ceramic coating pistons and other engine components.

[Flaminsam]

Hey guys and girls.

Just out of interest how many of you have looked into ceramic coatings? The most common ceramic coating is probably the exhaust manifold. But what about pistons? Valves or combustion chambers maybe?

[pacman]

I looked into ceramic coating and through research found http://www.zircotec.com/ to offer the best quality coatings.

More £££ than I was prepared to spend though; iirc it was £160ish to coat a manifold. They will do piston crowns and valve faces too. Some people also have their turbine housings done.

This article makes for interesting reading if you're into this sort of thing: http://www.hotrod.com/techarticles/engine/hrdp_0612_engine_coatings/viewall.html

[Flaminsam]

Yea ive also done a bit of research into zircotec and found them a little pricey.

The reason I ask is that a few people have problems with keeping their cylinder temps down. Surely of the crowns of the pistons and the valves were coated they should be protected from the likes of detonation and excessive heat? if the pistons reflect the heat away and out of the exhaust for instance surely that should be a good thing? Increased scavenging effect and lower afr's? Should give more power if im not mistaken?

[AdamB]

I would be careful Sam, some piston manufacturers don't like the use of coatings. If your thinking stock pistons then might be worth a go, but if it's a forged set I would contact the manufacturer first to ensure that they have no problems with it being used on their material.

If you have trouble keeping cylinder temps down you have a problem elsewhere. 75-80% of combustion heat is lost through the top piston ring into the water jacket, so if your overheating chances are your cooling system isn't upto scratch. Also am not sure if a cermaic coating would actually deflect heat away, its primary use is to contain heat within a system to give the gasses more energy to flow at a greater velocity, much like exhaust manifolds. If it was to do so on a piston they would turn to marshmellows pretty quickly as the heat isn't being allowed to escape.

You could look into getting the valve seats coated with DLC, I know Arrow Precision do this as its something I'm going to do myself. No matter how good you can lap a set of valves in, after the first 1000 miles you will leak 1% through the valve seat. Having a DLC coat on the seats helps prolong this. You can also get DLC coatings on bores, but once again I would contact the piston manufacturer as it's ulitmately them who determines how your bores are prepped.

Edited April 24, 2013 by AdamB

[AdamB]

Edited April 24, 2013 by AdamB

[Flaminsam]

So if standard pistons are coated they should last longer and cope with heat better? Also if you were to have for instance the bores ceramic coated (like some high power bmw's have as standard) the water jacket around the cylinder would not have as much to absorb heat wise I mean?

Would this put excessive heat into the first compression ring and cause it to fail?

This is all just theoretical at the moment, but surely it will make a difference to longetivity of a performance engine?

Just my theory is heat kills engines, so if the engine doesnt absorb as much heat it should be more efficient. Should provide a clean burn with less waste and higher adiabatic efficiency giving more power.

I thought insulating parts like cylinder walls, pistons, valves and combustion chambers would aid the engine as we try and get more power from them.

[AdamB]

To be honest am unsure as its not really what I would use ceramic coatings for. I would have said that ceramic coatings are used to contain heat rather than disperse it.

The water wouldn't have much heat to absorb, but at the same time the pistons have to be able to cope with the extended heat, most likely ruling stock pistons out of the equation.

The heat wouldn't cause the ring to fail, but what you could potentially do is increase the ring gap to allow the excess heat to blow past the piston, I know this kinda makes it pointless as its essentially throwing heat energy away. But without removing the heat it would take longer for the heat to be carried away from the piston and into the water jacket and surrounding area's, therefore heating the piston up and potentially causing it to fail.

I know exactly what you are saying, and that the internal combustion engine is only 30% efficient, and if we can keep heat within the cylinder we'll raise the efficiency of the engine, giving a direct performance increase, making the engine 5% more thermal efficient will lead to a 5% performance increase. However what I think would be a better idea, would be to coat the inside of the water jacket and the outside of the block. This will keep heat energy inside the cylinder, but still allow the heat to escape into the water and oil, although the cooling system will most likely have to be beefed up to cope with this.

[Flaminsam]

Yea I see where your coming from. The heat has to be dispersed somewhere as a by product of the combustion process so a bigger or more efficient cooling system would need fitting.

Just out of interest how much heat is passed out of the exhaust? I guess after the piston has reached tdc (and the air/fuel mix has been ignited), by the time the piston is at bdc the heat will have a small ammount of time to transfer to the cylinder walls to the water jacket. But surely some heat must leave with the burnt air fuel mix out of the exhaust port? Hence why scavenging should be promoted as much as possible with valve overlap?

This is turning out to be quite involved with engine theory after all :-S.

[AdamB]

30% is lost into the cooling system, 30% down the exhaust system and like 15% radiated out through the engine block/head etc. Goes to show inefficient the internal combustion engine really is!

I believe in heat wrap helping to give the exhaust gas a greater velocity upon exiting the port, and velocity is directly related to pressure as well would help promote removing any residual gas left over in the cylinder, but also manifold/port design as well. From what I've seen the port of the manifold should line up so that the roof is slightly higher than the roof of the port, since we know hot air rises this pushes the gas into a smaller space to leave the cylinder, increasing velocity and pressure.

Scavenging does play a big role, but obviously you can't go too wild with the overlap or it will run like a bag of spanners, the No1 thing to first consider is to burn the entire amount of mixture in the cylinder, which the piston, combustion chamber, quench area all play a big part.

Edited April 25, 2013 by AdamB

[Flaminsam]

This is all making good reading really. Il be wrapping my new exhaust manifold when i come to fit the engine back in my car.

Also adam have you heard of the 1/4 opening of the diameter of the valve tale? Ive heard of it before when i did some research into cam lift and duration.

The story i guess goes like this. If you have a valve of say 100mm diameter and open the valve with 25mm of lift you will not increase the flow through the valve opening.

Here is a graphic i found.

does that make any sence?

[AdamB]

I haven't heard of that exact term, but something similar.

If the valve diameter is increased, its possible to run less lift because it's just another way of increasing air flow, if you were to do both it turns into a stale mate situation where you either need excessive valve lift to make use of it, which in turn makes the engine run lumpy and impossible to drive unless it idles really high. Much like what you have said. Therefore ideally its really one or the other.

Some engines actually respond better to a smaller valve and or less lift, this is one area where the 1.3 N/A engine really suffers! It uses exactly the same components (except springs) as the FTE heads, yet the FTE heads flow enough for 340bhp in stock trim. Lets be honest, a 1.3 N/A engine is never going to even reach half that power output. With such large ports and valves for such small power, the velocity through the ports is going to be somewhat lacking, and since velocity and pressure have a direct relationship, pressure also drops, meaning poor atomisation of the fuel.

I'm actually on the lookout for an N/A daily, I was tempted to get another head and sleeve the ports to see what kind of impact it would have by raising the pressure in the ports. Some people tend to weld the ports and then smooth them back, but that for me seems a lot of work for something which may not even yield any gains what so ever.

I remember reading an article a little while ago about a Porsche 911 race car (can't remember what series), but they designed the head with large valve diameters and it really suffered in mid range power, Porsche then redesigned the head and fitted slightly smaller valves and the peak power was actually up over like 9 tenths of the rev range.

Edited April 29, 2013 by AdamB

[Flaminsam]

So basically the smaller valve would create a venturi effect a little like a carburettor causing greater velocity and higher pressure?

So how are the fte engines set up then? i understand that 300+ bhp can be achieved quite easily with stock cams but do they have a lift/valve diameter of roughly the 1/4 that we have mentioned already?

Would be interesting to see what would happen with slightly longer duration, creating slightly more valve overlap and increased scavenging with the optimum ammount of lift on the valves.

When i first came into modifying engines the thing to do was ''stick a cam in it and get the carb rejetted''. Now its much more intensive with electronics and injectors.

[AdamB]

Just to add as a bit of interesting reading.

Done a bit of digging around in some old engine tuning books of mine.

According to one source the intake ports should be 0.83 the size of the valve diameter, however if the valves are already too large for that specific engine then it's possible to take this down to 0.77 size of the valve diameter.

I would expect it to be much like a venturi effect, but its hard to say without actually spending some £££ on flow bench time and modifying a cylinder head each time. Saying that though a turbo engine can most likely get away with using large valves/ports because its being force fed rather than relying on the piston and gravitational acceleration. Although it would depend exactly what kind of setup your looking to run, something like a tight twisty track you may get away with smaller sized ports to boost up mid range power. Another thing to consider would be the gear ratio's, a small lightweight car will run quite happily on long ratio's because its acceleration is that much greater. Do the same with a car which ways 1500kg compared to 800kg, it will be sluggish and never make a good car to drive.

The FTE cams have a duration of 224 In, 228 Ex. I haven't actually a clue of the stock valve diameter in truth.