Rb25Det R32 Burning Oil After Deceleration

[Traah221]

Alright, so backstory on this issue is as follows.

Series 1 RB25DET, was running pretty solid except for my O2 sensor was going out, caused it to run rough as hell until it warmed up.

Installed an HKS GT2530, but the water lines off the stock block wouldn't fit so I had to delete them at the block, so the turbo is running oil only, no water. Still running a stock Rb25DET ECU and MAF.

I took it for an easy test drive and all was fine, it should be noted that I took my O2 sensor out and soaked it in petrol, then used a heat gun to blast it off, which seemed to help. No more rough running when cold, but the misfires and shudders come back when it's warmed up now.

Once everything got hot though, I noticed some blue/white smoke puff out of my exhaust after I took off from a stop sign. I watched it the whole time while driving normally and shifting, no smoke. It wasn't until I let off the throttle and let the car engine brake, and then gave it some throttle again that I saw another puff of smoke. So, it only burns oil when there is no throttle being applied, and the engine is decelerating.

I popped the hood, and noticed one thing straight off, my PCV hose from the intake side rocker cover to the plenum was kinked, so I replaced that with a factory new one. Not much change, but should I tear down my whole PCV setup and make sure it's working properly?

So, what would suddenly be causing this issue? I find it fishy that it started immediately after the new turbo was installed, but I also mucked with the O2 sensor and somehow the PCV at the same time. I have a Z32 MAF and PowerFC that haven't been installed yet, but would those possibly fix the issue? Or am I looking at something deeper in the head, like valve seals or something?

Thanks in advance!

[mattr33gtst]

My s2 r33 does the same thing when I let off the accelerator, it's only done 87xxx kms and it's running ruff every now and then. I checked oil for water and water for oil... Nothing there

And I'm not loosing coolant and I'm not burning the oil in the sump yet it puffs out smoke??

I figured if it was seals or rings it'd do it under acceleration especially in a boosted car but no only when I let off the accelerator.

I figure maybe dodgy seal in the turbo letting oil in due to maybe shaft play they the waste gate opens up

I'm going to pull my turbo off and inspect the exhaust side for oil

[Traah221]

Find anything interesting Matt?
Update, haven't yet pulled the turbo to look at it, but did a compression test and still 155-160 across all cylinders. Since I didn't have access to a leakdown tester, I cranked the measured piston PSIs to 200 and let them all sit for a few minutes, looking for any change in pressure and/or audible leak from behind the intake, from the rocker covers, or from the exhaust. Nothing, all 6 held 200+ PSI for 5 minutes each with no hissing. Starting to think it's indeed the turbo, since I had a little bit of lateral shaft play.

[533 RYC]

All turbos, even when new, have play. They need it, for thermal growth & oil pressure (if there is no clearance, no oil can flow). So i tend to giggle when a turbo is advertised as having no play.

As a rule of thumb spec, 0.004'' for vertical movement 0.010'' for lateral. These numbers should be used as a guide & taken as maximum values.

Its not a good idea to be running a water cooled turbo not water cooled especially a HKS unit (purely $$$ factor wastage incase you crack the centre housing).

Was the turbo brand new?

Do HKS recommend running an oil pressure restrictor? Do you have one fitted?

The most likely scenario is that the dynamic seal on the turbine side has let go. As you back off the throttle, negative pressure develops in the exhaust manifold, allowing/drawing oil past the dynamic seal & into the turbine housing.

If the turbo was 2nd hand, the seal might have already crapped itself - even though shaft play was ok.

If the turbo was new & you don't have a restrictor if ones needed, then the seal probably has crapped itself