360 Which is better - header blankets or inconel heatshield?

Inconel is the way to go. Blankets have a tendency to fray apart and degenerate over time-- plus they look sloppy to me in an engine compartment so beautiful as the 360's is. There a a few threads you can check out. Plus I'm pretty sure Inconel heat insulation is far better at heat dissipation. Note though, while they picture the headers with no air rails this is what the dealer was told in an email when I inquired about the headers:

"The headers do come with the air rails and Larini does not suggest them without. So after a long discussion just now with Larini, it seems that the manifolds listed do not have the air rails. They can make them with the air rails but the price is a bit higher as reflected in this quote. Not sure why they list them without but advise having the air rails. It must be a British thing "

In a few weeks I'll be ordering the Larini 200 cell cats and the headers for a 360. Price and quality look unbeatable.

 

I'm planning to do an insulation and shielding sandwich over my Kline cats and muffler. I'm a bit skeptical of the effectiveness of metal only shielding that is in constant contact with the heat source, even though there air pockets in the dimples. It's better than nothing, but curious how it stacks up to insulated shielding and with shields that aren't physically connected to the heat source.

I went with OEM '99 headers, so no AIR rails plus it has the factory insulation and shielding. They can be had fairly cheap though I went with new. They're also a 4-2-1 header so the sound is a little different.

 

INCONEL all day everyday


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The shielding is not in contact all over the place with the headers; there is an air pocket. The only think in constant contact with the header is the little round nipples which also get very hot (tested by mistake doh) when running; I think they are spot welded or something to the header. The rest of the metal sheet can be touched, not those though..

 

I don't have data to back up the following, so take my opinion with a pinch of salt.

I think that proper (like Capristo) blankets reduce under bonnet temperatures more than something like Inconel thin wall shields, but the thin shields offer a better weight/performance benefit hence why race cars use it. I think the metal shields do a sufficient job without the excess weight penalty, but the blankets offer more for a much larger weight penalty.

Much like sound deadening material, or cubic inches (engine capacity) - there's no replacement for more of it.

I can put my hands on my Capristo blanket equipped 430 Scuderia cats after a good drive, but there isn't a chance that I'd try it with a metal shield.

 

Would be nice if we had some data for headers with and without the inconel shielding and also for the blankets. Would also love to see a comparison between either of those and the stock headers. Ultimately, as long as either is better than stock, you're doing good.

 

https://www.ferrarichat.com/forum/threads/inconel-wrapped-headers-manifolds.651026/

 

That link didn't work for me for some reason but it does if you copy and paste it into the search bar

 

Thanks for that. You're right. I tried clicking the link and it didn't go directly to the post.

 

wow, that's impressive - you could easily cook an egg on my scud engine cover after a spirited drive - the engine bay temps seem mad to me
think I'll have to look at headers,cats, heat-shields in the near future

 

Has anyone an opinion of the heat dissipation issues? Seems to me, and I'm just spitballing here, that one would want a certain degree (no pun intended) of heat to be dissipated away from the headers and by extension, the engine itself. I understand the header blankets being "cool to the touch" after running through the gears, but... I'm wondering... does not the majority of the heat generated stay mostly confined to the headers and engine heads then?
It seems like the Inconel shielding is a way to mediate the heat exchange. Some of the heat is absorbed and dissipated while a percentage of it is, as in any case, absorbed by the headers themselves and the engine heads/engine. Seems like there's a happy medium to shoot for.

Any engine gurus out there with more than an educated guess?

 

I feel like this is one of those things that has 100 different answers that are all correct and wrong at the same time. I was under some impression that too much heat in the cat is bad for its longevity. On the other hand, higher exhaust temps cause faster flow of the air out the back which is good? Also, higher heat can cause more thermal expansion on joints and welds causing premature failure, but too too much temp in our engine bay causes other things to fail. I feel like there's not really a good answer here aside from not doing anything is bad.

 

The exhaust gas massflow has to be equal to to the intake massflow and the fuel mass flow. (What goes in, must come out. Otherwise the engine would get heavier and heavier over time). The temperature of the exhaust system is not a major factor in this. It is true however that hotter temperatures can correspond to higher massflow - in the case that you are burning more air-fuel mixture in your engine (i.e. more engine power). In terms of durability this is not an advantage.

The failures in the area of welds is typically due to low cycle fatigue - caused by thermal expansion and constricted geometry: the header wants to expand but is bolted down. This leads to stresses in the material. The cycling of temperatures (and thus stresses) will eventually lead to cracks. Higher peak temperatures lead to higher stress amplitudes and thus to earlier failures.

The failures of various components in the periphery is mostly caused by aging of polymer components or solder connections etc. These aging processes are also accelerated by higher temperatures, but the exact failure mechanism strongly depends on the exact design and material of the component, so no chance of making a generally valid assessment there.

So in that sense I fully agree with you: there is no good answer, it will always be a trade-off.

Your safest bet is to assume that Ferrari has found the best overall answer when they designed the car. Keeping the heat directly in the exhaust system to protect various auxilary components in the engine bay doesn't strike me as a particularly good concept. I would suggest that keeping the "insulation" of the exhaust system close to OEM and additionally shielding sensitive components (e.g. ECUs) against heat radiation, conduction and direct convection, is the smarter choice here.

Apologies for the wall of text, maybe it was interesting for someone at least.

 

Generally speaking, the less heat lost from an exhaust system in any place other than the tailpipe the better. Higher temperature equals higher gas flow, which in turn helps with heat transfer away from the cylinder heads.

 

In my opinion, these claims are not harmonizing particularly well with the laws of physics:

The mass flow of the exhaust gas does not really depend on the temperature of the exhaust system. There maybe some small changes in volumetric efficiency due to accoustics (speed of sound changes with fluid temperature) and due to changes in fluid resistance (density and viscosity change with fluid temperature), but those are negligible or will more likely be detrimental in the case of accoustics.

So if you are insulating the exhaust manifold of an NA engine, all you are doing is raising the temperatures in your manifold and thus on your cylinder head (due to heat conduction).

 

I'm not much of a physicist, so correct me if I am wrong, but isn't the volume of flow out of the back of the exhaust somewhat related to gas/air density, which is affected by temperature? If an exhaust is loosing a heat over its length, then won't the density of exhaust gas be reduced by the time it reaches the tailpipes?

 

The density of the gas increases as it cools down, so the volume flow will decrease correspondingly.
Consequently the velocity of the gas will indeed be lower as it cools down, but since the cooler gas is denser, the amount (i.e. mass) of gas that is being transported in a given time period remains unchanged.

 

The exhaust gas is already cooling and losing pressure so rapidly coming out of the head that I think it would be difficult for insulation to cause cooling problems. The factory system is insulated and shielded for effectively the entire length. I think there would be some benefit, however small, from keeping exhaust gas energy as high as possible until it reaches the atmosphere.

 

I have Jet Hot's ceramic coating on mine and am very satisfied. I wish I would've tempt before and after the header replacement, but my "hand in the engine bay" test after a spirited drive tells me temps are lower than stock...it's very noticeable.

 

You can get a Tubi with air rails and insulated heat shields for less than the Larini.


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Check with Scuderiacarparts.com. That’s where I got mine from for ~$5400 shipped.