Crankcase Pressure?
12-22-2010, 10:33 PM
#2
If you are utilizing a negative crank case ventalation system, you should see non to very minumal. My system is symply vented to atmospher, I have almost no crankcase pressure.
If you have alot of pressure, like a frieght train, then the rings are bad.
If you have alot of pressure, like a frieght train, then the rings are bad.
12-23-2010, 10:31 AM
#5
If it was bored incorectly then the rings will not seat in. Again can you describe the amount of crank case presure you are seeing? Describe the crank case vent system you have. Idle the engine and remove the oil fill cap, put a rag over it, is it sucking the rag in or blowing it out? Is it smaking out the file like a freight train or what? If it is then take it to the builder and make him stand behind it.
12-23-2010, 10:33 AM
#6
Wrong ring gap can do this, a ring in up side down can too. If it is bad enough you might see some oil fowling on the plugs. This can tell you wich hole is the issue. You can also run a leak down test or compresion test and that too will tell you something. Does it smoke out the exhaust, is it using oil? More details will help us diagnos the issue.
12-23-2010, 10:37 AM
#7
Also id the ring gaps are lined up. Improper ring break in can do this some times too. Crankcase pressure is usually ring related, in worst cae senerios, a cracked piston or a hole in the piston crown will do this as well. Rings are the most common cause. First you need to figure out if it is in fact bad. With no vacuum aplied to the crank case to evacuate the crank case there will be a little pressure. The is always a little combustion pressure that will escape past the ring into the crankcase. That is why you vent the crancase either threw the manifold or to atmousphere. So the first thing is to decide if there really is an issue.
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12-23-2010, 11:07 AM
#9
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I appreciate the help so dont worry about the spelling. Its done this since day one and there wasnt a 1k mile break in just 5 or so full heat cycles and 200 easy miles. Then straight to the dyno. Been fighting smoke out of the downpipe since day one, thats what got me thinking crankcase pressure was an issue. My drain wasnt the best from the get go but now its 100 times better after shop fixed it and with the engine running and drain going into bucket right at the same location where it would enter the oil pan it drains (so the drain works) and no smoke will come out of downpipe if you rev it up. But as soon as you hook oil return back up it would smoke. When the drain was off you could feel pressure @idle coming from crank, which is normal but I didnt know how much. The breather set-up was, pass valve cover to catch can, valley to catch can filtered to the atmosphere. Then I put a little filter on the driver side and didnt do anything, then tried a different valve cover with another big filter and helped but only when the filter was off. Anyways done some research and seen some get away with catch cans and other methods but then some have to go to pumps to fix the problem. Why is that some are different than others say at the same hp levels 900?
12-23-2010, 12:43 PM
#10
The difference can be as symple as the type of rings utilized as well as the finish on the hone work for the bores. There are basically three different finishes that are comanly used by the pros. A NA engine will have a differerent bore finish coursnes then a FI or Nitrous finish. Not all shops do this. Most shops just use the same finish for all engine types. This does not mean the finish is wrong. It is realy how annaul you want to be. They all will work just fine. The place I use for my machine work use does the three diferent finishes. The guy that owns the shop use to work for Chapparel Racing out of Midland Texas. they built nothing but race engines, Daytona engines, Indy engines, they were a very serious shop. So the people that worked there were tought to be annaul. Your crank case ventalation system sounds close to what I am running, basicaly venting it to the air with no help from the engine manifold vacuum. In this setup you will have more crank case pressure at idle then a stock car. It sounds like what you are telling me is you really are not having an issue with pushing oil out of gasket surfaces, or pushing valve cover gaskets out from under the cover. Your issue sounds like it is only aperent when you hook the drain from your turbo back into the crank case, and you are then getting a little smoke out the down pipe of the turbo. Is it like a smoke screen then or just a slight hint out the exhaust? I understand you feel air flowing out the port for the turbo drain, but that is really a bad place to "feel" for it at because depending on were your drain is located in the oil pan, you might be feeling the "windage" from the crank shaft spining. What side of the car is the drain back located and did you install it above or below the widage tray? What oil pan are you using? I would think due to the direction of crankshaft rotation, if you installed the drain back on the drivers side, there would be a greater chance of the windage pushing or slowing the flow of oil trying to come into the pan. The vents in the windage trey are facing the drivers side, so my thoughts are the oil being scraped from the air are thrown against the drivers side of the oil pan. This might be hindering the oil flowing back into the pan. The seal in the turbo is a mechanical seal, it does not take much pressure on the drain side to push oil threw the seal, and the seal does not work with the turbo not turning. It works better as the turbo speed increeses too. The exhaust back pressure in the exhaust pipe also helps to control the oil from coming threw the seal too. So if you only have a down pipe with no other exhaust, the pressure in the down pipe might not be enough to help the seal do its job.
Do your crank case vent filters show signs of blowby on them? I would think there would be oil stain running out of them if the pressure was too high. Do you have an oil drain on your catch can? Is it routed back to the crank case and if so do you run it open to the crank case all the time or do you have a valve in it to drain the can with?
If you have a spar oil fill cap you can drill and tap it were you can insert a nipple, then take a gauge and mesure the crank case pressure, preferably one that reads + and - in inches of water, not ounces of water but inches. It would be good to know exactly what the pressure is. Do not use the hoses going to your catch can. When you test this first test it with your ventalation system in service, then plug it some how,, and plug your filter on the valve cover, and take a mesurement. We can compare the two readings and get a good idea of how bad the crank case pressure is. This will help us determine if there is infact a crankcase pressure issue of if you might need to move your turbo oil drain some were else. Or if you just need to change up your vent system some. What size hoses are you using to your catch can?
Do your crank case vent filters show signs of blowby on them? I would think there would be oil stain running out of them if the pressure was too high. Do you have an oil drain on your catch can? Is it routed back to the crank case and if so do you run it open to the crank case all the time or do you have a valve in it to drain the can with?
If you have a spar oil fill cap you can drill and tap it were you can insert a nipple, then take a gauge and mesure the crank case pressure, preferably one that reads + and - in inches of water, not ounces of water but inches. It would be good to know exactly what the pressure is. Do not use the hoses going to your catch can. When you test this first test it with your ventalation system in service, then plug it some how,, and plug your filter on the valve cover, and take a mesurement. We can compare the two readings and get a good idea of how bad the crank case pressure is. This will help us determine if there is infact a crankcase pressure issue of if you might need to move your turbo oil drain some were else. Or if you just need to change up your vent system some. What size hoses are you using to your catch can?
12-23-2010, 02:57 PM
#12
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Yes its a stroker set-up and the drain at first once on the front of the pan but it was going straight up, now its on the driver side up as high as it can go. Once the car gets warm at idle it smokes like its on fire. I know the smoke is coming from turbo because Ive let it run open header and no smoke what so ever comes from the engine with the exhaust by passing the turbo.
12-23-2010, 03:42 PM
#14
Sounds like the issue is not in the engine. Sounds like you are getting oil coming out of the turbo to the exhaust downpipe. Now the question becomes is the seal in the turbo bad or do you still have an issue with the oil drain. Do you have a check valve in the oil feed line going to the turbo? On my rear mount I had a bad smoking issue too when I first installed the turbo. I ordered a check valve with a 1 psi pressure spring. What was happening is when you shut the engine off, there is still oil pressure that has to be bleed off. The oil would drain down out of the engine oil gaullies and into the turbo. Then the oil will leak past the oil seal (because the turbo is not turning) and into the down pipe. The check stops this from happening and it solved my problem. If you do not have one, you can order one from most any hardware store or NAPA, make sure the spring pressure is no more then 1 psi and that you install it in the correct direction. This would be a cheep check, I think the valve was less then 10 bucks.
12-23-2010, 04:21 PM
#15
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turbo was sent back and rebuilt to make sure everything was good on that end. Ive never thought about the check valve thing and oil still being pushed to turbo. For some reason when the car is off there is still a very small amount of pressure coming from somewhere. It will drip a veryyyyyyyyyyyyyy small amount for ever. You know a reason for that?
12-23-2010, 07:38 PM
#17
What do you mean drip? Dripping on the floor or you can hear fluid dripping into fluid inside the engine? If it is the sound, then yes, oil will drain into the oil pan for hours, and you can sometimes hear it. If you can hear fluid moving threw something, that could be the oil pressure bleeding into the turbo, and dripping into the exhaust down pipe. If you have AC still, you will hear the R134 gas equalizing in the system when the car is shut off (if it you were running the ac).
Does the smoking ever stop? How long do you have to run it to get it to stop?
Does the smoking ever stop? How long do you have to run it to get it to stop?
12-23-2010, 08:12 PM
#18
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its a -4 feed and no sounds of oil just when you take the feed line off the turbo it will continue to drip for ever it seems like. Ive actually fixed the problem or put a band aid on it which ever way you look at it, well its not smoking any more. Spent a lot more than I wanted but hey its fixed. Sorry to keep you going, I was just wanting to see other peoples opinions. To see if it was something I over looked or didnt know about. If I would have said problem fixed already in the op i wouldnt have got any replies.
12-23-2010, 08:39 PM
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As rpm rises so does the pressure thus not letting oil flow back into pan, backing it up into turbo and it has to go somewhere. Put a pump on it and no more smoking. I also have 65lbs of oil pressure at idle @ operating temp. which isnt helping but Ive talked to multiple guys that have that and they dont have any issues. My turbo is a low mount set-up also which doesnt give it much drop to build up speed to fight the pressure.
