[s-cars] Bypass valves - Which one?

[Trevor Frank]

Here is a good story,
Honda, the great copiers they are, bought all of the current motorcycles
back in the day before they built theirs.  They took them all apart,
meticulously and labeled every part on large white sheets.  As for the
motor they picked the best top end and bottom end from two different
manufacturers.  The first motors they built kept on blowing out seals,
and they had issues with rings sealing.  Turn's out they took a bottom
end from a company who's top end had a breather, and a top end who's
bottom end had the breather.

I am pretty sure Mihnia was suggesting that he was returning the oil to
the crank case but still venting the blow-by from the crank case.

We need to vent the gas, negative pressure in the crank case is a good
thing.  I suspect that there is a descent amount of negative pressure
that is proportional to the boost pressure in the boot between the turbo
and the maf.  This is a good thing, to have a descent source of negative
pressure.  The problem is feeding it back into the engine.  I currently
let it bleed into the air though a filter.  I suspect you could improve
the conditioning of the air that gets led back into the intake with some
kind of Air Oil Separator.  But I would be wary of this, it may not
destroy your engine but ultimately you should be loosing some hp, and
probably have to back off you ignition advance over not venting it in.
I may be splitting hairs, I don't know.  I have been trying to help
Brian B with his issue, and I suspect that he will be using some kind of
Centrifugal air-oil separator with an oil return back into the pan.  For
$20 BMW has a descent one they use on the M5 that may work, Brian is
going to try it out soon.  I wish I knew why some people have this
problem and others don't, excessive oil coming from the crank vent.  It
isn't a HP thing, I really wonder if it isn't and indication of some
small malfunctioning part in the breather system.

For a stock car or nearly stock, let's say, guessing, somewhere under
380 hp at the flywheel, you may be o.k. with venting it back into the
intake.  You should benefit from a properly implemented air oil
separator, even better if it vented oil back to the crank case.  For
really high hp motors I suspect you are gambling if you vent back to the
intake.  Under the right conditions apparently these motor's, like
Brian's and others can and will vent a lot of oil.  Put this into your
combustion chamber, like cylinder 4 and 5, they seem to be a strait shot
for a high mass particle and watch your electrodes explode on your spark
plug, soon your cylinder head gasket and maybe your head.  Detonation,
like a prison bride is an ugly thing.


-----Original Message-----
From: tblack [mailto:Tblack5 at cogeco.ca]
Sent: Monday, December 08, 2003 12:50 PM
To: QSHIPQ at aol.com; Trevor Frank; russ at panneton.name;
pizzoman at yahoo.com; Mihnea Cotet
Cc: CaptMagu at aol.com; s-car-list at audifans.com; gary.m.lewis2 at BOEING.COM
Subject: Re: [s-cars] Bypass valves - Which one?

Guys, By returning the oil to the sump implies a closed system, as per
Mihnea's comment re: UK S2. Should there not be a means of exhausting
the
pressure build-up in the crankcase? It seems highly desireable to not
vent
to the intake system as is the case with our cars. What is the solution?
Tom Black.

----- Original Message -----
From: "Mihnea Cotet" <mik at info.fundp.ac.be>
To: <QSHIPQ at aol.com>; <tfrank at symyx.com>; <russ at panneton.name>;
<pizzoman at yahoo.com>
Cc: <CaptMagu at aol.com>; <s-car-list at audifans.com>;
<gary.m.lewis2 at BOEING.COM>
Sent: Monday, December 08, 2003 2:30 PM
Subject: Re: [s-cars] Bypass valves - Which one?


> Yup Scott, agreed, but what about using a catch tank with a return
line to
> the oil pan??? A friend of mine from the UK with a 400 HP S2 has done
that,
> the idea is excellent as the oil consumption is reduced to almost
nothing
> (barely what gets burnt in the chambers due to tired piston rings).
>
> Just a thought...
>
> Mihnea
>
> At 14:20 8/12/2003 -0500, QSHIPQ at aol.com wrote:
> >Actually Minhea, small amounts of oil, even in vapor form, are enough
to
make
> >a difference.  In vapor form, it's now part of your 'Air' in the A/F
ratio.
> >Given what I see in perfectly good CIS cars with wet oil PCV, I'm not
with
> >your conclusion.  Oil also tends to help exacerbate hotspots in the
> >combustion
> >chamber.
> >
> >Put another way, when you see perfectly good I5's at the track
emptying a
> >quart of oil from a catch can per day, where would that oil go
without
> >one?  Ever
> >wonder why at track events, oil consumption reaches extremely high
levels
in
> >a perfectly normal S car?  I don't.  I might add that reducing the
> >aeration of
> >the oil is key as well (read:  Big oil coolers = good).  For more on
this
SAE
> >970922  Development of Modern Engine Lubrication Systems - coauthored
by
Uwe
> >Geiger Audi AG
> >
> >SJ
> >
> >
> >In a message dated 12/8/2003 1:10:03 PM Central Standard Time,
> >mik at info.fundp.ac.be writes:
> >Though, with regards to detonation/pre-ignition, I guess it would
take
> >$hitloads of oil puking through the breather in order to produce
> >detonation, but then it would mean that the engine is so FUBAR that
it
> >doesn't need to have any performance anymore...
>
> _______________________________________________
> S-CAR-List mailing list
> S-CAR-List at audifans.com
> http://www.audifans.com/mailman/listinfo/s-car-list


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