Trubo manifold heat

[drifter17a]

Does exhaust manifold get hot as turno exhuast side? I have a turbo cover to managr heat in the engine bay but  nothing is covering the exhaust manifold before turbo

 

i know as turbo does compress air, the temp does go up however does that mean exhaust manifold would be as hot?

[GTSBoy]

The exhaust gases are at their highest temperature as they leave the exhaust port and enter the manifold. They cool as they flow through the manifold because they transfer heat to the manifold and the manifold loses heat to the surrounding environment.

Thus, inevitably, the exhaust gases are cooler as they enter the turbo compared to when they entered the exhaust manifold.

So, yes, the exhaust manifold can easily get as hot as the turbine housing.

Having said that, you will generally see the highest temperatures where the exhaust gases have to slow down or they are concentrated into one area - which is usually the collector on the manifold and in the turbine housing, because the gases slam into the metal at those places, increasing the convective heat transfer coefficient and transferring even more heat to the metal than they might just flowing past elsewhere.

Exhaust manifold heat shields are a good idea - certainly for the stock manifold they are there from the factory. People seldom have anything like that on a tubular manifold because they are hard to achieve. Some might wrap a tube manifold with fibreglass tape - but this has a reputation of leading to cracked welds. The best case is generally to put ceramic coating onto the manifold to prevent it getting as hot (internal coating) and radiating/convecting heat into the bay (external coating).

All the real heat from a turbo comes from the exhaust side. The gases entering are at ~800-900°C and the steel/iron gets nearly that hot. The compressor side is only going to heat the charge air up to <<200°C (typically not much more than 100°C). So that's nothing, by comparison. The compressor is not a significant source of engine bay heat.

[joshuaho96]

1 hour ago, GTSBoy said:

The exhaust gases are at their highest temperature as they leave the exhaust port and enter the manifold. They cool as they flow through the manifold because they transfer heat to the manifold and the manifold loses heat to the surrounding environment.

Thus, inevitably, the exhaust gases are cooler as they enter the turbo compared to when they entered the exhaust manifold.

So, yes, the exhaust manifold can easily get as hot as the turbine housing.

Having said that, you will generally see the highest temperatures where the exhaust gases have to slow down or they are concentrated into one area - which is usually the collector on the manifold and in the turbine housing, because the gases slam into the metal at those places, increasing the convective heat transfer coefficient and transferring even more heat to the metal than they might just flowing past elsewhere.

Exhaust manifold heat shields are a good idea - certainly for the stock manifold they are there from the factory. People seldom have anything like that on a tubular manifold because they are hard to achieve. Some might wrap a tube manifold with fibreglass tape - but this has a reputation of leading to cracked welds. The best case is generally to put ceramic coating onto the manifold to prevent it getting as hot (internal coating) and radiating/convecting heat into the bay (external coating).

All the real heat from a turbo comes from the exhaust side. The gases entering are at ~800-900°C and the steel/iron gets nearly that hot. The compressor side is only going to heat the charge air up to <<200°C (typically not much more than 100°C). So that's nothing, by comparison. The compressor is not a significant source of engine bay heat.

I've seen some stuff like this as well, not sure if it's a good idea or anything but it does have more standoff from the piping than the conventional fiberglass wrap:

 

[GTSBoy]

Yeah the ACL and similar formable heat shielding materials are really nice. But most people do not have the patience or talent to do a good job like that.

Almost anything is better than nothing though. Even if you didn't form it closely like that and just had a slab of it slipped in between the manifold and somewhere/thing you wanted to protect, you would gain benefit.

There has to be a market opportunity for people like Artec to make formed heatshields to suit their cast manifolds. The fact that they are cast means that they are consistently the exact same dimensions and they could add bosses to the castings like you see on stockers to allow heat shields to be firmly attached yet floating away from the manifold itself.

[drifter17a]

I have a 6 boost manifold and it has loads of bends etc. turbo has a cover however manifold doesn’t so I started to wrap what I could without taking turbo off. Very restricted area

 

are you stating wrapping could lead to cracking weld? Is that because heat is retained? 
 

i have a exhaust gas temp right after turbo and it hits 700degree or 800 at times.

 

there are areas which is impossible to reach with fibre glass cloth. Is there anything I could apply such as the photo shared earlier which would formulate around exhaust pipe in difficult to reach areas, sort of like aluminium foil flexible to shape it in place?

 

i think from earlier reply you mentioned acl? Is this what you meant?

 

https://www.nstparts.com/product/acl-heat-shield-700x275

 

 

photo of my engine bay

 

https://ibb.co/9grHsMN
https://ibb.co/bXC8KRM
https://ibb.co/KV3kGZc

 

I am trying to cover bottom of the exhaust manifold which joins the turbo. Only way is to take turbo and possible manifold out as it also touches the engine mount which I don’t fancy doing

Edited December 5, 2024 by drifter17a

[GTSBoy]

47 minutes ago, drifter17a said:

are you stating wrapping could lead to cracking weld? Is that because heat is retained? 

yes

48 minutes ago, drifter17a said:

Is there anything I could apply such as the photo shared earlier which would formulate around exhaust pipe in difficult to reach areas, sort of like aluminium foil flexible to shape it in place?

yes

this

48 minutes ago, drifter17a said:

https://www.nstparts.com/product/acl-heat-shield-700x275

 

48 minutes ago, drifter17a said:

i think from earlier reply you mentioned acl? Is this what you meant?

yes

 

[drifter17a]

Thanks GTSBoy, appreciated