Sometimes there will be smoke that smells kind of like oil burning off thats dark greyish in color that doesnt dissappear when it hits the air, it kind of stays in a smoke form and floats off with the wind.
I figured its my turbo cause it happens only at idle. I never get smoke when I drive. And it takes a couple of minutes at idle for this to happen when it sits idling, and sometimes it just wont happen at all. It comes and goes.
I had 2 previous SR's in a 240 I sold recently, and the last one did the same exact thing, but someone told me its most likely the turbo. So I figured thats what this is.....till:
I opened my oil cap when it was idling tonight after a hard run, and there was Pulsating air comming out the valve cover!!! What does this mean?
I have searched, and I found nothing that settles my stomach with this mystery
Air Pulsating Out Oil Cap & Smoke at idle Occasionally
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Nismo_Freak
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Taylor_Durdan
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Re: (Nismo_Freak)
the air coming out of your valve cover is known as blow-by. this is when pressure from the combustion chambers leaks past the piston rings and builds up in the crankcase. when you removed the oil cap, it provided it a place to escape.
now.. let me guess. do you have one of those little breather filters on one end of the port on your valve cover? that hose is essential for evecuating the pressure. the crank case ventilation system on turbo vehicles work like this:
looking at the motor; on the left side of the valve cover is a smaller black rubber hose that goes from a PCV valve to a small steel vent line hooked to your intake manifold. this provides suction of small pressure through the vavle cover at idle and vacuum situtations. once boost is acheived, the PCV valve shuts (its a one way valve) and that black line no longer sucks out pressure. afterall, if there wasnt a PCV valve there, then the manifold pressure would just fill the engine!
now, on the right side of the motor is the larger crank case vent sytem. there is a port on the back end of the motor that connects to a lerge black metal box. this is the factory oil seperator. it acts as a catch can so all the oil that gets sucked up, too, doenst make its way into your turbo and intake tract. that box connects to one side of the valve cover "T" fitting and the other side goes down to the intake of the turbo where the venturi effect draws out pressure and creates a vacuum in the line, thus sucking out the crankcase pressure under boosted applications.
what happens when you dont have the line going from the valve cover to the turbo intake, the pressure doesnt get sucked out. so the system is constantly under pressure and can only bleeds out what it can. this pressurises the area when the crank and rods live. that pressure pushes on the piston rings and prematuraly wears them out. then you have blowby. your combustion pressure leaks past and blows out where it can.
CORRECT
WRONG
notice how in the first picture, theres a hose going down towards the turbo? that is correct. notice in the second picture he has them both going to a new catch can, but isnt evecuating anything from it, he just has a filter? yeah thats not right. and he will ruin his motor shortly. to be proper, he would run a line from the catch can to either the inlet of his turbo, or you can acutally use your exh downpipe if you want (but you get alot of unecessary smoke)
hope i helped you learn a little something today
now.. let me guess. do you have one of those little breather filters on one end of the port on your valve cover? that hose is essential for evecuating the pressure. the crank case ventilation system on turbo vehicles work like this:
looking at the motor; on the left side of the valve cover is a smaller black rubber hose that goes from a PCV valve to a small steel vent line hooked to your intake manifold. this provides suction of small pressure through the vavle cover at idle and vacuum situtations. once boost is acheived, the PCV valve shuts (its a one way valve) and that black line no longer sucks out pressure. afterall, if there wasnt a PCV valve there, then the manifold pressure would just fill the engine!
now, on the right side of the motor is the larger crank case vent sytem. there is a port on the back end of the motor that connects to a lerge black metal box. this is the factory oil seperator. it acts as a catch can so all the oil that gets sucked up, too, doenst make its way into your turbo and intake tract. that box connects to one side of the valve cover "T" fitting and the other side goes down to the intake of the turbo where the venturi effect draws out pressure and creates a vacuum in the line, thus sucking out the crankcase pressure under boosted applications.
what happens when you dont have the line going from the valve cover to the turbo intake, the pressure doesnt get sucked out. so the system is constantly under pressure and can only bleeds out what it can. this pressurises the area when the crank and rods live. that pressure pushes on the piston rings and prematuraly wears them out. then you have blowby. your combustion pressure leaks past and blows out where it can.
CORRECT
WRONG
notice how in the first picture, theres a hose going down towards the turbo? that is correct. notice in the second picture he has them both going to a new catch can, but isnt evecuating anything from it, he just has a filter? yeah thats not right. and he will ruin his motor shortly. to be proper, he would run a line from the catch can to either the inlet of his turbo, or you can acutally use your exh downpipe if you want (but you get alot of unecessary smoke)
hope i helped you learn a little something today
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got2b240
- Posts: 475
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I do to have the stock catch can and intake line from that "T" on the valve cover hooked up like stock.
This is a Type-X S13 Blacktop. Its newer and I am supprised it has blow-by cause for stock boost she runs verry hard, compaired to the 2 other motors I had previously.
But can anyone open their oil cap for me and tell me if they get pulsating air out the top?
This is a Type-X S13 Blacktop. Its newer and I am supprised it has blow-by cause for stock boost she runs verry hard, compaired to the 2 other motors I had previously.
But can anyone open their oil cap for me and tell me if they get pulsating air out the top?
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Taylor_Durdan
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Re: (got2b240)
well, all motors will have that to a certain extent.. its bad when smoke blow out of it, too. you might need to replace your PCV valve.
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Lucian_rider
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- Car: Silvia S13 Fastback with SR20DET
Re: (got2b240)
What no one has mentioned is that pulsing air is normal as this is caused by the rise and fall of the pistons which moves air around the crankcase by the underside of the pistons somewhat like an air compressor or a two stroke engine.
Blow by adds to the volume of gases in the crankcase but would not be pulsing but a constant stream of gases that is trying to get out of the crankcase. Obviously blow by increases with the pressure of combustion and the rpm of the engine. High boost will create more leakage past the rings than low boost etc.
What your exact problem is however I am not certain, however a leak down test should show if you have excessive blow by caused by worn rings or a glazed/worn bore.
Chris
Blow by adds to the volume of gases in the crankcase but would not be pulsing but a constant stream of gases that is trying to get out of the crankcase. Obviously blow by increases with the pressure of combustion and the rpm of the engine. High boost will create more leakage past the rings than low boost etc.
What your exact problem is however I am not certain, however a leak down test should show if you have excessive blow by caused by worn rings or a glazed/worn bore.
Chris
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S14owner95
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- Joined: Wed Jun 29, 2005 9:01 am
- Car: 95 240SX, S14SR, JIC Suspension, Mad Tyte Stickers
Re: (Taylor_Durdan)
If you use the Exh, wouldn't that create a pressure instead of a vacuum therefore creating more pressure into the engine and an exponential rate?Taylor_Durdan wrote:...or you can acutally use your exh downpipe if you want (but you get alot of unecessary smoke)
If you use a catch can on the left side of the motor, or just dump it off, the pressure is able to be relesed at any rate it chooses to do so..
Running the hose back into the turbo could possibly be bad for it.. think of the compressor wheel spinning at X amount of RPM and then blow by, or vaporized oil slams into the fins, goes through the turbo, and down through the intercooler.. at which point in time, somewhere in that line, it's going to gather somewhere, therefore disrupting airflow, and possibly creating a stock of oil in the bottom of the intercooler (hence the reason some intercoolers have drains)
The motor itself creates a vacuum, so it sucks through the breather valve, and is vented through the other side of the valve cover..
Maybe I'm wrong?
Re: (S14owner95)
If you don't run vacuum to the valve cover it is only going to vent when pressure becomes high enough to push it out side of the hole through the breather.
This creates unnecissary pressure buildup undernieth the pistons, and results in an increase in blowby. Over time this wears out the compression rings, and the problem just gets continually worse.
By hooking it up to a vacuum source (like the exhaust, or intake) you relieve the extra pressure and aid in sucking out blowby vapors.
If done correctly (slashcut facing AWAY from incoming exhaust flow) it can create between .25 - 4psi of vacuum depending on RPM.
The intake seems to do about the same done by my tests. Of cource if you do hook it to the intake, I would run a catchcan in between to catch the oil vapors.
This creates unnecissary pressure buildup undernieth the pistons, and results in an increase in blowby. Over time this wears out the compression rings, and the problem just gets continually worse.
By hooking it up to a vacuum source (like the exhaust, or intake) you relieve the extra pressure and aid in sucking out blowby vapors.
If done correctly (slashcut facing AWAY from incoming exhaust flow) it can create between .25 - 4psi of vacuum depending on RPM.
The intake seems to do about the same done by my tests. Of cource if you do hook it to the intake, I would run a catchcan in between to catch the oil vapors.