Oil pressure

[StewartG]

My Vx engine has developed the alarming practice of less oil pressure with more revs has anyone else got this problem? The oil pressure is good at idle even when hot but above about 3 thousand revs and/or under hard acceleration the pressure dives. I've changed the foam in the sump an am useing 5w40 Volvoline. I originally thought it was oil surge until I noticed it did it at a standstill. I think I feel a lightening of my wallet coming on.

 

Edited by - stewartg on 11 Dec 2000 20:56:50

[Alex Wong1697456877]

Was the baffle fully intact? Mine had broken apart and for ages, I had some bits of baffle blocking the oil channels from the top to the bottom of the engine. This caused oil to fill up the top half of the engine when revving. I only realised the cause of this when I took my engine apart.

 

Alex

[Swiss_Tony]

I have found a similar problem with my vx.

I tried changing the baffle and the oil.

Also I got a tappet noise after sustained high revs

My cure was to change the sump to one without a

foam baffle. No more problems!

The reason for this (in my opinion) is the oil

cannot return quickly enough through the foam.

My new sump has a strainer on the oil pick up pipe

which I feel safer with.

Has anyone else had this problem?

 

James

[Alex Wong1697456877]

James,

 

Do you not get problems with surge without the baffle or has the pan been modified?

 

Alex

[Swiss_Tony]

Alex

 

No problems with surge yet.

The sump has some baffle plates around the oil pick up

and it has a baffle plate the whole length approx half

way up. If you look at the inside it seems very well

designed. It is not a standard sump, its a cast ali

job.

 

James

[StewartG]

Thanks for the replies James and Alex. I've been thinking along similar lines. When draining the oil it doesn't run out very fast, just a dribble, presumably the foam does a good job of trapping even the thin oil I'm using and presumably the oil pump has a struggle sucking enough oil out of the foam to maintain pressure at high revs.

My engine has a sort of dished plate sandwiched between the crankcase and the sump which squashes the foam as the sump is bolted up under the engine. This must make the foam denser and give the oil a harder time getting through.

I think my next move might be to cut some of the foam out, making it into a sort of grid rather than a block or I might try running the engine with no foam to see what happens.

James, where did you get your sump from? I'm using the standard Caterham alloy one.

Alex, The foam had not brocken up and the pickup pipe has a strainer so I doubt any bits could get up into the engine

Are we the only ones with wet sump Vx engines to have this problem?

 

Edited by - stewartg on 12 Dec 2000 00:16:09

[Swiss_Tony]

Stewart

 

I would not recommend using the sump without the sponge as it

is the only form of baffle in the sump. The oil surge would be

a major problem.

The plate you refer to is the windage plate which basically

helps to prevent the oil from splashing onto the crank. If this

happens it slows the engine down ie less bhp etc it will also

tend to come out of the breather pipes etc.

The sump I got is from SBD (sbdev.co.uk from memory)

It cost £200 plus the vat and comes with pick up pipe with a

strainer.

The main drawback with this sump is the ground clearance.

It is a bit deeper than the standard Caterham sump.

I cannot remember by how much but I can measure it if ness.

If you do go for one check with SBD on how much oil to fill it

with. The sump seems well made but seems thinner on the bottom

so maybe not as strong as the standard one?

Also the flywheel is left exposed so I have made an ali plate

to cover this.

If you do go for one dont forget to drill out a hole for the dipstick.

I seem to remember that SBD call it a "lowline sump" suitable

for w*******ds and rwd installations.

Have you modified your breather system?

I found this to help reduce oil out of the breather pipes.

 

Hope this helps

James

 

Forgot to add that I have not grounded it out in 1500 road miles

 

Edited by - James on 12 Dec 2000 23:52:29

[StewartG]

Are James and myself the only ones to have this problem? I've got 2.5 bar oil pressure hot at idle but only 2 bar when accelerating hard or taking right hand corners, left handers give 4 bar but most race track corners are right handers and round abouts go that way too.

I'm assuming my engine is basically sound because the oil pressure is fine at idle

I'm looking at four scenarios

1) Stop looking at the oil pressure gauge more than the road £0.

2) Invest in a SBD baffled sump £200.

3) Invest in an Accusump, has anyone tried this? £300ish

4) Invest in a dry sump installation £1500-£2000 fitted

The parts for dry sumping come to about £800 but do I need a degree in fluid dynamics to install them myself. Has anyone attempted DIY?

Alex is your engine dry sumped? Did you do it?

 

[Alex Wong1697456877]

Stewart,

 

You're getting oil surge. It drops on right handers as the pickup lies to the right of the sump. Turning right sloshes the oil to the left. Accelerating sloshes it to the back. Hard braking also causes surge but usually isn't noticeable as you're off the throttle. My undamped digital gauge shows it to happen though. I get those symptoms from underfilling or when oil is low. I fill mine well above the max line on the Vx dipstick (by over 1cm). The Shallower pan makes this necessary. From empty, mine takes 4 litres easily. The excess a minimal amount, if any, just blows out the breather. Have you modified your can cover plate? Mine is cut away to just a square covering the breather outlet. SBD recommended this. It stops it blowing oil so easily.

 

I'd suggest topping up the oil by another litre and trying again. Make sure your breather bottle is empty before driving off then see if any blows out.

 

Alex

 

Edited by - Alex Wong on 17 Dec 2000 19:43:55

 

Edited by - Alex Wong on 17 Dec 2000 19:45:17

[Chelspeed]

> I'm looking at four scenarios

> 1) Stop looking at the oil pressure gauge more than the road £0.

 

Thats a short term solution, probably not recommended as a long term solution.

 

> 2) Invest in a SBD baffled sump £200.

 

I really wouldn't recomend this on a Caterham. This sump is designed for a westie and is flat bottomed. On the Caterham Vx nose down installation it makes the bottom of the front of the sump extremely vulnerable (mine lasted 3 miles). It's also very light weight which means very thin, absolutely perfect for circuit use in a Westie but not so clever for road use in a Caterham. The pukka Caterham wet sump pan is tapered so that the front isn't lower and the front is very solidly finned.

 

> 4) Invest in a dry sump installation £1500-£2000 fitted

> The parts for dry sumping come to about £800 but do I need a

> degree in fluid dynamics to install them myself. Has anyone

> attempted DIY?

 

Ive fitted an SBD dry sump system myself. Their catalogue used to have a plumbing diagram. I'll see if I can dig out a copy of the old catalogue, give me a fax number and I'll send it to you if I find it. If not I'll sketch my layout.

 

Is 2 grand a price from Caterham? The Caterham system is particularly complex as the oil tank is within the bellhousing so fitting means engine out, new bellhousing, new clutch system etc etc. It shouldn't cost anything like this much to fit a more conventional dry sump system but you then need to find space for the oil tank. I shortened the passenger footwell to fit mine, worked very well.

 

[StewartG]

Alex, I'm trying the more oil solution but Roger King has warned against this as a long term solution. He reckons that significant overfill will cause the crank to hit the oil and foam it up and this will result in less oil pressure with the engine being lubricated by oily air.

I wonder how meaningful the ex Vauxhall dipstick markings are and how much oil is left in the sump when the engine is running, presumably not much or we wouldn't have a surge problem. If a significant amount of oil is circulating the engine it can't be in the sump hitting the crank.

I've also seen a noticeable drop in oil pressure when changing from a short to a long filter. I suspect the bigger filter allows more oil flow which means less pressure.