Today's Message Index:
----------------------
1. 04:32 AM - Re: RPM Variations - follow up (Thom Riddle)
2. 05:26 AM - Re: RPM Variations - follow up (Roger Lee)
3. 05:51 AM - Re: Re: RPM Variations - follow up (John Fasching)
4. 09:55 AM - Re: Re: RPM Variations - follow up (Richard Girard)
5. 12:49 PM - Re: Re: RPM Variations - follow up (b d)
Message 1
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| Subject: | Re: RPM Variations - follow up |
Too much "precision" in instruments can cause unnecessary concern. The ASI function
in my EIS varies in increments of 24 rpm which tames the readout to meaningful
precision level.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343260#343260
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| Subject: | Re: RPM Variations - follow up |
Hi John,
Out of curiosity what is your max WOT flat and level rpm and what is your cruising
rpm? Let me know and this may have something to do with a 100 rpm swing and
maybe not. How big an up or down? (i.e. 50' pm or 200'pm)
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343268#343268
Message 3
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| Subject: | Re: RPM Variations - follow up |
Roger,
I don't have the precise WOT number at hand, but pretty sure it is 5,650 in
level flight from density altitude 8,500 to 10,500 - seems about the same at
either alt. The Up/down variation seems to be 100-ft or less. The operation
yesterday with the auto pilot holding the plane within 10-ft (as shown on
the Dynon D-180) kept the engine rpm really solid...the most I saw was
10-rpm variations....the Dynon only gives rpms in +/- 10 units, and if rpm
is 'on the cusp' it can 'jump' up and down as the electronics sees which
number is closest.
My cruising rpm is 5,250 - at least that's what I shoot for, and am seeing
4.4 gph at that rpm.
Overall I am happy with the engine's operation...this rpm variation is just
something that I wanted to resolve. In my mind, the pitch changes that I
somehow cause when flying manualy change the load on the engine and results
in some rpm change.
One other thing I see is that when I first start the engine and its oil temp
is in the 60's that the rpm will slowly increase without throttle movement.
After the engine is warmed up that doesn't seem to happen. By the time I get
to the end of the runway and finished my run up and the oil is in the low
120's that 'creep' in rpm is gone.
John
----- Original Message -----
From: "Roger Lee" <ssadiver1@yahoo.com>
Sent: Friday, June 17, 2011 6:24 AM
Subject: RotaxEngines-List: Re: RPM Variations - follow up
>
> Hi John,
>
> Out of curiosity what is your max WOT flat and level rpm and what is your
> cruising rpm? Let me know and this may have something to do with a 100 rpm
> swing and maybe not. How big an up or down? (i.e. 50' pm or 200'pm)
>
> --------
> Roger Lee
> Tucson, Az.
> Light Sport Repairman - Maintenance Rated
> Rotax Repair Center
> Home 520-574-1080 TRY HOME FIRST
> Cell 520-349-7056
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=343268#343268
>
>
>
Message 4
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| Subject: | Re: RPM Variations - follow up |
John, As oil warms it's viscosity becomes less (gets thinner), it takes less
power to pump and RPM goes up. We don't see this in car engines so much
anymore because an ECU can compensate and hold a steady RPM as the engine
warms.
Rick Girard
On Fri, Jun 17, 2011 at 7:47 AM, John Fasching <n29cx@ridgeviewtel.us>wrote:
> n29cx@ridgeviewtel.us>
>
>
> Roger,
>
> I don't have the precise WOT number at hand, but pretty sure it is 5,650 in
> level flight from density altitude 8,500 to 10,500 - seems about the same at
> either alt. The Up/down variation seems to be 100-ft or less. The operation
> yesterday with the auto pilot holding the plane within 10-ft (as shown on
> the Dynon D-180) kept the engine rpm really solid...the most I saw was
> 10-rpm variations....the Dynon only gives rpms in +/- 10 units, and if rpm
> is 'on the cusp' it can 'jump' up and down as the electronics sees which
> number is closest.
>
> My cruising rpm is 5,250 - at least that's what I shoot for, and am seeing
> 4.4 gph at that rpm.
>
> Overall I am happy with the engine's operation...this rpm variation is just
> something that I wanted to resolve. In my mind, the pitch changes that I
> somehow cause when flying manualy change the load on the engine and results
> in some rpm change.
>
> One other thing I see is that when I first start the engine and its oil
> temp is in the 60's that the rpm will slowly increase without throttle
> movement. After the engine is warmed up that doesn't seem to happen. By the
> time I get to the end of the runway and finished my run up and the oil is in
> the low 120's that 'creep' in rpm is gone.
>
> John
>
> ----- Original Message ----- From: "Roger Lee" <ssadiver1@yahoo.com>
> To: <rotaxengines-list@matronics.**com <rotaxengines-list@matronics.com>>
> Sent: Friday, June 17, 2011 6:24 AM
> Subject: RotaxEngines-List: Re: RPM Variations - follow up
>
>
>> >
>>
>> Hi John,
>>
>> Out of curiosity what is your max WOT flat and level rpm and what is your
>> cruising rpm? Let me know and this may have something to do with a 100 rpm
>> swing and maybe not. How big an up or down? (i.e. 50' pm or 200'pm)
>>
>> --------
>> Roger Lee
>> Tucson, Az.
>> Light Sport Repairman - Maintenance Rated
>> Rotax Repair Center
>> Home 520-574-1080 TRY HOME FIRST
>> Cell 520-349-7056
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/**viewtopic.php?p=343268#343268<http://forums.matronics.com/viewtopic.php?p=343268#343268>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
Message 5
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| Subject: | Re: RPM Variations - follow up |
This is true. I am a Control System Engineer and this is a common issue in
all control systems and their I/O. It also is an issue on the outputs which
could be a reading or something like a valve or speed control such as a
governor. Typically there are what is termed "dampening" built into every
instrument to dampen out fast oscillations. This does not effect "precision"
but it adds a "time" component. If yours is digital, look in the menu
options . . . if it has it and it should. In older instrumentation they
would install small orifices in the line to dampen out pulses where liquid
and air medians were used . . . today, the sensors are right on the primary
process such as speed or flow or pressure or temperature . . etc. They see
everything like a magnifying glass and they even pick up noise. You don't
need that, you need an average of the input over time. The dampener gives
you that "time" adjustment. "Precision" is one term and "sensitivity",
"dampening", "sampling rate", "stability"are others. Look for "sensitively"
and/or "dampening". The "precision" is more about how many decimal points to
the right you wish to see, slightly different than the other two terms . . .
why I'm saying this is you may just over look the attribute if you look
only for "precision". In digital electronics there can be computer code that
controls this from a screen or that can be a and adjustable "pot" or
potentiometer. Today you can almost count on computer code . . . again it
depends on the programmer and his knowledge of terminology . . .there are no
absolutes . . . usually "trial and error" sorry to say. "Sampling rate" is
yet another term that can also affect it your reading "stability". Hope that
sheds some light on it better.
Bruce
On Fri, Jun 17, 2011 at 4:29 AM, Thom Riddle <riddletr@gmail.com> wrote:
> >
>
> Too much "precision" in instruments can cause unnecessary concern. The ASI
> function in my EIS varies in increments of 24 rpm which tames the readout to
> meaningful precision level.
>
> --------
> Thom Riddle
> Buffalo, NY (9G0)
> Kolb Slingshot SS-021
> Jabiru 2200A #1574
> Tennessee Prop 64x32
>
> Truth is what stands the test of experience.
> - Albert Einstein
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=343260#343260
>
>
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