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02-02-2016, 03:03 PM
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Join Date: Jun 2006
Posts: 316
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Up draft 540 sump
[quote=rv6ejguy;1049145]Here's what we're up against with typical vertical induction Lycomings:
Bad pairings, unequal shapes, small plenum volume and unequal runner lengths.
This one
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02-02-2016, 04:55 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Interesting. And is there a only 1.3% flow difference between .0245 and .0255 nozzles even though there is an 8% area difference?
Last edited by rv6ejguy : 02-02-2016 at 05:23 PM.
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02-02-2016, 07:19 PM
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Join Date: Jun 2006
Posts: 316
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The division of flow between the injector nozzles with the interaction of the flow divider for this installation goes like this:
Cyl #1 16.8%, Cyl #2 17.5%, cyl #3 16.1%, cyl #4 16.1%, cyl #5 16.8%, cyl #6 16.8%
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02-02-2016, 07:33 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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I guess I don't understand how this mechanical injection system works. On Kinsler types that I played with eons ago, going from a .024 to a .025 nozzle was around a 6.5% flow change for an 8% area change at a fixed 30 psi.
I am guessing to get the numbers above, you flow the whole setup on a test bench and measure the flow amounts from each injector individually?
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02-02-2016, 07:46 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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Quote:
Originally Posted by rv6ejguy
I guess I don't understand how this mechanical injection system works. On Kinsler types that I played with eons ago, going from a .024 to a .025 nozzle was around a 6.5% flow change for an 8% area change at a fixed 30 psi.
I am guessing to get the numbers above, you flow the whole setup on a test bench and measure the flow amounts from each injector individually?
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DanH has a good article on fuel injection systems in this months Kitplane. I was surprised to learn the flow divider had that much influence on the operation too.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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02-02-2016, 08:32 PM
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Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
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Quote:
Originally Posted by BillL
DanH has a good article on fuel injection systems in this months Kitplane. I was surprised to learn the flow divider had that much influence on the operation too.
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I guess there is more to it than meets the eye on the outside. I need to pick up a copy and learn some more then...
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02-02-2016, 10:09 PM
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Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,574
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a few comments looking back at the whole thread
I've really enjoyed following this, and learning along the way.
I am really happy that the initial issue lead to an increased capability in the EFII system that solved the problem. I thought it interesting that Ross was open-minded enough to make the change after earlier saying that it was a mask for the root problem. He was likely correct, but was open to the 'symptomatic relief' anyway to address a common systematic problem.
Yes, it would be great if we all had manifolds that flowed well and evenly.
I feel pretty lucky to have the angle-valve horizontal induction manifold which does seem to flow very evenly, right out of the box. My GAMMI spread is less than 0.2 gph, right out of the box. No doubt the plenum volume, and runner design is a big part of that.
Interesting that the fuel divider plays much of a role at cruise fuel flows. It has a pretty symmetrical geometry.
Excuse the thread drift here for a funny story:
I got a huge chuckle out of DanH bringing up the Bosch D-jetronic. I spent a lot of time fussing and toying with the D-jetronic on my 1971 Volvo 1800E race car. I really hated it. Its fundamental problem was relying on manifold pressure, rather than a direct measurement of airflow. A real challenge for the old analog computer box was that airflow is a non-linear function of manifold pressure. The manifold pressure sensor was pretty low quality by todays standards. A small error in manifold pressure near WOT would give a very incorrect mixture. But the bigger issue for me was that it is completely un-adaptable to changes in engine breathing. Improved breathing means more airflow at the same MAP, and so it got leaner as I improved the engine. Eventually, it had a horrible lean spot at the RPM where the induction tuning gave the best flow, to the point where it would miss. I tried adding a trim pot in the computer box to bias the mixture, and I tried fudging the calibration of the MAP sensor. Marginally solved the issue, but never perfect. And then, trying to get it to pass California smog tests. I will spare you all the onslaught of swear words I've directed at the D-Jetronic over the years.
My final solution was to find a Bosch K-Jetronic system off of a 1975 Volvo. What a wonderful system that was. It used a direct mass-flow sensor, and a constant-flow injection. (sound familiar?) That made the system much more amenable to engine changes. My engine finally ran right, delivering about 170 hp on 94 (R+M)/2 gas from an old B-20 overhead-valve motor. Not much by todays standards, of course.
That system was so versatile that it was the backbone of the first (or one of the first) production FI systems with a closed-loop mixture trim from an O2 sensor. It was called Lambda-sond. I think it was the first, but could be wrong.
Anyway, just thought I'd share that -- The old CIS, whether it be Bosch or Bendix, is not a bad way to go.
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 625
LS6-15/18W sailplane SOLD
bought my old LS6-A back!! 
VAF donation Jan 2020
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02-03-2016, 05:09 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Interesting photo. Plenum volume and runner taper isn't the only thing the Murrays are doing differently.
Check out the injector port location (inside the bend, not outboard), alignment (pointed toward the intake port, not away from it), and port style (positive injector retention).
This set of runners are not likely to be for Dave Anders, as there are six of them.
Photos shamelessly borrowed from the SDS website:

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Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 02-03-2016 at 05:11 AM.
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02-03-2016, 06:57 AM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by DanH
...This set of runners are not likely to be for Dave Anders, as there are six of them...
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That's what I thought too, but upon closer inspection it looks like 4 induction tubes and one exhaust (showing the O2 sensor bung).
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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02-03-2016, 07:09 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Toobuilder
That's what I thought too, but upon closer inspection it looks like 4 induction tubes and one exhaust (showing the O2 sensor bung).
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Aahhh...you're right.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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