They must be very poorly designed and cheap aftermarket manifolds you have seen failing then.

I myself have only seen one case of a wrapped fabricated manifold breaking which was a Jansport mild steel system. I believe this manifold failed mainly because the engine mounts on the car it was fitted to were shot and it was more the increased movement then the heat wrap which snapped the manifold. The jansport manifold broke on the pipe where the collector is not on a weld and well away from the wrapped section.

The weld is generally the strongest part of any fabricated material partly because of its increase in thickness but also due to moleculer structure. Stainless steel and mild steel used for exhaust sections are easily capable of the increased teperatures they are subjected to when a heat wrap is fitted.
The mild or stainless steel is a much more ductile material then an oe cast manifold and has greater resistance to fatigue then cast iron.

An oe cast manifold which is made from cheaper materials and mass produced is much more likely to fail having been heat wrapped then a well made fabricated exhaust manifold wheter stainless or mild steel.

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Originally posted by ianofbhills
That statement is incorrect.

If the manifold is cast like most factory fit manifolds and most turbo manifolds then indeed the extra heat invoked by wrapping the manifold with the heat wrap can increase the risk of cracking it.

After market manifolds tend to be fabricated from bent tubes hence their better gas flow properties (larger diameter) and increased engine performance. Wheter they are made from the mild steel or stainless they will both be fine for manifold wrapping and will not crack because of it.

Manifold wrapping is an old way of helping to keep the exhaust gasses moving through the exhaust system as efficiently as possible by preventing the heat transfer to the exhaust pipe. If you look at motorsport a better way of doing it now is to ceramic coat the manifold inside and out which has all the benefits of the heat wrap with none of the negatives. I.e the heatwrap tends to get torn and damaged after a while and needs to be replaced, heat wrap can trap moisture next to a mild steel exhaust increasing the risk of corrosion.

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That statement is incorrect.

If the manifold is cast like most factory fit manifolds and most turbo manifolds then indeed the extra heat invoked by wrapping the manifold with the heat wrap can increase the risk of cracking it.

After market manifolds tend to be fabricated from bent tubes hence their better gas flow properties (larger diameter) and increased engine performance. Wheter they are made from the mild steel or stainless they will both be fine for manifold wrapping and will not crack because of it.

Manifold wrapping is an old way of helping to keep the exhaust gasses moving through the exhaust system as efficiently as possible by preventing the heat transfer to the exhaust pipe. If you look at motorsport a better way of doing it now is to ceramic coat the manifold inside and out which has all the benefits of the heat wrap with none of the negatives. I.e the heatwrap tends to get torn and damaged after a while and needs to be replaced, heat wrap can trap moisture next to a mild steel exhaust increasing the risk of corrosion.

im not to keen on it myself....

if the manifold is stainless it can cause it to crack as it wont let the heat out

make sure you have no oil leaks and that no oil gets on it otherwise it soaks in and when it gets too hot it will catch light

heat wrap or manifold wrap,wouldnt recomend using it with an after market manifold as the excess heat can cause the maifold to crack:)

wot is the stuff called mate?

yer it is worth it mates as it keeps the heat in the exhaust more and not your air filter i am doing mine the weekend well worth the 40 quid the stuff is

whats the benifits?

would it be worth me doing this on my c20xe?

cheers

james