- With 1200 horsepower at the wheels, at around 35 psi of boost pressure,
and the ability to rev to over 10000 RPM, the Integrated Motorsports R34 GTR
is probably one of the most powerful RB powered Time Attack cars,
anywhere in the world.
We're here with Peter from PMC Race Engines, to find out exactly
how that engine's put together and how it makes that sort of power.
Now Peter those sort of power levels aren't unheard of.
But normally we're probably hearing about those sort of power levels
from drag car that only needs to hold together for six to maybe eight seconds
at a time.
You've got a car here that needs to perform for a lap that can last
up to about a minute 30 around Eastern Creek here.
- Hopefully.
- It's a completely different kettle of fish really.
So can we start with the engine block, what have you got in this car?
- Well we use the Bullet billet block.
We've got a custom 77.7 mil stroke crank.
We use an aluminium forged rod from America and a billet piston
to go with it.
We run about 10.8:1 compression ratio.
We run it very tight, we're trying to get it as efficient as possible.
And the Bullet's so much better than any other way of doing it because
A it's 40 kilos lighter and it's so much stiffer.
So we don't have any sealing issues, it seals the bore so much better.
- Before we go too much further, 'cause there's a lot of great stuff
that you've just gone into so I wanna just actually go back and unpackage
some of that.
So let's start, so you're using the Bullet billet aluminium engine block,
little bit of a mouthful there.
And we're seen these come online over the last few years and of course here
at World Time Attack in the open and pro class, the billet alloy blocks have
become the go to, really if you wanna make that power reliably.
So let's just go back over the advantages there, you've obviously said you're
40 kg lighter, that's a world of difference for a start but we're more interested
in the strength aspect, so head gasket sealing is real big issue
with these turbocharged engines at high boost levels.
Where are the advantages from that alloy billet block when it comes to
sealing the head gasket?
Making sure that that head is sealed tightly under high boost.
- It's all to do with how thick the deck is.
At a minimum 14 mil thick and that gives massive rigidity.
So the block doesn't move around under load and it's got a very thick
sleeve in it.
So it's very stable with a big half inch stud, massive clamp load.
So with a sealing ring like from Nitto, Nitto head gasket,
we just don't have the head gasket issues anymore.
- So you've just also mentioned there the bore.
So with an alloy block, obviously we're not able to run the piston rings
directly on that raw alloy finish.
So these run a ductile iron sleeve that then gets pressed into the billet block
and those give you some advantages as well, the thickness of those sleeves
is greater than the stock bore?
- Absolutely they're much stronger material.
You can bore them out to 88.5 capacity's always good.
The structure of it is just not gonna crack.
And if there is an issue, it's easy just to pop it out, put a new one it,
deck it, and back to work.
- I think that's something that's overlooked, obviously sometimes things happen,
in motorsport, particularly when you're pressing an engine this hard,
and here unlike with a stock block where you'd basically be forced to scrap
an entire block if you have a problem in one cylinder,
you can replace individual sleeves?
- Yes that has happened to us.
We've had a lean out, absolutely torched it and within hours we've popped
the sleeve out, put a new one in, decked it, bored it, honed it,
back into service.
I've actually built this one in 12 hours from scratch this week.
So it can happen but you cannot fix a steel block like that.
So it would be thousands of dollars to fix another one where this one
was $1000.
- Alright so another aspect you mentioned there is the fact that you're running
an aluminium conrod.
Now typically the alloy conrods is more something we would see in a drag racing
application, they have some problems as well around their fatigue life
which doesn't really make them well suited to circuit racing.
But of course Time Attack is a fairly unique type of circuit racing.
Give us your run down on why you've gone to that alloy rod and what
the advantages are as you see them.
- Well first of all they're about half the weight.
We use the Bill Miller rod from America which is a forged rod.
And they're so good on the bearing, we just don't hurt bearings,
they're just such a cushion because of their aluminium construction.
Because of that we get much better bearing life and we can really put
the boost in without fear of hurting a rod.
- I think particularly in drag racing terms as well when these engines are being
run right on the edge, if the engine is run briefly into detonation,
then the alloy rod tends to absorb or cushion that impact from the
detonation which is what you're saying there, you don't end up hurting
the bearing as a result.
And the bearings on the big end of these engines are relatively small,
given the power you're making?
- Yeah they're very small in an RB, we're undersize for what we really are.
So even with the very high end Carillo rod, a slight bit of detonation,
the bearing will fall out, no way to hold its shape.
With the conrod, the Bill Miller rod, we get away with that.
So the tune, we're on the ragged edge, we're pushing the poor little 2.8 all the way,
massive revs, massive boost, and it's more than seven seconds,
it's like a minute and a half and sometimes we have to go around again.
So the temperatures involved are much greater.
So the aluminium rod's the only way we get away with that.
- Alright now in terms of this engine being 2.8 litres, obviously you've got the advantage
with that billet block, but the rod to stroke ratio of the stock RB26
isn't great.
Wouldn't typically be a rod to stroke ratio that would lend itself well
to 10000 odd RPM.
Have we done anything there with the rod length to try and aid that rod
to stroke ratio?
- Not really, it's a little bit hard to do much with it because we're trying to keep
the block as small as possible and as light as possible.
When you go to the 30 block, it lifts everything up, it's not so good
for weight distribution, but we also have harmonic issues with the longer block.
So the 2.8 is about as much stroke as we would go and there's not much
we can do with that stroke ratio.
It's not great but we get away with it.
- So essentially you're saying you've compromised the rod to stroke ratio
and you haven't gone to a tall deck block.
- Absolutely but in the future we are actually making a custom RB block,
which is about 20 mil taller than the 26 block.
And that's the biggest compromise we'll make for height and we don't want
to lift that motor much more.
It's all about making that thing go around the corner here.
So that's the reason.
- Alright now you also mentioned that you're running a billet piston which again is
not particularly common.
So where do you see the advantages of a complete billet piston over
an existing off the shelf or even custom built forging?
- It's just being able to actually make it strong enough to do what we're doing.
And also make it easy enough to actually be available because we move them around
a fair bit to get the shape that we want.
And there's no off the shelf piston that can do what we wanna do.
It has to be strong enough to do what we're trying to do for lap after lap.
So we custom make it for the compression ratio, we have holes in the ring lands,
that press rings out, there's all sorts of stuff we're doing.
- Now you were just talking about there, holes in the ring lands,
so just let's go into that, so you're using a horizontal gas port,
can you just tell us how those horizontal gas ports help?
- Yeah we're just trying to seal that ring up as much as possible.
With much load force on the ring to push it onto the bore.
And we actually start creating a vacuum in the sump because we're not
having the blow by issues that we were once before.
- So that leads me onto the rest of the bottom end and another area
where the RB26 is well known to have its share of issues is in the oiling
department.
Now obviously in this sort of application, you go straight for a top shelf dry sump
lubrication system.
Are there any other tricks or changes that are necessary around getting
the RB bottom end reliable in terms of oil control?
- With the billet, because it's so much stiffer, we're not having the bore
flexing that we would normally see in a 26 block.
So we negate the blow by which is most of the problem that we see with
the oiling system.
There's no, the oil just can't get back to the sump because it's got so
much air going past those holes.
So with the billet, it's not so bad because we can draw the oil
out of the head via a stage in the pump and we don't have those issues
so much any more.
- So basically when you can reduce that blow by, that actually gives you
a significant improvement in the oil control capability.
- Yes and also a significant horsepower advantage.
So we chase everything we can, especially at this level where Matt's
trying to win this race.
We're doing 300 plus ks down there at 10000 revs so we need
a very stable block.
- Alright let's just move onto the cylinder head here because obviously the bottom
end really is just there to give us capacity and actually remain reliable
but it's really the cylinder head, coupled of course with the turbocharger,
that is there to flow the air in and out of the engine and make the power,
so what have you done there with the RB26 cylinder head?
- The 26 head is my thing, I port that, that's my main job.
It's got beryllium seats in it, it's titanium valved.
Some of them, most of them we use the Ferrea super plus valve,
and they'll spring package.
Significant boarding on the inlet side and a lot of shaping on the exhaust.
Plus we do a very open chamber design to get rid of squish because they just
cannot handle that squish.
- Now let's just talk about that, for those who aren't aware,
particularly with the RB26 head, there are some significant squish pads
which in OE terms are generally there to help try and move the mixture
formation in towards the spark plug.
So where do you see the disadvantages of those squish pads and why do you
modify or remove them?
- In a factory road car, they only have seven or eight psi,
and they gotta meet emissions, and they try to make that event happen
in a very tight place to get good emissions and decent power,
but when you start pushing the things with 30 pounds of boost and
1000 plus horsepower, that fuel control and the burn is critical,
and we just can't get away with it with a closed chamber.
We just can't get it detonation sets in and we lose motors all the time.
- The cams in this of course as well, another key to the air flow.
Can you give us some insight into what you're doing there, what the specs
of those cams are?
- Yeah actually they're getting smaller all the time.
We're actually dropping them, as you can see they're going past
10000 revs and you think wow they must have big cams,
but they're very small.
We're only going 265, 272, and they're revving to 10 because
they've got such a big, a modified inlet bore.
And we're running a very large single throttle body plenum.
And all that air adds up to big revs, you don't need those camshafts,
you don't wanna waste that energy out the exhaust.
You have to pull it up a quarter and it's gonna snap into action.
So we don't go big on the cams anymore.
- Now in terms of the valve train as well, the RB26 cylinder head is already
a direct bucket valve actuation which is great for high RPM.
Is there anything needs to be changed there with the bucket operation
for reliability at 10000 RPM?
- Yeah we have to DLC coat a bucket and we remove the factory shim,
and we make a longer valve and then we tip it to length,
so we get, so we move it away, a shimless valve set up and it's the
only way we can limit that 10000 revs on downshifts and upshifts,
with a sequential gearbox.
- So just moving away from the shim, which means that there's absolutely
no chance of reliability problems with that shim making its way out,
you've just got a one piece bucket, but of course adds to the complexity
of actually setting your valve lash?
- Yeah certainly does.
It's a fairly in depth sort of process and we work within micro millimetres
to try to keep things exactly in time.
Like two thou too tight can change your degrees up to 12 degrees
in timings so we really keep that under control and it's a very lengthy process.
It's an expensive head.
- Well look Peter it's an amazing piece of engineering, it's an amazing feat
as well producing that sort of power for a Time Attack application.
We've still got a couple of sessions to go today and we know that you've had
a few problems so far this weekend.
Everything seems to be lining up for you so we wish you all the best
and hopefully the car can put down a representative time in the two sessions.
Thanks for the chat there Peter.
- Thank you very much and I really enjoy your show, thank you.
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