Partially wrapping exhaust manifold/header...

[Ma70.Ent]

I've been wondering, could you partially wrap an exhaust manifold/header (basically not completely wrapping it) to get some of the benefits, and not the drawbacks? The drawbacks I hear of are mainly faster rust/corrosion due to the moisture being trapped within the wrap. Exhaust wrap is pretty cheap so to get some of it's benefits without it's disadvantages would be pretty cool.

 

[RazoE]

wouldn't that be akin to putting your pants on half way?

partial wrap might have some adverse affects, I'm not an expert by any means, but wouldn't the unwrapped parts give off more heat then the wrapped parts, and warp..?

 

[Ma70.Ent]

wouldn't that be akin to putting your pants on half way?

partial wrap might have some adverse affects, I'm not an expert by any means, but wouldn't the unwrapped parts give off more heat then the wrapped parts, and warp..?

I'm not an expert either, that's why I posted this up. Hopefully we can get more input on this

 

[Keros]

I'll also retain the claims of not being an expert.

But consider that a metal pot handle will still get hot when the pot is on the burner, dispite the handle not being connected to the heat source. Most, if not all, metals (especially cast iron), have a high thermal conductivity. It's unlikely that there will be a large temperature difference in any area on the metal itself, particularly between the wrapped and unwrapped areas because the heat energy will move throughout the entire component via thermal conductivity. It could be a problem if there was something with a high specific heat (like water) contacting one part of the metal and not another.

That said, insulating the part is done to decrease the thermal conductivity between the ambient air and the part in question... so wrapping some area of the part and leaving other areas exposed would help you a bit, but still not see the full benefit. If we're talking about cast iron... cast iron takes a LOOONNG time to rust. That said, any wrapped parts will still trap moister, and potentially the boundries between the wrapped and unwrapped parts will get more moister, but a cast iron part is going to take a hella long time to rust.

Why not ceramic coat the parts then wrap them? That's pretty much all benefit, with no downsides.

 

[super.secret.supra.club]

I'll also retain the claims of not being an expert.

But consider that a metal pot handle will still get hot when the pot is on the burner, dispite the handle not being connected to the heat source. Most, if not all, metals (especially cast iron), have a high thermal conductivity. It's unlikely that there will be a large temperature difference in any area on the metal itself, particularly between the wrapped and unwrapped areas because the heat energy will move throughout the entire component via thermal conductivity. It could be a problem if there was something with a high specific heat (like water) contacting one part of the metal and not another.

That said, insulating the part is done to decrease the thermal conductivity between the ambient air and the part in question... so wrapping some area of the part and leaving other areas exposed would help you a bit, but still not see the full benefit. If we're talking about cast iron... cast iron takes a LOOONNG time to rust. That said, any wrapped parts will still trap moister, and potentially the boundries between the wrapped and unwrapped parts will get more moister, but a cast iron part is going to take a hella long time to rust.

Why not ceramic coat the parts then wrap them? That's pretty much all benefit, with no downsides.

well said keros, well said.

ed.d.

 

[tlo86]

i have heard of over-insulation of exhaust components.. what exactly is that?

 

[Ma70.Ent]

Hmmm, any of you smart guys wanna contribute?

 

[benchwarmer]

I don't pretend to be smart(no one would believe me anyway) but as I recall thermal wrap causes premature rust due to the trapped heat, not moisture. Remember that rust is oxidation and adding heat to an oxidation reaction will accelerate that reaction. By preventing the heat from radiating out of the exhaust you cause the temperature of parts like the manifold to increase tremendously which dramatically decreases the life of the part.

If your goal for the heat wrap is to improve scavenging you're better off using a better designed exhaust setup, such as a quality header, since that gives all around better performance without sacrificing service life.

If you just want to decrease under hood temperatures you should try to duct the heat away using a vent scheme. That or you can just heat wrap the intake ducting so that the under hood temps don't warm up your intake charge.

Partially wrapping the exhaust would help alleviate the corrosion problem since not all of the heat is trapped inside the manifold. However, Any heat trapped in the manifold will just cause the manifold to run hotter and, since the manifold isn't completely wrapped, it will radiate just as much heat as it would without the partial wrap. I stand by my belief that heat wrap is the devil and should never be applied to an exhaust component you intend to keep.

 

[Ma70.Ent]

Here's an interesting link about header wrap....(it defends it!)

http://www.heatshieldproducts.com/header_heat_wrap.php

Header wrap is getting a bad "wrap". Header exhaust heat wraps are not the reason pipes fail from heat. It is really more an issue of alloy quality used by the manufacturer of the header or exhaust system. The only thing a header wrap might do, is prematurely expose any flaws in a low grade alloy. DC sports manufactures a header for the Dodge Neon that they actually sell exhaust wrap with. If header wrap was so bad, why would a header manufacturer sell it with their header?

Ceramic coatings DO NOT reduce as much heat as a header insulating wrap does, period. In fact we have ceramic coating people become header wrap customers, as they discovered it did not reduce the amount of heat they desired. Instead they applied a header wrap over the top of their ceramic coating to get the right amount of heat reduction.

Header wrap reality: If you want to retain the most heat in your exhaust system, reduce the most amount of radiant heat damage, keep your turbo spooled up, use header wrap to achieve this. If you don't, you need your exhaust to look pretty and do not want the most performance or heat retention, use a coating instead.

the reason NASCAR teams do use header wrap, because there is a ban header wrap. The ban is in place not because header wrap causes premature failures, but because NASCAR does not allow a complete encapsulating wrap around the exhaust. They will allow partially covering blankets.

Basically if wrapping headers and exhaust pipes caused them to fail, we wouldn’t be in business. In fact since 1985 we have NEVER had a complaint about our header wrap causing a blown header gasket, cracked or fatigued any header or exhaust system. It is time for the haters to take their rhetoric and move on, for those of you interested in our header wrap products see the links below.

 

[MK3.0dudeman]

I've heard good and bad about this and I really want to know about it.Thats whay I'm happy this thread got started.I plan on runing a turbo blanket,wraping my stock manifold,but I don't know what to do with my down pipe.I want to run wrap on it but I spent big money on it and I don't want anything to go wrong on it.I was thinking of painting it with thick coats and than wraping it to slow down the rusting prosas.But I'm not sure if I want to risk it.

 

[MK3.0dudeman]

how about this?
http://www.suprasport.com/Thermo-Tec-Header-Manifold-Blanket_p_87-1196.html
any imput on this?

 

[MA70_Powa]

Interesting... I just got my dump pipe thermal wrapped from the back of the turbo until it goes under the car as my underhood temps were pretty intense. I've also got a turbo beanie on the way.

It'd be interesting to get some expert's input as I dont really want my DP to rust....how long would it last (its stainless steel)?

 

[Ma70.Ent]

Looks like I'm not the only one who's interested in finding out how useful this is (and how "not damaging" it is).

 

[MK3.0dudeman]

I need to know a.s.a.p. cause I just picked up your brothers down pipe and I don't want to fuck it up

 

[NashMan]

most cracks happen from shitty welding

i still deabting about wraping my ebay manafold cause fi ti crack i have to rip it all off to weld it

i like the heat wrap that comes wiht spray sealer dei makes it pretty good stuff

http://www.designengineering.com/products.asp?m=sp&pid=55

 

[adampecush]

I don't pretend to be smart(no one would believe me anyway) but as I recall thermal wrap causes premature rust due to the trapped heat, not moisture. Remember that rust is oxidation and adding heat to an oxidation reaction will accelerate that reaction. By preventing the heat from radiating out of the exhaust you cause the temperature of parts like the manifold to increase tremendously which dramatically decreases the life of the part.

No.

"rusting" occurs due to an oxidation reaction involving water and salt, where a porous scale allows for continued attack of the exposed metal. High temperatures pretty much do away with all moisture, resulting in no rust. High temperature scale on the other hand will occur when a steel component is hot for prolonged periods; however, this is a generally non-porous oxide, and will protect the underlying metal (acting much like the oxide on the surface of stainless steel or aluminum).

The main negative effect of high temperature exposure is creep (time dependent deformation due to high temperature exposure and applied stress), but the exhaust temperatures and the stress due to the weight of the turbo aren't really enough to cause a creep failure in the lifetime of a typical engine.

I could go further, but I'm boring myself, and will probably be boring everybody who's reading this...so I'll stop.

manifold wrap = fine. if your manifold fails due to corrosion, under any circumstances, somebody has royally fucked up, and not having heat wrap probably wouldn't have saved it anyway.

 

[Ma70.Ent]

No.

"rusting" occurs due to an oxidation reaction involving water and salt, where a porous scale allows for continued attack of the exposed metal. High temperatures pretty much do away with all moisture, resulting in no rust. High temperature scale on the other hand will occur when a steel component is hot for prolonged periods; however, this is a generally non-porous oxide, and will protect the underlying metal (acting much like the oxide on the surface of stainless steel or aluminum).

The main negative effect of high temperature exposure is creep (time dependent deformation due to high temperature exposure and applied stress), but the exhaust temperatures and the stress due to the weight of the turbo aren't really enough to cause a creep failure in the lifetime of a typical engine.

I could go further, but I'm boring myself, and will probably be boring everybody who's reading this...so I'll stop.

manifold wrap = fine. if your manifold fails due to corrosion, under any circumstances, somebody has royally fucked up, and not having heat wrap probably wouldn't have saved it anyway.

Keep going further whenever you're free, haha. We'd like to be more informed in this thread, or at least I would..

 

[Ma70.Ent]

A post I read on another forum in case anyone still is interested.

(disclaimer: I work for Applied Plastic Coatings, a company which applyies performance coatings, including exhaust.)

The problem with wraps is three fold: moisture, air, uneaven tempratures.
Some of the earlier posters noted that with wraps that moisture could lead to rust, which while certianly true is not the main reason I would be concerned with moisture. The wraps do not provide an uninterupted covering of the header which can lead to air and water geting under the wraps paticulary at the ends and joints of the wrap and air is trapped under the wrap when the wrap is put on. firther becouse the wrap will eithe be overlapped or abuted to the previous pass you will get uneaven tempratures which cause uneaven expansion of the pipe leading to metal fatuige. this problem is only made worse by the presence of air and moisture, which will expand when exposed to heat.

Bottom line, when it comes to header wraps: don't.

 

[Kckazdude]

Wrapped mine from the elbow down. The pipe is thick enough that I wont worry about rust for a very long time. By the time I have a rust issue I am sure I will have another DP.

 

[adampecush]

A post I read on another forum in case anyone still is interested:
The wraps do not provide an uninterupted covering of the header which can lead to air and water geting under the wraps paticulary at the ends and joints of the wrap and air is trapped under the wrap when the wrap is put on. firther becouse the wrap will eithe be overlapped or abuted to the previous pass you will get uneaven tempratures which cause uneaven expansion of the pipe leading to metal fatuige. this problem is only made worse by the presence of air and moisture, which will expand when exposed to heat.

sorry, but the 10-15 degree difference resulting from the uneven wrapping is not going to do a damn thing. There's a pretty big temperature difference between the mid point of the runners and the flange attached to the head, and you don't see manifolds spontaneously cracking apart there. His understanding of thermal fatigue is somewhat lacking.

By the way, what happens to moisture at 500C? Sure as shit it won't be sticking around for long.

With that said, I challenge somebody to show me a properly constructed manifold that has failed by thermal fatigue due to wrapping, and I may re-think my opinion. Until then, I say heat wrap away.