Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by NewbVetteGuy » Sun Nov 05, 2017 7:57 pm

MadBill wrote:
Sat Nov 04, 2017 6:21 pm
CharlieB53 wrote:
Sat Nov 04, 2017 9:20 am
.. I seriously doubt that any insulation could function as a one-way heat valve, allowing the piston to accumulate temps and melt without other contributing factors causing elevated combustion temps...
A heat diode! The ramifications are huge... :-k
I feel like I remember something along these lines announced by Toyota in the past year or two.

Toyota Thermo Swing Wall Insulation Technology (TSWIN3).
http://newsroom.toyota.co.jp/en/detail/8348091
https://www.youtube.com/watch?v=y_QTFp1XDdE


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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by NewbVetteGuy » Sun Nov 05, 2017 10:58 pm

I thought in the thread about the new version of Dynomation that it now can account for coated chambers and pistons; It would be interesting if someone could model some typical 400-500hp street combo with and without the coating option enabled and then go back to the non-coated version and bump the compression up until the post-coating hp/torque roughly matches and look at the curves between the lower CR with coatings version and the higher CR, no coatings version.

I'd be pretty shocked if they didn't look really similar/ identical.


My understanding is that combustion pressure & temperature are near equivalents; the old guidelines for "safe" CRs for aluminum vs. iron heads and that iron heads make more power at the same CR as aluminum heads; all about pressure-temperature.

Why can turbo chargers and superchargers increase the PRESSURE in the cylinder beyond what an NA motor can when detonation is introduced as a function of temperature? -It's because the turbos and super chargers are doing the compression outside of the cylinder and can therefore cool the charge with intercoolers- keeping temps down, which are inducing detonation. Same reason water / water+meth injection keeps detonation at bay, right?


I can't see how thermal barriers, which increase combustion chamber temps, aren't a VERY near equivalent to a static CR increase.

Even the earlier comments in this thread: "thermal barriers make more power, if you richen the mixture so you can keep timing the same" --yea, you're essentially increasing the temp-pressure / CR equivalent and you need the enrichment for the cooling effect to fight off detonation. "Fuel Injection" instead of water or meth injection.


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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by ptuomov » Mon Nov 06, 2017 8:54 am

I think there are a couple of differences.

First, in terms of the efficiency, I think one thing that also matters is the expansion ratio. I don't think the thermal barrier coating does anything to the expansion ratio.

Second, based on my thinking, higher compression ratio makes the charge as hot or hotter at every stage of the compression stroke. The thermal barrier coating should by my theory put less heat into the charge early in the compression stroke and keep more of it in the charge later in the compression stroke.

Thinking out loud, I think that understanding the costs and benefits first for diesel engines would be helpful, as those aren't really knock limited. Once one understands the diesel engine well, then one can introduce the impact of knock constraint and the end-gas temperature to the analysis. Along the lines of this paper: http://papers.sae.org/2010-32-0090/
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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by hoffman900 » Mon Nov 06, 2017 8:55 am

It seems to me, that there is way more to be had in piston oil jet design than coating of the chambers. This has been the trend in top level race engines.
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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by ptuomov » Mon Nov 06, 2017 9:00 am

hoffman900 wrote:
Mon Nov 06, 2017 8:55 am
It seems to me, that there is way more to be had in piston oil jet design than coating of the chambers. This has been the trend in top level race engines.
Isn't that the opposite of TBC from combustion perspective? TBC keeps heat in the charge after gas temperature has increased above the chamber wall temperature, piston oil squirter takes heat out of the piston and thus indirectly out of the charge?

The question that this will ultimately boil down to in my opinion is which one if better with a knock limited fuel: Is one better off using the chamber walls to cool the end gas and increasing compression (and thus expansion) ratio or not using the chamber walls to cool the end gas and reducing compression?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by hoffman900 » Mon Nov 06, 2017 9:31 am

Oil squirters are about making the piston being able to handle the stresses of combustion. The more stable the piston, the more table the ring pack and the more optimal the timing can be.

Check this out:
www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_08e.pdf

By changing the oil jet, with the same volume of oil, they were able to get back almost 10hp they loss due to ignition timing retardation.

and also look at the effort on the Ford RY45:
www.engineprofessional.com/TB/EPQ115_22-42.pd

Short of going to an "aluminum metal matrix composite" which, has pretty much been a pipe dream in the racing world, 1) due to logistics / costs 2) rules.
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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by pamotorman » Mon Nov 06, 2017 10:06 am

since the engine is a heat pump the more heat retained in the chamber the more HP. this is the reason you need .5 more CR to get the same HP with aluminum heads vs CI because more heat is transferred into the water jacket with aluminum heads. this is the reason to coat the chamber to prevent the heat loss thru the heads

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by ptuomov » Mon Nov 06, 2017 10:14 am

hoffman900 wrote:
Mon Nov 06, 2017 9:31 am
Oil squirters are about making the piston being able to handle the stresses of combustion. The more stable the piston, the more table the ring pack and the more optimal the timing can be.

Check this out:
www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_08e.pdf

By changing the oil jet, with the same volume of oil, they were able to get back almost 10hp they loss due to ignition timing retardation.

and also look at the effort on the Ford RY45:
www.engineprofessional.com/TB/EPQ115_22-42.pd

Short of going to an "aluminum metal matrix composite" which, has pretty much been a pipe dream in the racing world, 1) due to logistics / costs 2) rules.
Interesting.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by ptuomov » Mon Nov 06, 2017 10:15 am

pamotorman wrote:
Mon Nov 06, 2017 10:06 am
since the engine is a heat pump the more heat retained in the chamber the more HP. this is the reason you need .5 more CR to get the same HP with aluminum heads vs CI because more heat is transferred into the water jacket with aluminum heads. this is the reason to coat the chamber to prevent the heat loss thru the heads
That's how it works if you're not knock limited, like with a diesel engine. However, how does it work with a knock-limited engine, say, 93-octane pump gas port-injected spark-ignition engine?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by pamotorman » Mon Nov 06, 2017 10:47 am

ptuomov wrote:
Mon Nov 06, 2017 10:15 am
pamotorman wrote:
Mon Nov 06, 2017 10:06 am
since the engine is a heat pump the more heat retained in the chamber the more HP. this is the reason you need .5 more CR to get the same HP with aluminum heads vs CI because more heat is transferred into the water jacket with aluminum heads. this is the reason to coat the chamber to prevent the heat loss thru the heads
That's how it works if you're not knock limited, like with a diesel engine. However, how does it work with a knock-limited engine, say, 93-octane pump gas port-injected spark-ignition engine?
since you can use a lower CR to get the same HP with coated chamber aluminum heads would that not reduce the tendency for the engine to knock ???

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by ptuomov » Mon Nov 06, 2017 10:59 am

pamotorman wrote:
Mon Nov 06, 2017 10:47 am
ptuomov wrote:
Mon Nov 06, 2017 10:15 am
pamotorman wrote:
Mon Nov 06, 2017 10:06 am
since the engine is a heat pump the more heat retained in the chamber the more HP. this is the reason you need .5 more CR to get the same HP with aluminum heads vs CI because more heat is transferred into the water jacket with aluminum heads. this is the reason to coat the chamber to prevent the heat loss thru the heads
That's how it works if you're not knock limited, like with a diesel engine. However, how does it work with a knock-limited engine, say, 93-octane pump gas port-injected spark-ignition engine?
since you can use a lower CR to get the same HP with coated chamber aluminum heads would that not reduce the tendency for the engine to knock ???
I don't know.

Holding the volumetric efficiency and exhaust valve opening point constant, you'll on the one hand get a higher thermal efficiency from keeping more heat in the chamber, but on the other hand you'll get lower thermal efficiency from lower expansion ratio. So I don't know that in net adding coatings and reducing compression ratio will make more power in a knock-limited setting.

My intuition (not to be confused with fact or experience) tells me that, maybe the coatings help if the starting compression ratio is very high to begin with (and thus the efficiency isn't very responsive to small changes in expansion ratio). If the starting compression ratio is low because the fuel is low octane, then I'd guess that it's more likely that you lose more from lowering the compression ratio than what you gain from keeping the heat inside the chamber. But that's just a guess.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by pamotorman » Mon Nov 06, 2017 11:02 am

hoffman900 wrote:
Mon Nov 06, 2017 9:31 am
Oil squirters are about making the piston being able to handle the stresses of combustion. The more stable the piston, the more table the ring pack and the more optimal the timing can be.

Check this out:
www.f1-forecast.com/pdf/F1-Files/Honda/F1-SP2_08e.pdf

By changing the oil jet, with the same volume of oil, they were able to get back almost 10hp they loss due to ignition timing retardation.

and also look at the effort on the Ford RY45:
www.engineprofessional.com/TB/EPQ115_22-42.pd

Short of going to an "aluminum metal matrix composite" which, has pretty much been a pipe dream in the racing world, 1) due to logistics / costs 2) rules.
the piston oilers would allow the piston to maintain the crown a constant temp which should stabilize the HP output.

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by NewbVetteGuy » Mon Nov 06, 2017 1:41 pm

pamotorman wrote:
Mon Nov 06, 2017 10:47 am
ptuomov wrote:
Mon Nov 06, 2017 10:15 am
pamotorman wrote:
Mon Nov 06, 2017 10:06 am
since the engine is a heat pump the more heat retained in the chamber the more HP. this is the reason you need .5 more CR to get the same HP with aluminum heads vs CI because more heat is transferred into the water jacket with aluminum heads. this is the reason to coat the chamber to prevent the heat loss thru the heads
That's how it works if you're not knock limited, like with a diesel engine. However, how does it work with a knock-limited engine, say, 93-octane pump gas port-injected spark-ignition engine?
since you can use a lower CR to get the same HP with coated chamber aluminum heads would that not reduce the tendency for the engine to knock ???
My short answer would be "no"; my long answer is the rest of the post below.


What actually makes an engine knock / fuel to pre-detonate? Is it the static CR, the cylinder pressures, or the temperature?

My understanding is that it is the TEMPERATURE in the combustion chamber that causes the fuel to pre-detonate / combust from heat alone, without a spark; CR is just a very rough INDICATOR / approximator of what your combustion temperature is going to be.

A lower CR coated chamber should have the same tendency to knock at the same temperature as an uncoated chamber of higher CR, in my understanding.



Example: Let's say we have a fuel with an auto-combustion temperature of 250 degrees Celcius at stochiametric AFR. This scenario represent my understanding. We run this fuel in 4 identical engines with the only difference being whether the head is iron vs. aluminum and whether it's coated or not.

#1: Iron head with a 9.5:1 compression ratio reaches 250 degrees Celcius just a couple of crank rotation degrees prior to the spark igniting the mixture; we have pre-ignition and need to remove a couple degrees of timing to avoid pre-ignition at current temps (or drop the incoming air temp or coolant temp)

#2: Aluminum head with 10:1 compression ratio reaches 250 degrees Celcius just a couple of crank rotation degrees prior to the spark igniting the mixture; we have pre-ignition and need to remove a couple degrees of timing to avoid pre-ignition at current temps (or drop the incoming air temp or coolant temp) -identical situation to #1 despite different CR and materials as it's the combustion temperature of the air-fuel mixture that matters and determines when pre-ignition occurs

#3: Aluminum head with coated chambers with 9.7:1 compression ratio reaches 250 degrees Celcius just a couple of crank rotation degrees prior to the spark igniting the mixture; we have pre-ignition and need to remove a couple of degrees of timing to avoid pre-ignition at current temps (or drop the incoming air temp or coolant temp) -identical situation to #1 & #2 despite different CR and materials/coatings as it's the combustion temperature of the air-fuel mixture that matters and determines when pre-ignition occurs

#4: Iron head also coated (crazy I know) with a 9.5:1 compression ratio reaches 250 degrees Celcius MANY crank degrees prior to the spark igniting the mixture; we have pre-ignition and need to remove a LOT of degrees of timing to avoid pre-ignition at current temps (or drop the incoming air temp or coolant temp, or lower CR or get rid of the coating, or retard the cam, or....) -near identical situation but the max temp threshold is reached sooner so we need to pull more timing to prevent the temps goign over our threshold



Assumption: Temperature is the cause of pre-ignition / detonation of a given fuel; CR, DCR, all the other indicators have rough coorelation to pre-ignition /detonation

Or to say it another way: the temperature of the fuel being raised beyond the point at which the fuel spontaneously combusts is the CAUSATION of pre-ignition; the other factors are merely COORELATION to what we should actually care about.

(Thermal barrier coatings put more heat into the combustion chambers and this attribute makes pre-ignition / detonation more likely, BUT thermal barrier coatings create more even temps, reducing hot-spots and this attribute helps to reduce the likelihood of pre-ignition. If your pre-ignition was because of a hot-spot, thermal barrier coatings might help; if it's full-on detonation / spontaneous combustion of the air fuel mixture, thermal barrier coastings should make it worse.)

Unless we're talking about a magical unicorn "heat diode" coating and then I got nothing...



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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by pamotorman » Mon Nov 06, 2017 2:24 pm

I would think the coatings would even out the heat and would prevent hot spots that would cause the problem.

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Re: Chamber & Piston Thermal Barrier: CR Improvement Equivalent?

Post by MadBill » Mon Nov 06, 2017 2:49 pm

There is much to dispute in your premise, e.g., how can retarding the spark help if the fuel pre-ignites prior to the spark? Not speaking to your overall premise though, but just to correct a few relevant misstated terms:

o Pre-ignition is combustion initiated other than by the spark, prior to the spark.
o Compression heat is not capable of initiating combustion in a spark-ignited engine with any normal fuel; it requires something like a glowing protruding head gasket edge, loose and thus red-hot spark plug, etc.
o Detonation is the explosion of a portion of the mixture after the spark but ahead of the arrival of the normal combustion flame front at the affected region.
o There is no such thing as pre-detonation.
Last edited by MadBill on Mon Nov 06, 2017 3:03 pm, edited 2 times in total.
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