Can anyone weigh in on crank case pressure at high RPM?
03-28-2022, 09:24 AM
#22
That seems pretty high at 17%. You may be in the early stages of the rings going. Also it is not all about ring seal either. The second piston ring is also used for oil control can be giving way and allowing for oil to pass by into the intake manifold. Then you just said the word nitrous and what are the details here? Take a look inside the manifold and see if it has a lot of oil in it. Given it is a single plane intake you might not see much or take a peak inside the intake ports. With us guys with low rise plastic intakes the oil can puddle in the bottom of them which will not be the case here.
03-28-2022, 12:43 PM
#23
TECH Addict
iTrader: (1)
I have vented many, many N/A engines to atmosphere without issue. No excessive oil collection in cans, ever (there’s always going to be a little oil in the bottom of the can, no matter what), and no mess. My 434 in my Chevelle is the same way. I avoid PCV setups unless it’s necessary for emissions, whenever possible. I don’t see the need from a performance standpoint, to allow the oil mist to re-enter the intake, if it’s avoidable. I’ve found that these LS engines make more crankcase windage than the previous SBC’s, and in my opinion, anything we can do to keep this out of the intake is a good thing…again speaking from a performance standpoint only. I don’t think that’s the issue here. Judging by the numbers in the other thread, and what’s going on here, I’d say there a ring seal issue or something similar. Almost sounds like the engine has way too much oil in it, but that would not cost 100ish hp.
03-28-2022, 06:52 PM
#24
And your not happy with how it works? The vacuum pump is worth a few ponies.
Im happy with how mine works, 1/2 inch of oil in bottom of can every month. No oil whatsoever in intake manifold. If for whatever reason i start my car i make sure i get it up to temp, that way i evaporate all the water so none ends up in the can... Did think about getting the gz pump, was just unsure how reliable they are seeing tho i daily my car. Once i see that cars with them on are getting 30-40k out of them, ill get one, until then ill stay with what i have
Im happy with how mine works, 1/2 inch of oil in bottom of can every month. No oil whatsoever in intake manifold. If for whatever reason i start my car i make sure i get it up to temp, that way i evaporate all the water so none ends up in the can... Did think about getting the gz pump, was just unsure how reliable they are seeing tho i daily my car. Once i see that cars with them on are getting 30-40k out of them, ill get one, until then ill stay with what i have
04-03-2022, 12:27 PM
#25
This opinion is not going to be popular, but it's okay.
Catch cans are a joke invented by the copy crowd. They are not intended for normal applications or to replace a evacuation system. Do they work? Sure. They catch residual oil vapor.
Plug off your differential vent and see what happens
.....and it's not a air pump.
The entire ICE works on pressure differential. Specifically with respect to this thread, the less pressure diffential above and below the rings, the less effective and efficient combustion is. That's why vacuum pumps make so much power in HP applications.
In a perfectly tuned, healthy engine can one omit the PCV system? Sure.
I don't ever expect my engine to be at it's healthiest without some sort of evacuation system. I usually use the GM 24505066 air pump, 95 Corvette
and GM 12117025 Plug along with the old-school exhaust scavenge system made popular by the Traco boys in the day, and that's what I plan for my current LS turbo build.
Catch cans are a joke invented by the copy crowd. They are not intended for normal applications or to replace a evacuation system. Do they work? Sure. They catch residual oil vapor.
Plug off your differential vent and see what happens
.....and it's not a air pump.The entire ICE works on pressure differential. Specifically with respect to this thread, the less pressure diffential above and below the rings, the less effective and efficient combustion is. That's why vacuum pumps make so much power in HP applications.
In a perfectly tuned, healthy engine can one omit the PCV system? Sure.
I don't ever expect my engine to be at it's healthiest without some sort of evacuation system. I usually use the GM 24505066 air pump, 95 Corvette
and GM 12117025 Plug along with the old-school exhaust scavenge system made popular by the Traco boys in the day, and that's what I plan for my current LS turbo build.
The following users liked this post:
G Atsma (04-03-2022)
04-03-2022, 04:23 PM
#26
TECH Resident
I dont think you can really call catch cans a joke! As well as oil, they catch water vapour. I for one would rather catch the oil/water than have it run thru the combustion events.
A catch can doesnt eleminate your evacuation system, its added to it , to remove those contaminates from entering your intake and being ingested by your engine
A catch can doesnt eleminate your evacuation system, its added to it , to remove those contaminates from entering your intake and being ingested by your engine
The following 2 users liked this post by Mickyinks:
Corona (04-03-2022), theunderlord (04-04-2022)
04-04-2022, 12:45 AM
#27
Okay, conducted a cylinder leak down test on a cold engine. Here are the results
#1 17%
#2 17%
#3 14%
#4 16%
#5 17%
#6 15%
#7 14%
#8 17%
also I should mention the piston rings are gapped for nitrous.
I would imagine on a warm/hot engine the 17% would be closer to 10-12%.
I should also add that I had to run a shorter (lengthwise) windage tray for clearance in the Holley Ls Swap oil pan.
Can crankcase windage cause excessive pressure??
#1 17%
#2 17%
#3 14%
#4 16%
#5 17%
#6 15%
#7 14%
#8 17%
also I should mention the piston rings are gapped for nitrous.
I would imagine on a warm/hot engine the 17% would be closer to 10-12%.
I should also add that I had to run a shorter (lengthwise) windage tray for clearance in the Holley Ls Swap oil pan.
Can crankcase windage cause excessive pressure??