Jump to content
SAU Community

Recommended Posts

Hello

Got some major headache herefrown.gif

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 (hoses connected the right way)
Crank is a R33 with good oil pump drive (modded to 0.2mm clearance)

I don't really know what it can befrown.gif

I see your issue its in your specs however you do have enough pressure for a street engine, 10 PSI per 1000 is right however your idle pressure should be a little higher, on the RPM side your OK.

When running around.003" clearances this is typical, those clearances are for all out race engines.

We have just built our bottom end with similar clearances, however.....

You want to be running at minimum a 50 weight of oil, if not 60 weight ideally, those clearances are far too loose for a 40 weight of oil, we will be running straight 60 weight (not multi grade) oil on .003" clearances.

Second part is in your oil pump, a stocky with reimax gears, in our case we used a Tomie pump, reason being was the external oil pressure adjustability for pressure control combined with more volume.

Start testing with a thicker oil and report back......try a 25-50 oil for starter if its a streeter with those clearances.

Im also assuming the clearances were checked properly with a mike and not plastigauges......

  • Like 1

I see your issue its in your specs however you do have enough pressure for a street engine, 10 PSI per 1000 is right however your idle pressure should be a little higher, on the RPM side your OK.

When running around.003" clearances this is typical, those clearances are for all out race engines.

We have just built our bottom end with similar clearances, however.....

You want to be running at minimum a 50 weight of oil, if not 60 weight ideally, those clearances are far too loose for a 40 weight of oil, we will be running straight 60 weight (not multi grade) oil on .003" clearances.

Second part is in your oil pump, a stocky with reimax gears, in our case we used a Tomie pump, reason being was the external oil pressure adjustability for pressure control combined with more volume.

Start testing with a thicker oil and report back......try a 25-50 oil for starter if its a streeter with those clearances.

Im also assuming the clearances were checked properly with a mike and not plastigauges......

Funny I was just thinking the opposite - being old school I like to check with plasti- gauge after establishing the clearances by measurement. Using an N1 pump my basically stock RB30 was running at well over 100psi from cold at 5000rev/min. The OP's pressures should be adequate with your suggestion of a heavier oil and maybe less oil control issues will present themselves!
  • Like 1

Funny I was just thinking the opposite - being old school I like to check with plasti- gauge after establishing the clearances by measurement. Using an N1 pump my basically stock RB30 was running at well over 100psi from cold at 5000rev/min. The OP's pressures should be adequate with your suggestion of a heavier oil and maybe less oil control issues will present themselves!

Im also old school and only use plastigauge for double checking, its a guide only and not accurate, i also use a bore gauge but i also back it up on mockup stage with a plastigauge to double check myself, much like yourself, you can never check enough, it only takes a small error of not having the bore gauge setup correctly to get it wrong, thats where platigauge is a good secondary measure but remember its not accurate and a guide only.

We had our machinist set up my clearances while the block and crank were in to my specs, got it home and started a few mock assemblies, used a platsigauge to double check clearances and found the rods at .002" when i specified .003".

Got my bore gauge out, yep he was off, had to go out and get some X stamped ACL bearings and mix and match them with the stock sized ones while checking with my mike for accuracy, finally double checked one more time with plastigauges.

Turned out he had the apprentice set up my clearances after going over to let them know it was wrong...... the apprentice didnt know how to properly zero a bore gauge.....

So plastigauges can be good for the obvious, but they are not accurate enough for fine detail, great for catching obvious error though.

Edited by GTRPSI
  • Like 1

clearensen both checked with plastigauge and bore gauge.

i'll try a 20-50w oil

remember that the values i've given was after only a few minutes so i guess the pressure will be even lower when the oil is warmer

i come from the 4g63 world and we have like cold-idle @8bar oil pressure with 10w-40

This is my old car

https://www.youtube.com/watch?v=Wu-mbkUcIRM

9.33/quar mile, 750whp mitsubishi mirage

If your doing like in the clip above your clearances are OK, your issue is in the oil weight used and pump setup you selected.

Hopefully just the oil weight will sort you out to something a bit better.

Did you shim up the oil pressure relief valve for a bit more pressure before you closed the engine?

  • 2 weeks later...

This sounds really odd.............

You can't be missing the rod bolts and be complaining about oil pressure. You'd have much more to complain about.......

ALL hex bolts sounds impossible. The thing would have fallen apart during installation when turning the engine over. Something in the description must be off, but I can't work out what else it could be.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
    • Hi,  Just joined the forum so I could share my "fix" of this problem. Might be of use to someone. Had the same hunting at idle issue on my V36 with VQ35HR engine after swapping the engine because the original one got overheated.  While changing the engine I made the mistake of cleaning the throttle bodies and tried all the tricks i could find to do a throttle relearn with no luck. Gave in and took it to a shop and they couldn't sort it. Then took it to my local Nissan dealership and they couldn't get it to idle properly. They said I'd need to replace the throttle bodies and the ecu probably costing more than the car is worth. So I had the idea of replacing the carbon I cleaned out with a thin layer of super glue and it's back to normal idle now. Bit rough but saved the car from the wreckers 🤣
    • After my last update, I went ahead with cleaning and restoring the entire fuel system. This included removing the tank and cleaning it with the Beyond Balistics solution, power washing it multiple times, drying it thoroughly, rinsing with IPA, drying again with heat gun and compressed air. Also, cleaning out the lines, fuel rail, and replacing the fuel pump with an OEM-style one. During the cleaning process, I replaced several hoses - including the breather hose on the fuel tank, which turned out to be the cause of the earlier fuel leak. This is what the old fuel filter looked like: Fuel tank before cleaning: Dirty Fuel Tank.mp4   Fuel tank after cleaning (some staining remains): Clean Fuel Tank.mp4 Both the OEM 270cc and new DeatschWerks 550cc injectors were cleaned professionally by a shop. Before reassembling everything, I tested the fuel flow by running the pump output into a container at the fuel filter location - flow looked good. I then fitted the new fuel filter and reassembled the rest of the system. Fuel Flow Test.mp4 Test 1 - 550cc injectors Ran the new fuel pump with its supplied diagonal strainer (different from OEM’s flat strainer) and my 550cc injectors using the same resized-injector map I had successfully used before. At first, it idled roughly and stalled when I applied throttle. Checked the spark plugs and found that they were fouled with carbon (likely from the earlier overly rich running when the injectors were clogged). After cleaning the plugs, the car started fine. However, it would only idle for 30–60 seconds before stalling, and while driving it would feel like a “fuel cut” after a few seconds - though it wouldn’t fully stall. Test 2 – Strainer swap Suspecting the diagonal strainer might not be reaching the tank bottom, I swapped it for the original flat strainer and filled the tank with ~45L of fuel. The issue persisted exactly the same. Test 3 – OEM injectors To eliminate tuning variables, I reinstalled the OEM 270cc injectors and reverted to the original map. Cleaned the spark plugs again just in-case. The stalling and “fuel cut” still remained.   At this stage, I suspect an intermittent power or connection fault at the fuel pump hanger, caused during the cleaning process. This has led me to look into getting Frenchy’s fuel hanger and replacing the unit entirely. TL;DR: Cleaned and restored the fuel system (tank, lines, rail, pump). Tested 550cc injectors with the same resized-injector map as before, but the car stalls at idle and experiences what feels like “fuel cut” after a few seconds of driving. Swapped back to OEM injectors with original map to rule out tuning, but the issue persists. Now suspecting an intermittent power or connection fault at the fuel pump hanger, possibly cause by the cleaning process.  
×
×
  • Create New...