[urq] Too much Crankcase ventalation?

Ben Swann benswann at comcast.net
Wed Sep 5 11:44:06 EDT 2007

So no connection to manifold pressure/vacuum?

I was contemplating a catch reservoir with draincock at bottom - two fittings
at top - one to vent out crankcase and valve cover and the other to small
filter and/or slight draw from Intake using one way valve and restrictor.
This way any oil would be collected and observed, but would retain some PVC
benefit - just not too much.   Thinking...thinking..


-----Original Message-----
From: cody at 5000tq.com [mailto:cody at 5000tq.com] 
Sent: Wednesday, September 05, 2007 8:49 AM
To: Ben Swann
Cc: s-car-list at audifans.com
Subject: RE: Too much Crankcase ventalation?


Just use the MC crankcase vent hose that goes to the metal pipe, then  
it attaches to the T hose that fits on the valve cover, then stick a  
mini K&N filter availible at your FLAPS on the other end of that T hose.


Quoting Ben Swann <benswann at comcast.net>:

> Thanks for all the replies.  Before going further, it would be good to know
> more about the engine:
> The engine installed in '83 Ur Quattro is MC-1 rebuilt with align-bored
> block/crank with 1 size-over main bearings, piston assemblies balanced to
> nearest gram.  Reworked NF head 42I 38E valves and stock MC-2 cam   
> has external
> aux. water manifold.  Intake manifold and throttle body are from WX engine,
> dual-piece exhaust manifold, UrQ downpipe to 2.5" exhaust with free-flow
> K-24 turbo, Bypass valve is oriented to blowoff to turbo intake after filter
> and forced air intake is being fabricated to fit car.  Using stock UrQ
> intercooler for now.  Engine is being managed by separate ignition and EFI
> computers - MAC-14 with dual knock sense ignition and most CIS components
> deleted, and Megasquirt V2.2 EFI with MSExtra code pushing fuel through 38lb
> injectors (for now).  Engine is mated to 5000 Quattro transmission using
> single-mass 3B flywheel setup.  Engine has baffled oil pan from 7A.
> Frankenmotor indeed, but intention is to put together a durable high-rev.
> I5 engine that fits car well and retains original look/layout as original
> motor.
> OK - back to the XS crankcase/camcover vent issue - this is surely   
> what it is,
> and Scott helped bring it to light with his questions.  I'd rather not
> and implement a catch-can system yet although it is something possibly to
> consider if I push boost over 2.5 bar.   I would like to know how I can
> regulate things so it just isn't trying to suck the outside in at   
> idle or blow
> insides out at full boost - slated to be 2.5 in the near future, but need to
> do basic tuning first.
> In answer to Scotts ?'s below re. how it is plumbed, it seems I my   
> have things
> a bit too simplified right now and I would not even consider present  
>  hookup to
> be "PVC".  Basically there is direct connection using a stock hose   
> between cam
> cover, intake manifold and crankcase.  So I surmise that whatever manifold
> pressure is, it is the same inside the camcover, and crankcase as well.  Big
> oversight I suppose or more like, just getting things to work as they should
> after the car has been down for nearly a year.
> As I explore my boxes of doodads and valves, I'd appreciate entertaining any
> good suggestions on a simple means of having just a little vacuum in the
> crankcase and cam area when under negative pressure and very little if any
> postive pressure in the cam/crankcase area when under boost.  Or   
> perhaps there
> should be just a slight bit of pressure made inside the engine - blowby etc.
> that is allowed to vent, but be recovered "gracefully" into the intake.
> engine is new and should be very tight.  The noise goes away when vacuum is
> relieved in the cam cover area, so hopefully not to difficult..
> Catch can recovery system is not outside the question of future mods, but
> certainly outside the scope for the immediate needs as best as I can tell.
> TIA for suggestions even on how to make a simple catch can and drainback.
> Ben
> -----Original Message-----
> From: QSHIPQ at aol.com [mailto:QSHIPQ at aol.com]
> Sent: Tuesday, September 04, 2007 8:58 PM
> To: quattro at audifans.com; urq at audifans.com
> Cc: benswann at comcast.net
> Subject: Re: Too much Crankcase ventalation?
> Ben
> Congrats on getting it running, missed the actual fix, since I was
> staring at the non-run status on my visit earlier this  spring...  WRT PCV,
> by default, on several add on turbo/supercharger  systems over the   
> years, I've
> been initiated fully into this mysterious  dark world of vacuuming
> dynosuar-scum we call PCV.  First, that's a  lot of vacuum!  I thought 14in
> with my
> re-gifted blue urq was a  lot.  I suspect you are actually creating so much
> that
> your squeal may be  the seal whistle as it finds more free air source.
> look at the stock  system, then look at what EFI does to it.
> The stock urq uses a combined breather/low vacuum setup with a manifold
> valve.  When the urq is not under boost, the PCV routing goes from the
> crankcase
> to the head, and then directly into the manifold.  When the urq  is under
> boost, the PCV routing goes from the crankcase to the head, and then to  the
> igloo
> (PCV valve at manifold is closed).  This allows a mild vacuum  source under
> boost, keeping pressure from building in the crankcase under  sustained
> load (trailer/mountain/high GVWR).
> Looking at the above, with a stock urq you have a maximum vacuum of  14in at
> idle at sea level (most urq's IME see around 12in - I have the euro  head
> cam which puts it higher).  Ok, that's baseline, now add in EFI  with the
> stock PCV...
> What did you do with the breather/low vacuum line with the EFI setup?   My
> guess is that with increase vacuum, you need to increase port size on the
> breather, and possibly decrease port size on the manifold valve.  What  I've
> learned over the years, is that slight changes to designed PCV   
> vacuum  sources
> can
> really affect how the PCV works or specifically doesn't.  For  instance,
> times I've seen restrictors inserted into the igloo breather  line, that
> actually caused too much pressure in the system.  The last one I  saw this
> with on
> an urq, actually blew oil out the turbo seals because the  pressure was too
> high on the gravity return of the turbo oil.  Here, you  are experiencing
> opposite problem...
> With vacuum too high, you will overload the breather line capacity, and the
> vacuum in the crankcase and head will be excessive.  You equalized the
> breathing by removing the oil cap, which means you need to either   
> add a bigger
> breather, or add an additional breather until you get the right equalization
> of
> engine manifold vacuum to engine crankcase vacuum and/or restrict the size
> the PCV valve ID at the intake manifold.  I tend to favor chasing smaller
> vacuum feed ports to larger breather ports first, because vacuum   
> leaks tend to
> become more significant as the amount of vacuum increases.  To this end,
> can replace the PCV valve with one out of a later turbo car (an  upright
> and valve type vs the diaphram type the urq uses).  Once  under   
> boost however,
> you need to make sure you have a constant low vacuum source  to keep
> pressure in the crankcase, without blowing oil out the valve  cover gasket.
> Ben, it's a dance for sure, but the very last thing I would do, is go catch
> can.  IMO/E, that's an 'nth' power mod on a full out race car that has
> optimized VE in every other respect.  Or, if you are running really high
> boost
> levels, it can increase the amount of air vs oil vapor.  But, as a  general
> rule,
> I run PCV closed loop whenever possible.  It's easy to run a  catch can,
> harder to design a proper sized PCV system.  In my opinion  catch cans are
> mostly used to avoid the harder design of doing it  properly.  Which means
> definition a catch can would be catching more  than a properly   
> designed closed
> loop PCV circuit.
> HTH and my .02
> Scott Justusson
> QSHIPQ Performance Tuning
> Chicago
> In a message dated 9/4/2007 3:34:09 P.M. Central Daylight Time,
> benswann at comcast.net writes:
> am finally able to drive the Ur Quattro that has  the new engine with
> Megasquirt - Yeah!.  Engine is balanced MC-1 with NF  head.  I am now tuning
> it, so it will get better and better, but  starting way rich, and trying to
> figure creative ways to tune since I don't  have ready access to a   
> dyno.  I'll
> probably need to have someone drive  as I make changes to the VE   
> tables, etc..
> Ideas?
> Anyway, after  my first extended tuning session and the engine was   
> on the warm
> side, I  noticed a nasty squeal almost like a loose belt when the engine
> idling.  I feared the worst as it seemed to be coming from the head  and
> sounded a little like a metal machining noise, but went away when I  gunned
> the
> engine.  Oil level was good - still on the Havalone break-in  crap.
> I pulled the oil cap and the noise went away with a release  of some serious
> vacuum.  I repeated this experiment only to conclude  that there is so much
> vacuum on the head at idle, that it is probably  evacuating the cam   
> bearing or
> something to that effect.  If I left the  cap loose, the noise did not come
> back, each time I tightened the oil cap,  the noise cam back in a   
> few seconds.
> I have the UrQ PVC hose setup, but so  much is removed of the CIS   
> stuff, there
> is fairly much a direct draw into the  Intake manifold and the engine is
> pulling a good 18-20 lbs of vacuum at  idle.
> So just seeing if there is any solution to this.  I  would expect I should
> have
> some ventilation in the cam area, but this is too  much.  Ideas?
> Ben
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