Today's Message Index:
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1. 10:41 AM - Rejetting a 914 during Winter? (darinh)
2. 05:49 PM - Re: Rejetting a 914 during Winter? (lucien)
3. 05:51 PM - Re: Rejetting a 914 during Winter? (lucien)
4. 09:59 PM - Re: Rejetting a 914 during Winter? (darinh)
Message 1
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| Subject: | Rejetting a 914 during Winter? |
Does anyone rejet their 914 (or 912) during winter? Our summer temps at altitude
(6000' to 8000') are usually in the range of 60 to 80 F, but in the winter
drop to the 20's to around 0 at times. I have noticed ever since the thermometer
started heading south of the freezing line, my engine won't hit my max TO
rpm of 5700 and it seems to run a bit rough at more than 75% throttle setting.
I know that Rotax jets these things for 60F and 1000' msl which is now where
near what I fly at.
My stock jetting (main) is 158 on the left carb and 156 on the right. Looking
at a Bing jetting correction chart for altitude and temp. I am coming up with
recommended jets of 150 and and 148 respectively for 0 to 32F and 6000'.
Can any of you engine gurus tell me if this may be the source of my slightly diminished
engine performance? Also, one last thing that makes me think the engine
is running a bit rich is that if I land at a small strip and shut down right
after landing, it will sometimes backfire on me. If I have to taxi to parking,
the rundown gets all the extra gasoline fumes out and the backfire does not
occur. Seems to me that this says it is a bit on the rich side. Any help
or suggestion is appreciated.
--------
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=222398#222398
Message 2
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| Subject: | Re: Rejetting a 914 during Winter? |
darinh wrote:
> Does anyone rejet their 914 (or 912) during winter? Our summer temps at altitude
(6000' to 8000') are usually in the range of 60 to 80 F, but in the winter
drop to the 20's to around 0 at times. I have noticed ever since the thermometer
started heading south of the freezing line, my engine won't hit my max TO
rpm of 5700 and it seems to run a bit rough at more than 75% throttle setting.
I know that Rotax jets these things for 60F and 1000' msl which is now where
near what I fly at.
>
> My stock jetting (main) is 158 on the left carb and 156 on the right. Looking
at a Bing jetting correction chart for altitude and temp. I am coming up with
recommended jets of 150 and and 148 respectively for 0 to 32F and 6000'.
>
> Can any of you engine gurus tell me if this may be the source of my slightly
diminished engine performance? Also, one last thing that makes me think the engine
is running a bit rich is that if I land at a small strip and shut down right
after landing, it will sometimes backfire on me. If I have to taxi to parking,
the rundown gets all the extra gasoline fumes out and the backfire does
not occur. Seems to me that this says it is a bit on the rich side. Any help
or suggestion is appreciated.
My plane has the 912ULS on it and flies regularly up to close to 10,000' without
any apparent enrichening of the mixture. It runs as smoothly as it did at sea
level, I think the EGT's may be between 50 and 100F lower but that's about all.
The carburettors should take care of it as they're altitude compensating.
One thing that will make them run a little rich is if the little vent tubes on
the sides of the carbs aren't routed to the intake. I.e. if you don't run the
airbox and they're not connected to anything. I ran mine to fittings pressed into
the backs of my air cleaners.
Before I did that, the carbs did run a little rich at full throttle, but nothing
that would cause rough running and etc.....
Doesn't sound normal to me...
LS
--------
LS
Titan II SS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=222467#222467
Message 3
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| Subject: | Re: Rejetting a 914 during Winter? |
Oh, I should actually address your question ;). No, I havn't found the need to
do any rejetting with the change of seasons. In fact, in winter the motor puts
out very slightly more power than during the summer. The EGT's barely change
at all that I can see.
LS
--------
LS
Titan II SS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=222468#222468
Message 4
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| Subject: | Re: Rejetting a 914 during Winter? |
I think I may have found the problem...the cable on my waste gate for the turbo
had stretched a tad bit and needed readjustment. Now if the damn weather would
cooperate long enough for me to fly it I could test it out.
--------
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=222514#222514
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