[Diy_efi] Venturi effect crankcase breather

[Adam Wade]

--- arnie <arnie_ at charter.net> wrote:

> More than a fairly small drop in pressure..., how
> small of a drop in pressure? 

We did not discuss actual numbers, as he was not at
liberty to do so.  He did indicate that running an
open exhaust on a motorcycle would allow one to exceed
that level of pressure drop.  How much it will alter
the life of the engine is anyone's guess, and I am
sure it depends on the materials used in a particular
engine.

> Being closer related to the motorcycle industry, I
> reason that you would be more familiar with this.
> Though it is referred to as a 'compression' ring,
> it's main function is to control oil.  A one
> compression ring (along with conventional oil ring)
> has been used successfully for many years
> (decades ?) especially in the motorcycle camp.  

It's been used almost exclusively on two-stroke
motors, where there is no oil control needed (when
using crankcase induction), and friction is a huge
enemy.  Very few four-stroke bikes use only one
compression ring.

> OEM (as well as aftermarket) has been prescribing
> (and using) larger gapped second rings for a decade
> that I am aware of.

What constitutes a "larger gap"?

> This aids in the compression sealing of the top
> ring, by preventing pressure buildup below top
> compression ring.     

Where is this pressure coming from?  If both
compression rings have the same sealing
characteristics, then there should never be a build-up
of pressure between the two.  Further, since
compression pressure is what seals the top compression
ring, and it is absent from the second ring, the
second ring should not seal nearly as well as the top
ring, regardless.


=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
| "It was like an emergency ward after a great catastrophe; it  |
|   didn't matter what race or class the victims belonged to.   |
|  They were all given the same miracle drug, which was coffee. |
|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |

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