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Full build RB25, smoke valve covers, comp/leakdown fine

Lopin18

By Lopin18,
in Engines & Forced Induction

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Lopin18 Contributor

Lopin18

Posted
Posted

This will be a weird one:

RB25 Neo head on rb25 neo block with 26 internals (CP, Eagle, ACL, ARP, Cometic HG 2.5mm), enlarged oil returns, blocked feed, 1.1mm on the other one. VTC inactive. Rear head vent to crank, big catch can vented with oil return to pan and vents to crank and valve covers, Jun oil pump. Tomei baffle box on the oil pan.

 

This was fully done with everything i saw around. Everything was done as perfect as i could. Ever since day 1 ive had a weird white vapor coming from the valve covers (pcv valve hole open to air, i never got it into the catch can), like a light smoke, almost like something burning slowly. And a tick on the head after warm up (i meassured valve to cam clearance as best as i could and its within spec, but im guessing one was too tight maybe...) i ignored it for now. Compression was fine after initial start and break in, 175 psi.

 

Anyways, i made over 450hp with clutch slipping, a lot of things happened, in the end it was ran hard, it worked. Last weekend i went to a drift demo we had. PCV hole was open to air still, engine squirted oil on the bay, oil temp was around 270-290, it was hot as hell. oil pressure was fine all the time, blew the turbo seals BUT i had more white smoke comming from the pcv hole now. shut down, it kept smoking for quite a while, like something was burning. i dont know what that is, maybe its the shitty mobil 1 mineral oil? i dont know.

Due to the turbo smoking, i towed the car home, in my mind i broke a piston ringland. But not i didnt. still have 170 psi compression, leakdown @ 75 psi was only showing 2% - 4% according to the instructions on the leakdown tester (4-8 psi loss), compression test was done cold and hot after rolling the car to the shop. leakdown was made cold.

This was quick check while hot: at home, 8pm, i shined a light on the pcv hole and i could clearly see the smoke being pushed out, giving it throttle it clearly pushed it harder.

 

So what now, compression is fine, leakdown is fine, but engine seems to be smoking from the covers for some reason. im leaning towards BAD oil doing something weird under heat. I supposed blowby would be noticeable on the leakdown, but its fine right? (75psi in, 72psi held, it was never over 8psi difference), maybe i dont really grasp how blowby works vs these tests or something....

Any ideas?

 

 

 

 

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Why have you left the pcv valve hole unblocked? Where is the catch can vented to - to turbo intake or to atmosphere? Rear "vent " to crankcase could be useless or worse - conducting pressure to the top. Why did your turbo seals blow? Oil temps seem excessive.  What did your tune look like esp AFRs and did you measure EGTs?

Lopin18 Contributor

Lopin18

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PCV was unintentionally ignored, facing the first event it was all quick. Its going to be directed to the catch can now.

Catch can is vented to atmosfere. Has a bottom fitting to return oil to pan. I thought the rear vent or drain, wouldnt really hurt anything, whats the generan consensus on it right now?

Turbo seals, old holset turbo, used exhaust wheel, i think its out of balance, i keep repairing it every 2 events. Now i bought a new chra to replace the whole thing. I have an oil restrictor on it, but its pretty big, it has a 4mm hole or bigger.

Oil temps were indeed sky high, it was a small track, 2nd gear, it was intense and the engine was heating up quite a bit.

AFRs are rich, we run around 11.6 - 12  on boost, 100 octane fuel. no EGT right now. im switching from a Z32 chiped ECU to an Ecumaster emu ecu.

Apart from all these small things that may add up to big issues. I cant seem to put my finger on the difference between the good results on leakdown etc vs the blowby or smoke im seeing from the valve cover. I keep hearing that the Mobil 1 oil sold in my country is really bad, noone uses it, but i cant imagine that its so bad that it would cook itself and smoke so much. sounds farfetched.

Ill correct the pcv valve hole, new turbo, gotta ask around about the turbo oil restrictor. Retuning soon on the new ecu. using knock and a bunch of new sensors to take care of the engine.

Just have to figure out this smoke thing. Im almost opening up the engine and rechecking everything. Its not a lot of work for me.

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