ayousef

title say it all, whats the safe maximum oil pressure our engines can handle at high RPM, in this case a built RHS 427.

I don't want anyone telling me the 10psi per 1000rpm ballpark figure I want to know whats the safest anyone would feel running on their lsx based on factual data.

Thanks

redtan

iTrader: (5)

How would anyone have "factual data" for something they "feel".

I feel the safest at 70psi @ 7000rpm, but unfortunately I have no way of giving that to you in factual data...

Tainted

iTrader: (9)

Well theres gonna be factors you need to mention to give you that perfect answer.

Oil weight
Bearing clearances
Materials (iron or aluminum different expansion rates etc) that need to be factored in
Im sure oil temp plays a factor as well at some point
How good the oiling system is. You do see some people talk of the crank "frothing" up the oil so you lose efficiency.

I quite possibly left out plenty more but those are some big ones

ayousef

not sure why that was very hard to interpret? I said what you personally feel BASED on factural data, for example you could say I feel 70psi is the max I would like to see at 7000rpms because ive seen issues where going above 70psi caused bla bla bla etc... Its very simple.

I also posted this question in the wrong section, I was half asleep when I did.

ayousef

The reason im asking is simple, I have a Meling 10295 high pressure pump on my wet-sump RHS427 which takes 8.5 quarts of oil (go figure) and have a small thermostatic oil cooler adapter. When oil temps are cold and warm and just slightly below 105 degrees CELICUS I have perfect oil pressure, which goes up to 75psi at 6500rpms with 20w-50 oil, which could obviously be slightly less with thinner oil. Now the problem I have is, as soon as temps go above 105, oil pressure at wot goes down to 35ish psi which im not very happy with on an $18,000 LME longblock (minus intake).

I did so many changes at once im not sure where the pressure will end up at, threw the thermostatic adapter out, put a normal adapter, routed the oil cooler lines with -10 instead of -8 and purchased a high volume/high pressure melling pump and shimmed the spring just a tiny bit.

The additional volume should increase pressure, cooler oil due to no thermostat should increase pressure, and bigger oil cooler feed and return lines should also reduce pressure drop hence increase pressure, but the fact that the oil will always be circulating in the cooler will cause a pressure drop yes im loosing my mind.

Tainted

iTrader: (9)

You better watch that the high volume pump doesnt suck your pan dry. I think you would have been better with a high pressure pump with a shimmed spring . And more volume doesnt necessarily mean more pressure either.

06Sierra2

I'm pretty sure that pump is stock volume, high pressure. Should be about 10psi over stock? Should be the same pump I'm running on the dd and just ordered for my stroker project car

ayousef

well to be honest with you im not really worried about that problem, im sure whatever oil going to the top will find its way back down pretty quick, especially since my setup required I not use lifter trays. Like I said I also run 8.5 quarts of oil in my set-up and finally with all this power I barely stay on the throttle for a few seconds at a time

I had the high pressure melling pump and im now switching to the high pressure high volume pump. The reason I did not shim the high pressure pump and opted to go with the high volume one then shim is because based on my conversation with Melling tech they told me that the red spring (high pressure spring) cracks open at 60+ psi and is fully open at something like 90psi, shimming the pressure relief valve when im only getting 30psi at WOT wont do a thing for oil pressure since the relief is fully shut (my tuner thinks it will) so I would like to hear what you guys have to say on the subject.

Also, all else equal higher volume will create more pressure no way around it, lets assume a 1" pipe and your flowing 20gpm through it, then all of a sudden you flow 25gpm through the same diameter pipe, pressure will inevitably go up.

Keep the comments/suggestions coming though please

Tainted

iTrader: (9)

Someone Im thinking matt at texas speed made a post a long while back about these pumps andnpressure concerns and volume vs pressure. Maybe try a search on the subject if you havent already?

Exidous

iTrader: (11)

I would contact LME. Your oil weight and pressure should be based on how they specced the motor. Bearing tolerance and such. Your pressure shouldn't drop that much though just because you went over 105C.

ChucksZ06

iTrader: (9)

You have main bearing clearance problems sir. Better fix that or use some thick oil or you will have big problems. 35 psi is not good at high rpms.

ayousef

I don't have bearing problems at all, I have 75psi at 95degrees celcius engine oil temps, however as temps goto 105 it drops to about 35ish at WOT. During this time the thermostatic oil cooler adapter starts to open causing the pressure drop in addition to the slight drop due to rising temps, there is no way oil pressure will drop that much in 10 degrees if I had bearing problems.

On the otherhand LME did recommend the 10296 high volume pump but for some reason the builder put in the 10295 cause he probably never read the sheet from LME.

CAMSTER

iTrader: (10)

I always shim relieve valve .075 with the melling high pressure high volume
pump, I usually see 73 psi @ wide open throttle at running temps.
I use 10/30 0r max 10/40 weight oil in new high compression or boosted engines.
I always like to add a quart Dura Lube for extra protection and piece of mind.

Gordon0652

iTrader: (4)

Blah Blah Blah pressure, you want Volume!

CAMSTER

iTrader: (10)

I speak for myself, I want both the worst thing is to have a expensive new engine seating at a traffic light in hot weather and 16 psi oil pressure.

ayousef

well since the engine clearances aren't going to change, and assuming oil viscosity is constant, increasing pressure is the only way you will increase flow. Plus you need pressure to get oil to the bearings when the engine is spinning at a very high speed and the associated centrifugal forces acting against that pressure

Awake455

If I read correctly you lose 40 psi when the oil temp goes from 95 C to 105 C, is that correct? If so, I'd suspect the thermostat or oil cooler setup.

Out of curiosity, did you try hooking the oil cooler up without the thermostat assembly to see if the restriction was in the cooler/lines or the thermostat?

soundengineer

iTrader: (16)

the Simple answer is...as long as you dont collapse/blow up the oil filter, and as long as you dont cavitate the oil, or suck the pan dry.... you can never have too much

the low side all depends on the use....
of course you already know the 10psi per 1000 rpm rule...
but some engines dont even need that much...
I know some diesels spec out at 2psi minimum at idle.....because that is all it takes to float the crank and prevent bearing damage because of how well they are built and how much tighter their machining tolerances have to be to support the power they make.

on my setup... at idle I have 75-80 psi cold, and 60-65 psi hot.
at WOT, I have 130-135 psi Hot (I dont know about cold because I dont go WOT until all Fluids are warmed up

I know some promod guys, and they all have 70-90 at idle and 130-150+psi at WOT(some have more than that)


again.. they key is that you dont suck the pan dry, and you dont cavitate the oil or froth it up...

other than the oil filter, there is nothing you can hurt from high oil pressure
so just be sure to use a Wix or K&N filter that have been tested to over 300 psi with no issues.

if you have turbos or an oil fed supercharger, you may need to restrict the feed line to keep too much oil from going into it and overflowing it.

get a high flowing oil pump like the Schumanns Race pumps, and you will see a rise in pressure because of the rise in flow(you can only flow so much fluid thru the passageways, so pressure goes up because flow cannot increase without a pressure increase if the oil passage stays the same size)

Insttech427c5

did you ever figure out your oil pressure issue?

pdxmotorhead

8 year old thread...