100+ oil psi on my rebuilt m20

[Kozworth]

Rebuilt b25 with new bearings, rod bolts, arp, oringed block, rings, gaskets. The engine was 100% working and was a daily before the build with no oil pressure lights or issues of that nature. Everything plastigauged within spec.

I have a sunpro oil pressure gauge, and at first I was getting around 20psi with just a few quick cranks. I believe the oil pressure built up. I am getting now 100+ since the gauge stops at 100. I am afraid of blowing seals.

I do have a reducer on my turbo feed, it came with the feed line kit. it basically takes the 4an and makes it a pinhole. Since the kit was not adaptable to just a straight 4an to the turbo, I decided to try it out.

Any issues with "boring" out this reducer with a drill bit to make more passageway to lower the oil pressure. I am pretty sure its this and not an oil block somewhere in the engine.

[Nutzy]

Don't try and drop your oil pressure by increasing feed to the turbo, you'll just kill hte turbo.

Something is wrong there, possibly the oil pressure control bizzo valve.

I helped a friend years ago with a motor swap in a Datsun. The first time he cranked it over, the oil filter basically exploded and pissed oil everywhere. It turned out the oil pressure relief thing was assembled wrong.

[Nutzy]

Don't try and drop your oil pressure by increasing feed to the turbo, you'll just kill hte turbo.

Something is wrong there, possibly the oil pressure control bizzo valve.

I helped a friend years ago with a motor swap in a Datsun. The first time he cranked it over, the oil filter basically exploded and pissed oil everywhere. It turned out the oil pressure relief thing was assembled wrong.

[Kozworth]

Edit: I stated reducer, I ment restrictor
Well I do not see an issue with increasing the feed size to the turbo. First of all, its a restrictor at the turbo inlet, but the turbo is normally a -4an. Maybe I am just thinking of this backwards.. But I assume with a smaller hole youd gain more pressure. For example, a hose shoots out at x flow, but when you shrink the hole it travels thru by placing your thumb covering part of the end, this hole is smaller and y ammount flows.

Also, not really too fimilar with oil flow and pumps, but I did change an oil pump on an e30 on my back with the pan half in the way, I am pretty sure I assembled the pump and its components correctly with the engine on a stand.

Like I stated, its basically all from a running engine. The block internals, and whole head did not have any visible oil pressure issues or clogs. The block was oringed from an eta. Every passage was cleaned thoroughly and the block was hot tanked/honed aswell.

[bmwstudent]

You are correct in assuming that a restriction creates pressure. But it will create pressure on the restricted side of the fitting, once it makes it through the fitting to a larger cavity(inside of turbo)there will be a pressure drop. Especially since it's a gravity drain into the oil pan. I'm not sure but do you have the restrictor in the wrong spot? I work on tractor trailers and they are all turbo charged, I've never seen a restrictor on the turbo feed line, nor the drain.

[lcoleman]

Don't try and drop your oil pressure by increasing feed to the turbo, you'll just kill hte turbo.

Something is wrong there, possibly the oil pressure control bizzo valve.

+1

I would make sure your gauge isn't just grounding out, too.

[Kozworth]

You are correct in assuming that a restriction creates pressure. But it will create pressure on the restricted side of the fitting, once it makes it through the fitting to a larger cavity(inside of turbo)there will be a pressure drop. Especially since it's a gravity drain into the oil pan. I'm not sure but do you have the restrictor in the wrong spot? I work on tractor trailers and they are all turbo charged, I've never seen a restrictor on the turbo feed line, nor the drain.

Well, I feel that if you had a restriction, it would atleast affect the line somewhat, not just at the tip. The way my sender is set up is there is a 4 way adapter. One is a male/male fitting into the oe oil pressure spot, one is blocked, one goes to the feed line, and one goes to the oil press sender. I feel that if the line was held up from a restrictor thats too small for the turbo, then there would atleast be greater backpressure. I read that one guy has 70-80 psi on an oe b25, so assuming a -4an line has now a pinhole passage I feel that the feed line itself would have a lot more back pressure.

From what I read, the H1C is not a ball bearing turbo, its a journal style. IIRC, a ball bearing turbo requires a restrictor to reduce flow to the turbo, to not blow past seals. This is where I am confused, because a restrictor in the sense of a garden hose would actually increase pressure?

Its late night, keep dem hoes til its daylight. I cant think straight.

[NZM3]

Hi,
I would suspect the oil pressure relief valve is stuck (maybe the spring is too stiff) or not operating correctly that is assuming the gauge is working correctly.
Changing the oil feed line size etc to the turbo will not be the route cause of the problem.
Are you running the correct oil viscosity if it was to thick it can cause higher oil pressure.

[Kozworth]

I remember upon assembly that the relief valve did move distinctly.

I have a video of a start up of one of the first times, where it read 24 lbs.. Is it possible that the car was not fully primed?

And again... I would NOT be changing the turbo feed line size. The turbo itself takes -4an... so Boring out the hole would just make the line size closer to stock! I am not sure if I am describing this correctly or not, but does my reference to the garden hose make sense...?

[Rc 415]

Opening up the restrictor will not reduce engine oil psi. Where are you sourcing your turbo oil feed line from? The stock oil pressure sensor location? Just think of it like this, the pressure sensor that was there might as well have been a plug there.

[Kozworth]

Opening up the restrictor will not reduce engine oil psi. Where are you sourcing your turbo oil feed line from? The stock oil pressure sensor location? Just think of it like this, the pressure sensor that was there might as well have been a plug there.

The source is from the stock oem oil pressure sender spot. Ive seen this dozens of times done on e30 turbos. Jordans massive turbo writeup utilizes this spot. Not sure what you mean might as well have been a plug here.

If you take a garden hose and block it off (with a plyable enough hose I assume) the hose would build pressure, and start to bow out. Now.. If you take a garden hose and not block it off completely, but put your thumb over 80% of it, how would that not increase pressure? You see the water shoot out much further.. If the orfice is smaller, you will get a further spray, but LESS water is traveling through the orfice, so in return MORE water would still be in the hose.

So how is this not relevant to my turbo feed? If the oil is being pushed through a 4an line, then jammed through a pinhole, I could see how the gauge pre feedline would read a higher pressure because the oil is being restricted through the restrictor, and there is technically more oil pressure since the oil cannot pass through the restrictor as easily due to the opening. Less oil flowing with the same constant of oil pressure from the engine thus changes to more pressure, since the engine oil is not moving at the same rate as stock....

[ak-]

I'm tired and can't read everything, but where is your oil pressure sender located for your gauge?

[Rc 415]

I run the same setup my oil pressure guage sensor was right off the T there. Ran no restrictor and a .40 restrictor and saw no change in oil pressure. If anything adding the turbo feed to your pressurized oil feed system should drop your engines overall pressure because the sensor that was originally in the turbo feed spot did not relieve any pressure at all. Your oil pressure bleed in the pan is most likely to blame

[FLG]

Your not thinking correctly. A restrictor reduces pressure, not the opposite. Think about if you have a sealed bucket with a hose attached to it and a small hole on the bottom, now assume there's no restriction and the hose can fill the bucket quicker then the hole can drain it... Thus causing a pressure build up. Now put a restrictor on that hose, yes there may be more pressure at the tip but now that same hose cannot fill the bucket up as fast due to the restricted flow, thus causing less pressure build up.

Sent from my Galaxy Nexus using Tapatalk 2

[Rc 415]

I've tried to explain best I can, I run the exact setup daily and have no issues. Good luck with figuring it out