I was browsing northernautoparts.com for another batch of oil (change time coming soon), and spotted odd things that sppse to be wrapper around exhaust pipes (each one individually) where they sticking out from engine (dont kill me for not knowing proper term for that, please). Presumably that stuff should cool engine compartment down by elimination of radiating heat from pipe heads up to 70%, and hence increase performance.

Anyone tried something like that? It looks kind of fishy to me. Wouldnt heads crack faster from such overheating (i presume they overheat when they couldnt eliminate surface heat)

Where are you seeing this on their site?

wow.. expensive stuff

XCanuk - thanks! I totally forgot to add link when i pressed "post"..

its like 70$ and if its indeed helps so much - i wouldnt mind to cough them up.. Problem is - if its really works. And how the heck i can get to those pipes in X anyway - they under engine, i sppse? Just wanna at least measure diameter to stop thinking about it

The problem with the Xterra's "pipes" are that they are a cast piece and it would be near impossible to use that stuff on them.

Off hand, I don't know of one material, given the thickness required, that would cut enough heat for their claims. I would guess that its only a light jacketing material, closer to being an air cell aluminum foil or the newer versions of asbestos jacketing used at one time.
It would serve more as a heat protection, similar to a heat shield. Overall heat reduction = minimal.
BTW.. I work in Mechanical Insulation

And aren't our current pipes junk? This would probably be too much heat for stock... maybe if you switched to SLR or something... but even then... SLR hasn't been known to be the most reliable... but looking at the picture: it looks like it could be wrapped better...

Nope, wouldn't work on the stock setup for several reasons:

1) The exhaust manifold is a little tiny cast POS so it has no real pipes to speak of and it's only about 5 inches from the head to where the manifold ends.

2) At the end of the manifold the next thing in line are the catalytic converters. This is most surely the biggest source of heat in the engine compartment on the Xterra.

3) Wrapping the catalytic converters is probably not a good idea.

4) Once you get past the cats and finally to some exhaust pipe that you could wrap, there probably is no point because it's below and behind the engine compartment and is still no competition to the heat the cat creates anyway.

On the other hand, if you have headers and you relocate the cats then these things may work I suppose, but I doubt it would have a significant impact on anything.

Passive systems, such as insulation only retard the entropy rate. An active system like functional dual hood scoops that forced a downdraft over each of the exhaust manifolds might do a better job. Of course, you'd have to have the minerals to cut holes in your hood and be held in the same regard as any of those posers with the cheesy "hood scoops" that don't actually scoop anything other than cash from your wallet.

I'm uncertain if at running speed, the heat radiating from the manifolds significantly increases engine compartment temperature. Perhaps if you had skid plates there'd be a reduction in turbulence, and thus an increase in engine compartment temperature.

Those wraps are mainly to keep the exhaust gas temp up for greater exhaust velocity. Not really to keep engine bay temp down. Poor mans ceramic coating....