X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost03.isp.att.net ([207.115.11.53] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTP id 6471450 for flyrotary@lancaironline.net; Wed, 11 Sep 2013 16:40:35 -0400 Received-SPF: none receiver=logan.com; client-ip=207.115.11.53; envelope-from=bbradburry@bellsouth.net Received: from desktop (adsl-98-85-111-127.mco.bellsouth.net[98.85.111.127]) by isp.att.net (frfwmhc03) with SMTP id <20130911203959H0300pom5ne>; Wed, 11 Sep 2013 20:39:59 +0000 X-Originating-IP: [98.85.111.127] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: In-Reply-To: Subject: RE: [FlyRotary] Re: First Flight jitters Date: Wed, 11 Sep 2013 16:39:59 -0400 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01CEAF0D.8ED59240" X-Mailer: Microsoft Office Outlook 11 Thread-Index: Ac6vIBEJMKLQ6XayR/6Yiv8OhVb4ZwADghiA X-MimeOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 This is a multi-part message in MIME format. ------=_NextPart_000_0009_01CEAF0D.8ED59240 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit At sea level on a standard day. At 18000 ft on a standard day, that would be 14.96 + 29.04 hg of boost, which converts to about 13.2 psi. The pressure ratio at sea level is only about 1.47 but at 18000 ft it is 2.93. it seems difficult to find a turbo that is sized to adequately serve at both low and high altitudes. How are those of you with turbos sizing for this problem? Bill _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ben Haas Sent: Wednesday, September 11, 2013 2:52 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: First Flight jitters 44hg is based on 29.92 + 11 hg of boost..... That converts to about 5 psi Ben Haas www.haaspowerair.com _____ To: flyrotary@lancaironline.net From: Lehanover@aol.com Date: Wed, 11 Sep 2013 01:46:54 -0400 Subject: [FlyRotary] Re: First Flight jitters I must admit I have never understood manifold pressure. I have been working on that. The lack of power at lower RPM is understood. RPM X torque = HP. So, the engine has poor torque due to short stroke. There goes half of your multiplier. Tuning needs to be a bit closer to ideal. The best way to remove HP is a poor exhaust system. Look at the care in the designs of dirt bike exhaust systems. A typical turbo exhaust manifold is a poor design for a normally aspirated engine. And until the boost is up to overcome that poor design and add the recovered power to the intake, you just have a NA engine with a bad exhaust design. So the first engine saw 44" HG when it failed. That would be 21.5 pounds of boost. Over 20 pounds you need to be right on the tune. Well rich of peak EGT to fuel cool and lower charge temperature. Timing 2 degrees below best power. Good size intercooler and a quick waste gate. That was on the way to being a drag racing engine before adding the known problems. When the boost is low or there is none, then you can use more ignition advance. Once you can limit boost to say 4 to 6 pounds or 8" to 16"HG with a waste gate you can be close to 18 degrees. Same as a NA engine. When the boost is up to maximum then you need to retard a bit. On long closed throttle runs you can be up to 35 degrees. This because you have few pounds of air, and nearly no fuel flow. So, very low compression. All this takes a long time to burn the idle mix. The RX-8s do this. How is this? One pound of boost is the same as 2.04" HG. Or, 14.7 pounds at sea level times 2.04 =29.98" HG. At any throttle setting, local barometer showing on the manifold pressure gage suggests a well designed intake system and a free flowing air filter. The Manifold pressure gage is measuring vacuum in the intake system. The gage is connected between the butterfly and the engine or turbo inlet. The boost gage measures pressures above local barometric in either pounds of boost or inches of Mercury or both and is connected between the turbo and the engine. It is measuring pressure in the inlet runner. Is that correct? Add timing marks to your starter ring gear. Divide the number of teeth by 360 to get degrees per tooth. Clean and paint a green tooth at TDC. Turn the engine backwards and paint a tooth or valley between teeth another color for 15 degrees. Paint a red tooth at 20 degrees, and so-on. Write the code on the engine beside the pointer you have constructed. OK for tractor aircraft. Not so much fun for pushers where the prop is pulling at your loose clothing. Lynn E. Hanover In a message dated 9/9/2013 9:36:25 P.M. Eastern Daylight Time, rwstracy@gmail.com writes: If your ignition timing measurement was accurate at 3000 rpm and 16" mp, it's way too retarded. What did you set the static timing to? Remember that that has nothing to do with actual ignition timing. It's just a reference point for the computer. Tracy ------=_NextPart_000_0009_01CEAF0D.8ED59240 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

At sea level on a standard = day.  At 18000 ft on a standard day, that would be 14.96  + 29.04 hg of boost, = which converts to about 13.2 psi.

 

The pressure ratio at sea level is = only about 1.47 but at 18000 ft it is 2.93.  it seems difficult to find = a turbo that is sized to adequately serve at both low and high altitudes.  = How are those of you with turbos sizing for this = problem?

 

Bill

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ben Haas
Sent: Wednesday, = September 11, 2013 2:52 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = First Flight jitters

 

44hg  is based on = 29.92 + 11 hg of boost..... That converts to about 5 psi

Ben Haas
www.haaspowerair.com

To: flyrotary@lancaironline.net
From: Lehanover@aol.com
Date: Wed, 11 Sep 2013 01:46:54 -0400
Subject: [FlyRotary] Re: First Flight jitters


I must admit I have never = understood manifold pressure. I have been working on that. The lack of power at = lower RPM is understood.

 

=

RPM X torque =3D HP. So, the = engine has poor torque due to short stroke. There goes half of your = multiplier. Tuning needs to be a bit closer to ideal. The best way to remove HP is a = poor exhaust system.

Look at the care in the designs of = dirt bike exhaust systems. A typical turbo exhaust manifold is a poor design = for a normally aspirated engine.

And until the boost is up to = overcome that poor design and add the recovered power to the intake, you just = have a NA engine with a bad exhaust design. 

 

=

So the first engine saw 44" = HG when it failed. That would be 21.5 pounds of boost. Over 20 pounds you need = to be right on the tune.

Well rich of peak EGT to fuel cool = and lower charge temperature.

Timing 2 degrees below best power. = Good size intercooler and a quick waste gate. That was on the way to being a = drag racing engine before adding the known problems. =

 

=

When the boost is low or there is = none, then you can use more ignition advance.  Once you can limit boost = to say 4 to 6 pounds or 8" to 16"HG with a waste gate you can be close = to 18 degrees. Same as a NA engine. When the boost is up to maximum = then you need to retard a bit. On long closed throttle runs you can be up to 35 = degrees.

This because you have few pounds = of air, and nearly no fuel flow. So, very low compression. All this takes a long = time to burn the idle mix.

The RX-8s do this. =

 

=

How is this? One pound of boost is = the same as 2.04" HG. Or, 14.7 pounds at sea level times 2.04 = =3D29.98" HG. At any throttle setting,

local barometer showing on the = manifold pressure gage suggests a well designed intake system and a free flowing = air filter. The Manifold pressure gage is measuring vacuum in the intake system. The gage is connected between the butterfly and the = engine or turbo inlet.

 

=

The boost gage measures pressures = above local barometric in either pounds of boost or inches of Mercury or = both and is connected between the turbo and the engine. It is measuring = pressure in the inlet runner. 

 

=

Is that correct? =

 

=

Add timing marks to your starter = ring gear. Divide the number of teeth by 360 to get degrees per tooth. Clean = and paint a green tooth at TDC.

Turn the engine backwards and = paint a tooth or valley between teeth another color for 15 degrees. Paint a red = tooth at 20 degrees, and so-on. Write the code on the engine beside the = pointer you have constructed. OK for tractor aircraft. Not so much fun for pushers = where the prop is pulling at your loose clothing. =

 

=

Lynn E. = Hanover

 

=

 

=

In a message dated 9/9/2013 = 9:36:25 P.M. Eastern Daylight Time, rwstracy@gmail.com = writes:

If your ignition timing = measurement was accurate at 3000 rpm and 16" mp,  it's way too retarded. =  What did you set the static timing to?   Remember that that has nothing = to do with actual ignition timing.  It's just a reference point for the computer.

 

=

Tracy

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