Crankcase vent vacuum setup removal = bad

[Langanobob]

^ Unofficial Counterpoint  :

There definitely was a shitstorm over the 696.  But I think the end result has been plenty of sales, albeit to a new breed of owner of the undesirable kind that hands out in NMC    But a marketing success for Ducati.

And dry sumps are technically cool.  I don't really think there would be any real resistance from purists.  And real purists still think belt drives are a sacrilege but they're selling.

I think it's pure economics, rather than resistance from the marketing guys; the bikes seem to be selling OK as is, although I don't have any recent sales numbers, so why change anything major.

[hunduc]

let me revive this old thread as i am thinking about this mod now and i have probably the same qualms ducatiz might have had when he started this thread. but i start to arrive to a different result he did. looking at the famous posts he copied in at the start of the thread, i actually do not see any reference to a vacuum. the bcm post talks about hollowing the reed valve out - people do not do that when they do this mod. it also worries about oil build-up above the valve, but how will that damage the engine (as long as you check that your oil level is fine, and maybe clean up the filter or any gunk in the hose - if you put your filter on top of a hose)? the more to-the-point nichols post is a little bit confusing to me. first, no mention of a vacuum there either. (i do not argue that there is no vacuum there, i just argue that it does not have a profound effect on the operation of the valve - i think the vacuum generated by an open airbox fairly far away from the crankcase breather is not even close to the pressure generated inside the engine by possible blow-by gases) second, the sentence "The stock system is less restrictive because there is more volume making it less restrictive." does not make sense to me - how is the volume of the hoses+oil breather box+airbox bigger than the whole atmosphere? later parts of the post talk about race bikes (no vacuum mentioned) and then again about monsters, with the similarly confusing statement "Therefore, the system that allows you the largest volume to pump into is the stock system. This system pumps into the airbox and has the added benefit of a collection/separation tank between the crankcase and the airbox." again, how is the atmosphere smaller than those he mentions? and again, no mention of the vacuum. also, by stating the system "pumps" sort of implies that the crankcase blow-by gas pressure is the more important in opening the valve, not the airbox vacuum. 

again, i do not argue that you can have ill side effects - blow-by spitting oil on your leg or on the rear tire for example. but i do not think this mod can damage the engine itself.

also, it might be against the law, but all our exhaust mods are against that as well. and i think the exhaust mods have a worse effect on the environment than this one.

any proof that this mod can damage the engine?

[Fergus]

Isn't the advantage to the airbox the fact that the engine is sucking air in, creating an effectively lower pressure than would be the case w/o the airbox?

[hunduc]

absolutely, the only question is, how big is that effect compared to the pressure coming from the crankcase. is it big enough so that by removing it, you alter the behavior of the valve so much so that some sort of damage results in the engine?

[ducatiz]

Isn't the advantage to the airbox the fact that the engine is sucking air in, creating an effectively lower pressure than would be the case w/o the airbox?

you mean the engine intake are sucking air?  if so, yes.  the airbox has a vacuum and draws on the crank vent.

[Ddan]

absolutely, the only question is, how big is that effect compared to the pressure coming from the crankcase. is it big enough so that by removing it, you alter the behavior of the valve so much so that some sort of damage results in the engine?

At a BCM maintenance seminar, Bruce Meyers said the difference in power was minimal in a 2 valve motor, I can't imagine there would be any way venting the crankcase to atmosphere could actually cause damage

[junior varsity]

had mine vent to atmosphere for a half dozen years now it seems. no problems.

would i do it again? probably not. i already did it on this one and it looks good, don't have the parts to go backwards.

on a sbk, hell no i would not do it.

[hunduc]

would i do it again? probably not.

why not? pls elaborate...

[Howie]

At a BCM maintenance seminar, Bruce Meyers said the difference in power was minimal in a 2 valve motor, I can't imagine there would be any way venting the crankcase to atmosphere could actually cause damage

Yes, the difference is minimal on a 2 valve, but the difference exists.  IMO, the individual needs to recognize there is a difference and removing the breather box itself is not a performance enhancement.  Then that individual can make an informed decision.  Clearly, the power gain from a set of flat slides on short manifolds trumps the power loss of venting to the atmosphere.

[koko64]

I run FCR 41s with an open air box, but I have kept the stock breather system. I only run the pull cable and can fit it with a squeeze around the breather hose into the air box. I like the idea of intake vacuum helping to relieve crankcase pressure. This assistance with reducing parasitic power losses in the engine due to crankcase pressure may be of benefit as I'm running higher compression pistons and porting which will increase both the mechanical and dynamic compression.

If the stock set up gives one extra horsepower then I'm happy.

[ducatiz]

I run FCR 41s with an open air box, but I have kept the stock breather system. I only run the pull cable and can fit it with a squeeze around the breather hose into the air box. I like the idea of intake vacuum helping to relieve crankcase pressure. This assistance with reducing parasitic power losses in the engine due to crankcase pressure may be of benefit as I'm running higher compression pistons and porting which will increase both the mechanical and dynamic compression.

If the stock set up gives one extra horsepower then I'm happy.

I've often wondered if there is a way to minimize the system so that it's smaller and tanks up less space.  perhaps even used hoses that were form-fit so they snaked around the engine up to the airbox.  I think what bothers people about it is the vent-> hose -> box -> hose -> airbox that adds to the complexity of the engine's look.

[junior varsity]

why not? pls elaborate...

For the reasons listed just above this post and below yours, primarily. If you think about it, it makes since: Air is in the crankcase, when the pistons travel 'down' they need to be able to move that air out of the way. In the stock venting system, the air box and intake are 'pulling' that air out of the way.

I would imagine that the smaller the displacement and shorter the stroke the less it makes a difference, but i got other things on the mind right now to think too much into it.

i removed mine for clutter reasons. just like the airbox.

for performance i'd leave it on, and not only stick with an airbox, but creatively enlarge mine.

[junior varsity]

but creatively enlarge mine.

heh... that's what she said.

[koko64]

 

And you could make a bigger carbon air box, and sell some copies to other DMFers 

[koko64]

I've often wondered if there is a way to minimize the system so that it's smaller and tanks up less space.  perhaps even used hoses that were form-fit so they snaked around the engine up to the airbox.  I think what bothers people about it is the vent-> hose -> box -> hose -> airbox that adds to the complexity of the engine's look.

Yeah, I had to frig around with the hose to make it work. Mine is the stock hose, shortened a little and runs along the side and above the battery box. Very similar to the stock hose run. I put the FCR cable on and then refitted the hose around it with some cursing. It's not too bad. You could easily get some good hose and fittings from an auto/speed shop and rig something up that looked better and fitted easier.

With a hole saw and some fittings I can't see why some of the more crafty types couldn't rig up a hose to one or both of the larger K&N pods.

A thought; opening the air box will probably reduce the vacuum draw on the crankcase hose anyway. Probably works better on the stock air box. Hope I'm wrong. 
Anyone read anything that addresses this?