---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Fri 06/17/11: 5 ---------------------------------------------------------- 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 _____________________________________ Time: 04:32:33 AM PST US Subject: RotaxEngines-List: Re: RPM Variations - follow up From: "Thom Riddle" 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 ________________________________ Message 2 _____________________________________ Time: 05:26:59 AM PST US Subject: RotaxEngines-List: Re: RPM Variations - follow up From: "Roger Lee" 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 _____________________________________ Time: 05:51:06 AM PST US From: "John Fasching" Subject: Re: RotaxEngines-List: 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" 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 _____________________________________ Time: 09:55:54 AM PST US Subject: Re: RotaxEngines-List: Re: RPM Variations - follow up From: Richard Girard 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 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" > To: > > 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 >> >> >> >> >> >> >> >> >> >> >> > > -- 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 _____________________________________ Time: 12:49:34 PM PST US Subject: Re: RotaxEngines-List: Re: RPM Variations - follow up From: b d 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 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 > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.