Xflow oil pressure

[McBreadhead]

On my 1760cc Xflow I'm getting just under 3 bar on cold start up at idle, then just under 2 bar on hot idle.  I've also noticed the oil pressure light takes maybe 10 seconds to extinguish after start up.

When cruising at 2500-3000 rpm I get 2.5 bar,

When returned to base after 20 mins, I get only 1 bar at 1,000 rpm. This is scary but oil pressure light doesn't illuminate. Oil level is at full mark on dipstick with no discernible loss. 

Gauge is standard Caterham, not mechanical. Engine runs a high pressure oil pump and rebuilt only 4K miles ago and not tracked nor ever taken to rev limit. 

It's due an oil change but any thoughts as to why I'm seeing such low readings?

[Tazio]

They are low, so it's either the sensor, the gauge or motor, so I'd start with the sensor, though ideally I'd put a mechanical gauge on though.

[virden]

I agree with Tazio, renew the warning light sensor and change the gauge with a capillary version, you can get both from Demon Tweaks, or CBS. 

Are you using 20/50W oil?

[Roger King]

Wot he sed (about a mechanical sensor), but the figs are actually not too bad. One bar at idle when hot after a run is OK; a high pressure pump will make no difference at all at tickover because they simply have a stronger spring in the relief valve which has no effect until the pressure reaches much higher levels. To increase idle oil pressure you need a high pressure/high capacity pump. Ideally, I'd like to see 3.5 to 4bar at high revs - what are you getting at around 5000rpm? If you're anywhere near those figures there is probably nothing wrong, although I can't explain about the light taking so long to go off.

You probably have a standard road type light switch which will would normally be set at around .4bar. Unfortunately these lights are really only of use to tell you that your engine is already b*ggered. A competition light switch will be set to nearer 2 bar. This will give you advance warning that something is going wrong but you have to put up with it coming on all the time at low revs.

[jonsymons]

McB - according to my Haynes manual for late 1970's Escorts (ie with Crossflow engines) the following are the minimum oil pressures at 80degC:

700rpm - 8.5lbf/in2 (0.6 bar)

2000rpm - 21lbf (1.45 bar)

I defer to those in this thread with much greater knowledge than me to advise on your questions but I thought the above figures might be of some interest (comfort?) to you.

[McBreadhead]

Thanks all for your comments. 

Car runs Valvoline VR1 20-50 mineral oil. 

I can confirm  oil pump is both high capacity and high pressure as per receipt from Burtons. 

As for what happens at 5,000 rpm I need to take her out to explore and confirm but I'm pretty sure the gauge shows 3.5+ bar so maybe I'm getting cross eyed for nowt. It's just the 1 bar at idle that concerns. Could the oil collector be too close/far away from the sump floor I wonder? Is there an optimum position as I recall the engine builder had to raise it a tad?

Car is going to James Whiting soon so perhaps he can test with a mechanical gauge.