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jimlc
Joined: 19 Mar 2007
Posts: 21
Location: Loveland, CO
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 Posted: Sun Jun 17, 2007 5:05 pm Post subject: Impulse Line |
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Hey you'al, what is an impulse line? It is a term I have not encountered
before. When I see something new to me, it is a chance to learn. I have
installed a lot of fuel pumps on aircraft, motor homes, etc., but none had
such a line that I am aware of.
| Quote: | You wrote:
Heavy clear tubing is recommended for impulse line so you can see what is
going on in it.
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Jim Crowder
S5/3300 Jabiru (Engine swap in process)
North Front Range of Colorado
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thesupe(at)hotmail.com
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| Posted: Sun Jun 17, 2007 5:20 pm Post subject: Impulse Line |
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The impulse line goes from the crankcase to the Mikuni fuel pump on a 2
stroke engine. Perhaps some fourstrokes use one, but I don't know about
that for sure.
Jim Chuk
Avid Mk IV
| Quote: | From: "Jim Crowder" <jimlc(at)att.net>
Reply-To: kitfox-list(at)matronics.com
To: "Kitfox List" <kitfox-list(at)matronics.com>
Subject: Impulse Line
Date: Sun, 17 Jun 2007 19:03:58 -0600
Hey you'al, what is an impulse line? It is a term I have not encountered
before. When I see something new to me, it is a chance to learn. I have
installed a lot of fuel pumps on aircraft, motor homes, etc., but none had
such a line that I am aware of.
>You wrote:
>Heavy clear tubing is recommended for impulse line so you can see what is
going on in it.
Jim Crowder
S5/3300 Jabiru (Engine swap in process)
North Front Range of Colorado
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Don’t miss your chance to WIN $10,000 and other great prizes from Microsoft
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jimlc
Joined: 19 Mar 2007
Posts: 21
Location: Loveland, CO
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| Posted: Sun Jun 17, 2007 10:04 pm Post subject: Impulse Line |
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What purpose does it serve? It seems a good way to get fuel into the
crankcase, something I would think was very undesirable. Please understand
I am sure it does serve a purpose, it just is not apparent to me.
Jim Crowder
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Fox5flyer
Guest
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| Posted: Mon Jun 18, 2007 2:24 am Post subject: Impulse Line |
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Jim, as the rear piston comes down it creates a momentary crankcase
pressure that sends this "pulse" of crankcase pressure through the line
(usually typical fuel line) to the Mikuni fuel pump nearby. If the line is
too long the pressure pulse at the pump is diluted. Also, if the pulse line
is too soft, the line can actually expand a little that also dilutes the
pressure at the pump. If that happens the pump doesn't get enough of a
pulse to pump fuel efficiently. What is recommended--if I recall
correctly--is that the line be no more than 12" long and be of a material
that won't expand under the pressure pulses. For this reason, some of the
very soft urethane types aren't suitable as pulse lines.
Hope this helps.
Deke Morisse
N148DM
S5/Soob/CAP
NE Michigan
"Take time to laugh - it is the music of the soul."
---
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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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| Posted: Mon Jun 18, 2007 4:25 am Post subject: Impulse Line |
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At 11:03 PM 6/17/2007, you wrote:
| Quote: | What purpose does it serve?
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Rotax 2-strokes use a pressure driven diaphragm fuel pump. The
"Impulse Line" runs from the crankcase to the drive port of the pump.
The variation in the crankcase pressure in a 2-stroke is sufficient
to drive the pump.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
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Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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thesupe(at)hotmail.com
Guest
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| Posted: Mon Jun 18, 2007 4:41 am Post subject: Impulse Line |
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When the piston comes down you get more pressure in the crankcase, and when
it goes back up, you get less pressure there. The difference in pressure
causes a diaphram in the fuel pump to move back and forth which togeather
with one way valves in the fuel pump alow the pump to work and deliver fuel
to the carbs. Unless that diaphram has a hole in it, no fuel will go into
the crankcase. The impulse line ofcourse alows the fuel pump to feel the
differences in pressure in the crankcase.
Jim Chuk
Avid Mk IV
Chisholm Mn
[quote]From: "Jim Crowder" <jimlc(at)att.net>
Reply-To: kitfox-list(at)matronics.com
To: <kitfox-list(at)matronics.com>
Subject: RE: Impulse Line
Date: Mon, 18 Jun 2007 00:03:22 -0600
What purpose does it serve? It seems a good way to get fuel into the
crankcase, something I would think was very undesirable. Please understand
I am sure it does serve a purpose, it just is not apparent to me.
Jim Crowder
--
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Mon Jun 18, 2007 5:45 am Post subject: Impulse Line |
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Jim:
I waited for the other more experienced people in the group to post answers to your questions.
As they have said the impulse line is a tube that connects the diaphragm pump ( generally Mikuni) to the base of the engine. The base of a two stroke engine acts as the intake manifold for each cylinder and sends pulses of air mixed with fuel/oil to the cylinders. It is possible for some of the fuel/oil to migrate up the impulse line to the pump. If the pump is installed horizontally with the impulse line entering it from the bottom then any of that gas/oil will drain back to the base of the engine when the engine is stopped.
You will find out everything you wanted to know, and a few things you didn't want to know, about two stroke Rotax engines here: http://www.800-airwolf.com/articles.htm
There is even more information available on the great Canadian ultralight page (unabashed national plug) here: http://www.ultralightnews.com/ .
[img]cid:411083913(at)18062007-3416[/img]
Noel Loveys, RPP, AME intern
Campbellton, Newfoundland,
Canada
Kitfox Mod III-A, 582, B box, Ivo IFA
Aerocet 1100s
noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)
Do not archive
[quote] --
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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dwight purdy
Joined: 10 Feb 2006
Posts: 85
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| Posted: Mon Jun 18, 2007 3:32 pm Post subject: Impulse Line |
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I saw a fellow use one on a ea71 subaru pulling an Avid model one. He said
he could shot it eight feet straight up. Thought that was good enough.
Dwight Purdy
model ll
marion IN.
At 01:17 AM 6/18/2007 +0000, you wrote:
| Quote: |
The impulse line goes from the crankcase to the Mikuni fuel pump on a 2
stroke engine. Perhaps some fourstrokes use one, but I don't know about
that for sure.
Jim Chuk
Avid Mk IV
>From: "Jim Crowder" <jimlc(at)att.net>
>Reply-To: kitfox-list(at)matronics.com
>To: "Kitfox List" <kitfox-list(at)matronics.com>
>Subject: Impulse Line
>Date: Sun, 17 Jun 2007 19:03:58 -0600
>
>
>
>Hey you'al, what is an impulse line? It is a term I have not encountered
>before. When I see something new to me, it is a chance to learn. I have
>installed a lot of fuel pumps on aircraft, motor homes, etc., but none had
>such a line that I am aware of.
> >You wrote:
> >Heavy clear tubing is recommended for impulse line so you can see what is
>going on in it.
>
>Jim Crowder
>S5/3300 Jabiru (Engine swap in process)
>North Front Range of Colorado
>
>
_________________________________________________________________
Don't miss your chance to WIN $10,000 and other great prizes from Microsoft
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269.9.0/852 - Release Date: 6/17/2007 8:23 AM
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dwight
model II |
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jimlc
Joined: 19 Mar 2007
Posts: 21
Location: Loveland, CO
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| Posted: Mon Jun 18, 2007 6:24 pm Post subject: Impulse Line |
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Thanks to Noel, Guy, Jim, and Deke, I now for the cost of a few electrons
understand how the impulse line drives the pump. If I missed somebody blame
my advanced age. There has been traffic on the List regarding this for some
time and even though it doesn't apply to me, I needed to know how it worked.
Do Not Archive
Jim Crowder
S5/3300 Jabiru (Engine swap in process)
North Front Range of Colorado
Today I removed the old engine--progress is being achieved on the swap.
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