Technical High oil pressure

[koalar]

does anyone know what it should be Is this a real fault.

all I can find is

Crank the engine for at least 10 seconds
Is the oil pressure between 0.8 bar (11.6 psi) and 7.5 bar (108.8 psi) ?

This is how the thread started.


Four pages later, relevant questions have remained unanswered.

As stated already, yellow triangle does not warn of high oil pressure. There does not appear to be a sensor that measures the oil pressure.

I've asked the question before, more than once, "how did the garage get from a yellow triangle to oil pressure?" Why will you not tell us this?

You have a yellow triangle. What else is wrong? Not what has been diagnosed, but what else can you as the driver see or feel is wrong with the way the vehicle operates?

Does the oil pressure light illuminate when the ignition is turned on?
Does it then extinguish as the engine starts?

The yellow light is very likely a simple issue, simply fixed, if we can stop fixating on the oil pressure.:bang:

 

[1947Guy]

I thought i would add a conclusion to my problem. The yellow triangle was on because the oil pressure sensor 'which I had already replaced once' was not making contact with the earth strip and consequntly not talking to the ECU. The sensor is screwed into a plastic housing and needs an earth return to complete the circuit.
As for the high oil pressure, I have decided to continue driving the car, as there is no other faults and the 80 PSI I spoke about, might be needed to power the hydrolic valve system.
Whats the worst that could happen, it could go BANG one day. Happy days.

 

[Pugglt Auld Jock]

Thanks very much for bringing us up to date on this. So the yellow triangle was a "red herring" after all - as I think most of us were suspecting.

We're still left with the high oil pressure though. In my experience, an oil pressure sensor switch is a simple spring loaded on/off switch so can't give an actual pressure value. So the question then is was this 80psi reading obtained from the oil gallery or from somewhere in the multiair high pressure side? My guess would be the oil gallery because if taken from the multiair high pressure system I imagine it would be pulsed and peak values would be much higher?

So, if we assume it was taken from the oil gallery (I'd be screwing the pipe into the oil switch hole) all we need to know, in this instance, is what the max pressure is specified to be (if tested with the engine cold this might well be the blow off pressure of the pump relief valve).

A pressure of 54psi (or was it 45?) has been quoted somewhere earlier in the thread but Koalar gives a cranking procedure above which seems to quote a much higher pressure. If the max permissible really is 7.5 bar then it's the highest I've ever seen for a cranking pressure - but maybe the valve module oil supply needs this?

 

[DaveMcT]

The MultiAir system uses two normal cams to drive the exhaust valves. A third cam drives a hydraulic piston which powers the inlet valves. Valve duration and lift is controlled by bleeding away oil from that circuit. The engine lubrication system never gets to see any of that hydraulic pressure.

 

[koalar]

I couldn't find the spec for this models pump


I did find a few other similar pumps and their relieve valve is set for 145 PSI


I didn't post as its might have been a red herring and not a fair comparison



coincidencely the max pressure for most third party pressure switches is 145 psi. So fairly marginal.

 

[Pugglt Auld Jock]

Thanks Dave. Although I have no experience of the Multi/twin airs, I presume the oil supply is fed to the multi unit from the normal oil supply the engine uses (by which I mean it's primed from the in sump oil pump via a gallery in the block/head? It just occurred to me that the normal running pressure might be a little higher than on an "ordinary" engine due to the demands of the multiair? Also I don't know if you can tap into the multiair high pressure side but if you could, and the high reading was being obtained because of this, then you would expect to see a pulsed output not a steady reading, hence my comment about the "pulsed" output.

In conclusion, I probably ought to stick to engines I know and not speculate about ones I don't!

 

[DaveMcT]

MultiAir is very clever - the inlet valves on each cylinder have their own hydraulic pump and actuator. You could say the cam followers/rockers are replaced by a hydraulic lever. There is a throttle valve, but engine power is almost entirely controlled by the hydraulic valve lift and duration so the inlet manifold sees more or less atmospheric pressure. Valve timing is fixed. It's not a fully electronic cam.

I had thought the MultiAir oil would be trapped for life like it is in hydraulic tappets, but thinking about it the oil is bled away by he valve lift control so there will always be a through flow. Regular oil changes will be really important. It may even be worth fitting a 1 micron bypass filter.
https://www.thebestoil.com/products/bypass-oil-filtration/

This explains what they do on HGV diesels
https://www.overdriveonline.com/the-bypass-filter-advantage/

This is part of a series about the engine. His car is the MX5/124 but the engine is much the same as used in all MultiAir Fiats.
https://www.youtube.com/watch?v=DnSefxN2FQ0

 

[Pugglt Auld Jock]

This chap makes a few very interesting points
https://www.youtube.com/watch?v=A05WsAi_6to

 

[DaveMcT]

This chap makes a few very interesting points
https://www.youtube.com/watch?v=A05WsAi_6to

He says they can open and close the valve twice in a cycle. Makes me wonder why they have not used a normal hydraulic pump and driven both inlet and exhaust valves. Perhaps that would contravene Konisegg patents. But saying that, the very first "electronic valve" engine was made by Lotus. Early versions had a computer the size of a washing machine and could not rev above 3,500 because it could not process fast enough. But it did not need a starter motor and could shut down cylinders when not needed.

http://www.lotusdriversguide.com/Press/Camless_engine.php