Smokey

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Does anybody know the top rpms that I am gonna be able to get with this combo? I am in the process of breaking in the engine and is not sure on what rpm to look for. I have 96oz in it already.
While I'm at it, does anybody know the rpms for a Bambula 26x10 after break in?

Thanks
Smokey

Big_Bird

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Smokey

I have run 2 gallons through my ZDZ 80 single now and the best I can get with a Bambula 26x10 is 5500. It turns a Menz Standard 26x10 at 5820. During breakin on a test stand I have only had the engine at full throttle very briefly at these values near the end of the 2 gallons. A little disapointing.

I'm running the Bisson Pitts style muffler with tips still intact. Timing is correct from every thing I read. The carb is a Walbro. The engine starts good and sounds great. Speed transition is excellent.

First gallon was 40:1 Penzoil 2 cycle air cooled and 93 octane. Second gallon was 40:1 Klotz KL-300 synthetic and 93 octane. Compression is excellent. Tach has been calibrated.

By the way, I checked a friends well broken in 80 at the field the other day and it was turning 6050 with a Menz Ultra 26x10. Not sure what muffler.

Ken

Smokey

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I was able to get 5900 with a Bambula 26x8 prop at about a little over 1/2 gallon. I am also using a Bisson pitts muffler. I forgot to mention that i have the air intake trumpet from RCS.

Smokey

Big_Bird

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What is the air intake trumpet supposed to do for it?

It would seem that we are in a similar ratio on speed with our Bambula props. I would expect a 26x8 to turn a little faster than a 26x10.

Ken

Smokey

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Big Bird

The trumphet is basically a ram air intake. It directs the air into the carb.

Smokey

rmh

The muffler you have is a quieter , In Cowl muffler - It does extract some power penalty -
You can clip the swedged ends to gain more power --AND noise -.
Having run and checked lots of these engines - we are convinced that they are are happiest with low exhaust restriction -or a quiet can or a tuned system.
I have been called a bald faced liar -for my readings published on these engines - so be it - but honestly the rpms will vary quite a lot -depending on exhaust systems -
A JMB can - the larger size - is consistantly above 6000 rpm on Bambula 26x10
on all 80 singles in our area .
adding any tuned can - these numbers improve adding a tuned pipe - they go up more .
On the Bambula 26x10 - about 6400 is the best we see .
On MenzS up to 6600
On the mejzlic 26x10 -I have tested tuned large pipe setups which turn over 7000
My point is that the prop load , NOT the advertised size and the type of prop or muffler plays a big role in how these or other two strokes perform -- especially engines ported for tuned systems .
The air trumpet is an unknown for performance gain.
It can , however make the engine run better if there is an air flow problem -at different attitudes.
I have seen that .

.

Big_Bird

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Dick

Thanks for the info. At this point I don't intend to cut the tips off, if at all, until I fly the plane since I'm not looking for all out performance and would trade some RPM for a little better sound. The Bambula sure seems quieter than the MenzS. The Super Decathlon that this engine is going in has a shorter nose than the typical 3D plane and doesn't lend itself to the installation of a can.

A few days ago I started a thread asking how one baffles (for better cooling) a ZDZ80 in an Extra or Decathlon but got not one response. Apparently it doesn't need baffling or no one has ever done it or ........ Any comments?

Ken

rmh

I never have hd to use bffles --just make sure there is a decent path in for air and a low pressure area for the air to "siphon" out the cowl--

Smokey

My Feedback: (16)

Dick

Have you tried the 80 with the BCM pitts muffler? If so, what did you get for rpms with Bambula 26x8 and 26x10. Also, what would you recommend for a carbon fiber prop after break in. I am mainly interested in 3D stuff.

Thanks
Smokey

rmh

Not the BCM- but have run the earlier Pitts (JA?) which was very open and very loud and ran over 6000 on the 26x10 -
If you are after 3d stuff- use smaller prop - a 26x10 Mejzlic is not a big load - at least not on my engines - it just buzzes !
As for how well that will help your 2D flying - is your guess- the 26x8 Bambula may be good - I use the 26x10 Bambulas and they work well -but I don't spend much time doing hover stuff with that - it does recover veryrapidly tho on the 23 lb plane .
I have always used a tuned can on the 80;s for myself -26x10 MenzS runs 6600 best setups.
longer setups run from 6300 - to that .
Tuned Long pipes - more than that -