- With any performance engine, reliability and reducing wear while maintaining maximum
performance is obviously a key aspect.
And once of the applications that can be used to help in this area is performance coatings on
these engine parts.
We're here with Gary from Calico Coatings to talk a little bit about the engine coatings
available and how they can help.
So Garry, for a start, there are a huge number of coatings that are available for your internal
engine components.
One of the ones I want to find out a little bit more about is DLC.
So can you tell us for a start what does DLC stand for?
- DLC is an acronym for diamond like carbon coatings.
They're used primarily in race engines.
- And what sort of components would you be applying that DLC coating to?
- You normally see DLC coatings in wrist pins, and valves, typically on the intake side.
Although you do see more and more used on the exhaust side as well.
- And when you're applying that coating, so what is the physical process that you
got through in order to apply that coating to a fresh component?
- DLCs are applied in a vacuum chamber.
You typically clean the parts very well, it's key to getting a good DLC and they have
to have an extremely good finish on 'em.
We typically like to see DLC parts in the two micro inch category before we coat it.
Although you can get away with a little more depending on the application.
And then once you put 'em into a vacuum chamber it goes into a deep vacuum,
three to four turns below atmospheric pressure.
And gases are introduced into the chamber and molecules are broken and then the
plasma's created and it's attracted to the part, basically it slams into the part
and becomes part of the part.
And they're typically very thin, about two to three microns in thickness.
- Now that was actually the next part I wanted to talk about, even though they are very
thin is there a need, if for example you were coating a wrist pin, we see that applied to,
with DLC being applied to wrist pins quite frequently.
Is there a need to account for that in the wrist pin to pin boss clearance inside
the piston?
- Normally we would tell an engine builder to go with the normal clearances they
typically do when they first start using any coating.
And then what you'll find is that coatings will allow you to run thinner lubricants and tighter
clearances to control your oil scavenging inside the motor a little better and you slowly close
that up until you start seeing some detriment and then open it back up like you would
and any good engine builder would do.
- So it's just an iterative process of finding out where the happy place is for that
particular component with the coating?
- Correct, correct and you'll find that you can run tighter clearances with oils or DLCs and
dry film lubricant type coatings than you normally do but you just don't want to
jump right off into it if you've never done it before.
- That could be an expensive mess in the end.
- Absolutely because we can't account for everything that's going on.
There's a lot of lubricants out there and you absolutely can run thinner lubricants
when you start running coatings as well but you're going to have to play with that some.
- Alright so, let's just focus on that wrist pin again, so where would you see the
advantages in a DLC coated wrist pin compared to the non coated component?
Are we talking about frictional reduction, are we talking about life expectancy or is
it a combination?
- Well it's a combination.
You DLC coat a pin with a good DLC coating and a good pin material, 'cause there's a lot
of different types of pin materials and any engine builder will tell you that.
But pin material's irrelevant to the type of engine it's going in.
Then you put a DLC coating on it and it's going to give you a lot better lubrication
properties and it'll allow you to tighten those clearances up and then you can run thinner
oils and it'll give you a lot greater life and you'll typically get, with a DLC coated wrist
pin for example, you'll get the life of the material as opposed to the life of the
coating, is where you'll be at.
- So the coating is not going to wear off is what you're saying there?
- Correct, correct.
- Just to put some perspective on it, and obviously it's going to depend
very much on the size of the wrist pin but could you give us some idea of the cost
of a DLC coating on a wrist pin?
- Well your typical average wrist pin, say for your small block or big block
Chevys, Fords, run from about $28 to $32 per pin.
- Alright so moving on, the other component you talked about there with the DLC coating
was valves and a slightly different aspect with the application of that coating, why are you
DLC coating valves and where's the advantage?
- Well you coat 'em for relatively the same reason, so lubrication between the seat
and the valve face.
When they had leads in fuels, wasn't really a problem 'cause the lead served as the
lubrication.
When the EPA came in and started taking lead out of fuels, racing world had to follow that
suit so being the good friendly partner that we are, so we had to come up with
ways to lubricate that contact.
And DLC became the accepted form of lubrication between the face and the seat
of the valve.
- Now safe to assume that if you are going to DLC coat a valve then the engine machinist
is going to need to cut the valve face before it's coated?
- Yes, everything needs to be done and then the valve of course has to have that same
finish on it.
And that's where you get a little tricky from applicator to applicator because you
don't ever want to do things to a valve that's an applicator like roll the edges over
'cause that's going to kill the performance of the engine.
And it doesn't take very much on that valve seat to kill horsepower in the motor.
- Now you're also talking about alternatives to the DLC coating on the valves as well
for reducing wear, particularly in dirt track engines, can you talk about the coatings
available there?
- Normally in a dirt application you wouldn't use a DLC, you'd use a chrome nitride,
we call it a CRN coating.
Does the same thing but it's a little harder, doesn't have quite the lubrication properties
but it holds up a lot better to a dirty environment which say a 360 sprint
car's going to see, whereas when you get into the hastatics of a NASCAR cup engine,
it doesn't see near the trash going through the motor that a dirt spring car will for sure.
- So to sort of break that down, the DLC coating, the NASCAR cup motor,
that would be where you'd apply that because of the cleanliness of the engine,
the way it's being used.
With a sprint car engine, because of the dirt it's going to end up ingesting,
the Chrome nitride coating would be better?
- That would be my recommendation and that's what we tend to see out in the real
world when the coatings are being used and engine builders are asking for certain
applications of coatings.
That's certainly how it breaks out most often.
- The next natural question, particularly as it applies to the valves there is when
the engine is freshened up and the valve seats need to be, or valve faces need to be
recut, where does that leave us with a DLC or a chrome nitride coating,
can the valve be reused or does it need to be refaced and then sent back for
coating again?
- It's not typically recommended that you do that but it is possible to do that on a
chrome nitride valve, would never recommend it on a DLC valve.
There's just no good way to strip DLC off of a valve.
We typically work with titanium valves.
Normally these coatings are going to survive the valve, life of the valve,
the valve's going to start tuliping or cupping or stretching beyond its life
before you're going to need to do that.
But you can see that in some of the lower budget teams with the CRN valve,
it's possible to strip if off so yeah it's possible to do it there but I wouldn't
recommend it on a DLC valve.
- In most instances, the DLC coating essentially is going to outlive the valve,
your'e going to throw that part away and replace it with a freshen up essentially?
- Oh absolutely, hands down, these coatings are really really tough.
They're very thin but man they're tough.
- Alright so moving on, the other aspect I wanted to talk about is the coatings
that you can apply to a bearing and this is something I've had no personal experience
with, the general consensus out there in the industry is that the bearing surfaces
really shouldn't be coming into metal to metal contact between the bearing surface
and the crankshaft journal, bring protected by an oil film.
And if that's the case then it would stand to reason that a coating on the surface
should really give us no advantage.
So what's the actual truth there?
- Well you're 100% correct, there should never be metal to metal contact on a bearing.
And as long as there's an oil film between a bearing and a crank, I don't have any
particular preferences to a brand of bearing, I think they're all good bearings and I think
they'll all hold up to the manufacturer's life but what the real world sees is that there
is metal to metal contact.
If there were no metal to metal contact, you'd never lose a bearing but we know
that happens right.
So those moments of time when there is that contact, that's when it's a really good
time to have a secondary source of lubrication which is what a bearing
coating is.
It's not a primary source of lubrication, in most cases it's not even a real good
lubricant in a wet environment because typically most engine bearings use
some type of molybdenum disulphide type coating as a load bearing capacity.
Molys don't normally lube well in oil, it's just not the nature for 'em.
They're good dry film lubricants but not oils.
So most companies like ourselves and other companies, we put other things in there
with it to give it the lubrication properties which we can't really get into a lot of that.
But you need that moly for that load bearing capacity so we typically say
that bearing coatings are a moly based coating 'cause that's generally the body
of the coating.
- So that moly in the coating, that basically prevents the coating just being squashed
out under high load, that's what you're saying there?
- Absolutely, otherwise a typical set, teflon by itself, it'd just squish right out like
jelly, you can't have that it'd smoosh up.
So you want that load carrying capacity so most of 'em are moly based coatings.
And they will allow that bearing to hold up for that momentary loss of oil
pressure or that momentary loss when you first start the motor when you don't
have good oil pressure.
And that's what a secondary source of lubrication's good for.
And it will allow you to generally over time tighten your oil clearances up because
it does provide a good source of lubrication and that's what it's used for.
- Alright so there's a couple of aspects I want to touch on there.
So the first one, just to really sort of wrap up what you're saying there,
it's essentially, the coating could be considered a safety backstop for when
we get into those situations which we hopefully should never be getting into
with metal to metal contact.
Basically giving you the ability to potentially live through that situation without instantly
damaging a bearing?
- Absolutely I mean we race, we're racers, the company was built on racers.
We race, right now we have racecars that compete every weekend and so we know
that what we see typically when we're starting to have engine trouble,
is the oil light will tip on.
The driver will radio in, the oil light's on, only in the corner.
It goes off on the straight away.
Well you're about to run into trouble, it happens, well it's a good time to have
a coated bearing in there to get you to the end of that race without blowing the
motor up.
- Alright so the second aspect you mentioned there, just talking about the clearances,
so obviously you're building up the thickness of that bearing material and we already talked
about the thickness of the DLC coating.
I'm not quite sure how that relates to the thickness of what you're applying to the
bearing but does the engine builder need to take this into account when setting
clearances?
- Yes he does, we typically would tell a new coating user, go with the clearances
you currently use and sizes like you normally would with the coating on the
bearing, measure the bearings out, run the motors, get comfortable
with the coating and what it looks like.
And then you start slowly tightening your clearances up and you'll see that you
typically will be able to tighten up a considerable amount with a coated
bearing over a none coated bearing.
But now what that number is, depends on the engine builder, the application, RPMs,
all that.
- So can you give us some of the advantages in a competition engine
of being able to tighten up that oil clearance, get that a little bit narrower
or smaller, where do we see those gains?
- Well that gets back to your scavenging of oil, you don't want oil sloshing around
that motor 'cause that's parasitic load on the crank and all and just slows the motor
down and that's not good.
So it's going to help you out there because you're going to be able to control that oil.
You're going to be able to run thinner oils than you normally typically might would
and those are probably your biggest advantages there.
- And a thinner oil reduces your frictional losses inside of the engine while it's
operating?
- Yes.
- Alright look it's been great to get some insight into those coatings Garry,
and if people want to find out more about Calico Coatings, where can they go to?
- They can go to www.calicocoatings.com and call our office, we love to talk
to people, we help with a lot of engine problems.
Typically you're calling us because you have a problem.
If everything's sunny and clear and 72, we don't get very many of those calls.
- Perfect, thanks for the chat.
- Thank you.
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