Oil Pressure Issue

Having had a few passengers in the car who own Caterhams, they all commented on the low oil pressure my gauges were showing for a 420R. Mine was basically showing (when warm) an idle of about 1 bar (which is just above the red line), and under load it goes up to about 2-2.5 bar. When cold it typically showed about 1-1.5 bar more due to the oil being thicker at that temperature. The car sounds fine (no knocking) and the oil level is correct, not only that, the oil is definitely being circulated around and also spat out into the catch tank. To start with this was pointing to the sender of gauge being at fault.

Caterham technicians got back to me on this with the following technical details:

The 420 dry sump oil pump is fitted with an oil pressure relief spring which we reduce in length by a predetermined amount to avoid running into power drop off issues which can occur with excessive oil pressure, as it is assumed that most customers using a dry sump equipped model will use their cars on track. This means that the oil pressure values seen on a 420 will be reduced slightly in comparison to those seen on a wet sump 360 for example.

Upon initial start up when the oil is cold, I would expect the oil pressure should sit between 2.5-3.0 bar at idle, raising to between 3.5-4.0 bar with increased revs.

Once the oil has been warmed up to operating temperature, I would expect the oil pressure should sit between 2.0-2.5 bar at idle, raising to between 3.0-3.5 bar with increased revs

With this in mind I decided to investigate further, first I tested my gauge with a fellow owners gauge, both read the same, meaning the gauge was not at fault.

I needed to now test the sender, which often is to blame. I decided the best way to rule out the sender, was to test the oil pressure mechanically. I'd already had my eye on some stack gauges prior to this anyway, and decided to invest in a mechanical gauge, and a matching temperature and water gauge, which I will fit during my next oil change which was going to happen any time now anyway. You can see the results of the new gauges in this last picture.

So after now fitting the mechanical gauge and completing a service/oil change, my mechanical gauge confirmed that the oil pressure being reported by the sender was correct, meaning I have low pressure somewhere in the system. I've booked the car in to Caterham Silverstone so they can investigate further because anything oil pump/pressure related is best now looked at by a professional, I believe the oil pump is inside the engine itself so not a job I can easily do. The pressure is still going up under throttle/load and the oil is being pumped around the system so I've been told it wil be OK to drive for the most part, this will also help with the diagnostics.

On with the diagnostics, first I was asked to get a video of the engine starting up from cold, showing the pressure:

Once the engine was at normal operating temperature I pulled over to show the idle temperature when at a good running temperature. Note I have added a switch under the knee panel on the drivers side so I can toggle between water and oil temperatures.

To complete the set I took a video showing the pressure rising when pressing the throttle to show that pressure does increase when under load.

The resolution is documented in the following post: