[Diy_efi] crankcase vacuum control

[Jack Vines]

Greetings, Adam,

The crankcase pumping losses are real when a crankcase has positive
pressure, which can happen, especially on a high-boost, high-rpm turbo
engine.  That is why dry-sump systems have as many as 4-5 scavenge stages
and only one pressure stage. It becomes a vacuum pump and maintains a vacuum
in all parts of the engine.  It helps rings seal as well, by increasing the
pressure differential between top and bottom sides.

thnx, jv. 

-----Original Message-----
From: Adam Wade [mailto:espresso_doppio at yahoo.com]
Sent: Saturday, April 26, 2003 5:47 PM
To: List for general do-it-yourself EFI talk
Subject: RE: [Diy_efi] crankcase vacuum control


--- Jack Vines <jackv at ambassadorprograms.org> wrote:

> You can pick up 30-40hp on a strong engine through
> reduced pumping losses.  The pistons don't have to
> compress the crankcase atmosphere on their way down.

But they have to fight the vacuum on the way back up.

Frankly, I have never bought this as a source of
power, and there has yet to be a scientific
explanation that "washes", IME.  I'd love to hear one,
but this ain't it, I don't think.

> The most important factor for turbos is it keeps the
> oil out of the combustion chamber and thus helps
> prevent detonation under high boost.

How does oil get into the combustion chamber?  Through
the airbox?  That can be eliminated with a simple
crankcase vent filter, and elimination of the hose
between crankcase and airbox.

=====
| Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
|   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
| "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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