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High oil pressure question


pd_55

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This is for the M10 builders and gurus. i.e. @kbmb02 The motor that I’m running is a 2.0 liter that has reportedly been built in the 90’s. Not sure of the compression, but pistons are Arias and is running an unknown spec Schrick cam. Has also been converted to fuel injection with Haltech ECU management. Had an engine out service by VSR in NH in 2020 where it was resealed, oil pump replaced and pan baffled. Motor runs well, no smoking, no leaking, no seaping around gaskets.

 

BUT, it is running very high (to me) oil pressures.

 

Cold start - Idles at 60-70 psi

Driving (cool) - Above 3k, 70-80 psi

Warm idle - 40-45 psi

Driving (fully warm) - Above 3k, 50-60 psi

 

Oil is LiquiMoly 20w50 Classic. Car lives in Phoenix, AZ, so oil is never that cold. My only comparisons are my other cars that operate in the 25-40 psi range, so 70 psi seems ludicrous. Question is if this can be considered acceptable or normal for a tuned M10 or are these unsafely high pressures?

 

Thought it might be the sensor, but I installed a mechanical gauge backup and reads the same. Could it be the fitting where both sensors are tapped into; orifice size? Blocked passage? Blocked oil pump pickup? Oil pan baffle? Baffle pic attached. Any help is always appreciated.

 

IMG_1606.png

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That is about normal for a healthy M10.  The pressure relief valve does not have a really large passageway so with cold oil you can easily get to 100psi when it's cold if you rev the engine above 3000 rpm.  The factory spec is 4bar (57psi)@ 4000 rpm with warm oil. 

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1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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Normal!

Oil pressure relief valve in pump (should) limit max pressure to about 74 psi...which you would see on a cold start and drive.

Fully warmed and driving pressure is perfect at the 60 ish range.

Warm idle is great.

Do you have a mechanical or electric oil pressure gauge?  Mechanical with 0-100 range is accurate and easy to read with a 270-degree needle sweep.

 

IMG_4684.thumb.JPG.9da58bad6929f042f11b7ec4f8a857af.JPG

 

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I haven’t heard of pressures that high, but that’s reassuring to hear. Just recently started driving it after installing the motor, trans and new engine management. So I was definitely concerned.

 

@John76 The mechanical gauge I’m running is an AutoMeter classic style 0-80 psi. It runs in line with the ecu reading, which is why I installed it. The sensor is a Haltech sensor that reads to the digital dash. I have the warning at 80 and it flirts with that sometimes when cold.

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Looks pretty normal for a healthy engine to me...

 

if it goes over 100, the relief plunger's probably sticking-

just don't LET it go much over 100 when it's cold,

or it can blow the oil filter off.

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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@TobyB I don’t think that will happen as when I see 80, I almost want to coast to the shoulder, shut her off and pray I don’t see a fireworks of oil under the hood. Thanks for all of the insights.

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With a 80psi mechanical gauge you need to keep your OP under 80 if you top out the gauge it will stretch the internals and become inaccurate.

If everybody in the room is thinking the same thing, then someone is not thinking.

 

George S Patton 

Planning the Normandy Break out 1944

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The early gear type oil pumps had a problem with sticking pressure relief valves.  On a cold winter morning if it stuck you could easily hit 200+psi.  I separated a MANN filter at the seam once, It sounded like a water spray nozzle in the engine bay.  Made one hell of a mess.  

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1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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5 hours ago, pd_55 said:

I think I opted for the 80 psi, because I didn’t think it would run that high. Always learning.

I pegged the 150 psi VDO electric gauge on my '69 once--on a (too) cold morning (to be) running 20w-50 oil.  Even warmed up it was showing 70-80 psi.  Also, I've found that equal weight synthetic oil runs a bit lower pressure than conventional oil.  

 

mike

'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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6 hours ago, Son of Marty said:

Yeah, but not for long.

It happened so quick I only had to push it about 30 yards to get it back in my driveway. Fortunately it was gravel. 

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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10 minutes ago, Preyupy said:

It happened so quick I only had to push it about 30 yards to get it back in my driveway. Fortunately it was gravel. 

I messed up a paddock pretty bad in a cold race morning. Glad I didn't get on track.

Also many many years ago I assembled the relief tube wrong way so it prevented the piston movement. It took about 10 seconds from first start to blow the filter seal out.

Racing is Life - everything before and after is just waiting!

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Pressures look comparable to my rebuilt 74 with 4 miles so far. On cold start choke high idle 1500 rpm I see 80-85 psi on the VDo gauge. Otherwise almost identical to yours. Nice, run her!

 

"Sometimes it's a little better to travel than to arrive”  Robert M. Pirsig

Gunther March 19, 1974. Hoffman Motors march 22 1974 NYC

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18 hours ago, pd_55 said:

@TobyB I don’t think that will happen as when I see 80, I almost want to coast to the shoulder, shut her off and pray I don’t see a fireworks of oil under the hood. Thanks for all of the insights.

No need for religion- just shift. 

Keep the revs lower.

Once warm, the regulator unsticks, the oil thins, and you're fine.

 

t

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"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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