andrew_lally Posted June 11, 2006 Posted June 11, 2006 has anyone else experienced a slight trace of oil venting from dump valve??? no back pressure!!!... dosent smoke!!! oil levels all correct!!! any ideas anyone???....any help/advice would be greatly apprecited!!! cheers regards andy....
the squiggle Posted June 11, 2006 Posted June 11, 2006 Vent the breathers to atmos as the induction is pulling in oil from the crank/cam breathers under rapid accel. The 2 pipes going into the induction just at the 90degree inlet to the turbo are the ones to vent to atmosphere
andrew_lally Posted June 11, 2006 Author Posted June 11, 2006 sweet...ordered a catch tank mate!! cheers squirrel regards andy
the squiggle Posted June 11, 2006 Posted June 11, 2006 Probably find the inside of your intercooler and pipework will have a coating of oil.
st3ph3n Posted June 11, 2006 Posted June 11, 2006 For those of us without a degree in japanese car mechanics, but with an appetite to know everything could you explain the benefits of the catch can, and do the cars come with one as standard?
the squiggle Posted June 11, 2006 Posted June 11, 2006 Under hard accel the oil in the sump gets thrown backwards and up into the crank breather which in turn is being sooked into the combustion chamber and being burnt The catch can catches the oil before it gets sucked into your induction No catch can fitted as std Oil getting into your induction will lower the octane rating of your fuel and could bring on DET which is a very bad thing.
st3ph3n Posted June 11, 2006 Posted June 11, 2006 Cheers Grant. They're quite inexpensive items, might consider one as a safety measure when/if I can get the funds together for stage 2 of my project.
drb5 Posted June 11, 2006 Posted June 11, 2006 I have a used, but very clean, Helix catch can for sale, if anyones interested. £25 delivered.
coulty Posted June 12, 2006 Posted June 12, 2006 Under hard accel the oil in the sump gets thrown backwards and up into the crank breather which in turn is being sooked into the combustion chamber and being burnt The catch can catches the oil before it gets sucked into your induction No catch can fitted as std Oil getting into your induction will lower the octane rating of your fuel and could bring on DET which is a very bad thing. Don't forget that the cam breathers also vent. These run from either head to a t-piece that enters the inlet tract next to the crank breather.
MY94 Posted June 12, 2006 Posted June 12, 2006 The original PCV (Positive Crankcase Ventilation)system does indeed do some good for the engine by ensuring the corrosive gasses are removed from the crankcase and replaced by fresh filtered air. The Subaru system has two main phases depending on manifold pressure/vacuum. Under manifold vacuum conditions (probably 99% of the engines life) there is a non return valve under the throttle body, which allows the 'blow by' vapours to be drawn into the manifold. The vapours are replaced from the vents on the cam covers, supplied from the inlet duct. This provides the circulation of air through the engine, prevents condensation, oil contamination and internal corrosion. This is indeed a good thing and there is a strong case to retain this system if the car is a daily driver. Under positive manifold boost conditions, the non return valve under the throttle body closes and the hot 'blow by' gasses (Note - 'blow by' tends to be a cool vapour at low power but a hot gas at high power) are re-routed via a 't' piece to the intake duct for reconsumption by the engine. The cam cover vents may also vent out during this phase. This is where you can get oil suspended in the gasses finding its way into the induction system......this is a bad thing ! The oil coats the intercooler, reducing efficiency and causes premature det due to lowering the octane of the fuel. It is possible to 'catch' the suspended oil in a 'catch can' This is a reservoir deigned to reduce the velocity of the gasses, allowing the oil to fall out of suspension. The oil collects in the bottom of the can and the oil free gasses carry on to be either reconsumed by the engine or vented to atmosphere. The catch can will ideally intercept all 3 vent lines although the main culprit on the Subaru would appear to be the central crankcase vent. The return of gasses from the catch can is also the subject of some debate. If the gasses are reintroduced to the intake system then you are asking the engine to burn an oxygen free mix ! ie you are reducing slightly the amount of oxygen fed into the engine, this can only mean less power. I personally prefer to vent to atmosphere and block off the return to the intake system. There are concerns that this is not very 'green' however the vented gasses are just of the same constitution as your exhaust gasses (assuming you have a decat exhaust) Taken from ANDY F'S WEB SITE!!!
scoobymark Posted June 17, 2006 Posted June 17, 2006 The original PCV (Positive Crankcase Ventilation)system does indeed do some good for the engine by ensuring the corrosive gasses are removed from the crankcase and replaced by fresh filtered air. The Subaru system has two main phases depending on manifold pressure/vacuum. Under manifold vacuum conditions (probably 99% of the engines life) there is a non return valve under the throttle body, which allows the 'blow by' vapours to be drawn into the manifold. The vapours are replaced from the vents on the cam covers, supplied from the inlet duct. This provides the circulation of air through the engine, prevents condensation, oil contamination and internal corrosion. This is indeed a good thing and there is a strong case to retain this system if the car is a daily driver. Under positive manifold boost conditions, the non return valve under the throttle body closes and the hot 'blow by' gasses (Note - 'blow by' tends to be a cool vapour at low power but a hot gas at high power) are re-routed via a 't' piece to the intake duct for reconsumption by the engine. The cam cover vents may also vent out during this phase. This is where you can get oil suspended in the gasses finding its way into the induction system......this is a bad thing ! The oil coats the intercooler, reducing efficiency and causes premature det due to lowering the octane of the fuel. It is possible to 'catch' the suspended oil in a 'catch can' This is a reservoir deigned to reduce the velocity of the gasses, allowing the oil to fall out of suspension. The oil collects in the bottom of the can and the oil free gasses carry on to be either reconsumed by the engine or vented to atmosphere. The catch can will ideally intercept all 3 vent lines although the main culprit on the Subaru would appear to be the central crankcase vent. The return of gasses from the catch can is also the subject of some debate. If the gasses are reintroduced to the intake system then you are asking the engine to burn an oxygen free mix ! ie you are reducing slightly the amount of oxygen fed into the engine, this can only mean less power. I personally prefer to vent to atmosphere and block off the return to the intake system. There are concerns that this is not very 'green' however the vented gasses are just of the same constitution as your exhaust gasses (assuming you have a decat exhaust) Taken from ANDY F'S WEB SITE!!! Wow way too technical for me[*-)] I have a Bailley DV12 with the return pipe blocked off, which is depositing an oily substance, don't know how much, but more importantly in simple terms is this healthy or not?
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