Dual mikuni's 28's running rich

[Bob Wood]

Update:
After adjusting  float level, bracing carbs, my jetting has changed still not up to 1200 but as high as I can get it. Here are my jets and temps 
# 2. 170 Jet less than 900
        155 jet. 1050
         145 jet 900-950
          150 jet. 1050-1100.          Static RPM  3060

#4.  170. Less than 900
        155 jet 950
         140 jet 1000-1050
          130 jet 1050-1100.         STATIC RPM 3060


So finally have the 2 sides even on temps. I checked my tiny tac with a digital for max rpm and got 3060. Tiny tac was bouncing around at WOT.

Next I set up the thrust scale and at the max jets and 3060 RPM above I got 150 lbs thrust. 
Am running a TN 54x22. I  spoke to TN PROPS and can get a 54-20 repitch for 75.00 and 1 week wait.


If anybody has a Mosler 6 bolt 3 1/4". Prop with the 2" counterbore. I may be interested......

I am thinking more rpm may give higher EGT and also my extra thrust 

Am I on the right track.?
Bob

[Steve]

Update:
After adjusting  float level, bracing carbs, my jetting has changed still not up to 1200 but as high as I can get it. Here are my jets and temps
# 2. 170 Jet less than 900
        155 jet. 1050
         145 jet 900-950
          150 jet. 1050-1100.          Static RPM  3060

#4.  170. Less than 900
        155 jet 950
         140 jet 1000-1050
          130 jet 1050-1100.         STATIC RPM 3060


So finally have the 2 sides even on temps. I checked my tiny tac with a digital for max rpm and got 3060. Tiny tac was bouncing around at WOT.

Next I set up the thrust scale and at the max jets and 3060 RPM above I got 150 lbs thrust.
Am running a TN 54x22. I  spoke to TN PROPS and can get a 54-20 repitch for 75.00 and 1 week wait.


If anybody has a Mosler 6 bolt 3 1/4". Prop with the 2" counterbore. I may be interested......

I am thinking more rpm may give higher EGT and also my extra thrust

Am I on the right track.?
Bob

You are on the the right track and the prop change expectations are correct on thrust and EGT...

From collected reporting on props:

The de-pitch change you are considering on the Tennessee 54x22 will yield an additional static 150 rpm  and 100 degrees more EGT...
Leonard shortened the 54x22 prop on his Dual Mikuni version of the Betterhalf prototype to bring the engine (alive) - his cut prop was 52x22...  The engine 69x92 well run-in...
Frank Johnson has experimented with a 52x22 prop that users report out performs the 54x22's they were running... Frank has modified his blade layout on the 52 and that is important to note...
The advantage of leaving the pitch at 22 is once you are in cruise the rpm required will be less... Generally the draggy airplane flys best with the longest prop you can turn up to rated rpm...

My 69x94 engines turned 3100rpm EGT 1300 static when fresh on a Peery 54x24 prop (very thin blade shape) the LE climb at 525 lbs gross was underwhelming... Changed to a Tennessee 54x20 prop the engine turned 3350 rpm EGT 1400 static and ROC went into the 400 ft/min range ...

[Bob Wood]

Ok thanks for the prop reports. Do you think the repitch to 54-20 will get me from 150 to 170 thrust.

Is 150 too low to safely fly the XL? I have not head many reports on thrust measurements and what is really go or no go.  

Thanks Steve 
Bob

[Tom H]

Bob Wood, be careful, max static thrust is not the "final answer" as to how the airplane will climb or fly.  Static thrust tells you the prop's performance at zero airspeed.  It may indicate how quickly the airplane will start accelerating on take-off roll.  But, as soon as you get some airspeed, the prop may or may not be doing as well.

We just tested a new, beautiful Performance Prop on our DE Stubby.  A work of art.  We got the best static thrust numbers yet, with higher rpms (about 3400) just like we wanted.  It accelerated quickly, broke ground sooner, but did not give us much better climb than our main prop (3100 static).  And, in level flight, I did not get to full throttle because the rpms hit red line.  Also, had to run the engine about 3200 to get the same cruise as the old prop would get at 3000.  That was expected, but, increasing rpm on up to 3600 did not yield much gain in speed.  Seems the prop hit its limit.  Probably pitched too low.

So, Frank says to send it back and he will make some pitch tweaks to it, which, I hope, will put it somewhere between our main prop and the tested PP prop, yielding better climb, but only a slight loss of cruise speed.

I think, for best climb, the prop needs to be just slightly stalled at zero airspeed (which give high rpms, but not high thrust numbers), then un-stall as airspeed starts to pick up, maybe just before lift-off/climb speed, at the target rpm. 

Maybe the best test would be to tow the engine/prop on a test stand at 50 mph and measure the thrust in that condition.  Somebody should work on that.  Should make a good video.

That's my thinking, anyway.

[Bob Wood]

Tom,
Interesting, I think I am going to do more high speed tests and maybe a take off or 2 on my 5600 foot strip and see how it goes.  Does my 150# seem low at 3060 static? In actual flight when the prop unloads I would expect to gain 100-200 RPM and the thust that goes with it. So I may be ok??


 I would rather order a new prop and have the ability to go back to my 54-22 that cut mine up.  I am running out of WI summer is there is such a thing. 

I have about 11 hrs in run and taxi testing on my motor that has about 50 hours total time.  I feel like it is ready to go up...
Thanks,
Bob

[Sam Buchanan]

Skip further thrust tests, jetting tests, and most of all, the high-speed tests.

Time to fly. 

No more paralysis by analysis.   ;D

[Tom H]

Bob W, Sam said it. 

We built and flew a LEU (Treehugger).  It was a tad heavy.  The engine wood bar dyno test showed 29 HP at 3400 rpm.  We had a 54x20 prop (unknown mfg), and full throttle static was 3150 rpm.  It was probably developing 25-26 HP at this rpm.  Static thrust was around 100 lbs.  My notes say it climbed at 3220 rpm.  I do remember that climb was very poor, though.  But, it flew, and we flew it, but decided it needed more HP and less weight.  Stopped all development work when it met up with a tree.  All OK, airplane in pieces in storage.

You have a nice, long runway.  Almost a cross-country in a LEU (except for Les Homan).  If you have the basic airplane flying skills, and if the airplane has a flying CG at 28 - 30% of wing cord, you should be able to fly it.  If you have decent altitude half-way down the runway, keep flying.  If climb was pathetic, you have half a mile to land. 

On landing, with power at idle, our LEU had to be pointed toward the ground, as compared to any conventional airplanes that I have flown.  It seemed weird, at first.  You want to keep airspeed up until you are close to the ground before flaring.

Pick a calm day.  Fly the thing.  Have fun.  Have someone shoot a video.

[Bob Wood]

ok, sounds good to me, I did a test hop last night flew a portion of the runway . Slight crosswind and the sun was down so I called it a night. Tail popped up jumped right off , seemed smooth and stable.....Good weather next couple of days, will advise how it goes.

Thanks for all your help!!  My worst fear was not flying it before winter.....

Bob

[Bob S.]

Just FYI, I pulled my jets again and I know I SAID one was a 120...well, I just checked and it is MARKED 120 but I drilled it out to match the 180...so they are in essence both 180 jets and the needle is in the middle slot. My EGT's are just under 1400 and CHT on the one head is around 350....

Sounds like you are getting yours narrowed down! AND getting some air under those wings??

[Bob Wood]

Bob S.
Thanks for this info I still have jetting work to do but I did get 3 flights in and have it running well at 1150 or so on both jugs an a 130 and a 150 jet. 

These are a ball to fly, I jumped off and flew at 3/4 throttle the length on my 5600 ft runway at about 50 ft or so and had great control and stability. I did have rigging issues which I am starting a new discussion on. Please jump in .

Thanks to all of you guys for getting me into the air!!
Please jump into my rigging thread
Bob

[Dan_]

Dan,
Thanks for this, I did see this and set up accordingly. I thought maybe the L Eagle guys had a different setting....

How did you measure your engine thrust. I  am thinking a  200# deer scale with a hook and rope tied to a trailer hitch or tree??
Thanks,
Bob

Here is a good web site with tuning tips and manuals...

www.mikunioz.com/tuning_manuals.htm

[Bob Wood]

I wanted to get back to this thread as I am ready to try to lean out my 37hp 1/2 vw.  I have 10 or so issue free flights which I chalk up to no vibration shaking the float needles, making the motor run rich at certain rough power bands. It even happened when landing in a rough field where the floats bounced around and overflowed. So I am running great right now but still low EGT.

I have been running 170 main jets with the needles on the middle notch. My EGTs are around 900 on both sides. I just went to 160 mains for a couple flights and saw no change. I was going to go to 150 next, to see if I can get then up to 1000 or so.

My CR is 8:1 and I am running premium Mogas.

Comments greatly appreciated.

[Dan_]

This may be apples to oranges for example he is running a bigger engine with smaller carbs, but I thought it was interesting. 

[Chuck in Indiana]

I wanted to get back to this thread as I am ready to try to lean out my 37hp 1/2 vw.  I have 10 or so issue free flights which I chalk up to no vibration shaking the float needles, making the motor run rich at certain rough power bands. It even happened when landing in a rough field where the floats bounced around and overflowed. So I am running great right now but still low EGT.

I have been running 170 main jets with the needles on the middle notch. My EGTs are around 900 on both sides. I just went to 160 mains for a couple flights and saw no change. I was going to go to 150 next, to see if I can get then up to 1000 or so.

My CR is 8:1 and I am running premium Mogas.

Comments greatly appreciated.

Ok, where are your egt pickups located? An inch closer or farther away from the exhaust valve will make considerable difference. What do your plugs look like? That is a good indicator of mixture.
Mikuni's are motorcycle carbs, and quite resistant to vibration. I have found that carburation problems are almost always ignition.