RB26 blow by problems

[Skyrel]

I have some blowby problems that I need to sort out, so instead of reinventing anything I was hoping for some input for mye setup. My car is a streetcar that gets abused regularly at trackdays, and has not had the most common oil control mods installed (restrictors, head return etc). Mods of interest are:

GTSS turbos 1.1bar
HKS downpipe and exhaust
Mines ECU 600cc injectors
385 wheel hp

To help with blowby I installed:
Mines head baffles
Nismo oil separator


Long story short, this did not help at all. My turbo intake is a complete mess after just half an hour ont the track, and if I go anywhere above 7500RPM or so I get clouds of smoke behind the car.



At first I considered a second catch tank post oil separator. But I think it would be best to remove the Nismo oil seperator and install a catch tank with separate hoses from each cam cover, blocking off the PCV and see how that goes. But then I started searching and after reviewing a lot of posts that are talking of how the PCV system benefits the engine, I got insecure if this is smart for a streetcar..


Anyone with some educated answers out there?

[AlexJ]

What size restrictor have you got in the turbo oil feeds? ball bearing turbos need something to reduce the flow or they will blow oil past the seals.

[Skyrel]

As far as I know all garratt BB turbos come with a restrictor, but I have no idea of the size. Are you thinking I need to install a second restrictor in the banjo?


Thanks


Edit: To test this, I could simply clean the intake and dump the valvecovers to ground for a while. Then inspect the inlet to verify if the problem is blowby or turbo seals.

[AlexJ]

Originally Posted by Skyrel

As far as I know all garratt BB turbos come with a restrictor, but I have no idea of the size. Are you thinking I need to install a second restrictor in the banjo?


Thanks

You are right, I think they do, I also have GTSS and iirc they did. They were second hand to me and iirc the restrictor was in the banjo bolt itself. But if you have especially high oil pressure you may need additional restriction.

Worth a try I think, because otherwise you have bigger problems. My setup is very similar to yours, with the addition of a restrictor in the head oil feed and blocked off PCV, I run 15w50 oil and overfill massively. I've never filled the catch can after thousands of track miles.

[AlexJ]

Originally Posted by Skyrel

Edit: To test this, I could simply clean the intake and dump the valvecovers to ground for a while. Then inspect the inlet to verify if the problem is blowby or turbo seals.

sounds like a good plan

[Skyrel]

Originally Posted by AlexJ

You are right, I think they do, I also have GTSS and iirc they did. They were second hand to me and iirc the restrictor was in the banjo bolt itself. But if you have especially high oil pressure you may need additional restriction.

Worth a try I think, because otherwise you have bigger problems. My setup is very similar to yours, with the addition of a restrictor in the head oil feed and blocked off PCV, I run 15w50 oil and overfill massively. I've never filled the catch can after thousands of track miles.

I cannot remember if my banjos had restrictors. I also got the turbos second hand, so there is a possibility I used the OEM banjos. With that said, the turbos probably has restrictors in them (I think all Garrett BB do) and the banjos could be secondary restrictors.


I dont have very high oil pressure, I have an OEM pump with just over 4 bar on the OEM gauge. I have thinner oil than you do though, 5-40, but I run a very good oil cooler and of course overfill it like mad



Ill try the ventilation thing. If theres still oil in there, ill need to do the painful job of inspecting my banjos for restrictors Thanks for the advice, I had not thought of this at all






PS

Im considering to remove the PCV system as well, and ventilate the cam covers in a seperate tank. But then I read that the PCV system should be kept in plase in street cars.. Any thoughts?

[FRRACER]

With Oem and N1 pumps more so you need to use a 0.8mm restrictor. I know they come with 1mm as standard but no issues with 0.8mm and this is what HKS supplies with their kit. BB turbos only need a mist of oil. Also consider mines camb baffles to help with blow by

[AlexJ]

Originally Posted by Skyrel

PS

Im considering to remove the PCV system as well, and ventilate the cam covers in a seperate tank. But then I read that the PCV system should be kept in plase in street cars.. Any thoughts?

The PCV system is strictly for emissions, just block it off unless you local laws require it.

[Skyrel]

Originally Posted by FRRACER

With Oem and N1 pumps more so you need to use a 0.8mm restrictor. I know they come with 1mm as standard but no issues with 0.8mm and this is what HKS supplies with their kit. BB turbos only need a mist of oil. Also consider mines camb baffles to help with blow by

So HKS adds a second restrictor on the turbos? Hm. I cant remember if the seller gave me a set of banjos or if I used the OEM`s. I think the front turbo banjo is ok ish to remove, so its probably fastest to just remove the one I have to take a look. Thanks.

[Skyrel]

I just removed the banjo, and it is a standard large diameter banjo bolt.


Does anyone know who supplies these?

[GT-R David]

HKS banjo bolts is what most people use

[FRRACER]

https://instagram.com/p/BWqY0yBjaCN/

[UnderDriven]

Originally Posted by AlexJ

The PCV system is strictly for emissions, just block it off unless you local laws require it.

I disagree with this, it has other benefits and is worth keeping.

[FRRACER]

PCV 101

https://youtu.be/EPIfI9aZHt4

[Skyrel]

Quick update: I installed the restrictors, and the turbos still had lots of oil in the inlets. I cleaned it up, and blocked the breather hose on the rear turbo. I then took a new hose from the oil separator and to the driver side of the engine to the ground, cleaned up the turbos and took the car to a drag race. Launched and shifted @ 8000RPM for 7 runs.


The result was a small oil puddle under the car just where the new breather hose dumps. Im yet to inspect the turbo inlets, but I am quite sure they will be fairly clean as the new breather dumped a lot of oil to the ground.

So it seems I had a turbo leak AND a blowby, but Im yet to see if the turbos stopped leaking. I will inspect this soon.







On a side note I have noticed that the turbo lag has improved dramaticly where before they where sluggish from 4-5000RPM. I also had a boost cap of 1.1 bar before, now I run 1.2 bar up to 8000RPM. I believe that the turbos had to much oil supply before causing the problem. So the restrictors really made a difference. Im also very happy with the performance of the car, 7.75 seconds 1/8 mile, 1.7 60ft.

[CabbageMS]

Originally Posted by Skyrel

Quick update: I installed the restrictors, and the turbos still had lots of oil in the inlets. I cleaned it up, and blocked the breather hose on the rear turbo. I then took a new hose from the oil separator and to the driver side of the engine to the ground, cleaned up the turbos and took the car to a drag race. Launched and shifted @ 8000RPM for 7 runs.

On a side note I have noticed that the turbo lag has improved dramaticly where before they where sluggish from 4-5000RPM. I also had a boost cap of 1.1 bar before, now I run 1.2 bar up to 8000RPM. I believe that the turbos had to much oil supply before causing the problem. So the restrictors really made a difference. Im also very happy with the performance of the car, 7.75 seconds 1/8 mile, 1.7 60ft.

I'm very interested in this. I am on similar setup, 1.15bar on GT2859-9 turbos. I have lots of oil in both front and rear turbo intake (a sign that it's likely to be too much turbo oil pressure rather than PCV as PCV only reconnects to back turbo inlet?). I also have a lot of lag, only hitting 1.1 bar at around 4500rpm. So what exactly needs to be done? Use the HKS banjo bolts with restrictors in, in addition to the ones that come in the turbo? Or replace the ones in the turbo?

[Skyrel]

Im a little angry with myselfe for not updating this, I always try to keep solutions updated, but I guess my build thread got the update and so this was forgotten.

https://www.gtr.co.uk/forum/400890-s...r33-gtr-4.html


Its fairly detailed in there. In short, I installed a 0.8mm banjo restrictor on each turbo, and the turbos responded with better response and more boost pressure. I had to do some serious work with the breather system to make it work though.

Cheers