oil weight VS oil pressure??

[d1 mule]

hey, got the car tuned last week and it started to knock at high revs on the dyno so they stopped, i since noticed oil pressure was at about 10 psi at idle when warm which seems low to me??? so im wondering if the oil i put in is too thin?? was running Fuchs titan GTO 10W 40. the engine is a ae92 4agze with 89000kms

cheers

[MR2BOY23]

a 40w oil doesn't sound thin to me

You could experiment with a higher grade- example penrite 10w-50 see if that helps increase the pressure slightly

Even a castrol edge 10w-60, though this would possibly be too thick for your application

[l1ttle_d3vil]

i put a cheapy autogauge oil pressure gauge in mine which seemed to read really low so hooked up a proper mechanical / engineering gauge to make sure and it read the same, was around 10 - 15psi at idle from memory.

edit - this is on an aw11 4agze running 15/40

[d1 mule]

yeah its got a redline mechanical oil pressure gauge, and i have installed a remote oil cooler/filter kit which might have some affect i guess as im sure with the same gauge on the 4age it was at least 20pis at warm idle. might try some 10-15W 50 once the bearings done then

[IH8TEC]

mine runs 25-30psi at idle, 10 seems really low, but i think some supra engines are at around 4-5psi at idle,

don't need much at idle as there is no load or anything on it. but up high you'd want 50+ i'd say.

[matt dunn]

mine runs 25-30psi at idle, 10 seems really low, but i think some supra engines are at around 4-5psi at idle,

don't need much at idle as there is no load or anything on it. but up high you'd want 50+ i'd say.

10 is not too bad if the oil is really hot.

Normaly minimum you'd want is 10 psi per 1000rpm,
so 20 and 2000, 30 at 3000 etc etc

[d1 mule]

i might look into getting the oil pump re built while the sump is off i suppose, iv also got a oil temp gauge to hook up once its all back together too. im basing my concern on the 4age that came out of the car that had approx 20psi at idle and got up to 80psi when caning it.

the tuner said the pressure was weird when it was on the dyno too, say holding at 3k then foot flat the press would be t 35psi drop down to 25ish then pick up???? weird eh

[IH8TEC]

stuff can be weird on the dyno like that as the car is put under alot more stress than normal. and oil temps normally go bloody high, mine did anyway, even with the oil can and dyno room fan.

4age oil pumps are pretty good for pressure.

matt - now you mention it, when i've seen my oil REALLY hot, as in 125ish deg, it's been down to about 10-15psi on idle. only happened on dyno.

[matt dunn]

matt - now you mention it, when i've seen my oil REALLY hot, as in 125ish deg, it's been down to about 10-15psi on idle. only happened on dyno.

I know my car idles with the oil pressure light on after a race as the oil is so hot and thin, but it's not a problem. It has a high pressure switch but it's still around the 10 to 15psi at 800rpm.

[tsoob]

im running a 20/50w which is quite thick this is for running in on but yeah my pressure is like 20 and goes up to 80 under boost

[Bazda]

Rebuild the pump.. Just buy a new one. I dont think you can buy the gears individually anyway.

Also if the pump is stuffed it usually scores the inside housing which is part of the whole thing.

They are around $240 from the TS sponsor on here.

But id first check your pressure on the road, at all rpms and see what the results are before you do anything

[fangsport]

yeah its got a redline mechanical oil pressure gauge, and i have installed a remote oil cooler/filter kit which might have some affect

are you checking oil level at engine stop, or at idle??
the bosses engine runs a similar system, but the guy who installs the engine checks oil level at engine stop, therefore running approximately 2l of oil to few as it takes close to a litre in the plumbing and holds close to a litre in the head (FJ20). due to this, he runs bearings every time he runs it!!

[d1 mule]

i checked oil level after i filled it then after it has been runnning for a while. I initially put the whold 5Litres in as i assumed the oil cooler and lines would be about a litre, it was just below the F on the dipstick.

should have the bearings out this week will post pics

[matt dunn]

Did you know that incorrect tuning and detanation can cause run bearings too,
so have a look at the top of the pistons.

[d1 mule]

im not taking the engine apart, just taking the sump off in place ish, doing the bearings and slapping it back together to have the tune finished asap

[IH8TEC]

keep the oil to find the problem before you run it again, mine did big end on dyno, turned out to have water in the oil. then redid the whole engine, pulled all apart, checked everything.

now good as, was weird but problem fixed.

[bluemaumau]

any idea how you ended up with water in the oil brendon?

[MAGN1T]

Once you've spun a bearing, replacing them always results in another failure.
That's because the rod and crank will also be damaged.

There's 2 reasons bearings fail. One of them is oil starvation. The other is detonation. So failing on a dyno will usually be detonation and the fault of the tuner.
Easy to tell. Once the bearings come out, the one that's failed will either be too wide all the way around...probably starvation , or it will be too wide at one point. That one point is where the bearing takes the load between the crank and rod whilst at TDC. If it looks like that then suspect detonation (same as hitting it with a hammer).
Either way the only safe way to fix it is a reground crank and a resized rod. Cracktest too.

If the oil pressure fluctuates with load, it's a sign of a broken piston because crankcase pressure will also be fluctuating with load. An oil pressure gauge doesn't read oil pressure, it actually reads oil pressure plus crankcase pressure, which should of course be zero.
edit, oil pressure will also fluctuate when the level is too low, that's because it sucks up air as well as oil.

Steve

[1I1]

If the oil pressure fluctuates with load, it's a sign of a broken piston because crankcase pressure will also be fluctuating with load. An oil pressure gauge doesn't read oil pressure, it actually reads oil pressure plus crankcase pressure, which should of course be zero.

Steve

As in oil pressure is at 30psi at 3000rpm with part or no throttle, give car full throttle and it dips down to say 25psi for a second and straight back up to 30psi?

[d1 mule]

got the bearings out look to have been hot and scuffs on them?? but in saying that i dont know what a run bearing looks like