Lsx Twincharged pcv and backfiring in search of help!
01-09-2016, 12:46 PM
#21
If you move to point B, then you are just exhaust scavenging, and that is pretty much all you need other than a clean air inlet. You will still have oil vapors in the exhaust, even if rings etc are sealed well which can condense in you mufflers etc. maybe smoke, Not ideal to me.
I also want to point out that off boost, you have an intake manifold side PCV valve sucking up crankcase gasses into the head as well (see the picture). Everyone loves to install catch cans on the turbo side but neglects the intake manifold side completely, as if somehow it magically won't ever pull up any oil vapors.
That brings me to the next point. I understand during boost you may/will draw air from the crankcase. (not ideal either for same reason oil vapors). You still need a clean air source to replace the air you are extracting. I don't see that in your drawing.
Naturally Aspirated
Dyno Test Results
Without Vacuum Pump With Vacuum Pump
762ft lb@5100 772ft lb@5100
865hp@6700 890hp@ 6800
Source: http://www.strokerengine.com/vacuumpump.html
Note there is no "Fresh air source" that would defeat the purpose of trying so hard to depressurize the crankcase
more discussion
http://www.performanceboats.com/gn7-...um-pump-3.html
Originally Posted by GearHead
Vacuum is good and it helps keep the boat and/or car stay cleaner. I believe Bob and Bob have covered the subject pretty well. If one looks back at the Grumpy Jenkins study, he said one of the best performing pans was one with a large box style sump to let the oil sling away from the crankshaft. I have used this theory in several competition eliminator engines that mandated wet sump pans with good outcome. Now as has been mentioned, the dry sump has better oil control, but turning all those pump stages does not come without some power losses due to turning the pump.
Dry sump is best all around in oil control and the amount of vacuum one can pull. It is generally worth 40 to 70 HP on a decent machine. Comparing with a bad design it can be worth more. One can pull 20+ inches of vacuum as you are just pulling against atmosphere.
A big wet sump pan and vacuum pump are much cheaper. However one cannot pull the same amount of vacuum as the dry sump because in the wet sump you are pulling against the oil pump and too much vacuum can cause oil pump cavitation.... aereate the oil and damage bearings and crankshaft. With a better oil pump, the more vacuum one can run. Typically I have kept the vacuum to a maximum of 13" in a wet sump. However, the first 5 to 8 inches have the largest gain. As mentioned, oil pan and ring drag do affect the actual power, but pretty well one can see a 20 to 40 hp gain with just the vacuum pump and generally more in the 10 hp range with an evac system.
Dry sump is best all around in oil control and the amount of vacuum one can pull. It is generally worth 40 to 70 HP on a decent machine. Comparing with a bad design it can be worth more. One can pull 20+ inches of vacuum as you are just pulling against atmosphere.
A big wet sump pan and vacuum pump are much cheaper. However one cannot pull the same amount of vacuum as the dry sump because in the wet sump you are pulling against the oil pump and too much vacuum can cause oil pump cavitation.... aereate the oil and damage bearings and crankshaft. With a better oil pump, the more vacuum one can run. Typically I have kept the vacuum to a maximum of 13" in a wet sump. However, the first 5 to 8 inches have the largest gain. As mentioned, oil pan and ring drag do affect the actual power, but pretty well one can see a 20 to 40 hp gain with just the vacuum pump and generally more in the 10 hp range with an evac system.
Lastly as I mentioned, oil vapors due exist even in tight motors. There is no such thing as 100% sealed. Therefore, because I don't want oil going through my turbo, IC, intake valves etc, and my mufflers, or car to smoke, I think it's a good practice to use a catch can. Dont agree its a bandaid, although it could be used that way too. The volume of the can is negligible relative to the crankcase in my mind.
Gas state molecules, that which the pcv system craves, will not stop in a catch can because they are gasses.
I made a more detailed post about this exact situation, here
http://zilvia.net/f/showpost.php?p=5736274&postcount=4
Last edited by kingtal0n; 01-09-2016 at 12:56 PM.
