Super small PCV vents ??
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Super small PCV vents ??
When I had my valve covers off, I could not believe how small the PCV vents are....Basically the two main vents on the covers may connect to a 3/8" hose, but the actual hole on the inside of the cover is close to the size of a paperclip.
Have folks drilled these out to get better breathing and more hp ?
There is the one 3/4" port on the driver side, I am just baffled as to why the engineers did not make the other ports bigger.....
Curious as to what others have done and the benefits....I know from racing, this can be an easy way to free up a few more hp too....
Have folks drilled these out to get better breathing and more hp ?
There is the one 3/4" port on the driver side, I am just baffled as to why the engineers did not make the other ports bigger.....
Curious as to what others have done and the benefits....I know from racing, this can be an easy way to free up a few more hp too....
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From: seattle
1990 300ce supercharged and intercooled
There is no PVC valve. So the small orifices are to regulate vacuum in the crankcase. The large hose is for at high load. If you want to add a vacuum pump or something then you would add it to the large hose on the left bank. If you drill out the small holes you would just end up with a large vacuum leak and to much vacuum on the crankcase and burn a lot of oil etc.
But honestly there is sufficient crankcase vacuum already.
But honestly there is sufficient crankcase vacuum already.
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There is no PVC valve. So the small orifices are to regulate vacuum in the crankcase. The large hose is for at high load. If you want to add a vacuum pump or something then you would add it to the large hose on the left bank. If you drill out the small holes you would just end up with a large vacuum leak and to much vacuum on the crankcase and burn a lot of oil etc.
But honestly there is sufficient crankcase vacuum already.
But honestly there is sufficient crankcase vacuum already.
I know many in the Japanese and American performance scene add all sorts of evacuation and even pumps and see 10+ hp gains. I was surprised folks are not talking about this more with the e55 platform.
Here is some helpful reading for some : http://forum.diyefi.org/viewtopic.php?f=24&t=357
Last edited by cij911; Nov 23, 2012 at 04:41 PM.
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From: seattle
1990 300ce supercharged and intercooled
The two small restricted vents are only for when the intake is under high vacuum like idle or low part load. The large hose is for under high load. As mentioned you could measure crankcase pressure. Easy to do, tap and oil cap and put a fitting in there to hook a pressure gauge up to. I you have high crankcase pressure then you could address it. I think that you will find that the stock setup is pretty good.
As far as one side or the other on the valve cover goes it does not matter as the engine can breathe from one side to the other. You do not need to vent each side separately.
As far as one side or the other on the valve cover goes it does not matter as the engine can breathe from one side to the other. You do not need to vent each side separately.
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I have never heard of a partial load and full load vent, but you are correct...
So how do the gases get to just the drivers side and if this is correct, why would there be a partial load vent on the passenger side ?
So how do the gases get to just the drivers side and if this is correct, why would there be a partial load vent on the passenger side ?
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From: Puerto Rico
2005 E55 AMG
You are looking at this the wrong way. The gasses build up in the crank case and heads. Since it's positive pressure it will fine the path of least resistance to escape. Even if one side was vented and the other not it would still relieve pressure from all areas.
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Dirt Scooters
Exactly. For my new build i had -12 bungs welded on both valve covers at the highest point of the valve covers and will vent both 3/4 lines into a catch can. The vacuum pump idea is great but just not on a street car.
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E55
When I had my valve covers off, I could not believe how small the PCV vents are....Basically the two main vents on the covers may connect to a 3/8" hose, but the actual hole on the inside of the cover is close to the size of a paperclip.
Have folks drilled these out to get better breathing and more hp ?
There is the one 3/4" port on the driver side, I am just baffled as to why the engineers did not make the other ports bigger.....
Curious as to what others have done and the benefits....I know from racing, this can be an easy way to free up a few more hp too....
Have folks drilled these out to get better breathing and more hp ?
There is the one 3/4" port on the driver side, I am just baffled as to why the engineers did not make the other ports bigger.....
Curious as to what others have done and the benefits....I know from racing, this can be an easy way to free up a few more hp too....
It's a pretty simple design. The (pvc) throttle body lines create a constant draw to pull fresh air into the crankcase and evacuate the caustic gases through the valvecovers. The 3/4 line has two functions; a) supply fresh/filered air to the crankcase while under vacuum, b) act as a vent if crankcase pressure increase beyond atmospheric pressure. It also acts as a good tell if an engine has blowby issues.
Under full throttle high rpm, I am also guessing there is Bernoulli effect on both the 3/4 fitting and the 3/8 fitting at the throttle body alleviating the build up of any positive pressure in the crankcase.
In case you are pondering it, you could not increase the size of the orifices in the valve covers without compromising the ability of the throttle body to maintain a low idle. It would definitely set a code.
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OK, I understand why technically one 3/4" port will suffice, but my question was why the two different sizes ( 2 small - low load ports & 1 large - high load port).
e55 addressed my point, and apparently has 2 - 12AN lines - should be great. I know a few others have as well, I am just wondering why it is not as common as with other platforms.
lowprofile - why would enlarging the pinhole on the valve cover to say 3/8" (to match the exit diameter) throw codes with the ECU? Where do the low load ports connect to (I can't see, but it looks like somewhere under the throttle body) ?
e55 addressed my point, and apparently has 2 - 12AN lines - should be great. I know a few others have as well, I am just wondering why it is not as common as with other platforms.
lowprofile - why would enlarging the pinhole on the valve cover to say 3/8" (to match the exit diameter) throw codes with the ECU? Where do the low load ports connect to (I can't see, but it looks like somewhere under the throttle body) ?
Last edited by cij911; Nov 23, 2012 at 11:37 PM.
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. Thanks guys!
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E55
OK, I understand why technically one 3/4" port will suffice, but my question was why the two different sizes ( 2 small - low load ports & 1 large - high load port).
e55 addressed my point, and apparently has 2 - 12AN lines - should be great. I know a few others have as well, I am just wondering why it is not as common as with other platforms.
lowprofile - why would enlarging the pinhole on the valve cover to say 3/8" (to match the exit diameter) throw codes with the ECU? Where do the low load ports connect to (I can't see, but it looks like somewhere under the throttle body) ?
e55 addressed my point, and apparently has 2 - 12AN lines - should be great. I know a few others have as well, I am just wondering why it is not as common as with other platforms.
lowprofile - why would enlarging the pinhole on the valve cover to say 3/8" (to match the exit diameter) throw codes with the ECU? Where do the low load ports connect to (I can't see, but it looks like somewhere under the throttle body) ?
