Found This Interesting Read On Rb26 Oil Issues What Do U Think?

[GD51LA]

Matt owns/runs a shop in Japan building high HP motors - very high HP motors. This is long, but a good read:

If you're looking for soultions here, delete it because there are no

solutions for a fictional problem. It's going to be dripping with

sarcasm, too! What fun. Hang on to your shorts.

That's right. You didn't read it wrong. The Internet spread BS on

this subject has finally reached "urban legend" status and I feel

it's time to set the record straight, vent, shed some light,

whatever. What pushed me over the edge is a new post on Hybrid Z

where the guy (Boosted Z I think?) gets some good #'s on the dyno

but sees oil pressure falling off around 8,000 rpm. The first

questions asked are "Do you have the oil restrictor?" etc... sigh...

Are you serious??? Now we've reached the point where the drain back

issue is so bad that the engine can't even do ONE DYNO PULL without

all five quarts of oil ending up "trapped" in the head?? Give me a

break, man.

What's funny is that the RB26 is, what, 18 years old, but it never

had oil drain back issues until Tomei started selling the stupid

restrictor with a little hand drawn picture of high oil level

without the restrictor and low oil level with it. Actually, it's not

a bad idea, but I'm calling it stupid because of what it started.

A little perspective:

Obviously Nissan doesn't think it's a problem because they never

addressed it in the 33 or 34 engines. Oil returns and pressure

orifice are the same as far as I can tell. At least not any major

changes for what seems to be a catastrauphic problem (sarcasm).

Would someone PLEASE explain to me why Nissan can take a bone stock

R32, R33, or R34 to the Nurburgring and go at full throttle, lap

after lap, eight plus minutes per lap and never have oil drain back

problems that rob the sump of oil, but a guy on an Internet forum

can't do one lap of a two minute circuit or even one dyno pull, have

oil pressure sag, and have everyone under the sun call out for

restrictors and additional drain backs? No, not really; that was

rhetorical.

I've seen N1 and Super Taikyu race engines up close and even inside.

Never seen any additional drain backs. Not sure of the Super GT

engines, but they probably use a dry sump with scavenge in the head

and no drain backs, to keep oil off the crank. Saw the HKS Drag GT-R

up close too, and never noticed anything like that. There are

probably thousands of track GT-R's driven in Japan alone that don't

have this problem.

My experience:

Power numbers's? Don't know. Our dyno's here won't hold much over

700 without slipping tires (at least that's as high as I can get

it), and I'm not a big fan of numbers on a piece of paper, so I

really don't care. However, I can tell you that the most powerful

RB26 I've ever built burried a 320km/hr (198.838 mph and don't tell

my mom) speedo on the expressway at over 10,000 rpm. Modified HKS

pump, no aftermarket restrictor, no additional drain backs, oil

pressure holding at a rock-solid 115 psi.

In fact, I've never used an aftermarket restrictor or additional

drain back in any engine I've ever built... I've never had an oil

pressure problem in any RB engine. Ever. I build 'em loose, too.

Maybe some people are having problems. With the above, I doubt very

much it's a "pooling in the head" problem.

Here's why:

Suck air in the oil pump and oil pressure goes to zero almost

instantly. No "falling off in the top end". Some people shift gears

and the oil pressure is magically restored (even though all the oil

is in the head), only to have it fall off again as soon as the rpm's

climb back up.

Oil pressure falling off in the upper rev range can be caused by

several things, the most common of which is cavitation. I would put

money on it that most people running RB Z's are using the steel pans

from the Z31? This not only eliminates the excelent RB26 sump

baffeling, it also precludes you from using the RB26 windage trays.

Foamy oil cavitates. What happens is tiny bubbles in the oil enter

the pump under huge vacuum. A bubble that already exists is much

easier to expand into full blown cavitation than oil with no

bubbles. The bubble(s) expand to many times their own size, taking

up space originaly reserved for oil. Once it hits the pressure side,

the bubble collapses, but the damage is done. Less oil went through

the pump. The faster the pump spins, the more vacuum is created, and

the worse the problem becomes. Oil pressure that falls off as the

revs climb is almost always caused by cavitation. This can also be

caused by a too-small or too-restrictive oil pick up. Moving it all

the way to the back of the engine couldn't possible affect this,

could it?

I watched a video of a guy going around the track in an RB Z. On

braking and turning in only one direction the oil pressure would

zero out almost instantly. Once the car straightened out or throttle

was restored, pressure jumps back to normal instantly. Once again

the common consensus was the 'ol PIHS (pooling in head syndrome). On

decel or only turning in one direction? PIHS or bad baffeling in the

pan/pick up location? You be the judge, but use common sense.

The restrictor is good:

But for the wrong reasons. The right reason is the same as a small

Chevy or any other engine for that matter... The head doesn't have

heavy rotational forces for two reasons: There's no heavy stuff

swinging around, and it's only moving at half the crank speed. It

doesn't need a lot of pressure, especially because the cam to lifter

interface is fed by oil dribbling out of the cam journals. Pressure

in the head is wasted, which is the reason for the factory

restricotr. A smaller restrictor will keep the pressure to the

bottom end higher in the rev range due to decreased VOLUME wasted in

the head.

The additional return is bad:

There are two large returns in the rear of the head and several

throughout the length of the left side of the motor. Due to crank

windage, the ports on the left side of the engine are subjected to a

vacuum because the crank is pulling down on that side of the engine.

The one in the rear, right supplies windage to the head for crank

case ventilation. Air doesn't pull down the left side if it can't

come up the right. Under hard acceleration, oil wants to move to the

rear of the engine. Some people install a large line from the rear

of the head back to the right side of the front sump in the GT-R

pan. Anyone see a problem with this? There's actually two. Under 1g

of acceleration, not only will oil not move forward through this

line back to the front of the engine, it gives the oil in the sump

another path to exit the sump. Reason #2 is that the right side of

the engine is pressure side and not the suction side. Crank windage

at higher RPM can push oil back into the tube if it's not very

carefully baffeled. It could work well in a rear sump if the hose is

almost straight down and entering the left side of the engine. But

this as assuming there really is a drain back problem.

What I have seen/done:

An additional line from the back of the head, under the plenum, back

to the RADIATOR. Additional coolant movement out of the head. Very

common mod on drag engines. Maybe someone saw this somewhere and

mistakenly thought it was for oil and ran with it? Who knows.

With the additional oil restrictor in place, the oil level in the

hed would certainly be lower than without it, but I assure you that

even with the stock restrictor, it's not even close to a problem.

Especially not the problem it's been made out to be.

Anyway. I feel better and will now step off of my soap box. I'm sure

there will be arguments from people who had PIHS cured by these

mods, or whatever, but you really need to stop and think about it.

Especially given the factory stock cars not having problems on the

ring, etc.

Matt

[Bick033]

Good read Interesting it is.

[KiwiRS4T]

Oil control problems - normally only on the track or dyno - are not fictional although the causes are not always well understood.

The number of RB powered cars I have seen pull up at the track with zero oil pressure is not funny (luckily hasn't happened to me).

The other fairly common oil problem is excessive amounts of oil coming out of the top of the engine through the breathers or elsewhere ( took me two years to fix this).

The 57 page oil control thread http://www.skylinesaustralia.com/forums/topic/110680-oil-control-in-rbs-for-circuit-drag-or-drift/?&hl=sk+oil+control has canvassed all these issues rather thoroughly and come up with solutions that have been proven to work.

I don't know how the big power Japanese engines are built but I do see efficient breather systems with often more than one catch can and or air/oil separator featured on them usually fed into the turbo intake which will have some scavenging effect. Also I imagine some of the long distance cars will have dry sump set ups which is of course the ultimate fix.

[Dahtone Racing]

Tell him to put a nitto pump on an engine with a stock restrictor and see how much joy he has.

I just fixed a car with this problem without removing the head and while not perfect it's the best compromise when the engine wasn't setup correctly from the start.