X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-gx0-f180.google.com ([209.85.161.180] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4542987 for flyrotary@lancaironline.net; Tue, 26 Oct 2010 14:12:14 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.180; envelope-from=wdleonard@gmail.com Received: by gxk8 with SMTP id 8so4111628gxk.25 for ; Tue, 26 Oct 2010 11:11:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=AycyJ4uiNFnRoI87jfyfVNymmLmWEvY3T/DRNZHbZuc=; b=CXt2hMl8We8DRXY0sQCWV37u3DwSGA+eQLdbWoJ68xtkSWVrB74yQ/sXHNen2EB3Ms bV8+k5gYSaWfoXM+sCG+jUkqp5q4Q/TlzYFGDylN5KUCELEeZAyx0Z4Uk65mb9gNCuyq PP4nIVQlm22dzt3XEl5TTiZoK8b/TReiwSldc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=gDd5M0Msv/gHprsqUr8D+1KZ897d5o2JozHAtfsHP3u6xSq7khotP3Sxgla+5KRe/9 WMJgIKFxiRCFfsUgrRPeDnMhNI0Baz9jiDTGGcFGfvRE6vf8R/nhd9xk5IQbZvldUY79 HKPl/kqMVFRPkA0LqQJgN7R5LHFmHA34dx5VA= MIME-Version: 1.0 Received: by 10.42.223.132 with SMTP id ik4mr1667944icb.163.1288116700375; Tue, 26 Oct 2010 11:11:40 -0700 (PDT) Received: by 10.231.32.13 with HTTP; Tue, 26 Oct 2010 11:11:40 -0700 (PDT) In-Reply-To: References: Date: Tue, 26 Oct 2010 11:11:40 -0700 Message-ID: Subject: Re: [FlyRotary] Re: Oil pressure change... Careful! From: David Leonard To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=20cf30549e555aecad0493890ad1 --20cf30549e555aecad0493890ad1 Content-Type: text/plain; charset=ISO-8859-1 They are not really "pop" off valves. (a valve that closed, then switches to nearly open at given pressure). Those are regulators. They are continuously flowing a variable amount of oil to keep the pressure withing the specified range. If the pressure is not reaching the minimum of that range, there is SOMETHING wrong with the system and it needs to be found... a leak, bad pump, stuck regulator, bad pickup, uncalibrated sensor, etc.. (see Lynn's list in a much earlier post) Why does the pressure go up with thick oil? Because it is more viscous=more resistant to flow. If there were no regulators in the system, then the flow through the engine would be the same either way. But in no case would the flow increase to the engine(higher pressure just means higher pressure). If there is a leak somewhere, then there is just more oil flowing through the leak instead of into the engine. That is especially true with the spring loaded regulators.. higher pressure means that the spring opens preferentially. -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net On Tue, Oct 26, 2010 at 10:48 AM, Dave wrote: > If the pressure does not exceed the minimum of the pop-off valves on the > front or back irons, then how is the volume of oil reduced? > > > > On 10/26/2010 12:44 PM, David Leonard wrote: > > Chris, > > Regarding the oil pressure, I just wanted to remind you of one thing. The > reason that the oil pressure goes up with thicker oil, is because less of it > is flowing through the engine and more is going out the regulator. > > I submit that it works like this: the oil gets thicker, it does not flow as > easily anywhere although the pump still puts out the same amount of oil, > that causes the pressure to go up, which opens the regulator a little more > than it was when the pressure was lower, this causes a HIGHER PERCENTAGE of > the total flow to go through the regulator instead of into the e-shaft. > Since the total flow remains the same as when the pressure was lower (for a > given RPM, the result is a net reduction in flow to the e-shaft. while it > is probably true that the thicker oil will lube the bearing better, so not > as much might be needed, don't forget that most of the oil going into the > e-shaft is going to cool the rotors. And a reduced amount of thicker oil is > not going to cool nearly as well as a higher amount of thinner oil. > > There is obviously a balance/optimum oil thickness, and the manufacturer > probably knows best by suggesting a particular thickness of oil. As we say > in medicine, don't go chasing after lab numbers (which is what oil pressure > really is). If you felt your oil pressure was too low you want to find the > underlying cause rather than make it look better by thickening up the oil. > If I had a patient who was severely anemic I could make the blood count look > better by giving transfusions, but I might be missing the life threatening > GI bleed. > > Oil pressure too low? think of all those things on the list that Lynn sent > out. Think that your application warrants a higher oil pressure? Then > install stronger springs in the regulator and keep that oil flowing through > the engine rather than rob the engine so you have a nice pretty number on a > gauge. > > And it appears that keeping with the regular weight oil will save some $$$ > as well. > > -- > David Leonard > > Turbo Rotary RV-6 N4VY > http://N4VY.RotaryRoster.net > http://RotaryRoster.net > > > On Tue, Oct 26, 2010 at 6:50 AM, Chris Barber wrote: > >> Since my oil pressure was down a bit following my pressure repair I >> decided to take heed or some of the comments regarding one of the possible >> causes as presented here. It seemed to be the easiest that I could try. >> >> So, I shelled out the bucks for some Royal Purple 50 (actually, 20/50 >> IIRC). Geezh, I thought the 30 weight and 40 weight was pricey at $8 and >> $10 a quart, this stuff was $16.00 a quart. I drained about 2 to 3 quarts >> out of the pan and out of the filter and replaced it with the 50 wieght. >> So, now it was a blend of the 30 and the 50. I cranked up the engine and my >> oil pressure was up by about 10-15 psi. WOW! I did not expect such a >> dramatic increase. I had just run the engine earlier (before I went >> and purched the oil). Before the change, my idle pressure was around >> 28-30. After the change it was in the low 40's. The most psi I was >> getting before the change was about 50-55 psi at 6300 rpm. After the >> change it was at about 72 psi at 6300. >> >> I let her idle for about ten minutes and all seemed good. So, since my >> temps seemed good and steady now that Outside air Temps were have now dipped >> down into the low 90 I decided to taxi around a bit. Yep, I sometimes enjoy >> taxiing around in my very expensive go-cart. >> >> The engine was running sooooo smooth and strong. I was feeling pretty >> damn good about it all. Since I was moving around on the ramp where there >> was quite a bit of traffic following this weekends big 'ol Wings Over >> Houston air show, I reached down and switched on my nav/strobe lights. At >> the exact instant of turning on the light (which, btw, are on my secondary >> alternator circuit) the engine started faltering and wanting to stall out. >> WTF!!! I switched to the B computer and things smoothed out. Back to A and >> had to add throttle and mixture to keep it running and it was still rough. >> Back to B to make it back to the hangar. >> >> Once back at the hangar, I checked the MAP table (RWS EM2, btw) and >> nothing seemed changed from earlier. Kinda sounded like fuel was having >> trouble getting to the injectors. I would think to look at the injectors >> first, but am not inclined to focus here too much since the engien smoothed >> out when changed to the B computer. Since both computers use the same >> systems, it seems to be isolated to the primary computer. Please, correct >> what I am missing here. Since my judgment was clouded with anger, I put >> everything back in th hangar for the night. This good good bad good bad >> stuff is taxing and discouraging. I feel I am so close, then this >> nonsense. (on top of my RPM's cutting out around 6000 rpm - can slowly inch >> it up to 6300, with power to spare- if I go slowly, but cuts out at rpm over >> 6300 and change on the EM2 and an EGT reading issue). To quote >> Mork....."Heavy sigh". >> >> Trying to wrap my head around where to start on this latest PITA gremlin. >> It had been running as close to perfect as I could have imagined. >> >> All the best, >> >> Chris Barber >> Houston >> > > > > > --20cf30549e555aecad0493890ad1 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
They are not really "pop" off valves. (a valve that closed, = then switches to nearly open at given pressure).=A0 Those are regulators.= =A0 They are continuously flowing a variable amount of oil to keep the pres= sure withing the specified range.
=A0
If the pressure is not reaching the minimum of that range, there is=A0= SOMETHING wrong with the system and it needs to be found...=A0 a leak, bad = pump, stuck regulator, bad pickup, uncalibrated sensor, etc..=A0 (see Lynn&= #39;s list in a much earlier post)
Why does the pressure go up with thick oil?=A0 Because it is more visc= ous=3Dmore resistant to flow.=A0 If there were no regulators in the system,= then the flow through the engine would be the same either way.=A0 But in n= o case would the=A0flow increase to the engine(higher pressure just means h= igher pressure).=A0 If there is a leak somewhere, then there is just more o= il flowing through the leak instead of=A0into the engine.=A0 That is especi= ally true with the spring loaded regulators..=A0 higher pressure means=A0th= at the spring opens preferentially.=A0
=A0
--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
=A0
On Tue, Oct 26, 2010 at 10:48 AM, Dave <david.staten@gmail.c= om> wrote:
If the pressure does not exceed t= he minimum of the pop-off valves on the front or back irons, then how is th= e volume of oil reduced?=20



On 10/26/2010 12:44 PM, David Leonard wrote:= =20
Chris,
=A0
Regarding the oil pressure, I just wanted to remind you of one thing.= =A0 The reason that the oil pressure goes up with thicker oil, is because l= ess of it is flowing through the engine and more is going out the regulator= .=A0
=A0
I submit that it works like this: the oil gets thicker, it does not fl= ow as easily anywhere although the pump still puts out the same amount of o= il, that causes the pressure to go up, which opens the regulator a little m= ore than it was when the pressure was lower, this causes a=A0HIGHER PERCENT= AGE of the total flow to go through the regulator instead of into the e-sha= ft.=A0 Since the total flow remains the same as when the pressure was lower= (for a given RPM, the result is a net reduction in flow to the e-shaft.=A0= while it is probably true that the thicker oil will lube the bearing bette= r, so not as much=A0might be=A0needed, don't forget that most of the oi= l going into the e-shaft is going to cool the rotors.=A0 And a reduced amou= nt of thicker oil is not going to cool nearly as well as a higher amount of= thinner oil.
=A0
There is obviously a balance/optimum oil thickness, and the manufactur= er probably=A0knows best by suggesting a particular thickness of=A0oil.=A0 = As we say in medicine, don't go chasing after lab numbers (which is wha= t oil pressure really is). =A0If you felt your oil pressure was too low you= want to find the underlying cause rather than make it look better by thick= ening up the oil.=A0 If I had a patient who was severely anemic I could mak= e the blood count look better by giving transfusions, but I might be missin= g the life threatening GI bleed.
=A0
Oil pressure too low?=A0 think of all those things on the list that Ly= nn sent out.=A0 Think that your application warrants a higher oil pressure?= =A0 Then install stronger springs in the regulator and keep that oil flowin= g through the engine rather than rob the engine so you have a nice pretty n= umber on a gauge.
=A0
And it appears that keeping with the=A0regular weight=A0oil will save = some $$$ as well.
=A0
--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRo= ster.net


On Tue, Oct 26, 2010 at 6:50 AM, Chris Barber <cbarber@texasattorney.net> wrote:
Since my oil pressure was down a bit following my pressure repair I de= cided to take heed or=A0some of the comments regarding one of=A0the possibl= e causes as presented here.=A0 It seemed to be the easiest that I could try= .
=A0
So, I shelled out the bucks for some Royal Purple 50 (actually, 20/50 = IIRC).=A0 Geezh, I thought the 30=A0weight and 40=A0weight was pricey at $8= and $10 a quart, this stuff was $16.00 a quart.=A0 I drained about 2 to 3 = quarts out of the pan and out of the filter and replaced it with the 50 wie= ght.=A0 So, now it was a blend of the 30 and the 50.=A0 I cranked up the en= gine and my oil pressure was up by about 10-15 psi.=A0 WOW!=A0 I did not ex= pect such a dramatic increase.=A0 I had just run the engine=A0earlier (befo= re I went and=A0purched the oil).=A0=A0Before the change, my idle=A0pressur= e was around 28-30.=A0 After the change it was in the low 40's.=A0 The = most psi I was getting=A0 before the change was about 50-55 psi at 6300 rpm= .=A0 After the change it was at about 72 psi at 6300.=A0
=A0
I let her idle for about ten minutes and all seemed good. So, since my= temps seemed good and steady now that Outside air Temps were have now dipp= ed down into the low 90 I decided to taxi around a bit.=A0 Yep, I sometimes= enjoy taxiing around in my very expensive go-cart.=A0
=A0
The engine was running=A0sooooo smooth and strong.=A0 I was feeling pr= etty damn good about it all.=A0 Since I was moving around on the ramp where= there was quite a bit of=A0traffic following this weekends big 'ol Win= gs Over Houston air show, I reached down and switched on my nav/strobe ligh= ts.=A0 At the exact instant of turning on the light (which, btw, are on my = secondary alternator circuit) the engine started faltering and wanting to s= tall out.=A0 WTF!!!=A0 I switched to the B computer and things smoothed out= .=A0 Back to A and had to add throttle and mixture to keep it running and i= t was still rough.=A0 Back to B to make it=A0 back to the hangar.
=A0
Once back at the hangar, I checked the MAP table (RWS EM2, btw) and no= thing seemed changed from earlier.=A0=A0Kinda sounded like fuel was having = trouble getting to the injectors.=A0 I would think to look at the injectors= first, but am not inclined to focus here too much since the=A0engien smoot= hed out when changed to the B computer.=A0 Since both computers use the sam= e systems, it seems to be isolated to the primary computer.=A0 Please, corr= ect what I am missing here.=A0 Since my=A0judgment was clouded with anger, = I put everything back in=A0th hangar for the night.=A0 This good=A0good bad= good bad stuff is taxing and discouraging.=A0 I feel I am so close, then t= his nonsense.=A0 (on top of my=A0RPM's cutting out around 6000 rpm - ca= n slowly inch it up to 6300, with power to spare- if I go slowly, but cuts = out at rpm over 6300 and change on the=A0EM2 and an=A0EGT reading issue). T= o quote Mork....."Heavy sigh".
=A0
Trying to wrap my head around where to start on this latest PITA greml= in.=A0 It had been running as close to perfect as I could have imagined.
=A0
All the best,
=A0
Chris Barber
Houston







--20cf30549e555aecad0493890ad1--