Crankcase Recirculation on aftermarket intake

[danielflo216]

I've got a GX200 (196cc clone) with many upgrades, among those are an aftermarket airfilter. I was wondering if I could connect the breather hose from the crankcase breather and thread a nipple into the air filter to 'recirculate' the air that comes out of the breather. I am aware that among the air that comes out of the breather there is also oil mist, so I was thinking that an oil catch can is probably necessary as well. I couldn't find anything quite like this online (apart from a setup with a heavily modified 390) but I did see a video from Red Beard Garage of him doing something similar with a catch can, but he didn't recirculate the air from the breather after it came out of the catchcan, he put a filter on the end to vent it to atmosphere, which to me ruins the entire purpose of the catch can, his explanation was that he could get the oil and put it back into the engine but it seems so inconvenient because his catchcan didn't even have a hose to go back to the valvetrain so he had to manually refill the engine with the oil the catchcan caught. Because it doesn't seem like many people have or are doing it I wonder if I would even gain any performance from a setup like that anyways. I was thinking of getting a PCV valve as well because according to my 'research' that is the only way to gain power from a recirculation system. Just wondering if a setup like that or similar would be worth the time and money. I don't even know if what I'm saying makes sense because although I understand the concept I don't know too much about the science behind crankcase ventilation and the best way to maintain good pressure, so if you don't understand me feel free to question me

 

[BaconBitRacing]

Are you trying to do something similar to Smokey Yunick's hot vapor engine? https://www.motortrend.com/how-to/hrdp-1009-what-ever-happened-to-smokeys-hot-vapor-engine/
That system is more than recycling of air, it's a whole system. Personally I wouldn't, I don't see the benefits. I would like to question you. Would you gain more power than you would lose due to less dense, hot air? Would a catch can even work to filter out the oil? Of course, the Ford flathead did have an oil bath air filter, so a bit of intake oil may not be a problem. Link: https://www.underhoodservice.com/oi...s in outside air and,often made of steel mesh).

Another thing, keeping on intaking oil, is how much is exceptable? Over all I don't think any notable gains will come of it, but go karts are for experimentation and fun, so if you want to try it, come up with something.

 

[danielflo216]

Are you trying to do something similar to Smokey Yunick's hot vapor engine? https://www.motortrend.com/how-to/hrdp-1009-what-ever-happened-to-smokeys-hot-vapor-engine/
That system is more than recycling of air, it's a whole system. Personally I wouldn't, I don't see the benefits. I would like to question you. Would you gain more power than you would lose due to less dense, hot air? Would a catch can even work to filter out the oil? Of course, the Ford flathead did have an oil bath air filter, so a bit of intake oil may not be a problem. Link: https://www.underhoodservice.com/oil-bath-air-filters/#:~:text=The oil bath air filter pulls in outside air and,often made of steel mesh).

Another thing, keeping on intaking oil, is how much is exceptable? Over all I don't think any notable gains will come of it, but go karts are for experimentation and fun, so if you want to try it, come up with something.

I hadn't heard of Smokey's engine before this. The technology sounds very ingenuous especially for the time. I was surprised it made more power than the stock engine let alone ran with such lean mixtures without a computer. I guess I'm not aiming for something like that, but more just recirculating the air that would go to waste either way. What you said about how a bit of oil in your intake not being bad. Would just connecting the crankcase breather to a threaded nipple in the air filter be considered 'too much' oil in your intake, or would it have to pass through something similar to a catch can or oil bath? I guess every case is different, even down to how the specific model was manufactured, but I always heard from big youtube channels that especially on smaller and cheaper engines, the breather spat out a lot of oil and it could even hold back an engine with the stock air filter (because the stock ones have a built in nipple to recirculate crankcase pressure). I guess it would be something to test to see if you notice any positive or negative differences to having 'more air' in the intake, but it being less dense air and if it would affect engine performance, as well as varying amounts of engine oil being burnt. I heard somewhere that a bit of engine oil can help keep the piston and cylinder head clean, similar to how antifreeze from leaking head gaskets clean pistons, but it's probably all a myth.

 

[BaconBitRacing]

A few basics with "extra" engine oil in the combustion chamber: Extra carbon deposits. A relatively small amount of may not cause issues, but straight breather air could be a little oil dense. Extra carbon causes some issues, like needing to clean your plug more, and in extreme cases extra engine wear from it building up. The general advice is keep the oil in the bottom end, not the top. Not to mention some smoking. The issue that comes from speculation is how a small engine carb would react to oil going through it for hours upon hours. That flathead I mentioned had a much larger carb, larger combustion chamber, and quite possibly worse machined tolerances. The mention of "air that would go to waste anyway" is right, it would go out into the atmosphere. The issue I run into is hot air. The air coming out of the crankcase is hotter than the surrounding air, and cooler air is more dense. That matters on performance cars. https://www.cars.com/articles/what-does-a-cold-air-intake-do-and-is-it-worth-it-448150/
But I have a theory that pushing hot air into a small engine could be even worse than on a full size car. The reasoning is cars are designed to be able to run hot underhood air, while small engines always have a plentiful supply of cool air. My biggest reason would be after taking a look at a 196CC carburetor. It's tiny! There's only so much room for total mass of air, so it might as well be more dense. Remember, this is theory, but it sounds plausible. Again, I love seeing new things tried, but I don't think I would take the risk with a "daily driver" kart.

 

[danielflo216]

A few basics with "extra" engine oil in the combustion chamber: Extra carbon deposits. A relatively small amount of may not cause issues, but straight breather air could be a little oil dense. Extra carbon causes some issues, like needing to clean your plug more, and in extreme cases extra engine wear from it building up. The general advice is keep the oil in the bottom end, not the top. Not to mention some smoking. The issue that comes from speculation is how a small engine carb would react to oil going through it for hours upon hours. That flathead I mentioned had a much larger carb, larger combustion chamber, and quite possibly worse machined tolerances. The mention of "air that would go to waste anyway" is right, it would go out into the atmosphere. The issue I run into is hot air. The air coming out of the crankcase is hotter than the surrounding air, and cooler air is more dense. That matters on performance cars. https://www.cars.com/articles/what-does-a-cold-air-intake-do-and-is-it-worth-it-448150/
But I have a theory that pushing hot air into a small engine could be even worse than on a full size car. The reasoning is cars are designed to be able to run hot underhood air, while small engines always have a plentiful supply of cool air. My biggest reason would be after taking a look at a 196CC carburetor. It's tiny! There's only so much room for total mass of air, so it might as well be more dense. Remember, this is theory, but it sounds plausible. Again, I love seeing new things tried, but I don't think I would take the risk with a "daily driver" kart.

Yeah definitley. Do I need a breather filter or can I just have the breather going straight to atmosphere. I never really understood why you needed a filter with a crankcase breather because its really just pushing air out most of the time.

 

[BrownStainRacing]

Yeah definitley. Do I need a breather filter or can I just have the breather going straight to atmosphere. I never really understood why you needed a filter with a crankcase breather because its really just pushing air out most of the time.

You should never let the contaminated, heated air from the crankcase get into the intake charge. Thats blow by, air/fuel/ exhaust/oil mixture.

Keep the intake air, clean and cool .

The stock valve/ baffle/pcv, whatever you wanna call it, inside the stock valve cover, is NOT designed to handle the extra blow by from these engines above 4000 rpm.
Remember, these are utility engines, designed to run at a steady constant low (under 4000) rpm and live forever. Asking them to do more, will take more planning and better parts.

Ive tested this using a vacuum/ pressure gauge. Seen HUGE spikes in pressure (+20 psi) really fast, then back to normal 8"-8psi. It happened, over and over again to all the engines I tested, jus at different rpm. I not talking about worn out tiller motors, but well thought out built engines with a few hrs on them.
Even different engine temps, will effect the vacuum / pressure readings from the crankcase.

Hard to believe??? Open up another port to the crankcase, add vacuum/ pressure gauge and watch the bounce at different rpm.
Shocked me too.

The best way I've found to vent the crankcase, is with 2) 1/2" one way check valves, running out of the valve cover. Outta the crankcase will get oil up in them from being slung off the rotating assembly.

These let that extra pressure (from blow by) out, and not let in fresh air, that again causes extra pressure in the crankcase, when the piston is moving from the bottom of the cylinder to the top of the cylinder (vacuum).

These crankcase's are really small compared to the bore and stroke size.

Engines with much bigger crank cases don't have this vacumm/pressure problem.
Look at a 250cc 4-stroke motorcycle engine. It doesn't even have a valve in the crank case, jus an open vent with a tube running to air box. The crankcase is so much bigger because of the internal gear box.
Making sense yet???

Another reason to properly vent the crankcase, is too much pressure under the piston when it's getting blowed down by the power stroke. This extra pressure slows the piston down, which is a MAJOR power robber.
It feels like the engine jus hit a wall and cannot make any more rpm.
Well.......it did hit a wall. A wall of air pressure that should not be there during the power stroke.
Making sense yet???

Here the parts I use. I'm not saying buy them here, or even purchase them at all, it's jus a reference.

Placement of the check valves should be high, jus incase oil gets up there, it can run back down. Small filters should be used to keep from clogging up the check valves with dirt.

Hope this helps.

2 Pcs 12mm 1/2" Fuel Non-Return One Way Check Valve Petrol Diesel Oil Aluminum | eBay

Fit for Carburettor and low pressure fuel systems.

www.ebay.com

Universal 12mm Crankcase Vent Intake Mini Cone Air Breather Filter Chrome BLACK | eBay

Quantity: 1x Air Filter. Universal fits for most cars, trucks, Motorcycle. Color: Black(as pictures show). Neck Size: approx. Width: approx. Height: approx.

www.ebay.com

 

[danielflo216]

You should never let the contaminated, heated air from the crankcase get into the intake charge. Thats blow by, air/fuel/ exhaust/oil mixture.

Keep the intake air, clean and cool .

The stock valve/ baffle/pcv, whatever you wanna call it, inside the stock valve cover, is NOT designed to handle the extra blow by from these engines above 4000 rpm.
Remember, these are utility engines, designed to run at a steady constant low (under 4000) rpm and live forever. Asking them to do more, will take more planning and better parts.

Ive tested this using a vacuum/ pressure gauge. Seen HUGE spikes in pressure (+20 psi) really fast, then back to normal 8"-8psi. It happened, over and over again to all the engines I tested, jus at different rpm. I not talking about worn out tiller motors, but well thought out built engines with a few hrs on them.
Even different engine temps, will effect the vacuum / pressure readings from the crankcase.

Hard to believe??? Open up another port to the crankcase, add vacuum/ pressure gauge and watch the bounce at different rpm.
Shocked me too.

The best way I've found to vent the crankcase, is with 2) 1/2" one way check valves, running out of the valve cover. Outta the crankcase will get oil up in them from being slung off the rotating assembly.

These let that extra pressure (from blow by) out, and not let in fresh air, that again causes extra pressure in the crankcase, when the piston is moving from the bottom of the cylinder to the top of the cylinder (vacuum).

These crankcase's are really small compared to the bore and stroke size.

Engines with much bigger crank cases don't have this vacumm/pressure problem.
Look at a 250cc 4-stroke motorcycle engine. It doesn't even have a valve in the crank case, jus an open vent with a tube running to air box. The crankcase is so much bigger because of the internal gear box.
Making sense yet???

Another reason to properly vent the crankcase, is too much pressure under the piston when it's getting blowed down by the power stroke. This extra pressure slows the piston down, which is a MAJOR power robber.
It feels like the engine jus hit a wall and cannot make any more rpm.
Well.......it did hit a wall. A wall of air pressure that should not be there during the power stroke.
Making sense yet???

Here the parts I use. I'm not saying buy them here, or even purchase them at all, it's jus a reference.

Placement of the check valves should be high, jus incase oil gets up there, it can run back down. Small filters should be used to keep from clogging up the check valves with dirt.

Hope this helps.

2 Pcs 12mm 1/2" Fuel Non-Return One Way Check Valve Petrol Diesel Oil Aluminum | eBay

Fit for Carburettor and low pressure fuel systems.

www.ebay.com

Universal 12mm Crankcase Vent Intake Mini Cone Air Breather Filter Chrome BLACK | eBay

Quantity: 1x Air Filter. Universal fits for most cars, trucks, Motorcycle. Color: Black(as pictures show). Neck Size: approx. Width: approx. Height: approx.

www.ebay.com

Sounds like a good system, but I do have a fuel pump coming from the valve cover so I don't know if venting all of the crankcase pressure will affect its pumping ability as it works off the constant pressure changes in the crank case. I just don't understand the point of a breather filter because a filter is for sucking air in, not pushing it out. If I were to use an air oil seperator instead and connect 2, 1 way ports to the valve cover, 1 taking all the blowby and oil mix and seperating it into oil and air, and another taking the oil back through another 1 way check valve back to the valvetrain to deposit the oil. After looking into it there isn't much information on it but in my mind it just seems like an inefficient and longer version of a breather filter, but If that is the case it doesn't seem like it would hurt too much and i'd be up for the experimentation. But if the system ends up robbing the engine from power due to the warm air I could just attach a breather filter to the air outlet of the seperator.

I've got a clone engine so the manufacturing quality is very poor, I don't run it long enough to know if it leaks oil but I occasionally find a tiny amount of oil in the line that goes from the valve cover to my fuel pump. So I would prefer any potential oil not go out as mist into the atmosphere, rather go to a seperator that gets clean fresh air to either reuse or dispose of and liquid oil to put back into the crankcase.

 

[BrownStainRacing]

I don't know if I need a one way valve. I don't know if I make sense but Ive got a gx200 and I always thought the stock breather from the valve cover was one way, as last time I felt it there was only air coming out, not in. I also have a fuel pump coming from the valve cover so I don't know if venting all of the crankcase pressure will affect its pumping ability as it works off the constant pressure changes in the crank case. I just don't understand the point of a breather filter because a filter is for sucking air in, not pushing it out. If I were to use an air oil seperator and connect one port to the breather, another to the valve cover to return oil, and another to the intake to put just air into the intake, apart from the warm air I don't see how it wouldn't work. I could also just attach a breather filter to the side of the air oil seperator that would go to the intake. I would also have to use 2 one way valves so it only sucked breather air in and put oil back so it doesn't backflow into the seperator

I've got a clone engine so the manufacturing quality is very poor, I don't run it long enough to know if it leaks oil but I occasionally find a tiny amount of oil in the line that goes from the valve cover to my fuel pump. So I would prefer any potential oil not go out as mist into the atmosphere, rather go to a seperator that gets clean fresh air to either reuse or dispose of and liquid oil to put back into the crankcase.

You are making it harder then it is.

Yes that is a 1 way stock valve. It's not a super valve that can handle all rpm's. It will hold open on you at higher then normal rpm, when it should be closed. It doesn't matter what brand, flavor, or color, it's the same designed stock crankcase vent system in every honda clone style OHV small block engine.

Your fuel pump works off of pulse, not pressure. The up and down movement of the piston is whats making your pump work. You will always have vacuum and pressure in the crankcase while the piston is moving.
Try this, start engine, disconnect hose from valve cover, hold your finger over it. Disconnect hose between carb and pump.

It's still pumping fuel. It's jus building too much pressure in crank case now with finger over the other hose.

Never do I have any oil in my catch can. Maybe a drop or 2 of yellow nasty moisture every 3rd or 4th oil change. I don't want that crap back into my crankcase.

I've done the testing, I know the 1 way check valves work.

The vent filters are not super filters, I use them to keep big chunks of debris out of the lines.

Good luck

 

[danielflo216]

C

You are making it harder then it is.

Yes that is a 1 way stock valve. It's not a super valve that can handle all rpm's. It will hold open on you at higher then normal rpm, when it should be closed. It doesn't matter what brand, flavor, or color, it's the same designed stock crankcase vent system in every honda clone style OHV small block engine.

Your fuel pump works off of pulse, not pressure. The up and down movement of the piston is whats making your pump work. You will always have vacuum and pressure in the crankcase while the piston is moving.
Try this, start engine, disconnect hose from valve cover, hold your finger over it. Disconnect hose between carb and pump.

It's still pumping fuel. It's jus building too much pressure in crank case now with finger over the other hose.

Never do I have any oil in my catch can. Maybe a drop or 2 of yellow nasty moisture every 3rd or 4th oil change. I don't want that crap back into my crankcase.

I've done the testing, I know the 1 way check valves work.

The vent filters are not super filters, I use them to keep big chunks of debris out of the lines.

Good luck

Cheers, I'll take your word for it and do some experimenting.

 

[BrownStainRacing]

Try that vacuum/pressure gauge, it'll tell you what right or wrong.

You may find a better set up. If you do, please share your findings.

 

[danielflo216]

Try that vacuum/pressure gauge, it'll tell you what right or wrong.

You may find a better set up. If you do, please share your findings.

Yeah definitley will do, I will probably start with trying a catch can with one way valve and a breather filter. Your right that there probably isn't much that needs to be recirculated and what gets caught in a catch can probably shouldn't go back into the engine. Do you think a one way valve is even necessary with a catch can setup, or would it be dependant on if the pressure is fine without it. I guess every engine has different tolerances and especially those clones can vary drastically model to model, so one engine might be more susceptible to blowby even with upgraded parts.

 

[BrownStainRacing]

Y

Yeah definitley will do, I will probably start with trying a catch can with one way valve and a breather filter. Your right that there probably isn't much that needs to be recirculated and what gets caught in a catch can probably shouldn't go back into the engine. Do you think a one way valve is even necessary with a catch can setup, or would it be dependant on if the pressure is fine without it. I guess every engine has different tolerances and especially those clones can vary drastically model to model, so one engine might be more susceptible to blowby even with upgraded parts.

I really don't need a catch can. It was something I had so I used it.

Now, when I had a hose coming from the side cover (billet, 2 ports) the cam and crank gear slung oil up into the catch can.

Since I have both out of the valve cover with check valves now, no more oil in the catch can.

I got 1 going to can and 1 with vent filter to atmosphere. That made the gauge show less bounce. Both to the can showed more bounce, more pressure.

Keep experimenting, you will find what works for you.

 

[danielflo216]

I really don't need a catch can. It was something I had so I used it.

Now, when I had a hose coming from the side cover (billet, 2 ports) the cam and crank gear slung oil up into the catch can.

Since I have both out of the valve cover with check valves now, no more oil in the catch can.

I got 1 going to can and 1 with vent filter to atmosphere. That made the gauge show less bounce. Both to the can showed more bounce, more pressure.

Keep experimenting, you will find what works for you.

Sorry for bringing this back up but I was wondering if you had a breather filter attached to the stock breather on the valve cover, or just on the two you threaded into the valve cover

 

[BrownStainRacing]

Sorry for bringing this back up but I was wondering if you had a breather filter attached to the stock breather on the valve cover, or just on the two you threaded into the valve cover

I take the plate and stock valve out of the valve cover. Thread that hole for a nipple. Make another threaded hole in valve cover for another nipple. Use 1 check valve for each hole and 1 filter for each check valve.

Place check valves, filters at least 6" above the valve cover so they don't get oil mist in them.

I can grap you some pics later if you need them.

 

[danielflo216]

I take the plate and stock valve out of the valve cover. Thread that hole for a nipple. Make another threaded hole in valve cover for another nipple. Use 1 check valve for each hole and 1 filter for each check valve.

Place check valves, filters at least 6" above the valve cover so they don't get oil mist in them.

I can grap you some pics later if you need them.

Cheers, would be much appreciated

 

[Denny]

You guys have taken something so simple that worked perfectly and redesigned it to not work worth a darn. The purpose of crankcase ventilation systems is many fold.
first is to get rid of any moisture and acid causing byproducts from the combustion process. The second and somewhat lesser function is to put the crankcase under vacuum or neutral pressure to help ring seal.
Leave the stock valve cover on and run the hose from it to the air filter. If you want to make any improvement anywhere it’s getting fresh air into the crankcase. When you remove the governor thread the hole where the arm went through for a 1/8” pipe fitting and get a brass elbow from ACE hardware with a hose barb on it. Thread in the elbow, add 6” of 1/4” hose to it and a fuel filter on the end of that. Then call it done!

 

[BrownStainRacing]

You guys have taken something so simple that worked perfectly and redesigned it to not work worth a darn. The purpose of crankcase ventilation systems is many fold.
first is to get rid of any moisture and acid causing byproducts from the combustion process. The second and somewhat lesser function is to put the crankcase under vacuum or neutral pressure to help ring seal.
Leave the stock valve cover on and run the hose from it to the air filter. If you want to make any improvement anywhere it’s getting fresh air into the crankcase. When you remove the governor thread the hole where the arm went through for a 1/8” pipe fitting and get a brass elbow from ACE hardware with a hose barb on it. Thread in the elbow, add 6” of 1/4” hose to it and a fuel filter on the end of that. Then call it done!

You do it your way, and I'll do it mine!!!!

Put a vacuum/pressure gauge on it and see for yourself.

If you like stock, boring, slow, junk,.... fine. I like my junk to actually haul a$$ and last longer then the normal outta the box tiller motor.

I'll call it done....when I'm ready to call it done!!!!

 

[BrownStainRacing]

@danielflo216
If you are turning less the 4000 rpm, don't bother with the stock crankcase vent/pcv system. Jus add a filter up high and block the hole on the airbox.

If turning more then 4000 rpm, yes I recommend check valves.

Heres some pics. I idle my engines 2000-2200, to get the oil moving and temps up faster. They are NOT normal, stock, boring, turd motors.

on my engine, at idle 2000 rpm, the gauge is bouncing from 2" of vacuum to 2 psi. That's very low, compared to the stock system. At 5900 rpm with a load, it does not go over 10" -10 psi.
Test your stock system and get back to me. You will see that big spike in psi I was talking about earlier.

I've spent hrs, hrs and hrs testing this on different engines and stock valve covers. It's the best I have found.

If you need more pics, jus ask. I got plenty for you.

 

[Denny]

You do it your way, and I'll do it mine!!!!

Put a vacuum/pressure gauge on it and see for yourself.

If you like stock, boring, slow, junk,.... fine. I like my junk to actually haul a$$ and last longer then the normal outta the box tiller motor.

I'll call it done....when I'm ready to call it done!!!!

Must be tough being the smartest person in the room there Jr.

 

[BrownStainRacing]

Must be tough being the smartest person in the room there Jr.

Nah....it's ez,......JR!!!!