The little flakes leave bare exposed metal mostly Fe even for stainless steel which just has some chromium in the steel mix. You get a new protective iron oxide layer. Oh but then you rewet it with some moisture and soften the layer. Boil away, flake off Eventually you get a badly corroded and defective pipe. If you wrap it you will get accelerated corrosion due to the wetting, evaporating and rewetting cycle. You are forcing it to happen at a greater rate by putting a water absorbant next to the piping.
There is a huge reason why the Navy spends big man hours searching for wetted lagging in their steam plants every year.
Wrapping a downpipe is going to cause this problem. Where you live will contribute to the rate of corrosion. How much humidity is there? How often does it rain? Fresh water or close to salt water Cl has a very significant effect on corrosion?
Do they salt the roads? It would take a really long time to corrode through one, but they do corrode. Almost all of them are quite rusty. Ceramics introduce their own problems particularly internal to headers and turbine housings. Ceramics are brittle. The metal expands when heated, and the ceramic coating doesn't expand as much or at the same rate.
The ceramic coating eventually will start to flake off in little chunks. I've heard reports of the flakes damaging turbine blades.
I've also seen many rusty ceramic coated headers. One little spot of rust will grow to a bigger spot as the wetness seeps under the ceramic coating.
So what can you do? You really have to think about where you live and what sort of conditions you car will see. If you live in a really dry area and the insulation will stay dry most of the time, than your problem is minimized.
If you live in Western WA state like I do and you wrap your downpipe and it happens to be a mild steel downpipe, it won't live long. If you live where they salt the roads, drive in the winter and wrap a mild steel downpipe, it might not last one winter. Get a bunch of wet salty water in your downpipe wrap and kiss it goodbye. If your downpipe is thicker walled stainless steel than it will live longer. Too many variables really. Consider your own situation and conditions.
Stainless steel can corrode for certain. That's why you never clean a stainless steel sink with a rough abrasive. You will destroy the oxide coating exposing the bare metal. Wanna see your stainless steel sink rust away? Get some hot salt water, and scrub the crud out of it using grit sandpaper everyday for a month.
By the end of the month, you'll need a new sink. So consider your conditions of O2, Temperature, and Cl and make your own choice. Those are the 3 largest contributors to normal forms of corrosion. This doesn't include most cracking corrosions. Even more fun Solve it for T2. If P2 is lower than P1, T2 is lower than T1.
No surprise. Ever open the valve of a pressurized air tank and watch the valve get cold? This does NOT mean that the turbo "derives a very large portion of its energy from heat. The rotational energy transferred to the turbine comes entirely from the kinetic energy of the fluid in this case, gas striking the vanes.
It is true that the hotter the gas is in the volume of the manifold, the higher will be the gas pressure, and therefore the higher the energy delivered to the vanes, but heat temperature is NOT what is turning the turbine. David, "Wow and several books I read including corky's maximum boost specifically identify the combination of flow and heat as the reason for the power. Cooling of that gas BEFORE the turbine input reduces its pressure and therefore the kinetic energy of the gas striking the vanes.
That's why a turbo at the end of the exhaust pipe would be bad; because of the loss of heat through the pipe causing loss in PRESSURE at the turbine input. Regarding "Hey, no need for an intercooler," now you are writing about the compressor side of the turbo, not the turbine end. Even if you ran the turbine with high-pressure cold water which would theoretically work just fine , the exit air from the compressor section would still be heated same old ideal gas law.
So you would still want to cool the compressed air, to reduce the back pressure on the compressor and increase the density of the input air. Also as Corky has pointed out in other literature, the engine is stressed less if input air is cooler. OK this has wandered off-topic somewhat but From this it seems intuitive that if the exhaust has more energy ie more heat for the same pressure then there is more energy that can be 'recovererd' by the turbine. This ties in with the example of a turbodiesel ie no difference in throttled airflow spooling up when you press the accelerator - the exhaust is hotter from the added fuel burning.
To answer the original question - retaining heat in the exhaust means more recoveerable energy for the turbo! This has been interesting. Thanks for staying civilised everyone : pointy-head Jeff. I have my downpipe wrapped, and so far I am pleased with the results. My heater hoses and brake lines are no longer suffering from the heat of the pipe. It has only been wrapped for about 7 months and everything is looking good so far. I'll give an update if I notice anything. Chris B. Well for me the proof's in the pudding, and I'm not believing the rust stuff til I see it.
Wow, this thread went longer than I thought. There have been a lot of posts confirming my original post about heat energy, blah blah and a few contridicting sp it. In the end it seems people have come to the consensus that heatwrap or ceramic coating, or heatshielding would be good for a little help in spoolup and some ponies Well, like I said, I've run mine wrapped for a long time my current eclipse has been wrapped for over a year, 20K mi or so and there is no 'excessive' rust.
There is surface rust but no more than what I'd consider normal for an unwrapped exhaust. Lance Schall, this has been my beef with tubular stainless steel manifolds for a long time. The results, 6,mi later the manifold cracked to the point of being unfixable. I returned to a cast manifold and have had no problems, wrapped or unwrapped. These types of manifolds are designed to extract the last bit of HP and are perfect for a track car that needs that Basicly, if it's a proper mainifold designed to be run on the street wrapping it will help.
I have mine heat wrapped and like crispy, I am more pleased with the fact that my brake lines are no longer scorching and heater hoses about to fall apart after some roadracing.
The idea of heat providing recoverable energy is something that I would have to agree with but I can't figure out how to prove it other than back to back dyno runs but who wants to pull a DP off at the dyno? My underhood temps have decreased as well which gives me a better ambient intake temp. The benefits of having the wrap on there has easily justified it's existence for me.
And all you thermo guys need to stop pulling variables out of equations. Thermodynamics relies on "before" and "after" to tell you how much power the turbo converts to mechanical energy, not T1 or T2 or P1 or P2 individually. I'm pretty sure turbochargers are not isothermal devices. Pressure is heat, heat is pressure. His second sentence is not correct as stated obviously.
How about "Heat makes pressure" instead? Since a given volume of gas will rise to a higher pressure if heated, a hotter cylinderful of exhaust gas will result in a higher gas pressure at the turbo input, increasing the pressure differential across the vanes, producing more power. Again, a given pressure differential from input to output of the turbo will result in a certain amount of power generated by the turbo.
Makes no difference if the turbo is hot, cold, or in between. The internal combustion engine works the same way. Y8s, "And all you thermo guys need to stop pulling variables out of equations. Pretty sure P,V, and T cover it, at least for an ideal gas, according to Mr. Boyle and Mr. You can [help] prevent this by getting them coated before wrapping.
If the pipe is made of non quality steel I could see it going through eventually but would take years. Originally Posted by catcher All times are GMT The time now is PM. User Name. Mark Forums Read. Thread Tools. Wrapping downpipe worth it? Appreciate 0 Tweet. Find More Posts by evoxi. Find More Posts by hetzle. Quote: Originally Posted by evoxi DEI has a titanium wrap that reduces resonance from the pipe and even drone. Quote: Originally Posted by evoxi Any possibility at all to have it wrapped while on a lift or does it need to be removed and wrapped.
Quote: Originally Posted by evoxi I've googled and read about pros and cons with wrapping you downpipe s but I'm looking for i specific. Find More Posts by Shogun Originally Posted by MolonLabe Originally Posted by Chiromikey. The metal is forced to retain more heat than it can handle and it disintegrates as if it had been rusting for decades.
The parts just crumbled away as the wrap was removed. May wrap them as well So glad this popped up again. I ended up wrapping the top parts of the pipe right off of the turbos. But for the short time I didn't have them wrapped you can see that the piping off of the turbos melted the heat shielding.
Holy hell!! I had to take some of the bay apart again to wrap the top portions for now and seems to be good. I'll wrap the bottom half soon here but damn. Wrap your pipes people, it's hot in that bay!
And no, nothing was touching and had plenty of space so I'm not sure how this happened and I haven't seen anyone else with this issue that didn't wrap them. Last edited by The Infiltrator; at PM. Originally Posted by Audibot. I kinda dought just coating the hot side of turbos would give you that much benefit over the hassle.
Wrapping them with tape isn't realy an option Maybe one day i explore a more heat extraction way to keep the bay cooler.
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