Anyone have any experience with ceramic-coated pistons? How much of a horsepower benefit can one expect? Does coating enhance or degrade overall engine reliability?

Are they practical for a driver? Cost-prohibitive for the horsepower gains to be expected?

 

I'm surprised GKull has not seen this or replied to it. I know he used a couple of ceramic coatings and thin dry film lubricant coatings within his new motor. Might want to email him if he doesn't respond.

 

I just saw this post It's the only way to build a motor. Conservative claims of 25 free hp and you can safely add another .5 of compression without Detonation.

I was in a hurry and didn't research it enough. You should do the whole motor. I have a light weight 40ish pound 3.750 crank and it is nitrided & oil repellant treated. My JE pistons I sent to a place and for $225 got the ceramic tops - moly sides - oil repellant bottoms. My Dart heads I didn't go far enoungh I had the chambers and exhaust valves done with ceramic thermal coating. You should after all the porting is done. Have the whole intake and exhaust ports done. I was leary of thermal coating my 2.08 titanium intake valves.

Not really a good picture but you can see the moly sides and white thermal piston top. durring and after stroker crank clearance grinding I had washed the block so many times with soap and water it was getting light rust. So before I slapped it together it was surgically clean!

:smash:

 

The cost is covered by the HP gain in fact it's a bargain. If your already paying $600 for pistons why not pay $800. I can't get my 10.84 C/R motor to ping on 92 octane. I wish that I had believed the coating manufacturers and went with low to mid 11's

The other area to coat with oil repellant is everything under the valve covers and the and the cam valley. Go to any type of car race and talk to any of the top engine builders and everyone of them has the total engine treatment.

 

I went home for lunch and this is who did my pistons.
http://www.rtdz.com/swain/old/prices.html

 

Swain Tech do a lot coating for nascar engine builders. They do all sorts coating and they are only 7 minute away from my house.


Bruce
93LT1 Conv w/ZF6
top end mods
jetted 150hp NX

 

Interesting.......

 

Hey gkull....whats the height of the coating? or do they machine the parts to get the same dimensions as before coating?

 

I'd recommend against it for a street motor. I've never seen any legitimate data supporting the benefits of thermal barrier coatings on pistons, and I was a design and release engineer of pistons for over ten years for a major automotive company. I cannot think of any legitimate reason for it with respect to horse power increases but I can think of a few reasons not to do it! Here they are:

1) Higher chamber temperatures. The two main paths for heat transfer from the combustion chamber are through the piston dome and through the cylinder head. Sure, there are some supposed benefits to retaining heat in the chamber (more heat to do work on the piston, yada, yada, yada). But with more heat comes higher temperatures, and higher temperatures mean lower detonation resistance, which in turn means you are more knock limited with the fuel you are using. The result is you have to turn your timing back to limit detonation and you lose torque because you are not at optimum spark timing anymore. For the same reason aluminum heads give better knock resistance (higher thermal conductivity of the aluminum) than cast iron, the thermal coating will reduce knock resistance (lower thermal conductivity).

2) Coating adhesion problems. Ever seen a piston that has experienced prolonged operation at knocking conditions? It looks like a sponge on top because little pieces of aluminum are eaten away from the dome of the piston every time you hear that baby knocking (sometimes you see these pieces deposited on the spark plugs). You're not going to get the coating to adhere under these conditions -- No way. And what are these little pieces going to do in your combustion chamber? Hint: they're made of ceramic and so is the stuff on sandpaper. Nuff said?

3) Very little benefit(?) for the money. I'd be real suspicious of data that shows any kind of significant power gain due soley to thermal coatings.

In summary, if you're running a race engine which you'll be using ultra high octane fuel in and don't mind rebuilding frequently, it might be worth the trip, but I'd say no way for a street motor.

BTW: I've seen diesel pistons that are anodized on the dome (anodizing is a controlled oxidation process of the aluminum which forms a type of metallurgically bonded ceramic layer on the top). This IS benificial for two reasons:

1) It insulates the piston from the ultra high temperatures of a diesel.

2) It forms a compressive stress layer on the dome of the piston which minimizes the tendencies for the piston to crack on the dome. A diesel operates at 2000+ psi combustion pressures (the best spark ignition combustion pressures are limited to about 1200+psi).

Sorry about the long response, but I hope it was worthwhile.

 

Everybody can have an oppinion. I think what your not seeing is detonation is caused by hot spots in the cylinder. So in the days of cast iron heads every hot rodder polished the chamber to ensure that no sharp edges would induce preignition. You can cause ping by just having a spark plug of the wrong heat range that doesn't conduct heat away from the protruding tip fast enough.

Your right in your statement that thermal barrier coated pistons and chamber would cause a rise in combustion temp. Well when the exhaust valve opens I hope that all of it is gone roaring down my headers and now because of all my thermal coating the tempeture of my piston top, chamber, and exhaust valve are all lower than what it would be in a none treated motor I can safetly run .5 more C/R with the same timing and the same octane.

The motor runs cooler because your not X-fering heat to the water or oil. That's where I didn't have enough done. I should have also coated the ports. Just think of how much heat is induced into the water jackets around the exhaust ports.

When you have a thermal barrier the piston would be stronger because of less heat. I saw a demonstration of uncoated .030 thick aluminum sheet metal. You put a torch near it and it melts and a hole falls out. The they coated the aluminum and it wouldn't melt. I also believe that the space shuttle works because it has a thermal barrier. I also never have motors designed to make any kind of 7/70 warranty plan!


[Modified by gkull, 11:01 AM 9/5/2001]

 

MASTERFULLY said gkull, I know for a fact that without thermal coatings, turbine engines, wouldn't be as powerful as they are today, and their longevity, wouldn't be that great also. I've also seen where clooged secondary fuel nozzles, caused improper fuel burning, and if it weren't for the TBC, the cCOMBUSTION LINER would have ruptured. I don't have to draw you a picture of what would have happened if this liner ruptured. I'm a FIRM BELIEVER OF THERMAL BARRIER COATINGS. :cheers: :chevy

 

gkull, I know your attention was directed at lemans but you didn't answer my question about the height of the coating.

 

Lohkay I also had concerns because I was planning on running .044 or so Quench for the highest swirl and again eliminate any chance of ping if I hit it with big doses of NO2.
http://www.swaintech.com/race.html The coating in negliable in thickness I think they told me @.005 or less.

 

I don't want to belabor the point, so I'll shut up after this post. But...

For the type of motor that's typically driven on the street TBCs shouldn't be necessary to keep the pistons from failing. And yes TBCs will promote hot spots because you are providing a barrier to heat transfer away from the piston suface, in turn promoting knock, pre-ignition etc. You actually WANT some degree of heat transfer to occur to prevent hot spots.
Spark plugs work the same way, the electrodes on cooler plugs conduct heat away (into the head) more efficiently than hot plugs.

Just because TBCs work in gas turbines and the space shuttle does not mean they are a great idea for piston coatings. The applications are just not the same!!! Turbines use transpirational (air film) cooling for their combustion chambers and blades as well, but that doesn't make it a great idea in a spark ignition recip motor. Ceramic coatings are used in diesel pistons because knocking and pre-ignition aren't a concern.

A few years ago I designed, and had a "source" of mine, make some pistons for a friend's Bonneville racer. His turbo 2.5L four banger put out 420 HP (for a 350 ci motor at the same specific output, that's nearly 1,000 HP) at close to 40 psi of boost. The pistons were based on OEM production forgings with a few modifications to improve pin oiling, and some ring land alterations. The conn-rods were drilled to shoot oil up to the underside of the piston in order to PROMOTE heat transfer. Not a TBC or anything else exotic in sight anywhere, just sound design principles. The pistons lived fine*--in fact, for a few seasons. And he went fast enough to set a record of 210 mph in the flying mile for his class. He also drag raced the car and could run high 10 sec 1/4s all day long with a gear change and slicks.

If you've absolutely wrung out the lubrication system, fuel delivery, spark, and cooling system concerns and you're still toasting pistons in your motor 'cause its making just too damn much power, then by all means TBC the livin' poop out of it, but I still maintain that TBCs are overkill in a street motor.

Of course if it just makes you sleep a little better to have your motor's pistons coated with TBCs, then that's worth the money too.

...sweet dreams. :sleep:


* We didn't verify 7/70 reliability, though. :D :D :D

Thanks for the lively discussion on this one, GKULL. I've read a lot of your other posts and I think you've helped out a lot of Forum members with your experience, and I respect your opinion. I just happen to disagree with you on this one. That's the beauty of the Forum-- lots of opinions from lots of different viewpoints and experiences.:D :D :D

 

Hell, we all have our opinions, but the one that I trust unquestionably are those put forth by David Vizard. Ceramic coatings do work and not just for racing engines. Sure, the money can be spent elsewhere, but for performance gains and some insurance, I'll continue to coat my engine. It promotes better flame fronts for more complete burn of air/fuel, no hot spots for detonation. By coating the combustion chambers, valves face and back, and the exhaust port completely, the heat generated is not lost through the piston crown or cylinder head chamber and in used to generate power. Period. The chamber coatings prevent heat loss into the head and water jackets reducing operating temperatures and with higher exhaust temperature at valve opening increases exhaust speed and scavaging. Sure, some coatings can be poorly applied and hotspots become apparent. But having the coatings applied professionally, i.e. SwainTech, you'll be happy with the results. Don't think so? Pull the heads after 6-mos to a year and see what they look like. Coatings last. Heat is what makes the power within the cylinders and the more you can generate, and not at destructive levels, and effeciently used, the more power you'll have. I suggest you investigate further from those that know. Bottom line, if you want every ounce of power your engine can generate, coat, if not, spend the money on something else.

 

My goal was to have a street legal 200+ mph car out at bonneville salt flats. Every edge I could have to do it I did. I saw so many blown motors out there three weeks ago. I drove 440 miles out there and drove back home. I guess I built a good running motor. Any body can make 11+ second drag Vette, but all you do is beat it up and someone is always faster. The only way to go drag racing is a dragster or a drag bike. I used to get pissed waiting in the hot sun staging lanes for slow cars doing a one wheel burn out and then oil the track.

Vettes with wide tires and quick steering are not what you want to show up with. From going to Nevada open road races we figured out that low to mid 500 hp is required to run over 200. So I built the motor to do it.

 

Well first lets take a look at the question and clarify something. What everyone is talking about is a dry film coating on the pistons, not ceramic coating. That is used on headers etc. If you did that to the pistons you would not even be able to get them into the block. Yes I think there is more to be had out of a motor that has been coated. It is a lubricant, and anything helps. So if you are pondering the question if you should do it or not, the answer is yes. :yesnod:

 

I know this is old, but I like the information in it. Ceramic coatings aren't just good for the engines, but they're also good for brakes. VB&P is doing it to the inside of class specified brakes to prevent heat transfer to the brake fluid. A few companies are coating the metal plate above the intermediary pipes to prevent heat from getting into the cabin. Of course there's also all the stuff you mentioned. Good stuff. ttt for coatings!

 

A point of clarification. Detonation is not caused by a hot spot in the combustion chamber. A hot spot causes the mixture to be ignited before the plug fires, and therefore is called preignition. Only relatively thin metal will cause preignition. A head gasket hanging into the bore, unchamfered combustion chamber to deck surfaces, casting flaws in the chambers, and even spark plug threads, are examples of metal thin enough to heat and/or glow sufficiently to ignite the mixture. When the flame front from the preignition meets the flame front from the spark plug, a ping occurs.

Detonation is a secondary flame front from another cause. As the spark plug initiated flame front progresses across the combustion chamber, the mixture ahead of the flame front, known as "end gasses" are compressed by the gasses behind the flame front that have already burned. As any gas is compressed, the temperature increases. If the temperature becomes high enough, the unburned end gasses will ignite by the heat of compression. That is detonation. Detonation is a rapid, uncontrolled, high heat, violent combustion. The pressure and the heat can burn holes in pistons and wreak other damage. As you can see, detonation is actually POST ignition as opposed to the preignition caused by hot spots. Gasolines with higher octane have a greater resistance to ignition by the heat of compression.

Obviously, combustion chamber gas temperatures and pressures are a tricky subject and have more than one means of control. Enough for now.

RACE ON!!!

 

Preigntion often leads to detonation because it's the same as advancing the spark, so the end gas is at higher temp/pressure before being consumed by normal flame front propagation.

Detonation due to a cause other than preignition (such as insufficient octane) heats up the combustion chamber boundaries, which can lead to preignition that worsens the detonation situation.

The real damage of detonation is overheating the combustion chamber boundaries. Detonation increases the heat transfer rate to the boundaries by up to an order of magnitiude.

Duke