Are Piston Coatings Worth Having AND Can Coatings Save Your Engine? [TECH TALK]

Are Piston Coatings Worth Having AND Can Coatings Save Your Engine? [TECH TALK]

– There’s a belief in the high performance
engine building world that piston coatings are some kind of magic solution to an
improperly tuned engine and we’re here with Eric from Mahle Motorsports to find
out what the actual truth is with that situation. So first of all Eric, just to address that point
I’ve just made, I think a lot of engine builders or tuners think that if we’ve got
a thermal barrier coating on the piston crown that we can do no harm and that
piston’s going to survive no matter how much boost we throw at it, how lean the
air/fuel ratio is or how much detonation the piston is being subjected to. Safe to say, there’s no truth in that? – Well I don’t want to call it a bandaid at
best but it’s certainly no magic bullet either. So the thermal barrier coatings, if they’re
going to block heat and you get into a situation where you’re going to overheat
or melt that piston, it’s going to melt it through the coating. The advantage of the coating is it may buy
you some time or it may delay the onset from a point where you can push the engine
a little harder, push it even further than that and that’s where you’re still going to
run ultimately into damage. – So ultimately it’s going to give us a little
bit more margin for error, it’s definitely not a bandaid for doing the job properly in
terms of the tune up I want to really get into where the key benefits with these
coatings that we see applied to pistons. And for a start I want to talk about the
normal range of coatings that we do see so can you run through what our
options are there when we’re looking at a fresh piston, what can we apply to it? – Yep three main coatings, the thermal
barrier that we talked on that you’re typically going to see on the crown of
the piston. The second is protection for the ring groove,
primarily top ring groove which is traditionally a hard anodised or nickel plating,
we at Mahle prefer the hard anodised version of that and the third is your skirt
coatings. – Is it safe to assume that not all of these
films or techniques are the same between different piston manufacturers, are there
variations between what one particular piston manufacturer will use and what
you’re using maybe? – Everybody has a slightly different variation,
a lot of the intent and purposes are the same, let’s take skirt coatings for example,
you have coatings that are made to be break in coatings, you have coatings that are
made to be applied extremely thick, then the coating itself is abradable so that
it changes to the shape of the piston and finds its ideal thickness so to speak. And then you have coatings that are applied
and meant to be there for the life of the engine and that have either, not necessarily
break in but friction reduction capability and/or protection against scuffing. So on the surface, all three of those coatings
on the skirt may look identical but they have slightly different purposes and different
intent for what they’re going to do over the life of that piston and then hence the
engine. – Now that skirt coating, as far as Mahle is
concerned, it’s the third of those aspects you’re talking about friction reduction and
it’s a coating that should be there for the life of the piston? – Yeah absolutely, that’s the same coating
that we put in all of our OEM manufacturers, it’s the same coating that we use for the very
top race series pistons, it’s the same skirt coating that we put in our shelf stock catalogue,
every day average, build it in your garage piston, it’s the exact same formulation,
exact same process for applying it. And if everything is perfect in that engine,
it’ll be there as long as that piston will last. The caveat is perfection is very difficult
to achieve. And when it’s not perfect, that’s when the
coating becomes sacrificial. So it’ll take the brunt of a part that’s
overheated, it will, if you get into a marginal lubrication situation the
coating becomes sacrificial. Rather than scuffing the piston immediately,
again it’s buying you that extra margin of safety to help the part survive. – Now there’s a couple of aspects I just
want to touch on there. So you’re obviously applying this coating
to the skirt of the piston after the piston has been manufactured so obviously there’s
some material thickness of build up there. Does that then affect what the engine builder
and machinist need to do in terms of piston to cylinder wall clearance or is it really a
non event, don’t need to consider it? – For the PowerPak kits that we sell, no,
because that’s a function of the fact that we coat every piston that we sell so
it’s designed to be coated from the beginning. So when our engineers are looking at
speccing out clearance on this piston, they know that coating’s going to be there. We really size the piston according to the
bare aluminium for what it’s going to run in a cylinder. The coating is added afterwards but we spec
out all of our clearances over that coating. One, that’s what the engine builder can
measure and two, we know that we can run slightly tighter with coatings because
it’s got that margin so coating goes away, you still have the bare piston to run in
with the right clearances so by designing and selling the parts coated from the factory,
not having to send it down and have somebody else’s coating, we’re able to take all that
into consideration and put it in the box, on the shelf with the clearance that we want
the engine builder to set it to. – So you can be confident then when you
receive those parts, the clearance is what it needs to be, no need to take the
coating into account, it just is what it is. Now in terms of the operation of that
film on the piston skirt, the friction reduction, so this is something
I just want to get into a little bit because everything’s working right, we do have an
oil film essentially protecting the piston skirt from metal to metal contact on the
cylinder wall. So on face value the advantage seemingly
of that friction reduction coating might be a little bit limited so can you talk to
us about how it actually gives us that benefit? – Yeah there is some slight properties of the
material that as, the way that it interacts and transports oil, there’s some advantage
and that’s part of the friction reduction. But the bigger factor is that the piston
doesn’t travel in one constant motion. As it’s moving up and down the cylinder,
it stops, it changes directions. Every time that it stops, you have that
potential for metal to metal. And not only does the piston stop but
it rocks and it travels back and forth in the cylinder in addition to up and down. So in those circumstances, when the piston
is stopping or rocking, that’s where you see, or let me back up one step, as it slows
down and speeds up away from those stopped positions, that’s where you have
mixed lubrication and that’s where the real advantages are. In addition, with the coatings in that stop
and rock situation, it also helps with noise and in an all our race motor, piston slap’s
not a big issue but you start getting into more street applications and guys are
replacing, particularly in modern vehicles where everything is so quiet, you can’t
put a loose forged piston in there and deal with that noise and the coatings,
that’s another advantage where they help you. – I don’t think anyone building a performance
engine with forged pistons wants their brand new performance engine sounding
like a diesel on initial startup. Alright so moving up the piston, the hard
anodising for the piston ring groove, can you tell us why that’s necessary and
how it’s an advantage? – The biggest factor of the hard anodising
is to protect against micro welding. And micro welding is simply a result of
the cylinder pressure that is pushing down on the ring, forcing the ring into the bottom
of the groove and that’s where sealing occurs but at the higher temperatures and
higher pressures you can actually start to have localised melting of the aluminium and
the piston ring picks up that aluminium and it starts to transfer it and as the ring
rotates it’s dragging this molten aluminium around the part and/or it melts and solidifies
and so if you see a micro welded ring it actually has little specs of aluminium for
lack of a better term welded to it, and then it takes those welded specs and
drags it around which completely tears up the surface of the ring groove which
is where the sealing really occurs. So the hard anodising changes the structure
of the aluminium by turning it into an aluminium oxide which is much harder and
it protects you or gives you protection against that micro welding. Very very typical in modern late model
engines where the rings are very close to the top of the piston which is excellent
for power but very tough on components so the hard anodising is an alternative to
allow you to retain that ring position at the higher temperatures and pressures. – So really you’ve just talked about moving
the ring up the piston which as you said aids power. And is it a case of as you move that ring
up the piston, it’s going to be exposed to more heat and that’s why without the
hard anodising you end up with the micro welding being more prominent? – The heat is the biggest factor that creates
it but it’s the combination, the heat alone won’t do it, you have to have it in combination
with the pressure, cylinder pressure but those two factors, they tend to go hand in hand
so if one’s higher typically the other is as well so it’s protecting against both. – Now off camera you did also mention that
that hard anodising coating actually just after its been applied, actually provides a slightly
rougher surface finish. So initially it can actually have a minor
reduction in the seal between the ring and the ring groove but that goes away
over time? – If you look at anodising under
magnification, it’s a very porous, very rough surface, much more so than
what you would see at the molecular level on bare aluminium. So the bare aluminium groove is actually
a smoother, better surface for sealing than the anodising but the anodising, the
ring will condition the anodising a little bit so you see some changes as the engine
breaks in. Very minor, it’s possible to measure but
probably not noticeable on the average build but it’s a factor, it’s a factor. – Alright so we’ve already briefly touched
on the thermal barrier coating and the fact that it’s not necessarily there to fix
a tune up problem but the real advantage when the tune is good and everything’s
running well, it’s designed to reflect the heat back out of the crown of the piston,
back up into the combustion chamber, can you tell us how that’s an advantage
in terms of engine performance? – Well being able to retain heat in the
chamber, using it for work versus just having it transfer to the piston,
once it’s transferred to the piston, it’s wasted energy, wasted heat. You’re not able to turn that heat into
energy. – So it opens up the tuning window
a little bit, changes the tuning window. The other part of that is heat is very
detrimental to a piston, by nature of aluminium material, it’s going to be
detrimental to it so not only are you opening that tuning window but you’re
trying to protect the integrity of the piston by keeping it cool, allowing it
to run cooler and allowing the piston to run cooler is a major benefit for
durability. – Now on that basis, if you’re transferring
less heat into the piston, does that by default mean that you can then run a
slightly tighter piston to cylinder wall clearance or is there really not that sort
of correlation? – At times but typically no because there’s
such a huge temperature differential between what happens at the top of the
piston and the crown of the piston, all coatings out of the picture, that
differential exists and even once you put a coating in, it just makes that
differential ever so slightly smaller but probably not enough that you’re going to
affect actual piston to wall clearance at the skirt. – Alright so we’ve talked about the three
primary coatings there and the last part I wanted to talk about there is the hard
anodising that you’ve got applied to that top ring groove. In some particular applications and Top Fuel
is the one that springs to mind, we actually see the entire piston is hard anodised so
why is that applied in Top Fuel and where’s the advantage from that? – In a case like Top Fuel that’s such a
harsh environment on every component that you put in that engine, it’s more about
trying to protect and control the damage as much as it is prevent damage. So we have to make sure that we’re not
tearing up cylinder liners, if the piston scuffs we want to control it to the piston
where you can take out the piston, replace it and not have to completely
refresh the engine. So it’s more about controlling the
method of damage as much as it is prevention. There’s some, again, safety factor that
it adds and it opens up the tuning window but it doesn’t prevent it but we help kind
of steer what’s happening with a coating like that in that application. – And obviously Top Fuel’s a pretty
extreme application where the engines are being torn down and a lot of the
components are being replaced after every single pass. What I’m interested in, because we get
asked about this a little bit is would hard anodising the entire piston be a
technique that would be even remotely applicable to a road car piston or a circuit
racing piston? – It could and there’s examples out there
where it is done but in my opinion, particuarly looking at what happens on
the skirts, we just touched on some surface roughness issues, why not use
a coating that’s made to make the skirt smoother, to aid in friction and a little
more forgiving on cylinder walls, basically putting the right coating in the
application or right places when it’s available. – Look it’s been really interesting Eric,
hopefully everyone watching now has a little bit more insight into those
coatings, what they can do, what they can’t do and how to choose the right
coatings for their application. If people want to learn more, how can they
reach out? – Best place to start’s the website,, it has all our contact information, we’ve got some
additional tech oriented videos, technology oriented videos that touch on a few aspects like that and if nothing
else, it puts you in direct contact to us where we’re happy to talk about it with
anybody that’s got questions. – Perfect thanks for the chat Eric. – No problem, thank you. – If you liked that video
make sure you give it a thumbs up and if you’re not already a subscriber,
make sure you’re subscribed. We release a new video every week. And if you like free stuff, 
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your free spot to our next live lesson.

10 thoughts on “Are Piston Coatings Worth Having AND Can Coatings Save Your Engine? [TECH TALK]

  1. cool content bro

  2. Are coatings something you've looked into at all before? Did this interview leave you with any more questions? Let us know and we'll address them in future content where possible for you guys 🤓
    Cheers for the support! If you want Andre's t-shirt but are struggling to steal it off his back, you can grab your own here instead just FYI: – Taz.

  3. Want some FREE MAHLE pistons for your own build? Enter the latest competition here:
    No sweepstakes, enter your card number there or give us some money here BS, it's as simple as a few clicks. Best of luck guys! – Taz.

  4. Dang, auto-play kicked me out of the live chat. Thank you for another great video Taz, almost read all of your last reply! If im lucky I'll manage to find another engine, maybe the EJ thats hiding in a corner 👌

  5. I know mahle has some 4g63 and 64 pistons lol

  6. 😍😍😍😍

  7. Can you ask if DLC coating the piston skirt works and by how much? What about DLC coating the ring groove rather than hard anodizing? I know piston pins benefit from DLC coating and I always wondered about Piston skit and lifters/buckets. 3SGTE specifically in my case.

  8. Excelenteeeeee, gracias

  9. Take a shot every time he says "Coohting".

    Prepare to die.

  10. Skirt coating yes. Thermal coating, not really needed for most builds. They do have their place.

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