- Getting a good quality ring seal is critical if you want an engine that's going to perform
well as well as limit oil consumption.
Gapless ring technology is something we get asked a lot about and we're here with Keith
from Total Seal Rings to talk about gapless rings and maybe debunk some of the myths
when it comes to ring technology.
So for a start Keith, while Total Seal aren't the originator of the gapless ring, it seems like
Total Seal has almost become synonomous with the gapless rings and for those who
aren't aware of how a gapless ring works, it actually does still have a gap but can you
tell us about the construction and how they go together.
- Absolutely, our ring is a simple 2 piece design, it's a thick ring and a thin ring.
Thin ring goes underneath the thick, we offset the gaps 180°.
Very easy installation, no special tools required and you've essentially got a
gapless piston ring.
We're the ones that introduced it into the automotive world in 1967.
Gapless designs just as you said, they've been around for well over 100 years.
They've been used in industrial engines, pumps, compressors, transmission seals,
they've been used in many many different things but we're the ones that brought it to
the automotive world and we're known for the gapless ring but at the same time,
I came to work for the company in 1997 and recognised that not only do we have this
gapless ring but we need to work on rings in general, all rings, conventional rings,
gapless rings, how do we keep pushing this further and further and further and
improving that technology.
- Now what I'll do is actually just back up a little bit because some people might not
really understand why we need a gap in the ring and obviously part of it is the construction
and getting it over the piston.
And when we're working with a conventional ring, what we're doing is selecting an end gap
for that ring when we're assembling the engine cold in the workshop so that when it expands
as it heats up and the engine's operating, we're going to end up with a minimal end gap
but that can be a risky proposition.
Go too far, the ring butts together, we end up with catastrophic damage so the gapless
ring allows us to be a little bit more conservative with the ring end gaps of
those 2 individual components but because they're 180° apart, doesn't give that path
for the blow by to get down past the ring.
Now in terms of running a gapless ring, what sort of advantages do these offer
in comparison to a conventional ring?
- Well that's a pretty easy one, the gapless ring, you're looking at multiple functions of
the ring.
Not only the first place we're going to go is ring seal on the intake stroke.
People like to always talk about blow by numbers, how much leakage it has and that's
a key element of the gapless.
It eliminates the blow by, it eliminates the leakage, at the same time because of that,
we're eliminating contamination getting into the oil pan, fuel getting into the oil pan,
dilution of the engine oil but most importantly on the internal combustion, naturally
aspirated engine, the ring does all the draw on the intake stroke.
Best cylinder head in the world, best camshaft, best fuel injection, best carby, all of that's great
but if the rings aren't doing their job on the intake stroke and filling the cylinders as best
they can, you're leaving power on the table.
So that's the real key to the gapless is how it affects the intake stroke and it seals and
draws harder.
- So essentially with a conventional ring what you're saying there is during that intake stroke
where you're creating a low pressure area inside the combustion chamber, obviously
you're using that to draw air and fuel in through the intake valves but that conventional
ring can also essentially end up drawing blow by or crankcase gases back up as well
which aren't what we want?
We do not want to contaminate that clean intake charge and because the gap
is there, we do lose some of that suction, some of that draw by blocking that gap off,
that depression is increased and you can actually see it, if you're looking at a
manometer, this gentleman last night we were out with, they're looking at Porsche stuff
and some Volkswagen stuff.
They're looking at numbers with conventional rings in the 5 and 6 range.
WIth a gapless ring they're in the 30s and 40s.
That much more effective draw on the intake stroke, that much increased seal.
- OK so that increase in the efficiency there. basically that's going to add up to an improvement
in the engine's volumetric efficiency and then we've got the reduction in the blow by
gases and particularly with a gapless ring we will see the evidence of the effect of
that gapless ring, particularly if you do a leakdown test on the engine?
- Yeah absolutely.
Typically a gapless ring motor, once everything's good and seated up,
you're going to be 1%, 2% at the most but it's very very common to see under 1%.
Gentleman here just a little before you just did a combination, he went to leak it,
he said the needle didn't even move, he goes I ad to double check it, make sure
I actually had the air hooked to it because nothing, he goes, it didn't even budge.
- So gapless rings though, you can set up the piston with a gapless top ring or a
gapless second ring.
Now this sort of goes against the general consensus these days that when we're
gapping our conventional rings, it's normally recommended by a lot of the piston ring
manufacturers and suppliers to provide a larger gap for the second ring than that
top ring.
Theory behind that is that if we have the second ring gap too tight, we can end up
with a pressure build up between the rings, resulting in destabilisation of the top ring.
Tell us your thoughts on that.
- Baloney.
It's a theory and with all theories, we're looking at a white sheet of paper, we're looking at
the theory, the theory holds water.
But there are so many other events happening within that engine, there are
so many different dynamic forces.
To truly get an engine into ring flutter is what that's commonly known as,
it takes a very very specific set of parameters to have that happen.
And it can happen, it truly can happen but in the real world, it almost never
happens.
It's commonly misdiagnosed as ring flutter but it's rarely proven to be
ring flutter.
I have so many customers, so many people, I'll give an example, I have a
particular sprint car engine builder.
These engines make almost 1000 horsepower, they're over 9000 RPM,
almost 17:1 compression.
He runs nothing but gapless second rings.
There is no ring flutter problem in this engine, it just does not.
It can't evacuate the cylinder fast enough on the exhaust side to depressurise the
top ring so there's a lot of horses that all have to align to have that happen.
We go back to engines 50, 60, 80 years ago, 100 years of internal combustion
engines, they've always had tighter gaps on the second ring than the top.
Trust me, those engines didn't have ring flutter.
The theory about having to open the second ring gap up has been around since
the early 70s and to me it is a theory, the theory holds water but it doesn't
apply to every single engine.
I personally have had many engines with gapless second rings and I never had a
ring flutter problem.
- Alright so on that basis then, what would drive you to choose between a gapless top
ring or a gapless second ring?
- Again simply efficiency on the intake stroke.
If I'm going to do a normally aspirated engine, I'm looking at a gapless top ring.
It just simply draws harder on the intake stroke.
I want to get that additional power.
If it's a forced induction engine, they both work equally as well.
Gapless top ring or gapless second, you'd be amazed at how many big horsepower
blower turbo cars that have gapless second ring, their function, they're not
trying to draw harder on the intake stroke, they simply want to eliminate that blow by
they want to eliminate that contamination, especially on alcohol engines.
Getting all the fuel into the engine though 'cause that fuel's going to break that oil
down very very quickly and it's going to cause a lot of wear problems in the engine and
ring seal issues.
- Is there also a consideration around the heat generated, obviously the top ring gets exposed
to more heat than the second ring, is that another consideration with these blower
or turbocharged engines with using a gapless second ring over a gapless top ring or not
an issue?
- No not really an issue, where the gapless top ring really helps in those kinds of,
what I'll call dual purpose applications especially, the power tour, drag week,
you guys do that same stuff.
These engines where we want to be dual purpose, I want to have 40 pounds of boost
or I want to be able to throw 1000 shot of nitrous on it but 99% of the time I'm not,
I'm just driving it.
So now I can gap the ring huge, 40, 50 thousandths, it doesn't matter, it's gapless,
put it in big and drive it, just enjoy it.
When you do use the power adder and really step on it, you've got enough end
gap for the ring to expand and not butt the ring ends 'cause the whole key as
you just said earlier when you started, was about butting those ring ends.
You run that ring too tight, as we say, everybody knows about it.
Little loose, nobody knows, only you.
- Now if we just talk about conventional rings for a moment, we've also seen,
at least over my career, 20 plus years now, the ring thickness, ring width has sort of
gradually reduced over time and there can be some advantages with that in terms of
ring seal, can you talk us through how those thinner rings can help?
- Well certainly and what I'm going do is I'm going to grab a prop right here.
When we're looking at the rings, we talk about the thickness, not only are we
talking about the axial height, we're talking about the radial depth, inside
to outside edge.
So we're reducing the rings to get rid of friction.
Everything is about friction reduction, if we can come with the materials, which
we have, that allow us to use that thinner ring and still survive the heat because the
heat is the enemy, if it'll handle the heat, how thin can I go?
As I reduce these dimensions not only am I reducing the force that it puts
on the cylinder wall but as I reduce this radial dimension, I'm reducing, I shouldn't
say reducing, I mean increasing its ability to bend and follow the bore.
As that cylinder can move around, especially in today's aluminium blocks
the rings have to follow.
Rings really don't like to bend and follow bores, they want to hold the shape that
they were made with so by reducing that radial dimension, it gives the ring much
more ability to flex and follow the bore.
- I think it's important to mention that while we may consider that our bores are round
when the engine's machined and often that's not even the case.
Certainly with some of the aluminium blocks when they're faced with very high cylinder
pressure, they'll be very very out of round and that's where getting that ring to follow
that bore irregularity can help seal?
- Absolutely, as the engine heats, again, aluminium blocks, not a lot of people have
done this but take that aluminium block if you're really into this thing, put it in a
big oven and heat it up.
Measure it cold. measure it hot, you'll be blown away at how much that block
moves, how much it's grown and how much it's grown out of round.
So everything we can do to improve that ring seal, to give that ring that ability to
follow that distortion, is going to improve that ring seal and at the same time,
drop that friction.
- Now you also mentioned there with the thinner rings is the ability to handle or
get rid of the heat out of the ring and we've heard issues with micro welding of
the ring to the ring grooves in the piston.
Where's the limiting factor, is it down to whether we're talking about a aspirated
engine or forced induction or the usage of the engine or the fuel, what's the considerations?
- Yeah micro welding can occur from a few different things.
One and a lot of people don't think about it is simply debris.
Dirt, rust, a lot of people don't pickle their engines when they're going to sit.
Especially in a humid environment, alcohol based engines, that attracts moisture,
attracts rust horribly.
You'll start to get some of that debris in there and that debris when it starts on a cold motor,
it's going to lock that ring up, it's going to micro weld it, it's going to create a hotspot
in there, that's one thing people have to look at.
Overly rough cylinders will do it, if you hone a really rough bore, that debris will get in
between the ring and the cylinder and the groove, the ring and the groove and create
a hot spot, that's micro welding as well.
But the other one is simply heat, tuning, micro welding will generally occur during
the break in cycle when the engine's fresh.
All the surfaces in this engine still have to be lapped together, the oil is the final
metal working fluid and the same things with the ring.
As good as we get the ring, as perfect as we make it, it still has to mate and
seat inside the ring land.
So if we've got any irregularities, high spots, hot spots, during that initial warmup, that
initial break in, it is possible to weld the ring which is an occurrence where the piston actually
sticks to the ring, not the other way around so it actually gets so hot it'll start to melt
the aluminium in the groove.
That's generally a fuel problem, too lean, too hot, not getting enough heat out of the
engine, simply cooling systems not efficient enough.
Those are the general reasons that will happen and it doesn't happen that often
these days.
There was a time where micro welding was a big problem, especially when they
changed to unleaded race fuels.
Australia, the Super Car guys, they bought it like crazy when they went to E85.
Simply not enough lubrication there so they had to look at the oils they're using,
the ring groove clearances and how do we get that heat out of the piston.
Some of them had to go to oil sprayers on the bottom side to cool the piston.
But once you address those issues, micro welding's not a problem.
- Alright so another topic I wanted to discuss here is the radial tension of the
rings and a lot of people think it's the tension of the rings pushing out against
the bores that does the hard work of sealing but the reality is really on the compression
stroke we're relying on the combustion pressure.
So a lot of people in race engines will move to a low tension ring.
The aim there of course is to reduce the frictional losses.
Can you talk to us a little bit about the pros and cons of a low tension ring pack?
- Well when we talk about low tension, it's not only the compression ring sizes,
it's the oil ring sizes.
So we have to look at what we consider standard tensions.
The word standard gets thrown around a lot and it's really kind of an industry faux pas.
A standard tension 3/16 oil ring is typically around 20, 22 pounds.
Using the same word standard on a 3 mm o ring's about 10 pounds.
So you've got a small Chevy that was designed with a 5/64 oil ring in mind.
3/16, 5/64 is 5/64 is 3/16 ring pack.
Engine was designed around that 20 pound oil ring and now we've put a 10
pound oil ring in and add a high volume oil pump to it where we're flooding
25% more oil in and so the tension of that oil ring just simply can't keep up so that's
the main thing to look at is to make sure you've got the right oil ring tension for
your application.
Street cars and racecars regardless of the power, have to do different things,
street cars have different jobs than racecars so we always have to look
at that oil ring tension, especially in a street car where we want to keep that engine
nice and dry.
So that's really the downside is keeping that engine nice and dry, finding the right ring
pack that's going to keep it nice and dry and give you all the friction reduction that
you can handle.
I've had engines, my own personal engine built with a very very thin top and second ring.
I wanted that bore conformability, I wanted that reduction in friction but I still didn't
go as low on the oil ring as some people do because I simply wanted a dry engine,
it's got to be happy, it's got to be dry, I'm willing to give up a couple of
horsepower to make sure my street car doesn't smoke.
- I think most people would probably be in that same boat as well.
Alright look if people want to find out more about the Total Seal products,
where can they go Keith?
- Come to our website, totalseal.com and we've also just started a Podcast
so you can come to the Facebook page for Total Seal, Twitter all those, we've
got a new Podcast, please sign up, follow it, we're interviewing, like you're interviewing
with me, we're interviewing and dealing with Joe Costella and the legends of this
industry, we've done Jason Line from the KB Racing Team, multi time pro stock
champion, Pat Musi we just did one with him and we're going to do a little
bit of everybody from sprint cars to Indy Cars to Porsche restorations so
we're kind of going to be doing a little bit of the same thing you guys are doing.
- Alright thanks a lot for your time there Keith.
- Really appreciate it, thank you I appreciate you having me.
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