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interested to see what you end up with.

my dart 427/turbo build has had 2 MM cans, one wild one pcv, for a couple years now. each connected to a valve cover with 10an hose.

under vacuum - the wild can would be the fresh air into the engine through one valve cover, the PCV can on the other valve cover was connected back to the intake.
then under boost - the pcv valve closed, they would both be open to atmosphere from each valve cover

connected to valley cover ended up with a lot of oil in the can, like full after 500miles a lot.

being turbo, there wasnt a good place to connect before the turbo, tried "suction" line from the MM PCV valve connected to the back of the intake but that still allowed a lot of oil back into the intake.

i ended up just taking the little disc out of the catch can breather and running them both open to atmosphere the whole time

no problems with RMS blown out, lots of street miles, 10.5+:1 comp, e85, ran s480 (800ish hp) to GT55 98mm (1500ish hp)
 

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interested to see what you end up with.
my dart 427/turbo build has had 2 MM cans, one wild one pcv, for a couple years now. each connected to a valve cover with 10an hose.
under vacuum - the wild can would be the fresh air into the engine through one valve cover, the PCV can on the other valve cover was connected back to the intake.
then under boost - the pcv valve closed, they would both be open to atmosphere from each valve cover
connected to valley cover ended up with a lot of oil in the can, like full after 500miles a lot.
being turbo, there wasnt a good place to connect before the turbo, tried "suction" line from the MM PCV valve connected to the back of the intake but that still allowed a lot of oil back into the intake.
i ended up just taking the little disc out of the catch can breather and running them both open to atmosphere the whole time
no problems with RMS blown out, lots of street miles, 10.5+:1 comp, e85, ran s480 (800ish hp) to GT55 98mm (1500ish hp)
Sounds like a cool build. With the two cans open vented, did you get much 'stank' especially at idle or low speed?
Were the cans positioned near the air filters in your set up?
 

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Sounds like a cool build. With the two cans open vented, did you get much 'stank' especially at idle or low speed?
Were the cans positioned near the air filters in your set up?
not really noticeable cruising around town wasnt bad, the only time it got stinky was after a longer cruise on the highway (15 mins or longer) and then stopped at the end of the offramp waiting for light or something.

cans no where near filter on front of turbo, one on passenger side firewall and other on brake booster bracket, both hoses 12-16" long
 

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not really noticeable cruising around town wasnt bad, the only time it got stinky was after a longer cruise on the highway (15 mins or longer) and then stopped at the end of the offramp waiting for light or something.

cans no where near filter on front of turbo, one on passenger side firewall and other on brake booster bracket, both hoses 12-16" long
Hmmmmm might just needs some pitchas...
 

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Sorry, calling BS on your claim. A MM Wild (which vents under positive pressure) should absolutely prevent the oil seal issues IF installed correctly, with the port and hose sizes needed for the build. That is the entire purpose, it seems, of the dude creating it (according to the site).
If you were using the proper setup on the can and you are still pressurizing the crankcase, it sounds like there is a problem with your build.
[There is no problem with my build. I know a bunch of guys getting rid of the mm can because of crank case pressure issues. A 3/8” hose is not big enough to support 1000+ hp builds. Call bs a vented can is what my build needed
 

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Hmmmmm might just needs some pitchas...
not a ctsv, so not much help probably lol.


current version has a VS 94/108, every things more compact, ac works a lot better and is needed for chiller, larger radiator
Automotive fuel system Hood Automotive tire Motor vehicle Automotive design


"max" effort was turbo forward headers, gt5533r thru the grill, smaller radiator,
Car Hood Motor vehicle Automotive design Automotive fuel system
 

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Discussion Starter · #69 ·
The port on the blower snout is 3/8” being the restriction in the system using a mm can it can only move so much air
The port on the blower snout isn't a restriction when discussing crank case pressure and the MM catch can...

Sent from my SM-G991U1 using Tapatalk
 

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The snout hose (which should get a boost check in it) is only in play as vacuum in the right conditions.
The RMS protection is provided by the dual -10 or bigger lines to the MMW which vents CC pressure through its filter.
It would seem that if you’re still having pressure in the CC, either the hoses or the filter is plugged or the can is full, or??
I don’t mean to start any arguments, it’s your build and I’d like to learn from it as I build mine.
If the MM is a problem I certainly want to know(!) and I wanna know why and how to fix it.
The can is meant to vent (blow off) positive pressure.
I’d really like to know why it isn’t working
 

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May I ask a question please. . .

Has anyone done any calculations, regarding how large any of these hoses need to be, versus flow determined to vent the crankcase, versus a given HP level?

Again, if we are pumping 1500 cfm on the top of the piston,
we are also pumping 1500 cfm on the bottom of the piston.
***That's your total potential windage for each engine rpm.

If you divide the above by 4. as each engine rpm has 4-Pistons moving 90° (4 * 90)= 360° you can zero in on what each piston contributes to the windage.

One of the things that would interest me, is;
How many square inches are the inter-bay vents, versus the square area of the pistons / bores.

Then one might be able to back into the / a useful number?

Since the B-15 lsX is warranted for 900 fwHP, that also gives you a number to use. 900 fwHP, means GM is assuming the engine is going to pump ~1350 CFM.

Then, what would be the assumed blow-by, given as a percentage of CFM, that the GM Engineers might have worked with?

Empirically, many have stated a number 10AN hose is required for engines with ~1000 fwHP.

What can a number 10AN hose flow?
To begin with; figure about 133 CFM / Sq" of radiused area.
***The weight of the oil in the mist will change this, but it is a starting point.

Just some thoughts which might help move things along. . .

Cheers
 

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Discussion Starter · #72 ·
Mighty Mouse has stated that a 3/4" ID hose is good for 1k HP. The number has been repeated by other race shops - so that's an empirical number.

The problem is that we don't really know the airflow of the crankcase - because for every piston moving down creating pressure there is another piston moving more or less opposite, creating temporary vacuum.

So the actual airflow OUT of the PCV system is not the CFM of the air consumed by the motor. It would vary based on RPM, ring efficiency and boost I would think.

But, some airflow calculations suggest a 3/4" pipe can handle 60-70CFM with a starting pressure of 10psi over 3 feet. That would be similar to almost 100 HP of potential airflow. Or, 10% of the approximate power output of my motor.

Seems like a lot of capacity for venting blowby to atmosphere when the catch can "valve" opens under boost?

Sent from my SM-G991U1 using Tapatalk
 

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Mighty Mouse has stated that a 3/4" ID hose is good for 1k HP. The number has been repeated by other race shops - so that's an empirical number.

The problem is that we don't really know the airflow of the crankcase - because for every piston moving down creating pressure there is another piston moving more or less opposite, creating temporary vacuum.

So the actual airflow OUT of the PCV system is not the CFM of the air consumed by the motor. It would vary based on RPM, ring efficiency and boost I would think.

But, some airflow calculations suggest a 3/4" pipe can handle 60-70CFM with a starting pressure of 10psi over 3 feet. That would be similar to almost 100 HP of potential airflow. Or, 10% of the approximate power output of my motor.

Seems like a lot of capacity for venting blowby to atmosphere when the catch can "valve" opens under boost?

Sent from my SM-G991U1 using Tapatalk
Just a quick thought or two…

I’m thinking the CFM flow of the 3/4” ID hose, must be proportional to the volume of flow of the Blow-By or ring leakage. Take that hose flow area, into the piston / bore area. What is the proportion given as a percentage?

At this point, that’s a beginning… Lol

At this point, I would also not discount the windage issue within a Y-block, having a large bore, and moderate to high RPM and resultant piston speeds.
 

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May I ask a question please. . .

Has anyone done any calculations, regarding how large any of these hoses need to be,
versus flow determined to vent the crankcase, versus a given HP level?

Again, if we are pumping 1500 cfm on the top of the piston,
we are also pumping 1500 cfm on the bottom of the piston.
***That's your total potential windage for each engine rpm.

If you divide the above by 4. as each engine rpm has 4-Pistons moving 90° (4 * 90)= 360°
you can zero in on what each piston contributes to the windage.

One of the things that would interest me, is;
How many square inches are the inter-bay vents, versus the square area of the pistons / bores.

Then one might be able to back into the / a useful number?

Since the B-15 lsX is warranted for 900 fwHP, that also gives you a number to use.
900 fwHP, means GM is assuming the engine is going to pump ~1350 CFM.

Then, what would be the assumed blow-by, given as a percentage of CFM,
that the GM Engineers might have worked with?

Empirically, many have stated a number 10AN hose is required for engines with ~1000 fwHP.

What can a number 10AN hose flow?
To begin with; figure about 133 CFM / Sq" of radiused area.
***The weight of the oil in the mist will change this, but it is a starting point.

Just some thoughts which might help move things along. . .

Cheers
I wouldn't assume anything based on the OEM build rating, I've had some issues.
 

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Discussion Starter · #75 ·
Just a quick thought or two…

I’m thinking the CFM flow of the 3/4” ID hose, must be proportional to the volume of flow of the Blow-By or ring leakage. Take that hose flow area, into the piston / bore area. What is the proportion given as a percentage?
To assume the bore of the hose must be proportional to the volume of flow from ring linkage must also include the effective "plenum" area of the crank case, the valve cover area AND the hose diameter. I suspect the blow by is creating wavefronts of pressure, which of course increases with chamber pressure (leakage) and piston speed. But those pressure waves also somewhat dissipate into the valve cover areas before being funneled into the PCV system. We don't really know how much air volume we're creating from blow-by, and it obviously varies by motor, ring seal and chamber pressures. At the end of the day, it may not matter to much in the "real world."

That's the beauty of the "wild" MM can: as soon as the PCV system registers anything other than negative pressure (vacuum), the flap valve will open to release any positive pressure into atmosphere; essentially directly venting into the engine bay when under boost. That's specifically WHY I chose the can and routed things the way I did. When you let off the loud pedal, and the system regains vacuum from closing the bypass valve in the S/C, the flap valve closes and it again becomes a closed PCV system.

At the end of the day, perhaps the question isn't how much CFM of crankcase blow-by I'm creating at 7K RPM on ethanol... it's really "how long does a 3/4" tube take to bleed off any positive crankcase pressure?" Because that's essentially the only barrier between my valve covers and atmosphere under positive pressure situations, as if you were simply running really tall breathers on the valve covers. At 200* F, the speed of sound is over 1250 feet per second. We'll assume the velocity of the pressure wave is close to this (it's technically slower, but I haven't found an easy way to calculate this). So let's say the actual pressure waves travel around 1,000 fps. That means any excess crankcase pressure/windage will expand into the valley and valve cover areas, then into the PCV hoses (3/4" diameter, estimate 3-4 feet in length) and then vent into atmosphere through the flap valve in approximately 0.004 seconds. How those pressure waves dissipate in amplitude over the same distances and interact with seals, etc, is something super nerds will have to contemplate.

In short, I think over-sizing the hoses into a "valved" catch can solves the problem, when the system is setup correctly.

I need to get my axles back together so I can properly test it. :love:
 

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I agree with what you said, there, but I will not do the math. The sources of pressure build up would no doubt include ring blowby as well as valve seal leakage (boost and exhaust back-pressure) and would be impossible to calculate without direct measurement.
My approach is the same as you detailed, using -10 hoses. I'm not teeing them but using two separate -10 fittings in the can. I would assume that these two hoses would be plenty as long as I don't let the can get full or the filter saturated. How well the system works will have a lot to do with what sort of baffles are in use as well. I went with the valve covers I chose primarily due to the baffle and fitting arrangement which looks promising. Can't WAIT to test it!
 

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To assume the bore of the hose must be proportional to the volume of flow from ring linkage must also include the effective "plenum" area of the crank case, the valve cover area AND the hose diameter. I suspect the blow by is creating wavefronts of pressure, which of course increases with chamber pressure (leakage) and piston speed. But those pressure waves also somewhat dissipate into the valve cover areas before being funneled into the PCV system. We don't really know how much air volume we're creating from blow-by, and it obviously varies by motor, ring seal and chamber pressures. At the end of the day, it may not matter to much in the "real world."

That's the beauty of the "wild" MM can: as soon as the PCV system registers anything other than negative pressure (vacuum), the flap valve will open to release any positive pressure into atmosphere; essentially directly venting into the engine bay when under boost. That's specifically WHY I chose the can and routed things the way I did. When you let off the loud pedal, and the system regains vacuum from closing the bypass valve in the S/C, the flap valve closes and it again becomes a closed PCV system.

At the end of the day, perhaps the question isn't how much CFM of crankcase blow-by I'm creating at 7K RPM on ethanol... it's really "how long does a 3/4" tube take to bleed off any positive crankcase pressure?" Because that's essentially the only barrier between my valve covers and atmosphere under positive pressure situations, as if you were simply running really tall breathers on the valve covers. At 200* F, the speed of sound is over 1250 feet per second. We'll assume the velocity of the pressure wave is close to this (it's technically slower, but I haven't found an easy way to calculate this). So let's say the actual pressure waves travel around 1,000 fps. That means any excess crankcase pressure/windage will expand into the valley and valve cover areas, then into the PCV hoses (3/4" diameter, estimate 3-4 feet in length) and then vent into atmosphere through the flap valve in approximately 0.004 seconds. How those pressure waves dissipate in amplitude over the same distances and interact with seals, etc, is something super nerds will have to contemplate.

In short, I think over-sizing the hoses into a "valved" catch can solves the problem, when the system is setup correctly.

I need to get my axles back together so I can properly test it. :love:
Let me see if I can make this easy for you Jesse:

Yes, heat does have an impact on velocity.

If the hose is too small, flow will begin quickly, but then the hose will velocity choke early.

However, if the velocity is sufficiently high, flow direction
won't change quickly. . . Which can be good!

If the hose is too large, then the velocity will be slow, flow
will begin slowly, also possibly causing turbulence / stall to
take place. But the flow can change direction quickly.

Generally speaking, at normal engine temperatures, most use
1116 feet per second to calculate velocity.

Most in this industry flow at 28" of water depression.

It is generally accepted that the flow through an orifice, having an area of one square inch, and having a proper radius, will when flowed at a depression of 28" of water, velocity choke at 146 cfm. Per the math in my signature below, the velocity will amount to 350 fps @ 28" of water.

Why does the industry use 28" of water?

Because all one has to do is double the velocity value
and we have the velocity through a live engine.

So then; (2 * 350)= 700 fps
=> (700 / 1116)= 0.63 Mach

And No! Our heads don't come close to flowing that type of velocity..lol

So, if the hose is too small, it might velocity choke, causing
the issues some have had with rear main seals leaking.

If it is too big, then it might not have the velocity to carry the oily mist
'The Distance', as it might simply stall.

What would be the correct sized hose for your application?
Frankly, I don't know?

And since most all science projects begin with some 'Empirical Finding', you’re on your way. And if required, you now also have some understanding of the applied physics.. :)
 

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To assume the bore of the hose must be proportional to the volume of flow from ring linkage must also include the effective "plenum" area of the crank case, the valve cover area AND the hose diameter. I suspect the blow by is creating wavefronts of pressure, which of course increases with chamber pressure (leakage) and piston speed. But those pressure waves also somewhat dissipate into the valve cover areas before being funneled into the PCV system. We don't really know how much air volume we're creating from blow-by, and it obviously varies by motor, ring seal and chamber pressures. At the end of the day, it may not matter to much in the "real world."

That's the beauty of the "wild" MM can: as soon as the PCV system registers anything other than negative pressure (vacuum), the flap valve will open to release any positive pressure into atmosphere; essentially directly venting into the engine bay when under boost. That's specifically WHY I chose the can and routed things the way I did. When you let off the loud pedal, and the system regains vacuum from closing the bypass valve in the S/C, the flap valve closes and it again becomes a closed PCV system.

At the end of the day, perhaps the question isn't how much CFM of crankcase blow-by I'm creating at 7K RPM on ethanol... it's really "how long does a 3/4" tube take to bleed off any positive crankcase pressure?" Because that's essentially the only barrier between my valve covers and atmosphere under positive pressure situations, as if you were simply running really tall breathers on the valve covers. At 200* F, the speed of sound is over 1250 feet per second. We'll assume the velocity of the pressure wave is close to this (it's technically slower, but I haven't found an easy way to calculate this). So let's say the actual pressure waves travel around 1,000 fps. That means any excess crankcase pressure/windage will expand into the valley and valve cover areas, then into the PCV hoses (3/4" diameter, estimate 3-4 feet in length) and then vent into atmosphere through the flap valve in approximately 0.004 seconds. How those pressure waves dissipate in amplitude over the same distances and interact with seals, etc, is something super nerds will have to contemplate.

In short, I think over-sizing the hoses into a "valved" catch can solves the problem, when the system is setup correctly.

I need to get my axles back together so I can properly test it. :love:
Which of these are you leaning towards, or have you already committed?
Font Diagram Brand Magenta Logo
 

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I am doing what is labeled there as the "Big Boy" method except that the illustration misses a detail.
The red block at the center of the can is NOT the boost check, it is the PCV valve. Meanwhile, the blue line would have the Boost Check inline to prevent the CC vapors from going to the inlet when in boost.
When the snout sees vacuum, it pulls through the PCV from the can, the can vent poppet is closed, the can then pulls from both valve covers, the VCs pull from the crankcase and the valley pulls from the inlet tube thru the boost check for fresh air.
At least that's my read on it.
 

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Discussion Starter · #80 ·
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