- Traditionally when it comes to choosing a platform to build a Time Attack car out of,
the Subaru WRX or STi hasn't been a popular choice but we're here with Liam who's the owner
and driver of the Car Mods Australia GC8 WRX here at World Time Attack to find out a little bit
more about what goes into building a competitive Subaru.
So I guess for a start Liam, why did you go down the patch of choosing the Subaru platform?
- Well I'm guilty of being a bit of a Subi fan.
We've previously run a 4 door GD and we had good success developing that and the next step
was just to go to the lighter weight option and move into the coupe.
- So this is a GC8 and it's the two door type R coupe that you started with?
- Yeah so it was just a regular old import back when you could afford to buy an import.
And yeah basically just stripped it down and created the starting point from there.
- OK so in terms of that starting point, what are the sort of weak points if you like of
that GC8 chassis that you knew that you were going to need to work on to make it competitive
in open class?
- Yeah so I think the initial point was obviously focus on the weight within the rule set, that's
the biggest advantage that you can gain from it, a lot of the heavier, higher horsepower cars
are sitting in the sort of 1300, 1350 sort of weight, that range and obviously not being, running an
EJ and not being able to put out as many ponies, we've sort of got to compensate that.
So yeah the first point of call is strip whatever we could out of it, get the right lightweight
panels on it and use that as the platform to work from.
- Alright so there's a lot of carbon going on I can see that, what did you actually get the
weight down to?
- Yeah so the weight, it came down to about 1190.
- Is that without driver?
- Yeah without driver and that's in circuit format so we build the car as a circuit car.
Which happens to obviously just work pretty well with the open rule set, with the addition
of some of the bolt on stuff, the aero stuff.
So that was a pretty good outcome, we definitely knew that there'd been coupes, get down to 1150
before and I'm a good friend of Alex from GotItRex and so obviously there was a little bit of a
benchmark there with the weight that they got theirs down.
Theirs being Pro Am they got a little bit more out so we were pretty happy to come in at under
1200 as a starting point.
- Alright so weight, obviously a big factor there, we've talked about that but obviously power,
particularly here at World Time Attack, you need a lot of it so the Subaru engines,
and I don't want to annoy any of the purists out there who love their Subarus but they can
be a problematic engine to extract big power out of.
So can you talk to us about the engine combination, what have you got in there?
- So I can now proudly say that categorically we've got the recipe now for a high powered EJ.
It's taken a think 5 years and Brad Sherriff, he is just an absolute guru and we worked over, I would
say the last 4 or 5 years, changing componentry, making sure we've got the right bits and pieces,
there's lots of combinations out there that all the Subi loves will know that are known to make
good power but we're going to make it reliably, consistently and over a circuit season.
We've now done that twice, it is a complete mish mash of the best products on the market
and they certainly aren't all, they don't all originate from Subaru, there's a mixture there.
The two main components I would say is the sealing solution.
Naturally everyone knows that keeping your heads down is important once you start feeding
some boost in.
I think there's probably, actually there's probably three components right.
So the second is obviously having a big enough turbo to make the power and the right bits inside
but then the third is the tune.
So you can't feed all the power into it early and again, Brad's just an expert, he's the best
in the world and we'll feed it the best part of high 30 pounds of boost at the top end
and it just loves it and it's done that consistently through a circuit season.
- Alright there's a bunch of stuff that I want to go back and unpack there.
So you're absolutely right, the head sealing is such a problem with just about any turbocharged
engine, the EJ's not on its own there.
Now there's a variety of solutions in terms of better head gasket materials, sealing rings,
o rings, head studs, can we get a little more information on what you're actually using there
or is that some secret squirrel information?
- No look I mean it could be, for someone else it could be secret squirrel but I'd like to share it,
purely because now we've had such great success, I always feel frustrated and sorry for people who
are constantly lifting heads and having problems.
So we do use an IAG sealing ring, basically a fire lock gasket kit, hands down the best product
in the business, we've fed it well into the 40s in boost and in combination with the 14,
a head stud, a big head stud, you're laughing.
- Now there's a lot of terminology that's thrown around with fire rings and o rings and sealing
rings and some of it sort of crosses across so when you say a fire ring, I think that was the term
you used there, are you talking about a ring that actually locks into the cylinder head
and seals against the top of the bore?
- Yeah so it's effectively a metal ring which is I would say, to dumb it down, 'cause again
a lot of my terminology's pretty layman but it's effectively taking the difference, any sort of
movement that there is between the top and the bottom end, it allows the ring to take a
bit of the movement instead of compromising the gasket so we crank those, the studs down really
hard as per the spec and the ring does all the work if there's any fluctuation.
- OK so these are off the shelf products from IAG?
- Yep they are.
- Alright, got a little bit loud out there so we've just moved into the garage a bit deeper.
Let's just go back to the base engine that you're running there.
There's obviously a lot of different engine combinations, what are we talking here and
what is the capacity?
Yeah so look we've landed on a very specific build which has been tried and tested and it
starts with the 2.5 litre engine.
And basically it gets a really good crank, the key component is a custom piston from
Colin at Special Piston Services.
And yeah basically we matched that with the head with the right valve spring and right
valve spring pressures to handle the shift cuts and paddle shifting and that's basically
the nuts and the bolts of it.
- OK so nothing too tricky or anything particularly unusual there, not really reinventing the wheel.
- No so we used a 272 cam, basically anything bigger, you make more horsepower but you've got
a more aggressive load.
So we try and make it nice and easy on the buckets and everything's really happy,
it'll put out over 500 kW all day every day.
- And you mentioned high 30s there, maybe low 40 psi?
- Yeah absolutely right in the top end so the key again to Brad's strategy, the car's
effectively torque mapped so as a lot of people will know, feeding a Subaru a lot of boost early on,
that's a recipe for lifting heads so Brad's pretty smart about his tuning and he's pretty
leading edge with that stuff so we make sure it goes in, all the boost goes in at the right spot.
- And that's really about just managing the peak cylinder pressure because of course it's the
cylinder pressure that will actually tend to lift the head, even with the right sealing
system that you talked about there.
- Yeah absolutely so it's just about making a compromise with RPM and how high are you
going to rev the thing.
We know that that's definitely a factor in the deterioration with lots of use, lots of laps so
we try not to rev the thing over 8200, we could go further and you would naturally make more
power but that's a happy medium for us.
- One of the trade offs we do have to make there is in terms of peak power vs gaining a wide enough
powerband to make the car usable because this isn't a drag car and even with the paddle
shifted gearbox which we'll talk about shortly, you still will end up a little lower in the RPM,
particularly through some of the tighter corners so what, obviously the 2.5 litres there is going
to help but what sort of boost threshold do you see, where in the RPM range I should say are you
seeing usable boost?
- Yeah so we run a big Precision turbo, again another really key component to the package.
And we try not to put too much into it under 4500, it is very drivable though, that powerband
from 4500 through to 8200, it's big, if you keep it in the right gear, obviously having the
paddle shift allows you to do that and yeah it's zippy but with the right gear ratios it's all
pretty good.
- Alright another area that we see a lot of problems with street driven Subarus taken to
the racetrack, maybe for the odd track day is around oil control and certainly I can only
imagine the sort of lateral and longitudinal G forces you're able to pull given the aero
package on this car are significant so what have you done around getting a reliable oil
control system?
- Yeah so since day one we've used a Daley dry sump kit.
Hands down the best in the business, we've had no issues at all.
There's a lot of talk on forums and on the internet about people running wet sumps at the track
and it is just a recipe for a disaster, don't do it, you need a dry sump.
Like you said, you pull a lot of Gs, there's a lot of tight twisty turny, powery sort of
corners and it'll just slosh everything around so that's how we keep it safe.
- I think it's something that enthusiasts do need to consider, obviously there's a pretty
big upfront cost in going to a dry sump system, that does need to be factored in
terms of if it saves you one engine, it's probably also paid for itself.
Now I'm not saying it's the right option for everyone but certainly at this level it's
a sensible option and one that really as you say, there's no alternative that makes sense.
Alright let's talk about the rest of the car and you've talked paddle shift a couple of times so
what is the actual gearbox in the car?
- Yeah so it's a Samsonas gearbox.
Over the years we've had some trial and error with other gearboxes and we've landed on
Samsonas and it's been fantastic.
The shift is really smooth, it's nice and easy on the box and no issues at all.
- Now one of the factors obviously with the Subaru platform is it is 4WD so that comes with
a centre differential and that gives you the ability to also control the torque split front
to rear.
How important is that for a race application, circuit application?
Obviously we're not on gravel here, it's not a rally car so is it still important on tarmac?
- Yeah absolutely, we use the full MoTeC suite across the car and that includes the diff controller.
It's really important for us, trying to be able to pull the car out of corners with the front and
then drop the front off as we get going, it's crucial, naturally that's the area for us to
shine a little bit, not having the big ponies down the straight so the cornering's everything and
controlling the power and the diff, yeah that's the key.
- In terms of the rest of the electronics package in the car, can you talk us through what's
installed?
- Yeah so we're running PDMs, like I said everything MoTeC.
We've got the paddle shifter there.
- That's all controlled via the MoTeC ECU as well, not its own standalone controller?
- No it's not standalone and yeah that's kind of it.
- And so MoTeC M150 is the ECU?
- Yeah MoTeC M150, MoTeC dash as well.
- Now is that running production firmware?
Because this is one of the things with MoTeC M1 that a lot of people probably might not
be initially aware of is essentially you can think of it as a black box and it really, the functionality
is going to depend entirely on the firmware and you sort of alluded to Brad Sherriff's
torque model.
Is it safe to assume therefore that you're running some of his firmware?
- Yeah so Brad Sherriff at Racetech Performance, he's the key to the tune and that torque mapping,
that's all him.
And certainly something that we keep pretty tight to our chest, it's something that
customers can talk to Brad about but it's really important for us.
- Alright another thing that's really important at World Time Attack and we've seen this
evolve over the years we've been coming here is the aero packages and yours is obviously
nothing short of extensive.
Can you talk us through how that package was developed and how you've gone about testing
and developing it?
Testing and validating it I guess.
- Yeah so we've used Freddy from TopStage with his V3 product on the previous car,
on the 4 door.
We've transitioned that over for this, for the circuit season.
And basically we're using now a fairly experimental front end, we've added a bigger
canard and we're making significantly more downforce with a bit more drag as well.
So we're working through the process, particularly at this practice and the last week of just trying
to get the right balance, we've added the gurney on the rear which is, we've got full car balance
now which is good but we're just trimming little bits off the canard to make sure that
we're not having any detriment in the top speed down the straight unnecessarily so that we balance
that with the speed we need for turn one.
- OK so again, a bunch of stuff I want to kind of dive into a little bit more.
So first of all, we talked off camera before, obviously validating this stuff, what is it
actually doing and numbers are thrown around all over the show but we don't have the
benefit of wind tunnels to really properly test this.
But you've got shock or damper travel sensors on the car so shock travel, shock position
sensors, can you talk to us about how you can gather some sense of what the aero
package is doing base on that?
- Yeah so we use the potentiometer and what we'll do when we go and practice or what Brad
will do is we'll effectively map what the pot is doing under different conditions.
So we can see, static where it's sitting and then we can see how much we're getting into
the damper with the aero load on it based on that measurement from the potentiometer.
- So in other words, look at what it's doing static when the car's not moving, maybe look
at what it's doing in terms of how far they've compressed it, let's say 200 km/h, that's going to
give you a bit of a guide, I mean yes it's not 100% accurate but better than guessing.
- Yeah look there is a bit of suck it and see but it's done systematically so you're trying
to replicate certain conditions and then yeah basically look at those speeds and look at how
much you're into the damper.
- OK so another element you talked about is the new canards on the front which is a
Top Stage product and again off camera you talked about the fact that while there's a
huge improvement in downforce, I think you said it knocked your top speed by maybe 20 km/h?
- Yeah look the new package has definitely wiped a bit of speed off the top end down the straight.
Which is to be expected because we've seen a significant gain in the front end aero.
And so basically now it's just a matter of like I said, winding it back slowly so we don't put
the car out of balance, that we get enough speed down the straight to carry through one, to give
us a good time so that we've got good balance through one but also we're keeping the
pace up.
- And again you sort of, you briefly touched on this but how you're sort of doing this is actually
physically trimming material off the canard?
- Yeah so we've been taking effectively a measurement off the front canard and balancing
that with rear wing angle so that the car's still in balance and then having a look at
the data and seeing how the speed's improved so for example the last small trim we made,
it made about a 10 km/h difference down the straight and really we didn't suffer with turn
one stability at all.
- And I think the other point you've sort of mentioned a couple of times there that it is
so easy to overlook and it's not just a case of going and throwing a big rear wing on the
car because yes that's probably going to give you a lot of downforce but it's going to create a
car that particularly at speed, it just understeers and goes straight ahead so that's what you're
talking about with that balancing the downforce on the front axle line vs the rear?
- Yeah look one of the big advantages in the development we've had with this car through
the circuit season and through Brad's expertise and using Murray's, they're
effectively an experimental 6 way damper, is that we've been able to balance having the
right springs in it, we've been able to play with wing angle.
We already knew the V3 package was good for 300, 400 kg and it's basically a matter of getting
the angles right and making everything happy.
- Alright look it's early on in the World Time Attack weekend, it's been great to get some
insight into this car and we look forward to seeing how you go through the weekend,
best of luck for tomorrow particularly and thanks for the chat.
- Awesome, thank you.
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