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Discussion Starter · #1 ·
Well, I figured a separate thread to discuss this issue might work a little better. I'm trying to sort a PCV valve for the airbox in my 748R to work with the corse undertail breather. I know Motowheels has one that's like $130 or something crazy. Other people have suggested cutting a stock breather apart but the only one's I have are the bonded all plastic ones which ccannot be dismantled.


What I'm really wondering here is does this breather valve absolutely HAVE to be a reed style? Plenty of cars out there running the generic inline plunger type for miles and miles not burning any oil. Running this style PCV valve would also allow tight packaging and let it fit under an MWR filter.

Has anyone used this style PCV valve with the undertail corse breather boxes? If it would work, they're like 5 bucks for a generic one at the local autoparts store and would seem a move economically viable option isntead of spending crazy money on an aftermarket unit, or hacking up an used stock crankcase mounted valve.


Thoughts and opinions?
 

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As long as the rate of flow (in cfm's) is at least as fast as what OEM and replacement breathers are capable of, I can't see any reason why you wouldn't be able to use a different style.
 

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Discussion Starter · #3 ·
Well that's what I was thinking. Most of the generic replacement units will work with anything from a small 4banger to a SBC so they should be able to handle the CFM from my high-comp 853.

My reasoning is this: A spring loaded one way valve is a spring loaded one way valve, regardless of design or layout. The inline plunger style has worked great for well over 60+ years so why not on a bike right? I guess if she starts puffing smoke and there's oil in the airbox I've got my answer lol.
 

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Mr Leakered
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Here you go:

http://www.ducati.ms/forums/40-sport-touring/92584-breather-being-naughty.html

Shazaam's post on ducatiupnorth.com leaves out a couple details. That thread fills in the blanks.

We have comparable CCs, so you should see a similar improvement. The low end response surprised me.

I literally went to Autozone, who had PCVs in easy open boxes, and just sucked on them to find the one with the highest flow at low and high 'suction.' =)

Coring out the plastic breather didn't last long as the seam did pop, but it was damaged to start with. The race version I got was made for a race sized tube, but I was able to stretch with stock one over the nipple. It took a bit of work, some swearing, and a few beers.

Have a good one.
 

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I wouldnt bother, some say it yields hp but noone can really come up with proof. well the ones that produced it and tested it themselves of course, which means nothing.
V8 guys have come up with proof but then they literally suck the air out, which is not the case here.
Assuming you bought a gutted one, you can take what you have as breather today and pick it apart and put it the other way in the airbox.

To me its just a pretty thought.
 

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I've got a Triton, This has a 750 parallel twin motor and boy do they have a problem with crankcase pressure. I enlarged the holes into the timing chest and put a one inch pipe from there to the back of the bike. A lot of my mates were not convinced of it's value and took the piss out of it. Until evening when the bike was sitting chugging at idle I blocked the tube and stopped the engine dead. 90 Degree Vs don't have as big a problem but it is still there. I doubt Ducati would have gone to the trouble of a Corse system if it wasn't useful.
 

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Mr Leakered
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I wouldnt bother, some say it yields hp but noone can really come up with proof. well the ones that produced it and tested it themselves of course, which means nothing.
V8 guys have come up with proof but then they literally suck the air out, which is not the case here.
Assuming you bought a gutted one, you can take what you have as breather today and pick it apart and put it the other way in the airbox.

To me its just a pretty thought.
May or may not add WOT / full pull HP on a dyno. I don't know. It certainly adds a significant amount of torque at part throttle openings.

Have a good one.
 

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As you are flying down a back straight somewhere.....what air pressure is getting into the air box?

do you think that it is greater than the crankcase pressure at that point?

and if it is it may have an adverse effect?

for the sake of applying a one way valve......
 

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Discussion Starter · #11 ·
I wouldnt bother, some say it yields hp but noone can really come up with proof. well the ones that produced it and tested it themselves of course, which means nothing.
V8 guys have come up with proof but then they literally suck the air out, which is not the case here.
Assuming you bought a gutted one, you can take what you have as breather today and pick it apart and put it the other way in the airbox.

To me its just a pretty thought.

^So are you saying just vent the return line out of the corse breather box to atmosphere? When I spoke to Steve at ECS he had mentioned that some people had also done this. Also, the 865 twin in my Thruxton have been known to dump a little oil in the airbox occasionally when run really hard too. Funny you should mention that.


andy9980: I've already looked into this idea but it seems to be more feasible with the breather that were bonded together with the metal band. As I mentioned the two that I have are both the all plastic style which if cut and flipped would require either epoxy or plastic welding to reseal and that just doesn't seem worth the effort.


tonered: You know I completely forgot about that site. I ahd actually read that article a while back when I had considered running the open K&N breather on my other 748 (which has not vented any oil on my rear tire in 2500 hard miles *knock on wood*) I see the ford inline valve which is just an inline plunger style PCV valve is suggested which was my initial idea.

I will pick one of these up and see how it functions. I imagine it should work just fine, but we'll see.

Thanks for all the input guys.:D
 

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Mr Leakered
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You're welcome.

I plugged the drain hole in my airbox long ago when I found the PO didn't do the drain line recall and I was sucking unfiltered air through the melted end of the drain tube. With it blocked, I get a small amount of oil that sits in the drain's well and some oil mist on the inside of the box. A single papertowel is more than enough to clean it up during a valve service. I had similar amounts of oil in the box before the mod.

Atmospheric is an improvement, but suction is better. As noted above, Corse wouldn't bother otherwise. I have no reason to distrust the K&N breather. It was just easier to go this route, versus stripping out all the breather parts.

STs typically run with a completely chopped lid due to the restricted size of the airbox. This is identical to the DP kit. Even with no lid, there is negative pressure in there to supply the breather mod. The closed airbox on the SBKs might be even more effective.

I'm not sure if there is a speed at which the air box on the desmoquattro SBKs get a positive pressure. I would guess the 1199 might. We know the S1000RR gets it peak HP at speed due to ram air. Regardless, at that point the breather mod won't be working, but neither would the stock setup.

Again, I found a nice perf increase at part throttle openings, which is enough to satisfy me for this mod. WOT throttle is, and has always been, great. I really don't know if this mod helps at WOT as much as the typical airflow mods (DP kits). The front comes up easier now than when I bought the bike.

Have a good one.
 

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I've got a Triton, This has a 750 parallel twin motor and boy do they have a problem with crankcase pressure. I enlarged the holes into the timing chest and put a one inch pipe from there to the back of the bike. A lot of my mates were not convinced of it's value and took the piss out of it. Until evening when the bike was sitting chugging at idle I blocked the tube and stopped the engine dead. 90 Degree Vs don't have as big a problem but it is still there. I doubt Ducati would have gone to the trouble of a Corse system if it wasn't useful.
I've done a lot of work with Brit twins including vintage racebikes, and because that application requires a catch tank for the breather, what I ended up with for a breather system was a large hose like yours, but with a reed valve to prevent any backflow. This hose went to a nipple on top of the oil tank, and the tank and engine breather combined came from another top nipple on the tank. The advantage is that any oil carried out the breather is deposited back in the oil tank, and very little is carried out the separate tank breather to the catch tank.
 

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A simple PCV from a car won't handle the pressure variations/volume of a high rpm twin.It simply won't flow enough air. Keep in mind an average auto engine has at least 4 times the crankcase volume and turns well less than half the speed along with a constant vacuum source to help evacuation of the crankcase pressure.A reed valve or a oneway diaphram valve from an air injection system used on older autos can be made to work but it takes some fabrication. A regular PCV valve will allow crankcase pressure to build to the point of blowing oil into the airbox or out any weak gasket or seal.
I went down that road with my 851/955 racebike,even with a big reed in the system revs over about 9000 puked oil everywhere.[But it sure was fun!]
 

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Discussion Starter · #16 ·
Well then wtf am I supposed to do? Call a dealer and see if they happen to just have an old random corse airbox breather floating around?

There has to me a more economically viable option here. Does anyone know if that Ford diverter Valve is a reed style or not?
 

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Discussion Starter · #19 · (Edited)
Alrighty, looks like I'm gonna hack apart two of these stupid stock breathers. Going to just take the cap from one and see about threading it onto the base of the other to make essentially a double sided breather. Will run it inline in the hose to avoid the need for a big huge thing sticking out of the inside of the airbox.

This is the best solution I can think of at this point, as I can mount is where the stock breather box was just aft of the vertical head allowing the remainder of the hose to run from the valve to the box and sit flush in the opening.

If anyone has any thoughts on why they think this is a stupid idea lol, let me know now before I snag another breather (want to run another STM on the other bike, and will use it's stock one to mutilate along with the 748R stock one to make my creation lol).


edit: Just snagged an old style breather with the metal band clamp off ebay right now. Will slice up the side of the band clamp to remove it and get the outlet portion. I will smooth over on the outside and refit the metal clamp to secure them and use a second band clamp around the outside to cinch the metal clamp down to hold it all together. This should me it somewhat serviceable as I will be able to remove the inlet side to clean as needed.

Will post pics up of my creation as I go.
 

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Mr Leakered
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A simple PCV from a car won't handle the pressure variations/volume of a high rpm twin.It simply won't flow enough air. Keep in mind an average auto engine has at least 4 times the crankcase volume and turns well less than half the speed along with a constant vacuum source to help evacuation of the crankcase pressure.A reed valve or a oneway diaphram valve from an air injection system used on older autos can be made to work but it takes some fabrication. A regular PCV valve will allow crankcase pressure to build to the point of blowing oil into the airbox or out any weak gasket or seal.
I went down that road with my 851/955 racebike,even with a big reed in the system revs over about 9000 puked oil everywhere.[But it sure was fun!]
It's working for me. The issue here is that the oil trap is now part of the crankcase volume. The vacuum is a benefit on top of that. I have yet to see oil puking anywhere other than the existing base gasket leak (thus Mr Leakered). I have replaced the clutch hub seals, but at that time the motor had over 50,000mi on it. I'm now close to 65k.

I would agree that glassing a reed valve into the airbox as shown in the ducatiupnorth article would be the best route, but I wanted to give the easy solution a try. It worked well enough for me.

Well then wtf am I supposed to do? Call a dealer and see if they happen to just have an old random corse airbox breather floating around?

There has to me a more economically viable option here. Does anyone know if that Ford diverter Valve is a reed style or not?
In posts about the ducatiupnorth article, shazaam never elaborated on that as I hoped he would. I had to assume it was just a standard, ball-type automotive PCV. There are some out there that will only flow the same amount of air no matter the pressure. Out of the selection I was looking at, I picked the largest diameter one that flowed the most air.

Although, if you look at small, one way valves in McMaster-Carr, you will see there are some flapper valves that would flow big air. I believe some were rated for oil exposure.

I wasn't using anything special, but I could not get my all plastic breather to seal. The joint is fairly deep with the integrated reeds. You might have luck with an epoxy, but. . .

Tonered, care to elaborate on your statement about part throttle improvement?
As noted in my linked post above, after the mod when rolling on the throttle, the response was so much improved that I found myself being sat up in the saddle due to the unexpected torque. I was getting more low end torque than I was expecting/used to. It took a few days to get familiar with it again.

Have a good one.
 
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