Vic
If at a certain (say 3000) rpm the relief valve becomes full open, any
additional oil flow from increased rpm will result in increase oil pressure.
Remember, the oil pump is a positive displacement pump. The faster it turns,
the more volume/min it pumps. I think it's a fairly linear relationship. The
increase in pressure is a result in the increased flow. Since oil is
incompressible, the increased flow through the system results in more
pressure. I'm guessing, but I would think that the flow restriction through
the oil galleries and bearings is pretty constant, regardless of rpm. I
imagine that the system reacts something like the following:
At idle the pump is spinning relatively slowly therefore delivering a small
amount of oil. The relief valve remains closed because there isn't much flow
resistance at this small flow rate, therefore very little resulting pressure
(sometimes referred to as "head" or "head pressure").
As engine speed increases, oil flow will increase proportionally to pump
speed. At some point, the increase in flow (therefore pressure) will cause
the relief valve to begin opening. Depending on the flow restriction through
the relief valve, the oil pressure will continue to rise with rpm until the
relief valve is fully open. At this point the oil pump again will see a
fixed resistance and oil pressure will increase a little faster with rpm.
Walt
> -----Original Message-----
> From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net]On
> Behalf Of Vsnively@aol.com
> Sent: Monday, July 01, 2002 5:37 PM
> To: Walt_Boeninger@hp.com
> Cc: 6pack@autox.team.net
> Subject: Re: Oil Pressure
>
>
> Walt,
> Same is true on my '95 Ranger---the oil pressure needle stays
> at half-scale
> except
> when engine is off. Interesting sidenote---my TR6 service manual
> says that
> the oil pressure idiot light extinguishes at 3 to 5 psi. I would
> think that
> by the time that light comes on, it's way too late. Also, I'm a little
> baffled by the relief valve setting. The
> manual states 53 psi. I have a basic understanding of hydraulics,
> so how can
> oil
> pressure indicate above 53 psi if it dumps over the relief ?
> Thanks.
> Vic Snively
> 75 TR6
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