Exhaust wrap. Good or bad?

[ChillyBear]

Well, is it good or bad for efficiency? I want to do a partial grill block and a bely pan and I want to do this to keep my engine bay cool. Is this going to drastically affect mileage or the life of my exhaust system?

[spydyr]

I've had wrapping cause premature rusting. You have to make sure its on good and sealed so that moisture, which it will anyways, doesnt get in. The heat makes it more prone to rusting.

No over all effect on anything except ambient temperatures in my case.

[ChillyBear]

good, because I want to use coroplast for my belly pan. I may just use aluminum for the exhaust areas.

[RobertSmalls]

If you can get the cat to warm up faster and stay warm longer, that will make up for some of the engine-off and low load conditions where many of our cars operate.

[Christ]

Rust proof coatings before wrapping/insulating will help prevent the rust from forming.

Hotter exhaust piping should keep the exhaust gasses from cooling as much (part of the point of header wrap), which should make exhaust flow stronger, higher velocity, increasing scavenging. It's theory, not practice, that covering the entire exhaust will achieve bigger gains in this department.

At the very least, it will stop parts of the exhaust from cooling as much while the engine is off or at low load, where there is less heat energy in the exhaust.

Faster exhaust heating times will also mean that less moisture gets trapped in the exhaust from short-distance operation.

[luvit]

what rust-proof coating are you talking about? it could stink at high temps.

[Christ]

high-temp ceramics or alumina coatings. They're designed to help prevent rusting.

[Lazarus]

Here's a little more from a previous thread.

[miket]

Would the higher temperatures and the absorbed water and salt in the wrap cause 409 stainless to have crevice corrosion or crack welds?

[Olympiadis]

I've used exhaust wrap since the earl 1990's, and I still do. It works very well on stainless. You can use it on mild steel, but it will drastically shorten the life of the metal. Don't bother trying to keep moisture off of it. The exhaust is full of moisture, and besides, it's not the water but the Oxygen and high temp that eats the mild steel. Mild steel will glow red during normal operation and is prone to Oxygen contamination similar to a weld.

Wrap will bring O2 sensors and Cat up to temp quicker, and it drastically increases the life of other under-hood components that would normally be exposed to the radiant heat from the exhaust.

Gains in performance or scavenging are too small to measure even on a 500hp engine, and so should not be the reason for using the wrap.

Keeping O2 and Cat up to temp, and fast O2-switching is measurable.
Less degradation of under-hood components from radiant heat becomes obvious.