X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 22 Jun 2012 12:28:23 -0400 Message-ID: X-Original-Return-Path: Received: from elasmtp-dupuy.atl.sa.earthlink.net ([209.86.89.62] verified) by logan.com (CommuniGate Pro SMTP 5.4.6) with ESMTP id 5620276 for lml@lancaironline.net; Fri, 22 Jun 2012 01:04:11 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.62; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=KgrPIIckEUZkEW58LeIIdr9tBb/37X72NxdC6csGWkYJFwq0ht9XPS/gvaAoNraZ; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [70.105.247.254] (helo=[192.168.1.24]) by elasmtp-dupuy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1Shw1v-00054m-Ny for lml@lancaironline.net; Fri, 22 Jun 2012 01:03:35 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: multipart/alternative; boundary=Apple-Mail-266--890521154 Subject: Re: [LML] Re: Precision airmotive servo X-Original-Date: Fri, 22 Jun 2012 01:03:35 -0400 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1084) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da9401a0a74962a724309110562fe2f11115c350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 70.105.247.254 --Apple-Mail-266--890521154 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Isn't there someone that does this for a price? e.g. Gami has a machine = that tests flow for injectors. Does someone have a machine that tests = flow for the main metering jet? On Jun 21, 2012, at 1:07 PM, Gary Casey wrote: Full throttle fuel flow is determined by only two things - the diameter = of the main metering jet and the pressure drop across it. It is = impractical to mess with the pressure drop, so the only way to change = the mixture is by changing (enlarging) the metering orifice. Removing = the brass orifice is not very difficult - just remove the cap on the = opposite end of the mixture control. It just slides out, but make sure = it gets put back in with the same orientation. The orifice is off = center and the mating port gets rotated by the mixture control, closing = off the orifice. Pretty simple, really. But first you have to know how much you would want it enlarged. The = mixture at takeoff should be noticeably richer than best power - if you = lean at full throttle on the ground you should see a slight rpm = increase. And yes, the EGT should be at least 150 ROP. But what is = peak EGT on the ground? Do you want to run it in that condition long = enough to find out? You might want to richen in increments of 5 percent = or less, and therein is the rub. To richen the mixture 5 percent the = diameter must be increased by only 2.5 percent. If you are really lucky = you might have a drill just that size - I did - but most likely you will = have to take it to a shop that has reamers that can open it up. The = other thing to try if you like is to put a radius at the leading edge of = the orifice, which has a chamfer already. A very slight "break" of the = sharp edge will increase the fuel flow a couple of percent. Naturally, = you have to keep everything perfectly clean. The good thing is that you = can test it without flying. After an attempt or two you will either = have what you want or will be ready to send it off to an "expert" for = the adjustment. You've "scrapped" the metering orifice, but they're not = very expensive. The point is that for minor increases in fuel flow you can make slight = changes without much trouble. If you overshoot you are back to plan B. = The good news is that once you have it right it never has to be adjusted = again, unlike on the Continental system. Gary Casey I believe my fuel servo is not delivering sufficient fuel to the engine = in the takeoff position. Why I say this is because the difference = between the peak EGT and the takeoff EGT is 70 degrees F on the leanest = cylinder and 120 on the richest. The book says this spread should be = anywhere between 150 and 200 degrees F. Why do I care you may ask.. = Well my CHTs are too high at full throttle takeoff. I have to work to = keep them below 430. I have done everything possible to maximize = cooling airflow with little improvement in the CHT situation. =20 Anyhow, I would be interested in information from the group on the = following=20 Like to compare fuel flows at full throttle at close to sea level (mine = is between 15 and 16 gals/hr) Any info concerning experience with enriching the takeoff flow on the = bendix style RSA-5AD1 servo (this setting is internal, I have found no = reference material on the procedure) Thanks Tom --Apple-Mail-266--890521154 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii Isn't = there someone that does this for a price?  e.g. Gami has a machine = that tests flow for injectors.  Does someone have a machine that = tests flow for the main metering jet?

On Jun 21, 2012, = at 1:07 PM, Gary Casey wrote:

Full throttle fuel flow is determined by only = two things - the diameter of the main metering jet and the pressure drop = across it.  It is impractical to mess with the pressure drop, so = the only way to change the mixture is by changing (enlarging) the = metering orifice.  Removing the brass orifice is not very difficult = - just remove the cap on the opposite end of the mixture control. =  It just slides out, but make sure it gets put back in with the = same orientation.  The orifice is off center and the mating port = gets rotated by the mixture control, closing off the orifice. =  Pretty simple, really.

But first you have = to know how much you would want it enlarged.  The mixture at = takeoff should be noticeably richer than best power - if you lean at = full throttle on the ground you should see a slight rpm increase.  And yes, the EGT should be at = least 150 ROP.  But what is peak EGT on the ground?  Do you = want to run it in that condition long enough to find out?  You = might want to richen in increments of 5 percent or less, and therein is = the rub.  To richen the mixture 5 percent the diameter must be = increased by only 2.5 percent.  If you are really lucky you might = have a drill just that size - I did - but most likely you will have to = take it to a shop that has reamers that can open it up.  The other = thing to try if you like is to put a radius at the leading edge of the = orifice, which has a chamfer already.  A very slight "break" of the = sharp edge will increase the fuel flow a couple of percent. =  Naturally, you have to keep everything perfectly clean.  The = good thing is that you can test it without flying.  After an = attempt or two you will either have what you want or will be ready to send it off to an "expert" for the adjustment.  You've = "scrapped" the metering orifice, but they're not very = expensive.

The point is that for minor = increases in fuel flow you can make slight changes without much trouble. =  If you overshoot you are back to plan B.  The good news is = that once you have it right it never has to be adjusted again, unlike on = the Continental system.
Gary = Casey

I believe my fuel servo is not delivering = sufficient fuel to the engine in the takeoff position. Why I say this is = because the difference between the peak EGT and the takeoff EGT is 70 = degrees F on the leanest cylinder and 120 on the richest.  The book = says this spread should be anywhere between 150 and 200 degrees F.  = Why do I care you may ask.. Well my CHTs are too high at full throttle takeoff.  I have to work to = keep them below 430.  I have done everything possible to maximize = cooling airflow with little improvement in the CHT = situation.  

Anyhow, I would be interested in = information from the group on the following 

Like to compare = fuel flows at full throttle at close to sea level (mine is between 15 = and 16 gals/hr)
Any info concerning experience with enriching the = takeoff flow on the bendix style RSA-5AD1 servo (this setting is = internal, I have found no reference material on the = procedure)

Thanks
Tom
=

= --Apple-Mail-266--890521154--