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> Oil pressure on a /6 under load
SirAndy
post Jun 13 2019, 08:14 PM
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What is the max oil pressure i should be comfortable with (under load) on my 3.6L?

I've been reading 993 manuals and posts all over the tinterwebs and all i can say for certain is that the stock 993 gauge seems to max out at 5 bar but according to all the info i found you'll get there already around 3k rpm and then the gauge just sits at max.

The reason i'm asking is that i'm using a gauge showing psi instead of bar (with the correct sender for that) and 5 bar should be around 73 psi but my oil pressure is substantially above that under load.

I'll idle around 40 psi (sometimes drops to 25-30 when it's really hot) and hit 100 psi as soon as i get above 3k rpm and pretty much stays there.
I've seen as much as 110 psi.

100 psi is about 6.9 bar
110 psi is about 7.6 bar


Question is, am i about to blow up my engine running these kinds of pressures?
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Cairo94507
post Jun 13 2019, 08:50 PM
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Andy- That seems like high pressure to me. Are you certain the sender and the gauge are matched units? (IMG:style_emoticons/default/beerchug.gif)
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SirAndy
post Jun 13 2019, 09:19 PM
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QUOTE(Cairo94507 @ Jun 13 2019, 07:50 PM) *

Andy- That seems like high pressure to me. Are you certain the sender and the gauge are matched units? (IMG:style_emoticons/default/beerchug.gif)

Yes, most certainly certain ...
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rick 918-S
post Jun 14 2019, 03:00 AM
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My 928 engine starts up at 150 psi. Not the same engine. Hot it runs at around 80 psi.
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Mark Henry
post Jun 14 2019, 05:25 AM
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This question I'd ask over on the bird engine rebuild forum.
Odd case with me as I've done many older and newer, but I've never rebuilt a 3.6.
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SirAndy
post Jun 14 2019, 12:15 PM
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QUOTE(Mark Henry @ Jun 14 2019, 04:25 AM) *
This question I'd ask over on the bird engine rebuild forum.

We'll see how that goes ...
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mepstein
post Jun 14 2019, 12:44 PM
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The wrong sender will double the pressure reading. Without seeing what you have, our engine guy that’s the problem. Hook up a manual gauge and you will know for sure.
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Spoke
post Jun 14 2019, 01:36 PM
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Have you confirmed the pressure with another gauge? My 3.3L 930 peaks at about 4BAR cold and 3-3.5Bar warm. I guess it better to have too much pressure instead of not enough.
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SirAndy
post Jun 14 2019, 02:20 PM
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QUOTE(mepstein @ Jun 14 2019, 11:44 AM) *

The wrong sender will double the pressure reading. Without seeing what you have, our engine guy that’s the problem. Hook up a manual gauge and you will know for sure.
@SirAndy


Checked my records and this is what i bought:
https://patrickmotorsports.com/products/eng-36-oil-ps2-pms

It's a 0-10 bar dual sender with an adapter to fit in place of the stock 0-5 bar sender.

Went to look at the car (at work right now so i can't really take it apart) and snapped a quick pic, you can clearly see the adapter between the case and the sender.

So i'm going to assume i have the correct 0-10 bar sending unit ...
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mepstein
post Jun 14 2019, 02:52 PM
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Grease gun threaded hose and manual gauge will tell you for sure.
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post Jun 14 2019, 03:54 PM
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(IMG:style_emoticons/default/agree.gif) Sounds like you've covered the bases Andy but a temporary hook up to a mechanical gauge that can be purchased for < $25 will put your mind at ease, Señior. (IMG:style_emoticons/default/beerchug.gif)
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SirAndy
post Jun 14 2019, 04:02 PM
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So assuming that a mechanical gauge agrees with my current gauges, i still would like to know what the maximum pressure is one can safely put into this engine.

Is > 100 psi too much?
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DaveO90s4
post Jun 14 2019, 04:31 PM
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Andy, another 928 comment (not 993) that may be relevant. On the 928 the maximum gauge reading is 5 bar but the pump will pump up to 8 bar. Anything from 5 to 8 bar simply has the needle pegged at 5 bar. Maybe the 993 adopts the same Porsche thinking? Just a thought
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SirAndy
post Jun 14 2019, 04:34 PM
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QUOTE(DaveO90s4 @ Jun 14 2019, 03:31 PM) *
Andy, another 928 comment (not 993) that may be relevant. On the 928 the maximum gauge reading is 5 bar but the pump will pump up to 8 bar. Anything from 5 to 8 bar simply has the needle pegged at 5 bar. Maybe the 993 adopts the same Porsche thinking? Just a thought

That's what i am hoping for but i can't find any definitive answers anywhere about what the max actually is.

8 bar is ~ 116 psi and my engine gets that high when i drive it hard.

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worn
post Jun 14 2019, 04:43 PM
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QUOTE(SirAndy @ Jun 13 2019, 06:14 PM) *

What is the max oil pressure i should be comfortable with (under load) on my 3.6L?

I've been reading 993 manuals and posts all over the tinterwebs and all i can say for certain is that the stock 993 gauge seems to max out at 5 bar but according to all the info i found you'll get there already around 3k rpm and then the gauge just sits at max.

The reason i'm asking is that i'm using a gauge showing psi instead of bar (with the correct sender for that) and 5 bar should be around 73 psi but my oil pressure is substantially above that under load.

I'll idle around 40 psi (sometimes drops to 25-30 when it's really hot) and hit 100 psi as soon as i get above 3k rpm and pretty much stays there.
I've seen as much as 110 psi.

100 psi is about 6.9 bar
110 psi is about 7.6 bar


Question is, am i about to blow up my engine running these kinds of pressures?
(IMG:style_emoticons/default/confused24.gif)

I understand the concern, and have had it with my TR6, but also think you are lucky to be on higher end of the problem. I would think that oil coolers would be most at risk. The bearings and engine internals would just go happily spitting oil, high pressure or not.
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roblav1
post Jun 14 2019, 05:30 PM
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Those pressures seem high to me. Hot, 40 to 50 psi at 3000 rpm is about the norm in all my 911 engines. Start at about 20 psi and add 10 psi per 1000 rpm. Load should not have an effect on psi. Temp and rpm will.
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Mark Henry
post Jun 14 2019, 07:22 PM
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Has it always done this or is this new?
For a mechanical gauge, if you can get a long enough whip, I'd tape it to the rear window so you can read it in your RVM as you drive.
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porschetub
post Jun 14 2019, 10:14 PM
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Hopefully useful only cause I looked and researched one of these motors but the deal never panned out due to zero history supplied from the seller of a JDM import "write off" with 993 engine.
2 bar oil pressure @ hot idle,pressure pegs out to 5 bar (74psi) at around 3000 rpm and the hp relief valve is set to 6.2 bar (92 psi).
Wisdom certainly indicates a mechanical gauge test as mentioned ,if the same check the oil pressure relief ,not worth pissing around as an expensive engine.
Oh and yes excess oil pressure can cause issues....have seen it.
Good luck Andy.
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SirAndy
post Jun 14 2019, 10:43 PM
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QUOTE(Mark Henry @ Jun 14 2019, 06:22 PM) *
Has it always done this or is this new?

It's always been high but used to be at around 80-90 psi max.

Getting over 100 is new.
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jcd914
post Jun 14 2019, 10:56 PM
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When did it start?
Didn't you have an oil pressure problem a while back?
Something about a sudden loss of pressure?
Or am I mis-remembering?

Jim
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