[s-cars] Crank Case Pressure and Turbo Smoke?

[Trevor Frank]

Oh ya and believe it or not there is some HP to be made by having vacuum
in the crank case. Porsche would flow the inside of there cases and even
polish them they found 6hp on a 200hp motor at 8k rpm.  Vacuum pumps
will make sure that the air friction is reduced and it would not be a
far step to say that if it where legal Porsche could have recovered even
more hp.  So it isn't to far to assume that aside from all the other
benefit's there is actual hp to be gained by having vacuum in the crank
case.  Many spec motors in racing that are allowed to use a dry sump set
up will have small trick like a miss balance of oil return volume as
apposed to oil inlet volume to generate vacuum in the crank case.  There
is a reason that vacuum pumps are not legal in many forms of
racing...it's an unfair advantage, where they are allowed they are used.

-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of Trevor Frank
Sent: Wednesday, February 23, 2005 12:16 PM
To: Djdawson2 at aol.com; t44tqtro at gmail.com; s-car-list at audifans.com
Subject: RE: [s-cars] Crank Case Pressure and Turbo Smoke?


Sorry, but I will have to disagree here, there are lots of reasons not
to vent into the motor, so there are lot's of reasons to vent some other
way..either to atmosphere or into a vacuum pump or into the exhaust.
For me the issue was always about keeping blow by gasses and more
importantly oil out of the intake track, I have seen to many failures of
a motor due to oil in the intake.

Blow by gasses are corrosive and will degrade the oil in the motor.
Virtually any air oil separator will still allow some small amount of
oil past is and if nothing else the dreaded blow by gasses back into the
intake, filled with incombustibles and displacing clean cool air.  Oil
in the intake track can lead to oil in the combustion chamber, this can
lead to detonation, pre-ignition etc...and I have seen it lead to
catastrophic failure of the combustion chamber, blowing holes thru
stuff. 


So a good air oil separator should keep the intake trac clean.
Venting to atmosphere will keep blow by gasses out of the intake tract.

Using a vacuum pump on the vent line will give you vacuum in the crank
case and help keep the rings from floating, the motor from leaking etc.

Venting appropriately to the exhaust will also generate vacuum.

There are also lot's of reasons to have vacuum in the crank case so if
you decide to vent to atmosphere then you are also deciding not to have
vacuum..at leas at some point on the outlet, we can argue if you
actually get any into the crank case with what is generated between the
maf and the turbo at times.

Initially I just put a K&N on the valve cover, but after improving the
suspension, better tires and racing at a few banked tracks I did start
to see some oil vent out of it.  So I went to an air oil separator with
an oil return to the crank case.  This ended any oil getting out of the
air filter, still venting to atmosphere.  My next step would be to use
an egr valve and vent into the down pipe, at a 45 deg angle with an
appropriate tube to generate some fractional amount of vacuum.  Past
this using a purpose made vacuum pump would be a good idea.



-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com] On Behalf Of Djdawson2 at aol.com
Sent: Tuesday, February 22, 2005 9:23 PM
To: t44tqtro at gmail.com; s-car-list at audifans.com
Subject: Re: [s-cars] Crank Case Pressure and Turbo Smoke?

In a message dated 2/22/2005 8:24:00 PM Mountain Standard Time,

t44tqtro at gmail.com writes:

> Can you all please clarify- is an air/oil separator sufficient to
> resolve the problem of oil going into the intake, or is a vent really
> needed?

The issue we've been discussing hasn't been so much control of oil going
into

the intake... but rather, keeping the crankcase from seeing pressure.

> I definitely installing a catch can/separator, but am hesitant to
> install a crankcase vent due to emissions legality issues- we have
> emissions testing, can't run afoul or can't drive the car.
>


There's really no reason to vent it to atmo... unless you need the
chrome.
Dave
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