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Next OCMD project: crankcase pressure reduction system?

Old 12-25-2011, 08:55 AM
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Next OCMD project: crankcase pressure reduction system?

Now that I am kind of running out of options with the mods, I am turning to the less obvious areas. In that light, and in the knowledge that four-strokes suffer from significant pumping losses (to the point that mfrs have begun to address the issue in recent sportbikes, for example through the use of larger inter-cylinder vent holes and an actual vacuum pump in the new Ducati Panigale), I have began thinking about figuring out a way to do something similar to my VTR engine.

I had a look at the NAG valve offered by Rising Sun Cycles (NAG Crankcase Pressure Relief) but the price is absolutely ridiculous for what is obviously just a bleed valve. So, I will be looking at fashioning something similar "on the cheap".... The main thing now is deciding whether to use one or two valves (one per valve cover or link them as the NAG set-up does). Also, have to see about calibrating the said valve(s) to get about 0.5 atm vacuum (that should do the trick).

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Old 12-25-2011, 09:08 AM
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You could just buy some pcv valves from the parts store. Same deal, way less expensive. Autozone carries more than you can shake a stick at.
Champ/PCV Valve (PC754) | AutoZone.com
Champ/PCV Valve (PC91) | AutoZone.com

These are two examples, but you can find ones that better fit your aesthetic needs if you take some time to search.
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Old 12-25-2011, 09:25 AM
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Any idea on what a typical psi setting is on those? If it's atmospheric or higher it's of no use.....
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Old 12-25-2011, 02:41 PM
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I just came up with a variation of sorts of my original idea. I have a spare oil filler cap (made from billet) and will drill it out and press a 14mm fitting into it. I will then route a hose from it to the airbox (where PAIR valve air pick-up was formerly). This should help reduce crankcase pressure somewhat (facilitate bleeding off excess pressure) without necessarily putting added stress on the various seals as would perhaps running below atmospheric pressure in the sump.

The cost of this experiment will be very minimal. Will keep you posted.
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Old 12-25-2011, 10:20 PM
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The PVC that you had posted is merely an expensive one. The ones I showed can be had in all sorts of variations from plate to ball valve. They release the pressure from the piston pulse and create a vacuum in the engine as the piston returns back up. No different than the one that you were looking at. The Pair system would actually pull a vacuum on the crankcase. With a little routing work you could run each crankcase vent to the pair system and pull on that crankcase quite well. NOTE: this will require significant monitoring of the oil level through test phase. Good luck, and let us know how it goes.
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Old 12-26-2011, 12:12 AM
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Do you still have the plastic bottle in the airbox and the lines going to it?
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Old 12-26-2011, 04:25 AM
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Thanks Bill. Your suggestion came at around the same time I stumbled across it while doing research on the matter. Some call it the Pair sucker mod as it uses the vacuum from the exhaust to create a partial vacuum in the crankcase. Now I need to explore this further....
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Old 12-26-2011, 04:25 AM
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Originally Posted by 8541Hawk View Post
Do you still have the plastic bottle in the airbox and the lines going to it?
at the moment yes.....
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Old 12-26-2011, 06:16 PM
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Well, then, I don't understand. I think you are trying to duplicate a system which is already in place. The airbox collector bottles and system of hoses is already there doing its best to draw a vacuum on the crankcase. That's what that system is there for. Page 1-25 of the service manual shows the hoses going to the valve covers. Page 1-30 includes a description and flow path for the system. What exactly are you trying to accomplish?

If you're trying to draw an actual vacuum on the system, installing some kind of pump may be counterproductive, as the energy required to run the pump may exceed any gains benefited from said pump.
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Old 12-26-2011, 07:25 PM
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http://www.autoshop101.com/forms/h63.pdf
Vacuum Pumps, High Amp Alternators, Racing Pulleys and Mandrels from GZ Motorsports

Yes, there is a point of diminishing returns when it comes to a system like this, so you can lose power. Up til then, power will be gained (looks like 5% according to info on those pages). Using the existing system for ventilation and putting a valve inline to the air box will insure the highest vacuum, of which little to none is from the airbox. The airbox venting of these gases is so that the engine can digest it for EPA standards.
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Old 12-26-2011, 07:39 PM
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Interesting read. So the challenge seems to be to find a small enough pump with a specific capacity such that you don't exceed your desired vacuum, say 12". Then, find a DC motor which will power the pump and will be reliable enough to run constantly while the bike is running. Finally, find a spot to put it and plumb it in neatly.

This sounds like fun. Take pics along the way and I'd be interested in seeing before/after dyno runs.
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Old 12-26-2011, 08:17 PM
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The underlying idea is to reduce crankcase pressure. One option is to provide more bleed area to prevent the build-up (venting the oil cap; similar effect to the Big Breather mod used by Thorsten Durbahn). The other is to use the natural vacuum present in the exhaust system (exiting exhaust gases leaving partial vacuum behind themselves) and essentially tapping into it (via the PAIR ports) and using it to create a partial vacuum in the sump.

Apparently all the roadracing teams are using the latter type of set-up and report increased power from reducing pumping losses (see pic; vented cap with line leading to PAIR port....). I saw some reports of positive results, for example a 4 hp gain on a ZX-12....
Attached Thumbnails Next OCMD project: crankcase pressure reduction system?-2012557-pair.jpg  
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Old 12-27-2011, 07:23 AM
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Originally Posted by Hawkrider View Post
Well, then, I don't understand. I think you are trying to duplicate a system which is already in place.

that's what I was thinking reading this...

How about a dry sump oil system? Reduce parasitic power loss from parts turning through the oil (does that even happen on a VTR motor?). A proper system would also apply negative pressure to the crank case which you are looking for.

just an idea I had
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Old 12-27-2011, 07:34 AM
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Just trying to simplify things how about checking to see how much pressure or vacuum is currently present In the case before designing something
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Old 12-27-2011, 10:28 AM
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Well now that I have a little better understanding of what is going on....

Now as I see it, the NAG set up is basically a glorified PCV valve to keep the positive pressure from back streaming to the crank case.

I don't think you would need this or anything else as the reeds on the pair system should already be doing that job.

It would be interesting to hook a vacuum gauge to one of the pair ports and see what king of negative pressure is actually generated by them.

Now to figure out why they hook to the side cover and use the oil fill port instead of using the fitting on the valve cover....
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Old 12-27-2011, 05:22 PM
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It is in the read. There are a couple issues. running to high of a vacuum at the top of the engine would go counter flow to oil draining down from the cyl head. This could cause some issues. The other item of concern is that you dont run too high of a vacuum. A pair system could pull to much air, and might require a valve to bleed in fresh air from the air box in the case that it exceeds the desired pressure.
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Old 12-27-2011, 05:37 PM
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Having quickly read up on PCV valves, I saw they maintain a slight vacuum in the crankcase so that may very well be the way to go. Simple and effective near as I can tell right now.....
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Old 12-27-2011, 05:43 PM
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Here is a pic of the NAG valve installed ina VTR. Sure looks like a PCV valve to me....
Attached Thumbnails Next OCMD project: crankcase pressure reduction system?-nag-valve-vtr.jpg  
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Old 12-27-2011, 05:48 PM
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Well after thinking about it today, my take is a little different.

As the engine will leak as it is no where near vacuum tight, the farther you get from the vacuum source, the higher the pressure (or less pressure differential\vacuum)

as the goal here would be to create a low pressure zone under the piston, going from the clutch cover makes sense.

So as I see it, most of the bits needed for this experiment are already there.

The pair reed valves should do just fine in regulating the vacuum (as that was their job to begin with)

So you would need a fill plug with a hose port on it.

Then something to put in-line to use as a vapor trap, so most of the oil vapor can re-condense and drain back into the sump.

The next step would be to see if one pair port creates enough flow to pull a vacuum to make a noticeable difference. Personally I don't think you will create enough flow to cause any problems.

Though my first step would be to rig a vacuum gauge to the pair port to see what kind of pressure differential you actually get from the pair port.

If not you might need to make up a vacuum can of some kind that you can hook both pair lines up to and then run a line to the clutch cover.

Sounds interesting and very workable after a little experimenting....
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Old 12-27-2011, 05:49 PM
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......... ...From another site.............

Last edited by 1971allchaos; 12-27-2011 at 06:04 PM.
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Old 12-27-2011, 05:53 PM
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Originally Posted by mikstr View Post
Here is a pic of the NAG valve installed ina VTR. Sure looks like a PCV valve to me....
Looks like one to me also and the way it is plumbed, in that pic, I also don't think it is working....

That is why the plastic bottle has the opening pointing towards the wall of the air box. That way the air blowing between the bottle and wall causes a vacuum in the bottle.

In the picture, I don't see how you can get air blowing over the valve opening, instead it looks like it will blow directly into the opening.....but that is another story....
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Old 12-27-2011, 05:57 PM
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Originally Posted by 1971allchaos View Post
the NAG set up is basically a glorified PCV valve to keep the positive pressure from back streaming to the crank case.
I understand, the reason for the extra venting from the crank case... And understand the effects of the P.A.I.R system...
Mikstr, Would you get the same outcome if you removed the reed valves from under the covers??
Well I'll step in and say yes you could get the same results by removing the reed valves completely and running a NAG type valve.

The problem would be that you would have hot gas all the way to the valve.

So you would get faster hose wear and carbon in the hose all the way to the valve, which might cause it to stick. The reed valves eliminate all these problems and they are also free...
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Old 12-27-2011, 06:21 PM
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Originally Posted by 8541Hawk View Post
Well I'll step in and say yes you could get the same results by removing the reed valves completely and running a NAG type valve.

The problem would be that you would have hot gas all the way to the valve.

So you would get faster hose wear and carbon in the hose all the way to the valve, which might cause it to stick. The reed valves eliminate all these problems and they are also free...
You wouldn't have hot gases up to the valve, just somewhere in between the port and the valve, and that would depend on the pressure differential. The carbon that you will get will be from the mist and vapors of the crankcase, and that will likely occur in the cylinder head more so than the hoses. It also doesn't matter where you run the vacuum in the engine when it comes to where you would like the vacuum to be, it matters based on what direction you want gases to flow. That is why you can have it on top of the engine, but also why it can cause problems with oil starvation to the conrod. I am not fully convinced that running it past the pair is the best plan because of the potential for carbon build up in the small passage, whereas you can use all the existing plumbing of the crankcase venting with condensation vessels by just adding a valve in the hose coming off the cylinder head. I guess we will see which way Mikstr goes on this one.
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Old 12-27-2011, 06:51 PM
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Assuming the NAG valve is set to open at below atmospheric pressure (assuming we are speaking of a one-way valve of course), it will open and bleed pressure out whenever the threshold pressure is reached. Once the pressure in the case is equal or below to that on the other side of the valve (in this case the airbox), the valve will close, effectively sealing the crankcase and keeping the pressure inside below atmospheric.

As our engines are 90 degree Vees, there is fair amount of variation in the crankcase volume (area under pistons), as oppsed to an inline-four, for example where it is relatively constant (two pistons going up, two going down), so there is a constant flux of pressure (from high pressure to partial vacuum) with every stroke of the crank. The bottle set-up allows these pressure variations to be felt all the way into the airbox, since it's essentially an extension of the crankcase in its present configuration (can't image this is overly beneficial for jetting, what with all the the turbulence these pressure variations must create). If nothing else, the NAG valve would essentially cut half that activity out (no pulling of air out of airbox due to checker valve), leaving only the pressure spikes into the box (not necessairly bad as they temporarily pressurize the intake).

Also, venting the cap seems like it would also be a good idea as it would allow the pressure rise to bleed out more quickly, reducing the "compressor" effect and allowing the pistons to come down in the cylinders with less resistance. For the NAG valve set-up to work, however, it too would have to be set-up with one as otherwise it would just become a bypass to atmosphere, reducing the effectiveness of the NAG
Just my thoughts for now....

Last edited by mikstr; 12-27-2011 at 07:27 PM.
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Old 12-27-2011, 06:57 PM
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Originally Posted by autoteach View Post
I am not fully convinced that running it past the pair is the best plan because of the potential for carbon build up in the small passage,
That is my concern too, along with having oil vapor going into the pipe. Would it drive up the pipe temperature, possibly to the point of compromising its durability/longevity?

Comments?

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Old 12-27-2011, 07:29 PM
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What if you vent the oiler cap-as planned.. And ran the vent tube from that filler cap hole to a open inlet (No PVC) in the upper section of the airbox lid ...
You would have the slight vaccum, but being the snorkel is open/cool air.. No real pressure. And for carbon being allowed back on the topside of the heads(to the valve train) the air filter would be sacrificed,as a barrier...
The only concern I could think of - Is as I have been told -about messing with the air box (Tweety, Mike, etc..)
What do you think??
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Old 12-27-2011, 07:33 PM
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More ramblings:
- a PCV valve is essentially controlled by intake vacuum but what I think would be needed is the different, one that would be controlled by pressure in the crankcase
- it seems that what would be needed, then, would be a pressure relief valve (one-way) ideally set to lift at about 0.5 atm pressure. THis would allow any pressure above that to bleed off (into the airbox if you want), thereby keeping crankcase pressure below atmosphere.

The other option is simply to not try to regulate the crankcase pressure level itself per se but simply provide a means for it to bleed off more easily (hence the vented cap; this, to soem degree, mimics the move towards larger inter-cylinder vent holes, as used on the latest generation GSX-Rs, for example). It simply facilitates the air movement....
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Old 12-27-2011, 07:41 PM
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Still trying to understand- The need to control, or regulate the pressure coming out of the crank case... Venting the crank case is So smart.. relieving the pressure ..
Where or How would it damage component in the bottom end ?
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Old 12-27-2011, 07:45 PM
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Originally Posted by mikstr View Post
That is my concern too, along with having oil vapor going into the pipe. Would it drive up the pipe temperature, possibly to the point of compromising its durability/longevity?

Comments?
Well the way I see the system working and making usable HP is the idea is to remove that air that is being pumped around.

So a PVC valve in each breather line (to start and these also could be used to regulate the ultimate pressure in the crankcase by leaving one open if you create too much vacuum)

Then use the oil fill port as the pump out point (just venting here is not going to do anything). Then use the pair system to create a vacuum in the crankcase. I see no issues with the oil in the exhaust, as long as you are not blowing clouds of blue smoke, which would mean you need better baffling in your lines.

Other wise you are putting no more oil in the exhaust than what leaks past the valve guides and seals or gets blown by the rings. So like I said, unless you are doing a 2 stroke impersonation, I don't see any problems.

Then it would be a matter of finding out how low of a pressure you can run in the crankcase before you start sucking stuff in past the seals.

Then raise the pressure until the seals work properly and you then have the largest HP gain you will see from this mod due to having the least resistance to the pistons moving.
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Old 12-27-2011, 07:48 PM
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Originally Posted by mikstr View Post
- a PCV valve is essentially controlled by intake vacuum but what I think would be needed is the different, one that would be controlled by pressure in the crankcase..
Read this again.. You know -The late model cages(cars) emission system work this way, So to control waste..manufacturers started this in the early 70's
Owning more than a few earlier vehicles,, The PVC on these engines -work like the valve on a pressure cooker..
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