VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: JetPo on May 06, 2007, 02:08:19 pm
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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
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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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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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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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Do you think you could prevent the cracks between the valves on the head if you ceramic coated in that area?
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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...
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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
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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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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: ).
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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?
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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.
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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?
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there was talk previously about using zirconium oxide coating... i think that might have a good chance at working...
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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.
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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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theoretically if you can keep 100% of the heat inside the chamber it would be extremely efficient. but that's kind of impossible.
It's a ceramic head then...
And an electric heater for the driver...
A coil round the exhaust would suffice I think
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but you can't reach 100% efficiency with ceramic can you? rather you need something that actually reflects the heat.
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Some coaters dual coat, first an insulating coat, then a heat reflective coat.
Re not coating the pre-cups, I respect the experience of those that have done it and don't advise it, but it cannot be correct to say it keeps heat out. Correct, it keeps heat out of the pre-cup - BUT it retains the heat inside the air within the pre cup where it is wanted.
The pre-cup heats by cooling down the air inside it, if a thermal barrier is placed over it as a coating it will no longer cool down the air inside it so well - this is the reason why a lot of people have used it in low compression diesel engines (search on the web) as it effectively restores some of the heat lost when dropping CR.
I would argue that other than a small thermal loss, it won't improve the burn IF the air was already hot enough to ignite the diesel anyhow, pre coating. More gain would be seen on an engine of lower CR or some other issue causing lower air temp in the pre cup.
If any negative effects were seen, something must be wrong. All things being equal, it's a good thing to do as reduces thermal stress on the head and pre cup, improves efficiency and sustains the air temperature in the pre-cup better.
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i'd like to agree with you that putting a heat barrier/reflective coating in the pre chamber makes all the sense in the world.
Tragically, it appears we have emperical evidence, from some one that has invested alot of time and money into experimentation, that says otherwise.
I guess we need to figure out why it doesen't work, and attack the problem from that angle.
Apearently, a swirl chamber (or something else) at 198 F aids in combustion. So what ever the air temperature rises to, from compression, it needs another 198 degrees to do something to succesfully complete the combustion process with the equipment we have now.
Are the swirl chamber walls mearly heating the air a few degrees more in the phemto second that the air is in contact with it?
Is the air being pre heated in the intake tract?
Does a hot injector give a better spray pattern?
The TDi engine seams to work just fine at a much lower CR. The gosh darn things even need glow plugs in the coolant to keep the driver and passengers alive in frigid climates. Why can this engine do this?
Higher injection pressure?
Different combustion chamber?
Any thing else? pilot injection?
Do we need a TDi pump to run an IDI motor at the same CR as the TDi?
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but you can't reach 100% efficiency with ceramic can you? rather you need something that actually reflects the heat.
Silver coat the ceramic?
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I wonder if its the temperature of the injector. The ceramic coating insulates the injector, and there is no water jacket in the area.
Any one have one of those opticle temp sensors? Try aiming at a warmed up injector boss, and then about an inch away where there is water jacket.
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i'd like to agree with you that putting a heat barrier/reflective coating in the pre chamber makes all the sense in the world.
Tragically, it appears we have emperical evidence, from some one that has invested alot of time and money into experimentation, that says otherwise.
I guess we need to figure out why it doesen't work, and attack the problem from that angle.
Apearently, a swirl chamber (or something else) at 198 F aids in combustion. So what ever the air temperature rises to, from compression, it needs another 198 degrees to do something to succesfully complete the combustion process with the equipment we have now.
Are the swirl chamber walls mearly heating the air a few degrees more in the phemto second that the air is in contact with it?
Is the air being pre heated in the intake tract?
Does a hot injector give a better spray pattern?
The TDi engine seams to work just fine at a much lower CR. The gosh darn things even need glow plugs in the coolant to keep the driver and passengers alive in frigid climates. Why can this engine do this?
Higher injection pressure?
Different combustion chamber?
Any thing else? pilot injection?
Do we need a TDi pump to run an IDI motor at the same CR as the TDi?
Apparently 'over swirling' is possible as it encourages more gas to be cooled from the chamber sides and reduces the burn quality.The VW swirl chamber is based on a Ricardo patent AFAIK from at least 60 years ago and in the 50's was regarded as one of the best of the IDI's efficiency wise.
Surely what makes an engine do work, is not the flames from the fuel but it is just a matter of heat... Extra heat expanding a particular volume of air. So arguably an infra red lightbulb could do the same thing.
Initially I couldn't see how the swirl chamber could heat the air; but I guess it can whilst air is cooler than the chamber. But what is the temp of the chamber walls? what with the coolant trying to suck the heat out. Heat will of course go back out of the air as the compressing takes it beyond wall temp on its way up to 600 deg C. Fuel burning only raises it up another 300 deg C or so,
Where did the rapidly cooling walls get their heat from? Obviously it came from the previous 4 strokes or at least the power stroke. Thus in the continual process the present power stroke will be 'robbed' of heat for the next cycle.
Ceramic coating will reduce heat loss so the same coolant will be able to remove more of the heat that does pass (2/3 of non ceramic setup) and so there will be less heat returning to the air from the chamber walls but with a 1/3 more heat staying in the chamber that doesn't seem a problem. If peak air temp in the chamber is higher in the ceramic case then turning the fuel down should result in similar temperatures to original setup.
Reducing radiator size could help; or using pure antifreeze (which although it boils at a higher temperature actually has a lower SHC than water).
I don't like the idea of higher and higher injection pressures just seems like extra energy wasted and extra strain on the pump. Neccesary perhaps for absolute power but for economy not required. Somewhere I have a book that suggests that over atomisation can lead to poor burning. Perhaps its linked to times of lower injection volume where the droplets can get lost in the excess of air and slow the flame front...
However efficient these TDI engines appear; I'm not getting the vibes that they will be long life engines.,,,
Rant off
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No rant detected. I'd really like to cermaic coat my prechambers if there is a noticable, measureable bennifit.
we can pontificate all day long about how it should be bennificial, but we have a member of this fine community that has gone where no man has gone befor, and actually ceramic coated everything but his socks. The results are that ceramic coating the swirchambers of the VW IDI diesel does not work.
I am inclined to trust Dave's observations that ceramic coating the swirl chambers on the IDI VW Diesel engine results in lower performance.
From his varied posts on the subject:
it does not result in better fuel milage
it does not improve cold starts
on a stricly performance only VW idi diesel, it gives no bennifit, but actually reduces performance.
He has no motivation to report an untruth. I don't suspect he used the wrong coating.
I could write a couple of paragraphs on why ceramic coating the swirl chambers should work as well. And with my plans to build a low compression VW 1.6TD engine, I really would like to ceramic coat the swirl chambers too. I contacted Swain Technologies (http://www.swaintech.com/), sent them pictures, talked at lenght over the phone about it, and although they have never done a diesel swirl chamber befor, they felt it was a do-able process and should yeild noticeable bennificial results.
But with Dave's experimental results, I am inclined to begin my build without ceramic coating the prechambers. Its not an expense thing, its a performance thing. I can't drink the coolaid and jump on a band wagen thats heading no where.
I honestly suspect that the ceramic coating is not causing the bad results because the wall of the swirl chamber are at a lower temperature. I suspect that the cooler wall of the swirl chambers are causing an unintended consequince to something else, and thats causing the poor performance. No good deed goes unpunished.
If VW screwed up the swirl chamber design and they have to be at 190 F to run right, we're screwed.
If there is something else whe can fix, or modify, i'm in like flin for cermamic coating the swirl chambers.
Does any one have one of those point and shoot temperature measurement thingies?
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Tragically, it appears we have emperical evidence, from some one that has invested alot of time and money into experimentation, that says otherwise.
Maybe the member can post a bit more info, wasn't it more that he couldn't measure the difference - which if only looking at changing the coating on the pre cup without changing anything else, unless measuring mpg carefully over 2,000 miles would be hard to get an accurate figure on - given that a FULL engine treatment of multiple coatings gives UP TO 5%?
I guess we need to figure out why it doesen't work, and attack the problem from that angle.
Can't argue with that ;-)
Apearently, a swirl chamber (or something else) at 198 F aids in combustion. So what ever the air temperature rises to, from compression, it needs another 198 degrees to do something to succesfully complete the combustion process with the equipment we have now.
This can't be so, on full compression the air is way higher temperature, a chamber round it at a 'cool' 198 will do nowt but cool the air down. The chamber only gets hot via ROBBING the air of temperature. Put 10 metal spoons in your cup of tea, leave them there for a minute. All the spoons are now warm. But your tea is now also warm, not hot. The heat travels to something cooler - the warm spoons don't warm the tea up - they sap the heat of the tea to keep them warm. Put your tea in an insulated chamber (flask) and it stays hot all day. Compared to combustion and compression pressures, a pre-cup is always cold - so I cannot see in any possible way or form that it's 'heating' the charge up! If bad running resulted, or no improvement, either the issue was caused by something else (changing too many things at once) or too small to measure the improvement, or a poor coating, or something we don't yet understand.
Are the swirl chamber walls mearly heating the air a few degrees more in the phemto second that the air is in contact with it?
And where would they get this heat from, unless it's taken OUT of the compression/combustion air - thus reducing pressure/temperature in the cylinder?
Does a hot injector give a better spray pattern?
Now that is a good question, quite possibly - it is done via heating the fuel on oil engines as without it they can't spray good enough. Seeing as how with decent compression a car will start fine on a cold engine/injectors I think the answer is 'no' though, perhaps there is some small efficiency to gain by heating them - this would need practical testing. Most people suggest they are 'hot enough' in the head but one could feed them with diesel at 100c pretty easily. I don't think it's worth bothering with this line much though, my 'seat of pants' conclusion.
The TDi engine seams to work just fine at a much lower CR. The gosh darn things even need glow plugs in the coolant to keep the driver and passengers alive in frigid climates. Why can this engine do this?
My argument on the other thread and generally agreed on in techincal papers is they don't have the compression and friction issues an IDI has with the pumping losses in and out of the pre-cup. This results in the increased efficiency. The increased injector pressure and different spray putting the energy in via the fuel rather than the swirling air to allow good fuel/air mixing enables them to run without a pre cup/swirl and at the lower compression ratios. I think very high injection pressures on the smaller volume of a pre-cup may result in diesel hitting the walls (bad for mixing/power/engine life) and thus better suited to the lager 'bowl' in a DI piston. Pilot injection is a way of managing noise and emissions on a di, as well as reducing the strain on the bearings as the compressed and ignited charge isn't released in a 'jet' from the pre-cup 'slowly' like on a idi, but explodes at once over the piston directly - the idi's are kinder from a shock wave/bearing load point of view at the expense of some efficiency (typically 10-20% compared to a di).
Do we need a TDi pump to run an IDI motor at the same CR as the TDi?
I haven't worked out what would happen. Would be interesting. I think there would be issues with the space being too small for the spray pattern produced by the di pressure/injector. IF one enlarged the pre-cup to the size of a di bowl, maybe this would work (this would also give the same di compression ratio). One could then perhaps drill a big entry/exit hole to the pre cup and make pumping in/out easier and approach the efficiency of a DI. Of course you would also have the noise and loading issues of a DI if you did that, presuming it would run and you are not trying to fire the fuel through the alloy of the head or something ;-)
Seems like a good experiment though? Anyone taken the pre-cups completely out and seen if the engines will run? Lol. We need a re-usable copper or metal head gasket for an experimental engine! The cost of new bolts and gaskets puts me off tinkering more than anything else.
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While not a great insulator, tungsten carbide transfers 2/3 the heat of steel, so TC liners might help improve efficiency. Don't know what the cost would be though. While looking at TC stuff, I ran across this interesting diesel. A coal/water slurry diesel "Over 200 operating cylinder hours were run on critical wearing engine parts. The main components tested included cylinder liners, piston rings, and fuel injector nozzles for coal/water slurry fueled operation. The liners had no visible indication of scoring nor major wear steps found on their tungsten carbide coating. While the tungsten carbide coating on the rings showed good wear resistance, some visual evidence suggests adhesive wear mode was present. Tungsten carbide coated rings running against tungsten carbide coated liners in GE 7FDL engines exhibit wear rates which suggest an approximate 500 to 750 hour life. Injector nozzle orifice materials evaluated were diamond compacts, chemical vapor deposited diamond tubes, and thermally stabilized diamond. Based upon a total of 500 cylinder hours of engine operation (including single-cylinder combustion tests), diamond compact was determined to be the preferred orifice material."
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Here is an old post on Dave's experience with ceramic coating:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=7017&highlight=
The results appear to be measureably WORSE. Worse milage, worse cold starts, and less power.
I can say it should work too, but looks like Dave has done some work in this area and really broke off his pick.
i'm still wondering if the ceramic coating is the cause of some unintended consequence which is the real problem.
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935 racer... What colour was the ceramic coating?
If you got a 5% gain overall was that by coating everything? If so then by implication a greater gain could have been achieved by coating the 'right' part.
A larger exhaust gave me a 30% gain.
One final point you said coating affected performance and mpg; but then your goal has been to up the power and speed hasn't it? ... Maybe ceramics help the light footed 'econo-miser' :lol:
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Ok I am going to attempt to answer all these questions. But first off I think everyone should ask themselves, why are we trying to coat the pre chambers? Is there a problem with the way they are stock? What is the ultimate advantage you are hoping for in ceramic coating the chambers.
Greg123: Yes you are right it keeps the heat out of the pre cup its self, and than reflects the heat into the air, which is of course where the combustion occurs. I also agree that this means the pre cup is cooling the air to a certain extent, but I believe this is only on a stone cold engine, once the engine is up to operating temp I believe the purpose of the pre cup is store heat for the combustion process, one of the reasons why I believe they chose iconel for the pre chamber, instead of just making the pre cup part of the casting and keeping it Al. I could be wrong but based on my experiences that was my conclusion.
saurkraut: where does this 198degree firgure come from? I assume this is celcius?
greg123: To give more info on my tests I have done this a few times times, twice of which NOTHING else was done to the engines besides removing the head, CCing the precups (and once the chambers) and reinstalling with a new HG, I set the timing back to where it was as well. The third time I tried I also lapped the valves, and CC'd the cups and chambers.
Andrew: I tried coating the blue area you mentioned twice, no noticeable gain. And as I mentioned earlier coating the pre cup alone seemed to smoke more, I needed to advance the pump.
Mark: the coating is a silver color.
Trust me I wanted some sort of positive benefit from this, but I just had no luck. I've tried ceramic coating damn near everything on these heads, and anything where there is heat for that matter, the local ceramic coater and I are really good friends and I send as much business to him as I can but this was one thing I tried that just didn't work.
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i think i'm understanding a bit more about this now.. since my car smokes more now with the lower temp t-stat than it did with the much higher temp t-stat...
and the problem could also be magnified if you're using an intercooler to cool the charge air...
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Thanks for responding so well Dave.
Myself, I'm lookng for Samepowerlessfuelmorempg... Pepsi :mrgreen:
Interestingly; how was the coolant temperature affected with everything ceramikked?
Perhaps if the coolant temp dropped then the way to go would be to shield part of the radiator. :?:
As silver and white coatings I believe behave very similarly; I wonder if going against intuition and using a black ceramic would produce something special :idea:
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So I wonder how coating the head behind the pre-cups, just where the sides of them are, or the back side of the pre-cups would affect operation?
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"saurkraut: where does this 198degree firgure come from? I assume this is celcius?"
Water Jacket temp. For purposes bringing the discusion back to facts, i pulled a kind of known number out of the air. i assume the outside of the swirl chambers are close to this temp. The inside, who knows?
We probably should have a note in the FAQ on this subject
Oh, by the way,did you ceramic coat your sox too?
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Same foot. Only difference is the shifter is on the wrong side.
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TDI engines have excellent life with less head issues than idi (cracking etc). They have been used in lorries for years and the vw tdi as well as other older engines (Rover Perkins Prima 2.0di diesel from 1989 on) that used di have had excellent reliability. They often have a useful side effect of contaminating the oil far less as combustion is kept central making for better oil life/less wear. I took a Montego up to 225k miles with no descernable wear anywhere, when I scrapped the vehicle due to rottern body.
Anyhow that's an aside a little, there is NO WAY in any circumstances that the pre-cup walls can heat the air. Energy ALWAYS travels from Hot > Cold, thus the colder walls will always warm up by heat removed from the air inside. Injector heating isn't an issue as it's screwed into the head and the ceramic coating won't affect that. Normally so much heat escapes into the head that water cooling is needed to avoid warping etc, even with the ceramic coating the engine will still reach temperature so heat directed to the injector should be much the same. Thermostat opening should be less as there should be less need to use the radiator due to heat kept in the chamber more. Even if one presumes that the chamber can heat the air before ignition (even though it's hot enough to self ignite diesel, which is way hotter than the temperature of a head surface) that heat would COME from the temperature of the burn, which is the same thing as robbing peter to pay paul. I think we need to get away from any idea that the pre-comp chamber can in any way heat the air in it due to a) it would need to be 700+c or thereabouts, which I put to the group it isn't.
b) even if conditions exist where it was proven that it is hotter than the air/combustion in the chamber, it's 'heat' isn't free, it's taken from combustion temperature. There are no glow plugs stuffed all over the head heating it, the heat is sapped out of heat that should be contributing to combustion pressure - ie power and efficiency!
I have been on a top fuel board where all the top teams use ceramic coating to increase power. another way of looking at it is to say make the same power, but with slightly less fuel. I can't fault the theory, the quality and efficiency of coatings and the number of coatings etc would make a difference, as would over swirling (if that's possible?) due to higher temp sustained in the chamber. I'm certainly convinced there are gains and it's a 'good thing' to coat, how much gains and if it's worth it is another matter. Subaru and top fuel engine builders, among others, think it is. Very little in the motor world is devoted to serious persuit of mpg but I feel it could have application there.
There has to be other longevity benifits, particularly in protecting the head from heat and the crown of the piston, those of you building heavy turbo motors take note ;-)
Apparently 'over swirling' is possible as it encourages more gas to be cooled from the chamber sides and reduces the burn quality.The VW swirl chamber is based on a Ricardo patent AFAIK from at least 60 years ago and in the 50's was regarded as one of the best of the IDI's efficiency wise.
Surely what makes an engine do work, is not the flames from the fuel but it is just a matter of heat... Extra heat expanding a particular volume of air. So arguably an infra red lightbulb could do the same thing.
Initially I couldn't see how the swirl chamber could heat the air; but I guess it can whilst air is cooler than the chamber. But what is the temp of the chamber walls? what with the coolant trying to suck the heat out. Heat will of course go back out of the air as the compressing takes it beyond wall temp on its way up to 600 deg C. Fuel burning only raises it up another 300 deg C or so,
Where did the rapidly cooling walls get their heat from? Obviously it came from the previous 4 strokes or at least the power stroke. Thus in the continual process the present power stroke will be 'robbed' of heat for the next cycle.
Ceramic coating will reduce heat loss so the same coolant will be able to remove more of the heat that does pass (2/3 of non ceramic setup) and so there will be less heat returning to the air from the chamber walls but with a 1/3 more heat staying in the chamber that doesn't seem a problem. If peak air temp in the chamber is higher in the ceramic case then turning the fuel down should result in similar temperatures to original setup.
Reducing radiator size could help; or using pure antifreeze (which although it boils at a higher temperature actually has a lower SHC than water).
I don't like the idea of higher and higher injection pressures just seems like extra energy wasted and extra strain on the pump. Neccesary perhaps for absolute power but for economy not required. Somewhere I have a book that suggests that over atomisation can lead to poor burning. Perhaps its linked to times of lower injection volume where the droplets can get lost in the excess of air and slow the flame front...
However efficient these TDI engines appear; I'm not getting the vibes that they will be long life engines.,,,
Rant off
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So it looks like UK v rotw :wink: + Andrew...
Greg what do you think about black ceramic?
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Anyhow that's an aside a little, there is NO WAY in any circumstances that the pre-cup walls can heat the air. Energy ALWAYS travels from Hot > Cold, thus the colder walls will always warm up by heat removed from the air inside.
Why not? What if the pre-cup walls are(just a guess)350 degrees? They will add heat to the air UNTIL it exceeds that temperature. Now I will admit that won't be for long, but it does add some heat. Plus the warmer the pre-cup is,
the less heat will eventually be lost. Hence me wondering about coating the outer wall of the pre-cup or the head where it contacts the pre-cup.
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well i have an idea...
if we need heat to stay in the pre-cup.. why not just use a metal that absorbs heat like the catalytic converters use... that way it can heat up and store the heat... and the chambers can be ceramic coated to keep the heat in there.
something like this... head + ceramic coated > layer of heat absorbing metal (that can withstand great temperatures...) > precup
lets get some discussion on this!
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I don't know that we have much choice in metals as it not only has to withstand heat, but also be very oxidation resistant at high temps.
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I don't know that we have much choice in metals as it not only has to withstand heat, but also be very oxidation resistant at high temps.
lets go with... Platinum... $$$$$$$$$$
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High temperature paints likely as not have similar heat transfer caracteristics. Could always coat the head/water interface to slow down losses to coolant.
Pre ignition chamber is acting as an averaging mechanism reducing the peak temp and also raising the bottom temp. Is this a good thing or is it just a benefit in extremes of outside temperature?
Black Ceramic anyone :mrgreen:
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I accept that may be possible. May I ask where this heat comes from though? Surely this is a case of heating up your boiler to then pour some hot water on the outside of the boiler, claiming it helps the boiler efficency by heating the boiler up? Insulating the boiler and keeping the heat in the water inside it would result in a far more efficient system.
Why not? What if the pre-cup walls are(just a guess)350 degrees? They will add heat to the air UNTIL it exceeds that temperature. Now I will admit that won't be for long, but it does add some heat.
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I don't think it helps at all as at cranking speed with a cold engine it just sucks heat out, so much so an overly high CR is needed to fire up the thing. Cold cranking starting is the only place where, if hot enough, it *could* help, but obviously it's stone cold and doesn't. All other times it's a heat soak, other than for a small fraction during the initial compression stroke. Bottom line is a hot engine means part of the fuel is uesd to heat the engine up, the more power and more fuel economy for a given amount of fuel can only come from reducing the amount of energy lost via heat to the engine and through the exhaust.
Mark I'm sorry I don't know anything about Black Ceramic - if you do can you share a bit with us? I'm promoting the theory here, how efficient a partial coat would be (ie can one measure the improvement) is another matter! I guess a whole ceramic pre-chamber or similar would be the best way to go, coupled with a ceramic 'topped' piston and ceramic coated everything else. Cylinder bore would be a difficult one, easy to coat but problems with life/rings bedding in etc.
Pre ignition chamber is acting as an averaging mechanism reducing the peak temp and also raising the bottom temp. Is this a good thing or is it just a benefit in extremes of outside temperature?
Black Ceramic anyone :mrgreen:
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I accept that may be possible. May I ask where this heat comes from though? Surely this is a case of heating up your boiler to then pour some hot water on the outside of the boiler, claiming it helps the boiler efficency by heating the boiler up? Insulating the boiler and keeping the heat in the water inside it would result in a far more efficient system.
That was kind of my point in a way. I was thinking that if ceramic coating the pre-cup interior, keeping heat out of it, didn't seem to help, than maybe coating it to keep it from loosing heat as quickly might. I'm insulating the boiler. :wink:
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Bottom line is a hot engine means part of the fuel is uesd to heat the engine up, the more power and more fuel economy for a given amount of fuel can only come from reducing the amount of energy lost via heat to the engine and through the exhaust.
I'm promoting the theory here, how efficient a partial coat would be (ie can one measure the improvement) is another matter! I guess a whole ceramic pre-chamber or similar would be the best way to go, coupled with a ceramic 'topped' piston and ceramic coated everything else. Cylinder bore would be a difficult one, easy to coat but problems with life/rings bedding in etc.
I was looking on the net about tungsten carbide liners, which are used in some engines, along with TC coated rings. Now while not a great insulator, it does state that it transfers 2/3 the heat of steel, meaning 1/3 of what the cylinder normally looses would stay in the system.
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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....
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I'm insulating the boiler. :wink:[/quote]
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This experiment could be likened to a giant engine precup.
http://www.monolithic.com/plan-design/ceramic/index.html
Click on the graph and enlarge by holding 'ctrl' on keyboard and rolling mouse wheel :idea:
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Check out this very long but very interesting article:
http://www.patentstorm.us/patents/5915351-description.html
Maybe the reason a ceramic-coated prechamber had poor results because the timing was not retarded to compensate.
See, I always thought an insulated prechamber would be nothing but good. The poor real-world results may be the result of an unintended variable!
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This has been a great post. Very informative and compelling. However I would hesitate in making the leap w/ the analogy below...
This experiment could be likened to a giant engine precup.
http://www.monolithic.com/plan-design/ceramic/index.html
Click on the graph and enlarge by holding 'ctrl' on keyboard and rolling mouse wheel :idea:
The heat in the article is radiated primarily through the infrared of the electromagnetic spectrum, which sunlight pretty much encompasses, where-as heat gain in a combustion chamber is most likely due from convection and conduction. Thus physical characteristics that have an effect upon wavelength, ie. color are most successful in reflecting heat via radiation and other physical characteristics, though not negligible, are lesser.
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This has been a great post. Very informative and compelling. However I would hesitate in making the leap w/ the analogy below...
This experiment could be likened to a giant engine precup.
http://www.monolithic.com/plan-design/ceramic/index.html
Click on the graph and enlarge by holding 'ctrl' on keyboard and rolling mouse wheel :idea:
The heat in the article is radiated primarily through the infrared of the electromagnetic spectrum, which sunlight pretty much encompasses, where-as heat gain in a combustion chamber is most likely due from convection and conduction. Thus physical characteristics that have an effect upon wavelength, ie. color are most successful in reflecting heat via radiation and other physical characteristics, though not negligible, are lesser.
Sootme'
You could well be right...but then again... the fuel burning in the chamber does produce light. But is it blue like a gasser or yellow like a school bunsen burner with air turned down. Maybe its blue with yellow spots!
Yellow being more like the sun. So does the heat transfer in a diesel mimic the sun more than a gasser? Very interesting point maybe. My mini quartz spark plug for tuning gassers show all the colour changes in a poorly tuned engine.
:idea: Could it be that an engine running rich gets hotter not just because of the extra fuel but because of the increased visible radiation. Could that be why even a diesel can be given extra fuel and then extra air to produce extra power without overheating by keeping the visible radiation down. :idea:
I have a diesel book from some 50 years ago that had a series of high speed photography shots through a quartz view lens that shows the burn sequence. It also shows detonation in a gasser too. Unfortunately picture quality is too lousy to reproduce.
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I have a diesel book from some 50 years ago that had a series of high speed photography shots through a quartz view lens that shows the burn sequence. It also shows detonation in a gasser too. Unfortunately picture quality is too lousy to reproduce.
Interesting.. is this the same spectroscopy in the book as used to determine the presence of elements in measuring corrosion of spark plugs? http://www.ornl.gov/sci/de_materials/documents/ASMEFall04Paper.pdf
No doubt there is heat gain through radiation, for all hot bodies radiate hence the spectroscopy you mention. But I am inclined to say the majority of heat gain is due to convection and conduction due to the proximity of the combustion (unlike the 149,600 km distance to the sun). I stand to be corrected when I said "the heat in the article is radiated primarily..." because our atmosphere does indeed absorb a great deal of the sun's energy and is transferred further through convection, hence the winds and currents. Though within that article the more direct source of heat gain is that through radiation.
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Well either we're in different solar sytems or you should change your name to Soot IN YuR EyE...LOL :mrgreen:
http://en.wikipedia.org/wiki/Astronomical_unit
The millions of miles does make it a rather large swirl chamber!
The book is a thermodynamics book
"Thermodynamics as applied to Heat Engines"
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Visible light doesn't carry much heat. Heat is in the infrared spectrum, so if it would last, I imagine a ceramic with a coating of gold would be the best way to keep heat in. Question is how quickly would it turn black with soot?
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Visible light doesn't carry much heat. Heat is in the infrared spectrum, so if it would last, I imagine a ceramic with a coating of gold would be the best way to keep heat in. Question is how quickly would it turn black with soot?
visible light can actually carry quite a bit of heat... the gold would turn black pretty quick though...
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My bad on the distance... Yeah it would be a massive swirl chamber. Light being energy, all energy equates to heat, even visible, lasers and ultraviolet burn.
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But infrared carries more heat than the shorter wavelengths.
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So would coating the injector heat shields help at all? Would they flex when tightened and wreck the coating?
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So would coating the injector heat shields help at all? Would they flex when tightened and wreck the coating?
Put them in wet? :idea:
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I apologize I don't know if I derail the post more then help but... what if inefficiency in ceramic coating certain areas, ie. the swirl chamber or precups, was not dependent upon thermodynamics but rather aerodynamics. Are the swirl chamber's walls deliberately roughed up to promote turbulence and just the right amount of swirling? Would applying a surface such as ceramic coating actually smooth the wall too much? Likewise turbulent boundaries have a direct effect in heat transfer through convection (see link). wall?http://physics.ust.hk/penger/PRL_v81_987.pdf
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I apologize I don't know if I derail the post more then help but... what if inefficiency in ceramic coating certain areas, ie. the swirl chamber or precups, was not dependent upon thermodynamics but rather aerodynamics. Are the swirl chamber's walls deliberately roughed up to promote turbulence and just the right amount of swirling? Would applying a surface such as ceramic coating actually smooth the wall too much? Likewise turbulent boundaries have a direct effect in heat transfer through convection
Ah yes that is a very good point. Swirl and turbulence is critical or the fuel will not be dispersed among the oxygen properly. That's why you should never polish the intake ports on a gasser cylinder head to a mirror finish. Maybe in order to do a thermal coated prechamber we need to keep the surface rough and retard the timing... maybe change other variables. Hopefully the coating is very thin also, or it may change the geometry of the "throat" and affect the swirl pattern.
I think it'll work we just need to refine the details.
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I apologize I don't know if I derail the post more then help but... what if inefficiency in ceramic coating certain areas, ie. the swirl chamber or precups, was not dependent upon thermodynamics but rather aerodynamics. Are the swirl chamber's walls deliberately roughed up to promote turbulence and just the right amount of swirling? Would applying a surface such as ceramic coating actually smooth the wall too much? Likewise turbulent boundaries have a direct effect in heat transfer through convection (see link). wall?http://physics.ust.hk/penger/PRL_v81_987.pdf
No derailing by your posting; just useful input. :wink:
Doesn't the tangential entrance do a lot of the mixing work.Maybe the roughness helps.
Could just be cost cutting... else exhaust manifold would be polished. :?:
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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.
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If you have your pistons coated, how much will it increase overall length? Has anyone measured? Are we talking .001, .01 or what?
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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:
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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%
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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
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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.
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Thanks
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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.
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"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...
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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)
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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
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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?
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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
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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...
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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. ;)
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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 .. :D
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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.
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I see Andrews point. Keeping the intake tract cool. Not coating it would be kind of like blowing your cooled charge through a heated pipe right before it goes into the combustion chamber. I mean Daves high speed intake manifold is ceramic coated inside and out.
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So the question is : Is the price of coating worth the extra power ?
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Well, if you just ceramic coated the pistons, and did not do any skirt coatings, it would be about 100 bucks. What else could you do for 100 bucks? Rebuild a set of injectors if you have your own pop tester. That would give you a good gain. Perhaps run a cold air intake pipe. I think the pistons would provide the best bang for your buck. Even heat distribution accross the piston crown, less heat soak into the piston. Less heat into the oil from the pistons. The ability to run up to higher operating temps for periods of time with out damaging the piston. Slightly better efficency with heat means more for work, ie turbo spool.
I guess in the 100 dollar range, I think it is the best application of funds for the payback.
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Check out this very long but very interesting article:
http://www.patentstorm.us/patents/5915351-description.html (http://www.patentstorm.us/patents/5915351-description.html)
Gentleman,
I think tylernt has brought an interesting point here, and probably the reason why coating the pre-chamber itself is a really bad idea.
By 935racer experiment and the patent description above, we have theorical and empirical evidence that the coating should go between the surfaces of the pre-chamber that exchange heat with the air and the head itself.
The surfaces of the pre-chamber can be viewed like the regenerator from the Stirling engines, keeping part of the heat for the next cycle: they should store a good amount of heat and deliver it as fast as possible for the next cycle, for good efficiency of the whole combustion process.
I never saw the pre-chamber and don't know if a coating like that is possible, but I see that as a way to reduce losses and really improve efficiency.
Cheers,
Leonardo
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I actually didn't read all of the way through this. I am very interested in the engineering aspect of this as I would like to manufacture precups from ceramic. Here is my take, a vortex is created by combining slow moving low pressure hot air with fast moving high pressure cold air. The two push against each other and move up and around, at the exact same time they attempt to equalize each other passively "movement from one concentration to another" I don't understand how exactly the inderect injection process takes place from injection to combustion "kind of a black box of unknown for me" Hot air comes in injection occurs in a cone like shape, now the air is heated via compression and then cooled by the cooler fuel being injected and the two begin their dance, the air cools more rapidly as the fuel heats up and atomizes and expands into a vapor, the temperature equalizes somwhat between the air and fuel, thermodynamically speaking it happens slowly but to us this is a rapid process. The air fuel mixture from the beginning is doomed somewhat because of the cooling process of the aluminum head and components rapidly absorbing and transporting the heat away. someone once explained to me that the hot air moves quickly and the exhaust gasses move slowly and this is a trait unique to indirect injection. Please correct me if I'm wrong, I also plan to get my engine coated and running a low static comp.
thanks,
Kevin
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Wow! This be a right rave from the grave, I wondered what happened to this one!
I was suprised that the ceramic coating of the alloy cylinder head in the prechambers didn't seem to help efficiency/ power. Didn't some of the japanese idi motors used ceramics for the precups instead of iconel? How well do these magic coatings adhere to the engine components? ???
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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
Maybe off topic, but what about the turbo? Sure the coated pistons will be less likely to melt, but the turbine isn't going to be any happier about being 1500ºF is it? I aways thought the concern about EGTs was primarily for fear of melting the turbo.
I know people have ceramic coated their exhaust manifolds, turbine housings, and downpipes, GeeBee has probably done his entire exhaust, but at some point we approach diminishing returns right?
I just did my piston domes, but I did not run the engine before I did this so I have no control to verify against to determine what kind of gains it produced in terms of power or efficiency.
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I did the exhaust manifold, Both turbo housings & Downpipe on my AAZ
I learned from the thermal protection on my Ti exhaust on my 997TT and my Ti exhaust on my Desmosedici
The TI headers on my Porsche still look great and you can shut down the motor and touch the exhaust and headers after a minute or so..
Lucky I have a buddy with a powder coating shop that also does ceramic, he just adds my stuff to whatever he is running that day..
My wrench goes crazy when he see's my S/S metric or TI hardware for my installs,it seems I powdercoat everything I take off before I reinstall.
Latest was my axle and leaf spring's and followed with S/S U-Bolts for the spring's and new Poly spring inserts and S/S brake lines.
Gee-Bee