Plumbing Crankcase Ventilation into Pods

I want to plumb my crankcase vent back into my intake so that I'm burning most effeciently.

I have K&N knockoff pods. The have metal ends, so I'm thinking I can drill a hole and put a hose barb in the center of the metal end.

The question here is this: Do I need to plumb all 4 pods, or would it matter? I'm thinking it shouldn't really matter, since it would be pre-throttle plate. It shouldn't change the vacuum... I'm thinking about just plumbing the inside two pods. (In this case, even if it slightly effects the mixture, it will at least be going into the two inner pods that probably don't flow as much air anyway). It will help on looks, too. Not that my bike is a real looker anyway...

Any thoughts/suggestions? Anybody have a better idea on plumbing the ventilation back in?

 

Personally its a waste of time as you gain nuthing and no one else does either...exhaust fumes is still exhaust fumes .

do what you like...

 

I agree with Hoonz. But if you really want to do it I would just plumb into the intake vacuum and not have to worry about the filters. An inline filter can be added to the large crankcase line so the intake stream stays clean.

 

I'm inclined to disagree with my esteemed colleagues, simply from the standpoint that the vacuum that is generated by the intake circuit is invaluable in helping seat the piston rings. Not to mention the reduced emissions as crank case blow-by is re-introduced into the intake. The crank-case blow-by is also reduced by the vacuum assisted seal on the piston rings. Kind of a win-win situation. But there are a few catches. 1- This will not improve your power, it will reduce it (not by much though, remember it is diluting your air/fuel mixture) but given the environmental concerns, this shouldn't be too much of a concern. 2- You would need to plumb all four pods to get the maximum vacuum available. If you plumbed the vent to only one pod, that cylinder would only provide you with the vacuum 1/4 of the time you needed it. Additionally, it would be the only cylinder getting the blow-by gasses, causing an imbalance in its power charge characteristics, throwing off your synchronization and making the entire bank imbalanced.
IMHO, this is a question you will have to answer yourself. Are you looking for power or are you looking for efficiency? Or is the desire appearances? It is my personal belief that if you hunt for efficiency, power comes as a result. If you’re concerned with the appearance of the bike, don't bother plumbing the air pod with the breather line. Your better off not putting it in. Just be sure to put in a good breather with a catch baffle for the oil. If you’re looking for the added efficiency of the vacuum on your piston rings (and, by extension, reduced emissions) you have to plumb all of your pods.
I hope that this helps you some in making an informed decision.

 

Problem with that Robert, is that you don't get much vacuum on the filter side of the carbs. The vacuum is on the other side of the throttle blades. Your thinking is sound, that's the way a PCV system works in a car, vacuum is plumbed into the crankcase to aid in ring sealing, but you don't get a measurable amount of vacuum on the pods to get any affect here.

The only reason to plumb the oil breather back into the airbox is for improved emissions, which Robert already covered.

 

So plumbing the vent to the intakes and bypassing the carbs is a bad idea because you need the carbs to regulate the gases? i.e they will pull what they need from a pressurized airbox?

 

I work at an environmental testing supply company, so I know how dirty things already are around here. I guess mostly I want the thing to be alittle more efficient. I also want to reduce the restriction, and perhaps get a little vacuum on the blow-by gasses. It is my impression that blow by gasses, if not sucked away, lead to decreased oil life due to the unburnt gases running around in the crankcase. I'd like to burn those off. If my bike burns a little cleaner in the process, that'd be great.

I think I'll be plumbing all four. I was more or less looking for other suggestions on where to plumb in. I'd like to be able to plumb in on the filter side of the carbs, but not actually drill through the filter tips, but there's very little space/material through which to plumb fittings. I'll need to look more closely later.

I think that running the vac to the intake side of the carbs(presumably the sync fittings) is probably a bad idea, since there's a considerable amount of vacuum there..., besides the fact that one of those vacuum ports is occupied by the petcock vacuum line.

Thanks for the responses on this, by the way... keep it comin

 

Pigmouse,
I had the same idea to reattach breather hose to pods.
I have'nt done it yet but I'm still thinking.
My Idea.?.?
Might work Might not??????
1.Vacuum hose T-ed 4 ways
2.Drill hole in each Pod end.
3.Insert T-ed ends into each Pod.

 

Joel, your right about the vacuum signal behind the carbs on pods. However, in the stock configuration, there is ample signal given the restrictive nature of the airbox. To use the vacuum to suck the blow-by dictates using the signal from the airbox side. If you were to use the signal from the manifold side, you would lean out your fuel mixture and upset your air/fuel ratio. I'm with you on the stronger signal from the intakes but to get the system to work correctly, you must plumb to the airbox side. Plumbing pods poses its own challenges. Namely the proximity you would need to get the EGR pipe to the intake bell in order to get a strong enough signal to be useful and not interfere with anything. There is the rub.
Another issue I would like to dispell is the perceived uslessness of the EGR. Years ago, emissions requirements were met by manufacturers using vacuum pumps (smog pumps) on vehicles. Ever wonder why NASCAR started using them? Because of the efficiency improvements offered by negative pressurizing the crankcase. Admittedly there was no emissions gain in mind when doing this (NASCAR dumps the output from this pump into a breather, not back into the intake stream) but it improved power because of the improved ring seal. Now Joe-on-the-street doesn't care one bit about any of this but using the EGR system in a manner it was intended can be benificial to the vehicle and the air. I strongly advocate its retention and use. Best of luck fellas, I don't think it should be very hard to accomplish.

 

Replace EGR with PCV in the above post.
I think :wink:

EGR comes off the exhaust, and I don't know of any bikes that have them.

 

Yup, I'm retarded. Thanks Pigmouse, I ought to take up drinking coffee.

 

Well I learned a lot from that. Thanks Robert.

 

pcv =positive crankcase ventilation , fer people wondering...


Same as a running motor , it no suck , it is blown , by 14.8psi .....

 

PCV is what I was referring to, I goofed (little too much sugar in the lemonade this morning).

I'm puzzled HooNz, I've never had need to measure crankcase pressure before and have had this information repeated to me in several periodicals as well as my automotive encyclopedia. I'm aware of slight positive pulses being typical, but on the whole, the vacuum signal will suck the blow-by out weather or not there is positive crankcase pressure. Am I missing something here? The vacuum supplied is supposed to perform this evacuation. Any one else got a thought on this?

 

The blowby is produced by the opposite motion of the pistons (I think) as well as what little pressure "blows by" the rings from the combustion. The positive crankcase pressure is a natural "equal and opposite reaction" to the pistons being forced down after the compression stroke.

In essence, it's like the inverse of the exhaust. It stands to reason that it will be actively BLOWING out of the hole, meaning that very little vacuum is required to "suck" the blowby gasses.

Wow this has been a pretty decent thread...

 

Time to put a twist on the conundrum of crankcase ventilation.

Crankcase pressure is created as pigmouse stated by the pistons coming down the bore causing a displacement of air.

Herby lies the question. Four pistons moving. Two up, two down. Shouldn't the displacement of air created by the two coming down be taken up by the vacuum displacement of the two going up?

Shouldn't this create a Neutral Air Environment inside the crankcase?

Of course, we all know that most of our XJ's will let a fair amount of air out the breather or oil filler while the engine is running.

Given the hypothetical NAE theory, where does the expelled air come from in a sealed crankcase?

100% blow by from the rings?


Cheers
HG - Thinking too much today. :wink:

 

Well, you're always going to have certain amount of pressurized combustion gas in the crankcase, because as you know, rings don't seal 100%. Add worn cylinders and weak rings into the equation, and you get even more positive pressure in the crankcase. I don't think the pressure is from the pistons moving down, but from combustion gasses.

 

Excellent point HG, I'm thinking that a slightly positive pressure would be the resultant condition. The pistons do displace the air volume in the case (just like inside the cylinders) and while two are moving up, two are moving down in perfect synchronicity, effectively negating one another. Enter the blow by gasses. Here is the resultant pressure. Good point my friend. Your totally right Joel, no ring set will seal perfectly (although the "gap-less" rings are supposed to, but I've no knowledge of their efficiency) and will allow a bit of gas through, more if they are worn. I think we can put this one to bed.

 

Also don't for get that the gases introduced by blowby are hot and will expand the ambient air in the crankcase pressurizing it even more.

 

I went to a different subject without even realizing , i twas on about a point and i no can even figure out what it was..

But , that bit above is referenced by a factual fact that most people think that as a motor is running the vacuum created by the pistons going down with only the intake valve open that that it is "sucking" , we'll it ain't , as all that is happening due the the enlarged displacement it is creating a lower than atmosphere pressureless area and as atmospheric pressure is 14 odd psi above whatever the inside chamber would be at a intantanious time the higher pressure naturally moves [it has too] to the lower pressure area to try and remain at equlibberiam?.. so a motor is blown by 14 odd psi , a calculator would shoot holes in this as it will not be a complete vacuum so in fact the difference will not be 14psi and i know that , typing this is enough for me , its just the idea without being too accurate but the basic's are there , barn door meckaniks , ok?.....

And yet , the vacuum of outer space which seems quite expansive compared to little earyth one could debate greatly which sucked or was blown when a little hole opened between the two :roll: .. so since we on little earyth the basis i opinionated is from that reference point , here.

 

Huh??? I've got to get my conversion program upgraded to include Oz speak. Let's see if I understand what you wrote HooZn.
Your saying that the pressure generated in the motor is generally going to be 14 psi, more or less and has nothing to do with the valves. With you so far but I'm confused as to how a calculator is involved. And I'm so very glad there aren't any leaks in our atmosphere to the great void beyond (but it sticks around because of gravity so I guess we're safe for now). Oh Positive Negative One, please spell it out for me, I'm having a dumb attack.

 

HooZn is stating the fact that, here on earth, at sea level, we have about 14 lbs of air pressure pushing against everything. The higher up you go the less pressure, that's why your ears wanna pop going up a mountain side or in an airplane!

Inside the engine as the piston goes down it creates a low pressure area, open a valve and the atmosphere wants to rush in to fill the void! The piston doesn't suck air into the cylinder.

Same thing takes place with a water pump, the pump won't suck, it just creates a low pressure at the impeller and the atmosphere pushes the water up the pipe to the pump.

 

Ah yes. I'm familiar with the process, simple physics really. Has to do with one of Bernoulli's principles (the one with the venturi tube). Air rushes in to fill the low pressure developed in the venturi, raising its velocity. Not that it is exactly like the internal area of our motors but the demonstration of normal air pressure rushing in to fill a low pressure area. I comprehend the reference HooNz was making now. Thanks Nick.

 

Wow. This is great.
This is the most techy talk I've seen on XJbikes. I think I'm getting a stiffy....

Oh wait, no that's the atmospheric pressure rushing into my empty pockets. :wink:

 

Whoosh!

 

The calculator is involved "with" and "at" a time reference so one would need one if one ain't good at maths like me.

Maximum and averages , eg:the maximum fixed vacuum would be ??? [but we know its variable] so the balance to be adjusted at 14psi would not be 14 as i mentioned but a lower value , a example fixed state -5 to +14 = +9 ...

Then there is the averages with a heep of things like restriction and rpm involved and heat and atmospheric pressure....

So out here , how many "thought" a engine "Sucks".

Sucks petrol in , Blows it Out !. meckanically a common used word is Displacement , so now it does not mean just "size" but to displace.

And if i got a long pipe [or mc'donalds straw] and shoved it into outaspace from here teknically what should happen is a whoosh out! , i guess robert something else is holding it all in :idea: .

All i Care about is When twist throttle , it goes .

 

Suzuki's are the only bikes that Suck. :lol: :lol:

 

you are absolutley correct. it doesn't take a lot of vacuum to pull out crankcase gases. basically a pcv valve is just a metered vacuum leak. more intake vacuum pulls the spring and plunger/ball in the valve closer to closed. this would be happening at idle or low rpm cruise where crankcase pressure wouldn't be very high and driveability is the main concern. as rpms and load increase and intake vacuum drops this allows the little ball/plunger (just depends on design which style it is) in the vavle to open up allowing more of a vacuum leak to pull the larger amount of crankcase pressure out. even though at a higher throttle percentage your intake vacuum drops significantly there's still enough there to pull those fumes out. crankcase pressure should never (on a auto anyway) should never exceed 3psi and a newer/better ring sealing engine will produce virtually none. if it does it's time to to a cylinder leak down test to check and see how bad the rings are and what percent of leakage it has. i'm not sure what it should be on a bike though.
hope all that makes sense

 

Excellent analogy on the metered vacuum leak. Unfortunately, our machines haven't the check ball, just a plumbed line with a foam baffle system. Seems to work just fine though. You ought to see the crud I cleaned out of mine after 90K miles.

 

yeah, it's just a breather. oh well though. i can only imagine how much crud was in there. pretty impressive with the 90k though.

 

Preventitive maintenance works! I did swap the motor after 80K after my bone-head brother put 5 quarts in the crankcase, but not any trouble otherwise (I did have to pull the replacement motor and replace the broken starter chain guide, but they will all do that from age). I'm hopeful to have the original engine overhauled with new seals and such by the end of the year.

 

so on a bike motor what's the cylinder walls look like after that many miles? i've never taken a motorcycle engine all the way down yet. key word, yet!!

 

I still have very visible cross hatching and a beautiful round cylinder, no different than any of my automobile engines. If your itching to try pulling one apart, come on over! Weather is fine and we're under 76F partially cloudy skies. Fridge is stocked and SWMBO has just cooked dinner! Excuse me, gotta go, dinner time!!!

 

little far of a drive. lol. that's really amazing though. thanks for the info.

 

Whatever you decide to do about the crankcase vent hose make sure it doesn't get clogged up and don't put a restrictive filter on it or run the hose so far that it has a lot of resistance to the air flow or the pressure will start blowing out your gaskets and cause oil leaks everywhere.

 

Well, what would be the best option for those of us with pods? I don't really care about venting it back into the motor, but currently I have a cheap filter on it from Advance Auto, just like the ones you see on valve covers often. Would think it wouldn't be too restrictive, but just looking for some other suggestions.

 

i would think that would work just fine. that's all i've got on my v-star and it works great.

 

Sounds like what you have is acceptable for performance. K&N makes a very nice unit, check them out.

 

Umm. Yeah.

DO NOT PUT AN AUTOMOTIVE PCV VALVE ON YOUR CRANKCASE VENT if you are running pods!

Trust me. It is bad. I have the oil leaks to prove it already. Too much restriction. Kills mpg also. I just hope the harm is not too far gone now that I've realized what's going on. I hope this post saves somebody from the ignorance I had.

Oh yeah, don't try plugging it with a bolt, either.... You do need it.

 

There should be no harm done mechanikkly , maybe a seal , then again maybe not..

 

Ok I was going to buy the pods to, but have no intentions of running the crankcase breather back into the airstream. So you guys are saying I am gonna need a crancase breather, or a filter? I am more in the trucks/cars automotive feild and somewhat newer to the road bike thing (I grew up on dirt bikes though). I am just asking a question as simple as what to do with the vent hose from the case? Thanks, Chad

 

The simple answer is to read the previous three pages and draw your own conclusion. No single person is right or wrong. The simple answer is, there is no simple answer.

It's more about what you can afford and whether you want to look after your engine properly.

If your still unsure after reading the last three pages then leave your airbox in.

If you can't work it out with all the information provided then you should leave well enough alone. We don't need another three pages discussing the same topic again if your not prepared to read.

 

Umm yeah read through it twice and didn't come up with a straight answer. No need to get all uptight and rude about it.

 

oooooooh rude dude.

 

Well if you read it twice then you should understand that there is no simple answer. It's all there in black and white. The choice is yours alone as to how you do it. Nobody can say what you should do.

 

Do a google search for "motorcycle crankcase filter" and you will have a few options for sticking a filter on the end of the vent hose.

 

Hi,
You guys put on an informative read here.
I have a 82 xj750 maxim. I am currently putting on a Mac 4-1 exhaust, A dynojet stage 3 kit and k&N pod filters. I guess there are two options for the crankcase hose.

1. I am considering connection the crankcase hose to the pods.
or
2. Just leaving the hose and putting on a mesh of some sort to help prevent anything from entering it.

What do you suggest for better overall performance and less maintence?. I am not too concerned about the environmental aspects.

Thanks a lot for your replies to this.

 

Environmental issues aside, I'm going to suggest the plumbing of the hose to your pods so that they can all take turns pulling the vacuum on the hose to help with ring seating and it spreads the oil/fuel vapor across the cylinders so that you don't load down only one cylinder.
Simpler set up is simply venting to the atmosphere but you do loose the vacuum.

 

Another advantage of plumbing into the pods that hasn't been mentioned yet is that they help prevent your pods from falling off.

Quite a few posters have mentioned losing one or more pods. It might come loose but can't fall off.

 

Rigging the pods with a little safety tether is probably a good idea.

Wasting time trying to rig-up the crankcase vent to the Pods is silly!

Run a hose from the crankcase vent to a place where a right angle fitting can be permanently affixed and a section of hose extended down and held in place - vertically.

Cut the bitter end of this downward vertical extension on a severe bias, so that there becomes a "Leading edge" of hose before the elongated opening to atmosphere.

At speed ... the lower pressure created behind the hose will cause the crankcase to become vented.