Just seems to me that the heat wrap will transfer the heat onto the CPS itself. A heat shield with some standoff between it and the CPS, I totally understand, but wrapping the CPS seems like best case no-effect, worst case insulates and creates more heat. Explain like I'm a 5-year-old please.

This is the heat wrap I've seen mentioned in the past:

 

CPS came with a heat shield from the factory, do you have that? The factory one is painted silver, over time the paint comes off, and it gets coated in oil. Heat gets transmitted to or from the CPS three ways, conduction, convection, and radiant heat.

Conduction means touching. The CPS is bolted to the block, so starting from a cold engine as the engine block gets hot, the CPS will start to heat up until it is equal to block temperature - because the block is cooled by coolant let's call that 200 degrees. We could assume it will usually be at or near this temperature on a truck that is driving down the highway.

Convection means movement of some medium - usually air or water. The engine is cooled via convection by the coolant. For the CPS, there is air moving around it, we can assume more at higher speeds, less at lower speeds. The question is what is the air temperature. There is some air coming through the radiator - assume that air is around 200 degrees. And there is some coming under the truck, lets assume maximum 100 degrees. So likely the CPS is being cooled by convection.

Radiation/Radiant heat is the heating by electromagnetic waves. The way the sun heats the earth. On a cold engine, the 200 degree engine radiates heat to the CPS, heating it, but once the CPS is at 200, the block cannot heat the CPS any more. However, the exhaust manifolds, pipes, and converter are located near the CPS. They operate between 500-700 degrees on a running engine. The manifolds are cooled via convection by the air running past them. And they are cooled via conduction where they are bolted to the head. However the exhaust gases are constantly heating them. And they are radiating heat toward the CPS.

I have noticed the CPS failures typically occur when an engine is either hot, or perhaps when a hot engine is shut off and let sit for a few minutes - not too short, and not too long. Let's say 20 minutes. That is enough time for the exhaust manifolds to radiate enough heat to raise the CPS temperature to let's say 300-400 degrees from radiant heat. Less than 20 minutes, it does not have enough time to raise the temperature, longer, and the surrounding air cools everything off. Pour water down the back of the block, it cools the CPS nad you can start the truck.

Now, the radiant barrier is interesting. Aluminum reflects 98% of the radiant heat, so only 2% gets through. Then, once the heat shield itself is a little warm, let's say 220 degrees, it only radiates 2% of its heat energy (assuming both sides are aluminum faced) (called emissivity). I wrap the factory cover with aluminum foil, and it has an air gap with the CPS. Air conductivity can be thought of as .0057% The material you linked to is not aluminum both sides but fiberglass on one side, which is .015% or around 2.5x as much as air. Also, fiberglass has a radiant emissivity of around .8-9%, so 4 times that of aluminum.

The advantage mostly comes from the reflectivity of the aluminum. The linked product would work best on a situation where you can't have an air gap on the back side.

 

Ahhh, yes, awesome. Dang. So thorough! Thanks for posting that!

So... yes, the factory heat shields remain intact. Would it be beneficial to wrap the CPS in that linked wrap still? Or more beneficial to wrap the heat shield?

Also, my 2002 doesn't have the plastic under-shield, obviously, but my 2004 surprisingly still does. Should that come off to help dissipate heat while it's sitting after having been run? Or are the benefits gained by removing it (if any) offset by the downsides of removing it...

 

I believe most effective is wrapping the factory plastic cover in aluminum foil - inside and out. If you don't have that, form and aluminum shield that will fit between the exhaust manifold and the CPS without touching either - you can probably buy some aluminum ductwork from Home Depot for around $5 - put a hole in it, bend it, and bolt it to the oil pan using the factory oil pan bolts.

 

DEI gold wrap!

https://www.summitracing.com/parts/d...yABEgLlpfD_BwE

 

Does anyone know the part number for the heat sheild it's self? I can't find it. And mine has gone missing probably explains why the sensor has been replaced 2 times in the past year. Also what if instead of beefing up the heat shield itself why not wrap the exhaust with heat wrap at that location? Thoughts?

 

It’s no longer available to purchase new. It’s not really a heat shield but more a cover made from plastic. You can find one from a breaker or on EBay. Some folks on here have wrapped the cover in tinfoil or other metal to try to reflect the heat away.

 

You don't need the original, in a pinch you can fabricate piece of aluminum sheetmetal and put it between the sensor and the exhaust manifold. You can wrap the exhaust manifold if you wish, it will need to be white or silver to have low emissivity.

 

I used a chunk of my old aluminum license plate, bent in an L shape, and used a bolt hole that was unused next to the oil pan. Looks like a very effective barrier. Sorry no photo.

 

Extinsr - Probably one of the best explanations I have ever read on this forum. Thank you.