Is max oil pressure determined by the PRV

[Tim D.]

Hi all

Been musing, when the engine is hot is the max oil pressure above 2500 rpm say, determined by the pressure relief valve. I had a bored moment and watched a load of YouTube videos of TR6s being driver around. The oil pressure at high Revs seemed to be equally split between 50-60 psi and 75psi+ . I only looked at cars which had warmed up as per the temp gauge. Given there were 2 clear groups I thought this couldn't be general engine bearing wear that was determining it.. has to be the PRV? 

So do we think there are 2 different strength PRV springs out there. 

Also interesting, the one race prepped car seemed to have a max oil pressure of just over 50psi. 

It was also interesting to see that in almost all cases the max oil pressure was reached at about 1800 rpm in most cases. 

As I said, I was bored. 

Tim

[John McCormack]

15 minutes ago, Tim D. said:

Hi all

Been musing, when the engine is hot is the max oil pressure above 2500 rpm say, determined by the pressure relief valve. I had a bored moment and watched a load of YouTube videos of TR6s being driver around. The oil pressure at high Revs seemed to be equally split between 50-60 psi and 75psi+ . I only looked at cars which had warmed up as per the temp gauge. Given there were 2 clear groups I thought this couldn't be general engine bearing wear that was determining it.. has to be the PRV? 

So do we think there are 2 different strength PRV springs out there. 

Also interesting, the one race prepped car seemed to have a max oil pressure of just over 50psi. 

It was also interesting to see that in almost all cases the max oil pressure was reached at about 1800 rpm in most cases. 

As I said, I was bored. 

Tim

When the engine is hot the oil pressure should not be enough to cause the pressure valve to open. Oil pressure will be a function of pump output and the wastage in the engine.

I fitted a new oil pump a few months ago. Before the new pump oil pressure was 65-75 hot above 2000rpm and 25-30 at idle. It is now 30-35 at idle and 75 psi above 2000rpm.

When cold the oil pressure is about 80 which must be the valve opening point as it doesn't vary much above about 1000rpm. This oil pressure might seem a bit high but not much, I suspect the gauge reads 5 psi high.

[Tim D.]

4 minutes ago, John McCormack said:

When the engine is hot the oil pressure should not be enough to cause the pressure valve to open. Oil pressure will be a function of pump output and the wastage in the engine.

I fitted a new oil pump a few months ago. Before the new pump oil pressure was 65-75 hot above 2000rpm and 25-30 at idle. It is now 30-35 at idle and 75 psi above 2000rpm.

When cold the oil pressure is about 80 which must be the valve opening point as it doesn't vary much above about 1000rpm. This oil pressure might seem a bit high but not much, I suspect the gauge reads 5 psi high.

John, this is what I thought. But I was just intrigued that the majority of TR6s on YouTube seemed to have 50-60 psi max. 

[DRD]

2 hours ago, Tim D. said:

John, this is what I thought. But I was just intrigued that the majority of TR6s on YouTube seemed to have 50-60 psi max. 

It's worth remembering that although the temp gauge might indicate the engine has warmed up it takes much longer for the oil to get hot. Mine is about 60psi when hot but will sit at 75psi for about 30mins to start with. 

[Tim D.]

4 hours ago, DRD said:

It's worth remembering that although the temp gauge might indicate the engine has warmed up it takes much longer for the oil to get hot. Mine is about 60psi when hot but will sit at 75psi for about 30mins to start with. 

DRD yes absolutely. I have am oil cooler and you can see when it kicks In. Usually after 30mins. Also get 60psi

[Andy Moltu]

The max oil pressure is determined by the PRV if the pump is capable of delivering enough oil to reach the PRV operating pressure.

Other factors affect the ability of the pump to reach that pressure are the viscosity of the oil and bearing clearance, oil temp.

[astontr6]

17 hours ago, Andy Moltu said:

The max oil pressure is determined by the PRV if the pump is capable of delivering enough oil to reach the PRV operating pressure.

Other factors affect the ability of the pump to reach that pressure are the viscosity of the oil and bearing clearance, oil temp.

My car has always had high oil pressure even from new, my tick over pressure is 50 psi hot. and my running oil pressure is 75 psi above 2000rpm, hot. But of course I do not know how accurate my oil pressure gauge is? When cold my oil pressure goes above 75 psi to about 85psi as a guess as I assume that the PRV has opened up? But for years the actual PRV valve has been subject to poor quality replacements and when rebuilding an engine it s/b lapped in I doubt that many people do that? Also the clearance of the rotor to base plate on the oil pump should only be .002"? Lastly the cam shaft bearings must be in good condition or should have been line bored to accept Triumph spitfire circular shell bearings to restore pressure.

Bruce.