Today's Message Index:
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1. 01:18 PM - Radiator Hose for Intake and 1,3,5 lean (MHerder)
2. 06:47 PM - Re: Radiator Hose for Intake and 1,3,5 lean (Martin Hone)
3. 07:22 PM - Re: Radiator Hose for Intake and 1,3,5 lean (Lynn Matteson)
4. 09:56 PM - Re: Radiator Hose for Intake and 1,3,5 lean (ple190)
Message 1
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| Subject: | Radiator Hose for Intake and 1,3,5 lean |
Hey guys,
Scenario:
Jab 3300, wood 64x47 Zodiac 601 HD.
Recently rejetted from a .255 to .250 b/c I was running rich at high end.
Flew it for about 5-10 hrs with the .250 in it, all was good, left bank was a little
on the lean side and I was getting about 3100 rpm level at cruise on a good
day.
Decided last night to try to remove the scat hose from intake and replace with
smooth lined radiator hose 2 1/8" diameter, and nice smooth molded 90 degree bend
from airbox.
I had expectations that I would get more power, and more even distribution of fuel,
the exact opposite happened. One bank is now running even leaner, and much
to my supprise I was lucky to get 2850 rpm today. I'm kind of bummed about
this. What gives?
My thoughts are that now that I'm getting more air to the engine, maybe my mixture
might actually be too lean. But the reality is I have one rich bank and
one low bank with egts ranging from 1080-1150 on 1,3,5 to 13-1350 on 2,4,6. The
average of them is about right, but there is a pretty big desparity. As a
side note everything is very happy and even at cruise 2200-2500. The measurements
I'm giving are MWOT, which is really where I want to dial it in and get
the most pwr. It seems what I really need is better and more distribution of
the fuel/air I am sending into the manifold, not necissarily more or less fuel.
So I've changed back to the .255 main. I did one high speed taxi like this but
it was too windy to fly so I didn't get any good data.
WHAT ELSE COULD IT BE. Anyone else switch to a smooth intake hose and have to
readjust?
--------
One Rivet at a Time!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=333642#333642
Message 2
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| Subject: | Re: Radiator Hose for Intake and 1,3,5 lean |
Hi Michael,
Sounds like you have made a pretty poor situation worse, The plenum design
on the 3.3 is the cause of a lot of mixture related issues. I know of some
that have had some success by simply rotating the carb a few degrees while
others have designed and built their own plenum and intake runners.. There
is also a mod that removes the flow divider in the plenum and replaces it
with a half inch round tube. But you only have to look and see the
different inlet runner lengths to see part of the problem. I know that
Rotec have designed a plenum and intake runner system that mates to its TBI,
that replicates something you would find on a Lycoming.
Obviously your smooth intake mod has upset the flow going into the carb and
probably biased the fuel spray pattern to one side. You could try twisting
the carb slightly so that the fuel leaving the needle jet is aimed more to
the lean bank of cylinders.....
Martin
On Sun, Mar 13, 2011 at 7:15 AM, MHerder <michaelherder@beckgroup.com>wrote:
> michaelherder@beckgroup.com>
>
> Hey guys,
>
> Scenario:
> Jab 3300, wood 64x47 Zodiac 601 HD.
>
> Recently rejetted from a .255 to .250 b/c I was running rich at high end.
>
> Flew it for about 5-10 hrs with the .250 in it, all was good, left bank was
> a little on the lean side and I was getting about 3100 rpm level at cruise
> on a good day.
>
>
> Decided last night to try to remove the scat hose from intake and replace
> with smooth lined radiator hose 2 1/8" diameter, and nice smooth molded 90
> degree bend from airbox.
>
> I had expectations that I would get more power, and more even distribution
> of fuel, the exact opposite happened. One bank is now running even leaner,
> and much to my supprise I was lucky to get 2850 rpm today. I'm kind of
> bummed about this. What gives?
>
> My thoughts are that now that I'm getting more air to the engine, maybe my
> mixture might actually be too lean. But the reality is I have one rich
> bank and one low bank with egts ranging from 1080-1150 on 1,3,5 to 13-1350
> on 2,4,6. The average of them is about right, but there is a pretty big
> desparity. As a side note everything is very happy and even at cruise
> 2200-2500. The measurements I'm giving are MWOT, which is really where I
> want to dial it in and get the most pwr. It seems what I really need is
> better and more distribution of the fuel/air I am sending into the manifold,
> not necissarily more or less fuel.
>
> So I've changed back to the .255 main. I did one high speed taxi like
> this but it was too windy to fly so I didn't get any good data.
>
> WHAT ELSE COULD IT BE. Anyone else switch to a smooth intake hose and have
> to readjust?
>
> --------
> One Rivet at a Time!
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=333642#333642
>
>
Message 3
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| Subject: | Re: Radiator Hose for Intake and 1,3,5 lean |
Michael-
First off, if 1,3, and 5 are 1080-1150, that's NOT lean, that's rich.
The 2,4, and 6 at 13-1350 is on the lean side....unless it is late,
and my brain is fried.
To further explain what Martin is saying...imagine that the spray of
fuel leaving the carb is positioned at the 6 o'clock position inside
the carb (it is, actually). If the lean bank is 2,4, and 6, you need
to rotate the carb bottom so that the 6 o'clock moves toward the
2,4,6 bank of cylinders....this would be toward the 7 o'clock
position in your 601/ tractor installation. This rotation will make
the fuel discharge go on the left side of the flow divider, richening
the left bank of cylinders...the 2,4,6 side. When I was running a
Bing, I made a small pointer that I affixed near the carb and then
made a scratch on the carb so I would have a starting point and could
always return there if I needed to. Be aware that it doesn't take
much of a twist of the carb to make a big difference.
Further, is that 90 degree bend a vertical bend? According to the
wisdom (?) of about 5 years ago, the Bing likes to get its air from
above or below the carb and not coming in from the side. If your new
smooth hose comes to the carb from the side, that alone might have
caused the problem you are now having.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062
Prince prop (64 x 30, P-tip)
Electroair direct-fire ignition system
Rotec TBI-40 injection (sleeved to 35mm)
Status: flying...1086 hrs (since 3-27-2006)
On Mar 12, 2011, at 9:43 PM, Martin Hone wrote:
> Hi Michael,
>
> Sounds like you have made a pretty poor situation worse, The
> plenum design on the 3.3 is the cause of a lot of mixture related
> issues. I know of some that have had some success by simply
> rotating the carb a few degrees while others have designed and
> built their own plenum and intake runners.. There is also a mod
> that removes the flow divider in the plenum and replaces it with a
> half inch round tube. But you only have to look and see the
> different inlet runner lengths to see part of the problem. I know
> that Rotec have designed a plenum and intake runner system that
> mates to its TBI, that replicates something you would find on a
> Lycoming.
> Obviously your smooth intake mod has upset the flow going into the
> carb and probably biased the fuel spray pattern to one side. You
> could try twisting the carb slightly so that the fuel leaving the
> needle jet is aimed more to the lean bank of cylinders.....
>
> Martin
>
> On Sun, Mar 13, 2011 at 7:15 AM, MHerder
> <michaelherder@beckgroup.com> wrote:
> <michaelherder@beckgroup.com>
>
> Hey guys,
>
> Scenario:
> Jab 3300, wood 64x47 Zodiac 601 HD.
>
> Recently rejetted from a .255 to .250 b/c I was running rich at
> high end.
>
> Flew it for about 5-10 hrs with the .250 in it, all was good, left
> bank was a little on the lean side and I was getting about 3100 rpm
> level at cruise on a good day.
>
>
> Decided last night to try to remove the scat hose from intake and
> replace with smooth lined radiator hose 2 1/8" diameter, and nice
> smooth molded 90 degree bend from airbox.
>
> I had expectations that I would get more power, and more even
> distribution of fuel, the exact opposite happened. One bank is now
> running even leaner, and much to my supprise I was lucky to get
> 2850 rpm today. I'm kind of bummed about this. What gives?
>
> My thoughts are that now that I'm getting more air to the engine,
> maybe my mixture might actually be too lean. But the reality is I
> have one rich bank and one low bank with egts ranging from
> 1080-1150 on 1,3,5 to 13-1350 on 2,4,6. The average of them is
> about right, but there is a pretty big desparity. As a side note
> everything is very happy and even at cruise 2200-2500. The
> measurements I'm giving are MWOT, which is really where I want to
> dial it in and get the most pwr. It seems what I really need is
> better and more distribution of the fuel/air I am sending into the
> manifold, not necissarily more or less fuel.
>
> So I've changed back to the .255 main. I did one high speed taxi
> like this but it was too windy to fly so I didn't get any good data.
>
> WHAT ELSE COULD IT BE. Anyone else switch to a smooth intake hose
> and have to readjust?
>
> --------
> One Rivet at a Time!
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=333642#333642
>
>
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Message 4
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| Subject: | Re: Radiator Hose for Intake and 1,3,5 lean |
Have you tried a cross insert in the airbox outlet pipe, this has helped a lot
of people even out their EGT's. Just epoxy in some .5mm Al or use thin glass
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=333697#333697
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