X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-pz0-f183.google.com ([209.85.222.183] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3882219 for flyrotary@lancaironline.net; Sun, 11 Oct 2009 02:49:19 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.222.183; envelope-from=wdleonard@gmail.com Received: by pzk13 with SMTP id 13so7924207pzk.25 for ; Sat, 10 Oct 2009 23:48:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=N157PzpxMBZHuc35eh2t9C+bU2T+fvPralunsEAr1H4=; b=KR1OApjbneYAdcAb9OijoZBA/zNVnuXgryJ/8npdtpzaELyhHiozW8/k4uVTTrNmod WkYfk3k/8tBG+pVkKwRwJBF9DvflW//WhzCFm0Zc3q7abkTUl2GpypXXwLpCF7iT2FGS B2h79f10wCVu5FF92kbDNDisSkGO4o/aSBQGs= 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=uuZhz1SuyAI5eFTbrkbXY43H5gKevr067k5lcnkfkrZNzjBrt1qjue87YZahfRtCIh Mr+jFrDVBXqjjEmurDXPt4rlKBbdoqA9ksIkQpO/sYx9+Gru1FhV2z1L2Jxui7E9CCGC IfoSJ9kQ3o7NRz4szrH383CBgXcePktMONo1Q= MIME-Version: 1.0 Received: by 10.142.247.42 with SMTP id u42mr346019wfh.259.1255243718960; Sat, 10 Oct 2009 23:48:38 -0700 (PDT) In-Reply-To: References: Date: Sat, 10 Oct 2009 23:48:38 -0700 Message-ID: <1c23473f0910102348v34baaa80t198ca5d812fedc0@mail.gmail.com> Subject: Re: [FlyRotary] Re: where's the missing power? From: David Leonard To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=00504502cc35f9a60b0475a33388 --00504502cc35f9a60b0475a33388 Content-Type: text/plain; charset=ISO-8859-1 Mike, The last couple of inches of my throttle don't give me much power difference either, for what it is worth. I can't believe thay you have not been up in my plane yet. I have this coming week off if you have any time... Dave On Sat, Oct 10, 2009 at 11:14 PM, wrote: > Mike, > There are several reasons that an engine will produce max power at "less" > than full throttle. First, and this can sometimes be hard to check, be sure > that your full throttle position doesn't rotate the throttle plate past full > open. I've seen this several times in butterfly throttle systems. If you are > using a Mazda throttle body it is likely that the wide open position is > controlled with a stop. You shouldn't have a over rotation problem with > that. The second reason, and far more common, is that the design has more > intake than it can use with the tuning or RPM that the prop limits it to. > This isn't really a problem other than indicating that with development the > engine could make more power. Often with the design constraints placed on us > by a close fitting cowling or restrictive exhaust limit the best airflow to > less than the throttle body can pass. The engine just can't "breathe" well > enough to need a larger opening. The length of the intake or exhaust can be > too long/short and the maximum amount of air that the engine can digest will > be at the 3/4 throttle area or even less. Most engines can be tuned to best > performance at a specific length inlet and the diameter is also important. > Same with the exhaust. If either system is off a significant amount it can > prevent you from making any more power past a given throttle opening. This > won't hurt the engine at all, it just shows you that some portion of the > system can be improved. If your exhaust gas temperature is correct then the > injection is working properly and you need to check the other systems. Be > sure to double check your exhaust for obstructions or a pipe collapse. We > have had too many exhaust problems lately. To put your self at ease remember > this, most modern diesels have NO throttle plate. The speed of the engine is > completely controlled by the amount of fuel injected. This helps the > efficiency at maximum throttle, but obviously there is more air than the > engine can use at low speeds. A small amount of fuel is injected, > compression ignited ,and all burns up. If all is healthy your engine is > drawing all the air you can use by half throttle. You can probably make > improvements and get more power or lower fuel burn by tuning. > Bill Jepson > > -----Original Message----- > From: Mike Wills > To: Rotary motors in aircraft > Sent: Sat, Oct 10, 2009 8:27 pm > Subject: [FlyRotary] where's the missing power? > > 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 > -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net --00504502cc35f9a60b0475a33388 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Mike,
=A0
The last couple of inches of my throttle don't give me much power = difference either, for what it is worth.=A0 I can't believe thay you ha= ve not been up in my plane yet.=A0 I have this coming week off if you have = any time...
=A0
Dave

On Sat, Oct 10, 2009 at 11:14 PM, <wrjjrs@aol.com> wro= te:
Mike,
There are several reasons that an engine will produce max power at &qu= ot;less" than full throttle. First, and this can sometimes be hard to = check, be sure that your full throttle position doesn't rotate the thro= ttle plate past full open. I've seen this several times in butterfly th= rottle systems. If you are using a Mazda throttle body it is likely that th= e wide open position is controlled with a stop. You shouldn't have a ov= er rotation problem with that. The second reason, and far more common, is t= hat the design has more intake than it can use with the tuning or RPM that = the prop limits it to. This isn't really a problem other than indicatin= g that with development the engine could make more power. Often with the de= sign constraints placed on us by a close fitting cowling or restrictive exh= aust=A0limit the best airflow to less than the throttle body can pass. The = engine just can't "breathe" well enough to need a larger open= ing.=A0The length of the intake or exhaust can be too long/short and the ma= ximum amount of air that the engine can digest will be at the 3/4 throttle = area or even less. Most engines can be tuned to best performance at a speci= fic length inlet and the diameter is also important. Same with the exhaust.= If either system is off a significant amount it can prevent you from makin= g any more power past a given throttle opening. This won't hurt the eng= ine at all, it just shows you that some portion of the system can be improv= ed. If your exhaust gas temperature is correct then the injection is workin= g properly and you need to check the other systems. Be sure to double check= your exhaust for obstructions or a pipe collapse. We have had too many exh= aust problems lately. To put your self at ease remember this, most modern d= iesels have NO throttle plate. The speed of the engine is completely contro= lled by the amount of fuel injected. This helps the efficiency at maximum t= hrottle, but obviously there is more air than the engine can use at low spe= eds. A small amount of fuel is injected, compression ignited ,and all burns= up. If all is healthy your engine is drawing all the air you can use by ha= lf throttle. You can probably make improvements and get more power or lower= fuel burn by tuning.
Bill Jepson=20


-----Original Message-----
From: Mike Wills &l= t;rv-4mike@cox.net>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sat, Oct 10, 2009 8:27 pm
Subject: [FlyRotary] where's the mis= sing power?

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



--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net
--00504502cc35f9a60b0475a33388--