- One of the biggest killers of any performance engine is problems with
the lubrication system.
Maintaining a consistent supply of high pressure oil to all of the bearings,
as well as all of the other engine components is critical if you want any kind of reliability.
Of course when you take a factory road car engine and you put it on a racetrack,
with sticky slicks and you pull a lot of lateral G force, this can be problematic.
We're here with David Mountain from Mountune to talk about the development
of some of their oiling systems and in particular, dry sump versus wet sump.
So I think, David, it's fair to say that if budget is no constraint, if you want the
best of the best, you got to a dry sump lubrication system.
For those who aren't aware what that term even means, can you talk us through
how a dry sump lubrication system works?
- OK so basically the name gives you a clue, you're taking the oil out of the bottom
of the engine, you're putting it in a separate tank, somewhere in the car,
and what that means is that it's normally a tall tank where you can keep control
of the oil.
So you're always picking up oil, rather than picking up air which is what happens in
a wet sump.
So it's a much safer result for racing engines.
- Yeah I think that's probably a good place to just to back to.
The problem really with your factory road car sump is as you say, it's wet sump,
so that means the oil is stored in the sump, at the bottom of the engine and the
problem is when we've got very high lateral G force, cornering forces,
plus braking and acceleration for that matter, the oil can run away from the pickup
and you suck air and that's where you get problems?
- Yeah and also because the oil's in the bottom of the sump it's getting picked up
with the crankshaft, you get a lot of windage and aeration going on.
If you ever look at an engine on a dyno that has a perspex cover in the side of the
sump you just won't believe what's happening, it's scary.
It's just a massive through and there's only a little bit of solid oil right down the bottom
which is what you've got to try and pick up.
- Now that's a good place to point out that dry sump lubrication obviously is there
to ensure that you've got a constant supply of high pressure oil to the bearings.
But there are some other performance advantages there from reducing,
as you've just mentioned, the windage, windage losses.
So can we expect to see a power gain from going to a dry sump system as well?
- Yes certainly, it's more noticeable on higher speed engines.
So if you're running an engine at probably over 7000 RPM and certainly when you
get up to 9000, 10000 RPM.
You can see, typically on a two litre normally aspirated Ford engine,
we could see eight horsepower increase.
- And when every horsepower is valuable, that's a massive difference.
- Yes, yes a big difference yeah.
- Now let's just go through the component form of the dry sump system.
So you've mentioned there's a remote reservoir that's mounted somewhere
in the car.
Another advantage of that, it allows you to put the reasonably significant mass
of the oil exactly where you want it in the car for balance perspective.
But then you've got the dry sump pump which forms two functions.
It's pumping the oil out of the engine as well as pumping the oil back into the
engine from the dry sump reservoir.
Could you talk to us about the scavenge side of that dry sump pump,
'cause we hear the term four stage, five stage, et cetera.
Can you talk to us about what that means?
- Yeah you're quite right, the pump or pumps are split into two different jobs.
There's the pressure side and then theres the scavenge side.
Now whatever oil you've got in your dry sump, you've still got to pick it up.
So the more scavenge pickups you can have, ultimately if you had four,
one in each corner of the pump you're going to stand a pretty good chance
of picking that oil up, drawing it out and getting it into your main tank.
If you haven't got effective scavenge, what starts to happen is you start to
lose level in your main tank and your engine starts filling up with oil.
Now it's a bit, I mean things like Formula 1 engines, they have very complex systems.
But typically we use a two scavenge system so one at the front, one at the back
and that works very well for most jobs.
It's also probably worth mentioning here that when any engine is running,
you're inevitably going to have some level of blow by which is the combustion pressure
escaping past the rings, making its way into the crank case.
So particularly in high performance engines, we generally end up seeing some level
of positive pressure in the crankcase but with a dry sump system, particularly with
multiple scavenge stages, can you overcome that?
You certainly can and typically on our dry sumped engines we pull a vacuum.
Albeit a fairly small depression, but we do.
And we start off, if you said something like, you want three times the capacity
from your scavenge to your pressure, that's a good starting point.
I mean we have run more four or five times, can't say that we gain a lot from that.
So you've got to balance gaining power versus losing power and driving more
pumps and more friction.
But yeah a small depression and two scavenge is a good starting point.
- Now conventionally we normally see these dry sump pumps fitted external to the engine
which does add a layer of complexity and one of the problems I always worry about
is you've then got a rubber drive belt from the, rubber's maybe not the best term
but a drive belt nonetheless from the crankshaft pulley to your dry sump pump
which is another potential source of failure.
So can you talk to us about the development of your dry sump systems.
You've actually gone away from an external pump?
- Yeah over the years we've had huge problems with drivers going off into
the kitty litter, picking up stones, wrecking the belt and obviously ending
up with a damaged engine.
So one our latest Ford Duratec style, EcoBoost style dry sump,
all the pumps wer internal, so they're chain driven, internally, there are no
external pumps or drives.
Much more reliable, much simpler, there's just oil in and oil out.
And it's been a really good way to go.
- Less room for error.
Now that's all well and good.
Dry sump, obviously that's the ultimate if your class allows it, if your budget
allows for it.
But of course there are a lot of us at enthusiast level that are running lightly
modified factory engines where oil surge on the race track is still a very big concern.
You've also been involved in some classes such as British Touring Car Championship
where for some interesting rule reason, they've actually stipulated you must
stay with a wet sump system.
What challenges does that give you and what are the ways you can overcome that,
how can you get the best results if you're stuck with a wet sump?
- Yeah it's a bit of a bone of contention really because we and other engine
builders have said for a long time, it's actually cheaper to go *DRY* sump.
But anyway it's an old regulation, it's still there, and it's a major challenge.
I mean the amount of work we put into our wet sumps to get them to be reliable
is immense.
We have all sorts of things like moving pick up pipes, we have trap doors around the
oil pickup, one way valves.
A big job and occasionally on certain projects we have to add an Accusump which is like
having a big syringe of oil connected to your main oil gallery and the minute the pressure
drops, it whacks oil straight into the main oil gallery.
Very simple but very effective device.
- Alright there's a few things I want to sort of go back in and unpack there because
a lot of our viewers may not understand the terminology you've just used.
So let's start with the oil pickups.
So in a wet sump you've got an oil pickup that's physically bolted to the underside
of the oil pump and its job, unsurprisingly is to pick up the oil from the bottom
of the sump.
However the problem is when you're running very high G forces out on the racetrack,
the oil is physically sloshing around in the sump, running away from the pickup.
So you've talked about a moving pickup and can you just tell us how does that work?
- Yeah I mean basically the pickup pipe tries to follow the oil.
So if you've got a particular G force, whether it be braking or accelerating,
generally we see higher G forces under braking, the oil's all trying to rush forward
so we try and follow the oil as much as we can with the pickup pipe rather than
trying to contain it always because at high oil temperatures, the oil is so thin,
it just runs away.
- So what you're basically trying to do there is always locate the pickup in the location
in the sump where the oil is trying to run to?
- Yeah exactly.
- Now you've also got a little flag, kind of, I'll call it a flag, I'm not sure if there's
a technical term you use internally for it, welded to the end of that pickup.
So how does that help that pickup move around?
- Well it basically, obviously the oil is rushing to one side of the sump and it's
basically forcing, it's almost like having a keel on a boat in effect, it's forcing the
pickup pipe plus the weight of the pickup pipe, the G force is moving
it in the right direction, it just helps that.
- Alright so that's the pickup there but that still requires you to actually try
and hold the oil in the sump and again when you're pulling in excess of maybe
1.4, 1.5 G in a corner, the oil is physically trying to run away out of the sump.
So is this where your trap doors come in, can you tell us how those work?
- Yeah we're running very high speed logging and very accurate pressure sensors
so we can see exactly what's happening to the oil and we're very very careful.
We're looking at drop outs on the data logging and we've got features in the ECU
where we'll only allow a drop out of a certain limit for so long before we'll go into an engine
limp home or even cut the engine.
So we're looking at that and we're constantly developing to try to remove
those dips.
Particular circuits have particular problems, some circuits we don't have any problems.
So basically then we run trap doors if you like and one way valves around
the oil pickup, windage trays that try and keep the oil down below the crankshaft
where it's trying to pick up the oil.
It's pretty complex and there's a lot of work that goes into it.
And quite often, to be honest, one of the cheapest ways of solving this,
particularly if you're on a very limited budget is go and buy, I think for a couple
of hundred dollars, an Accusump system whereby you haven't got to necessarily,
you know we're forced a bit down the direction because the race teams don't
want to add anything 'cause this Accusump weighs something and it's
the package space.
But really, if you're running your own car and you just want a cheap and easy
way of getting rid of oil surge, it's brilliant.
- OK it's good that you've brought that up, the Accusump because this is a product
that we do see in the enthusiast market, it's quite popular.
And it's not a product that we've personally had much experience with.
So I wanted to get into that in a little bit.
Now you've already kind of mentioned it's basically like a giant syringe but I'd like
to dive in a little bit further on that so how is the Accusump plumbed into
the oil system?
- It's very simply literally plumbed into the main oil gallery and it's got like an air
spring on one side so you charge the system with air pressure.
The idea is when you fire up the engine and you pull up the revs, basically the oil
overcomes the spring pressure and it fills up the cylinder full of oil.
So what happens is it's sitting there, as I say, like a big syringe, the minute the
oil pressure drops on the other side, the air spring forces the oil into the
main oil gallery and you get, obviously only for a time period until it can
recharge itself but it's normally enough of a time period, you get different
sizes and capacities, we tend to use the fairly small, lightweight ones but it's on
capacity of oil.
The bigger the capacity, the more timeframe you've got.
But it normally gets you through the specific problem you've got,
cornering, braking under that specific corner, you're out of the corner and as
you're going down the main straight it's recharging it.
- So important to mention here that this really is a safety backstop and particularly
if you've got a completely stock engine that does suffer from really bad oil surge,
this on its own may not be enough to save the engine but when you start
using it in conjunction with some of the other techniques that you've mentioned,
it's enough to really give good reliability?
- It is, I mean if you take a pretty stock production engine, you'd pretty much get
away with putting a very simple baffle in the sump, just a static simple baffle that
most speed shops sell or you could easily fabricate it yourself, with an Accusump
you're going to be in pretty good shape.
- Right I think that's some really great information for our followers out there
because a lot of enthusiasts do want to take their cars to the track.
They don't want to be hurting the engine but perhaps they don't have the several
thousand dollars that a dry sump system entails so hopefully everyone's got
something out of that that they can apply.
Thanks for your time there David.
- No problem, thank you very much.
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