A Dissertation On Ventilation - Kawasaki KLR 650 Forum
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Old 10-03-2013, 07:37 PM Thread Starter
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A Dissertation On Ventilation

Extracted from another thread, this discussion was greeted with overwhelming disinterest.

Posting here, maybe connecting the crankcase to intake manifold vacuum is worth a look!

----------------------------

True Believers in the PVC valve mod sincerely think the results are one or more of the following:

* Increased power
* Reduced oil consumption
* Enhanced engine compression braking
* Better ring seating
* Improved fuel mileage

When asked HOW a check-valve in the crankcase breather hose creates these benefits, the responses are, well, vague.

Often, "crankcase vacuum" is cited as somehow responsible for these advantages yielded, although . . . no crankcase vacuum has ever been detected in normal engine operation.

Not surprising there's no vacuum, entirely, because . . . the crankcase ventilation line connects to the airbox at ESSENTIALLY ATMOSPHERIC PRESSURE, and the crankcase accumulates blow-by from the combustion chamber.

So, if crankcase vacuum is desirable, WHY NOT CONNECT THE CRANKCASE BREATHER LINE TO THE INTAKE MANIFOLD????????????

After all, our Positive Crankcase Ventilation automobiles have their crankcase vent lines connected to their intake manifolds, for goodness' sake! (CAVEAT: Positive Crankcase Ventilation's purpose is reducing emissions, pollution control; NOT performance enhancement, in automobiles.)

Connecting the crankcase vent line to the intake manifold (i.e., the rubber hose between the carburetor and the cylinder head, or even the cylinder head input stub) would provide the crankcase with the advantage of MANIFOLD VACUUM. (This notional modification is predicated on the supposition that crankcase vacuum is beneficial. A further note: Without value judgment concerning the justice and wisdom of any Clean Air Act, connecting the crankcase ventilation line to the intake manifold does NOT violate any such statute, as I fear the previously-proposed dump-tube ventilation of the crankcase to atmosphere would.)

CAUTION: If this modification is performed, a PCV valve MUST be installed in the crankcase ventilation line, for the same reason such a component exists on automobiles: To prevent an intake backfire from migrating to the crankcase, where flammable aerosols may ignite/explode. Further, manifold vacuum will modulate the effective open area of the valve; least when high manifold vacuum exists; greatest when low manifold vacuum is present.

Implementation technique? Off the top-of-my head, I thought perhaps a tubeless tire valve stem might be fitted through a hole in the intake manifold hose, then adapted to the crankcase ventilation line. Alternatively perhaps, one might tap into a carburetor vacuum port.

So, if crankcase vacuum is responsible for the claimed advantages of the PCV valve mod, wouldn't actual connection of the crankcase ventilation line to manifold vacuum enhance and increase crankcase vacuum?

Performing this notional mod would create a Positive Crankcase Ventilation system on a KLR, not unlike on every legal street automobile on the road today.

Postulation only in this post's thrust; comments encouraged and welcomed!
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Old 10-03-2013, 08:11 PM
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Old 10-04-2013, 06:08 PM
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Damocles,
I'll bump this along. And encourage you to DO IT. I've modified my oil system. And I have thought about this issue also.

I'll mention, that IT may or may not affect the carburation.

May I suggest that the OUTLET from the LH or RH side of the camchain cover between the sprockets, have a shield to reduce the possibility of SUCKING OIL.
Set up this way, filtered air from the air box will travel DOWN the existing vent hose and MOIST crankcase vapor could be PULLED from the highest point of the engine. Using a high quality, metal, dirt bike gas cap one-way check valve as the PCV valve.

GO for IT! It is only one little hole in the valve cover, plug-able.
pdwestman

Last edited by pdwestman; 10-04-2013 at 06:18 PM. Reason: LH or RH side
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Old 10-05-2013, 11:08 AM
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Kawasaki has already almost done this once. But it IS NOT a POSITIVE CRANKCASE VENTILATION SYSTEM. An automotive PCV system is a FLOW THRU VENTILATION system!
Neither is the Mercedes Benz valve as used by some on these sites!

Will someone kindly post a picture or parts diagram of the valve cover from a KLX650 (RIP 1993-1996)?
To show the complexity of the air / oil separator chamber.
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Old 10-06-2013, 05:19 PM
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Well, if someone will do a dyno test then we will know but until then I will just leave mine as is.
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Old 10-06-2013, 06:43 PM Thread Starter
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Quote:
Originally Posted by DaveO430 View Post
Well, if someone will do a dyno test then we will know but until then I will just leave mine as is.
You ain't from around here, are you, Dave 0430/Dave O430?

That is, are you familiar with the purported function and effect of the PCV valve mod?

Vast numbers of PCV valve mods have been performed, with no dynamometer data encouraging the modification.

The PCV valve mod is favored by some, celebrated in song and story, but essentially devoid of dynamometer validation (beyond the plausible error budget of dynamometer accuracy/precision/repeatability).

My only point: If "crankcase vacuum" is the primary operational factor producing the alleged desirable effects of the PCV valve mod, wouldn't any crankcase vacuum be enhanced, were the crankcase ventilation line connected to MANIFOLD VACUUM instead of to the neo-atmospheric pressure of the AIR BOX?

Further, I tried to point out above; the purpose of positive crankcase ventilation on automobiles is emissions reduction/pollution control, NOT performance enhancement.
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Old 10-06-2013, 06:53 PM
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Quote:
Originally Posted by Damocles View Post
You ain't from around here, are you, Dave 0430/Dave O430?
I did read the entire thread on it, that's why I said what I did about the dyno test. I do believe in the placebo effect and that's what I see in this mod.
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Old 10-07-2013, 04:42 PM
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This thread makes me smile!

~Things work out best for those that make the best of the way things work out~
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Old 10-07-2013, 06:01 PM
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Ok guy's,
Think MOISTURE EVACUATION?
How many times has this site and others had to EXPLAIN, "milky oil windows"?

I've driven my pick-up mostly, 1.1miles, morning and evening, mostly 6 days a week, for 18 years, NEVER had milky oil! Even in the -20 to -40F. winters.
I could not (CAN NOT) do THAT, with the KLR, in +45 to +70F. spring-fall weather!
pdwestman

Last edited by pdwestman; 10-07-2013 at 06:14 PM. Reason: added (CAN NOT)
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Old 10-10-2013, 01:38 PM
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Quote:
Originally Posted by pdwestman View Post
Ok guy's,
Think MOISTURE EVACUATION?
How many times has this site and others had to EXPLAIN, "milky oil windows"?

I've driven my pick-up mostly, 1.1miles, morning and evening, mostly 6 days a week, for 18 years, NEVER had milky oil! Even in the -20 to -40F. winters.
I could not (CAN NOT) do THAT, with the KLR, in +45 to +70F. spring-fall weather!
pdwestman
There's an Brit who developed a crankcase ventilation system for bikes that uses two free flowing one way valves in two different engine locations to promote air flow into and back out of the case.

Can't remember his name.
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