Zraced... Posted March 24, 2006 Share Posted March 24, 2006 I did a search on the forum, but found only V8 help. I have a monster turbo on my L28 and am boosting up to 15psi. I was wondering if I am in danger of pressurizing the engine block? I have a stock vent pipe that runs from the block to the intake manifold. If I boost to high will this pressurize the motor block? should I put a oneway valve on this hose to prevent flow back? Or is this not even a problem? My valve cover has a breather so that is not an issue up there. Thanks, zraced Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted March 24, 2006 Share Posted March 24, 2006 good question...i was boosting 15 psi on a stock L28et w/ a t4, ms, 440 injectors...and so on. and every now and then i was getting to much crank pressure and after i let off the gas, the damn oil dipstick would come out and the oil would squirt through the hood vent and onto the windshield. i've tried running pcv valve, vent breathers, everything and nothing seems to help. this motor was a perfect 150 psi compression across the board when i swapped it in and now compression is crap in 2 cylinders and dropping in the others slowly. i'm just going another motor in a lucky cause hopefully soon. dunno what else to try. Quote Link to comment Share on other sites More sharing options...
Zraced... Posted March 25, 2006 Author Share Posted March 25, 2006 I wonder if I should put a breather in the side of the motor with a pcv and cap the stock pipe that runs to the intake on the bottom. Just a thought as long as I don't get an oil leak...then maybe a catch can. Quote Link to comment Share on other sites More sharing options...
jeffp Posted March 25, 2006 Share Posted March 25, 2006 NOT GOOD! you broke your ring lands. Pressure in the crank case is a very good indication of a broken piston, then if you are losing compression, well the pistons are done. DETONATION was your problem. I just replaced my pistons for that very same reason, it only cost 3000.00 for new pistons and a refresh on the head. Not to fun. Quote Link to comment Share on other sites More sharing options...
Zraced... Posted March 25, 2006 Author Share Posted March 25, 2006 good question...i was boosting 15 psi on a stock L28et w/ a t4, ms, 440 injectors...and so on. and every now and then i was getting to much crank pressure and after i let off the gas, the damn oil dipstick would come out and the oil would squirt through the hood vent and onto the windshield. i've tried running pcv valve, vent breathers, everything and nothing seems to help. this motor was a perfect 150 psi compression across the board when i swapped it in and now compression is crap in 2 cylinders and dropping in the others slowly. i'm just going another motor in a lucky cause hopefully soon. dunno what else to try. Thats a massive oil leak...you must have heard popping from detonation to ruin the rings right? Would crankcase pressure ruin your rings? I think I'll hook up that vent hose/pcv ASAP to the side of my block before I run up too 15psi again. Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted March 25, 2006 Share Posted March 25, 2006 i always ran the block breather open and the valve cover open or with a breather... never had a problem. mike Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted March 26, 2006 Share Posted March 26, 2006 I got bored today, and decided to make a PCV evacuation system... similar to the stock setup I didn't want to drill and tap a hole in the intake manifold, so I did it the easy, cheap and effective way.. With the turbo, and N42 intake manifold, the PCV valve hits the turbo outlet, so I had to plug it up with a large bolt.. soo I put a filter on the end of the crank tube... since the oil and gas blow by blows OUT of the crankcase/block the filter would become clogged, and when this happened, strange things would occur.. the clogged blow by, caused sooo much high pressure build up in the crankcase/block, the turbocharger oil drain would not even drain the oil, because the high pressure was keeping the oil in the line. This would result in the oil to leak out of the turbo seals, and drip into the exhuast, which would smoke really really really bad. I then ran it open with no filter or anything, but I feared on a dirty or wet condition, water would enter the crankcase and contaminate the oil. SOO.. I attached clear hose from Home Depot to the crankcase PCV outlet, and put the open end behind the brake master cylinder and brake heat shield so no dirt would enter it Well.. with the PCV and nasty blowby gases pointed at the firewall, and the old rubber grommets I had, when I rolled the window down the high pressure in the engine bay would flow into the cockpit/cabin and create a vacuum.. ****, now I am smelling all this nasty *** blow by... I decided to buy the largest PCV valve I could at Checker Auto Parts, and attached a 3/8" hose to the intake manifold... obviously since it's smoothed and cleaned up, I TEE'd off the blow off valve vacuum source, and voila!! Magic! I noticed the engine seems to run a weeee bit smoother, and the RPMS are steadier... (the vacuum creates a better seal between the pistons rings and crankcase) here are the pics Notice the tube from under the intake manifold to the crankcase hole, and the shiney silver filter?? well that didnt work well NOW here is my ghetto setup =) Quote Link to comment Share on other sites More sharing options...
AK-Z Posted March 26, 2006 Share Posted March 26, 2006 would it be better to hook up the pvc from the crank to somewhere in the plumbing before the turbo (not directly). Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 27, 2006 Share Posted March 27, 2006 The stock setup in the car is VERY good, a bit TOO good actually! Under boost, the crankcase should be evacuated with the restriction the filter causes before the turbo, under vacuum the stock PCV can be restricted to .080 or .063" orifice to prevent too high a vacuum acting on the crankcase and sucking oil up into the inlet. Adding a supplementary breather box is a good idea, but as long as your rings are intact, the crankcase should never be more than -4" Water Column of pressure. That is more than enough to evacuate everything you want. Quote Link to comment Share on other sites More sharing options...
Zraced... Posted March 28, 2006 Author Share Posted March 28, 2006 I installed a PCV inline to the intake from the side of the motor. This should take care of any PSI problems. I have a breather on the valve cover line. Quote Link to comment Share on other sites More sharing options...
zbuild Posted March 28, 2006 Share Posted March 28, 2006 I run both my block breather and my tappet cover breather to a catch can and at the bottom of the catch can Ive got a drain with a one-way valve back into the sump. At the top of the catch can is a series of filtered holes that let the can breath to the atmosphere. I did this because I heard that if you use a PVC valve it can draw oil vapour back into your engine which can cause detonation in a highly boosted engine. I run 15psi & 17psi with a TO4. cheers - Simon Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted March 28, 2006 Share Posted March 28, 2006 I run both my block breather and my tappet cover breather to a catch can and at the bottom of the catch can Ive got a drain with a one-way valve back into the sump. At the top of the catch can is a series of filtered holes that let the can breath to the atmosphere.I did this because I heard that if you use a PVC valve it can draw oil vapour back into your engine which can cause detonation in a highly boosted engine. I run 15psi & 17psi with a TO4. cheers - Simon u have pic on how your catch can is setup and everything? i have a catch can available if i decide to run 1. Quote Link to comment Share on other sites More sharing options...
CarJway Posted March 28, 2006 Share Posted March 28, 2006 I posted this in another thread concerning PCV issues. AK-Z, I think that is ideal; that is why I am going to try something like this. Of course I would restrict the amount of air being sucked through the system, But this gives a great picture and general idea. (one would go to the valve covers and another to the Crank-case vent) Quote Link to comment Share on other sites More sharing options...
zbuild Posted March 28, 2006 Share Posted March 28, 2006 Gidday 280zforce if Ive done it right there are 2 pics, the working bits of the breather are a bit hard to see, but at the bottom front corner of the tank are 2 pipes, one goes to the return valve (the second pic) and the other goes to the breather from the block. inside the top half of the tank is a cage holding stainless steel wool to separate out the oil vapour which then runs back down to the sump. cheers - Simon Quote Link to comment Share on other sites More sharing options...
510six Posted April 6, 2006 Share Posted April 6, 2006 http://www.turbophile.com/technical/diy_catch_can.html This is a really good article on how to make an air/oil seperator. http://pg.photos.yahoo.com/ph/sss510six/detail?.dir=63ef&.dnm=b8b6.jpg&.src=ph This is a pic of my air/oil seperator a Mazda diesel fuel filter is used as the catch can and a return line is run to the sump, it works great. Quote Link to comment Share on other sites More sharing options...
Guest norm[T12SDSUD] Posted April 7, 2006 Share Posted April 7, 2006 At the track you will see guys running a breather hose from the valve cover to a small pipe welded to the exhaust collector. Apparently the high flowing exhaust does a good job at creating a vacuum and sucking out the air thus reducing pressure buildup in the crankcase. Later,Norm Quote Link to comment Share on other sites More sharing options...
Silent Posted April 7, 2006 Share Posted April 7, 2006 ']At the track you will see guys running a breather hose from the valve cover to a small pipe welded to the exhaust collector. Apparently the high flowing exhaust does a good job at creating a vacuum and sucking out the air thus reducing pressure buildup in the crankcase. Later' date='Norm[/quote'] thats what i plan on doing as well. simple science ordeal really. i think it would work on a turbo car, it would also create more vacuum, due to the air being forced out at a higher velocity. maybe t the line off to a vacuum gauge to monitor it? just an idea. i ran into this problem on my gsx, never really got it solved. total seal rings, o-ringed head and block, so it was sealed. but would get really pissy about 28 psi and barf the dipstick and cover everything in oil. my guess was the rings never sealed. so there has to be something. if it was there from the factory, there has to be a reason why it was engineered like that. but i seriously doubt nissan ever could see 400 rwhp on stock parts and expect that factory evac to work right Quote Link to comment Share on other sites More sharing options...
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