Oil pressure, how much is too much?

[DaSuprawolf]

i just finished rebuilding my N/A and i did the oil pump shim and during break-in the oil psi was around where it used to be. but after i changed to full synthetic oil and a K&N filter, its much higher, on the high way im pushing 80 psi! it was never that high befor. i like the higher psi but how much is too much??

btw, the shim was a 10mm nut, only like 4.5mm if i remember.
thanks all, -Brian

 

[Bishop92t]

Pressure is not flow. That K&N oil filter has a nasty habit of increasing pressure by restricting flow. Other then that, the only immediate problem with increased pressure is the increased chance of blowing a seal and/or leaking oil. I would recommend removing that K&N filter in favor of a stock unit.

 

[malloynx]

over time you WILL erode the bearings. hot oil with high pressure is like a bead blaster on your bearings

 

[xarewhyayen]

over time you WILL erode the bearings. hot oil with high pressure is like a bead blaster on your bearings

I agree... our system was designed to be high volume low pressure (HVLP). Its the flow ( volume) that matters. The only real oil system upgrade i would personally consider would be dry sump. Our system works very well if you maintain it correctly.

 

[Adjuster]

Just a few things to consider.

The filter is between the pump and the main galley pressure sensor on the stock engine, so if the filter is limiting flow, it would not show up as a pressure increase, but a pressure decrease....

Part of the higher pressure is the close tolerance of the bearings. I'm guessing on that shimmed pump he's on new bearings, and they have good close tolerances if he's seeing that much pressure at the galley.

I agree that oil under pressure will erode bearings over time. (Especially if there is debris in the oil.) The reality is however, your talking about pressures higher than 80psi. If he's seeing 80psi hot pressures, his engine is the tightest 7MGTE I've seen yet. (Mine does that cold, but then drops off to the 40's. in normal running with the 15/50 oil I run.)

Just make sure you always run at least 6 quarts of oil (this is slightly over the "full" mark on your dipstick) and use good WIX or Purolator filters. (Never the Fram craptastick ones.)

Better yet, either go with a remote filter using the Canton/Mecca depth filters, or buy a spin on adapter and use the same filter in the "stock" location. They are more money, but you just paid lots of money for your motor, so it's cheap insurance. Besides, they trap crap down to about 8 microns v/s the 20+ or larger your paper type filters catch. And the wear is from particles larger than 10 microns according to conventional wisdom. (I've got an additional filter that stops stuff down to 1 micron in size, and the Canton full flow for everything else.)

They claim the depth filters flow better than paper, and even dirty they flow better than paper, so there is no need for a bypass setup. You oil is always filtered this way. If you use the stock spin on paper filter, as soon as it's trapped debris in the holes in the paper, the bypass opens, and your just pumping dirty oil through your motor....

 

[Yellow 13]

So any recomendations for a good overall filter?

 

[SupraDerk]

Yay, I just switched from Fram to a PureOne. One question though...6 quarts, is that good for all 7m's or just the highly modded ones? I'm runnin with a little over 5.

 

[Adjuster]

I belive that IJ tested a pan off the engine, and it took 8 or 9 quarts of oil in it before the oil would be at the level of the spinning crank and rods. (Where you start to get serious windage losses, and it could whip up the oil. Foaming oil is not good as it's a terrible lubricant in a motor.)

So, short answer is that 6 quarts is excellent, but I would not run more than 7 or 8 unless you have a remote filter setup, or medium sized cooler added into the system. (They all hold more oil in them.)

I have two remote filters, about 21' of AN10 line, 3 quart accusump, huge RX7 cooler that alone holds another quart of oil, so my "base" oil fill is 10 quarts, but it "tops" out at 12.

I have found that on my engine/setup no foam is present at 12, but it blows oil out of the dipstick tube and my PCV setup. (I'm working on improving that system now so there is less crank case pressure from blowby, also this was on a pretty new motor, so the rings likely are not sealing as well as they should be at this point. I lowered the oil level to 10 added, but there is some residual oil in the system, so a perfectly accurate count can't be made.)

I know there are some that claim oil is trapped up in the head under high RPM use and higher oil pressures, but I belive that's urban myth. The head does have some small oil drain back holes into the block, but there is a large tube that dumps oil back into the block next to your oil cap, and that alone is plenty of oil drainback capacity. (Also it appears they set this head up to hold some oil up there anyway, so I belive it's a non issue.)

My dipstick at full is when the oil is just at the point where the flat metal is attached to the wire. This is at 10 quarts of oil + whatever's left in the system prior to the oil change.

The green filter where the vapor canister used to be is a 1 micron or better bypass filter, the blue one on the right forward apron is the full flow Canton/Mecca filter good to 8 microns.

I have the RX7 cooler right in the airflow coming in my 88 upper grille area. There is no center support on my setup, so I had to custom build a brace to keep the upper tie bar from twisting, or the hood would not latch right.

 

[DaSuprawolf]

cool thanks for all the input.
and im not around 80 when hot, more over 40, 30 at idle. and running 10w-30.
and yes all new bearings and rings.

so with that /\ psi, am i ok?
just get a WIX filter or is the KN ok?
-Brian

 

[TurboStreetCar]

i have almost the oposite problem, rather then start a new thread i guess ill just ask quick here, i just finishing rebuilding my 89 turbo, i did the oil pump shim, the banjobolt line conversion to AN fittings and braided hose, and got a remote oil filter kit and at hot idle with 10-30 i run about 4-7 psi of pressure. no knocks or anything and as soon as it gets to like 1200 its at 20psi. but i never really see over 50psi at any rpm hot. cold i get about 50 at cold high idle, does everything sound good? should i run a 15-40 or something to bump the pressure up a couple psi?

 

[mkIIIman089]

Whats the banjobolt line conversion?

I get .6kg/cm^2/8.53psi at hot idle (105C) and somewhere around 3kg/cm^2/42.6psi hot at 3k RPM with a totally stock oil system.

http://cygnusx1.net/supra/library/TSRM/lu/LU_04.html

 

[TurboStreetCar]

theres a line that connects the oil pump to the block, its the main oil supply line. u use a BSP to AN fitting and a 18mm streight thread to AN fitting and AN line to replace the small line and banjo bolt setup. it was on a wright up on supraforums so i figure while i had my motor apart id do it.

umm...i have no idea what that kg/cm^2 stuff is. i kno its a pressure but about what is that in psi lol

 

[Adjuster]

Looks like this, but mine is AN10... (And to make it worth the time, you have to machine your pump, so it's really not an easy project, just use the 18mm BSP 90 angle as noted, AN8 line and fittings and your good to go.)

Remember to port your pump so the exit to the AN/BSP fitting has no sharp edges. The oil has to come out of the pump around a very sharp edge, and that can't be good for flow I'd think. Of course there are many, many very sharp edges where the oil has to flow between the pump and the bearings, so really I'm just being too picky I'm sure.... LOL

 

[mkIIIman089]

umm...i have no idea what that kg/cm^2 stuff is.

Figure it out, nearly all Japanese guages and the TSRM use it as a primary pressure reading.

Now I know what he's talking about, thx Adjuster, it was more that I was just unfamiliar with that term then what it actually is.

 

[IJ.]

1x Kg/Cm2 is is close enough to 1 bar so 14.5 psi.

 

[TurboStreetCar]

1x Kg/Cm2 is is close enough to 1 bar so 14.5 psi.

Thats what i ment by didnt understand what it was, i ment in relation to psi lol

that was the conversion i was talkign about. but i checked it out today and i had around 5-10psi hot idle and about 40psi 3krpm hot.

 

[IJ.]

Chunks: I edited Colin's post to add in the PSI figures

 

[figgie]

1bar = 100 Kpa = 14.7 psi

btw the reason I throw in Kilopascals is that ALL MAP sensors are Kpa based just that Gm and the likes change it to bar

Kpa is also used in most standalones

 

[IJ.]

1bar>100kpa>14.50377psi>1.019716kg/cm2 if we're being picky

 

[figgie]

1bar>100kpa>14.50377psi>1.019716kg/cm2 if we're being picky

picky?
you mean like when kids are playing on your lawn

[IJ.]
"DAMN LITTLE PUNKS!! GET OFF MY GRASS!!"
[/IJ.]

lmao