From a discussion going on now (OBX Header thread), I thought this might be a good opportunity to focus on this topic...

I am becoming more and more convinced that header wraps are old news, and actually bad. The best way to address these issues appears to be with these new high-tech coatings; Jet Hot being one of the more popular choices, along with HPC...

Here is just a bit of reading on the pros & cons of wraps vs coatings:

http://www.centuryperformance.com/heatwraps.asp

jlm is running with this on his SuperSprint header:

http://www.hpcoatings.com/hipercoat_extreme.htm

Now while comparing these against wraps seems to be a no-brainer, from a PM recently received, do these coatings come at a cost, besides the price tag (couple hundred bucks)?

Through some research, it was found that such coatings reduce the longevity of motors, and exhausts; and for that reason not all racers use them... And it was shared that this approach is most beneficial in turbo applications. So, for the long-term, this might not be a good thing...

This person then decided (understandably to many of us) to not go this route and to forego the miniscule theoretical performance gain, in trade for longevity.

The longevity of the header seems to be improved by such a coating though... Is then the engine and the exhaust system taxed with such header protection?

With the header probably contributing much to our engine bay temps (especially when not in motion), I had always thought that this was a worthwhile investment, for that reason alone...

Curious to hear what some of you think...

 

Really? I'd like to see that "some research". I've been using ceramic coatings on motorcycle exhausts since I first heard of them more than ten years ago and I've never experienced nor heard of header coatings reducing the longevity of engines. I'll agree that the performance gains are minimal unless you're either running a turbo or running WFO all the time, but in the always hostile world of motorcycle exhausts it's one of the best ways to assure a long-lasting exhaust system.

But shortening the life of an engine? I'd need to see some proof of that, 'cuz my experience in the matter leads me to cry BS.

 

Hey Spunky, thanks for the input. My first thoughts also... He said that he lost the links from his research though...

I can see how maybe the exhaust system would see more heat because of this, and with that, maybe earlier failure of cats, resonators, etc... but for the engine, I'm not sure I see how that would be... That's why I started this inquiry...

 

Tony, thanx for starting this thread. I've been following the obx thread and actualy ordered an obx header from sparktec today. Anyway, I also spoke to hpc, they do an external and internal coating. They claim a temp reduccion under the hood to be anywhere between 35 and 40 degrees. The asking price for the job is $155, the same as the cost of the header. I guess you can see where I'm going here, I could just buy another header instead of having one coated and have obx headers for a long time. Is the coating cost worth it for a steet car? It's not like I drive wot for extended times and then there is the unknown in terms of what may happen to other components as a result of messing with header temps. But if hpc claims are true then the drop in temps under the hood may be a good thing for our little motors in the hot summer months. Where are the experts here?

 

Good subject Tony. I've been holding onto a bunch of header wraps from my CRX days (forgot to put them on when I got the Miltek ) but will be putting them on when I can afford the AEM broadband A/F meter Can't afford no ceramic stuff or my wifes gonna show me the porcilin potty

 

Dropping underhood temps is very nice, especially for our top-mount, heat-soaked ICs... I personally find the price quite reasonable. Logic tells me that if it's removing that much heat, it's going somewhere else... namely down and out. If that's it, that's great! However, there seems to be some concern about throwing more EGT's at our cats and remaining catback system...

We've already heard about stock and aftermkt cats and resonators getting shot, so more heat coming through is bound to make for more failures. Seems logical... I have a SuperSprint resonator about a foot beyond the cat. I would like to think it would be fine. I believe PROMINI's SilverSonic (Turbo'd MCS) utilizes this same SS resonator center pipe, so maybe it can take the heat just fine...

I guess my biggest concern is the possible negatives for the engine. I would tend to think that a coated header is going to move expended air faster, and take it (and its heat) away from the engine faster, that being a good thing. I have limited knowledge on such stuff though...

minibrute, keep us posted on the header, coating, driving impresssions, and dyno, if you plan on such...

 

MSFITOY, have you chatted with Peter about a wideband he found? He showed it to me sometime ago, and it's really good, and quite reasonable in price. Heck, even the gauge matches the MINI's motif .

Sure you want to do wraps after reading that first link I provided?

 

What sort of engine damage are we talking about? Only thing I can think of is heat migrating up the exhaust ports but the Cooper S already has inconel exhaust valves...

Also, if you're going to have your exhaust coated and you want it done with the shiny stuff (polished or chrome look) you can usually have the inside done in black for a small masking charge. There is a pretty decent difference in temp that the metallic finishes can handle compared to the satins (about 700 degrees I think). The metallics have aluminum in them and if they get too hot, they'll turn dull and you've wasted your money. Doesnt matter on most parts, but exhaust manifolds/headers are usually worth the small upcharge.


--
Cheese

 

I can see I'm going to have to find the reference that I'm hanging my anti-wraps/coating "hat" on.

Does anyone have a copy of Corky Bell's "Turbocharging"? I've left mine in long term storage back in USA while I'm here in Italy, and can't get to it. Its been a good 2 years since I read it, and I'm about 50/50 sure, this is where I read about potentially harmful effects of keeping too much heat in the header/exhaust for a non-turbo or normally aspirated application (granted, Mini is not N/A). Wonder if someone wouldn't mind reviewing Corky's theory on wraps &/or coatings from this reference and summarize for us?

I'll also endeavor to locate the reference. I swear I've read about this somewhere credible, and will post for everyone's review & opinions.

 

My experience with header wraps was not altogether a good one. Sure, it reduces heat in the engine bay, but if your header is made of mild steel and/or not coated, the header wrap will make the header rust like heck.

The wrap traps moisture against the header and keeps it there, a virtual playground for rust to form.

So, if you use header wrap and your header is not stainless steel or protected with a good coating of some kind (i.e., ceramic, "Jet-Hot", etc.), beware of rust!

 

why not just coat the INSIDE of the header? (ok,ok, you'd like to have a little bigger tube to make up for the coating thickness....)

 

these guys like 321 stainless( for its lesser ability to precipitate carbides) and stainless in general because "Typical carbon steel conducts 219% more heat per foot than do the types of stainless that we use. By contrast, quite a bit more heat stays inside the stainless header tube and does not get passed to the surrounding air. By not allowing the contraction of of the cooling gasses as they flow down the tubes, more exhaust velocity is retained which promoites better scavenging in the collector." from the Burns Stainless catalog.


also:
www.burnsstainless.com

 

Ah...I guess not. I didn't actually read it until now Yes, Peter mentioned that he is a dealer for these wide-band meters. It's definitely a part of my WANT list...

 

Tony,

I know there was a comment above about coating both inside and out. But what about that idea? Why not? I would think that coating the outside would help underhood temps, while coating the inside would enhance exaust gas velocity. The latter potential helping to remove heat otherwise absorbed by the exposed inner stainless surface??? Am I making any sense?

 

Indeed you are (making sense)! In the OBX header thread I reference internal and external coating, and totally agree. Just trying to find-out if there are any legitmate reasons not to coat...Let's see what BluMiniMe can find

 

Sorry Tony! I get so excited I pass right by the important stuff - a technical term.

Ciao

 

I'm not Tony, nor do I play him on TV, but I've got some experience with exhaust coatings. Normally you coat both the inside and the outside at the same time. I can't really imagine why anybody'd just coat the inside or just the outside. The purpose of the coating is to keep the heat in the exhaust rather than radiating it out through the tubing. A side benefit of coating is that it'll keep the pipes from rusting out because water can't get to it because it's, get ready for this, coated. Keeping the heat in the exhaust gases allows them to be evacuated more efficiently.

The main reason that wraps pretty much suck is that while they do keep more heat inside the pipes than the naked uncoated pipes will is that the wraps are porous, which means that they'll hold moisture and in doing so will cause the pipes to rust faster than leaving them naked will.

In either case, unless you're running a turbo or running WFO all the time, you'll never feel a difference in power whether or not you wrap, coat, or leave the pipes naked. It's just not that big a difference in the real world. If you're building a ten/tenths racer, maybe under just the right conditions you'll see some difference, but not much. It will noticably reduce underhood temps, though, so on that level or on an aesthetic level it might be worth doing.

I've got Harley exhausts that I've had coated mostly for aesthetic reasons that are out running around on the street and looking good long after their chromed brethren would have blued, bubbled, and rusted through. But I'm not kidding myself that it's some sort of horsepower secret, 'cuz it's not.

 

I had a Caterham Super Seven with all aluminum body so the underhood temperatures were transferred to the footwell. Jet Hot Coating made a big difference. There are two temperature ranges available from Jet Hot and I had purchased the lower one. It was insufficient to handle the heat and there was some adverse reaction, it's been a few years and I don't recall what, exactly. Jet Hot re-coated them with the higher temperature coating for only the difference between the price of the two coatings, I was impressed that they stood behind their product. I think that they guarantee it for life. There is a slight increase of O.D and decrease of I.D. so some slip connections are a little more difficult to make.

 

LeftyS7, thanks for the input!

Hey, I have to ask.... "had"? Why would you part with a 7? I'm planning on getting a kit in the not so distant future...

Was your experience with the venerable Crossflow, or the newer Zetec or Duratec powerplants?

Thanks for confirming what I thought about ID and OD's also!

 

I went back and forth with Jethot regarding a part I had jethot coated a few years back. They kept claiming it was going out "next week" but what really happened is they lost my part. Took them a few months to finally find it tucked away on a shelf somewhere.