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Today I finally got around to doing my janky mod to the oil filler cap. The fitting is sealed with silicone sealer and as airtight as I could make it. I plumbed into my boost gauge as it was already there. Engine off but ignition on gauge sat at zero as you'd expect. Start engine it went to vacuum just below zero. Driving normally gauge moves a few notches below zero. putting foot down and making boost the needle goes further into vacuum. I'd say it went no further than about -0.2 bar (at no time did the crank case go into positive pressure)
I personally feel this shows my PCV and general breather system is operating as intended?
I also think that’s a reasonably promising result to rule blowby out as a possible issue.
I suppose the next logical step is the oil pump? Could the pressure relief valve not be operating as intended? Or could it be worth dropping from 5w-40 to 5w-30?
Being a hatchback STi I believe these all came with 11mm oil pumps. The engine was replaced by Subaru under warranty, so I’ve no reason to assume they would use anything other than standard parts.
Oil pressure gauge next then?
the oil pressure lights on these are as accurate as a chocolate fireguard.
Today I finally got around to doing my janky mod to the oil filler cap. The fitting is sealed with silicone sealer and as airtight as I could make it. I plumbed into my boost gauge as it was already there. Engine off but ignition on gauge sat at zero as you'd expect. Start engine it went to vacuum just below zero. Driving normally gauge moves a few notches below zero. putting foot down and making boost the needle goes further into vacuum. I'd say it went no further than about -0.2 bar (at no time did the crank case go into positive pressure)
I personally feel this shows my PCV and general breather system is operating as intended?
I also think that’s a reasonably promising result to rule blowby out as a possible issue.
I suppose the next logical step is the oil pump? Could the pressure relief valve not be operating as intended? Or could it be worth dropping from 5w-40 to 5w-30?
Being a hatchback STi I believe these all came with 11mm oil pumps. The engine was replaced by Subaru under warranty, so I’ve no reason to assume they would use anything other than standard parts.
Oil pressure gauge next then?
the oil pressure lights on these are as accurate as a chocolate fireguard.
Also been runing one for a while. I posted on a previous post I also now have an oil pressure gauge. On a cold start it will go to around 6 to 7 BAR then pressure reducing as the oil warms up. When warm idle shows about 2 BAR. When driving it will hover around 5 to 6 BAR at varying loads and revs.
As far as I can tell, this is also in about the ballpark?
I agree. But my thinking is thicker oil will remain thicker at operating temp so added pressure!?
I ran a VF43 on a Hawk WRX with 5w40 Shell Ultra for years without any problems. I struggle to beleive this setup is so drastically different to cause me issues. But here we are.
Did you ever get this sorted?
I've an 08 STI hatchback with a similar issue. It's early days but my oil consumption seems to have increased. The inside of the turbo up pipe is a nice sandy colour. The centre section of the exhaust is black and sooty.
My engine is almost standard, forged pistons, closed deck block, Grimspeed oil seperator, RCM sump baffle plate, new 12mm oil pump. The turbo has the oem 1.5mm oil restrictor. There's almost no oil inside the tmc which goes with the clean up pipe.
The engine was rebuilt about 3 years and 12,000 miles ago by Enginetuner in Plymouth. Thats when the CDB was done. They rebuilt the turbo at the same time.
I'm leaning towards turbo seal failure but it shouldn't happen this soon after a rebuild surely.
Did you ever get this sorted?
I've an 08 STI hatchback with a similar issue. It's early days but my oil consumption seems to have increased. The inside of the turbo up pipe is a nice sandy colour. The centre section of the exhaust is black and sooty.
My engine is almost standard, forged pistons, closed deck block, Grimspeed oil seperator, RCM sump baffle plate, new 12mm oil pump. The turbo has the oem 1.5mm oil restrictor. There's almost no oil inside the tmc which goes with the clean up pipe.
The engine was rebuilt about 3 years and 12,000 miles ago by Enginetuner in Plymouth. Thats when the CDB was done. They rebuilt the turbo at the same time.
I'm leaning towards turbo seal failure but it shouldn't happen this soon after a rebuild surely.
I'm not sure I'd ever be as bold to call it 'sorted'. I still have a spare built turbo sat in my garage, just in case.. In my case, the seals seemed to blow on the intake side and my intercooler would have a load of oil residue. But I suppose it is possible for them to blow on the exhaust side too!? But my previous post saying about the enhanced turbo, it seemed to cure itself. Maybe it was just an oil burp? I'm still running that same turbo nearly a year on with no issues.
I did however remove the grimmspeed AOS and revert to the stock breather system, I have not had (touch wood) any issues since the last episode. (although I do look in the mirror every time I start it for that puff of smoke)
When I removed the AOS, I also removed that oil filter inside the banjo bolt for the turbo and AVCS feed. It could have been the bolt causing a restriction and oil starvation? I believe the general consensus is to remove that little filter. Mine didn't look very clogged at all tbh. But I'd gone to the effort so removed it anyway.
Maybe remove the AOS and see if it helps? My only other suggestion would be to also replace the PCV. But it sounds as though your issue is a bit different to mine, as no oil in the intercooler.
I think I was unlucky and maybe had a bad batch of Mellett turbo cores. To go through three of them is a bit questionable imo.
Just dont redirect the AOS back to intake. Theyre know for occasionally getting a gulp of oil back into intake on hard use, plus redirecting it away means you only ever get clean air into your intake
i ran mine into an overflow/catch can which you can just see behind the coolant overfill bottle (will see can i dig out better pics) before catch can it just went into a 500ml soft drink bottle again with no issues!
Thasnks for the pictures. You'r engine looks very similar to mine. My AOS vents back into the original PCV setup. That may be something for me to check. Also redirecting the vent to a catch can. It's an easy test and could show a result.
You've given me some ideas anyway. Thanks.
01 April 2023, 10:28 PM
