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RB26 Supporting Mods


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I am planning on going single turbo on my r32 GTR. My goal is about 500whp for now. Without knowing the condition of my motor, my local shop wants to do the following:

Inspect block and crank

Replace bearings

Oil pump upgrade

N1 water pump

Metal head gasket

Cams

And I think they wanted to do ARP head studs but I can’t remember for sure.

 

My question is, is all this necessary / worth it for this power level and not knowing the condition of my motor?

Besides injectors, fuel pump, coil packs, boost controller, and ECU, is there anything else I should be doing?

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How many km's has the motor done ?

How old is the motor ?

If it's being stripped down - best to do what you can afford. 

New pistons - decked block - valve guides - oil restrictor 

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5 hours ago, E33 said:

How many km's has the motor done ?

How old is the motor ?

If it's being stripped down - best to do what you can afford. 

New pistons - decked block - valve guides - oil restrictor 

Tac says 75,000kms but unverified. As far as I know, the motor is from 1990 when the car was made but I don’t know if it is the original motor.

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4 hours ago, SnekDoc said:

Tac says 75,000kms but unverified

It's not just unverified. It's obviously not correct. As if there is a 1990 GTR around with only that many km!

Comp test and leak down test it. If it comes up fine there is no reason to take the engine apart.

The weak part of any RB is the oil pump. Read up about what you should do about that.

The rest of it is just fuelling and oil/crankcase breathing control. Do what you have to do for those to keep it healthy.

f**king crack  testing the block and changing the water pump are a sure sign that your local shop have no f**king idea what they're doing, so run a mile right now and find a mechanic with a clue.

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If you're concerned about imminent catastrophic failure, monitor your engine by doing oil analysis and/or cut open your oil filters to look for metal filings. Leakdown/compression is also good to know, if either are poor you want to rebuild before turning up the power. Rebuilding an engine is simpler and less likely to go wrong when it hasn't spun a bearing/bent rods/valves/etc so if you see metal shavings in the oil filter or high bearing content in the oil stop driving the car and get the engine pulled. Once you've built up a baseline over a few oil changes you can crank up the boost and see if the engine is surviving the same way. Also check coolant and oil levels regularly to make sure you aren't leaking/burning anything.

It's a huge waste of time to pull and tear down an engine just to inspect the bearings. Cylinder bore condition + piston condition can be inspected by pulling spark plugs and borescoping it. Oil analysis is relatively cheap, so is cutting open an oil filter.

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1 hour ago, GTSBoy said:

It's not just unverified. It's obviously not correct. As if there is a 1990 GTR around with only that many km!

Comp test and leak down test it. If it comes up fine there is no reason to take the engine apart.

The weak part of any RB is the oil pump. Read up about what you should do about that.

The rest of it is just fuelling and oil/crankcase breathing control. Do what you have to do for those to keep it healthy.

f**king crack  testing the block and changing the water pump are a sure sign that your local shop have no f**king idea what they're doing, so run a mile right now and find a mechanic with a clue.

Yeah that’s what I thought based on what I’ve been reading but I wanted to double check, there’s only 2 shops around me that specialize in RBs, and there other one is overly aggressive and won’t do the setup I want.

So assuming the compression and leakdown test come back fine, it’s only oil and fueling I have to worry about? I’ve read a bit about the oil problems in RBs but I’m not sure how far I would have to take it for this setup. Upgrading the oil pump is probably a given but should I also be installing a restrictor on the head and upgrading baffle in the oil pan? Or anything else?

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1 hour ago, SnekDoc said:

Yeah that’s what I thought based on what I’ve been reading but I wanted to double check, there’s only 2 shops around me that specialize in RBs, and there other one is overly aggressive and won’t do the setup I want.

So assuming the compression and leakdown test come back fine, it’s only oil and fueling I have to worry about? I’ve read a bit about the oil problems in RBs but I’m not sure how far I would have to take it for this setup. Upgrading the oil pump is probably a given but should I also be installing a restrictor on the head and upgrading baffle in the oil pan? Or anything else?

Biggest thing to worry about with these engines is crankcase ventilation. You can have a huge pump pushing tons of oil on the oil feed but you'll ventilate the block if excessive crankcase pressure keeps oil from returning to sump fast enough. That's really what causes the "oil stuck in head" issue. Nissan figured this out with the R35 GTR, which is why the oil pump has both a scavenge pump and a pressure pump as well as significantly improved crankcase ventilation. The pressure pump is your usual oil pump, the scavenge side is on the oil return ports trying to forcibly suck air/oil down the return ports and force the returned oil into the pickup, so it's a "hybrid wet sump" in that regard: https://conceptzperformance.com/aam-competition-oil-pump-isr-treatment-nissan-gt-r-09-r35-aam-isr_p_7433.php

In the context of a wet sump RB26, you can either try and improve the crankcase ventilation system as-is with more breathers. I haven't been able to examine the breather fittings/hoses yet but one "easy" mod may be to put in a checkvalve on the crossover tube and then drill out any restriction that may be present in the stock breather fittings. That would keep fresh air from bypassing the crankcase when on vacuum but allow for maximum flow when on boost. I suspect that you would ultimately need to add another crankcase breather directly off the crankcase though.

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Thanks for this info. I’m still very new to all this. I’m going to keep reading the oil control thread, but based on the first 10 pages it sounds like to solve the oil problem the engine will have to be pulled, the head lifted, and the the sump removed anyway.

It sounds like people are saying to add a crank collar, upgrade oil pump, fit a restrictor in the supply line to the head, add another external return to the sump, and install baffle in the sump. It’s still not clear how necessary this for a mostly street car that will see track days occasionally since this seems to be more of a problem of extended high rpm use.

@joshuaho96I have not read about issues with the crankcase ventilation so maybe that is later in the thread.

While I have already learned much more from this thread, I have lost confidence in my build 🙃

Edited by SnekDoc
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2 hours ago, SnekDoc said:

Thanks for this info. I’m still very new to all this. I’m going to keep reading the oil control thread, but based on the first 10 pages it sounds like to solve the oil problem the engine will have to be pulled, the head lifted, and the the sump removed anyway.

It sounds like people are saying to add a crank collar, upgrade oil pump, fit a restrictor in the supply line to the head, add another external return to the sump, and install baffle in the sump. It’s still not clear how necessary this for a mostly street car that will see track days occasionally since this seems to be more of a problem of extended high rpm use.

@joshuaho96I have not read about issues with the crankcase ventilation so maybe that is later in the thread.

While I have already learned much more from this thread, I have lost confidence in my build 🙃

Modifying engines is hard, if anything it's harder if you intend for this to be a street build that can survive track punishment. Deleting power steering/AC/etc is a much harder pill to swallow to go dry sump, ripping out your trunk liner to fit an Accusump is a lot less palatable for a street-first kind of build, etc.

You have to decide what this car is going to be. If you want it to survive on the track with wet sump you want to turn down the boost, run less aggressive tires, etc. If you want to have 500+ whp for hard drag launches with slicks and hard track use but also street usability something has to give for practicality. The RB26 is really not a great engine in that regard, modern engines are amazingly better at doing what you want to do. Don't forget that to survive races with 600 hp the RB26 had swinging pickups and all kinds of other craziness for the oiling system, the stock RB26 has basically none of that.

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Would I be able to hold off on oil system upgrades for a while if I defer going to the track? Does more boost in itself require more oil flow and higher pressure, or is it the extended high RPMs of track use?

I feel like if I’m going to have to have the engine apart and crank removed to do the oil system upgrades, I might as well save up and do pistons/rods or maybe even a stroker kit.

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@fatz is the man to talk to, see some of his project car threads as he works through what works and doesn't work without spending the earth and spending on things not required at certain power levels.

2 of his build threads to sift through;

 

 

Some other easy-to-understand resources on RB26 rebuilds.

Rebuild basics 

https://www.facebook.com/media/set/?vanity=189006661230825&set=a.418233531641469

 

Extended sump walkthrough

https://www.facebook.com/media/set/?vanity=189006661230825&set=a.399827453482077

 

Crankcase ventilation

https://www.facebook.com/media/set/?vanity=189006661230825&set=a.42413259438489

Edited by JGTC
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On 11/1/2020 at 2:27 AM, SnekDoc said:

Would I be able to hold off on oil system upgrades for a while if I defer going to the track? Does more boost in itself require more oil flow and higher pressure, or is it the extended high RPMs of track use?

I feel like if I’m going to have to have the engine apart and crank removed to do the oil system upgrades, I might as well save up and do pistons/rods or maybe even a stroker kit.

More boost creates more blowby, which stresses the PCV system more. More blowby means more oil spitting out the breathers. The crankcase vent mods are really to solve that issue, track use just means spending more time at high boost. Street use just implies you're not spending very long at high boost.

If you're going down the road of a built engine think carefully about the trade-offs there. 2618 forged pistons are very tough and make big power but they do not live long lives. For something that is street-first you probably don't want to have an engine that has quite a lot of piston slap and needs to be carefully and lovingly warmed up, it's better to have a piston that calls for a tight piston to wall clearance for street use. Don't wildly overbuild an engine for way more power than you want. Tight piston clearance also helps with reducing blowby, so for track use if you aren't too wedded to huge power it'll make oiling less of a headache.

Really, every time I think about these issues with the RB26 the real solution is to sell the car and get a 996 Turbo but I have some kind of brain damage that keeps me from doing the obvious, cost effective solution.

Does anyone know if the Tarmac Solutions sump is going to be enough with just 1.5L extra? I'd like to only bump up to ~6L of oil capacity instead of 8-9L but I'm not sure if it's a good idea.

Edited by joshuaho96
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Okay after doing some more reading, I think this will be my plan.

Assuming compression and leakdown test come back fine I will leave the stock oil pump for now, don’t pull the engine, and shoot for about 330kw for now. I’ll stay away from the circuit and keep it under 7500rpm.

In about 6 months or so, pull the engine and make it track-ready:
HKS or nitto oil pump
Sump baffles
Valve cover baffles
Restrictor in oil feed to head
Crankcase ventilation
2.8 stroker
Oil cooler
Potentially extended sump

Does this sound okay or is this a bad idea to wait and do the oil mods later?

Maybe I will also do crankcase ventilation now since it sounds like it can be done easily by venting via the dipstick tube to oil/air separator?

 

Edited by SnekDoc
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3 hours ago, SnekDoc said:

Okay after doing some more reading, I think this will be my plan.

Assuming compression and leakdown test come back fine I will leave the stock oil pump for now, don’t pull the engine, and shoot for about 330kw for now. I’ll stay away from the circuit and keep it under 7500rpm.

In about 6 months or so, pull the engine and make it track-ready:
HKS or nitto oil pump
Sump baffles
Valve cover baffles
Restrictor in oil feed to head
Crankcase ventilation
2.8 stroker
Oil cooler
Potentially extended sump

Does this sound okay or is this a bad idea to wait and do the oil mods later?

Maybe I will also do crankcase ventilation now since it sounds like it can be done easily by venting via the dipstick tube to oil/air separator?

 

Yeah, the first step is fine. I would just install a Nismo oil separator or comparable while you're in there. Low boost, tune, take it easy for a while and make sure the engine is healthy. Dipstick vent and oil cap vent are really last resorts, don't bother unless you're really having issues with blowby, which you shouldn't at low boost and an internally stock engine.

If you're going to run a high flow oil pump you should go with an extended sump. The two go together, generally speaking.

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