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Area-51
Joined: 03 May 2021
Posts: 372
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 Posted: Thu Nov 17, 2022 7:04 pm Post subject: What did you do with your Europa this week - 18/11/22 |
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This week instead of driving three hours through crap traffic, 181 got hauled out and taken into the sky to do the journey in just 75 minutes; without traffic or idiot drivers to deal with.
The journey back was exciting; turning east on departure to cross the bay at 132kt gs, ASI read 80!!!
Then had "washing machine" to contend with, midday thermal activity, mechanical turbulence off mountain ranges to the west, 2500' CTA ceiling, 1700' undulating terrain floor, -500fpm sink, 30C air temperature.... It was 15 minutes of "not fun"... then headed straight back to happy air at the coast once over the ranges and clear of CTA... Pulled up weathX at the field; robot said 90deg xwind gusting 15kt; interesting... got to the field and wind sock said 25kt sea breeze straight down 05; brought 181 in and had a relaxing cup of tea... All the practical training got used...
Today confirmed 50 years of engine tuning skills with the new FART box (Fuel Air Ratio Tester).. What did it reveal??? It said that after 50 years of tuning engines by ear and sense of vibration the skills are still functioning perfectly! The FART confirmed idle mixtures were set spot on at 14.5 Stoichiometric... FART also confirmed main jets were set spot on at 14.5 also... What else did FART reveal?? FART revealed that adjusting the idle mixtures on the Bing carburettor only has affect at 1500rpm and below... FART also revealed that altering the main jet only has affect from 3600rpm upwards... What does this all mean?? It means basically all useful work the 912 does is on the main jet only!! 181 never flies at rpm below 3600; final is flown at 3600 with power pulled back to idle just before round out... between 3600 and 1500 the intermediate needle mixture is on the rich side of 13 down to 11; but this is all ground taxi rpm... What else was confirmed by today's first ever FART experience?? It confirmed fuel injection on the 912 is not required.
What else was learned today? That a good FART box can let anybody FART anywhere!!!
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rparigoris
Joined: 24 Nov 2009
Posts: 780
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| Posted: Thu Nov 17, 2022 7:37 pm Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Hi Area 51
What is your FART smelling for? Carbon Monoxide? Or is it a Oxygen sensor?
For Rotax 914, especially if you have modified the intake 914 (ie intercooler) they recommend that you don't run lean when you dial up War emergency power (115%). They want you to do this by using a Carbon Monoxide tester and checking each cylinder at a time through the EGT port. They want a minimum amount of Carbon Monoxide. So idea is to find leanest cylinder and make sure you are making enough Carbon monoxide. The older style 914 airboxes were more critical to the adjustment of the higher than airbox pressure air used to enrichen by plumbing to float bowls. You adjust so leanest cylinder is rich enough. Sorry, but haven't messed with it on rotax yet. Triumph motorcycles adjust carbon monoxide using that tester before they leave factory.
i installed a oxygen bung and sensor on my 914. I have a fuel air ratio display to let me know how I am doing. I installed a mixture control to allow leaning. I'm leaking carb float bowl pressure via needle valve to cross balance tube. Will verify things with Carbon Monoxide tester and figure leanest cylinder under various throttle settings. I'm slight rich on main jets, jet needle clips. My philosophy is to throw a little more fuel on the fire to keep things cool when generating BTUs. Now, the 94 tends to have a few cylinders run rich at taxi speeds, I plan on running really lean. Above 50% power, will know leanest cylinder at various power settings and lean accordingly. On 914 there is an enriching solenoid that plumbs float bowls to airbox, or higher than airbox pressure. I installed a switch that will activate the solenoid by pilot. I used a schottky diode to isolate power from being backfed into the TCU. Idea is if anything went wrong with lean plumbing, "rich switch" takes it out of circuit.
I too am a long time tuning guy, very satisfying to get things running the way you want them.
Ron P.
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Thu Nov 17, 2022 9:31 pm Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Hi Ron,
The FART is smelling Oxygen.. whether its CO1 or CO2 is irrelevant to me; i just want the FART to tell me how much Oxygen it is smelling; if the FART says 14.5 then i know its a happy FART. As long as my FART is happy i am happy also...
Whether the mixture is observed to be slightly rich during taxi, couldn't care less; its 5-10 minutes of mild operational demand time; and on a hot day it will help keep the engine temp within scale.
You cannot leak boost pressure back through the float needles on a 914 and expect to keep moving; firstly that would intimate that your boost pressure is higher than your fuel pressure; secondly you would run out of fuel on one or both carburettors.
The float chambers need to remain equalised to plenum pressure; if they are leaking air pressure the engine will run lean; hence all the Rotax instructions; and yes you tune to the leanest cylinder always; using an infrared pistol tester on each exhaust header is good enough to indicate this.
Remember you have a lot less room to get it wrong with turbo charging; things go crunch a lot quicker with less warning. If you want to run really lean above 50% power as you mention then firstly you are already going to be at 30% power as a result; so you will give it more throttle; then you will experience more heat, and its all down hill from this point.
Its like performing an engine out glide approach; the airframe has its optimum airspeed for endurance and distance... 14.5 Stoich is that optimum Oxygen content for "all" petrol engines under "all" operating conditions, for maximum thermal efficiency, end of story... and we are talking a balance between tuning for power and economy.
There are numerous ways to diagnose and monitor engine tune; for me its pretty much field experience knowing the different harmonic tones generated by different engine cylinder formations under full and partial load; they indicate air/mixture, spark timing, or mechanical imbalances. The FART is purely a final quality assurance confirmation for me before signing off on maintenance service.
There are endless test points that can be used to monitor an engine; Oil Pressure and Head Temp are the most vital, the rest are nice to haves but not essential and are just early warning meters for the less experienced. If you want perfect analogue economy as good as any fuel injection device then you want to know your manifold pressure and exhaust AFR oxygen content, and maybe add as a cross reference exhaust temperature probe, however to be as accurate as the O2 sensor the EGT probe really should be placed right at the valve throat; so for a 912/914 that's 4 probes.
For a 914 the best practical point to probe EGT is upstream at the impeller, this area between the head and impeller is by default a fairly constant temp environment and will rise and fall according to boost load and is a cross reference point for oil and head temperature meters, the other point i would probe is inlet air temp post intercooler, but personally i would still rely on my O2 readings as a final checkpoint.
All this above will give the operator the insight that the engine, mixture wise, can or cannot run any better than is being indicated.
Keep in mind that AFR O2 readings can be set for max power, max economy, or in the middle and in the middle is 14.5 under load in cruise.
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Sat Nov 19, 2022 6:38 am Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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A very productive week now... finished off the doors on the 3D model; perfect glass and perfect panel gaps in the perfect computer world.. gave the interior some more detail.
Some cleanup tasks, a few amendments and it will be time give some time elsewhere down at the tail.
Very happy with the results; time to put it in primer 😊😊
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Sun Nov 20, 2022 1:26 am Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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The mods keep materialising... Sunday afternoon was spent designing a new firewall solution for 181.
After the crap ordeal changing out fuel hoses recently and the lack of easy access at the firewall section a better option was created today.
Each piece is held in place by just two fixings each and tongue and groove interlocking. The lower section is removable by undoing two setscrews mounted on the inside upright face of the footwell and then sliding it downward. The upper section is fixed by two set screws on the same inside footwell wall and remains in situ and does not require removal until the frame is removed. There is provided a large inspection hatch that is fixed by tongue and groove and two set screws on the top lip of the upper section; removal is from the top once the airbox is out of the way. Apart for the airbox all fixings are accessible for tightening without removing any other items or covers.
Looking forward to fitting this mod when ever the engine is next being removed for any reason.
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dmac7
Joined: 05 Apr 2019
Posts: 46
Location: Canada
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| Posted: Sun Nov 20, 2022 2:52 pm Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Interesting posts Mr Area-51 confirmation is nice. I wonder if changing the needle positions affect cruise mixture much or only mid range? And thats a sweet firewall...
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Sun Nov 20, 2022 8:53 pm Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Thanks; still need to run it through relevant FAR's before production.
Re' adjusting Bing needle position; not going to even bother... If it aint broken, why fix it? But if you want to experiment and know how to proficiently monitor the affects, give it a go!
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Mon Nov 21, 2022 8:21 am Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Away up high in the friendly sky!!
Some finalisation on the engine cowling today... adjusting the radiator ports and shifting the side louvres into place to match actuals.
Also set the flap bar and bumped the flap hinges into final position. Discovered in the process the John had moved the flap bar hinges slightly aft from factory. On paper his mod provides 5deg additional flap angle...
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Area-51
Joined: 03 May 2021
Posts: 372
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| Posted: Tue Nov 22, 2022 9:12 am Post subject: Re: What did you do with your Europa this week - 18/11/22 |
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Passing rearwards today through the wing sections, adding mass balance to the ailerons and bellcrank window, adding in the flap hinge assemblies and finalising the speed kit... gaping and recessing control surfaces; some more work on the engine cowl adding fixing points.
Next will be wing fuselage interface, then its home straight down through the empennage; will be interesting to see what results the digital wind tunnel throws back.
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peterz(at)zutrasoft.com
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| Posted: Tue Nov 22, 2022 9:38 am Post subject: What did you do with your Europa this week - 18/11/22 |
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That's an incredible effort! Looks fantastic!
I'm also eager to see what the fluid dynamics look like!
Thx for doing this!
Cheers,
PeteZ
On Tue, Nov 22, 2022 at 12:19 PM Area-51 <goldsteinindustrial(at)gmail.com (goldsteinindustrial(at)gmail.com)> wrote:
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