156 Oil Pump/Pressure Specs....? - Alfa Romeo Forum
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156 Oil Pump/Pressure Specs....?

The oil pump of the twin spark engines has a pressure relief valve that opens when pressure reaches 5 Bar in order not to overcome that figure.

The figures I found for the twin spark (from DTE: Documentazione Tecnica Elettronica) are…
Oil Pressure Range Bar: 3.5 - 4.5/4000rpm & 1.0 – 1.5 in idling speed.

The figures I found for 2.5V6 are…
Oil Pressure Range Bar: 3.0 – 0.1/5.000rpm & 0.3 – 0.1 in idling speed.

1)As you can see the figures for the 2.5V6 are obviously wrong (3.0 - 0.1)…does anyone knows the correct figures for 156 24v 2.5V6 & 3.2V6?

2)Also I need to know ''when'' the pressure relief valve opens in twin spark/2.5 & 3.2V6…?

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Last edited by DJTaurus; 29-01-08 at 21:26.
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Re: 156 Oil Pump/Pressure Specs....?

on the V6 (alfa not GM) it should be 0.88-1.88bar at 750rpm and 5bar +/-10% at 4000. obviously the actual pressure will vary a lot depending on the oil you use and the temperature it is at.

relief valves should not be considered as only open and closed, they will be open by a certain amount at a certain pressure, the net effect is a fairly constant operating pressure regardless of rpm. on the V6 i would expect the valve to start opening at 5bar and be fully open by 5.5bar, but it depends, and every relief valve is different (since they use a spring).
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Re: 156 Oil Pump/Pressure Specs....?

I have no experience with V6, but I have an oil pressure gauge on my TS. After a cold start the pressure holds on 4,5 bar at idle and rises to 5 - 5,5 bar when driving. As the oil warms up the idle pressure drops. When oil temp is anywhere above 70 degrees, the idle pressure is 1,5 - 2 bars. When driving, it rises with the revs and somewhere above 2500 - 3000 rpm it reaches 4,5 - 5 bar and than it is stable up to the rev limiter.
I think the pressure relief valve opens disregarding the oil temperature and engine revs anytime when the pressure is above 5 bar. It may be opened slightly even at idle after a cold start when the oil is thick and pressure is build up rapidly but when the engine is hot it can start to open later, when the pressure rises above a pre-set value (5 bar aprox.)

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