Manifolds - Wrap or Ceramic anyone interested in a comparison?

[oldtuckunder]

Duplicate

Edited December 3, 2017 by oldtuckunder

[oldtuckunder]

For those interested, I found the following on under bonnet exhaust temps. NB looks like using thermocouples only clamped on doesn't give accurate results, so probably means my amateur attempts to get anything meaningful using IR temp sensors is probably even more so.

 

http://depts.washington.edu/vehfire/ignition/autoignition/surftemperdetail.html

 

Alan

[Waldi]

AlAn,

The IR thermometer will be more accurate in this case, because the spot-welded thermocouple wires tend to cool the couple a bit, hence giving lower readings.

We use spotwelded TC's a lot in my work for example to measure a component in a heating oven to monitor post weld heat treatment temperatures, that is a correct use of spotwelded TC's, since the heating nedium and the component (abd the TC) are almost the same temperature.

Regards,

Waldi

[oldtuckunder]

OK I'm going to declare that Ceramic Coating of Exhaust Manifolds for heat reduction is rubbish!

 

I'm not saying don't do it, but that if you think its going to solve under bonnet temperature issues, it isn't.

 

I have read and read, I have followed every link and bit of information I can find put out by the coating manufacturers and there is nothing "real" in terms of evidence that they have anything but the slightest impact on convected or radiated heat in the engine bay. At best they may marginally assist with radiated heat but only to the extent that if they are shiny they will radiate less than a dull surface, but no less than a shiny surface, but they will keep that finish much longer.

 

What are Ceramic Coatings good for? If you read all the manufactures blurb on these products they are designed to protect the metal that they are coating from corrosion, the fact that a thin ceramic coating may also have a tiny Thermal Barrier Effect has been hyped in almost urban myth proportions to imply that they will do magical things to reduce under bonnet temperatures. They won't to any extent that a road car or most private competition cars will benefit from, perhaps at the very pinnacle of motor sport where every 1/100th of a percent of gain can be justified its worth it, but those people are using real hot ceramic spray coatings, not something out of a tin that is baked in an oven afterwards.

 

If you carefully read the manufacturers site information (which is mainly USA where Trading Standards don't seem to apply, and Buyer Beware rules) even they don't really claim much Thermal Barrier effect or supply any data, they liberally band the phrase around, and as you follow the links to the companies that use the products to treat manifolds, and the end customers that have paid money for it, the claimed benefits in heat reduction grow at every step!

 

The only quotes I can find from people who work for the actual manufacturers of products like Tech Line are.

 

"In some instances, such as exhaust systems, you want to keep the heat flowing through the part rather than being absorbed by it and manage heat that reaches the surface so that it radiates away faster, to reduce surface temperature and to reduce heat transfer to nearby components."

"The Turbo X system is designed to not simply be a thermal barrier but to also shed heat off the surface keeping the surface cooler and radiating less heat to the nearby components,etc."

Which actually introduce a negative effect. In that whilst referencing the reduced Radiated Heat effect (from a shiny surface) it implies that they may well actually conduct more heat away into the air, which may well be worse for under bonnet temperatures than any gain from cutting down radiated heat.

I did find one long thread in which a Manager from Tech Line contributed openly, and whilst a lot of it is about applying ceramic coatings to Pistons, Valves, Heads etc. which also seems to be a candidate for Snake Oil, does have some revealing insights.

http://speedtalk.com/forum/viewtopic.php?f=1&t=1050

But ceramics are good at what they were developed for, corrosion protection from heat, solvents, rust, moisture etc. OH and looking good!. Without doubt if I had a mild steel exhaust manifold/headers I would get it ceramic coated. not for any heat reduction benefits, but purely because I think they do what they claim which is to stop them corroding and looking good for a long time.

 

I know for sure from personal experience that wrapping plain mild steel headers they are going to rot out fairly fast and there is a lot of evidence to support this (although some of this may be down to cheap steel pipes being wrapped), and that most of the VHT paints you can buy don't last very long. So ceramic coating of engine bay components is likely to have long term cosmetic benefits.

 

If you really want under bonnet heat reduction, then heat shielding and wrapping is the way to go. And it certainly seems probable that ceramic coating a mild steel manifold before wrapping may improve its survival chances.

 

If you have Stainless Manifolds, then ceramic coating will also keep them looking prettier longer if unwrapped, but for heat reduction wrapping SS manifolds appears to be a no brainer as they don't suffer the same corrosion issues as Mild Steel.

 

But wrapping has its issues, I'm convinced that re-wrapping my old mild steel headers 3 times over the past 4 years has cost as much as ceramic coating, plus the time doing it, none of it is as good as claimed, on primary pipes it all degenerates, goes brittle and starts falling off as it has very little abrasion resistance once it has gone brittle. i.e. if you are likely to be taking the manifolds on/off frequently you are going to be re-wrapping. Also if you are tight for room the extra 1/4" dia its going to add to the pipes can be a pain. And from a cosmetic view point it does start looking shabby.

 

So what am I going to do with my SS header's ?

 

I'm going to get them a shiny ceramic finish, not because I think it will have any positive heat benefit (and we will measure that) but purely because it will keep them looking nice, as even SS discolours. I'm resigned that as soon as fitted and tested, that I will have to resort to some wrapping and possibly some extra clever heat shielding to achieve the heat suppression I enjoyed with the previously wrapped pipes.

 

But maybe one day when competition time is over, the car may have a nice set of presentable headers still fitted.

 

Alan

[john.r.davies]

Alan,

I mentioned this before, but in support of your case against ceramic coated (or wrapped) headers, as a means of reducing under bonnet temperature, I did an experiment.

That wasn't the objective, it was an aero project, to reduce as much as possible the air flowing under the car, innpusuit of downforce (as in less lift) by putting the radiator of my old Vitesse Estate in the back.

It worked, on the road, but boiled over on track, and I certainly didn't leap to the front of the grid, so not a successful experiment.

 

My point is that it was a cold car to drive. Almost all the heat under the bonnet comes from the radiator. Even with a tubular manifold (more surface area, so more heat loss than a cast) it never got hot there, The pipes were hot, but nothing else.

 

John

Edited December 15, 2017 by john.r.davies

[oldtuckunder]

Someone found the following FAQ's on the web site of a ceramic coating specialist, just about says it all

 

Alan

 

Will the ceramic coating last forever?

Our ceramic coatings are very durable. Depending on the use of the car/bike, where it would be used and the environment where it would be used, the coating can change durability. We have customers that have done ceramic coatings with us for a long time now and they have experience no problem at all. Even on motorbikes, where the exhausts are more exposed than on a car.

What is the difference between exhaust wraps and your exhaust ceramic coating?

Exhaust wraps are very good. They are. For the purpose. They’re accessible and they have a thermal barrier benefit. But the looks…

The looks are nice for a short period of time. Then they start disintegrate themselves and they start look bad. They don’t last long and it is something you have to be doing again and again. With our exhaust ceramic coatings, you only do it once. Our exhaust ceramic coatings are durable and they offer the same look for an extended period. Your car/bike will look cleaner and, specially with the colours available, you’ll get a WOW factor, that you can’t get with the exhaust wraps.

Will your ceramic coatings give a boost in power to then engine?

Yes. They will make the engine gases flow better and that will improve the engine’s breathing, improving performance.

What are the benefits as a thermal barrier of your ceramic coatings?

Our ceramic coatings are produced to give an enhanced look to your car/motorcycle while helping reducing the surface temperature. External testing has shown reduction values in the order of 12-15% from our exhaust ceramic coatings.

Does coating the inside of the manifold avoids corrosion?

Yes it does. But, we do not warrant the coating on the inside pipes.

[oldtuckunder]

 

My point is that it was a cold car to drive. Almost all the heat under the bonnet comes from the radiator. Even with a tubular manifold (more surface area, so more heat loss than a cast) it never got hot there, The pipes were hot, but nothing else.

 

 

 

Reinforces my comment earlier in the thread that the temp of the pipes dropped almost instantly the fan cuts in, even if that air is warmed by the Rad its way cooler than the wrapped pipe. So may be although I have extensive heat shielding keeping the carbs and inlet cool and separated from the rest of the under bonnet area, it may be a good ideas to investigate managing the air flow when the fan cuts in (especially when idling as that is when the temps really start rising) to direct it away from the header pipes so they stop acting like a fan heater.

 

Alan

[BlueTR3A-5EKT]

As an apprentice, involved with the overhaul of Rolls Royce Dart turbo prop engines, the processes used to coat the combustion chambers flame tube outer casings against corrosion were either pure aluminium metal spraying and a ceramic coating named Solaramic. Solaramic was by far the better corrosion resisting coating, as observed at return of time expired engines for overhaul. Every aluminium sparyed can had to be blasted clean and recoated, whereas not every green coloured Solaramic one did. This fact impacted on the cost of engine overhaul.

 

Sadly Solaramic was not available in house, so I coated my TR exhaust manifold with metal sprayed aluminium (one Friday afternoon, as you do) and now after some 45 years, it is only just starting to flake. I had a big box for my lunch that day!

 

Solaramic process - https://www.flightglobal.com/FlightPDFArchive/1953/1953%20-%201076.PDF

Aluminium metal spray process - http://www.praxairsurfacetechnologies.com/-/media/us/documents/brochures/thermal-sprayed-aluminum-coatings-for-oil-and-gas.pdf

 

My own TR has wrapped stainless steel exhaust manifold now and I am pleased with the underbonnet temp drop and the improved 'stuck in traffic' tickover.

 

Cheers

Peter W

Edited January 7, 2018 by BlueTR3A-5EKT

[oldtuckunder]

so I coated my TR exhaust manifold with metal sprayed aluminium (one Friday afternoon, as you do) and now after some 45 years, it is only just starting to flake. I had a big box for my lunch that day!

 

My own TR has wrapped stainless steel exhaust manifold now and I am pleased with the underbonnet temp drop and the improved 'stuck in traffic' tickover.

 

 

 

Funny! I have the original Cast manifold for my Vitesse still in storage. An Uncle must have borrowed your Lunch box as he got it Aluminium sprayed for me at Rolls Royce engines in Bristol back in the late 70's. Sat around for decades it still only has the slightest traces of surface rust, mainly around the bolt holes where I think a bit of stress cracking of aluminium must occur.

 

I'm fairly certain that after coating that I will find that I still need to wrap the headers, but we will see?

 

Alan

[oldtuckunder]

Well SS Manifolds back from ceramic coating!

 

And I must say they look pretty!, and if the advertising blurb is correct will stay so for a long time. Honestly can't fault the finish.

 

Will the ceramic coating achieve anything but looks? Have my doubts, went for the full 4 coat race finish to give it the best chance, will be a week or two before engine running, but thought I'd try a simple initial test, hold a cigarette lighter just inside the pipe with finger on outside, after about 1 min pipe too hot to hold finger on, try again on another pipe with a piece of wrap on outside underneath finger, after 5 mins lighter ran out of gas but no apparent heat.

 

Suspect I have been sold bought a pig in a poke, but we will see when the engine is running!

 

Alan

[RogerH]

Hi Alan,

in this test the fabric will work better but consider the other parameters.

The pipes look good

They don;t pose a fire hazard

The pipework that would have been under the wrap will always remain in good condition.

How much heat are you dealing with - your finger will sense quite low changes and feel hot.

Feel the heat of the exhaust gas with the ceramic coat - it will be considerably hotter.

 

Roger

[oldtuckunder]

OK Test Results in from Ceramic Coating.

Conclusion "Its Pretty" but "Its Pretty Rubbish" as an Insulator.

Finally all running again with super duper 4 coat race spec Ceramic Coating, 1 inside 3 outside, finished is a very shiny very dark grey.

I have reposted my results from post #63 with the originals in Wrap, and added the Ceramic results alongside.

Alan

I left the engine running for around 20 mins until nice and warm, not just coolant warm.

Set the engine at 1Krpm idle and took most measurements, then took up to 2Krpm and took a few more.

NB. The "A" readings were taken of the bare black metal flange of the headers where they bolt to the head (i.e. not under wrap)

"B" readings are about 2" down from the flange and under wrap.

NB The A2,A3,B2,B3 reading are higher than A1,A4 B1,B4 in Wrap because two pipes are sandwiched, in Ceramic they aren't sandwiched so had almost identical readings to outer pair.

Because I was suspicious anyway I added some extra heat shielding to protect the starter motor (glad I did) but it means I can't get a reading for E1 with Ceramic.

What was also interesting was that there was no temp drop with ceramic at C1,C2 when the fan cut in as there was with the wrap

Covering: Wrap Ceramic

Colour: Black Dark Grey

1K rpm

A1 220 230

A2 240 230

A3 240 230

A4 220 230

B1 200 300

B2 210 300 This is the reading for both pipes in ceramic

B3 210 300 This is the reading for both pipes in ceramic

B4 200 300

C1 280 & 250 350

C2 280 & 250 350

D1 235 280

D2 235

E1 180

2K rpm

A1 245

A2 300

A3 300

A4 245

B1 225 400

B2 250 400 This is the reading for both pipes in ceramic

B3 250 400 This is the reading for both pipes in ceramic

B4 225 400

Edited March 23, 2018 by oldtuckunder

[Waldi]

Interesting testing Alan, thanks for sharing.

A very thin layer of air, just 1 mm, would make a difference but I just wondered why a thin layer of dense material like a ceramic (coating) could be a good insulator, thought it would be due to reflection, apparently not.

Regards,

Waldi

Edited March 24, 2018 by Waldi

[oldtuckunder]

Sad to report, that in the Bling Stakes as well, its not much better than it is at heat insulation, they stayed looking nice during the 1/2 - 1 hour of idling setting up etc, but the first quick 20 min spirited blast today has started turning them a mucky brown at the hot spots at the top of the primaries (which was really the only visible parts anyway). They still look nice and shiny in the cooler secondary pipes, but I'd have to be running you over for you to appreciate it!

 

Well you live and learn, if it sounds to good to be true, it probably is. I hereby condemn Ceramic Coating to the Expensive Useless Bin.

 

Alan

[oldtuckunder]

Slightly more frightening appears to be not only is it useless, its damaging! After yesterdays test drive both my Wideband AFR sensors in the manifold are toast, or rather probably poisoned by the decaying ceramic coat inside the pipes. If one sensor had gone bad I'd have dismissed it, but two at the same time? And I've tested its not the controller because plugging a spare in and doing a calibration run it works perfectly.

 

I know leaded petrol kills the sensors, as well as silicon fumes, wonder what nasty is in that ceramic?

 

Alan