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Date: Mon, 21 Jun 2010 08:41:51 -0400
Message-ID: <AANLkTilpApBLp0C3nn4eYkVMYvy5C236GsJq6eqVr7DY@mail.gmail.com>
Subject: Oil pressure
From: Lynn Hanover <lehanover@gmail.com>
To: flyrotary@lancaironline.net
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I am running my new turrentine-built 2004 renesis engine without a prop
right now, so no load.  I noticed about 60 lbs oil pressure when first
started, cold.  I made a few runs up to 4000rpm after some warm up and
noticed oil pressure reading more like 40 lbs.  this seems bad.  can I
adjust oil pressure?  what else should I be looking for?

also, what should I put over the oil fill tube?  it is open, with 2 thin
bolts protruding.


KevinLane Carpentry
www.KevinLaneCarpentry.com <http://www.kevinlanecarpentry.com/>

Here is a hyperlink to an oil pressure string on the RX-8 club news group.

You may have noticed that the rotary has the pressure regulator at the end
of the oiling system, where it is more typical to have the regulator in the
pump, or in the block next to the pump.

This does two things. It costs some extra HP and reduces fuel mileage. But
it keeps all of the items in the oil system to be pressurized at least at
the relief pressure, for a very uniform delivery system.  If you regulate
pressure at the pump, the further from the pump each item is, the lower the
pressure. In that regaerd it looks just like the fuel rail with the pump on
one end and the regulator at the other.

Further notice that the pump is not very big displacement wise, and that
leads to low idle speed oil pressure.  On outcome of this arrangement is
that at low RPM you get low oil pressure. You also have the oil holes that
spray cooling oil into the rotors, so you have built in oil leaks. So if the
oil is at opperating temperature and the engine at idle, the oil pressure
can be alarmingly low.

Another item that affects oil pressure is the oil pour weight, and if that
oil is a multi grade oil.

A higher pour weight has the effect of making the fit of the pump parts much
closer to ideal. So, the pump leaks backwards less, and therefore can
produce higher pressure.

The small size means that the regulator will not see enough pressure to
cycle until the pump sees a RPM well above idle. So, rated oil pressure may
not be seen before 3,000 RPM or even a bit more RPM.

So, the low oil pressure you report is at what RPM? Is that a straight
weight oil, or a multigrade?
What is the oil temp when the oil pressure is low.

The Renesis had the FD oil pump, and had problems in the first engines of
the oil pressure light blinking at traffic lights after a bit of a run. This
using the Mazda reccomended street oils.

The oil recommended by Mazda for the car is not what you would want to run
in an aircraft. There is no expectation by Mazda that you would jump into
the car and blast across Texas at wide open throttle every chance you get.

If you premix your top oil, you can use a straight weight synthetic in the
sump. Perhaps even a (Dare I say it?) a racing oil, that has more anti scuff
and anti foaming agents. Or if you use the OMP for top oil, then a straight
weight (Racing?) oil. The straight weight oil is missing the long chain
polymers of the multigrade oils.

The Mistral plane could not get out of the pattern until they took the
multigrade aviation oil out and put in a straight weight motor oil. No more
foaming, much better oil cooling. I talked to the Mistral guy in the engine
tent at Sun&Fun years ago right after he bought the company. Francis I
think? He was very nice but seemed not to know much about rotaries.

The low oil pressure at low RPM and idle is of no concern. The bearings are
way oversized for the stress involved, and so long as there is some pressure
the engine will outlast the pilot.

Of course I could be completely wrong.

Lynn E. Hanover

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<div><font face=3D"Comic Sans MS">I am running my new turrentine-built 2004=
 renesis engine without a prop right now, so no load.=A0 I noticed about 60=
 lbs oil pressure when first started, cold.=A0 I made a few runs up to 4000=
rpm after some warm up and noticed oil pressure reading more like 40 lbs.=
=A0 this seems bad.=A0 can I adjust oil pressure?=A0 what else should I be =
looking for?</font></div>

<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div><font face=3D"Comic Sans MS">also, what should I put over the oil fill=
 tube?=A0 it is open, with 2 thin bolts protruding.</font></div>
<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div>=A0</div>
<div><font face=3D"Comic Sans MS">KevinLane Carpentry<br><a title=3D"http:/=
/www.kevinlanecarpentry.com/" href=3D"http://www.kevinlanecarpentry.com/">w=
ww.KevinLaneCarpentry.com</a></font></div>
<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div><font face=3D"Comic Sans MS">Here is a hyperlink to an oil pressure st=
ring on the RX-8 club news group.</font></div>
<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div><font face=3D"Comic Sans MS">You may have noticed that the rotary has =
the pressure regulator at the end of the oiling system, where it is more ty=
pical to have the regulator in the pump, or in the block next to the pump. =
</font></div>

<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div><font face=3D"Comic Sans MS">This does two things. It costs some extra=
 HP and reduces fuel mileage. But it keeps all of the items in the oil syst=
em to be pressurized at least at the relief pressure, for a very uniform de=
livery system.=A0 If you regulate pressure at the pump, the further from th=
e pump each item is, the lower the pressure. In that regaerd it looks just =
like the fuel rail with the pump on one end and the regulator at the other.=
</font></div>

<div><font face=3D"Comic Sans MS"></font>=A0</div>
<div><font face=3D"Comic Sans MS">Further notice that the pump is not very =
big displacement wise, and that leads to low idle speed oil pressure.=A0 On=
 outcome of this arrangement is that at low RPM you get low oil pressure. Y=
ou also have the oil holes that spray cooling oil into the rotors, so you h=
ave built in oil leaks. So if the oil is at opperating temperature and the =
engine at idle, the oil pressure can be alarmingly low.=A0</font></div>

<div>=A0</div>
<div><font face=3D"Comic Sans MS">Another item that affects oil pressure is=
 the oil pour weight, and if that oil is a multi grade oil.</font></div>
<div>=A0</div>
<div><font face=3D"Comic Sans MS">A higher pour weight has the effect of ma=
king the fit of the pump parts much closer to ideal. So, the pump leaks bac=
kwards less, and therefore can produce higher pressure.=A0</font>=A0</div>
<div>=A0</div>
<div>The small size means that the regulator will not see enough pressure t=
o cycle until the pump sees a RPM well above idle. So, rated oil pressure m=
ay not be seen before 3,000 RPM or even a bit more RPM.</div>
<div>=A0</div>
<div>So, the low oil pressure you report is at what RPM? Is that a straight=
 weight oil, or a multigrade?</div>
<div>What is the oil temp when the oil pressure is low. </div>
<div>=A0</div>
<div>The Renesis had the FD oil pump, and had problems in the first engines=
 of the oil pressure light blinking at traffic lights after a bit of a run.=
 This using the Mazda reccomended street oils.</div>
<div>=A0</div>
<div>The oil recommended by Mazda for the car is not what you would want to=
 run in an aircraft. There is no expectation by Mazda that you would jump i=
nto the car and blast across Texas at wide open throttle every chance you g=
et.</div>

<div>=A0</div>
<div>If you premix your top oil, you can use a straight weight synthetic in=
 the sump. Perhaps even a (Dare I say it?) a racing oil, that has more anti=
 scuff and anti foaming agents. Or if you use the OMP for top oil, then a s=
traight weight (Racing?) oil. The straight weight oil is missing the long c=
hain polymers of the multigrade oils. </div>

<div>=A0</div>
<div>The Mistral plane could not get out of the pattern until they took=A0t=
he multigrade aviation oil out and put in a straight weight=A0motor oil. No=
 more foaming, much better oil cooling. I talked to the Mistral guy in the =
engine tent at Sun&amp;Fun years ago right after he bought the company. Fra=
ncis I think? He was very nice but seemed not to know much about rotaries.=
=A0</div>

<div>=A0</div>
<div>The low oil pressure at low RPM and idle is of no concern. The bearing=
s are way oversized for the stress involved, and so long as there is some p=
ressure the engine will outlast the pilot.</div>
<div>=A0</div>
<div>Of course I could be completely wrong.</div>
<div>=A0</div>
<div>Lynn E. Hanover</div>
<div>=A0</div>
<div>=A0</div>

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