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Post by Tony O. on Sept 1, 2010 20:27:12 GMT -5
Hi everyone.
Finally fired up the new motor I built.
New Brazilian case. I drilled and tapped it for full flow oil.
Shadek 26mm plugged pump.
New oil cooler.
Empi high pressure relief and oil control valves and springs.
New stock cross drilled crankshaft.
All oil clearances around .0025.
Using 10w-30 Valvoline full synthetic racing oil. On cold (90 F) today start up pressure gauge pegged 70 psi. Once warmed up, 150 on oil temp gauge, had 40 psi at idle. Back up to 70 Psi @ 2000 rpm.
Just wondering if this too high?
Any thoughts?
Tony O.
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Post by Gary Hammond on Sept 1, 2010 21:01:36 GMT -5
Hi Tony,  Oil pressure that high is usually used with greater oil clearances (ie. .003" to .004"), heavier weight oil (ie. 20w-50 racing), and high sustained RPMs ( 6000 to 9000 rpm) racing engines.  This sounds too high to me for a reasonably stock street engine with only .0025" bearing clearance.  I would think the stock 45 psi at 2500 rpm and 158 deg temp up to maybe 55 psi would be better. I'm surprised that with 70 psi feeding a .0025" clearance you aren't getting oil temps in the 225 to 250 deg range! Are you sure all your gauges are accurate?  Gary Hammond,   |
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Post by Tony O. on Sept 1, 2010 21:22:58 GMT -5
Hi Gary,
As far as I know the gauges are good. The oil temp gauge and sender are a new matched set VDO. The oil pressure gauge and sender are original and were reading 45 at start up and @ 15 at warm idle on a sloppy engine.
Maybe I need to go back to the stock springs?
I don't know. I always thought reasonably high pressure was a good thing but are these pressures beyond the high end of good?
Tony O.
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Post by Gary Hammond on Sept 1, 2010 22:35:12 GMT -5
Hi Tony, It depends on how your engine is set up. Are you running a stock oil cooler? Pressure this high can damage a stock oil cooler and may eventually blow the seals where it mates to the block. The higher the rpm, the greater the bearing clearance, and the higher the bearing load, -- the higher the oil pressure must be to keep the space between the crankshaft and bearing filled with oil. The oil is trapped between the rotating parts and provides hydra-dynamic lubrication due to the rotating action wedging the oil. The oil also removes heat from the metal parts which is later removed from the oil by the oil cooler. In addition, the oil is heated by being forced through a restriction under pressure. The higher the viscosity and the higher the oil pressure, the more heat is produced by being forced through a restriction. So if way more oil than is needed for proper hydra-dynamic lubrication is forced through the clearance from extreme pressure, extra heat is generated and power is wasted.  This will lead to extra pump wear and extra stress on the entire oil system including the oil cooler. For a mild, reasonably stock engine running 2500 to 4500 rpm I wouldn't go much over 45 PSI at operating temperature. Pressure at idle shouldn't drop below 15 to 20 psi. For a high performance engine capable of 6000+ rpm and 120+ hp, I would shoot for 55 to 60 psi and still maintain 15 to 20 psi at idle. Gary Hammond, P.S. --- You can buy adjustable spring anchor plugs that will let you set the oil pressure wherever you want it. |
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Post by Gary Hammond on Sept 1, 2010 22:49:27 GMT -5
Check out the dyno charts on CB Performance's turn key engines for oil pressure, oil temp, cylinder head temp, and oil type. Keep clicking on the "next" button. They have several engines listed here. cbperformance.com/dyno/dynocharts.htmlGary Hammond, |
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Post by jspbtown on Sept 2, 2010 8:27:53 GMT -5
I would definitely try the stock springs.
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Post by Gary Hammond on Sept 2, 2010 11:55:37 GMT -5
Hi Tony, Most of what I posted to this point was my understanding of a conventional U.S. engine. That's where most of my experience is. The ACVW dual relief system with built-in oil cooler is a different setup and operates a little differently. I found a post on The Samba website that shows how it operates. www.thesamba.com/vw/forum/viewtopic.php?t=280293&highlight=oil+pressureI have modified mine to a dry sump system with only one pressure relief valve, an external oil cooler, and external oil filter. So again, my experience is not with the stock VW system. From the Samba posting, it looks like your new case may have an undersized relief port from the oil control valve. Gary Hammond, |
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Post by Tony O. on Sept 2, 2010 12:52:18 GMT -5
Hello Gary,
Thank you for the link. Have not had time to digest all the info yet.
Tony O.
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I would think the stock 45 psi at 2500 rpm and 158 deg temp up to maybe 55 psi would be better.
This will lead to extra pump wear and extra stress on the entire oil system including the oil cooler.