What is so good about ceramic coating a TD5 manifold?

[Parker]

Hi Folks,

corona makes you ponder stuff. In a response to another question of mine there was a comment to ceramic coat the TD5 manifold.

Previous owner had the TD5 head replaced, and the manifold faced and refitted. They did not de-web the manifold but it seems to be ok so far.

I'm a structural engineer so know a bit about steel and heat. If I have problems with the manifold the future then I would de-web it, and elongate the external bolt holes. I've had a look and it seems even possible to drill the web in-situ to weaken the web but I won't do that unless I really have too much time.

But why ceramic coat the manifold in and out, will that really dramatically change things and is there evidence or is it just that it seems to make sense?

I should say that where I am in central Victoria there is a ceramic coating mob so it would not be a lot of bother to have it done.

Thanks for your comments/thoughts/ideas!

[Tombie]

Hey Parker...

Seeing I’m the one that likely planted that seed, here’s a quick link to cover off the basics.


5 Important Reasons You Should Ceramic Coat Your Exhaust Headers and Turbo Parts — Jet-Hot (https://www.jet-hot.com/articles/2018/6/29/5-important-reasons-you-should-ceramic-coat-your-exhaust-headers-and-turbo-parts)

I’ve been involved in High Performance vehicles for 30+ years, on custom intake and exhaust gear I’ve always done the ceramic coating. The benefits have always been quantifiable either in power, temp or longevity (or a combo).

[Dorian]

Hi Parker,
This is more along a 'thoughts' line. Taking the view that your more interested in warping than engine performance and drawing from my limited and rarely used knowledge acquired decades ago at uni.

A cast iron manifold would warp from mainly two reasons, the differences in expansion geometries / profiles within the manifold would cause the material to deform or that the operating temperatures of the manifold would cause some heat treatment / crystal phase change within the cast iron and hence some dimensional changes.

If you ceramic coat it the material temperature of the manifold would change less quickly, which should mean the temperature differences within the manifold ( Web temp vs pipe temp) would be lower and at least the warping would be a lot less. The final internal temperature of the manifold probably would be the same given the motor would be in operation for a few hours on many occasions so any "heat treatment" would probably still happen albeit at a slower rate, but this would still produce the same final warping.

Given that the collective experience of TD5 owners that have had to have manifolds shaved is that, whether you remove the webs or not, once it's warped and fixed it doesn't happen again and if you get a new manifold ceramic sprayed before you put it on your motor it still warps. I'd place a modest bet that a fair percentage of the warping is due to some heat treatment going on. (But the optimist in me is confused, as you would think that the manifold would have bean heat soaked during manufacture.)

So as a thought I'd say that in your case, coating your old manifold won't help with warping as your unlikely to get the problem on a previously machine manifold.
From my experience ceramic coating your manifold white noticeably reduces engine bay temps but on a stock D2 engine I couldn't notice any engine performance improvement.

Cheers Glen

[PhilipA]

Previous owner had the TD5 head replaced, and the manifold faced and refitted. They did not de-web the manifold but it seems to be ok so far

I can only speak from my own experience.

I noted the recommendations on the forum to reface the manifold,, de web the manifold, and ceramic coat.
I replace dthe studs with Mercedes Benz studs from UK with copper flashed nuts. I also added Belleville washer as I thought that they would maintain tension on the nuts but also at the same time allow the manifold to slide as it elongated with heat.
I had the manifold ceramic coated and the operator said that he managed to as he said almost completely coat the interior.
All of these activities were aimed towards reliability and the desire to not have to remove the manifold again.
The manifold has been reliable for about 60KK now.

Some things I noted. The warp increased when I dewebbed the manifold by a couple of MM, which is a pretty big change.

I elongated the end holes and second ones because I note that mainly the rear and front studs were always the ones that break, and IMHO it is because they get a lot of side stress as the manifold extends with heat. Toyota six turbo engines even have a 2 piece manifold with a sliding section to alleviate this. Obviously the elongation has the be biased toward the outside/end of the manifold. So far so good.

I have a reasonably hot tune in my EU3 D2 and the EGTs can easily run over 700 to 750 if not watched closely.
The other thing I did which was not so good was to not remove the turbo because of the diabolical drain bolts, and I broke the drain which leaked and had to be replaced.

I have my EGT gauge sender drilled through the "dimple" just in front of the turbo so my temps are manifold temps. Probably higher due to the insulating quality of the ceramic coating.
I would ceramic coat again.
Regards PhilipA

[Tombie]

I have seen plenty of warped, remachined manifolds warp again.

What happens when the webbing is destressed is that this no longer pushes the manifold outwards as it heats. Therefore it doesn’t apply any longitudinal forces along the manifold forcing the outer ends to move / warp.

The ceramic coating internally helps maintain gas velocity through the manifold rather than soaking into it which improves flow. External spraying also helps keep the heat away from the other components.

I haven’t personally heard reports of any manifold that has had this treatment having further issues and have never had problems since going down this path.

I’m running on of the most aggressive tunes you’ll see on a TD5 for 180,000km and without further issues. Make of that what you will. Others who followed my recommendations all seem to have solved their issues.

[Parker]

Really appreciate these comments!

When fixing things I usually err on the side of caution and in this case would just coat the thing.

Tombie, what does ‘one of the most aggressive tunes’ consist of and how much does it influence EGT? I ask this because I’m trying to get a Nanocom to then flash the ECU somewhat for my driving style and use.