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Date:         Thu, 10 Jan 2008 12:20:34 -0800
Reply-To:     neil N <musomuso@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         neil N <musomuso@GMAIL.COM>
Subject:      Re: oil pump blueprinting question
Comments: To: Mike S <mikes@flatsurface.com>
In-Reply-To:  <20080110154019.C1E5E1165C3@hamburg.alientech.net>
Content-Type: text/plain; charset=ISO-8859-1

Interesting to read Bob Hoovers' post Mike.

Thanks!

Neil.

-- Neil Nicholson. 1981 Air Cooled Westfalia - "Jaco" http://web.mac.com/tubaneil

Engine swap beginings: http://tubaneil.googlepages.com/

On 1/10/08, Mike S <mikes@flatsurface.com> wrote: > At 08:21 AM 1/10/2008, Giasson, Pascal (DNR/MRN) wrote... > >I have my old OE oil pump out and I noticed that the pump outlet > >port/hole is smaller that the receiving hole in the case...If I > >enlarge the outlet port on the pump then I would guess that the oil > >pressure inside the pump might be reduced, but what will that do to > >the oil presser elsewhere. If port matching is ideal then why did VW > >not do this in the first place? > > To "blueprint" is to exactly match factory specifications, correcting > for the allowed tolerances (i.e. if the factory spec is a 12mm +- 1mm > hole, you would want an exact 12mm hole). Also, gear clearances, > endplay, etc. Having said that, it's common for people to refer to > performance modifications as "blueprinting." Here's what Bob Hoover has > to say on the matter: > http://groups.google.com/group/rec.autos.makers.vw.aircooled/msg/20cb7f6f86953f1b > > Suction ports will normally be larger than pressure ports. You can only > have a suction differential equal to the crankcase pressure, which is > slightly more than atmospheric, so a bit over 1 bar (15-16 psi). The > pressure side can be arbitrarily high, but VW considers 0.9 bar an > absolute minimum at 2K RPM. It should normally be significantly higher. > The greater the differential, the smaller the hole required to support > the same flow. > > Changing the outlet size should have little effect on the oil pressure > on a stock engine, which is determined almost entirely by the delivery > rate of the pump (volume per revolution), viscosity of the oil, and the > various clearances in the engine. > > If you want more oiling, look for a high volume pump, not bigger ports. > But be careful, the stock pump has sufficient capacity and high volume > pumps can create so much pressure that the pressure reliefs can't > properly do their job - it can cause the oil cooler pressure relief > valve to stay open, causing less cooling. You might also blow oil > galley plugs or oil filters. > > Overall, for a stock engine, I don't think port size matters, nor do > you need a larger pump. The only "blueprinting" needed is checking oil > pump clearances (probably need to use plastigage for checking endplay > on a T4 pump). >


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