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Discussion Starter #1
Hello

Got some major headache here:(

I've rebuilt an rb26 after oil-pump failure

But when i start it up with 10-40w oil (20'c oiltemp) i got oil pressure of 2.5bar/1200rpm that drops to 1.5bar/1200rpm after 2mins. After 2mins i tried 3000rpm = 3bar
This seems way to low for me.

I've measured the pressure with a mechanical and one electrical gauge, not the dash-gauge.

I've done the rebuild myself (lot of expereince with 4g63, non with rb26)

Oil pump is a good used condition stock case with NEW reimax gears.
Main bearing clearences is 0.07mm
Rod bearings cleaences is 0.07mm
Oil squirters is torqued to spec.
Tomei 1.5mm oil restrickor to head.
Grex/Trust oil filter relocation and oil cooler kit
Crank is a R33 with good oil pump drive (modded to 0.2mm

I don't really know what it can be:(
 

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Your clearences seem a little large should be 2 thou what I beleive is .05mm, you will prob find the n1 oil pump doesn't flow enough for them clearences from what I've been told if you fit a better flowing pump like a tomei you will prob be fine
 

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I think I agree with the above, I just built mine with similar clearances to you. So on the large side which does require more flow from the pump, I'm running a hks pump which is higher flow so get better oil pressure than you are getting. I get 2.5bar on hot idle with running in oil and max of 6bar at revs. I plan to put a thicker oil in the engine to help protect the bearings, just got some Fuchs 15w50. I'm not sure it will help with the oil pressure but it is recommended when running larger clearances.
 

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I think I agree with the above, I just built mine with similar clearances to you. So on the large side which does require more flow from the pump, I'm running a hks pump which is higher flow so get better oil pressure than you are getting. I get 2.5bar on hot idle with running in oil and max of 6bar at revs. I plan to put a thicker oil in the engine to help protect the bearings, just got some Fuchs 15w50. I'm not sure it will help with the oil pressure but it is recommended when running larger clearances.
Why did you just not build it to tighter tolerances and not have to run thick oil and high flowing pumps making the pumps work hard? I don't understand it tbh
 

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Discussion Starter #6
Sorry misswrote The clearances
0.05 Rod and 0.07 main.

Shop manual says 1bar/900rpm 3bar/2000rpm and 4bar/4000rpm
 

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pressures still seem a little low to me but really all you need is enough pressure to keep the bearing floating. So as long as the pressure reaches 4bar then you're good
 

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Your still well within spec max spec on rod and mains is .090 thou of an inch mine are .050 on both rod and mains I currently get just under 3 bar got idle and just under 7 bar cold start and I'm using fuchs 15w50 race oil
 

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There are benefit to running larger clearances. There are many articles which talk about the trades offs

Bingo mikey hit the nail on the head advances in oil specs have changed so much tighter clearances are a bad thing so to speak ask any of the tuners 0.050 is the perfect clearance for rb26 bearings even nissan state upto 0.090 max clearance normal is 0.035-0.040
 

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Your still well within spec max spec on rod and mains is .090 thou of an inch mine are .050 on both rod and mains I currently get just under 3 bar got idle and just under 7 bar cold start and I'm using fuchs 15w50 race oil

You must mean .090 mm not thou? 0.090mm is 3.5 thou
 

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what does your pressure do at cold start ? does it hit 6+ bar cold ?
 

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Discussion Starter #18
20w-50 oil was better , not got 3.5bar cold start idle , and 1.5bar hot idle.

no problem with 5bar hot oil above 5000rpm
 

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20w-50 oil was better , not got 3.5bar cold start idle , and 1.5bar hot idle.

no problem with 5bar hot oil above 5000rpm

if you've got 4 bar by 4000 rpm then your fine I wouldn't worry, motul 20w60 300v will help even more if the clearances are on the large side.
 
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