X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-qy0-f196.google.com ([209.85.221.196] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3884661 for flyrotary@lancaironline.net; Tue, 13 Oct 2009 13:50:52 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.221.196; envelope-from=rwstracy@gmail.com Received: by qyk34 with SMTP id 34so8353421qyk.14 for ; Tue, 13 Oct 2009 10:50:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to :content-type; bh=kkcWd29+Goae5+VYZauntSQlLHDFo66RjsW776E7NKk=; b=wmSEL61OB3WKpBzjHG5DY3RV02DoZWaxdDcfugD66qvPNEiAHcSnkFRy19cRZYP0G6 2l6kQlnmq5mMDLXUq1rybg0rXZ1J3Iq3d7oAikuJchaw0PwIs5Vj9QZbjO+Da6tOWBix kFRl1QRWkxlvEBaz9wJNqdZf4EiXYiZP7JNmE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type; b=jvaDMZJcKKEOQAMZOATj/hudP7jrqZXqxScrm0B8vCATIm5v6Pygxao4kSLIn8lJD4 9gpG9BMnh0984N7wj70v9FtJkI9OYbfSxMD28N2br3darY4h6oDP9a7YBb9bWCSt/1Ib uR04Wv0BIsQp8qWCyTlj7H8y8w1mFAgvk5tQE= MIME-Version: 1.0 Sender: rwstracy@gmail.com Received: by 10.224.48.19 with SMTP id p19mr6193508qaf.165.1255456216867; Tue, 13 Oct 2009 10:50:16 -0700 (PDT) In-Reply-To: References: Date: Tue, 13 Oct 2009 11:50:16 -0600 X-Google-Sender-Auth: 1d1f958d2d640915 Message-ID: <1b4b137c0910131050l1207e4e2l795b6ea84bac60fb@mail.gmail.com> Subject: Re: [FlyRotary] where's the missing power? From: Tracy Crook To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=001485044788d666ba0475d4ad2a --001485044788d666ba0475d4ad2a Content-Type: text/plain; charset=ISO-8859-1 Mike, There are several possible explainations for the throttle position (not being WOT at max power) but there are only a few possible reasons for the best power being reached at 4" Hg manifold pressure below what is available (if that is true). I hesitate to point it out because you most likely already eliminated the obvious but the most likely cause is the mixture going lean because of MAP table setting or fuel pressure differential at the injector being too low. Have you fiddled with the mixture control at WOT? What does your mixture monitor indicate at WOT? Tracy (still in CO) On Sat, Oct 10, 2009 at 9:27 PM, Mike Wills wrote: > I noticed quite a while ago and have mentioned several times here that my > engine does not have a linear response to throttle. It reaches its max power > before it reaches fully open throttle. I havent worried too much about this > up until now because the airplane has sufficient power as is, has slightly > better performance than my previous 160HP Lyc powered -6A, and my wood prop > is actually a pretty good match for the current power level. > > But I would like to understand what's going on here and eventually address > it. I was flying yesterday, my usual boring holes in the sky directly over > the airport. Decided to investigate just a little so leveled at 5,000 feet > at full throttle. Started reducing throttle until I noticed a slight > reduction in RPM and fuel flow. Then looked down at where the throttle was > actually set and was shocked to see it slightly below half open. I dont have > a regular manifold pressure gauge, just an industrial type vacuum gauge ( I > really gotta get an MP gauge). Anyway, the vacuum gauge was indicating 4" of > vacuum. > > So I suspect I am giving up a substantial amount of HP. I think the most > likely suspect is my throttle body. For a throttle body I copied Tracy's > original design. Started with a stock late 80s Mazda TB and hacked off the > third port and all of the extra stuff. The cowl in this area is very tight > and I am unable to install any sort of air filter or any sort of bell mouth > on the TB. And I'm sure the cowl's close proximity to the TB influences > airflow into it as well. > > Any comments on this or ways to test it are welcome. > > Mike Wills > RV-4 N144MW > --001485044788d666ba0475d4ad2a Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Mike, There are several possible explainations for the throttle positi= on (not being WOT at max power)=A0 but there=A0are only a few=A0possible re= asons for the best power being reached at 4" Hg manifold pressure belo= w what is available (if that is true).
=A0
=A0=A0 I hesitate to point it out because you most likely already elim= inated the obvious but=A0the most likely cause is the mixture going lean be= cause of MAP table setting or fuel pressure differential at the injector=A0= being too low.=A0 =A0Have you fiddled with the mixture control=A0at WOT?=A0= What does your mixture monitor indicate at WOT?
=A0
Tracy (still in CO)

On Sat, Oct 10, 2009 at 9:27 PM, Mike Wills <rv-4mike@cox.net&= gt; wrote:
I noticed quite a while ago and have m= entioned several times here that my engine does not have a linear response = to throttle. It reaches its max power before it reaches fully open throttle= . I havent worried too much about this up until now because the airplane ha= s sufficient power as is, has slightly better performance than my previous = 160HP Lyc powered -6A, and my wood prop is actually a pretty good match for= the current power level.
=A0
But I would like to understand what= 9;s going on here and eventually address it. I was flying yesterday, my usu= al boring holes in the sky directly over the airport. Decided to investigat= e just a little so leveled at 5,000 feet at full throttle. Started reducing= throttle until I noticed a slight reduction in RPM and fuel flow. Then loo= ked down at where the throttle was actually set and was shocked to see it s= lightly below half open. I dont have a regular manifold pressure gauge, jus= t an industrial type vacuum gauge ( I really gotta get an MP gauge). Anyway= , the vacuum gauge was indicating 4" of vacuum.
=A0
So I suspect I am giving up a substant= ial amount of HP. I think the most likely suspect is my throttle body. For = a throttle body=A0I copied Tracy's original design. Started with a stoc= k late 80s Mazda TB and hacked off the third port and all of the extra stuf= f. The cowl in this area is very tight and I am unable to install any sort = of air filter or any sort of bell mouth on the TB. And I'm sure the cow= l's close proximity to the TB influences airflow into it as well.
=A0
Any comments on this or ways to test i= t are welcome.
=A0
Mike Wills
RV-4 N144MW
<= /blockquote>

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