- Traditionally, getting really high horsepower and reliability out of a Subaru 4 cylinder engine
has been somewhat challenging.
And we're here with Leigh from Deshele Performance Engines to talk about what
goes into a reliable Subaru engine when you're punching out perhaps north of
600 kW.
So for a start Leigh, can we talk about some of the known issues with the Subaru engines
and particularly I know they're very prone for bearing issues, particularly the big end
bearing, that seems to be a common problem with them.
What is the reason behind that and why do people have so much trouble keeping them
together?
- Mate I think it's probably down to maybe the bearing size, the oil pump which now we
can upgrade, we run higher pressure.
I actually modified the oil galleries in the block to feed the mains with the ones that
do lack oil.
I think that and setting up the clearances, definitely.
We have got a couple of bearing mods that we do do which has dramatically helped.
- Now just to go back for those who maybe aren't aware of what we're talking about,
the narrow bearing, so this is an issue with the Subaru engine design.
It's a horizontally opposed boxer 4 cylinder and it is a very short engine
front to rear so if we look at a crankshaft, there's not a lot of material
for the big end journal so this is what we were talking about, the bearing is
physically much narrower than a typical in line 4?
- Yeah it is, definitely.
- OK so therefore the issue is the bearing can't do such a good job of supporting the
load when we start running higher power?
- Yeah higher power and also with RPM I started to really notice that that also had
a dramatic effect on the bearings.
- Alright so the narrow bearing, that's one issue but you've sort of also talked around
some of the other areas there that sort of go hand in hand, it's not a one size
fits all fix, there's a few elements to it.
I mean most people would be aware, particularly on a race track where you're
starting to get high lateral G force, the factory sump can be a problem and
then you're not actually getting oil to the oil pump so are there solutions for that
or is the factory sump up to task?
- Look it is up to task, if you're drag racing, roll racing, it's fine.
If you are going around a circuit it does definitely become a problem.
Mainly under braking definitely they see that.
- And for those again who maybe aren't joining the dots here, if the oil pump can't
pick up oil and suddenly it gets a lung full of air, it's pumping that air through and
all of a sudden we get metal to metal contact between the crankshaft and the
bearing and that's game over so let's now talk about the oil pump which is that
next sort of element in the chain there.
So what are the problems there with the factory oil pump that you're trying to resolve?
- Look mainly supplying enough oil because the block does row a lot, a lot of people that
do build the motor tend to set the clearances up too loose on the mains, that is one of the
main critical points that people go wrong.
We actually tighten them up and when they get hot they expand.
We go a bigger oil pump for more flow, probably running a good viscosity oil
and it seems to have definitely eliminated, if you do have pressure and pick up problems,
you will eliminate that by tightening those.
- The factory oil pumps though, no problems with the EJ in terms of the pump actually
breaking which we see with a lot of factory pumps?
- It's very very rare, I hardly ever see it, I think in my whole time of building engines,
I've only probably ever seen 2 break and they've been high kilometres.
- OK so that pump's there to increase the physical volume of oil and by increasing
the volume of oil, obviously the viscosity plays into that as well but that's going to
help improve the oil pressure.
The aspect you just mentioned there with the block growing and the clearances,
so quite often if we look at factory clearances for a production engine and we're taking
that engine and maybe we're going to double the power, it's a reasonably common trend
to build the engine on the looser side of the factory tolerance or maybe even
slightly outside the factory tolerance with the fact that the crankshaft's going to flex
and we want to stay away from metal to metal contact so you're saying that that's not the way
we want to go with an EJ?
- No definitely not, with such a short crankshaft, I don't think you get the whip
or the flex in it like you would if it was say a 6 cylinder or something a lot longer.
- OK so I think that would be a common modification for those who are coming into
the EJ engine with no previous experience and an area that's where potentially they
are going wrong.
- They tend to run, I guess you look at old school V8 type theories where one inch per
journal, one thou per every inch of journal but with these yes on the big ends but on
the mains no, definitely tighter, you've got to pull them back to factory and
they're a lot more successful with that.
- Now the other element there is that the EJ series engine or any boxer engine for that
matter, physically it's trying to tear itself apart when you're making higher power
and I mean I've seen my fair share of these engines in pieces where there's really
obvious signs of significant fretting between the two halves of the crank case and that fretting
is basically where we know that we're getting relative movement so everything's flexing
and significantly more than you'd maybe think so how much of an issue is that and
are there solutions for that?
- Look yes it does happen, we have made our own case stud kit which has worked very
very well.
We've seen, when the boost comes on, oil pressure drop off with factory case
bolts when the cases start to pull apart.
When we put a new stud kit in and it's obviously a lot higher tensile,
it does solve that problem.
The fretting you will get a little bit of still just because it's just basically a
design in the engine but our case stud kit has dramatically helped hold oil pressure
at high power.
- Now when you say that oil pressure is dropping off at high power levels,
so I'm guessing here that it's actually moving the block apart enough that it's
just creating an internal leak?
- Correct it is yeah it's pulling the mains apart.
- Now of course when you're dealing with an alloy block, when you go to a much
stronger stud material or go to a stud from a bolt, something that you can get a lot more
clamping force, the knock on effect of that is you can end up and almost certainly will
end up distorting the main bearing tunnel so I assume here line honing's an absolute
essential?
- Yes definitely, for sure, it's a must, you won't be able to get the clearances right without it.
- No I'm interested in your take on this because I've actually just had a conversation
with one of our members on our forum and whereby what they've done is basically taken
a set of ARP studs and the machine shop has basically undertorqued them compared
to ARP specification in order to not get the distortion.
And I know that this is a reasonably common move, I've seen this in the Honda world as well.
Certainly from my perspective, I don't see that that's a good solution, if I'm going to
use an ARP stud, I want to use the manufacturer's torque so is that worth doing in any way shape
or form in your opinion?
- Not with them because I have actually tested their studs and unless
you do get close to what they recommend, you're not going to have the clamp load.
Once it gets hot and things settle, they will be loose and you'll go backwards
so I would recommend, if you can and you don't pull threads out of blocks and
things like that, that is not an issue, definitely stick to their recommended
specs if you can.
- Glad we cleared that up, I mean from my perspective if I'm using a part from a
manufacturer, makes sense that I'm going to use their recommendation.
Another elements I wanted to talk about with the EJ series engines is getting them to spool
turbochargers and this is, again I've tuned a lot of 4 cylinder engines, EJ, FA and obviously
every in line 4 cylinder that's popular from Japan and if we take a 2 litre, let's say a
4G63 and we compare that to a EJ20 and we put the same turbo on them, maybe
something reasonably large, generally all things being equal we're going to see
the EJ will spool quite a lot later.
Now is this an element of the engine's physical design or is this due to the
exhaust manifold design being that generally that has to be longer on an EJ.
- Definitely, I think it comes down to the exhaust heat, with a longer manifold it's
obviously not going to be as hot by the time it probably gets to the turbocharger
so you may be loosing there.
You're filling those pipes up and then always on a Subaru, you always have very long
intercooler piping when you've got a front mount so those things combined I think are
probably working against you in that regard.
- Alright so we've got a bit of detail now on the background of the engine and some
of those problems and how to overcome them, I'm interested in diving a little bit
into the car that you've got here behind you, so this is your drag car and from my,
if my memory serves correct, you said it'd run 8.80, 161 mph?
- Yes that's correct.
- So that's pretty quick for a Subaru, obviously there's faster out there in the
world but definitely it's no slouch.
Can you talk to us first of all about the engine combination you're using with this?
- Sure so it's an EJ25 block, fully closed deck, 14 mm head stud version.
We actually run a 2 litre 75 mm stroke crank.
We put a longer rod to help with the harmonics which has done that significantly.
Like actually better than what I thought.
The engine has gone to 10,300 with a steel rod quite a number of times now which
has surprised me and it's still going and it's got very good oil pressure and everything's,
head sealing is perfect, just really holding its own, it's surprising.
- 10,300's definitely no joke and for those who maybe aren't fully up to speed with
all of the different Subaru engine combinations, that 2.5 block with the 2 litre crank, what's the
capacity coming out to?
- 2.34 litre basically.
- So it's gone 10,300 or whatever you just mentioned there in terms of maximum RPM,
what do you try and shift it at typically?
- I try to shift around 9500 maximum but sometimes I get carried away.
- Can you talk to us about the turbo combination you've got on the engine as well?
- Yeah so it's a Precision 7675 with a single entry 0.94 housing on it.
It's currently on about 45 pounds of boost and we're estimating it would be about
650 kW at the wheels on a Mainline chassis.
- So estimating, so you haven't tuned it at that power level on a dyno?
- We have with converter, it only shows about 500 but it's definitely making more.
- Alright well we'll talk about the transmission because that's an interesting aspect,
in a moment but before we move on from the turbo, you've got a reasonably unique
position for that turbo, is this about trying to minimise the runner length which we were
just talking about?
- Yeah definitely, shorten the intercooler piping up and yeah just be a little bit
different I supposed from other people, but mainly yeah definitely shorten the pipes
up a fraction.
- OK so we'll move onto the transmission because particularly with the GC8,
that was the Achilles heel of that chassis was the factory transmission.
Obviously there's aftermarket sequentials, there's gear sets for the factory box and a lot
of people go to the 6 speed as well which is in its own right a pretty strong combination,
you've gone quite a different route with this with an automatic so can you talk to us about
your reasoning behind that?
- Sure so when we started playing around with the car, I went in the drag racing route
of things so, just that was the way it went and I though the most reliable way to go
for drag racing and to get the best times as to stick with a Subaru automatic gearbox.
So we found one from an SVX and we used that as our base to start with and just
modified, modified it and got it quite good.
- What I've seen with a lot of people that have gone down the factory auto route
is that there's definitely some advantages there in terms of not upsetting the car and
the traction, particularly during the shift, generally it's a little bit easier on the
componentry as well with the initial hit getting off the line but I also see a lot of
people spend quite a few seasons working through the inherent problems and finding the next weak
point in the box, is that the same situation you had?
- Oh definitely there was actually times where I came close to giving up on it and just stuck
it out and just happened to fluke a couple of things that we modified that took it to
another level.
We've played around with the line pressure, we're up at 260 psi line pressure at the moment.
It's helped a lot as well with getting it more reliable, having that extra clamp.
Obviously the clutch is wider band, it's definitely been a learning curve for sure.
- In terms of getting the car off the line, are you using anything like nitrous to
spool the turbo because that sort of tends to become the next problem with
a large turbo, small capacity engine with a torque converter.
- Yeah so we're using 75 shot to bring it up to it, we're leaving it around 5000
with a trans brake and it stays on, the nitrous stays on to the end of first
gear and turns off for the rest.
- So once you're out of, the end of first gear, basically the turbo's got
sufficient boost to be able to sustain itself.
- That's right, correct.
- And in that regard just with traction etc, are you using a boost control strategy as
you go down the strip or is it all in and that's it?
- No it's just all in at the moment and funnily enough it's actually starting to lift the front
inside wheel off the ground in second gear so yeah we're just letting it have it,
whatever it'll take.
- Alright look great to find out a little bit more about the car there Leigh and
appreciate your time talking us through the Subaru engine.
Obviously you run your own engine building specialist workshop, if people want to find out
a little bit more about you, where can they go to?
- Just desheleperformance.com.au and yeah we'll have engine packages that we do online
and what we kind of specialise in.
Sometimes there's a few articles on there of what's happening.
- Perfect, thanks a lot for your time Leigh.
- No worries Andre, thank you.
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