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Old 11-24-2020, 12:14 PM   #1
knesek
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Default Heat wrap downpipe in snow

Hi again,
With my new downpipe, I wanted to make sure that my stock intercooler doesn't get bad heatsoak. I'm going to upgrade to a grimspeed heatshield with the coating and gold stuff, but I'm also looking into wrapping the downpipe. I will be upgrading the intercooler during the summer, but as it gets in the -s relatively commonly here I feel like I'm fine for the winter.

I've been researching it a lot and heard a lot of conflicting information. I've heard a lot of better stuff about the DEI wrap, which is what I would go with. So, my questions are:

1. Is it ok to wrap the downpipe in a very snowy area? I assume that snow would get stuck and melt on it.

2. If I do wrap it, should I only wrap to the bend, or do the whole downpipe?

Thanks!
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Last edited by knesek; 11-24-2020 at 01:54 PM.
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Old 11-24-2020, 02:29 PM   #2
kingsalami
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No downside to wrapping your DP and driving in the rain or snow. I've had a wrapped Cobb DP on my '09 WRX for over 100K miles with no issues. Any moisture will simply burn off after driving a few minutes.

I've got mine wrapped all the way down to the cat, but I don't think it makes that much difference.
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Old 11-24-2020, 02:44 PM   #3
obiling
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This is one of those topics that everyone has their own opinion on but at the end of the day there's one thing you should keep it mind. All exhaust manufactures will void the warranty if you wrap their product.

Yes, in many cases the benefits are greater than all else, for instance; "I wrapped my exhaust because it was heating my brakes lines", or "I wrapped my exhaust because all my wires were melting"

But for a DD? Does it really warrant it? If that doesn't tell you enough then here's a post from someone who took the time to explain it back in 2003.

Long story short, wrapping the exhaust will cause the rate of corrosion to increase but it very well could be slow enough that it takes 5+years to actually fail.

As for your question 1, Yes but it will accelerate corrosion. 2, wrap the whole thing (except the cat, if it has one that is)

"There are several factors that affect corrosion. One of the biggest is O2. Heat is another one. What protects most metals including stainless steel is a really nice oxide layer. The rust stuff is Iron Oxide. It too is a protective layer. As a matter of fact the building I work in designed by the Japanese, uses a protective Iron Oxide layer. Russian Naval vessels have red decks... they let it rust and then seal it which provides life long protection and no need for paint saving money. In the US Navy we strip and paint.... ad infinitum.

Okay, so back to the downpipe and this O2 stuff. Water has lots of O2 in it. You get the water in close contact with metal. You heat it up and boil away the water into steam. The steam, temperature and now dry oxide layer flake off. 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.... ad infinitum. Eventually you get a badly corroded and defective pipe.

1) Most exhaust systems are composed of fairly thin walled tubing. 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? etc....

2) A turbine housing can take a wrap more readily because it is a much thicker piece of cast iron. It would take a really long time to corrode through one, but they do corrode. Almost all of them are quite rusty.

3) Ceramic coatings provide a protective barrier of their own and do a lot to reduce temperatures as they are lousy conductors of heat. 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. The ceramic coating once flaked off leaves bare metal that will rust in a wet / dry / rewetted atmosphere. 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 100 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."




Last edited by obiling; 11-24-2020 at 06:19 PM.
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Old 11-25-2020, 09:35 AM   #4
kingsalami
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Quote:
Originally Posted by obiling View Post
All exhaust manufactures will void the warranty if you wrap their product.

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."
[/b]
You've got a lot of accurate info in your reply. But be careful throwing out blanket statements from a post 17 years ago. From researching just a few minutes, neither Cobb, Tomei, nor Killer B void their warranties from using heat wrap. I'm assuming this is because they use higher-quality SS for their products.
I know Perrin voids their header warranty if you heat wrap, but I've never considered their headers to be high-quality from the manufacturing defects I've seen over the years.

You are correct in stating that wrapping will accelerate corrosion on mild steel components, but I don't know of any reputable manufacturer that produces mild steel headers or downpipes for our cars. It's because mild steel should never be used in this application due to mild steel corroding almost immediately on contact with moisture.

And you are also correct in pointing out that the rate of corrosion on these components will be much higher in the NE and NW than drier, milder states in the SW like AZ or OK.

It is up to the individual, but I can show you what my wrapped Cobb downpipe and GT Spec headers look like after 10+ years and 120K+ miles on the car - no significant corrosion.
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Old 11-25-2020, 11:20 AM   #5
obiling
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Quote:
Originally Posted by kingsalami View Post
You've got a lot of accurate info in your reply. But be careful throwing out blanket statements...
I appreciate you taking the time to tell me what I just said is in fact true lol also you should've taken the extra minute while researching to maybe reach out to the companies.

I spoke to Cobb through their webchat, warranty is void if you wrap; I called Killerb, the nice lady on the phone told me warranty is void if you wrap. I couldn't find a number for Tomei but I can say with certainty that cobb and killerb void the warranty so your the one throwing out false claims.

Here you are trying to make sure I don't spread misinformation but you actually did the opposite and now you're the one making false claims from your "research" Cobb & Killerb WILL void the warranty go call them.
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Old 11-25-2020, 07:05 PM   #6
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The hottest and closest thing to your intercooler is your turbo. Why are you not wrapping it?

Read the above twice slowly. Then go https://forums.nasioc.com/forums/sho....php?t=2298336 and read how to do it cheap and easy and marvel at the creator of that post and his brilliance.
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Old 11-25-2020, 07:28 PM   #7
Jack
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Quote:
Originally Posted by Unabomber View Post
........and marvel at the creator of that post and his brilliance.
Both chuckle inducing.....and true. No...really.
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Old 01-04-2021, 09:29 PM   #8
lc_wrx
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Do you think the heat wrap matters from what brand you buy it from? I was considering wrapping headers but not sure if tape brand differs throughout big companies
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Old 01-04-2021, 09:47 PM   #9
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Quote:
Originally Posted by lc_wrx View Post
Do you think the heat wrap matters from what brand you buy it from? I was considering wrapping headers but not sure if tape brand differs throughout big companies
You should most def not wrap your header. It will do bad bad things to the header.

Having said that, I'm of the opinion that most heat wrap is made by one or two companies and rebadged to many. I remember when the cool "titanium" or "lava" wrap came out not too long ago. It legit looks the same whether you get it from DEI (big name in wrap biz) or from the sort by lowest price eBay seller. Am I right? I can't say for sure as I don't KNOW, but I'd bet you $7 and punch in the neck I'm right.

Again...don't wrap your headers.
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Old 01-05-2021, 10:51 PM   #10
Scorpius
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I had a perrin dp on my old 09 wrx. The welds on the cat to tubing rusted. The dp fell apart. I had it wrapped in dei heat wrap. Midwest winters ftw. Don't wrap it.
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