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WydRyd 11-01-2006 08:29 PM

JET HOT 2000 Coatings?
Fellow turbo junkies, what do you guys think about the JET HOT 2000 header coatings?

Is it worth spending the extra cash on this process to reduce engine bay temps?

I presume the actual spool-up improvement would be minimal, but it may be worthwhile just to have a cooler engine bay and reduce heat soak in our intercoolers?

I've heard from certain tuners that it may accelerate cracking in the joints around the header? Is this more prevalent in track cars, or street cars?

I've also been told NOT to coat the inside of the headers, as the coating could potentially flake off and ruin the turbo's turbine?

What do you guys think? Worth the effort or not?

I've got a set of GSF S.S headers (no heater boxes) which I'm intending to use with a Garrett GT35RBB turbo and free flowing Magnaflow single in/out muffler.

Craig 930 RS 11-01-2006 08:38 PM

Why would you *ever* want to contain heat in headers?
To add more heat to an already taxed turbo?

Skip that stuff -

mb911 11-02-2006 05:44 AM


Originally posted by Craig911
Why would you *ever* want to contain heat in headers?
To add more heat to an already taxed turbo?

Skip that stuff -

Because heat drives the turbo charger not pressure like so many think.. Look at allot of tuners the wrap their headers and wastegates to keep as much heat as possible in there. it does result in faster spool ups and is a proven factor in many dyno runs

mb911 11-02-2006 05:45 AM

oh but to answer the question this is very common on Hi porformance applications but there is some risk that it could flake off

Craig 930 RS 11-02-2006 06:29 AM

Heat driving turbos etc - great in theory and partially true in practice - but really......skip it on our cars. The downsides are numerous.

mb911 11-02-2006 07:08 AM

its not theory it is proven. I will search more I did find one picture but not the best..

mb911 11-02-2006 07:16 AM

here is another not of a porsche but same principle

Craig 930 RS 11-02-2006 07:43 AM

Let's hear some success stories form actual turbocharged Porsche 911 chassis cars - with quantifiable results.......Bueler? Anyone?

Zeroclearance 11-02-2006 07:48 AM

Actually if one coats the headers and turbine housing of the turbocharger you will contain the maximum latent energy available. As a result the rotating assy (turbine wheel) will start spinning sooner-hence lag reduction. Typically with good coatings one can see 200 RPM reductions in lag.

As stated before, NEVER coat the inside of the headers or turbine housings. You will destroy your turbo in a short period of time. Please have this instruction in writing. Many times the coating company fails to heed the verbal instructions....


Craig 930 RS 11-02-2006 08:01 AM

Cool to see Kevin on this board now. He makes THE turbos for our 930s.

Kevin - What is your take on wraps?
Coatings on stainless headers (such as B&B) ......?

A few local guys have horror stories about the coating stuff flaking off. The wraps also hide the inevitable header cracks -

Wonder if it is worth 200 rpms, Kevin would know.

Zeroclearance 11-02-2006 08:22 AM

Wrap are not good in climates like the Pacific NW where we have rain.. Any condition where water will hit and soak the wrap will cause corrosion. Welds will fail. I have seen my share of turbine housings that have been wrapped, and most of the time I just toss the housings into the scrap bin.. However, for a race prepped only car, wraps have done well. Provided that there is no rain.. All in all, ceramic coatings by a well known company, Swain, JetCoat.. are cheaper and if the headers and turbine housings are prepped good, you have good results..

Results are less than favorable if one uses used parts vs new stainless and high nickle turbine housings.. It also doesn't warrant one coating just the headers, and not the turbine housing.. It is the turbine housing that we want the concentration of heated energy.

Another side note... Wrapping turbine housings do cut the life-span out of the turbine side sealing rings.. The heat tends to prolong the heat soak. It is minimalized if one had water cooled bearing housing, but that out of the picture in our application.. Heat radiating into the turbine shaft and bearings from the insulated wrap is NOT good and can suck out 50% of the life of your turbocharger..


Craig 930 RS 11-02-2006 08:26 AM

Excellent. Thanks a ton, Kevin.

mb911 11-02-2006 08:32 AM


Originally posted by Craig911
Excellent. Thanks a ton, Kevin.
You say that like a "told you so" when in reality we were both were answer it correctly just variations.

Don't know what that was all about But The answer was Yes and No flat and simple

Craig 930 RS 11-02-2006 08:35 AM

You have a great internet imagination, mb...

I just appreciate the truth and especially the complete no-bull***** answer from Kevin.

You started with:
"Look at allot of tuners the wrap their headers and wastegates to keep as much heat as possible in there etc"

Kevin simply gave us a well rounded answer, take it for what it is.

mb911 11-02-2006 08:42 AM

No imagination Maybe Just a perception I see from the posts..

I can tell You that the heat energy is what drives the turbo but of course more heat will end its useful life much quicker it still is the driving factor none the less. This is the reason so many want as short of exhaust track as possible to keep the heat in there before it has a chance to dissipate threw the metal. So sometimes these tuners are using wraps etc. I for one am not but the question was can it be done YES it can. Is there potential problems yes just like using aluminum rods in dragsters but benefits.

None the less craig No hard feelings just trying to answer as completly as possible as I do have something to share on the subject.. ;)

Craig 930 RS 11-02-2006 08:46 AM

Right on.
I wanted to clear up misconceptions about "coatings and wrap = good"

When in fact there are varying degees tha Kevin helped us out on.

Peace out!

mb911 11-02-2006 08:47 AM

yup same page !!!!!!!

Jim2 11-02-2006 10:44 AM

I've been around. Never heard this before:


NEVER coat the inside of the headers or turbine housings. You will destroy your turbo in a short period of time
Can you elaborate on this Kevin? What damage occurs in a short period of time? (Flaking, eroded turbine tips...?)


Craig 930 RS 11-02-2006 10:51 AM


Zeroclearance 11-02-2006 10:54 AM

The "coating company" can not etch every nick and cranny inside the header.. Nor can they clean/etch the interior of a turbine housing. You have to have a mechanical bond on every surface. The ceramic coating flakes off and makes contact with the turbine wheel. With a wheel that can turn 140-160K RPM it doesn't take much to incure FOD (foreign object damage) to the turbine blades. The removal of metal from impact will greatly effect the balance of the rotating assy. Accelerated bearing wear will occur.. After this, you get contact between the rotating wheel assy and the housing on both sides of the turbocharger.. And yes, I have seen this happen many times..

cgarr 11-02-2006 11:04 AM

If there is only One thing I have learned here that is, that hot air moves faster than cold air.

Craig 930 RS 11-02-2006 11:13 AM

Especially on Pelican ;-)

mb911 11-02-2006 11:17 AM

I am asking about your rotary muffler? Whats up with that?? Pics??

Craig 930 RS 11-02-2006 11:33 AM


mb911 11-02-2006 11:45 AM

so I am bit slow ha!!!!!!!!!!!!!! :D

Craig 930 RS 11-02-2006 11:56 AM

Nah, I just gave it a weird name for fun -

mb911 11-02-2006 12:01 PM

I guess then I have one as well

WydRyd 11-02-2006 02:05 PM

WOW, I'm gone for a few hours and look what I've stired up :D :cool:

ANYWAY, so the general consensus is that, YES, header coatings are worth it and NO, don't coat the inside of the headers!

quattrorunner 11-02-2006 03:25 PM

N/A guys are fine with this(coating inside). Like kevin has said, it needs to be cleaned, degassed, sandblasted and then coated after a final particle removal process. The insides obviously don't get the sandblasting/beadblasting done other than the ends that are reachable by the ends. This is the most important part of the process. The headers that are for N/A cars get the inside as an upgrade or bonus if this is the poilcy of the coater, so they would think they were doing you a favor if it gets done. And the guy coating is probably some guy getting just over minimum wage in some cases, so he may not have the gearhead smarts to figure it all out himself. It's really important that you make it known it should be uncoated. Big red letters on a sticker on the part when you ship it. If it were possable to sandblast the inside of the part, I think the flaking issue would be solved. The coating does keep the part cooler on the outside in comparison to no coating, and would be even cooler if it were coaten inside as well.

Craig 930 RS 11-02-2006 03:54 PM

Wyd - Ah the internet - we on Pelican are contentious on everything aren't we? :cool:

Still not sure if I personally see the benefit/risk ratio as being in my favor, but that option is one some may want to use.

quattrorunner 11-02-2006 03:57 PM

It is for those that want to outrun the other person at all expense. And I personally think it looks cool in white or light grey.

Randy Blaylock 11-02-2006 04:38 PM

If you coat your common lower price point aftermarket stainless headers, and ever have a crack (and it's when, not if) that needs repair, sorry charlie....

It's simply not possible to debride the base metal of the coating media thoroughly enough to get a weld of a character and quality that's worth doing, it's new header time.

The cost vs. benefit relationship doesn't pencil out to me.

On the subject of headers, perhaps Kevin will weigh in with his experience on a realistic service life of the garden variety headers from B & B and GHL, vs. other custom headers fabricated with superior alloys, or even inconel.

quattrorunner 11-02-2006 04:54 PM

The reason for the stress cracks is what? Heat cycling I guess.(I'm not sure) The reason for the coating is to keep the heat away from the header (or at least inside the tubes) The exhaust keeps the heat and not the headers in theory. So I would think that this coated header will outlast the uncoated part because it keeps it cooler. This is the selling point that coating companies sell. I used to work for one.

Randy Blaylock 11-02-2006 05:06 PM

Perhaps if the interior of the tubes was coated comprehensively, but as has been noted it's virtually impossible to prep the surface correctly, so the coating process will be inconsistent, and likely incomplete.

Given the advisory, in this particular application, to NOT coat the inside of the tubes, because of FOD concerns, the coating on the outside will only contain the heat inside the tubes, with no protective quality for the base material.

I'd hazard a guess that only coating the outside, while probably showing some benefit with regards to exhaust gas velocity and energy transfer which will reduce lag, and lower ambient temps proximal to the hardware, will also cause the headers to act as more of a heat sink since the external coating will not allow the heat to escape as readily to atmosphere through convection. I don't know what effect this will have on material life, but my gut suggests that it's probably not beneficial.

Not to mention the inability to make repairs.

I have been wrong before though....

quattrorunner 11-02-2006 05:23 PM

You may be right, I just don't know. My guess is that it would be better than nothing to have the outer coated but not the inner.

Ken911 11-03-2006 12:18 AM

Part of the reason stainless steel headers crack is from Chloride stress cracking corrosion. They will all crack due to this just some sooner that others even inconel will crack from it. The stress from heat distortion, the heat itself and the exposure to chlorides (road salt dirty rainwater etc.) will cause this type of corrosion. It is not notcible like general or pitting corrosion the metal will just crack at a high stress point. If these headers are new before they are coated IE never been exposed to rain water and road salt. then the coating should prevent or at least prolong the time until the headers crack.

mb911 11-03-2006 02:43 AM

typical cracking of stainless is caused be overzelous welders welding to hot causing carbide parcipitation which in turn will crack over a short term or long term depending on how hot it was. Not toot my own horn by I teach metal science and welding along with being a CWI so now I do have more experience with this then the average internet guy:D

Ps Not being a jerk or anything but who is kevin???

Jim2 11-03-2006 06:42 AM

Over and above what Ben said, the headers we use don't have sufficient expansion points to allow for material growth at operating temperatures. By comparison aviation exhaust systems have bellows or slip-joints at most multi tube unions or collectors. Our header tubes are welded to the collectors, and have minimal usage of expansion joints. Too many rigid mounting points as well.

From room temp to 1600F, 12" of stainless tube can grow upwards of 1/16" and is subject to continuious variations from 900F at idle to 1300F cruise, to 1600F on boost, so the header temps are changing constantly while driving, as a result they continously change shape to a minor degree, and if there are limited expansion points, they eventually develop cracks.

On a different note, some advertisments I read claim to have turbo headers made from "aviation grade 304 stainless". 304 is not (never) used for comercial aviation exhaust. I guess the statement helps sell product. Aviation is 321, it demands a price premium because thin wall 321 tube only seems to be used... in aviaiton exhausts.

Zeroclearance 11-04-2006 08:43 AM

mb911, you can always do a search..

Home of the K27 HyFlow...

rsrfan 11-04-2006 08:53 AM

Kevein is Kevin Matwichuk of Ultimatemotorwerks, . Kevin is THE Porsche turbo guru on Rennlist and many other forums. Kevin is responsible for creating new variants of the venerable KKK turbo chargers with new castings and CNC millwork. The k27 "s" and k27 "HFS" variants are his. He is also responsible for the "zero clearance" process used on Craig's beast. He is truly accessible and will talk with you for hours on your turbo specific needs. He is one of the good guys.


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