Author Topic: Ceramic Coating  (Read 24710 times)

May 06, 2007, 02:08:19 pm

JetPo

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« on: May 06, 2007, 02:08:19 pm »
Hi every body  :P ,

I have read some threads that were talking about ceramic coating, pistons, pre-chamber and the chamber for less temperature loss so better combustion. I wanted to know if someone had actually tried it and as seen results.

Thanks
Alex



Reply #1May 06, 2007, 11:54:06 pm

935racer

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« Reply #1 on: May 06, 2007, 11:54:06 pm »
Yep I am pretty sure I have tried ceramic coating the following for the 1.6 IDI engines:

Intake valves
Intake ports
Exhaust valves
Exhaust ports
Piston tops
entire deck surface of cyl head
pre cup faces
pre up insides
pre cup chambers
injector faces

Out of all these the only beneficial ones seems to be piston tops, exhaust ports, and exhaust valve faces.

DO NOT ceramic coat the precups, this keeps heat out of the pre cup which hurts performance, the pre cup is designed to absorb heat for the IDI combustion process.
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Reply #2May 07, 2007, 08:16:25 am

jtanguay

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« Reply #2 on: May 07, 2007, 08:16:25 am »
what if you were to coat the other side of the pre-cup to keep heat in the precup only??? would that work???


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Reply #3May 07, 2007, 12:11:12 pm

935racer

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« Reply #3 on: May 07, 2007, 12:11:12 pm »
Quote
what if you were to coat the other side of the pre-cup to keep heat in the precup only??? would that work???


See that is actually the common misconception, if you CC a precup the iconel no longer absorbs as much heat as it originally did, so it is much colder, heat is not trapped but reflected.

I just had a PM about why I wouldn't bother CCing the intake valve faces but  would on the exhaust side, simply the exhaust valve is getting head soaked from the port and manifold pressure, the stem on the intake side has pressure of cool air, the exhaust side has a pressure of cooking hot air, the exhaust valves maintain a much higher overall heat, even though both faces are exposed to same amount of heat during the combustion process. This is why exhaust valves burn out faster than intake valves.
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Reply #4May 12, 2007, 10:41:22 pm

subsonic

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« Reply #4 on: May 12, 2007, 10:41:22 pm »
Do you think you could prevent the cracks between the valves on the head if you ceramic coated in that area?
2009 Jetta TDI Loyal edition, 6-spd. 16V 2.0CR


1985 VW Golf 5-spd, 4-door, 1.6NA  Bought from orig. owner in Savannah with 42,000 miles.
"Making the jump NA to TD" slow but sure.

1980 VW Rabbit LS 5-spd, 4-door 1.6NA almost 450,000miles  RIP

Reply #5May 12, 2007, 11:45:06 pm

QuickTD

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« Reply #5 on: May 12, 2007, 11:45:06 pm »
Quote from: "subsonic"
Do you think you could prevent the cracks between the valves on the head if you ceramic coated in that area?


 I don't think so, those cracks seem to be the way the IDI heads relieve internal stress, both mechanical and thermal. I would be very suspicious of any head that wasn't cracked there, as I've never seen one before...

Reply #6May 13, 2007, 12:12:55 am

tylernt

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« Reply #6 on: May 13, 2007, 12:12:55 am »
I just pulled the head of an '84 1.6TD out of a Jetta, no cracks. Well, I haven't cleaned the carbon off yet so there may be hairline cracks but nothing obvious.

My theory is that the cool intake air on one side and the hot exhaust on the other side is what creates them. I suspect that thermal coating the exhaust port will slow or prevent the crack formation. Just IMHO though, I'm not an engineer so I could be totally wrong.  :P
'82 Diesel Rabbit, '88 Fox RIP, '88 Jetta (work in progress)

Reply #7May 13, 2007, 12:26:01 am

jtanguay

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« Reply #7 on: May 13, 2007, 12:26:01 am »
Quote from: "935racer"
Quote
what if you were to coat the other side of the pre-cup to keep heat in the precup only??? would that work???


See that is actually the common misconception, if you CC a precup the iconel no longer absorbs as much heat as it originally did, so it is much colder, heat is not trapped but reflected.

I just had a PM about why I wouldn't bother CCing the intake valve faces but  would on the exhaust side, simply the exhaust valve is getting head soaked from the port and manifold pressure, the stem on the intake side has pressure of cool air, the exhaust side has a pressure of cooking hot air, the exhaust valves maintain a much higher overall heat, even though both faces are exposed to same amount of heat during the combustion process. This is why exhaust valves burn out faster than intake valves.


Ah... so what you're saying is that the pre-cup doesn't hold any heat? its the heat around it that radiates inside???


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Reply #8May 13, 2007, 12:58:52 am

tylernt

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« Reply #8 on: May 13, 2007, 12:58:52 am »
Quote from: "jtanguay"
Ah... so what you're saying is that the pre-cup doesn't hold any heat? its the heat around it that radiates inside???
Yep, that's why diesels are more efficient the hotter they run (until you warp the head or crack something  :oops: ).
'82 Diesel Rabbit, '88 Fox RIP, '88 Jetta (work in progress)

Reply #9May 17, 2007, 07:40:42 pm

Mark(The Miser)UK

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« Reply #9 on: May 17, 2007, 07:40:42 pm »
Quote from: "tylernt"
Quote from: "jtanguay"
Ah... so what you're saying is that the pre-cup doesn't hold any heat? its the heat around it that radiates inside???
Yep, that's why diesels are more efficient the hotter they run (until you warp the head or crack something  :oops: ).


Isn't it the compressed air that carries the heat? Heat lost through swirl chamber walls to coolant surely drops the pressure. Thus less energy to do work. So how much better would a TDI be if head/piston face were ceramic coated?

Anyone yet cast a ceramic head?
Mark-The-Miser-UK

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I'm not here to help... I'm here to Pro-Volke"

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Reply #10May 18, 2007, 12:46:21 am

tylernt

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« Reply #10 on: May 18, 2007, 12:46:21 am »
Quote from: "Mark(The Miser)UK"
Isn't it the compressed air that carries the heat?
Most of it, yes, but it's easier  to reach the 1500*F ignition temperature when the chamber walls are 212*F vs. 72*F.
'82 Diesel Rabbit, '88 Fox RIP, '88 Jetta (work in progress)

Reply #11May 19, 2007, 09:25:13 pm

Mark(The Miser)UK

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« Reply #11 on: May 19, 2007, 09:25:13 pm »
Quote from: "tylernt"
Quote from: "Mark(The Miser)UK"
Isn't it the compressed air that carries the heat?
Most of it, yes, but it's easier  to reach the 1500*F ignition temperature when the chamber walls are 212*F vs. 72*F.


h'mm...
It's a bit of a connundrum :?  Heat loss through a ceramic coating if my memory serves me is about 2/3 of a bare surface. What's the theoretical temperature of air @23:1 squeeze? 600 deg C ?  Energy losses in a diesel? 1/3 exhaust 1/3 head and 1/3 work done?  Maybe exhaust losses come down to 2/9 with a turbo or better? leaving 7/9 for head and work done.. 7/18 head and 7/18 work done  :shock:  Now introduce ceramic coating...
 5/18 head and 9/18 work done :lol:
 work done now 50%??

Someone correct these figures.
Tylernt where did your 2 fahrenheits come from?
Mark-The-Miser-UK

"There's nothing like driving past a bonfire and then realising; its my car on fire!"

I'm not here to help... I'm here to Pro-Volke"

Be like meeee: drive a Quantum TD
 ...The best work-horse after the cart...

Reply #12May 19, 2007, 10:45:24 pm

jtanguay

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« Reply #12 on: May 19, 2007, 10:45:24 pm »
there was talk previously about using zirconium oxide coating... i think that might have a good chance at working...


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Reply #13May 19, 2007, 11:54:51 pm

tylernt

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« Reply #13 on: May 19, 2007, 11:54:51 pm »
I was wrong on the 1500*F, it's actually 1650*F per the Engine section of the Bentley, pg 5. The 212*F comes from the radiator fan / thermostat temperatures.

I'd agree that thermal coating the combustion chamber *should* help, logically, but somebody on here was saying they tried it and the results were terrible. Since reality trumps theory, I guess my reasoning was wrong. I can't explain the results, though.
'82 Diesel Rabbit, '88 Fox RIP, '88 Jetta (work in progress)

Reply #14May 20, 2007, 02:27:44 am

jtanguay

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« Reply #14 on: May 20, 2007, 02:27:44 am »
theoretically if you can keep 100% of the heat inside the chamber it would be extremely efficient.  but that's kind of impossible.


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