[DeTomaso] Remote oil filter setup

[Steve Hawkins]

Generally increasing flow requires more volume and requires a larger pump,
increasing pressure requires multiple stages on a pump.  Centrifugal pumps
are usually low pressure high flow pumps which is the basic design of the
Cleveland oil pump.  

In a system that has a constant internal capacity that doesn't change one
has to raise pressure to raise flow.  This can be accomplished by raising
the relief pressure or by using a higher flow pump which will raise
pressure.

Steve

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Julian Kift
Sent: Tuesday, May 05, 2009 7:52 PM
To: asajay at asajay.com; De Tomaso List
Subject: Re: [DeTomaso] Remote oil filter setup



If the passages are the same size, and you try to move -more- oil through
them at any given moment (higher volume), doesn't that by definition have to
increase the pressure?

 

>> Not necessarily, pressure is resistance to flow, so in an open pipe 
>> (with no head increase) there is no increase in pressure.

Put simply, in a reverse kind of way.... If I increase the pressure on my
water pressure tank (supplying the house), I can fill a bucket with water a
lot faster (higher volume).

 

>>Yes, beacuse there is no resistance to flow; P1V1 (the tank) = P2V2 
>>(the hose) so you increase P1 at the tank and as there is no pressure 
>>change at the hose V2 increases.
 
So what is the relationship of higher volume and higher pressure and at what
point do you get diminishing returns?

 

>> Depends what and how far you are pumping and line losses etc. In an 
>> engine too much pressure is as much a bad thing as too little. A hot 
>> engine should idle at around 20 psi and I've heard rule of thumb is 
>> 10 psi for every 100 HP at WOT.


To me, a "high volume" oil pump -implies- higher pressure, and... a "high
pressure" oil pump -implies- higher volume.


>>On an oil pump there is an internal relief spring, dictating at what 
>>pressure the pump internally bypasses i.e. the max pressure it pumps. 
>>The high volume pump will internally bypass at a lower pressure (than 
>>a high pressure pump). The pressure it produces in the engine depends 
>>on resistance to flow i.e. leakage around bearings, frictional losses, 
>>clearances etc.

 

>>A high pressure oil pump will require greater resistance to flow 
>>before it internally bypasses and is designed for applications where 
>>there is a lot of leakage (pressure loss) i.e. a worn engine or one 
>>designed with slide rule tolerances.

Julian

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