Wes's Onex #89

[builderflyer]

Hey guys, sorry to burst your bubble, but I don’t fly a Jabiru.

I fly a CORVAIR!!!!!!!
.

Sorry, I missed the part where you said your "absolute EGT values mean nothing" comments only applied to the Corvair engine and not to other engines more typically found on the Sonex. In particular, I didn't want those flying behind Jabiru engines to be mislead.

Art,,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,,Jabiru 3300 #261

[WesRagle]

Hi Guys,

Sorry, I missed the part where you said your "absolute EGT values mean nothing" comments only applied to the Corvair engine and not to other engines more typically found on the Sonex. In particular, I didn't want those flying behind Jabiru engines to be mislead.

Yea Nate, you gota admit you were a little obscure on that point. I'm a little slow on the uptake. I re-read the thread looking for where you said that. I've been married for a loooong time. I should recognize passive aggressive when I see it ;-)

I'm going to make a plug for signatures on posts. It's easy to go to "User Control Panel>Profile>Edit signature" and enter your name, aircraft model, engine, prop,... It adds context to any posts you make.

Wes

[Direct C51]

This does not apply to just a Corvair. I was only pointing that out because I’m not sure the Jabiru can run LOP well, with the stock heads and intake manifold.

[WesRagle]

Hi Guys,

I'm back from a long postponed vacation and can now get back to the Onex.

After approximately 16 hrs "time in type" I finally got up the nerve to call for insurance. It wasn't pretty, $1,482.00 for full coverage. I'll drop to liability only next year. So, with a little confidence and fully insured, I brought the Onex to civilization. A quick 30 min. flight and now the airplane is 20 miles from home instead of 85 miles from home.

It will be much easier to work on tweaks now.

With an OAT of approximately 50 Deg. today the oil temperature was only 160 Deg. F. in cruise. Tomorrow I'll de-mod the oil cooler inlet to remove the scoop I had to add this Summer before the engine was broken in. Next I'll get back to puzzling over that one cylinder running significantly hotter than the others.



Forever Forward,

Wes

[WesRagle]

Hi Guys,

The board has been a little quite so I'll yak some.

I finally got around to checking the timing on the Hummel. The primary (mag) was advanced a bit and the secondary was retarded a bit. I ended up adjusting the secondary to match the primary. I am running just a tad advanced but I don't want to retard the timing because that would cause the EGT to rise. Anyway, much smoother with the ignitions at least somewhat matched.

I took an 86 mile cruise this morning at 3000 RPM. Including climb and landing, it took 46 minutes and 4 gallons of gas. I still need to do speed runs but have been busy tweaking the mixture and timing.

OAT 55
Altitude 3500
RPM 3000
Oil Temperature 185
Hottest CHT 310
Hottest EGT 1300

The hottest EGT and hottest CHT are on the right rear. Like I said earlier, that cylinder is significantly hotter than the left rear. I know the subject has been beat to death, but I do wish I could balance the front and rear cylinders mixtures better.

I think I'm going to call the timing and mixture "Good Enough". I need to clean the plane up, do a first final polish :-), torque the heads, set the valve lash, and just have some fun flying. I've only flown "Cross Country" for two or three hours. The airplane is the definition of neutrally stable.

As a side note, it was about 35 Deg. F for my first flight of the morning. The oil cooler exhaust really does provide a lot of warm air for cabin heat.

Wes

[sonex1566]

Hi Wes,
I'm glad that its all coming together and most importantly enjoyable. What sort of cruise speed does your 3000rpm give you on your prop? My Aerovee has about 75 hrs on it now and touch wood my teething issues are behind me. I'm using the Sensenich 54 x 44 prop which gives me about 115 kts true at 3200 rpm ish. But I've never flown in temperatures as low as 55....ever! My only real issue really is that my wife and I are a bit 'solid', which means my climb rate is a bit crap...I always want more!

[N190YX]

It is my understanding from several sources over the years, the latest being the documentation accompanying a SureFly electronic magneto I recently installed on my certified airplane, that advancing the ignition timing will tend to increase cylinder temperatures. I believe retarding the timing past top dead center will also increase temperatures, and that may be what you were thinking of. The SureFly documentation cautions to closely monitor cylinder temperatures as the SureFly in my installation advances the ignition timing at lower than full throttle power settings. If you adjust your ignition timing more advanced than recommended settings, suggest you closely monitor and control* cylinder temperatures. *climb at higher indicated airspeed, reduce power in level flight, make the mixture more rich if leaned are three ways to lower cylinder temperatures.

[WesRagle]

Hi Richard,

What sort of cruise speed does your 3000rpm give you on your prop?

I haven't done the speed runs yet. I hate to guess but ... I don't think my speeds will be that much different from yours. 125 mph at 3000 RPM, 135 @ 3200, 145 @ 3400, and 155 @ 3600. I expected a little more but that's my initial impression.

Edit: Well, I did some GPS runs today and I didn't even get close to the above numbers. Initial testing shows:

112 at 3000, 123 at 3200, 130 at 3400. Seems my airspeed indicator is reading high. I was at 5000 DA and my indicated airspeed matched almost exactly with my TAS calculations as made by this web site: http://www.csgnetwork.com/tasgpscalc.html. WOT produced 3600 RPM and an indicated airspeed of 140 mph. Oh well, I built a draggy airplane. Still having a lot of fun.


I did intend to get you an answer this morning but when I got to the hangar I found I had left my steno pad in Olney. Left my funnel too. What better excuse for another cross country :-)

For today's trip I flew like this:

1) Full throttle for takeoff and initial climb
2) At about 300 ft AGL throttled to 3200 RPM which gives about 1400 EGT and 750 fpm climb.
3) At 1500 ft AGL nose over for cooling and speed. Pitch for 350 CHT. Approximately 500 ft per min climb.
4) At cruise altitude nose over and reduce power to 3000 to 3200 RPM.

On the outbound leg I leveled off at 2500 MSL, stabilized at 3000 RPM, and checked FF. FF was 5.2 GPH. I then climbed to 4500 MSL and checked again. As expected (with the Zenith Carb) the fuel flow hadn't changed but EGTs were lower. I just had to make sure that would be the case.

Still a lot to learn about the airplane but having fun learning. It's uncanny, but a check of the flight log on the GPS showed 134 miles in 67 minutes. Looks like 2 miles a minute portal to portal is going to be the rule of thumb.

I do wish I didn't have to fuel through a hole in the windshield. I'm limited to 100 mile radius unless I want to risk a shattered wind shield.

BTW, the easiest way to pick up climb (besides diet and exercise) is cold air induction. Good for at least 100 fpm at gross, probably more.


Hi N190YX,

It is my understanding from several sources over the years, the latest being the documentation accompanying a SureFly electronic magneto I recently installed on my certified airplane, that advancing the ignition timing will tend to increase cylinder temperatures.

My understanding as well. I know from experience that retarding the timing will increase EGT. Whether it is smart or not, I want to keep my EGTs down to 1400. To do that I have to give up a little on CHT. The difference between 1 or 2 degrees advanced and 1 or 2 degrees retarded is very pronounced as far as EGT is concerned.

Listening to the guys that have lots of trouble free flight hours on VWs, the key is keeping them cool. So, I'll strive to keep CHTs down to 350 and EGTs down to 1400 max and 1200 to 1300 in cruise. Funny how fast the emphasis changes from speed to reliability once you strap the plane on for the first time :-)

Wes

[WesRagle]

Hi Guys,

Got in another 1 hour on the Onex this morning. MWL-ETN-MWL. Departed at sunrise this morning. OAT ~ 50, Humidity ~95%. I think I finally made some ice. I noticed the engine was running a little rough. It was rough enough that I didn't turn directly for my destination but continued the climb as I orbited the airport. I applied carb heat and the engine dropped 200 RPM, smoothed out, and I was on my way. This is the first time I have run at power with carb heat for an extended period. It didn't seem to effect the engine temps much. FF did increase above normal once throttle was advanced to recover the 200 RPM drop.

My front CHTs are at the lower limit of my comfort. During cruise they were running just above 250 Deg. My hottest cylinder was running at 305. I think it's time to try to balance them some.

It was crazy at MWL this morning. Constant chatter. Some folks flying right pattern with left published. Constant instrument students flying missed approaches. Another student doing touch and goes down wind on 31. By the time I got to back to the airport the student flying downwind pattern was on the ramp. I crossed mid-field and entered the pattern for 13. Everything seemed normal until I was rolling out. It was then I saw this guy on short final https://flightaware.com/live/flight/N551XJ/history/20201107/1332Z/KHOU/KMWL. If I would have missed the first turn off I would have had no choice but to pull off the runway into the grass. I swear he never said a word. I need to start figuring out a way install ADSB.

Wes

[WesRagle]

HI Guys,

I finally made an attempt to check my airspeed indicator and get some idea of speeds at various RPMs. Assuming I did everything right, the airplane isn't as fast as I had hoped.

Testing was done at a pressure altitude of 4000 ft and an OAT of 62 deg F (5116 DA). The Onex is very hard to fly perfectly straight and level but I did my best. Initial results are.

3000 RPM 112 MPH.
3200 RPM 123 MPH.
3400 RPM 130 MPH.

Assuming I did everything right, my airspeed indicator is reading over 10 MPH high. Based on the calculations made by this site http://www.csgnetwork.com/tasgpscalc.html my indicated airspeed matched almost perfectly with true airspeed at 5100 DA.

WOT produced an indication of 140 mph which I assume is fairly close based on the above observation.

Oh well, I guess all the cooling drag I added, the longer main gear, the long wing tips, the left wing with a big wedge on it, ... , all add up.

I'm not going to worry about it. Fast enough for me. Having a blast flying it. ADS-B on roder.

Wes