficiently.
Whether a person driving a P6B fitted with bare tubular manifolds then wrapped tubular manifiolds would be able to pick the difference from a power perspective would remain to be seen.
Typically stainless steel tubular manifolds have a 10 year manufacturers warranty, while mild steel tubular manifolds have a 3 year manufacturers warranty. These periods are "typical" and don't represent all such warranties.
Now the downside......wrapping tubular manifolds with the appropriate material designed for such whether they be stainless or mild steel will result in a significant reduction in the useable life of the manifold. It is my understanding that the degredation is both a combination of moisture retention by the wrapping which expediates the corrosion process, combined with the heat generated within the tubes being unable to escape. The corrosive effects of the trapped heat attack the very structure of the tubes, eroding them from the inside out.
By wrapping tubular manifolds you will also void the manufacturers warranty. When I was investigating the pros and cons of using extractors on my 4.6, this was one area that all manufacturers had in common. A void warranty. :shock: Once wrapped, removal will leave definitive evidence which the manufacturers will be able to see, so should the manifold crack or display holes where the metal has corroded away, no reponsibilty for repairs or replacement will be offered. The warranties typically state that the use of "heat wrap" products will void the warranty.
A far better alternative to wrapping is ceramic coatings. Such coatings help to reduce the level of heat radiation while slowing the corrosive process. As an example...a bare tubular manifold up to normal temperature will measure in the region of 400 degress C, measured 1" away from the tube where it curves away from the cylinder head. The same tube with a ceramic coating will typically measure half that figure.
Warranties typically do not make mention of ceramic coatings, and in some cases the manufacturers themselves will provide such coatings as an option before purchasing.
Ron.