Author Topic: Ceramic Coating (Read 27710 times)

2446 · « **Reply #60 on:** June 15, 2007, 02:28:05 am »

toyota used to sell an engine with ceramic precups. It was called the 2L-THE and is the "high output" version of the 2LTE with more fuel and more boost. AFAIK it has not been used a lot, or for a long time, why I don't know. Maybe the improvements in materials used for the sindered steel inserts took car of the heat resistance, and the little (if any) efficiency improvements were not sufficient to justify the cost ?
The "toyota engine technology" book refers to it saying that ceramic was used to improve the strength and durability of the insert vs. higher temperatures encountered. Unfortunately the paragraph is super short and doesn't talk about efficiency or ignition delay.
Therorically the colder inserts would reduce the benefit of improved ignition delay when fuel hits the chamber wall. I think a coated precup engine needs a more advanced timing but wether you need an all different curve of just offset the stock one is unknown to me.
More advance and longer ignition delay will be more likely to produce diesel knock though.

subsonic · « **Reply #61 on:** June 15, 2007, 10:38:12 am »

If you have your pistons coated, how much will it increase overall length? Has anyone measured? Are we talking .001, .01 or what?

Mark(The Miser)UK · « **Reply #62 on:** June 15, 2007, 06:02:50 pm »

Quote from: "greg123"

Hehe, that may just work. Don't you know that you'll be able to get some sort of grant for £5 for being green too?? ;-) They gave me the same to fill in my cavity walls with insulation, but it appears they made my house with gaps 5mm too small so I can't get the grant....

I'm insulating the boiler. :wink:

[/size]

I don't think that tungsten lining will make any difference to the heat losses.
Why?
... Remember although Tungsten transfers 2/3 that of the alloy. What is forgotten is for the ratio to make any sense; it is a requirement to standardise the thicknesses.
Ie at a guess the tungsten liner would be only 1/16 of the thickness of the alloy:
so the True resistance weightings would be (1/16 x 3/2)tungsten + 15/16 x1)machined ally : 16/16 standard ally

(ie) resistance to heat loss =( 3/32 +30/32) : 1

or 33/32 : 1 .... Conductivity is 32/33 or 97% of heat still transferred!

Ceramic paints etc are probably about 1/400 conductivity of aluminium.so a coating 150 microns thick
Resistance (150/1000,000 x 400 + 1000/1000) :1
or 1.06 :1
So new effective heat transfer is 1/1.06 or 94%

300 microns of 'paint' gives 1.12 or 89%
or 11% saving (of 30% losses to coolant) ... or 3% fuel economy improvement. :cry:
Figures may or may not be accurate

Edit
Forget all else; cast iron is 1/4 of the thermal conductivity of aluminium...

Stainless is actually 1/2 of cast iron!
Theoretically drop losses to coolant to 4%

2446 · « **Reply #63 on:** June 16, 2007, 01:22:51 am »

Mark,
you're adding conductivities, I think you should rather add resistances (1/conductivity), you're also missing the interfaces phenomenons out, which play a great role in heat transfer physics. My physics are so old and dusty I will not make an attempt at an alternative calculation but the math is often not as simple as you're describing.

denis

VW Smokr · « **Reply #64 on:** June 16, 2007, 02:55:40 am »

Quote from: subsonic

If you have your pistons coated, how much will it increase overall length? Has anyone measured? Are we talking .001, .01 or what?

Supposedly about 0.015" thick coating; i.e. your piston would be 0.015" taller.

J.R.

subsonic · « **Reply #65 on:** June 16, 2007, 07:15:34 am »

Thanks

Mark(The Miser)UK · « **Reply #66 on:** June 16, 2007, 10:57:27 am »

Quote from: "2446"

Mark,
you're adding conductivities, I think you should rather add resistances (1/conductivity), you're also missing the interfaces phenomenons out, which play a great role in heat transfer physics. My physics are so old and dusty I will not make an attempt at an alternative calculation but the math is often not as simple as you're describing.

denis

Good name that Denis (my son's name

) I was attempting to do what you said but it was late [1.30am] :roll: parallel circuit type stuff.

As I write I am looking down at the rubbish that I wrote. If tungsten passes only 2/3 that of ally isn't this a 'standardised' emissivity figure?
So it looks like I then used 3/2 as a resistance and then gave it a 1/16 relative thickness Then added it to 15/16 of the ally [1/16 machined out] that I've standardised to 1...

With the interfaces I've assumed that aluminium on its own interfaced with the gasses is the same as the tungsten surface (especially after 'sooting on' ) I made no allowance for the tungsten to aluminium interface which would probably help the resistance figures.

quote
"True resistance weightings would be (1/16 x 3/2)tungsten + 15/16 x1)machined ally : 16/16 standard ally "

It is all very confusing (and I like maths :lol: )
Figures could beway off anyway Heads are an alloy and not pure aluminium. That figure varies too and I'm assuming somewhere between 200 and 400 w /m^2 deg K cast iron is about 50 to 60 W... Stainless is actually 1/3 of cast iron! not that a head could be made in that...

Denis get a pen out and give it a go... It's good for the grey matter...

2446 · « **Reply #67 on:** June 16, 2007, 11:50:32 am »

Quote from: Mark(The Miser)UK

Denis get a pen out and give it a go... It's good for the grey matter...

It probably is, but right now my written resources are buried deep somewhere in my "archives". When I'm done buying diesel and engine books I'll be buying materials book to get back into the business I was doing at school. anyway I will give you a hint. An idea that might make sense and realistically approach real world physics would be to consider the interface surfaces only. You could compare the surfacic conductivity/resistance of the combustion gases through ally (1 interface) and combustion gases through thermal barrier thin coat (1 interface) + thin coat (1 medium) + coating through ally (1 interface)

the4ork · « **Reply #68 on:** October 28, 2007, 03:42:43 pm »

all i want to know is...

i plan on ceramic coating the piston tops, combustion chamber and valve faces only (none of this pre-cup pre chamber crap)

also im getting the skirts friction coated and the bottoms of the pistons are getting a heat dispersant coating

now im running an N/A diesel with a .60 t3 .48ar turbo, so i should be able to push some good boost ~25psi or so... with the giles pump so i should see quite a bit more rpm over stock...

now i'd like to get the ceramic coating just to reduce the added heat from the boost, less stress on the engine components, especially since i dont have oil squirters, hence the piston coatings...

if its a problem of not enough heat ine the combustion chamber after everything has been coated then why not just ditch the intercooler? that should heat things up quite a bit

subsonic · « **Reply #69 on:** October 28, 2007, 06:29:53 pm »

--------------------------------------------------------------------------------
I have a brand new AAZ head. I am planning on having some ceramic coating done.
I do not intend to coat the prechamber or the iconel inserts, nor the intake tract. Exhaust valve and exhaust tract, yes. Perhaps also the face of the intake valve to help prevent heat soak. I understand the heat benefit of uncoated prechamber inserts.

My question is about the value of coatings on the faces of the cyl. head that are exposed to the combustion chamber. Dave had mentioned he coated the entire head deck. Specificly, I am wondering if the heat blocking properties would improve the combustion / burn by keeping more heat in the cyl, and out of the head. By doing this, would this also help prevent the cracks from forming between the valves? If the coating did help keep heat out of the head and allowed more heat to be applied to "work" instead of loss, would this create a effiency that would translate in to the possibility of quicker boost?

Thoughts?

the4ork · « **Reply #70 on:** October 28, 2007, 11:38:27 pm »

Quote from: "libbybapa"

If you are intercooled, then increased boost does not increase heat. Quite the reverse. Increased boost reduces temps. Increased fuel to air increases heat.

Andrew

what i meant was, coat the pistons/combustion chambers so i can run alot of fuel and alot of boost and keep the temps high inside the chamber with the boost/fuel but not have the side effect of toasting a piston due to the fact i have an NA block with no oil squirters

and im talking about running non-intercooled to keep combustion temps higher and more efficient... 25PSI should be about 170 degrees on a .60 t3 compressor

zukgod1 · « **Reply #71 on:** October 29, 2007, 03:00:00 pm »

Quote from: "theory"

Quote from: "libbybapa"
If you are intercooled, then increased boost does not increase heat. Quite the reverse. Increased boost reduces temps. Increased fuel to air increases heat.

Andrew

what i meant was, coat the pistons/combustion chambers so i can run alot of fuel and alot of boost and keep the temps high inside the chamber with the boost/fuel but not have the side effect of toasting a piston due to the fact i have an NA block with no oil squirter's

and I'm talking about running non-intercooled to keep combustion temps higher and more efficient... 25PSI should be about 170 degrees on a .60 t3 compressor

Is that 170 deg in Celsius? I wish the world would just adopt on mean of measurement...

tylernt · « **Reply #72 on:** October 29, 2007, 03:20:13 pm »

I would think that thermal coating the piston tops would be an acceptable alternative to oil squirters, at least for stock fuelling and boost levels. Dunno if anyone has tried it, though, or if it would be up to the challenge of 25PSI and fuelling to match... well, here's your big chance to be a pioneer in the area.

zukgod1 · « **Reply #73 on:** October 29, 2007, 03:29:51 pm »

Quote from: "tylernt"

I would think that thermal coating the piston tops would be an acceptable alternative to oil squirter's, at least for stock fueling and boost levels. Dunno if anyone has tried it, though, or if it would be up to the challenge of 25PSI and fueling to match... well, here's your big chance to be a pioneer in the area.

With stock fueling you can run a NA engine just fine turbo'd.

If you coated piston tops and exhaust parts you could run higher than OE fueling for quite a while i would guess.

I've ran NA engines several times @ 20+ PSI with no intercooler while pulling a small trailer and all was/is fine.

I have a friend on horetex that ran his NA Rabbit like a redheaded stepchild for months and it's demise was cooling related not boost (lost a hose), when disassembled all internals looked new still, piston tops, exhaust valves/seats etc and this was after months of flogging the snot out of it daily.

One would think by coating a TD engine piston tops etc you could run much higher fueling as long as you had the air you would be fine, fine as in no melty the pistons etc and hopefully you would gain some efficiency as in that's seems to be what this post is all about anyway.

Wouldn't it bee cool to be able to get 60mpg out of a TD? I think it's possible without having to drive like there is an egg under your foot with coatings.

Someone do it and tell us what happened will ya ..

zukgod1 · « **Reply #74 on:** October 29, 2007, 03:33:27 pm »

Quote from: "libbybapa"

Quote from: "the4ork"
im talking about running non-intercooled to keep combustion temps higher and more efficient...

please explain that

Andrew

X2

I think the issue would be cyl pressure more than heat.
Our VW's seem to handle the heat just find it's combined with the high cyl pressures that creates the problem.

High heat+ high pressure= no head gasket.