223 | Dry Sump Systems
- Hey guys, Andre from High Performance Academy. Welcome along to another one of our webinars where today we're going to be talking about dry sump lubrication systems, What they are, why we need them, we'll look at the components that go into a dry sump system, look at how those components need to be laid out in the car and installed and we're going to have a look through that system, particularly on our Toyota 86 racecar which has got a relatively basic homemade dry sump system installed that does a great job, yet doesn't cost the earth. Now before we get into this, we really need to talk about what the system is and of course we are talking here about the lubrication system for the engine. And when it comes to racecars, anything that's running on a circuit in particular, we see a lot of problems with engine failures as a result of lubrication issues. So what happens normally is an enthusiast will take their everyday daily driver car, start modifying it, start taking it to track days and then of course the bug bites, starts making more power, maybe adding better suspension and stickier tyres that generate more grip.
And of course the problem here is we get to a situation where the car is generating more G force out on the racetrack than it could ever hope to achieve on the road and the factory wet sump lubrication system is not designed for this. What happens then is we get the oil will actually flow away or slosh away from the oil pickup, the oil pickup picks up air instead of oil and of course when we get air going through our lubrication system, we end up with the situation where we can get metal to metal contact between our bearing journals and our crankshaft and our connecting rods and our bearing material itself. So that can almost instantly result in engine failure and doesn't take a lot of oil starvation for that metal to metal contact to occur. And as soon as that occurs, it also generates a lot of heat so we can see some really nasty failures as a result of this. And the first things to discuss is how do you know that you are at a point where you need to consider at least some level of upgrade to your oiling system.
So what we'll do is we'll just jump across to my laptop screen here for a moment. And this is some data from our Toyota 86 development car, this is still running the Subaru FA20 engine. And at the bottom of this trace here we've got our oil pressure in yellow. It's being displayed in bar here. So we've got our trace at the top here in purple is our engine RPM.
And what we need to understand here is that our oil pressure should always be related to our engine RPM. Rough rule of thumb is that we should be expecting to see somewhere in the region of about 10 psi oil pressure per thousand RPM. That's not rock solid, it's going to depend on our oil viscosity, our bearing clearances as well as the oil temperature. So there's a bunch of stuff going on in there but that's a really rough rule of thumb to work with. So in particular here we've got this situation where we can see our oil pressure is dropping.
Prior to that position, we're sitting at about 4.3 bar and then we see that drop down and we're sitting probably more around about 3 bar so 45, 48 psi give or take thereabouts. Given that we are at that point there, about 6000 RPM it's not ideal but we still have reasonable oil pressure. The other thing to keep in mind with this is we need to take into account the amount of load on the engine. So if we look at our throttle position there, we can see at that particular point, this is going through a long sweeping right hander where we are holding a sustained 1 G of lateral acceleration. You can see that we're only at about 38% throttle so we're not really actually asking for much power from the car.
Which is a good thing because if our oil pressure is dropping and we're under high load, this is the situation where we are likely to have metal to metal contact occurring. So this particular point, not a huge concern, we've also got a reasonably large drop in our oil pressure at this point, we get down to 2.3 bar so what's that, about 18, 19 psi. So that's starting to get pretty scary, particularly given that at that point we are at about 5500 RPM if we look up here. Now again, saving grace of that particular area is again we are off the throttle completely, that's actually a throttle blip there to match revs on a downshift that you can see. So again, not a lot of load on the engine.
We've got this final area here. Again we can see that we're getting down to about 2.5 bar, so 22 psi. But again we are off the throttle. So not great news for our Subaru FA20 engine. Subaru engines aren't generally well known for their ability to last long periods of time without good oil flow so we've actually been pretty lucky with this engine.
The only reason that it is holding together is because the areas where we have got this oil starvation or oil surge occurring, we are also under basically minimal load. So not a huge problem. To put some perspective around that as well, my old drag car, we originally started that, Mitsubishi 4G63 for those who aren't aware. We originally started that with a fairly heavy modified wet sump system, it used a proper baffle box around the oil pickup with rubber trap doors to make sure that the oil could flow into the pickup but not away from it. And what we found with that particular car is on the launch we would pull upwards of 2 G very briefly as we launched.
We actually saw the oil pressure drop slightly but not for a sustained period of time and nothing dangerous. During the actual run down the drag strip, the oil pressure was always rock solid but the scary part was that when we pullled the chute in the deep end of the track as we went over the finish line, and clutched in at about 10500 RPM, got on the brakes, between the combination of the parachute and the brakes, we would see the oil pressure drop down as low as about 12-15 psi. Now again we're off the throttle here but we're still at 10500 RPM so that's pretty scary for our engine, definitely not what we want to be seeing there. So let me just, if I can close this down. No I can't, that's interesting.
Bear with me while I try and close down my screen here. OK we've got a bit of a problem there 'cause that's stuck. I'll be right back. Alright, sorry about that, we're back up and running. Just had a little bit of trouble actually getting out of full screen mode.
Alright so before we get into our dry sump, I just want to mention that this is not the only option because dry sump systems, as we're going to talk about during today's webinar, they can get pretty pricey. They are the ultimate, particularly if you are building a dedicated racecar but if you've got something that is a crossover, you're only doing some track days and you don't want to break the bank, then it is possible to build a pretty good system out of a wet sump. And if you do want to learn a little bit more about that, we do have a webinar in our archive which you can go and check out. We'll just head across to my laptop screen for a moment. So it is webinar 201 and while I can't really show you too much detail here, obviously this is the webinar.
If you want detail, go check out that webinar. What we've got here is the wet sump system that I have built for our Subaru FA20. So we can see that I've just circled, that's a sump that's got wings on it that holds a larger capacity of oil and the part that I am touching right here is the baffle box. A little hard to get the detail, again, go check out the video so you can see exactly what goes into that. But this is a box that goes inside of the sump and it goes all the way down and seals to the base of the sump.
The oil pickup goes down in the middle of that and the idea here is it's got rubber trap doors that open up, allowing that oil flow in towards the pickup but it will stop the oil from flowing out. So that'll get you through for probably the majority of club level cars. Particularly if you've got a daily driver that you are track daying a couple of times a year, that sort of thing. Then this is probably more than enough but for those who are getting a little bit more serious, those who are building a dedicated racecar and for those who are generating massive amounts of lateral G force for cornering. And this is also, our braking and acceleration is just as much of a problem as I talked about with the braking area with my drag car, then unfortunately the dry sump is probably the way you want to go.
So the dry sump system, as its name entails, what it does is it gets the lubricant out of the sump and it stores it in a remote reservoir. So what I want to do is just basically walk through the components of the system one by one. So this is the entire system that is installed in our V8 powered Toyota 86. So this is the dry sump reservoir here. This will hold, I think somewhere in the region of about eight to 10 litres of oil.
So one of the advantages already over any factory wet sump system is we've got a lot more oil capacity in the system between the tank and also the lines running forward to the engine. So this allows us to also do a better job of getting the aeration out of the oil which is one of the tasks of the dry sump tank, so that we are returning oil to the engine and not oil that contains a lot of air bubbles in it. So our tank there, we've got a sight glass on the side of it as well so that we can check out oil level. So when you've got a dry sump system, your factory dipstick is going to be of absolutely no use to you. The dipstick checks the oil level in the sump with a dry sump system.
As its name entails, we no longer have any oil in the sump, it's all contained in the remote reservoir. So we need to be checking the oil level in that reservoir and this can be a little bit tricky. This sight glass is a nice addition actually, it's not something we did, it was on the dry sump tank when we purchased it, purchased the car. But it does give you the ability at a glance to see exactly how much oil you've got in that tank. Now what you can see there is we've got the little marking here for our level.
And this is one of the areas, king of getting a little bit ahead of ourselves but it's a good opportunity to talk about this now. One of the areas where I see a lot of people that are new to dry sump lubrication systems going wrong is that they will massively overfill this tank thinking that we need out oil level to be right up the top of the tank or something of that nature. General rule of thumb is that we want the tank to be approximately two thirds full. So that's where we've got our mark around about there. And it is important because if you overfill the tank, what you're going to end up with is problems with the dry sump tank actually spitting oil out into your overflow which no one really wants to see.
Now in terms of the fittings on this tank, what we've got here, right at the bottom which is a little bit hard to see, is we've got our drain. So this actually just goes under the car, so it's easy to drain without making a mess. So this is obviously ideal if you are going to be performing an oil change. Then we've got our pressure pickup so you'll note that this is picking the oil up from the bottom of our dry sump tank. So this is really the important point.
Because our dry sump tank, by its very nature is relatively tall and relatively small in diameter, it means that there's always going to be a head of oil above that pickup. And this means that regardless what the car's going, unless you've rolled it into a ditch, but we won't go there. Basically regardless of your lateral longitudinal G forces, there is always going to be a fresh supply of non aerated oil available at that pickup. So that line that we can see there, that then runs underneath the car forward to the dry sump pump. We've got our return here which is a little bit hard to see.
Now the key with this as well, and I talked about getting the aeration out of the oil. We can see that this actually comes in at an angle. So the idea here with that return is it's going to swirl the oil around the outside of the tank. There's generally going to be some plates inside of the dry sump tank as well with holes drilled in them or punched in them with the intention of basically helping separate the air out of that oil so that by the time that oil makes its way back down the bottom to the pickup, we are just left with pure oil. Then the final fitting that we've got on this is our breather.
So even a dry sump system is still going to breathe so we need somewhere for the oil vapours to go and in this case that actually runs forward back into the engine bay. So that's the dry sump tank component. The next part that's really important here is the sump itself. So here we've got a relatively crude modification to the factory Toyota 1UZFE sump. So for those who are familiar with the 1UZFEs, they run a two piece sump.
The top section that bolts to the bottom of the engine block is cast aluminium and in stock form they run a pressed steel lower section which is where the oil pickup is placed. So in this case the fabricator who made this system simply made up a laser cut aluminium plate to replace that section and then there is this lower sump section which is where the oil sits. Now in this case, we've got a relatively basic oil pump which is known as a three stage dry sump pump. So we've got two pickups here on either side of that lower section of our sump that run to our oil pump which we can see up here. Let's have a look at that pump and excuse the fact that it's filthy, this has just come from a race meeting.
So as I've mentioned, three stages here, they are labelled, this is a Peterson dry sump pump. So the two parts of the pump at the front there are known as scavenge stages. So these are the sections of the pump that will actually draw the oil out of the sump and pump it back to our reservoir in the boot. Or in the rear of the car, wherever you've got that. Then you've got the third part of the pump which is this section at the rear, is the pressure stage.
So this pressure stage draws the oil out of our reservoir and then pumps it through the engine. And you can also see that with the pressure stage, there is an adjustable pressure relief on this so we can actually adjust our maximum pressure. It's sort of a bit of a balancing act here because the dry sump pump is driven off the nose of the crankshaft. So we can affect the amount of pressure the pump will produce by controlling its speed, although all of the pump manufacturers will dictate a maximum speed that the pump doesn't go past. So you need to keep that in mind.
Beyond that you've also got the pressure relief valve. OK so with our system here as well the other advantage is, or the other aspect I should say is that once we've gone through our dry sump pump, we've got our pressure stage drawing the oil out of the reservoir, it's going to then need to pump it into the engine so we need to remove the factory oil filter housing and in this case we've gone to a remote housing which we can see here. This allows us also the flexibility of running a much larger oil filter which can be advantageous for racecars. Also gives you the opportunity to run some of the remote filters where you can actually visualise what's going on in the filter while the engine's running. So at a glance you can see if there's any debris going on inside of that filter or going through that filter.
And from here, so this is the inlet so basically in our system what we do is we run from the dry sump pump forward to the front of the car, we then run through our oil cooler, comes back out of our oil cooler into our remote filter housing there and out of our housing there, we can see this section here runs back down and that is where it returns back into the engine. So this is in place of the factory oil filter housing. So as you can probably get the idea here, there is a fair bit going on. There's a lot of work involved in fitting a dry sump system. The last part of that puzzle as well which I'll just show you now is the way that the pump is actually driven.
So this is the dry sump drive belt which is driven off the nose of the crankshaft. So another part you have to go through there is coming up with a way of attaching that drive mechanism to the front of the crank pulley. If you are building a race motor you'll find that some of the manufacturers of harmonic dampeners, the likes of ATI for example, they will have threaded holes in the front of the pulley that make it really easy to bolt on a dry sump pump drive mechanism. So that's our whole system there and as I've said, a lot going on there so we do need to give some consideration to that. Obviously if you're going to be fabricating all of that system yourself, there is a lot to take into account which is also all going to end up adding to your cost.
Now because it's not really possible to see what's going on with the dry sump itself on our Toyota 86, I wanted to take you through and show you what that actually looks like, so this is a Dailey Engineering dry sump system. We actually did a great interview with Bill Dailey from Dailey Engineering. If you want to actually learn a little bit more about his systems, check out our Dailey Engineering interview on our YouTube channel after this. But this is his LS system, or one of his LS systems. We can see the dry sump system down here.
We'll have a better look at what goes into that. So his is a little bit more integrated in so much as he is making a component from start to finish for a particular engine. So the advantage here is that his dry sump pump, both the scavenge and the pressure aspects of the pump integrated into the sump itself. This makes your plumbing much easier because you don't need to plumb from the sump for the scavenge stages up to the dry sump pump, that's all actually done internally so it keeps it a lot simpler. And we've got another shot of that there so it's a little hard to see.
We've got in this case this is I think off the top of my head a five stage pump. So we've got basically a chamber inside this sump for each pair of pistons and conrods and there is a scavenge area which you can't see, it's just onto the side of the sump there. And then externally you can see there's some channelling that draws all of that oil from the sump into the scavenge stages. From there the rest of the plumbing is pretty much what we already looked at. Alright so I want to talk about some of the advantages of a dry sump system.
So the first one, which should be pretty self explanatory here is we are going to primarily want to install a dry sump system to prevent oil starvation which we've already mentioned there is likely to happen when we're creating excessively high lateral or longitudinal G forces. So that's the number one aim of course is to keep our engine alive. And this is what most people think the dry sump system is there for. Absolutely that is its number one function but there is a lot more that goes on with this as well. The next aspect is that it reduces the aeration of the oil in the dry sump tank itself as I've already mentioned.
So the oil that the dry sump pump is then pumping through the engine has less aeration, it's able to do a better job. The other aspects that are a little bit more subtle though is that because the dry sump pump is sucking so much oil and air out of the crankcase itself, what it can do is actually pull a vacuum in the crankcase. Now this has a couple of advantages. First of all what it does is it reduces what is referred to as windage losses. So in wet sump engine, because we don't have a vacuum in the crankcase, generally we're actually going to end up with blow by creating a slighly higher pressure than atmospheric.
So we've got a lot of oil vapour floating around in the sump, or in the crankcase and when the crankshaft, the conrods are turning, they actually have to basically hammer their way through this oil mist in the sump. So by reducing the pressure in the sump, it reduces some of that windage, we get less windage losses and as a result we can actually see an engine pick up a small amount of power. Talking to Bill from Dailey Engineering about his LS systems, if one of these systems is bolted onto an otherwise completely stock crate motor, he expects to see somewhere in the region of about 13 to 16 horsepower gain. So definitely not enough to on its own justify the expense of the dry sump system but when you take into account the other advantages that the system gives, then definitely that's going to be a worthwhile gain. The other advantage though which again is quite often overlooked is that because we are able to now pull a vacuum in the crankcase, this gives the advantage of being able to use a lower tension ring pack.
So how this works is that with a factory engine, we're going to end up with a ring pack that has a reasonably large amount of radial tension which helps, particularly during the intake stroke, during the intake stroke we end up with a low pressure area in the combustion chamber or the cylinder as the piston moves down the bore, drawing fresh air and fuel charge into it. So what we've got is low pressure above the rings and if we've got a moderate to high pressure below the rings, this can actually help drive oil past the rings or blow by gases past the rings up into the, no not blow by gases, just the oil I should say, up into the combustion chamber and getting oil into our combustion chamber doesn't do a lot of good things for anything. One of the downsides with it is it's going to reduce the octane or the effective octane of our fuel. Obviously we're going to be burning oil, so oil consumption's a consideration. And on a knock prone engine, reducing that octane can potentially be dangerous to our engine.
So on the other hand with a, so to combat that with a wet sump system we need a ring that has a relatively high radial tension to prevent that occurring. When we go to a properly designed dry sump system though, because we are able to draw a reasonable amount of vacuum in the sump, we can go to a lower tension ring. And the advantage with a lower tension ring is that we then end up with less frictional losses because it's not forcing out against the cylinder wall quite so hard. So net effect there, if you build an engine purely around a dry sump system using low tension rings, between the windage losses and the frictional losses that we're avoiding with those low tension rings, that 13 to 14 horsepower I talked about before might become more like 30 or 40 horsepower so it starts to actually become quite significant. Alright I'm going to get into some questions and answers shortly so if there's anything that I've talked about so far, please feel free to start asking those.
I've still got a bit more to carry on with here though. So we've just talked about drawing a vacuum in the sump. So this is one of the keys with a dry sump system and it's worth just mentioning this in a little bit more detail. So in general, again drawing some information from Dailey Engineering's experience here, in a road race application, they generally aim for somewhere in the region of 13 to 14 inches of vacuum in the crankcase. And if you want to draw a vacuum in the crankcase then obviously one of the things you need to be mindful of is rocker cover breathers that are vented to atmosphere aren't going to cut it.
So let's just jump back across to my laptop screen for a moment and this is actually the breather system that we've got on the rocker cover of our 1UZFE. So we've got that breather sitting there, that is not a vacuum regulator so this actually, this particular setup is defeating the purpose in effect. I'll point out we've probably got a little bit of work ahead of us here, this is just as we had the engine delivered to us and we've just run with it so far. But it is an advantage if we can actually block that off and prevent the engine from, or the dry sump system from actually sucking air into the crankcase. Given with our circumstance we're only running a two stage scavenge on that pump anyway, the ability for us to draw a really good vacuum is going to be somewhat limited.
So yeah if you want to get the full advantage from that, you're going to need to make sure that the engine is sealed from a breather perspective. However, there is also the other consideration that we can end up with too much a vacuum in the engine, in the crankcase and that can also damage things so in this instance what we can get into a situation is where we've got so much vacuum that blow by gases are actually being drawn into the wrist pin boss and basically drying out or sucking out the lubrication out of the wrist pin boss and that'll quickly eat up your wrist pins and your pistons. So want to be a little bit mindful of that, again keeping that sort of 12 to 14 inches of vacuum in mind. So where this gets to be a problem is that when the engine is under high load, you're going to end up with some amount of blow by so it's pretty difficult to get really high levels of vacuum at high RPM and wide open throttle. But of course the scavenge stage of the dry sump pump is driven from the crankshaft so the speed of the scavenge stages is relative to crankshaft RPM and the issue we can get into here is where you jump off the throttle at very high RPM.
So all of a sudden you've still got very high dry sump RPM. So your scavenge stages are working really hard, when you jump off the throttle, the blow by from the engine being under full load, full power all of a sudden goes away and you can see a really sudden sharp increase in vacuum which can potentially be dangerous. Now one of the areas we do see that as well is that it can end up drawing air past the crankshaft seals. So not necessarily a big issue for our front crank seal but with the rear crank seal, particularly on a clutch car, you can end up drawing clutch dust into the seal area and into the crankcase and obviously that's abrasive so we want to avoid that where possible. So another option that is available is, if I can find it, yep, ah no not that one.
This one. Alright we'll jump across to my laptop screen again. So this is a vacuum regulator. So this one is from Peterson Fluid Systems. But they're available from a range of different suppliers.
So the idea with this is that you screw this on in place of your breather and it will basically regulate the amount of vacuum that can be drawn in the crankcase, making sure that you don't end up with excessive crankcase vacuum that could potentially be damaging your engine over time. And you can see there is a little filter element in there so if this does need to open in order to manage that, regulate that vacuum, you're not going to end up drawing in any dirt or debris from outside in the engine bay. So it's definitely a good idea for those of you who are considering developing a dry sump system. Right lastly we just want to have a quick look at how the dry sump system is plumbed up. And there are a variety of ways of doing this but within reason this is generally the sort of system that I use.
So we've got our dry sump pump here. So in this case we can see we've got a five stage pump. So we've got, in this area we've got four scavenge stages drawing out of the crankcase and that is all being returned back into the dry sump tank. You can see they've got an optional filter there. It's not something we run but you can add that in there.
It's going to make sure that no debris ends up in the dry sump tank itself. Now interestingly as well, this is something I haven't touched on yet which I just will, these little red areas here, these are what's called a scavenge filter. So it is a good idea to use scavenge filters. Sometimes these are literally an external filter which I think I've got one right here, yep I have. So again this is from Peterson Fluid Systems.
So basically it is just a screw in AN filer with a reasonably coarse gauze mesh inside of it and what it does is it basically protects your dry sump pump in case of an engine failure. Obviously you don't want to end up sucking pieces of piston or connecting rod or crankshaft, through that expensive dry sump pump, that's going to destroy it really quickly, so that'll trap that. Other people tend, because often this can be limited on how much space you have to work with. Other people will eliminate the scavenge filters but instead they'll actually build a mesh filter system into the bottom of the dry sump sump just to again prevent those larger pieces of engine making their way through your pump. Here we've got our dry sump tank of course and then we've got our suction area.
So this is where the oil is being pulled forward into our pressure stage and then finally from our pressure stage it runs forward, goes through our filter, goes through the oil cooler and then finally into the engine. I actually have run this the opposite way in terms of the location of the filter and the cooler in our Toyota 86. I tend to like to have the filter as that last backstop for any debris making its way into the engine so generally I like to have that as close the engine as possible but basically that's the sort of system you should be plumbing there. Right so we'll jump into some questions and answers now. If you've got any more questions, please feel free to keep asking them.
Nathan has asked, do you every worry about acceleration and deceleration affecting a dry sump system? Well this is kind of the very reason we go to a dry sump system and it's really all to do with the orientation of that reservoir, because we've got that relatively skinny but tall reservoir, it really doesn't matter how much lateral or longitudinal G force is applied to that. Because you've got such a head of oil above the pickup, you're always going to be drawing fresh, clean oil out of the bottom of that. Global Media has asked, what brand of racing oil are you guys running in the racecars? I've been a long term fan of Motul. I'm not paid to say that, we're not sponsored by them and in fact the oil is incredibly expensive but in terms of keeping your engine together, I don't really care how much I'm paying for the oil because the oil becomes really cheap in comparison to replacing and rebuilding your engine. And how I got onto this was back in the earlier days of my drag racing, we were running Pennzoil and a few other different brands and we were really struggling with our 4G63 program where we were running to 10500 RPM, somewhere in the region of 1100 wheel horsepower, we were really struggling with bearing life.
And we were basically rebuilding the engine or just fitting new bearings to the engine after about 10 to 15 runs down the drag strip. And that gets pretty tiresome pretty quickly. We were never really having problems with the bearings having metal to metal contact between the crankshaft and the bearings but you take them out after a meeting and you'd see that they were showing signs of distress. And all of the oil adverts in the world are kind of pretty much pointless in comparison to actually seeing first hand the difference that running a better quality oil makes. So we switched from the oil we were running, I think at the time it was Pennzoil but we've tried a few and we switched to Motul 300V 15W50 in our 4G63 program and we went from needing to replace the bearings after about 10 or 15 passes to basically being able to do just about a full season on the same bearings.
So for me, that was enough of a sales pitch to know that the oil was worth it and I've kind of stuck with it ever since. Anthony has asked, when do you need over 1 G of side load and or acceleration? Well you need it Anthony if you want to go fast. Unfortunately if you want to be going fast on a drag strip or a race track, you're going to be well over 1 G. To put some perspective around that, I mentioned earlier that our drag car was pulling in excess of 2 G on a launch. I can't actually remember now what it would pull in deceleration when we pop the chute and we're on the brakes, probably not quite that much but significantly more than 1 G.
To put some numbers around a modern racecar on a proper slick, you're probably going to be seeing somewhere in excess of 1.5 G in both cornering as well as braking. With some of these more advanced cars running a lot of aero now, that's probably upwards of 2 G so yeah 1 G doesn't really cut it too much, you're not going to be going too fast around a racetrack if that's going to be your limit and even at 1 G sustained lateral acceleration, that's more than most road cars can ever hope to achieve so you're already in the danger area. Kelvin has asked, typically will a stock engine run a variable oil pressure, would there be any advantage to a constant high oil pressure? So in most instances the oil pressure control is relatively basic, there will be a pressure relief valve that is just a mechanical valve so we do see the pressure to a degree vary with regard to RPM. Obviously as our engine RPM increases, we're driving the oil pump harder but at some point the oil pressure relief valve will open, we'll also see that oil pressure vary as our oil temperature changes and the viscosity of the oil changes. I can't say there'd be an advantage to a constant high oil pressure, what we would probably see, particularly at low RPM where we don't need high oil pressure, to get that high oil pressure though, we're probably going to be needing to needlessly run the pump very very hard and there may be some parasitic losses in terms of power related to that.
I will actually just mention there, a car that we recently were involved with, running on our dyno which is a Volkswagen TCR racecar, I actually run an electronic oil pressure control and it switches at a particular RPM so they run quite low oil pressure up to about 3000 RPM I think. And I'm going guess this is all around sort of getting optimal fuel economy, probably translated over from the road car engine but above 3000 RPM it switched to a higher oil pressure. John has asked, my biggest worry with the dry sump system has always been the sump itself, your 1UZ one doesn't look as complicated as this one. What do you need to look out for when making or buying one? OK John yeah so I'll be the first to admit that if we were starting with a clean sheet of paper with no budgetary constraints then I'd probably be designing a slightly more complex dry sump sump for our 1UZ. The downside with that is because it is only at the front of the engine, We aren't able to draw oil from the rear of that sump, so it's definitely not ideal but I'll be perfectly honest here, it also does an absolutely ideal job out on the track, or perfect job out on the track.
We see almost rock solid oil pressure so sometimes I think people maybe needlessly overcompensate these things and as we've sort of seen with this, a very simple system can actually do a pretty good job. So in terms of what you're trying to achieve there though, what we'd ideally like to do is be able to pick up oil from basically all four corners of the sump so that's going to mean that regardless whether we are braking, accelerating, cornering left, cornering right, we're still going to be able to draw oil out of the sump really efficiently. The reality however is that's not always possible so basically everything in life is a compromise there. And one thing I should have actually mentioned that I haven't touched on so far, another advantage with the dry sump system is because we don't need to store oil in that sump, the sump itself can end up being much shorter and this can allow you to then drop the engine and mount it lower in the chassis which can be an advantage for placement of the weight in the chassis. So yeah probably I can't do too much more justice to your question there John because it is a pretty big question in itself.
Daniel has asked, thoughts on scavenge only dry sumps? Looking into a two stage scavenge only, and OEM pump for pressure state due to lack of space on the EJ20. Yeah the EJ or the Subaru engines in general are really tricky in order to mount a dry sump system, we've sort of been toying with that just recently with our FA20 as well so I understand your pain. It's not something that I've done so it's a little bit tricky for me to really speak from first hand experience. So I'm guessing what you're talking about here is scavenging to an external reservoir then using the factory pump to pick up. My concern with that would be whether the factory pump can actually draw the oil effectively.
Obviously you've got a factory pump that's being designed to draw the oil from the sump which it's basically sitting right in front of and then pump it through the engine. Instead it's going to need to draw the oil quite some distance. So yeah I'm not 100% sure how well that would work, again not something that I've been involved with myself. But let us know how it works out if you do try that. 32LGTR has asked, can the regulator also breathe if there's positive crankcase pressure? I assume not, so do you recommend an engine bay catch can still? OK so these regulators, it depends which ones you're working with.
They can still breathe so if you do end up with positive crankcase pressure, and particularly if you are dealing with a turbocharged car, particularly if you're running quite high boost pressure, even with a dry sump system, you are still going to almost certainly end up with some level of positive crankcase pressure, it's one of those things that's really hard to get away from. So for example that's exactly what we had with our drag engine. At idle we were pulling somewhere in the region of about 20 inches of vacuum or just off idle we were about 2500 RPM probably but well before we got onto boost. And then in positive boost we're running up to about 54 psi of boost, 10500 RPM. We were still seeing moderate positive pressure in the crankcase.
So how I actually dealt with that, I didn't use a crankcase pressure regulator. The reason I didn't do that is I knew that was the sort of scenario we're going to be dealing with. So what I used was essentially a modified one way valve or PCV valve off to rocker cover breathers. So what this did is it allowed at lower load, lower RPM, lower boost pressure, we could still pull a vacuum in the sump but when the blow by exceeded the ability of the scavenge stages to draw a vacuum, then the one way valves, the PCV would open and those didn't go into the inlet manifold like a PCV normally would, those were vented into a catch can so a number of different ways to deal with this and there's not necessarily a right or a wrong. Georgeb12 has asked, do you know why you don't want to run vacuum in boosted engines? This was advice I received from Dailey Engineering but wasn't sure why.
Assuming more blow by due to large pressure difference across the rings. I think, not speaking out of turn here, I think you may have got the wrong end of that advice in terms of it's not a case of you don't want to run vacuum, it's probably a case, as I mentioned in that last question there, it's really difficult, if not impossible on a high boost engine to actually run a vacuum in the sump there. So you're going to end up inevitably with some level of blow by that's going to overcome the scavenge stage's ability to draw a vacuum. Daniel has asked, oil lines, have heard of many dry sump system failing due to oil line collapsing under vacuum, any suggestions on preventing that? Look we have never seen that with any of the systems we've been involved with. The answer there would be make sure that you are using a good quality line, a good quality AN hose and fitting that is designed around this sort of purpose.
The stuff that we generally use ourselves, being based here in New Zealand is from Australia, it's call Speedflow. I just like the quality of that particular hose and the Speedflow fittings that go along with it. And they are rated for oil use. I think they are internally strengthened as well which may help with the fact that they don't collapse. But remembering you should obviously have oil in your dry sump pressure suction line that runs from the dry sump tank to the pump anyway.
So yeah I think if you're careful with that, with your selection, it shouldn't really be an issue. Darius has asked, can you plumb the breather hose form the reservoir to the crankcase instead of to atmosphere? No you can't do that because then you're essentially creating a closed circuit system and you do need some ability to breathe here so no you do still need a breather tank off the dry sump reservoir. Nathan has asked, what would be the best spot for an oil pressure sensor in the dry sump diagram? So personally I prefer to run the oil pressure sensor basically where the oil is entering back into the engine and that's kind of what we've got on our Toyota V8 86 it's off the outlet of the oil filter assembly. And, let me just see if I can find that photo. No I cannot, nothing's really working right for me today.
There we go, let's head across to my laptop. So this is our oil pressure sensor here. So it's fitted on top of our remote oil filter housing but all we've got from there into the engine is this short hose which runs for about 150, 200 millimetres. An alternative is that you can also use the factory oil pressure switch mounting location on the engine, that's normally a pretty good area to place it. But basically we want to place it as close to the oil entering the engine so that we're actually seeing the real oil pressure that the engine is being exposed to.
If you mounted that on the outlet of the pump then you run the oil through an oil cooler, then through an oil filter and then into the engine, there's quite likely going to be a pressure drop between the outlet of the pump and what the engine's actually seeing. So yeah the bearings are what we're trying to protect so we really want to know what the oil pressure that they're seeing is. Alright we'll head back across to those questions. Patrick has asked, could you use a thermal valve at the remote filter going to the cooler? Yeah absolutely and on road cars I'm a big advocate of doing that. On a racecar it's not really necessary because we are going to be properly warming up the oil before we head out on track.
So taking that thermostatic bypass out of the oil filter or oil cooler sandwich plate is just one less thing that can go wrong. But for a road car, it's a really good idea. And the reason for this is that it can be dangerous both running your oil temperature too high as well as running it too cold. And particularly if you've got a really large oil cooler fitted to your car that works really nicely out on the racetrack keeping your oil temp under control, there's a pretty good chance that if you're out on the open road just cruising, then you're going to end up with your oil temperature too low and that means that the oil isn't able to get rid of some of the contaminants that make their way into the oil so over time that can be potentially damaging so yep big fan of the thermal valve. Adam has asked, aside from the cost and increased complexity are there any disadvantages of the dry sump system? I think you've really nailed it, cost and increased complexity really are the two big ones.
I will add one more. This isn't something that I've personally seen, thankfully but we do have the potential for a drive belt failure with a dry sump system. Now if everything's installed correctly, then this shouldn't be a huge consideration but it is very easy if you are not too careful with how you've designed your dry sump system and it's all custom made, to end up with the belt not running true between the dry sump pump and the crank pulley. And that can end up having that belt fail over time. Another key area that I've seen issues with this is where the belt is over tightened.
These belts don't actually want to be as tight as a lot of people think and a good rule of thumb for this is that when the belt's tensioned, you should be able to grab the belt and twist it reasonably easily through 90 degrees. If you can't twist it through 90 degrees, then the belt is too tight. So that will also cause failure. Last one, and this is kind of one of those freak occurrences situations, is you can end up with a piece of debris, maybe a stone flicking up off the road or something and making its way through the dry sump belt and causing damage that way. Because of course if that drive belt breaks or fails, then instantly we've got no oil pressure.
So I'm always a really strong advocate of making sure that the ECU is also monitoring oil pressure and instigating some cuts or safety margins there if something like that does go wrong. Kelvin has asked, do you use one of the oil pump stages to draw a vacuum in the crankcase. So yeah that's exactly it, if I wasn't clear there Kelvin, you're going to have the scavenge stages, they're in charge of drawing the oil and the air out of the crank case so it's the scavenge stages that will draw the vacuum there. Kfennell has asked, what vacuum am I targeting at the valve cover on an NA four cylinder, what data do I want to log, pressure and vacuum, where is the temp measured from? OK a few questions in there, let me cover those. So first of all, in terms of monitoring crankcase pressure, I generally will do this in the crankcase.
If you are wanting to do this in the rocker cover, you can do that as well, the valve cover, you just need to make sure of course that the system is sealed so you're going to need to make sure that any rocker cover or valve cover breathers are blanked off if you've got any chance of pulling that vacuum. As an aside as well here, other than sort of focusing on how well your dry sump system is set up and your pressures, your vacuum that you're drawing, you can also use historic data on crankcase pressure or vacuum to give you an indication on how well your rings are sealing. As the ring seal deteriorates, what you're going to see is that blow by will increase, as a result of this, the crankcase vacuum will start to drop away. Even if you aren't running a dry sump system and you're expecting positive pressure in the crankcase, this is still going to be the case, you're still going to start seeing positive pressure in the crankcase start to increase as your ring seal goes away. In terms of pressure, already dealt with that, as close to where the oil pressure goes back into the engine as possible.
And the temperature, generally I'm again monitoring that where it goes into the engine. There's two schools of thought on this, a lot of people will instead monitor the temperature of the oil coming out of the engine. Nothing really wrong with that, we just need to understand the implications, whether we're measuring before the oil goes into the engine or as it comes out because of course the oil coming out, you're likely to find it's going to be a lot hotter. GroovesAndLands has asked, any preference for gerotor versus spur gear style dry sump pumps? I think I probably can't talk in enough detail about the pros and cons of these. I've stuck to, for the most part, the products that we've been using have been the Peterson systems.
I know that different manufacturers have their own different preferences on that but I'm sorry I couldn't really give you a detailed run down on those advantages and disadvantages. Custom Garage has asked, would you still use an air/oil separator or a catch can when running a dry sump on a Subaru EJ20? So air/oil separators, not really necessary because that is happening in the dry sump reservoir so we shouldn't be getting any oil in the catch can. Still need a catch can, there's a couple of ways of doing this. We can run that catch can or breather can straight off the dry sump reservoir which would be my preference. I'd do that in conjunction with having the valve cover breathers blocked off on a naturally aspirated engine.
On a turbocharged engine where we are still expecting to see some positive pressure in the crankcase, we still want those breathers on the rocker cover open and I'd run those to the same catch can. Michael has asked, leakdown from the tank backwards through the into sump after prolonged periods of sitting, is that a concern? Is it best to spin or prime the dry sump pump with a power drill to return the oil to the tank before starting? Yeah Michael it is a consideration, the oil can drain into the sump itself. It depends a little bit on how well sealed the pump is. It's not a massive concern in my opinion. But after the car has sat for a while, you will find that the oil level in the dry sump tank can have dropped.
That being said, you should still be able to start the engine and that's going to rectify itself pretty quickly with the scavenge stages pulling oil out of the sump back into the reservoir. Again you should be in a situation where you've got enough reservoir of oil that you're still going to have a head of oil above the pump anyway. As an added point here I'll just add in, there is quite often with these dry sump pumps, the ability to drive them using a air pneumatic ratchet or something of that nature by removing the belt. And this is really nice if you have had your engine sitting for a very long period of time, or if you've got a fresh engine that you're about to start up. Unlike with a normal crankshaft driven oil pump, you've actually got the ability to prime the oil system, make sure you've got oil pressure and you've got oil flow right through the engine before you start the engine for the very first time.
32LGTR has asked, is there an advantage to scavenging from the back of the head say on an RB26 as well as the sump, or better to have all stages draw from the sump? Yeah so that is actually something that is quite common with the RB26 there. Where they're known for problems with drawing the oil back out of the head. So it's quite common to end up adding an external oil drain at the back of the cylinder head. Really I'd probably be inclined to just run that back into the sump and then scavenge from the sump instead. Otherwise you're using an entire scavenge stage to just draw that oil out of the back of the head.
We've got a little note here, I'm not sure, I'll just see if I can read through this. This is the response from Dailey Engineering, asking about the same question, this is from Georgeb12. Dailey have said, with a dry sump system, the scavenge sections of the pump create a vacuum in the crankcase helping the drain backs from the head work better. In high boost applications where vacuum is harder to achieve, we can add an extra scavenge stage to the dry sump that is dedicated to scavenging the head. OK so yeah that's basically what I was mentioning in that with a high boost engine, you're not going to end up with that vacuum.
So that's basically talking about just getting that oil back out of the head and using a separate stage of that so yep, can be an advantage to do that. But it doesn't really change the fact that you still, if you could draw a vacuum in a high boost application, it's definitely not going to be a disadvantage to be able to do so, it's just one of those things that gets increasingly more difficult to do due to our blow by. Wow we've got a lot of questions. Let's keep going through these. GroovesAndLands has asked, earlier you mentioned oil pans with trap doors and so on.
I've always been leery of these hanging up or getting stuck, have you ever experienced a failure with one of these styles of pans? OK so you've probably got a different perspective of what I'm talking about. After this webinar, search out Cosworth rubber sump trapdoor or words to that effect and you'll probably get a picture of what I'm talking about. So these aren't a metal trapdoor with a sort of a hinge system. These are actually a rubber trapdoor that gets pressed into a laser cut steel plate. And the idea is that the rubber material's quite soft, particularly as it heats up with the oil and becomes really really flexible and the trapdoor will easily open as the oil flows through it and then as the oil tries to slosh back, it'll close against the plate that it is inserted into.
I've used that in a few of our engines and I've had really good results with them. Probably not the only way. I guess the other key piece of advice is obviously if you are dealing with a sump with internal trapdoor in it, make sure you're dealing with a reputable manufacturer, for example I know Tomei do these sorts of sumps for the RB26 as well as the SR20. And I've had pretty good results with those. They're the ones we've used on some of our customer engines.
Kelvin has asked, would you ever need to use an accelerometer to measure G-force to validate upgrading to a dry sump or typically just check your oil pressure? No you don't need to run a G meter accelerometer to validate when you need to upgrade to a dry sump system and it's not a case of if you are at 0.95 G then you're fine but as soon as you go to 0.96 then you must have a dry sump. It's obviously not that simple. It's going to vary from one application to another, it's also going to depend how long are you maintaining that G force, is it just a quick blip or are you at sustained high lateral G force. So really the oil pressure's the bit that we're interested in, that's the one we need to monitor and that will tell you what you need to know. Barry has asked, how do dry sump pumps handle periods of oil starvation at high rpm? Does that cause gear wear on the scavenge stages? Good question Barry, the answer to that is that I really couldn't actually give you too much detail there.
I would imagine just from what I've seen, and obviously the scavenge stages there as well are designed to draw both oil and air and depending where abouts the scavenge stage is picking up, it would be expected that sometimes the scavenge stage may be operating without a constant flow of oil. However it doesn't take a lot of lubrication running through those pumps to keep them happy. I would be basically be picking that that is a design element taken into account with their design so not something you need to worry about. Pax-Sam has asked if you use low tension rings will there be some oil consumption at low rpm? With low tension rings, you can expect some increase in oil consumption in general. However with a dry sump system, as long as it's properly set up, you're going to be getting vacuum basically from idle.
Remembering that the dry sump pump in the scavenge stages are driven off the crankshaft. So the RPM and hence the amount of air and oil that they are scavenging, increases with RPM. Which tends to also increase with our blow by, or sorry, which also we see our blow by increase with RPM when we're under high load. So no we shouldn't really see any difference there but low tension oil rings we can always expect a small increase in our oil consumption. Alright guys I am going to call it there, we've got a huge amount of interest in this webinar which is great to see but we are unfortunately just out of time so I am going to have to call it there.
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