altavillan

My Feedback: (1)

It was a discovery from an early fitting of the cans in the fuse. For a while I was moving the canns around to adjust balance. Somewhere around that length the engine is real peaky at midrange, but much more power. It was near impossibe to hold hover without a throtle curve and irritating. So I started moving the mufflers back. It got rid of midrange peakyness but also got rid of a bunch of power, so I worked forward and found a spot where the peakyness is just off idle for quick acceleration, excelent fuel draw, (30% gain), no burbles, smooth transition, but with a tendency to melt couplers at WOT. So I put a servo on the choke to control venturi size and flood the engine with fuel at WOT to cool the exhaust gasses. Working good so far.

tonyc

My Feedback: (4)

I think you are saying that the servo closes the choke some amount at WOT. Would this be 50% or something less? I am a new BME owner and I want to have success.
Tony

RTK

My Feedback: (1)

Tony-- If you can''t wait until BME delivers their carb block (they still will tune differently than others) I can let you know how to tune your engine to run reliably if you let me know the carb and block you have. Send me a PM, I''ve run BME''s since the first 110''s came out. I''ve figured out the idiosyncrasies.

I will let Guy comment on his set-up

tonyc

My Feedback: (4)

Thanks RTK, sent you a PM.

Tony

altavillan

My Feedback: (1)

5 to 10% closed on the WGA carb. The detent ball is still in the slot. Not enough to 4 cycle but enough to shut down some top end rpm.

tonyc

My Feedback: (4)

Do you incorporate a mixing with your throttle servo to close the choke servo 5-10% at full throttle? My second question is how did you come up with the ratio of 5-10%, is it something you set on the ground or is it something that only flying will tell you?

altavillan

My Feedback: (1)

I put the servo on the left slider of a 12z. I can adjust in flight easily. That slider has a ratchet similar to throttle. Three clicks will guaranty a drained fuel tank at 12 minutes. Two clicks is noticeable in flight and one click probably would do the job. I usualy set it at 2 clicks. It would take about 5 clicks to get the choke rod to travel far enough to have the detent ball clear the slot. So in my engines case just a small amount is needed.

altavillan

My Feedback: (1)

Here's a pic of a better way to install the stingers. They are turned down to save a bit of weight and provide a lip to remain seated against the silicone reducer A slight flair would accomplish the same thing if a lathe isn't available. Once the stingers with the silicone reducers are pushed into the chair leg bend, run the modified tubing cutter around them to crimp lock them in place.

RTK

My Feedback: (1)

You are making them simpler every time you post. Good work Guy[sm=thumbup.gif]

tonyc

My Feedback: (4)

I did a lot of studdying of Walbro carbureator drawings and I can't find it.

"The detent ball is still in the slot."??????

On my BME 115 Walbro carbureator I have a rotating disk but I can not see a ball in a slot. Can you explain this to me.

So far what I think you are saying is 5 clicks on your transmitter gives you a fully closed choke disk and two clicks is what you do at WOT to increase gas flow.

Am I close?

altavillan

My Feedback: (1)

The choke butterfly is held open by a ball bearing, the ball is pressed against the choke arm by a spring. The choke arm has a slot the ball fits into in the open position. The rod holds the rotating disk (choke butterfly).
The slider on the 12z has about the same number of detents as the throttle ratchet. I'd say closer to 50. So 2 clicks is about 10%.

Part18 and 36. http://wem.walbro.com/walbro/product...um=WB%2D25%2D1

rmh

You got the combos figgered out - -
Where 90% loose it, is in trying to get the top end rich and the mid range correct.
typical is midrange gets corrected -then the top end goes lean- I did my "fix" using exhaust pressure on my 1.4 Tigres - 1/2 3/4 lb fuel pressure boost occurred when the engin went to full power - a closed loop setup - exhaust to tank pressure (which will not work on a Walbro.)
the friggen Walbros just ain' t designed for all this
BUT - I bet a setup where the demand diaphragn was tied into exhaust pressure -with an adjustable bleed - might work
Never tried it - would likely be tricky to adjust
fortunatly, my engines don't have the problem you have with the oversized carb.

RTK

My Feedback: (1)

That's where a 3 needle carb shines, no lean top end

rmh

I would like to se how it adapts to a full tuned exhaust - that setup requires a real ramp up in volume as power increases.
or you run lean - and it is very hard to tell you are lean-as the pipe tends to lock in the rpmif it is a good match..
On my ZDZ80 which "the xspurt" says is impossible the proper match and needle makes power like crazy.
But then -done right- any two stroker jumps power like crazy on proper pipes I see some of the DA85 guys are finally zeroing in on this.

RTK

My Feedback: (1)

When I retire (crash) the plane it is currently in I will have to send you the carb to play with Dick, that is if you send it back It is very simplistic in its function and will dump loads of fuel if need be.

frieshoo

My Feedback: (20)

This is great!

I should have smuggled some of the aluminum Brazilian beers last year. They were 40oz' ers!!

I'm going to try to build one of these things. I should have lots of 'raw' material after next weekend (Nascar Race in Talladega).

Dennis

altavillan

My Feedback: (1)

D.H. Yes finaly getting a handle on an engines intake and exhaust tuning needs is mucho more fun. Neet to see an engine go from being finicky about too much fuel, to wanting all that can be poured down it's throat.
As far as a three needle goes, there has to be some where to drill and install a brass rod to hang over the throttle disk and use a remote needle assy. with fuel supply tapped into the reservoir.

RTK

My Feedback: (1)

Guy, I also have a two needle carb with the high needle linked to the throttle arm. I never had a chance to run it though.

altavillan

My Feedback: (1)

That one should be tossed into the black hole where everything else BME seams to have gone

RTK

My Feedback: (1)

You want to try it?? and let me know how it works??

altavillan

My Feedback: (1)

Are you kidding? I finaly get mine working and there's no way I'm gona start changing it

davidf

My Feedback: (24)

the bud -light canister muffler worked awsum . had 7 or 8 flights on the 30 % yak with da-85 , the J B weld is holding it gogather nicely no signs of cracking or leaking , it really quieted down the 85 no more poping no more crackling . leaned out the motor a little . the power is nothing but awsun even with a mejzlik 24-10 3 blade . the da 50 previously on this plane just didn't do it . this plane has come to life and it's still flies very light . made the same muffler for my da 50 i used about 40% hardner to about 60% apoxy of J B weld for a softer joint . the bud-light muffler on the gs 70 gave the fx .91 1000 more rpms . is lighter and much more quieter than the stock muffler, the transion is instant with a 15x4 w. i used the same bud bottle and header pipe set up on my fusion .90 with a ax 120 . the power factor is foamy power . going to make one more bud - light muffler set up for my modified gs 40 '' yaktana '' with the new webra .55 i'll post #'s and pictures soon . thanks dave........

worldmodelsmach1

My Feedback: (1)

I'm thinking of doing this on a CRRC 40 GFI, Would I still use the formula above, or would that be to large for this engine? Also how much of a power loss (or gain) would I have If I copied this design directly?

hyflyer9

Has anyone had any luck with making a Rap around style pitts muffler. I am trying to find a way to either modify my stock side mount muffler or make a rap around style.
trying to get the noise levels down is the issue here
the engine is a RCGF 26cc
Thanks a bunch
hyflyer9.

hedgelawn

Muffler questions for 4 stroke warbirds ,
Is it possible to fabricate a muffler that will make a twin cyl. or radial Satio / ASP or Evo. sound closer to a Mokie or Kolm by custom fabricating larger chamber muffler.
This seems logicaly yes to me, but I have no experience in metal fab. so I thought I would ask for some pointers here first, before jumping into an experiment.

Thanks for any usable advice.

Jeff