Hey guys,

What are your thoughts on ceramic coating stainless exhaust manifolds? I've seen a few manufactures claim that coatings will void the warranty. Can someone point me in the right directing with regards to the effects of such coatings on schedule 10 manifolds?

Reason I ask, I've had my first manifold failure. Customer ceramic coated the manifold, and the wastegate practically fell right off. The crack looks like it starts right next to the weld. Weird part is, the manifold barely has 10 hours of use on it.

I've never had a manifold break before and I want to see what I can do to avoid this in the future, and hopefully protect myself the next time someone decides to coat one of my manifolds.

Thank you for your time!

 

In all reality 304l stainless is not meant for the heat that turbocharging produces.
If I remember right 304 begins to break down around 1300 degrees and EGT's under full boost typically reach as high as 1500, when the manifold isn't coated the air around it helps to absorb some of this heat and therefore the manifold never actually reaches those dangerously high temps, however when you coat it there is no where for to heat to go except into the metal therefore drastically reducing its strenght.

I would suggest to run sch 40 instead of 10 in the future for manifolds that are to be coated but that still wont fix the heat going over the metals properties. Try looking into 316 elbows instead of 304, they handle the heat a little better or if you can afford them 321 elbows which are meant for the abuse.

 

Most companies will not warranty manifolds that have been header wrapped either for similar reasons, also a header wrapped manifold will retain water and rapidly oxidize the metal.

 

I've said it a million times, but here it goes.

I ceramic coat all of my manifolds. Inside and out, INSIDE being the most important. However I use mild steel, it is more reliable than 316 or 304 for manifolds. I have never, ever had a manifold failure. And some of my manifolds have been tested in the worst possible conditions.

 

We ceramic coated a few manifolds at the shop I used to work at, I've seen mixed results. One manifold was a ramhorn for a Honda B series, it was run for a long time before coating, then sold to someone else who had it coated. It cracked at the wastegate flange as well. To be fair the welding on the WG stalk was not necessarily the best, and the whole setup ran open (unsupported) downpipe for many many miles before it broke. The guy who has it is a friend of mine and he literally drove across the country with it (a few trips from Atlanta to Melbourne FL, then to Philly, then out to Boise). Also of note, this is the manifold I asked about a while back, where the flanges and welds all seemed to be ferrous, a magnet will definitely stick to them.

On the other hand... we did a simple miniram type manifold for a turbo Lotus Elise, which was coated from day one. This manifold never had an issue, despite no flex in the downpipe and everything fitting VERY tight. The motor was a built 2ZZ with WMI, running 16-20ish psi on a GT2860 depending on the fuel and map selected. The temps were very very hot with that car, it had a single (but thick) sidemount intercooler mounted just aft of the driver's door, so that cut out a lot of already low airflow. The coating on the manifold flaked off a couple of times, and the coating place warrantied it every time. They said they had never really seen that before, and for this particular coating we were using they said it must have sustained 1100F for a little while to dull the look, and they didn't know at what temperature it would peel off. The heat also dulled the coating on the downpipe near the turbo, but it never broke. Just about every time we had to pull it out and get it recoated it was following a track day at Sebring or Roebling Road.

Here's a pic of the Lotus manifold for reference:


Not a great pic, but you can see the dulling on the downpipe. This pic was taken one of the times the manifold came back with a fresh coat on it.

 

Thanks for your input guys. I may not have much to say right now, but I read every word and am really paying attention. Thank you.

The engine is currently on an engine dyno and they are setting up the standalone. The part that really gets me is how soon this happened. Like, the engine is barely broken in, and the wastegate came off?

Normally, the wastegate is partially supported by the wastegate rereoute into the downpipe, but they just connected it straight into a muffler because the downpipe wouldn't clear the engine dyno (needed to be rotated).

So now I guess it's a combination of the coating overheating the metal, and a heavy muffler hanging off the wastegate.

Manifold is half way across the continent, and he needs another one, but it was a one off, so not sure what to do now.

Thanks for your input guys.

 

ouch on the half way across the continent thing... this is partly the reason i only do fabrication for locals. it is easier for a customer to come back and do a repair (i've had 4 in the past). only one was coated and it was a downpipe pipe cut that wasn't really welded that well to begin with. two of the others were related to wastegate branches at the collector on uncoated manifolds where the customer had done their own downpipes (maybe part of the reason?), the last was a turbo flange crack at the collector. i've seen far more manifolds for repairs though than i've had to fix my own. it is good to see them because i can analyze the failure and try to avoid that in the future on any manifold i do for a customer. i do get customers ask about coating, i don't recommend it, but if they want to i suggest they do it atleast a year after running the manifold without it so if there are any issues they can be addressed before it gets coated and they don't have to re-coat it a second time. i don't say it will void the warranty but i certainly don't recommend a customer have it coated. i absolutely advise against wrapping a manifold though. like james said, there is no where for the heat to go, so it overheats the material to the point of failure... but it is even worse with wrap, because it could possibly hold moisture/condensation close to the base metal on start up and that can't be good for a manifold i'm sure.

 

That sucks man.
Can they over night it back, you get it blasted real quick, welded re coated and than shipped back out?

I can't stress how important it is coat a manifold on the inside, if only coated on the outside the material just gets heat soaked to the point of failure.

 

More likely than a bad weld or the steel breaking down from the retained heat, I would point my finger at a strong harmonic destroying the WG tube. It's amazing how much an unsupported, weighted, mass can vibrate on the end of a fairly rigid structure like a thick turbo manifold. I think that sometimes you just get unlucky and build a setup that vibrates horribly at a particular RPM and fatigues the parts at a very fast rate.

 

This is the reason I do not touch SCH10 anymore, the only cracking issues I've ever had with manifolds under 30K miles were cuz I built them out of Sch 10

 

So did they make the dumptube, or did you ? I have seen in some instances where the dumptube was actually causing the wastegate elbow to crack, I had a customer that was making his own dumptube, and he was using very heavy home depot type pipe, and it was very long. I believe the weight and the vibration was leading to this type of crack.

Just tossing it out there.

 

if they had a muffler hanging off the wastegat i would not help them. as that is not what a wastegate is ment to hold.

the only failure's i have had was once on a dump tube (16g and very long), and the back side of a collector that i didn't put a big enough weld on (width).

I don't see how anything thicker then sch10 is needed. i mean sch10 is already thick as ****. sch40 is just plain stupid.

 

just to clarify, there is not a muffler hanging off the wastegate... the mufflers are 5 feet tall and are mounted outside of the room... there is a (supported by stands to the floor of the dyno room) 3" tube attached to a dump tube with a very loose slip fit... the dump tube sits about six inches inside the 3" tube... the wastegate supports very little of this load (due to the slip fit being loose)... but it is supporting some, but i don't feel it is any different from what the wastegate would see if the return into the downpipe was used

i have my own theories on why this failure happened... simply put, heat.

-franz

 

I've made a few manifolds with schedule 40 in the past, and it's something I want to avoid doing again. The time involved in preperation and welding is twice that of schedule 10.

I did some reading last night and it really seems as though 304 is not a great choice for turbo manifolds. 316 is iffy too it seems.

Before making this manifold, we looked at 304 vs 321 and decided on 304 because of the cost of the 321 elbows. Looking back, we should have bit the bullet and used 321.

Franz, sure does look like heat eh? And considering the crack looks like it developped next to the weld, I don't think it was a bad weld that caused it.

Another thing, (from what I have heard, no test data to prove it) is the 1.8T engine is known to vibrate a lot compared to other engines, and this has shown itself with manifolds that mount the turbo turbine at a 90°, especially cast iron manifolds, where the turbo bolts back out no matter what you do to secure them. We had this problem on a TT race car. The team got so fed up they decided to weld the turbine housing to the cast iron manifold, and so far it's been the only way to stop the problem. In this case, I think the position of the wastegate is acting like a hammer at the end of a long tube ... Combine that with the tortured T304 and this is what happens.

 

Agreed, 90% of the time we've ever seen a failure here its material fatique. Its just to bad the market would never support the use of higher grade materials to avoid the issue.

A lot of these cars these days run a solid mount @ the point the dumptube really creates a stress if unsupported. Seen dumptubes physically vibrating and @ that point its just a matter of time.

 

So now, apparently the downpipe is cracked too. This is not making sense!!

 

Was this stuff backpurged? How many amps did this material have in it?

 

The downpipe cracked on the referenced above setup (the Honda one) as well. I definitely agree on the vibrations, that's what I was getting at. I've repaired and replaced a lot of longer dump tubes from that in various materials.

 

Yes, everything was backpurged, including the downpipe and manifold. Amps, I couldn't tell you, but I know it was all full pen ...

 

I'm just wondering how much energy the material absorbed from the welding process, some of the industrial stuff I do this becomes a big factor. Which is one of the reasons when I do high heat high vibration stuff they require no filler for .065 wall tube, the extra energy/heat it requires to melt the filler into the parent material causes a grain breakdown which weakens the material in the HAZ area.

 

So now, what can I do to prevent future cracking once I fix it?

Thanks!

 

Too bad to hear that. But I'm still thinking that your manifold are insane.
Dont stop good work and find a solution.
Good luck

 

Correct me if i am wrong...always open to learning new things BUT is there not a HIGH risk to coating the inside of a manifold? Reason is for the possibilty of chipping off of the material and furthermore damaging the turbo?

All reputable companies that I have spoken to do NOT coat the inside...it would be ideal for the obvious reasons but i think they are to worried about the risk of damaging anything else.

Most ceramic coatings are 1600 for the shiny blingy stuff and 2000 deg + for the black stuff...theoretically they should not chip off.

 

Some people call them reputable, other people call them ignorant but popular.
If a small piece of ceramic coating were to chip off I wouldn't be too worried about it, ceramic coating is .003" or thinner, I haven't seen the coating flake however. And I've used it for the combustion chamber of heads, exhaust ports, valve faces, piston tops and even the turbine wheel itself. Quality coatings won't flake if they are applied properly.

 

Agreed "if" applied properly. Now those ignorant yet popular companies that you mentioned cannot be trusted than who do you use? PM me if you do not want to mention name on the post. I am talking about the coatings that many manifold companies include as an extra $ $$ option...

What is the proper process to coat a manifold? From my understanding you prep the surface then apply the ceramic coat and then bake it....but what are the "specifics" in doing this the right way?

thanks!!