X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-wi0-f180.google.com ([209.85.212.180] verified) by logan.com (CommuniGate Pro SMTP 5.4.3) with ESMTPS id 5353156 for flyrotary@lancaironline.net; Tue, 17 Jan 2012 06:47:38 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.212.180; envelope-from=msteitle@gmail.com Received: by wibhn6 with SMTP id hn6so2335518wib.25 for ; Tue, 17 Jan 2012 03:47:01 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=vMLICnl2J89elORyCcwOdWeIS9GaA49wm36xEnpuS8Y=; b=A5GieqfAuKcsN7PnRW15ctO1cSYH5CtByS8jp7wc0EGvr+eBP5QwxB+bdshvOA3gx5 iTPSlYS+YZbsRcW6hOvP7uTzD8RFkzQBs5s2p5QGfwV3RY20AEjGbr7CTyCEttnpYMEH 8RwicDEwYDXTzwnjz2J3f9M4Jci5wnlaRwX4k= MIME-Version: 1.0 Received: by 10.180.19.168 with SMTP id g8mr27609269wie.4.1326800821140; Tue, 17 Jan 2012 03:47:01 -0800 (PST) Received: by 10.223.105.211 with HTTP; Tue, 17 Jan 2012 03:47:01 -0800 (PST) In-Reply-To: References: Date: Tue, 17 Jan 2012 05:47:01 -0600 Message-ID: Subject: Re: [FlyRotary] Re: tuning advice From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=bcaec53d5503a1bddf04b6b7e3b2 --bcaec53d5503a1bddf04b6b7e3b2 Content-Type: text/plain; charset=ISO-8859-1 Lynn, Thanks so much for a very detailed reply. It sounds like the factory EC-2 setting for advance will be pretty close for cruise (5200 rpm) mode for my p-port engine. I usually lean pretty aggressively, so maybe a couple of degrees would be in order. Can you tell me if its normal for the MAP to be different for p-port engines, particularly around idle (1800 rpm)? My MAP readings are approx. 17.0 - 17.3 at idle. This is about 2" higher that with my side-port engine. I'm thinking this is because of the much higher intake/exhaust overlap with the p-port engine. Thanks, Mark On Mon, Jan 16, 2012 at 7:51 PM, wrote: > ** > The Pport is at a disadvantage at idle in that the inlet tract is so large > that air velocity in any situation is low. Great for high power (Low flow > drag). So fuel injected for idle more than a few MM from the port into the > block will surely return to droplets resulting in erratic idle and surging. > There is far less of a problem at close to 2,000 RPM. > > The side port block is usually run only on the inner or primary runners > that are deliberately > quite small and have higher velocity in any situation. In the car the > primary ports have a separate butterfly, so the only air available to the > engine is through the primary runners. > This gives a very satisfactory idle even when cold. With injection or a > carb the engine runs only on the primaries until higher power is demanded. > > The exact idle mixture will vary according to conditions. No thought > is given to producing best cylinder pressure at 50 degrees after TDC as you > will at some higher power setting. > > So on a cold morning you may need 11.7:1 to keep it running, and on a warm > morning perhaps 12.7:1 will be enough. But no two mornings will be exactly > the same, so the mixture knob must be adjusted in probably every case. The > more sophisticated the brain box the less adjusting will be required. In > effect, the brain box just fiddles with the mixture knob for you. > > On timing. > > For best power above 8,000 RPM with car gas 25 to 26 degrees. For avgas 27 > to 28 degrees. > > For best power at 5,000 to 5,500 RPM, 22 degrees for car gas and 24 for > avgas. > > The function of advance is to provide enough time to produce highest > cylinder pressure > at 50 degrees after TDC. Or better yet, since I have never even seen a > dyno pass below 7,000 RPM, because we need best power at 9,400 RPM (My > engines had 244 HP at 9,400), So I am guessing on this. > > If the EGT does not exceed 1650 in any case then no damage is usually > possible. > So if you keep that in mind and fiddle with the mixture at cruise to get > best airspeed, the go back a bit richer on the figure, all will be fine. So > you are rich of best power by a readable margin. Or you can go over 100 > degrees lean of peak EGT for economy cruise and add advance as the > over-lean mixture burns slower. EGT will be much lower and the timing can > be adjusted to get highest air speed without fear of damage. > > The airplane is just an expensive dyno. So much research can be done. > > The wide range of data is a result of the many intake and exhaust designs > being produced be so many folks building installations. If you have > a dismal intake system that limits cylinder filling then you can get away > with lots of advance. If you have a great system that really shines at > 5,500 RPM then you cannot run as much advance. So when another builder says > this or that as a fact, don't crank that data into your engine without > lots of thinking first. > Your engine acts only like your engine and not the same as any other > engine. > > A Pport would more likely have much better cylinder filling than a side > port. So, its effective compression ratio would be higher at any RPM than a > side port engine. So, higher compression means higher flame speed requiring > less advance to get best pressure at 50 degrees ATC. At idle it does not > matter. > > Any question, anytime. > > Lynn E. Hanover > > In a message dated 1/16/2012 6:53:37 P.M. Eastern Standard Time, > msteitle@gmail.com writes: > > Lynn, > > I know this is an old posting, but I save all of your posts for future > reference. I was wondering if you could you comment on the amount of > advance appropriate for a p-port engine? What is the max advance I should > run with 100LL? Do the numbers you quoted below apply the same to p-ports > as to side port engines? > > As it relates to a p-port engine, what MAP readings should I get at idle > (1800-2000 rpm)? > > Thanks, > Mark > > --bcaec53d5503a1bddf04b6b7e3b2 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Lynn,=A0

Thanks so much for a very detailed reply. =A0It= sounds like the factory EC-2 setting for advance will be pretty close for = cruise (5200 rpm) mode for my p-port engine. =A0I usually lean pretty aggre= ssively, so maybe a couple of degrees would be in order. =A0

Can you tell me if its normal for the MAP to be differe= nt for p-port engines, particularly around idle (1800 rpm)? =A0My MAP readi= ngs are approx. 17.0 - 17.3 at idle. =A0This is about 2" higher that w= ith my side-port engine. =A0I'm thinking this is because of the much hi= gher intake/exhaust overlap with the p-port engine. =A0

Thanks,
Mark

On Mon, Jan 16, 2012 at 7:51 PM, <Lehanover@aol.com> wrote:
The Pport is at a disadvantage at idle in that the inlet tract is so l= arge=20 that air velocity in any situation is low. Great for high power (Low flow d= rag).=20 So fuel injected for idle more than a few MM from the port into the block w= ill=20 surely return to droplets resulting in erratic idle and surging. There is f= ar=20 less of a problem at close to 2,000 RPM.
=A0
The side port block is usually run only on the inner or primary runner= s=20 that are deliberately =A0
quite small and have higher velocity in any situation. In the car the= =20 primary ports have a separate butterfly, so the only air available to the e= ngine=20 is through the primary runners.
This gives a very satisfactory idle even when cold. With injection or = a=20 carb the engine runs only on the primaries until higher power is demanded.= =20
=A0
The exact idle mixture will vary according to conditions. No thought= =20 is=A0given to producing best cylinder pressure at 50 degrees after TDC as y= ou=20 will at some higher power setting.
=A0
So on a cold morning you may need 11.7:1 to keep it running, and on a = warm=20 morning perhaps=A012.7:1 will be enough. But no two mornings will be exactl= y=20 the same, so the mixture knob must be adjusted in probably every case. The = more=20 sophisticated the brain box the less adjusting will be required. In effect,= the=20 brain box just fiddles with the mixture knob for you.
=A0
On timing.
=A0
For best power above 8,000 RPM with car gas 25 to 26 degrees. For avga= s 27=20 to 28 degrees.
=A0
For best power at 5,000 to 5,500 RPM, 22 degrees for car gas and 24 fo= r=20 avgas.
=A0
The function of advance is to provide enough time to produce=A0 highes= t=20 cylinder pressure
at 50 degrees after TDC. Or better yet, since I have never even seen a= dyno=20 pass below 7,000 RPM, because we need best power at 9,400 RPM (My engines h= ad=20 244 HP at 9,400), So I am guessing on this.
=A0
If the EGT does not exceed 1650 in any case then no damage is usually= =20 possible.
So if you keep that in mind=A0 and fiddle with the mixture at cruise t= o=20 get best airspeed, the go back a bit richer on the figure, all will be fine= . So=20 you are rich of best power by a readable margin. =A0Or you can go over 100= =20 degrees lean of peak EGT for economy cruise and add advance as the over-lea= n=20 mixture burns slower. EGT will be much lower and the timing can be adjusted= to=20 get highest air speed without fear of damage.=A0=A0
=A0
The airplane is just an expensive dyno. So much research can be done.<= /div>
=A0
The wide range of data is a result of the many intake and exhaust desi= gns=20 being produced be so many folks=A0building installations. If you have=20 a=A0dismal intake system that limits cylinder filling then you can get away= =20 with lots of advance. If you have a great system that really shines at 5,50= 0 RPM=20 then you cannot run as much advance. So when another builder says
this or that as a fact, don't crank that data into your engine wit= hout lots=20 of thinking first.
Your engine acts only like your engine and not the same as any other= =20 engine.
=A0
A Pport would more likely have much better cylinder filling than a sid= e=20 port. So, its effective compression ratio would be higher at any RPM than a= side=20 port engine. So, higher compression means higher flame speed requiring less= =20 advance to get best pressure at 50 degrees ATC.=A0 At idle it does not=20 matter.
=A0
Any question, anytime.
=A0
Lynn E. Hanover=A0
=A0

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