7 replies to this topic

[snotvomit]

I've mentioned this on my other thread about the squeal but it might be a topic on it's own. Does anyone know the running oil pressure for the Z20LET? I assume these values are taken at a certain number of revs but I can't find any confirmed figures as to what the engine oil pressure should be - I have searched and found a suggestion of 90 psi but that was discussing turbo oil restrictors on an Astra so I'm still not sure. Thanks for any info.

[vocky]

according to Nev in a previous post around 70 psi

http://www.vx220.org...ich-engine-oil/

[snotvomit]

Thanks - so around 70psi at high revs, judging from that post. I suppose the question that follows on from that would be what is considered to be the minimum satisfactory pressure at tick-over. 50 Psi?

[vocky]

30 psi would be a good (hot engine) tickover oil pressure

Edited by vocky, 15 April 2012 - 08:12 PM.

[joshua]

My VXT even with oil squirters is always 90 psi above 2500rpm and never drops below 45 psi. According to Vauxhall this is normal.

[snotvomit]

OK, so I will assume 30-45 psi on tickover and 70 - 90 psi at medium revs. Thanks guys.

[Nev]

Hi, I've just re-read that old post of mine. Just for clarity I would NOT recommend installing a pre-turbo oil pressure regulator. I base this on 2 things. 1/ The first is that during my R&D for my new engine, I made a long distance phone call to the techinical/design department of Garrett in the USA. I spent 25 mins on the phone talking to one of their very helpful turbo designers, the upshot of which was: It is better to run too high oil pressure to your turbo than too low. 2/ Those ebay oil restrictors do not work by restricting pressure at a certain value. They just restrict flow, which in turn resricts presure at all RPM, thus you may not run enough oil pressure at low RPM. Also, that small hole may completely block oil flow when the oil is thick/viscous during a cold start, which is clearly very bad for the turbo. Also, for clarity, during a very cold start (ie thick oil) you can expect to see oil pressures reaching 120 PSI in parts of the Z20LET engine. Also, for clarity, the oil pump is mechanically driven, and thus oil pressure increases in a roughly aritmetic progression with RPM. Thus if you rev your engine very high, expect to see greater oil pressures. I have heard that the OEM oil pump can/will start to cavitate at approx 7750 RPM (which is why I set my red line at just 8000 on my particular engine) - this is obviously not desirable! HTH.

Edited by Nev, 16 April 2012 - 09:08 AM.

[snotvomit]

Thanks Nev. I certainly won't be using anything to reduce pressure to the turbo. The concern here is that maybe there is a loss of oil pressure to the top end of the engine and something in the head has been starved of oil - hence the squeal/whining noise. It doesn't seem likely but it's worth a check. No-one seems to know what the hell this noise is. It's bloody loud and it sounds like it's coming from the head/cambelt but all the usual suspects have been eliminated.