Date: Sat, 20 Apr 2002 15:41:12 -0400
Reply-To: "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Organization: Bulley-Hewlett
Subject: Re: Ethnicity of Oil Pressure Switch
In-Reply-To: <000501c1e89d$9c535120$6202a8c0@dadspc>
Content-Type: text/plain; charset="US-ASCII"
There's a common misconception that "more/higher" oil flow/pressure is
good, and that very low oil pressure is a precursor to a tortuous
disaster awaiting your motor. However, this isn't true.
There is a certain "window" of good oil pressure, dependant on motor
speed and load. Too low is not good, too high is bad.
At no load, you can idle a VW type 1 or Type 4 motor for a VERY long
time (hours, or perhaps days) with almost nearly no oil pressure (.1 -
.2 bar) without serious damage. I've seen worn out bug motors that have
a great-looking bottom end, and nearly 0 oil pressure at idle, but they
aren't in for an oil-related failure.
At normal speed/load however, your bearings are crushing toward their
saddles far harder, and need a pressurized cushion of oil to prevent
bearing scoring or overheating. Higher oil pressure is required at
speed, thus the oil pump is driven directly from the cam.
On the other hand, if your oil pressure/flow is too high, you stand the
risk of blowing out seals, bursting your oil cooler, wasting fuel, and
lowering performance. Yep, that's right, your oil pump is an accessory,
which derives its power from the spinning crank. Since it is essentially
a hydraulic pump, and it is forcing oil essentially through a closed
system, its load on the cam can be quite high.
I've never done the math, but I would guess it draws in the 1 - 2 hp
range on a normal motor. If you artificially increase the oil pressure
(bigger pump, tighter relief springs) you will see a drop in
performance. Been there, done that on my former 914. all a bunch of
FYI...
Developing business and guiding change since 1996,
G. Matthew Bulley
Bulley-Hewlett
Corporate Communications
Business: www.bulley-hewlett.com
Alliance: www.ntara.com
Phone: +1.919.658.1278
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of Dennis Haynes
Sent: Saturday, April 20, 2002 3:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Ethnicity of Oil Pressure Switch
Once the oil is hoot, the engine will not reliably hold 29 psi at 200
rpm. These engine typically hold 10-12 PSI for each 1000 RPM using 20-50
oil once the oil is over 220. The 1.8 switch will work if the oil temps
stay low and the engine is new, but it will give nuisance alarms during
certain conditions.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Ben huot
Sent: Saturday, April 20, 2002 1:09 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Ethnicity of Oil Pressure Switch
Hi,
The minimum oil pressure at 2000 rmp (By Bentley spec, is Bentley
right!!!)
is 2 BAR (29PSI). Why do we have a.9 BAR (13PSI) as minimum pressure
alarm
/ switch??? It does not make sense, the minimum should be at least 1.5 -
1.8 BAR (What is minimum?)
Get a damn oil pressure gauge!!!
Yea, Bentley is a big book full of it!!!!! In a 10-page section on the
lubrification subject, no mention of the oil pressure at freeway
speed????????????????????
Regards, Ben
http://www3.sympatico.ca/huotx/engine1.htm
