Rob Walker Posted August 2, 2001 Share Posted August 2, 2001 I have just fitted the Caterham dry sump system on my K it has the gold pump and I am using the bell tank with the swirl tower. My question is, running this set up which Caterham recomend with all the engine breathers blanked off except for the top of the swirl tower produces an awfull clucking noise whilst at idle. I have also heard this noise from Mike Bees`s car. Is running the engine at a partial vacuum desirable and why? I get funny looks from fellow motorists. Edited by - Rob walker on 2 Aug 2001 12:31:45 Link to comment Share on other sites More sharing options...
EFA Posted August 2, 2001 Share Posted August 2, 2001 Maybe you've go a Big Hen problem..... Fat Arn See a meaty Vauxhall car here See the Le Mans Trip Website here See the Lotus Seven Club North Kent Website here Link to comment Share on other sites More sharing options...
FH Posted August 2, 2001 Share Posted August 2, 2001 Arnee, you beat me to it mad.gif Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 2, 2001 Share Posted August 2, 2001 There are very few substantiated benefits for the sealed system. I am investigating running a breathing set up using a one way valve. The pressure drop over the valve will give a partial vacuum, which may amount to having no effect whatsoever. Having had a face full of oil from when the scavenge belt fell off I am also investigating running a vent pipe through a one-way valve in the opposite sense to the dry sump tank. I consider it utterly necessary to have an early warning system for the possible departure of the scavenge belt. Caterham are developing mods in this area. If you are planning to use over 8000rpm, the dry sump system may not be up to the job and running an Apollo tank as well may be a good idea. Link to comment Share on other sites More sharing options...
Roger King Posted August 2, 2001 Share Posted August 2, 2001 I am strongly opposed to the fully sealed dry sump system. It is quite common these days on modern dry sump systems for the scavenge pump to pull enough air out of the sump along with the oil to ensure that nothing ever comes out of any breather. But in my opinion this leaves the breather with the job of allowing air IN. The job of a scavenge pump is to create a partial vacuum in the sump to suck the oil out and back to the tank. If the system is totally sealed you will get a partial vacuum in the whole of the engine. This means that oil is not assisted downwards by the weight of atmospheric air at the top of the engine. Apart from this, the engine's seals are now being sucked in. I suspect that the clucking noise (which I too have heard) is air forcing it's way past the seals, although I haven't looked closely at this because we don't use the sealed system. I feel that the best solution when you have a large capacity scavenge pump is to have a small bore breather vented to atmosphere, that will allow air in as needed. Link to comment Share on other sites More sharing options...
EFA Posted August 2, 2001 Share Posted August 2, 2001 My understanding is: A sealed system is that where there is no vent to air between the crankcase and atmostphere. This allows the scavenge as Roger says to get out all the oil, and some air, resulting in a slight vacuum. This must decrease the viscosity of the oil vapor within the crank case thus allowing the crank to turn with less resistance. These systems tend to pump the returnm to the tank at such high velocity that you spend your life emptying the catch tank for the DS tank. A totally sealed system does not have the catch tank which remedies the aboves, but will however not allow the air/oil extracted to separate at the tank as easily and will likely lead to aireation and subsequent engine failure. This, as Peter points out, is quite likely in any engine capable of over 8000rpm. My system has a single small vent to the top end of the engine which returns to the vented section of the DS tank, and it then has a well baffled breather from the dry sump tank to the catch tank. The engine lubricates properly at 9000rpm plus, and the catch tank remains empty. As it works, I wont touch it...... Fat Arn See a meaty Vauxhall car here See the Le Mans Trip Website here See the Lotus Seven Club North Kent Website here Link to comment Share on other sites More sharing options...
robmar Posted August 2, 2001 Share Posted August 2, 2001 Peter do you have any more info about "I consider it utterly necessary to have an early warning system for the possible departure of the scavenge belt. Caterham are developing mods in this area." as you have made me paranoid about this ;-) Rob Link to comment Share on other sites More sharing options...
EFA Posted August 2, 2001 Share Posted August 2, 2001 My car has an external pressure pump, and I* can hand on heart say the warning lamp on the Stack unit which can be programmed at whatever pressure threshold you like (30lbs/sq ft in my case)has already saved my engine twice 8in the event of belt failure - in my case snapping belts! An optical belt position snesor on the K has to be a good idea, or a pressure sensor on the scavenge output?? Fat Arn See a meaty Vauxhall car here See the Le Mans Trip Website here See the Lotus Seven Club North Kent Website here Link to comment Share on other sites More sharing options...
CHRIS CLARK Posted August 2, 2001 Share Posted August 2, 2001 Robmar. I can't speak from first hand experience 'cos I don't have a dry sump (and have NEVER seen Peters engine in place!), but Mike Bees runs what looks like a photo electric cell coupled to a big dash board light. I figure it works that in the event of a dry sump pump belt loss/break it 'makes' the light circuit by being able to see its opposite side (ie. no belt in the way). Result;big light on so you turn it all off damn quick! This is only a basic guide from what I saw while peering at Mikes eng. on a RR day!!! (I may have got it a bit wrong here, but you get the general idea!!!) Link to comment Share on other sites More sharing options...
paul jacobs Posted August 3, 2001 Share Posted August 3, 2001 Hmm, interesting reply by both RK and Arnie. Could answer some questions to the problems I'm currently experiencing with my Vx engine. It's fully sealed system, with a breather out of the dry sump tank to a catch tank, then vented to air via a pipe run down the underside of the car exiting just behind the axle. Whats happening is that the engine, instead of sucking everything down and out of the sump, seems to want to have POSITIVE pressure in it and is blowing oil out of the top of the rocker cover oil filler [recently changed from a push in alloy plug in a quest for a tighter fit], and from around the sump pan gasket causing a holy mess down the underside of the car. Perhaps Roger has a point, and I shouldn't be running the engine in a vacuum but should have a small breather somewhere to help pull oil/air down through the scavenge pump? Link to comment Share on other sites More sharing options...
Rob Walker Posted August 3, 2001 Author Share Posted August 3, 2001 Paul your system is operating different to my own. If you release the oil filler cap on the cam cover whilst the engine is at idle you can hear the air rushing into the top of the engine and the clucking stops imediately. I had not considered oil retention in the head as Roger suggested but was more concerned about what is happening to all the oil seals around the engine as these are not designed to be run under vacuum and possibily have air being drawn through them from outside the engine. It has been suggested that the benifits of running this system is no windage in the sump which can sap power but shurely the amount of energy required to run the scavenge pump and created this vacuum within the engine must negate this advantage ? Rob. Link to comment Share on other sites More sharing options...
Mike Bees Posted August 3, 2001 Share Posted August 3, 2001 A few points: The gold-pumped Caterham K system does indeed return the oil/air mix at high velocity to the tank, but it blasts this mix a swirly arrangement which stops it from foaming up & blowing out into the catch tank (as long as you don't overfill). Prior to the swirly arrangement (technical term: conning tower) this was a big problem. ... I can't see any significance in the density of the oil vapour. ... Surely a *totally* sealed system would be bad, because any blow-by would cause a pressure build-up? ... My dry sump system is "protected" against belt loss by having a proximity detector in close proximity to the pulley on the scavenge pump. It generates a pulse every time a blade on the pulley goes past. A small circuit sees the pulses and keeps a lamp on the dash unlit unless it fails to see a pulse for a period of a second or more in which case it lights the lamp. Mike Link to comment Share on other sites More sharing options...
EFA Posted August 3, 2001 Share Posted August 3, 2001 Paul, Knowing who designed your DS system, you need to reinstate the 1/2" hose from the side of the rocker cover (above inlet 2) and run it to the dry sump tank. I had precisely the same problem before I made this alteration. Fat Arn See a meaty Vauxhall car here See the Le Mans Trip Website here See the Lotus Seven Club North Kent Website here Link to comment Share on other sites More sharing options...
Nick M Posted August 3, 2001 Share Posted August 3, 2001 Arnie, From the pictures on the K2 RUM site, it appears you have a breather running from the cam cover behind the throttle bodies into the top of the dry sump tank and then a breather from the top of the dry sump tank to the catch tank. I assume this effectively de-vacuums the crank case and means you're not subjecting seals to an internal vacuum in the engine ?? I'm currently building a 1.6 16v VX and the intention was to run it sealed, i.e. no breathers from the engine, only one from the dry sump tank to the catch tank. I'm now beginning to think that maybe a breather from the cam cover back into the dry sump tank might not be a bad idea. Or have I missed the points that you were making ?? Link to comment Share on other sites More sharing options...
Miraz Posted August 3, 2001 Share Posted August 3, 2001 Presumably this would prevent any oil from reaching the catch tank, as it would flow towards the lower pressure in the breather running to the cam covers....? Or am I missing something..... My impending sv will be dry sumped, guess I ought to try to understand what problems I've signed up for. So far my list includes... 1. Excessive vacuum in entire engine - possibly improved by some form of vacuum relief valve/breather in the cam cover? 2. Aeration of oil still an issue - does the conning tower/swirl pot arrangement improve the situation significantly? 3. Pump belt failure - need a better warning system as a minimum - is it possible to improve the resilience of the pump drive? two belts? bigger belt? electric supplementary pump? What else have I missed? Miraz Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 3, 2001 Share Posted August 3, 2001 AFAIK, there is no such thing as a "totally sealed system" such as Arnie describes, for the very reasons that Arnie and Mike describe: any blowby would pressurise the system until the seals pop out and the engine fails with oil everywhere. Blowby always happens, so you know the engine is going to need to exhale on a net basis. We have been talking about the common dry sump arrangement where the only link to the external atmosphere from the enclosed engine internal volumes is via the scavenge pump. i.e. the scavenge pump evacuates the engine to the point where the amount of blowby gasses maintain the equilibrium of the internal pressure. Oil will only be drawn into the scavenge pump because of a pressure differential; a crankcase running at lower pressure means the scavenge pump is less effective. Whether this is a significant effect could be determined by measuring the actual internal pressure of the engine, but cannot otherwise be assessed because we don't know the magnitude of the blowby gas volumes. That such systems work at all means the pressure can't be that low. We might however be interested in just getting a little more margin of safety by controlling the pressure. We still know that the net requirement to exhale is being serviced by the scavenge arrangement. This means that any breathing into the engine can be routed through a one-way valve and a simple filter; you can even use a sprung one-way valve that will give a controlled pressure drop, guaranteeing that the vacuum never gets too rarefied. There is no need for an inbound breather to be routed via a catch tank which makes the plumbing simpler. Having run a gold pump dry sumped K with unrestrained seals on the cam cover breathers, I know that under all normal operating circumstances there is never a pressure buildup in the engine (the seals have never popped off the head); the engine (left sealed) would always operate with a partial vacuum. Given that we are contemplating some inbound breathing, there is a question around the appropriate siting. The only sensible answer is to use the existing cam cover breather location; there is an academic possibility that this may improve head drainage. In practice, there will only be an improvement in the drainage when the head is awash with oil and all the drainage holes are immersed; this happens reasonably seldom but may be enough additional safety margin to make a difference. The dry sump system offers more consistent lubrication at the cost of extra complexity, introducing extra points of failure. There is a rather unpleasant problem with the K-series sealed dry sump arrangement, related to belt failures. When the belt falls off the pressure in the engine builds up until it finds a way out. The path of least resistance is to pop the breather plugs squirting oil through the bonnet louvres and into the driver's face; having experienced this I don't want it to happen again. My planned solution is to run an outbound vent through a one-way valve set in the opposite sense and running into the top of the dry sump tank. So what are the purported advantages of running a sealed system that I will be throwing away by these planned changes? In short, I don't know because I have never seen substantiated descriptions of those advantages. Here are a few guesses: 1. Simplicity - the vacuum is never so rarefied that it affects the scavenging, so why make it more complex than it needs to be. 2. Simplicity - why have extra bits on a race engine that only do anything useful during a failure - by that time you will have lost the race anyway. 3. Windage - the pistons move at incredible speed, so there could be viscous resistance amounting to something measurable. The loss from the scavenge pump working against a vacuum stands a chance of being smaller, giving a net gain - this is relatively easy to test on a dyno, if anybody has the time. 4. Fail safe (very speculative) - just suppose the scavenge belt falls off and the seals hold up to the build up in pressure; the point that gives could be the scavenge pump rotor being driven by the positive pressure. In this case you could get the oil evacuation being performed (at least with partial efficiency) and it might be enough for the engine to stay alive. (Obviously this wouldn't work if your pressure pump was a stage on the same belt driven pump). 5. er... ummm... that's it So my thinking is: The one-way valved inbound breathing will allow some control of the vacuum giving you most of the power benefits from #3 without detriment to the scavenging. The complexity goes up to the extent of a one way valve and a breather filter. The facts of life are that the belt *does* fall off occasionally. I am not planning to investigate whether the seals will stay in under all circumstances when the belt fails, and I know I don't like getting a face full of oil. If I can arrange for that oil to go somewhere useful like into the dry sump tank then all the better. The complexity goes up to the extent of a one way valve, a piece of hose and a fitting somewhere at the top of the dry sump tank. With the pressure pump still being the normal k-series item, when the belt falls off there is a realistic chance to shut down the engine before it suffers any ill effects and before the oil pressure warning comes on. This is the value of an early warning system. Mike Bees uses an optical sensor; I plan to go low-tech and put a switch on the spring-loaded tensioner and see when it pings back on its stops. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 3, 2001 Share Posted August 3, 2001 Can anybody think of a good reason why Caterham would fit their dry sump system with 3-vee pulleys and a 4-vee belt? This is what I currently have which is self-evidently krappensheit. Link to comment Share on other sites More sharing options...
Andy Checkley Posted August 3, 2001 Share Posted August 3, 2001 Is belt failure on the scavenge pump because of the belt breaking at high revs or is it because the belt "grows" and slips the pulleys? If its slpping the pulleys would a deeper shoulder on the pulleys do the trick? Andy Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 3, 2001 Share Posted August 3, 2001 The belt runs on a spring loaded tensioner. If it is trying to get four vees to run in three grooves it is going to fail; end of story. I had previously attributed the failure to the belt wandering on the tensioner and falling off, which is still quite possible. The belt also looks suspiciously underspecified for a critical oil pump. I have started investigation of getting a custom solution made up and I am going to take my existing parts to the Caterham parts counter tomorrow morning to confirm that I have all the correct spec bits. A quick call with Darren this afternoon confirmed his belief that the belt should be a 4-vee. I'll keep you posted. Link to comment Share on other sites More sharing options...
Nick Green Posted August 3, 2001 Share Posted August 3, 2001 A friend's recently built SLR, with a DS, has a Minister sticker by the blocked off cam-cover breathers, stating categorically that the breathers are meant to be blocked. The engine clucks. From what people have said so far, would it be reasonable to say that that is just Minister's opinion, and that one of the breathers could be opened ? That is how I read what has been written so far. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted August 3, 2001 Share Posted August 3, 2001 If you are going to open a breather it *must* be filtered. You can't have a gale of any old muck whistling into the engine. While the clucking perhaps indicates an abuse of the seals, it perhaps indicates that there are extra forces at work keeping the oil inside the engine. I am not motivated to modify the installation because of clucking, but because of concerns about giving the engine the best chance to staying alive with a healthy oil supply. Link to comment Share on other sites More sharing options...
oilyhands Posted August 3, 2001 Share Posted August 3, 2001 I dont think the clucking is air coming past the seals, I think it's the pump running *dry*, if /when there were / is oil in the sump at idle then the clucking stops even though just as much volume is being evacuated from the engine cavity. I've heard it before on twin scavenge systems where one pump is dry and the other is still evacuating oil, add oil to the sump or put the car on level ground and the clucking goes away when both pumps have oil to shift. The problem only appears at idle where blow-by is minimal and oil circulation is at a low ebb, at this point the pumps capacity exceeeds the production of blow-by and oil volume, ignore it.. I've seen Peters DS belt arrangement, I think it needs a heftier belt *and* two heavily shouldered pulleys to prevent the belt being shed by belt-grow. Mikes proximity sensor is a good early warning system too. Oily Edited by - oilyhands on 3 Aug 2001 17:35:11 Link to comment Share on other sites More sharing options...
Paul Ranson Posted August 3, 2001 Share Posted August 3, 2001 My Swindon irrelevant installation uses a cogged belt like a miniature cam belt. Apparently safe to huge rpm. OTOH you have to remove the engine to change the oil filter. Paul Link to comment Share on other sites More sharing options...
Rob Walker Posted August 4, 2001 Author Share Posted August 4, 2001 Peter its sounds like you have zi wrong belt fitted or departed. Just checked my belt and its a 3PK 0768 which means 3 grooves and 768 mm in length. AFAIK its a Rover power steering belt you should be able to get one from Halfords or any Factors. The Gold scavenge pump has a 3 grooved pulley and I am running with the R500 reduced diameter crank pulley. The dry sump drive grooves on this pulley are identical in both shape and diameter to the original ultrasonic crank damper pulley. Hope this helps. If you have been running with a 4 grooved belt it could explain why your dry sump belt went AWOL. Rob. Edited by - Rob walker on 4 Aug 2001 14:10:10 Edited by - Rob walker on 4 Aug 2001 16:41:18 Link to comment Share on other sites More sharing options...
TorAtle Posted August 5, 2001 Share Posted August 5, 2001 Is the breathing located at the top of the swirl tower because Caterham chose to retain the internal pump? And would the benefit of this be that the oil would return faster to the sump (being pressurised), not only fed down by gravity? Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now