I'll be reviewing the Mighty Mouse "wild" catch can (and their kind of awkward website with weird option lists) here. But overall, I'm happy so far.
My "positive crankcase ventilation" thread.
Okay, so I am running a 400" highly modified motor with a 2650 Kong blower and enough pulley to generate 19+ psi at full beans. I run a typical catch can in the "valley/snout" loop as is traditionally done. My build is a 4-digit power level at the crankshaft, and I tend to push oil out of the valley cover under boost, but since that's better than the rear main seal I haven't fixed it in years. 
Anyway, I've decided to re-think my PCV system, and after some careful deliberation I have decided to use a Mighty Mouse "wild" catch can as I will illustrate below:
First off, a discussion of "Positive Crankcase Ventilation:" This means, the crankcase is actively being scavenged for harmful gasses while the car is running, which is 95+% of the vehicle's operational life for most of us. Because engines generate negative intake manifold pressure at idle and part throttle (ie a vacuum), this vacuum, when applied to the crankcase, does all the work for us and it's just a matter of creating a closed loop as illustrated below.
Note: Passively venting to atmosphere as is often utilized by hot rodders is ineffective, as you will not be pulling fresh air into the crankcase - only pushing excess pressure out when blow-by slightly over-pressures the crankcase. And that passive venting usually ends up ALL over your engine bay, leaving you with an oily, nasty mess. At the end of the day, the air internally will always be contaminated with sulfurs and other harmful byproducts that will corrode your springs, valves, oil, etc. Passive venting will also not allow excess fuel and moisture to be removed, further contaminating your oil and reducing its life significantly. Most of the catch cans I see today are either still completely reliant on the OEM system, or they close off the OEM routine and passively vent to atmosphere.
The OEM system is decent for OEM power and boost levels, but of course has no catch can - so intake manifold vacuum (the Supercharger snout) pulls essentially straight from the inner valley, where the air and oil vapors are most turbulent. With increasing power comes increasing airflow required to not only evacuate the crank case, but handle the increasing VOLUME of blow-by that occurs with higher boost and loose piston rings, while still trying to separate oil vapor from. Thinking about air as a fluid, when using OEM-sized 3/8" vacuum hoses, there's not enough volume for the pressure spikes when hitting 15-20psi! Also, under boost the evacuated air is hotter and traveling faster than at idle or part throttle, which decreases the filtering efficiency of the catch can.
So, I wanted a closed loop can for traditional part-throttle scavenging and I needed either sufficiently large enough hoses to accommodate the pressure changes, or ideally a blow-off valve. I did NOT want to open-vent all of the time, as that reduces ring seal, smells horrible, and of course leaves oil residue all over your engine bay. The Mighty Mouse "Wild" can fit my requirement as it has an effective flapper-type blow off valve, a one-way valve from the vacuum source to limit reversion under boost, and the flexibility to fit my CTSV Wagon where I want to put it while still utilizing positive ventilation (almost all of the time).
The PCV routing system options:
![Product Font Material property Magenta Diagram]()
Option #1: The MM recommended option is using one valve cover as the inlet for fresh air, the second for evacuation, and of course the S/C Snout for vacuum as shown on the upper left. The valley cover is capped.
I'm trying this one first, as I have super-sized the PCV evacuation hose up to 3/4" line (compared to OEM 3/8" line). In conjunction with the MM "blow off valve" I expect to keep all my seals in place going forward. I will monitor the fresh air line (ie the Airaid air intake tube) for oil build-up. If it occurs, then I have some 1-way check valves I will splice into the fresh air feed line to keep oil vapors from reverting up under boost. I don't expect it to be an issue, however.
Option #2: If - and this is a big IF - the first option is unsatisfactory, I have contemplated doubling the evacuation volume by running two 3/4" lines (one from each valve cover), then using the valley snout as the fresh air inlet. The MM can can be re-arranged to accommodate this easily, so that also factored into my purchase.
This option would also probably be the best if you needed to run a closed can (ie for road racing where a valved vent would not be legal).
Option #3: The factory / OEM PCV system: No catch can, just a single loop from the valley cover to the S/C Snout. This is why we all run our catch cans in the "S/C to valley loop" and not in the intake tube to valve cover circuit... the former is the "dirty" loop with the spicy hot crankcase vapors; the latter is the fresh air feed and, although it will see some positive pressure under boost, it's such a massively longer circuit that even if oil does start to condense, it will likely do so early in the vacuum hose and then eventually drain back into the valve covers (remember, 95% of the time airflow is in one direction: into the valve covers). But that valley - S/C loop? It's basically a straight shot into your intake manifold, which is why oil will quickly start to pool there, then run down your intakes and onto the valves, and into the cylinders.... Yay!
I'm still waiting on a replacement axle as I sheared some bolts off, but the car idles well. It idles very well, but I did notice a drop in manifold vacuum at idle, so I will have to check for small leaks - I'll update that as I go.
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![Automotive tire Motor vehicle Automotive exterior Hood Electrical wiring]()
The can: The red filter has a rubber "stopper" inside that seals against the top of the can. Anything other than negative pressure will push the flapper up, and instantly vent to atmosphere. The 3/4" line goes to an oil-fill adapter on my passenger valve cover. The 1/2" line goes to the supercharger snout (vacuum).
![Motor vehicle Automotive fuel system Auto part Gas Coil]()
The valley is now capped (we'll see if that cap stays on under boost, or if I'll need to use a zip tie to secure it). A 1/2" hose does fit over the S/C nipple, but the nipple itself is still ~3/8" diameter. Oh well. I still wanted larger hose diameter to reduce flow resistance in all directions, even if the fitting itself is a restriction.
![Hood Automotive tire Motor vehicle Automotive lighting Car]()
The BIG PICTURE. I will be cleaning things up later, this is just a trial run.
Anyway, I've decided to re-think my PCV system, and after some careful deliberation I have decided to use a Mighty Mouse "wild" catch can as I will illustrate below:
First off, a discussion of "Positive Crankcase Ventilation:" This means, the crankcase is actively being scavenged for harmful gasses while the car is running, which is 95+% of the vehicle's operational life for most of us. Because engines generate negative intake manifold pressure at idle and part throttle (ie a vacuum), this vacuum, when applied to the crankcase, does all the work for us and it's just a matter of creating a closed loop as illustrated below.
Note: Passively venting to atmosphere as is often utilized by hot rodders is ineffective, as you will not be pulling fresh air into the crankcase - only pushing excess pressure out when blow-by slightly over-pressures the crankcase. And that passive venting usually ends up ALL over your engine bay, leaving you with an oily, nasty mess. At the end of the day, the air internally will always be contaminated with sulfurs and other harmful byproducts that will corrode your springs, valves, oil, etc. Passive venting will also not allow excess fuel and moisture to be removed, further contaminating your oil and reducing its life significantly. Most of the catch cans I see today are either still completely reliant on the OEM system, or they close off the OEM routine and passively vent to atmosphere.
The OEM system is decent for OEM power and boost levels, but of course has no catch can - so intake manifold vacuum (the Supercharger snout) pulls essentially straight from the inner valley, where the air and oil vapors are most turbulent. With increasing power comes increasing airflow required to not only evacuate the crank case, but handle the increasing VOLUME of blow-by that occurs with higher boost and loose piston rings, while still trying to separate oil vapor from. Thinking about air as a fluid, when using OEM-sized 3/8" vacuum hoses, there's not enough volume for the pressure spikes when hitting 15-20psi! Also, under boost the evacuated air is hotter and traveling faster than at idle or part throttle, which decreases the filtering efficiency of the catch can.
So, I wanted a closed loop can for traditional part-throttle scavenging and I needed either sufficiently large enough hoses to accommodate the pressure changes, or ideally a blow-off valve. I did NOT want to open-vent all of the time, as that reduces ring seal, smells horrible, and of course leaves oil residue all over your engine bay. The Mighty Mouse "Wild" can fit my requirement as it has an effective flapper-type blow off valve, a one-way valve from the vacuum source to limit reversion under boost, and the flexibility to fit my CTSV Wagon where I want to put it while still utilizing positive ventilation (almost all of the time).
The PCV routing system options:
Option #1: The MM recommended option is using one valve cover as the inlet for fresh air, the second for evacuation, and of course the S/C Snout for vacuum as shown on the upper left. The valley cover is capped.
I'm trying this one first, as I have super-sized the PCV evacuation hose up to 3/4" line (compared to OEM 3/8" line). In conjunction with the MM "blow off valve" I expect to keep all my seals in place going forward. I will monitor the fresh air line (ie the Airaid air intake tube) for oil build-up. If it occurs, then I have some 1-way check valves I will splice into the fresh air feed line to keep oil vapors from reverting up under boost. I don't expect it to be an issue, however.
Option #2: If - and this is a big IF - the first option is unsatisfactory, I have contemplated doubling the evacuation volume by running two 3/4" lines (one from each valve cover), then using the valley snout as the fresh air inlet. The MM can can be re-arranged to accommodate this easily, so that also factored into my purchase.
This option would also probably be the best if you needed to run a closed can (ie for road racing where a valved vent would not be legal).
Option #3: The factory / OEM PCV system: No catch can, just a single loop from the valley cover to the S/C Snout. This is why we all run our catch cans in the "S/C to valley loop" and not in the intake tube to valve cover circuit... the former is the "dirty" loop with the spicy hot crankcase vapors; the latter is the fresh air feed and, although it will see some positive pressure under boost, it's such a massively longer circuit that even if oil does start to condense, it will likely do so early in the vacuum hose and then eventually drain back into the valve covers (remember, 95% of the time airflow is in one direction: into the valve covers). But that valley - S/C loop? It's basically a straight shot into your intake manifold, which is why oil will quickly start to pool there, then run down your intakes and onto the valves, and into the cylinders.... Yay!
I'm still waiting on a replacement axle as I sheared some bolts off, but the car idles well. It idles very well, but I did notice a drop in manifold vacuum at idle, so I will have to check for small leaks - I'll update that as I go.
-----------------------------------------------------------------------
The can: The red filter has a rubber "stopper" inside that seals against the top of the can. Anything other than negative pressure will push the flapper up, and instantly vent to atmosphere. The 3/4" line goes to an oil-fill adapter on my passenger valve cover. The 1/2" line goes to the supercharger snout (vacuum).
The valley is now capped (we'll see if that cap stays on under boost, or if I'll need to use a zip tie to secure it). A 1/2" hose does fit over the S/C nipple, but the nipple itself is still ~3/8" diameter. Oh well. I still wanted larger hose diameter to reduce flow resistance in all directions, even if the fitting itself is a restriction.
The BIG PICTURE. I will be cleaning things up later, this is just a trial run.
1 - 20 of 140 Posts
I was running a dual weapon x catch can watch a built 418 at 19lbs of boost and was pushing oil out my rear main seal. I went to 10an fittings on my valve covers to a dedicated motorsports catch can and no longer have oil issues.Okay, so I am running a 400" highly modified motor with a 2650 Kong blower and enough pulley to generate 19+ psi at full beans. I run a typical catch can in the "valley/snout" loop as is traditionally done. My build is a 4-digit power level at the crankshaft, and I tend to push oil out of the valley cover under boost, but since that's better than the rear main seal I haven't fixed it in years.
Anyway, I've decided to re-think my PCV system, and after some careful deliberation I have decided to use a Mighty Mouse "wild" catch can as I will illustrate below:
First off, a discussion of "Positive Crankcase Ventilation:" This means, the crankcase is actively being scavenged for harmful gasses while the car is running, which is 95+% of the vehicle's operational life for most of us. Because engines generate negative intake manifold pressure at idle and part throttle (ie a vacuum), this vacuum, when applied to the crankcase, does all the work for us and it's just a matter of creating a closed loop as illustrated below.
Note: Passively venting to atmosphere as is often utilized by hot rodders is ineffective, as you will not be pulling fresh air into the crankcase - only pushing excess pressure out when blow-by slightly over-pressures the crankcase. And that passive venting usually ends up ALL over your engine bay, leaving you with an oily, nasty mess. At the end of the day, the air internally will always be contaminated with sulfurs and other harmful byproducts that will corrode your springs, valves, oil, etc. Most of the catch cans I see today are either still completely reliant on the OEM system, or they close off the OEM routine and passively vent to atmosphere.
The OEM system is decent for OEM power and boost levels, but of course has no catch can - so intake manifold vacuum (the Supercharger snout) pulls essentially straight from the inner valley, where the air and oil vapors are most turbulent. With increasing power comes increasing airflow required to not only evacuate the crank case, but handle the increasing VOLUME of blow-by that occurs with higher boost and loose piston rings, while still trying to separate oil vapor from. Thinking about air as a fluid, when using OEM-sized 3/8" vacuum hoses, there's not enough volume for the pressure spikes when hitting 15-20psi! Also, under boost the evacuated air is hotter and traveling faster than at idle or part throttle, which decreases the filtering efficiency of the catch can.
So, I wanted a closed loop can for traditional part-throttle scavenging and I needed either sufficiently large enough hoses to accommodate the pressure changes, or ideally a blow-off valve. I did NOT want to open-vent all of the time, as that reduces ring seal, smells horrible, and of course leaves oil residue all over your engine bay. The Mighty Mouse "Wild" can fit my requirement as it has an effective flapper-type blow off valve, a one-way valve from the vacuum source to limit reversion under boost, and the flexibility to fit my CTSV Wagon where I want to put it while still utilizing positive ventilation (almost all of the time).
The PCV routing system options:
View attachment 161791
Option #1: The MM recommended option is using one valve cover as the inlet for fresh air, the second for evacuation, and of course the S/C Snout for vacuum as shown on the upper left. The valley cover is capped.
I'm trying this one first, as I have super-sized the PCV evacuation hose up to 3/4" line (compared to OEM 3/8" line). In conjunction with the MM "blow off valve" I expect to keep all my seals in place going forward. I will monitor the fresh air line (ie the Airaid air intake tube) for oil build-up. If it occurs, then I have some 1-way check valves I will splice into the fresh air feed line to keep oil vapors from reverting up under boost. I don't expect it to be an issue, however.
Option #2: If - and this is a big IF - the first option is unsatisfactory, I have contemplated doubling the evacuation volume by running two 3/4" lines (one from each valve cover), then using the valley snout as the fresh air inlet. The MM can can be re-arranged to accommodate this easily, so that also factored into my purchase.
This option would also probably be the best if you needed to run a closed can (ie for road racing where a valved vent would not be legal).
Option #3: The factory / OEM PCV system: No catch can, just a single loop from the valley cover to the S/C Snout. This is why we all run our catch cans in the "S/C to valley loop" and not in the intake tube to valve cover circuit... the former is the "dirty" loop with the spicy hot crankcase vapors; the latter is the fresh air feed and, although it will see some positive pressure under boost, it's such a massively longer circuit that even if oil does start to condense, it will likely do so early in the vacuum hose and then eventually drain back into the valve covers (remember, 95% of the time airflow is in one direction: into the valve covers). But that valley - S/C loop? It's basically a straight shot into your intake manifold, which is why oil will quickly start to pool there, then run down your intakes and onto the valves, and into the cylinders.... Yay!
I'm still waiting on a replacement axle as I sheared some bolts off, but the car idles well. It idles very well, but I did notice a drop in manifold vacuum at idle, so I will have to check for small leaks - I'll update that as I go.
-----------------------------------------------------------------------
View attachment 161792
The can: The red filter has a rubber "stopper" inside that seals against the top of the can. Anything other than negative pressure will push the flapper up, and instantly vent to atmosphere. The 3/4" line goes to an oil-fill adapter on my passenger valve cover. The 1/2" line goes to the supercharger snout (vacuum).
View attachment 161793
The valley is now capped (we'll see if that cap stays on under boost, or if I'll need to use a zip tie to secure it). A 1/2" hose does fit over the S/C nipple, but the nipple itself is still ~3/8" diameter. Oh well. I still wanted larger hose diameter to reduce flow resistance in all directions, even if the fitting itself is a restriction.
View attachment 161794
The BIG PICTURE. I will be cleaning things up later, this is just a trial run.
That's actually why I'm asking - I only saw lines to two valve covers; but then it clicked! The DMS can is simply open-venting to atmosphere.. Running an "open" filter, venting to atmosphere, is almost useless in our cars and isn't recommended, as it only releases excess crankcase pressure; there is no "ventilation" or recirculation of crankcase vapors in that scenario. Yes, it's saving the rear main seal but at the expense of unnecessary pollution and concentrating combustion byproducts (ie sulfurs, fuel, moisture and contaminants) within the crankcase, and ultimately your oil. This will dramatically shorten oil life, cause corrosion to internal parts and generally be bad for bearings over the long haul.
The 1920's called - they want their fancy "draught tube" back.
Although, the 1920's draught tube was actually more effective than your open breather setup as it had a second vent as a means to pull fresh air into the engine.That's actually why I'm asking - I only saw lines to two valve covers; but then it clicked! The DMS can is simply open-venting to atmosphere.. Running an "open" filter, venting to atmosphere, is almost useless in our cars and isn't recommended, as it only releases excess crankcase pressure; there is no "ventilation" or recirculation of crankcase vapors in that scenario. Yes, it's saving the rear main seal but at the expense of unnecessary pollution and concentrating combustion byproducts (ie sulfurs, fuel, moisture and contaminants) within the crankcase, and ultimately your oil. This will dramatically shorten oil life, cause corrosion to internal parts and generally be bad for bearings over the long haul.
The 1920's called - they want their fancy "draught tube" back.
[/QUOTE
With a closed system my crank case pressure was way to high. A vented can was the only option to keep the pressure low.That's actually why I'm asking - I only saw lines to two valve covers; but then it clicked! The DMS can is simply open-venting to atmosphere.. Running an "open" filter, venting to atmosphere, is almost useless in our cars and isn't recommended, as it only releases excess crankcase pressure; there is no "ventilation" or recirculation of crankcase vapors in that scenario. Yes, it's saving the rear main seal but at the expense of unnecessary pollution and concentrating combustion byproducts (ie sulfurs, fuel, moisture and contaminants) within the crankcase, and ultimately your oil. This will dramatically shorten oil life, cause corrosion to internal parts and generally be bad for bearings over the long haul.
The 1920's called - they want their fancy "draught tube" back.
1 - 20 of 140 Posts
