Trackday Oil Starvation

[Tony Martyr]

Nigel, it is the size of the orifice at the top of the apollo tank that determines the pressure and I assume it has been sized so as to still maintain the normal system pressure of circa 4 bar - although my system dropped a little under on fitting the device.

Just going back to the purpose of the first posting of this thread -How many k series in non-race caterhams have had major failures put down to oil starvation on tracks?

The most acute loss of pressure I have noted was on the LeSept trip on Magny Cours GP circuit where there is a long long fast right hand bend before the back straight. As the power went full on the pressure guage was at about normal idle pressure with oil that was around 110 degs C. That was 10000 miles ago.

 

[Peter Carmichael]

The Apollo works because air will flow through a small orifice far quicker than oil will. The bleed at the top of the Apollo tank is a restrictor (1mm I think). Even with 4 bar pushing across this, not much oil slips through - you can disconnect the cam cover hose and bleed it into a jar if you doubt this. When the swirl and flow in the Apollo tank has separated air to the top of the tank, the air slips tidily through the restrictor. It is important that the Apollo flows from top to bottom - I just fixed one where the flow was the wrong way round.

 

 

Does the effectiveness of the accusump depend on?

a) How good the oil pump is at pumping air (i.e. can the pump pass enough air to keep the apparent pressure high until the air reaches the bearings)

---

 

Not really. "Effectiveness" of the pump is mostly to do with over-capacity. If you have over capacity then in normal use, the pressure relief valve is dumping a lot of oil back to the low pressure side of the pump. When a pump with over capacity pumps air, the pressure relief valve closes and the volume flow to the bearings is not affected that much.

 

 

b) How long the accusump takes to pass all of its oil (I presume Peter thinks all the accusump charge goes out of the pressure relief valve because of the pressure in the accusump)

The Accusump is charged to normal operating pressure of the oil system - this is above the opening pressure of the pressure relief valve. As the Accusump starts to empty its oil into the oil system, its'spring pressure starts to drop away, so the pressure relief valve starts to close. Up until the point where the pressure relief valve closes, the Accusump is just throwing oil out of the pressure relief valve.

 

c) The length of time the oil pickup is in open air (because of b).

This will affect whether the Accusump will mask the symptoms of surge (pressure drop), but does not affect its inability to remove air from the oil.

 

Is it the case that different mixes of a, b, and c would mean that sometimes an accusump would work (in some engines, on some corners) and sometimes it wouldn't (in other engines on other corners).

 

It is my opinion, based on the reasoning that I have set out that the Accusump is ineffective in most, if not all, circumstances.

 

Also Peter, what do you think about the usefulness of the accusump on engine startup?

 

A good synthetic oil doesn't run off surfaces and leaves a film intact in the bearings. The bearing loads on engine start and idle are very low. Most of the "engine wear" that we get told about at start up is down to acid condensates and is nothing to do with metal to metal contact. Some annoying oil adverts wwere recently pulled from TV by trading standards because they implied that metal to metal contact was the de facto state of a started and running engine unless you used their product.

 

To add grist to Tony's mill. My 1.6 Supersport engine did ~12-15 trackdays (Oct 97 to May 99) and 20,000 miles before I fitted an Apollo tank. It was certainly surging, with the pressure dropping to idle pressure and consequent air through the bearings and followers. The bottom end has not yet needed attention despite this abuse. I am happier to have the Apollo tank in situ, but didn't fit it until I had worked out how exactly it helps.

 

Certainly the first SLR racers were reliable with the Apollo tank and unreliable with the dry sump.

[Peter Carmichael]

I have been corrected off line about the oil disappearing out of the pressure relief valve. The Accusump plumbing includes a flap valve to prevent this.

 

You could also achieve this by plumbing in after the oil filter if it has an anti-drain valve.

 

It doesn't alter the matter of air ending up in the bearings.

[Rob Walker]

Peter,

 

I am affraid I do not agree with you that the pump can pump air, it is as you rightly say a volume device it can pump oil with air in but not pure air, put an old pump on an electric drill if you doubt me and hence the need for the pump to be primed with oil on assembley. In my posting I said that the pressure was created by the pump forcing a volume through the oilways and that it was this restriction that caused the oil pressure not the pump.

[Peter Carmichael]

I think we are destined to disagree on this one.

 

I am routinely remiss in priming the oil pump and it does self prime.

[andy oliver]

Accusumps are made by Canton Racing Products e-mail

info@cantonracingproducts.com.Perhaps they should be allowed a say in this debate?

[Rob Walker]

Peter,

 

The reason your pump self primes is that the oil level in your Belltank is higher than the pump therefore the oil fills your pump by gravity. This is not the case with the wet sump set up, when the pump has to lift the oil out of the sump. If you look at the pump internals the rotor runs a clearance of up to .006" for the Rover sintered rotor and .010" in the case of the QED steel rotor within the outer rotor, in view of this clearance the pump will not move air unless there is sufficient oil present to make a gas tight seal between the rotors.

 

Edited by - Rob walker on 3 May 2002 18:52:18

[kjp]

Peter

 

I think that perhaps our 'K'series engines require more oil pressure than you imply. I agree that oil pressure in the gallery is small compared to the hydrodynamic bearing pressure but you do have to get oil into the crankshaft in the first place. The crankshaft is also an oil pump which trys to pump oil out of both its main and big end journals. The pressure required is proportional to engine speed and journal diameter. Racing engines which run what we would consider alarmingly low oil pressure (F1,Cart) must feed the oil through the nose of the crank.

 

eh

 

maybe

 

KenP