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Hot Engine Oil Pressures

On my S2 when hot the oil pressures from the dash gauge are:
tick over 800rpm 2.5/3Bar
just over 1000rpm 4.5/5.0Bar
1500rpm and above 4.5/5.0Bar

Lower of the two readings are when the car is very hot i.e. after standing in traffic and fans have been on a couple of times. Full oil pressure indicated once car is raised off tickover really.

_________________
David

 
I think our electronic senders are not the most accurate. I have decided if there is linear movement in sync with revs then all is good.

Incidentally with my 23 year old sender I got similar readings to you David. Since I put a new one on I seem to have a different scale. Do check where your gauge reads with ignition on/engine off. Mines at zero now but with old sender was showing 1!

Stuart
 
I put a test gauge on my 944 2.5L engine because I didn't trust the gauge.
Hot oil pressure aound 3.5bar at idle rising to 5.5 bar at 4500 rpm.
Interestingly, cold pressures were, as expected, higher but I didn't expect to see nearly 8 bar at 4000 rpm with the engine coldish ( i.e run for a minute or two but not up to temperature). I've checked out the oil pressure relief valve and all seems OK so I can only assume that the higher viscosity of the cooler oil must open the relief valve fully but that the flow area through the relief is designed for the oil viscosity at operating temperature (sensible), so that the thicker oil at lower temp creates a higher back pressure between the pump and relief. This is not a problem except that you need a pressure sender that can take 100% overload (normal scale 0-5bar) without damage. Some of the cheaper after market senders won't cope with this level of overload which may be one reason why the OEM one is more costly.
If the sender used cannot deal with the level of overload it will prematurely fail. Just a thought.
 
Tell us more....a surprise like mine where indicated pressures are lower than they used to be??

Stuart
 
Yes, pretty much the same, although my car is far longer in the tooth. I had a new OPS fitted when I had the front crank seal replaced and pressures range from between an indicated 1.8BAR up to a shade over 4BAR when hot.

This isnt helped by the oil that was used, but still, it was enough to start me driving with one eye constantly on the gauge!
 
Ah thanks Simon! Makes me feel better. I have done all my running in with my eyes on the oil pressure gauge. My poor old AFR and boost gauges must be feeling lonely!!

When hot I'm getting bang on 2 bar at idle up to about 4.5 bar once past about 3k revs. That's with new piston rings, big ends and head refreshed inc valve guides seats cut etc. The rest of the engine is still original.

Stuart
 
The specialists I know of who have rebuilt and raced more 944 engines that I could think of all run fully synthetic oil, no thinner than 15W50 or 10W60.
The workshop friends & I have used to prepare/rebore our 944 blocks recommend 15W50. Field experience and user feedback has more value to me than what a global oil reseller may say
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I must say I agree totally re the lower viscosity. A decent quality part synthetic is what I use.

Fully synthetic is belts and braces and (in my view) not necessary for normal engines pootling along doing a few thousand miles a year but essential for long life services.

To preserve your engines in any occassional hobby car, if left standing, I always turn of the main pump, pull the HT lead and turn the engine until I see good pressure before replacing, turning on and starting.
 
I didn't expect to see nearly 8 bar at 4000 rpm with the engine coldish
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My oil pressure (in my Golf Mk1) when cold is over an indicated 110psi for a few minutes when revving normally (from cold)

Drops to 25-30 ish when hot and 90ish psi at full chat (7000rpm).

I questioned this as it threatens to burst the gauge!! as the Stack gauge's top reading is 100psi but am told its quite normal (on the ABF engine I have in the car)
 
Stuart, for piece of mind for both Alasdair and yourself, Id suggest briefly refitting the original oil pressure sender.
 
ORIGINAL: Hilux
To preserve your engines in any occassional hobby car, if left standing, I always turn of the main pump, pull the HT lead and turn the engine until I see good pressure before replacing, turning on and starting.
Click to expand...

I have never understood that one - what difference in terms of wear is it going to make whether the engine is started or only turned over?
In both cases most of the oil will be in the sump, and when the engine reaches idle speed right away after having started, the pump will prime the oil circuit more quickly than when turning the engine over and over untill seeing oil pressure on the dash.
 

ORIGINAL: scam75

I think our electronic senders are not the most accurate. I have decided if there is linear movement in sync with revs then all is good.

Incidentally with my 23 year old sender I got similar readings to you David. Since I put a new one on I seem to have a different scale. Do check where your gauge reads with ignition on/engine off. Mines at zero now but with old sender was showing 1!

Stuart
Click to expand...

My Oil pressure actually reads below zero with ignition off as though the needle is on its stop, I do think having an oil pressure gauge rather than just a low oil pressure light is good to have but seems to create a certain paranoia.
 

ORIGINAL: 944 man

Stuart, for piece of mind for both Alasdair and yourself, Id suggest briefly refitting the original oil pressure sender.
Click to expand...

A good idea Simon but it's in the bin!! I think I am good with it now though, I have adjusted to the change and it's consistent across the board on start up, when hot and rises proportionately with revs.

Stuart
 
ORIGINAL: david924s
My Oil pressure actually reads below zero with ignition off as though the needle is on its stop, I do think having an oil pressure gauge rather than just a low oil pressure light is good to have but seems to create a certain paranoia.
Click to expand...

Is sure does! Especially when you rebuild an engine and change the sender at the same time!!

Stuart

 
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