 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
don(at)pcperfect.com
Guest
|
 Posted: Wed Jan 14, 2009 8:19 am Post subject: 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
[quote][b]
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
 |
Lynn Matteson
Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan
|
| Posted: Wed Jan 14, 2009 10:49 am Post subject: Full Thorttle Roughness Issue... |
|
|
Don, have you modified the carb so that the throttle goes completely
wide open? This is a no-no, I'm told, and I think it is said that it
will lead to roughness at WOT if you do this. I understand that the
throttle should stop just short of a full 90 degree opening. Somebody
else who has the full story should comment....Pete? Jim? Andy?
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 14, 2009, at 11:18 AM, Don Honabach wrote:
| Quote: | 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
============================================================ _-
============================================================ _-
contribution_-
============================================================
|
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM |
|
| Back to top |
|
|
andy(at)suncoastjabiru.co
Guest
|
| Posted: Wed Jan 14, 2009 11:21 am Post subject: Full Thorttle Roughness Issue... |
|
|
This goes back to about 1996, with the first 2200s and the induction plenum.
Jabiru were head-scratching for a while trying to find out why (only some)
engines were running rough at WOT (my original 2200 powered Jabiru SK did)
and in the end found out the solution from BMW motorcycles. They also used
the 32mm CV carburettor and had a restriction at (I seem to recall) 75
degrees open for WOT, instead of 90 degrees, claiming that at 90 deg., the
bike would run rough......We deduced it had to do with turbulence over the
butterfly's assembly when edge-on to the flow. Since then, the throttle arm
on the carb. is made to restrict opening. However, since machined splitter
intakes and other developments, I personally doubt this is still an issue,
but then I haven't removed the restriction just to see what happens. My
money is on main-jet mixture if the engine runs rough at WOT.
Regards, Andy
--
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
|
Peter H
Joined: 20 Mar 2007
Posts: 197
|
| Posted: Wed Jan 14, 2009 2:40 pm Post subject: Full Thorttle Roughness Issue... |
|
|
Don,
During static runs and during climb at WOT the manifold pressure is relatively close to 1 atmosphere but as the aircraft accelerates the vacuum increases and manifold pressure goes down .
As manifold pressure varies, the distribution of the fuel/air mix through the collector varies, and similarly as the velocity of incoming air increases the turbulence and pressure profile through the system also varies. Alignment of the butterfly also alters the distribution to R or L because of the central vane in the collector.
Possibly removing that vane would improve the situation, but that would be a challenge to the original development.
Like you I have also watched as EGT goes moves to favour R or L as the plane accelerates to max cruise and on a couple of occasions encountered extreme roughness due to the engine “boxing” with uneven power R to L due to the difference in mixture. The engine started shaking.
But if you follow Pete’s advice you should eventually find a setting that is satisfactory. The charge distribution is never going to be perfect throughout the power range .
Peter.
From: owner-jabiruengine-list-server(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of Don Honabach
Sent: Thursday, 15 January 2009 2:19 AM
To: jabiruengine-list(at)matronics.com
Subject: 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
| Quote: | | http://www.matronics.com/Navigator?JabiruEngine-List |
0123456789
[quote][b]
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
|
Peter H
Joined: 20 Mar 2007
Posts: 197
|
| Posted: Wed Jan 14, 2009 2:46 pm Post subject: Full Thorttle Roughness Issue... |
|
|
Lynn
That advice confirms my experience that WOT causes excess fuel to go to the
end of the collector enriching #1 and #2 but I believe that this is due to
the design of the collector and is costing power.
Peter.
--
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
|
lgingell
Joined: 10 Jan 2006
Posts: 50
Location: Lake California Airpark 68CA
|
| Posted: Thu Jan 15, 2009 1:06 am Post 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
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
_________________
Zodiac XL/Jab 3300
http://lancegingell.com |
|
| Back to top |
|
|
Clive J
Joined: 03 Nov 2007
Posts: 340
Location: UK
|
| Posted: Thu Jan 15, 2009 2:24 pm Post 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(at)matronics.com [mailto:owner-jabiruengine-list-server(at)matronics.com] On Behalf Of Don Honabach
Sent: 14 January 2009 16:19
To: jabiruengine-list(at)matronics.com
Subject: 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
[quote]
href="http://www.matronics.com/Navigator?JabiruEngine-List">http://www.matronics.com/Navigator?JabiruEngine-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
[b]
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
|
dbrown(at)avecc.com
Guest
|
| Posted: Fri Jan 16, 2009 6:24 am Post subject: Full Thorttle Roughness Issue... |
|
|
List,
On a similar note that don has observed, a month or so ago I was doing a
touch and go when I inadvertently left the carb heat on. While making
the climb out I noticed that the EGT's and CHT's had all evened out and
looked the best that they ever had. I now wonder if it was warm air
causing better atomization, or just the air intake system. Has any one
else noticed this and if so what are you thoughts.
David
N601EX Jab3300
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
| | - The Matronics JabiruEngine-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?JabiruEngine-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
