EXHAUST HEAT WRAP need info....

Does anyone have data on the effect of heat wrap on the exhaust header , positive or négative ...

Or no effect at all , there is a lot of opposing théory on the net.

The first thing I will say is that there is nothing inherently wrong with the concept of some form of heat shield or heat insulation on an exhaust manifold/header/turbo manifold. It's normal for exhaust manifolds/turbo manifolds to have a heat shield from the factory, to protect other components from the heat that comes off and to keep the heat from getting into the cabin. Also, more exhaust temperature is generally better for spooling a turbo especially at low rpm where the engine doesn't make so much heat. It's also better for warming up the catalyst on a cold start, but that's not a normal concern area. You could characterize the performance benefit on a turbo engine as small at best, and on a naturally aspirated engine I suspect the performance impact is basically negligible, ie don't expect any gains at all.

Now, if you've got an unwrapped exhaust part heating up your cabin making passengers uncomfortable then some kind of insulation is preferable. Tired of hot floor boards? Consider heat wrap, ceramic coat, or if possible a metal heat shield similar to an OEM part.

Where the controversy comes in is whether the wrapping itself causes a degradation of the part by whatever mechanism. I don't have any special information on that. I've run heat wrapped welded turbo manifolds before, but not long enough to give even a personal anecdote about their durability versus unwrapped. In my opinion heat wrap looks ugly, much worse than unwrapped, ceramic coat, or OEM heat shield. But they may still be functional. Certainly with stock heat shields a lot of heat is retained in the manifold and they still last for many miles.

Raymond has covered the general principle - Pretty much if we can keep the heat in the exhaust manifold we tend to provide more energy to drive the turbo and hence we see an improvement in spool. The reality is that any difference is probably incredibly small and the more relevant gain is reducing temperature in the engine bay and the heat soak that results. I've personally had trouble finding a heat wrap that offers a long life without degrading and falling to pieces. My preference is to have the headers ceramic coated. This also has the advantage of protecting the manifold from corrosion and improves the looks of the coated part.

Thank's for your time and answer.

My question came from a build i did [ JEEP 6cyl. 4.0l + cam + header + porting ]

The intake manifold and exhaust very close on the same side of the engine , i assume it would be benefic to had heat wrap on the

exhaust header to lower the intake manifold temp. for better performance.

With the answer i got , think i did the right thing ...

Now that it's five years later, I'm curious if HPA's opinion of header wrap has stayed the same or evolved?

I have a situation in which the unwrapped race headers seem to be cooking everything, and since I still have the mostly factory wiring harness I'm concerned that I will start to have electrical issues. I already have an issue where the AIM water temp sensor seems to have an internal fault, and temperature in the electronics box gets quite high. I added a fan to the E-Box and I'm working on upgrading to a higher flow electric radiator fan, but I'm wondering if I should be planning now to get the headers ceramic coated.

In theory, it's all good, but there can be two significant issues...

a/ the radiated heat cools the hot parts, and by insulating the parts they can run significntly hotter, possibly to the point where the material breaks down. or weakens to the point of failure. Examples are lower quality turbine housings and mild steel exhaust manifolds.

b/ there can be a problem with the wrap holding moisture against mild tubing and causing premature failure, but painting, or coating, the parts will reduce this, as does painting the wrap with a barrier paint. One might think the exhaust would boil off any moisture, but with wet, or worse, salted roads the spray from the front tyres can keep the exhaust relatively cool, especially under light load where less heat is generated.

It's not uncommon for the exhaust manifold to be fixed to the inlet (or other way round, or even for them to be cast as a single assembly. This is to help vapourise the fuel and/or warm the charge air to impreove driveability, economy, emissions, and speed up bringing the engine to operating temperature.

As you're in Canada, and I expect you use the vehicle in winter's very low temperatures, you need to figure if the trade-off is worth it - you may be able to figure out a simple heat shield you can weld/bolt to the exhaust, or where it can protect the wiring, etc. If you do decide to wrap, bear the above in mind.

Hi Gord,

Thanks for the insights. The original poster is indeed in Canada, but I'm in Miami, Florida myself. No road salt or low temps here. The issue I'm trying to understand is high engine bay temps on hot days (85F/30C and up).

Those are some good points. Where I get a little confused though is I see most discussions of heat wrap talking about issues in road cars and/or turbocharged cars. If you remove those two components of the situation, does the assessment change? The car in question, for me at least, is almost entirely a dedicated track car. The only road use it sees is driving to and from the track, and some road tests. It's a naturally aspirated six cylinder, and the headers are stainless steel. It's garage kept. Does the calculus change in any significant way? Or is ceramic coating still the way to go?

Thanks!

Ah, in that case, no real issues - might come down to cost and availability? Don't recall using ceramic, the wrap should work well, with maybe ceramic on the intake manifold to reduce it's heating?

IMO, anything that reduced underbonnet (hood) temperatures should be considered, and you may also notice easier starting when hot. Something to watch out for, that may be a minor concern, is that the exhaust components down-stream will be a little hotter and in extreme cases may need additional heat control.

I've not had issues with wrap degrading quickly, but a tech I worked with found 6 coats of black DEI silicone sealant works wonders. It's time consuming but worth it. It protects the wrap, the piping, and drastically reduces the risk of absorbing flammable fluids. With that combo I found temp readings indicate this reduces radiant heat more than quality ceramic coatings I've used like Jet Hot 2500, but that will vary with your application of the wrap, wrap type, etc.

Thanks for the clarification. It sounds like for a 99% dedicated track car header wrap on a quality stainless header and is naturally aspirated engine is generally fine. For a road car with moisture/salt, a forced induction application, or dubious quality headers, the potential for problems becomes much higher. Thanks!