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914World.com _ 914World Garage _ Oil pressure on a /6 under load
Posted by: SirAndy Jun 13 2019, 08:14 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?
Posted by: Cairo94507 Jun 13 2019, 08:50 PM
Andy- That seems like high pressure to me. Are you certain the sender and the gauge are matched units? 
Posted by: SirAndy Jun 13 2019, 09:19 PM
Andy- That seems like high pressure to me. Are you certain the sender and the gauge are matched units?
Yes, most certainly certain ...
Posted by: rick 918-S Jun 14 2019, 03:00 AM
My 928 engine starts up at 150 psi. Not the same engine. Hot it runs at around 80 psi.
Posted by: Mark Henry Jun 14 2019, 05:25 AM
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.
Posted by: SirAndy Jun 14 2019, 12:15 PM
We'll see how that goes ...
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Posted by: mepstein Jun 14 2019, 12:44 PM
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.
@http://www.914world.com/bbs2/index.php?showuser=179
Posted by: Spoke Jun 14 2019, 01:36 PM
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.
Posted by: SirAndy Jun 14 2019, 02:20 PM
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.
@http://www.914world.com/bbs2/index.php?showuser=179
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 ...
@http://www.914world.com/bbs2/index.php?showuser=10825
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Posted by: mepstein Jun 14 2019, 02:52 PM
Grease gun threaded hose and manual gauge will tell you for sure.
Posted by: 76-914 Jun 14 2019, 03:54 PM
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.
Posted by: SirAndy Jun 14 2019, 04:02 PM
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?
Posted by: DaveO90s4 Jun 14 2019, 04:31 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
Posted by: SirAndy Jun 14 2019, 04:34 PM
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.
Posted by: worn Jun 14 2019, 04:43 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?
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.
Posted by: roblav1 Jun 14 2019, 05:30 PM
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.
Posted by: Mark Henry Jun 14 2019, 07:22 PM
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.
Posted by: porschetub Jun 14 2019, 10:14 PM
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.
Posted by: SirAndy Jun 14 2019, 10:43 PM
It's always been high but used to be at around 80-90 psi max.
Getting over 100 is new.
Posted by: jcd914 Jun 14 2019, 10:56 PM
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
Posted by: SirAndy Jun 15 2019, 12:33 AM
Didn't you have an oil pressure problem a while back?
Something about a sudden loss of pressure?
Or am I mis-remembering?
Yes, this is the inverse of my previous problem ...
PS: I noticed it during the WCR trip
Posted by: Spoke Jun 15 2019, 01:11 AM
What viscosity oil are you running? I run 20W-50 in my 3.3L.
Posted by: Mark Henry Jun 15 2019, 04:57 AM
IIRC there is a oil pressure relief somewhere on the 3.6, I'd check it's operation.
Do the mechanical gauge temporary taped to the rear window so you can see it in the RVM trick, I've done it a few times for fuel pressure issues, works well.
Posted by: SirAndy Jun 15 2019, 10:04 AM
What viscosity oil are you running? I run 20W-50 in my 3.3L.
Mobile1 0-40 per Porsche recommendations, i've been running that same type of oil for 15 years now.
Posted by: SirAndy Jun 15 2019, 10:05 AM
IIRC there is a oil pressure relief somewhere on the 3.6, I'd check it's operation.
Do the mechanical gauge temporary taped to the rear window so you can see it in the RVM trick, I've done it a few times for fuel pressure issues, works well.
I know of the pressure relief valve, which is a contender.
Stupid question, could a clogged up oil filter cause this?
Posted by: Dave_Darling Jun 15 2019, 10:17 AM
The 993 used two oil filters. One of them may have been where the cooler was on earlier engines? I forget.... I do know it was harder to access than the standard one, though. Does your car have the on-engine cooler, or just the remote one?
--DD
Posted by: SirAndy Jun 15 2019, 10:21 AM
The 993 used two oil filters. One of them may have been where the cooler was on earlier engines? I forget.... I do know it was harder to access than the standard one, though. Does your car have the on-engine cooler, or just the remote one?
I have two and yes, one is in the location where the on-the-engine oil cooler would be on other /6 engines and the second one is in the stock location on the tank.
Posted by: Tdskip Jun 16 2019, 07:15 AM
Sounds like something may be constricting oil flow - agree with others that it sounds high.
Maybe change oil/filters and see if it comes back down some.
Given cost of these engines getting a sanity check mechanical gauge on it seems like a good idea.
Posted by: McMark Jun 16 2019, 08:21 AM
The pressure range of the sender will be stamped here. There are a few numbers on each face. The one in the picture says 30/16 (?) which should be the 30th week of 2016. You'll probably need an inspection mirror, or a borescope to see in there accurately, but you may get lucky with a phone picture or video.
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Posted by: porschetub Jun 16 2019, 02:52 PM
IIRC there is a oil pressure relief somewhere on the 3.6, I'd check it's operation.
Do the mechanical gauge temporary taped to the rear window so you can see it in the RVM trick, I've done it a few times for fuel pressure issues, works well.
I know of the pressure relief valve, which is a contender.
Stupid question, could a clogged up oil filter cause this?
Not a stupid question really,I don't think so because you should have over pressure valves in your filter housings,or atleast I know there's one in the tank filter housing on my car...spring and ball on a round seat.
Even if your system is different the filters themselves should have in built reliefs but I don't know @ what pressure they bypass.
Posted by: Mark Henry Jun 16 2019, 03:25 PM
IIRC there is a oil pressure relief somewhere on the 3.6, I'd check it's operation.
Do the mechanical gauge temporary taped to the rear window so you can see it in the RVM trick, I've done it a few times for fuel pressure issues, works well.
I know of the pressure relief valve, which is a contender.
Stupid question, could a clogged up oil filter cause this?
Not a stupid question really,I don't think so because you should have over pressure valves in your filter housings,or atleast I know there's one in the tank filter housing on my car...spring and ball on a round seat.
Even if your system is different the filters themselves should have in built reliefs but I don't know @ what pressure they bypass.
They don't really bypass at high pressure, they bypass at a differential in pressure of the in/out sides. It's not a big number maybe 10 psi difference. What controls the pressure in the circuit is the engines pressure relief valve(s).
If it's not the sensor I'd do a full oil change, cut open the filters, check the sump and check the operation of the pressure relief valve...
I'd still hook up or T in a mechanical pressure gauge first.
Posted by: porschetub Jun 18 2019, 12:08 AM
IIRC there is a oil pressure relief somewhere on the 3.6, I'd check it's operation.
Do the mechanical gauge temporary taped to the rear window so you can see it in the RVM trick, I've done it a few times for fuel pressure issues, works well.
I know of the pressure relief valve, which is a contender.
Stupid question, could a clogged up oil filter cause this?
Not a stupid question really,I don't think so because you should have over pressure valves in your filter housings,or atleast I know there's one in the tank filter housing on my car...spring and ball on a round seat.
Even if your system is different the filters themselves should have in built reliefs but I don't know @ what pressure they bypass.
They don't really bypass at high pressure, they bypass at a differential in pressure of the in/out sides. It's not a big number maybe 10 psi difference. What controls the pressure in the circuit is the engines pressure relief valve(s).
If it's not the sensor I'd do a full oil change, cut open the filters, check the sump and check the operation of the pressure relief valve...
I'd still hook up or T in a mechanical pressure gauge first.
Yes ,but my point was unless there is a restriction on the return system it's otherwise well taken care of.
I still vote for oil pressure valve check after doing a mechanical gauge test.
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