Today's Message Index:
----------------------
1. 01:08 AM - Re: Full Thorttle Roughness Issue... (lgingell)
2. 03:24 AM - Re: Re: 3300A - Full Throttle Roughness (Lynn Matteson)
3. 07:12 AM - Re: Re: 3300A - Full Throttle Roughness (Andy Silvester)
4. 02:24 PM - Re: Full Thorttle Roughness Issue... (James, Clive R)
5. 03:02 PM - Re: Re: 3300A - Full Throttle Roughness (Peter Harris)
6. 04:47 PM - Re: Re: 3300A - Full Throttle Roughness (j. davis)
7. 08:06 PM - Re: Re: 3300A - Full Throttle Roughness (Don Honabach)
8. 08:29 PM - Re: Full Thorttle Roughness Issue. (Don Honabach)
9. 08:46 PM - Re: Re: 3300A - Full Throttle Roughness (Peter Harris)
10. 11:05 PM - Re: Full Thorttle Roughness Issue. (James, Clive R)
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| Subject: | Re: Full Thorttle Roughness Issue... |
Don,
Other than the smooth 90 degree rubber hose, the other thing I did to solve the
*EXACT* problem you have was to get a smaller MID jet. I think, like David,
I went from a 285 to a 280. I don't have the paperwork with me, but I'm pretty
sure thats what it was.
The jet & the intake are the only things I have changed.
My EGT's looked just like yours in the graph.
..lance
--------
Zodiac XL/Jab 3300
http://lancegingell.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=224867#224867
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| Subject: | Re: 3300A - Full Throttle Roughness |
Andy alerted us to this problem, and when I looked at mine last year,
I found that there was a cast-in ridge that effectively bridges that
gap between the carb and the plenum. Although not a smooth
transition, it does fill the gap and thus avoids the "groove or step"
you mentioned. My 2200 serial number is 2062, delivered in August
2005, just to put it in a time perspective.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 15, 2009, at 12:01 AM, jetboy wrote:
> <sanson.r@xtra.co.nz>
>
> If this is any help I recall reading on the lists about the rubber
> coupling from carb to intake spider having a groove or step inside
> where fuel droplets cavitate and sit in a pool at times of
> operation. some have dealt to this by fitting an 'inner' sleeve
> tapered to make a smooth transition with no step.
>
> Ralph
>
> --------
> Ralph - CH701 / 2200a
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=224860#224860
>
>
Message 3
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| Subject: | Re: 3300A - Full Throttle Roughness |
Lynn,
Actually, the gap between the end of the carb. and the start of the intake
adapter can be a bit of an issue; the rubber coupler which bridges this gap,
which is necessary for vibration isolation, creates a definite groove
(annulus?) into which liquid fuel floods and then exits at any angle
depending on the influence of the airstream going through. One of our OEM
customers did extensive testing using a clear plastic transition and
reported that, at the point of exit from the carb, the fuel is still very
much in liquid form, and not the homogenous fuel/air vapour we might expect
from the theory. Of course, the mixture becomes more (er) mixed as it
travels up the intake tubes but Peter is absolutely right; there is little
opportunity for the fuel / air 'mix' to divide itself 50/50 by the vertical
splitter in the induction in the short distance it travels from the jet,
especially if the air going through the carb. is at all twisting. This extra
(though small) reservoir in the coupling-gap therefore adds to the
uncertainty of how the mixture splits left-and-right, often leading to an
imbalance of mixture at the cylinders. The same OEM fitted oxygen (lambda)
sensors on the 3300's combined exhaust headers (i.e. before the current
individual pipe setup), and found that there could be a ratio of 10:1 on one
side and as high as 16:1 on the other, where Jabiru's own reported 'ideal'
ratio is about 14:1. Interestingly, the lean and rich sides would swap over
as rpm increased, more-or-less proving the view that fuel distribution was
uneven before the splitter. I saw graphs of this a couple of years ago, and
the source of the analysis is impeccable. Now that we have comprehensive
engine monitoring and EGTs on all cylinders, it's easy to see these effects
through the rev. range as you fly. Even better are monitors like the GRT
Horizon/EFIS instrument which can graph EGT in real-time so you can see the
effects of mixture distribution at different power settings.
As I suggested in the post a while back, we found some success by inserting
a filler-ring made of rigid plastic (about the same consistency as the
coupler) which would fill said gap and provide a smoother bore. It wasn't a
complete fix, but definitely improved mixture distribution. Ideally, the
carb delivering into a plenum about 30% of the engine's cubic capacity
should give a better opportunity for fuel and air to mix, but space and
neatness of design precludes this. Jabiru's original plenum on the 2200 and
very few 3300s wasn't a success as the fuel in liquid state would tend to be
thrown to the front of the plenum and then run along the walls and up the
front two intake tubes, so the front cylinders were richer than the back.
Now, if the intake tubes protruded into the plenum by a few mm, the liquid
fuel wouldn't run up 'em, would it?
The experts at Jabiru were fed all this information at the time, but no
doubt had better reasons than me for keeping the design, and why not? It's
theirs!
Andy
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Lynn
Matteson
Sent: 15 January 2009 11:23
Subject: Re: JabiruEngine-List: Re: 3300A - Full Throttle Roughness
Andy alerted us to this problem, and when I looked at mine last year,
I found that there was a cast-in ridge that effectively bridges that
gap between the carb and the plenum. Although not a smooth
transition, it does fill the gap and thus avoids the "groove or step"
you mentioned. My 2200 serial number is 2062, delivered in August
2005, just to put it in a time perspective.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 15, 2009, at 12:01 AM, jetboy wrote:
> <sanson.r@xtra.co.nz>
>
> If this is any help I recall reading on the lists about the rubber
> coupling from carb to intake spider having a groove or step inside
> where fuel droplets cavitate and sit in a pool at times of
> operation. some have dealt to this by fitting an 'inner' sleeve
> tapered to make a smooth transition with no step.
>
> Ralph
>
> --------
> Ralph - CH701 / 2200a
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=224860#224860
>
>
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| Subject: | Full Thorttle Roughness Issue... |
Don, I don't have a functioning EGT but what you describe with RPM and
roughness is just what I'm experiencing on my Esqual with a 3300 Jabiru
#1460. I've only got 15 hours on the engine and am chasing other issues
for now so I'm very interested in the resolution. From what I've heard
in the past and read about the Bing I'm in the main jet size change
solution camp. Very interested in how you get on working the solution.
Regards, Clive
________________________________
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Don
Honabach
Sent: 14 January 2009 16:19
Subject: JabiruEngine-List: Full Thorttle Roughness Issue...
I just wanted to take moment and thank everyone that responded to my
question both on-list and off (WOW - just absolutely amazing the
response - THANK YOU!).
>From the various suggestions I decided that I needed to do a bit more
investigation...
During take-off AND WOT the EGTs on the right side of my engine are
significantly higher than the left. The max difference being ~1400
versus 1100F. However, during cruise, everything tends to even out but
now my left side (or at least cylinders #6 and #4) have higher EGTs than
the right side in general (~1359 verus 1290).
What is interesting is that my max RPM on take-off at WOT is ~2,850 and
there is no roughness at all despite the same EGT profile. In contrast,
when I do WOT in cruise the RPM maxes out at 3,000 and the roughness is
pretty bad and starts at about 2900RPM and gets worse as the RPM
increases. Also, pulling back so that the RPM is less than 2900 always
gets rid of the roughness.
So while the EGT profiles are essentially the same for both WOT
situations, it would appear that when the engine is capable of going
above 2900 RPM that the roughness occurs.
Any thoughts?
If interested, here are the two plot graphs for take-off and full power
cruise:
http://support.pcperfect.com/EGTs-TakeOff.pdf
http://support.pcperfect.com/EGTs-WOT-Cruise.pdf
Thanks!
Don
Message 5
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| Subject: | Re: 3300A - Full Throttle Roughness |
Andy,
That is a very informative post.
I have been testing with a twin injector throttle body feeding an
unobstructed plenum, then for comparison feeding the Jab collector. My
fuel/air mix should be better, in fact I tried 60PSI for greater
atomization, but the charge entered the plenum and too much of the fuel
carried through to over richen #1 and 2 near WOT.
This is an issue independent of the splitter or the type of turbulence.
I think it is happening because near WOT a proportion of the fuel droplets
have enough energy to accelerate through the plenum (or the collector) until
they reach the end.
This is similar to the principle used by Dyson when dust is separated from
the air stream by using it's kinetic energy in a cyclone.
After endless tests I think the problem is due to the fact that we have an
end fed plenum (or collector).
I plan to reconfigure my plenum for bottom feed similar to the 0-200, but
headers will still be unequal and it will not be easy to target the charge
for uniform distribution between the 6 outlets.
Peter
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Andy
Silvester
Sent: Friday, 16 January 2009 1:11 AM
Subject: RE: JabiruEngine-List: Re: 3300A - Full Throttle Roughness
<andy@suncoastjabiru.com>
Lynn,
Actually, the gap between the end of the carb. and the start of the intake
adapter can be a bit of an issue; the rubber coupler which bridges this gap,
which is necessary for vibration isolation, creates a definite groove
(annulus?) into which liquid fuel floods and then exits at any angle
depending on the influence of the airstream going through. One of our OEM
customers did extensive testing using a clear plastic transition and
reported that, at the point of exit from the carb, the fuel is still very
much in liquid form, and not the homogenous fuel/air vapour we might expect
from the theory. Of course, the mixture becomes more (er) mixed as it
travels up the intake tubes but Peter is absolutely right; there is little
opportunity for the fuel / air 'mix' to divide itself 50/50 by the vertical
splitter in the induction in the short distance it travels from the jet,
especially if the air going through the carb. is at all twisting. This extra
(though small) reservoir in the coupling-gap therefore adds to the
uncertainty of how the mixture splits left-and-right, often leading to an
imbalance of mixture at the cylinders. The same OEM fitted oxygen (lambda)
sensors on the 3300's combined exhaust headers (i.e. before the current
individual pipe setup), and found that there could be a ratio of 10:1 on one
side and as high as 16:1 on the other, where Jabiru's own reported 'ideal'
ratio is about 14:1. Interestingly, the lean and rich sides would swap over
as rpm increased, more-or-less proving the view that fuel distribution was
uneven before the splitter. I saw graphs of this a couple of years ago, and
the source of the analysis is impeccable. Now that we have comprehensive
engine monitoring and EGTs on all cylinders, it's easy to see these effects
through the rev. range as you fly. Even better are monitors like the GRT
Horizon/EFIS instrument which can graph EGT in real-time so you can see the
effects of mixture distribution at different power settings.
As I suggested in the post a while back, we found some success by inserting
a filler-ring made of rigid plastic (about the same consistency as the
coupler) which would fill said gap and provide a smoother bore. It wasn't a
complete fix, but definitely improved mixture distribution. Ideally, the
carb delivering into a plenum about 30% of the engine's cubic capacity
should give a better opportunity for fuel and air to mix, but space and
neatness of design precludes this. Jabiru's original plenum on the 2200 and
very few 3300s wasn't a success as the fuel in liquid state would tend to be
thrown to the front of the plenum and then run along the walls and up the
front two intake tubes, so the front cylinders were richer than the back.
Now, if the intake tubes protruded into the plenum by a few mm, the liquid
fuel wouldn't run up 'em, would it?
The experts at Jabiru were fed all this information at the time, but no
doubt had better reasons than me for keeping the design, and why not? It's
theirs!
Andy
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Lynn
Matteson
Sent: 15 January 2009 11:23
Subject: Re: JabiruEngine-List: Re: 3300A - Full Throttle Roughness
Andy alerted us to this problem, and when I looked at mine last year,
I found that there was a cast-in ridge that effectively bridges that
gap between the carb and the plenum. Although not a smooth
transition, it does fill the gap and thus avoids the "groove or step"
you mentioned. My 2200 serial number is 2062, delivered in August
2005, just to put it in a time perspective.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 15, 2009, at 12:01 AM, jetboy wrote:
> <sanson.r@xtra.co.nz>
>
> If this is any help I recall reading on the lists about the rubber
> coupling from carb to intake spider having a groove or step inside
> where fuel droplets cavitate and sit in a pool at times of
> operation. some have dealt to this by fitting an 'inner' sleeve
> tapered to make a smooth transition with no step.
>
> Ralph
>
> --------
> Ralph - CH701 / 2200a
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=224860#224860
>
>
Message 6
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| Subject: | Re: 3300A - Full Throttle Roughness |
Peter Harris wrote:
>
> Andy,
> That is a very informative post.
> I have been testing with a twin injector throttle body feeding an
> unobstructed plenum, then for comparison feeding the Jab collector. My
> fuel/air mix should be better, in fact I tried 60PSI for greater
> atomization, but the charge entered the plenum and too much of the fuel
> carried through to over richen #1 and 2 near WOT.
> This is an issue independent of the splitter or the type of turbulence.
> I think it is happening because near WOT a proportion of the fuel droplets
> have enough energy to accelerate through the plenum (or the collector) until
> they reach the end.
> This is similar to the principle used by Dyson when dust is separated from
> the air stream by using it's kinetic energy in a cyclone.
> After endless tests I think the problem is due to the fact that we have an
> end fed plenum (or collector).
> I plan to reconfigure my plenum for bottom feed similar to the 0-200, but
> headers will still be unequal and it will not be easy to target the charge
> for uniform distribution between the 6 outlets.
> Peter
>
Just wondering... there seems to be a preponderance of posting on this
list that has to do with Bing carb
tuning/jetting/adjusting/modifying/etc. Has anyone considered an
alternative? AeroConversion's AeroCarb comes to mind :') I'm quite happy
with mine (Sonex/3300/AeroCarb), and I know that there are many other
Sonex/3300 drivers that are, also.
--
Regards, J.
-------------------------------------------------
J. Davis, M.Sc. (computer science)
*NIX consulting, SysAdmin
-------------------------------------------------
The day Microsoft makes a product that doesn't suck, is the day they
make a vacuum cleaner.
Message 7
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| Subject: | Re: 3300A - Full Throttle Roughness |
I'd love to hear any real world results of the AeroCarb on Zenith 601s.
I also personally would love a fuel ejected fully computerized control
setup for the 3300 as well!!!!!
Don
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of j.
davis
Sent: Thursday, January 15, 2009 17:45
Subject: Re: JabiruEngine-List: Re: 3300A - Full Throttle Roughness
<jd@lawsonimaging.ca>
Peter Harris wrote:
<peterjfharris@bigpond.com>
>
> Andy,
> That is a very informative post.
> I have been testing with a twin injector throttle body feeding an
> unobstructed plenum, then for comparison feeding the Jab collector. My
> fuel/air mix should be better, in fact I tried 60PSI for greater
> atomization, but the charge entered the plenum and too much of the
fuel
> carried through to over richen #1 and 2 near WOT.
> This is an issue independent of the splitter or the type of
turbulence.
> I think it is happening because near WOT a proportion of the fuel
droplets
> have enough energy to accelerate through the plenum (or the collector)
until
> they reach the end.
> This is similar to the principle used by Dyson when dust is separated
from
> the air stream by using it's kinetic energy in a cyclone.
> After endless tests I think the problem is due to the fact that we
have an
> end fed plenum (or collector).
> I plan to reconfigure my plenum for bottom feed similar to the 0-200,
but
> headers will still be unequal and it will not be easy to target the
charge
> for uniform distribution between the 6 outlets.
> Peter
>
Just wondering... there seems to be a preponderance of posting on this
list that has to do with Bing carb
tuning/jetting/adjusting/modifying/etc. Has anyone considered an
alternative? AeroConversion's AeroCarb comes to mind :') I'm quite happy
with mine (Sonex/3300/AeroCarb), and I know that there are many other
Sonex/3300 drivers that are, also.
--
Regards, J.
-------------------------------------------------
J. Davis, M.Sc. (computer science)
*NIX consulting, SysAdmin
-------------------------------------------------
The day Microsoft makes a product that doesn't suck, is the day they
make a vacuum cleaner.
Checked by AVG - http://www.avg.com
1/15/2009 07:46
Message 8
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| Subject: | Full Thorttle Roughness Issue. |
Clive,
I've had some positive results in fixing my roughness issue, but I'm
still working out the details.
Here's what I've got so far...
I appear to have an air intake issue. Flying without the air intake
system and just the carb open to the cowling area and the plane flies
extremely smooth. This fixed the roughness for everything except the
last 1/4" of throttle travel. Repitching the prop so I had an in flight
max of ~3300 RPM fixed the last 1/4" of roughness. Before the pitch
change, my max out in straight and level was 3000 RPM.
I'm going to be installing various modified air intake setups over the
next few weeks and will post my results.
For what it's worth, after re-pitching and flying without the air intake
system, the plane is amazing. I've gained about 5 to 10 MPH in speed and
300 feet per minute or more in climb and the engine is much smoother in
all RPM ranges. I'm really excited about getting a good intake system
designed :) now that I'm seen the "other side" of this engine.
Don
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of
James, Clive R
Sent: Thursday, January 15, 2009 15:22
Subject: RE: JabiruEngine-List: Full Thorttle Roughness Issue.
Don, I don't have a functioning EGT but what you describe with RPM and
roughness is just what I'm experiencing on my Esqual with a 3300 Jabiru
#1460. I've only got 15 hours on the engine and am chasing other issues
for now so I'm very interested in the resolution. From what I've heard
in the past and read about the Bing I'm in the main jet size change
solution camp. Very interested in how you get on working the solution.
Regards, Clive
________________________________
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Don
Honabach
Sent: 14 January 2009 16:19
Subject: JabiruEngine-List: Full Thorttle Roughness Issue...
I just wanted to take moment and thank everyone that responded to my
question both on-list and off (WOW - just absolutely amazing the
response - THANK YOU!).
>From the various suggestions I decided that I needed to do a bit more
investigation...
During take-off AND WOT the EGTs on the right side of my engine are
significantly higher than the left. The max difference being ~1400
versus 1100F. However, during cruise, everything tends to even out but
now my left side (or at least cylinders #6 and #4) have higher EGTs than
the right side in general (~1359 verus 1290).
What is interesting is that my max RPM on take-off at WOT is ~2,850 and
there is no roughness at all despite the same EGT profile. In contrast,
when I do WOT in cruise the RPM maxes out at 3,000 and the roughness is
pretty bad and starts at about 2900RPM and gets worse as the RPM
increases. Also, pulling back so that the RPM is less than 2900 always
gets rid of the roughness.
So while the EGT profiles are essentially the same for both WOT
situations, it would appear that when the engine is capable of going
above 2900 RPM that the roughness occurs.
Any thoughts?
If interested, here are the two plot graphs for take-off and full power
cruise:
http://support.pcperfect.com/EGTs-TakeOff.pdf
http://support.pcperfect.com/EGTs-WOT-Cruise.pdf
Thanks!
Don
href="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.
m
atronics.com/Navigator?JabiruEngine-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
Checked by AVG - http://www.avg.com
1/15/2009 07:46
Message 9
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| Subject: | Re: 3300A - Full Throttle Roughness |
J
I would recommend against using Aerocarb especially on the J3300 based on
personal experience. I was supplied with an Aerocarb with no Teflon liner.
The slide worked on anodized metal to metal and jammed hard.
The slide is pulled and pushed by an outrigged lever which causes the slide
to twist and jam whenever pressure is applied. The attachment to cable is
off centre and not even co planar with the slide.
A Teflon liner is offered on the website but my several requests were
ignored.
I packed it with grease but it still jammed under the vacuum at low throttle
settings and any attempt to quickly open throttle for a missed approach
makes it jam harder because of the offset cable attachment.
I attempted to discuss changes to the design but was abused. I have a copy
of the correspondence.
When I asked for a refund I was told to sell it on eBay.
I would not have the conscience to give it away .
Peter
-----Original Message-----
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of j. davis
Sent: Friday, 16 January 2009 10:45 AM
Subject: Re: JabiruEngine-List: Re: 3300A - Full Throttle Roughness
Peter Harris wrote:
<peterjfharris@bigpond.com>
>
> Andy,
> That is a very informative post.
> I have been testing with a twin injector throttle body feeding an
> unobstructed plenum, then for comparison feeding the Jab collector. My
> fuel/air mix should be better, in fact I tried 60PSI for greater
> atomization, but the charge entered the plenum and too much of the fuel
> carried through to over richen #1 and 2 near WOT.
> This is an issue independent of the splitter or the type of turbulence.
> I think it is happening because near WOT a proportion of the fuel droplets
> have enough energy to accelerate through the plenum (or the collector)
until
> they reach the end.
> This is similar to the principle used by Dyson when dust is separated from
> the air stream by using it's kinetic energy in a cyclone.
> After endless tests I think the problem is due to the fact that we have an
> end fed plenum (or collector).
> I plan to reconfigure my plenum for bottom feed similar to the 0-200, but
> headers will still be unequal and it will not be easy to target the charge
> for uniform distribution between the 6 outlets.
> Peter
>
Just wondering... there seems to be a preponderance of posting on this
list that has to do with Bing carb
tuning/jetting/adjusting/modifying/etc. Has anyone considered an
alternative? AeroConversion's AeroCarb comes to mind :') I'm quite happy
with mine (Sonex/3300/AeroCarb), and I know that there are many other
Sonex/3300 drivers that are, also.
--
Regards, J.
-------------------------------------------------
J. Davis, M.Sc. (computer science)
*NIX consulting, SysAdmin
-------------------------------------------------
The day Microsoft makes a product that doesn't suck, is the day they
make a vacuum cleaner.
Message 10
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| Subject: | Full Thorttle Roughness Issue. |
Thanks Don, mine is just the last bit and only at high revs. In the
climb at 2800 it's smooth enough but then that a different situation to
3000 plus.
I will drop off the scat from the carb for elimination of that issue,
that's a great idea.
I have oversized scat tube on the carb which I'm hoping will help with
airflow but then I suppose that could be the cause.
Regards, Clive
________________________________
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Don
Honabach
Sent: 16 January 2009 04:27
Subject: RE: JabiruEngine-List: Full Thorttle Roughness Issue.
Clive,
I've had some positive results in fixing my roughness issue, but I'm
still working out the details.
Here's what I've got so far...
I appear to have an air intake issue. Flying without the air intake
system and just the carb open to the cowling area and the plane flies
extremely smooth. This fixed the roughness for everything except the
last 1/4" of throttle travel. Repitching the prop so I had an in flight
max of ~3300 RPM fixed the last 1/4" of roughness. Before the pitch
change, my max out in straight and level was 3000 RPM.
I'm going to be installing various modified air intake setups over the
next few weeks and will post my results.
For what it's worth, after re-pitching and flying without the air intake
system, the plane is amazing. I've gained about 5 to 10 MPH in speed and
300 feet per minute or more in climb and the engine is much smoother in
all RPM ranges. I'm really excited about getting a good intake system
designed :) now that I'm seen the "other side" of this engine.
Don
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of
James, Clive R
Sent: Thursday, January 15, 2009 15:22
Subject: RE: JabiruEngine-List: Full Thorttle Roughness Issue.
Don, I don't have a functioning EGT but what you describe with RPM and
roughness is just what I'm experiencing on my Esqual with a 3300 Jabiru
#1460. I've only got 15 hours on the engine and am chasing other issues
for now so I'm very interested in the resolution. From what I've heard
in the past and read about the Bing I'm in the main jet size change
solution camp. Very interested in how you get on working the solution.
Regards, Clive
________________________________
From: owner-jabiruengine-list-server@matronics.com
[mailto:owner-jabiruengine-list-server@matronics.com] On Behalf Of Don
Honabach
Sent: 14 January 2009 16:19
Subject: JabiruEngine-List: Full Thorttle Roughness Issue...
I just wanted to take moment and thank everyone that responded to my
question both on-list and off (WOW - just absolutely amazing the
response - THANK YOU!).
>From the various suggestions I decided that I needed to do a bit more
investigation...
During take-off AND WOT the EGTs on the right side of my engine are
significantly higher than the left. The max difference being ~1400
versus 1100F. However, during cruise, everything tends to even out but
now my left side (or at least cylinders #6 and #4) have higher EGTs than
the right side in general (~1359 verus 1290).
What is interesting is that my max RPM on take-off at WOT is ~2,850 and
there is no roughness at all despite the same EGT profile. In contrast,
when I do WOT in cruise the RPM maxes out at 3,000 and the roughness is
pretty bad and starts at about 2900RPM and gets worse as the RPM
increases. Also, pulling back so that the RPM is less than 2900 always
gets rid of the roughness.
So while the EGT profiles are essentially the same for both WOT
situations, it would appear that when the engine is capable of going
above 2900 RPM that the roughness occurs.
Any thoughts?
If interested, here are the two plot graphs for take-off and full power
cruise:
http://support.pcperfect.com/EGTs-TakeOff.pdf
http://support.pcperfect.com/EGTs-WOT-Cruise.pdf
Thanks!
Don
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1/15/2009 07:46
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