JBrannon

My Feedback: (3)

Dick, The TOC pilot is Don Szczur. I was thinking about people using the ZDZ 120 or 160 or a 3w 140 compared to the 150DA. I would think those are viable alternatives to the DA also.
Joe

Diablo-RCU

My Feedback: (1)

Say Kris:
There is something wrong with the tank setup of the fellow with the ZDZ. I once had a 62 minute flight with a 32 oz tank and a ZDZ-80 on a 24 lb Cap. Routinely flew 18 minutes of sequences while practicing....maybe 1/3rd tank left. The ZDZ gets better mileage than my 3W-100.

IanB

My Feedback: (1)

Again thanks for the good info Kris.............nice to read sensible posts!!


Just musing here..........Imagine how energy efficient that makes the bme

18mins 32oz gas 6900 mej 28x10............bme 110 pefa cans.............Kris
10mins 32oz gas 6500 mej 28x10............da100 regular muffs............IanB

Admittedly the DA has a lot less running than the BME but you are getting all that extra power and using almost HALF the gas.............hhmmmmm.

conservation of energy??
there IS only so much energy available in the gas!
Are you running very very cool head temps??



Dick any thoughts??

Kris^

My Feedback: (1)

All I know is what I see, Diablo. He has a 32 ounce tank. . Timer on the TX for 8 minutes and when he lands he's almost empty. I can see the fuel level, less than 4-5 ounces remaining in the tank, and he deadsticked his first flight with the engine after only 7 minutes of air time., with a full tank for startup and taxi to takeoff. I would not have believed it if I had not actually seen it. It DOES make good power though, turning a Menz-s 26-10 at about 6100, about normal for a ZDZ80 on stock muffler setup. Maybe he's venting some out the overflow and not knowing it, but there is no residue on the plane to indicate a problem.

We are having our club meeting on Tuesday, I'll mention it to him and see if he can find a problem with the tank setup.

BTW, I've run my 110 for over an hour on 32 ounces of gas, at a steady 3500-4000 rpm using a Menz-s 27-10, when I was doing the first break-in run on my back deck. When I landed today after 20 minutes of HARD flying in heavy winds (25mph+), I had an easy 1/3 tank left. Since he's hauling around a heavy 84" bipe he's on the gas a lot more than he knows, but I just don't realistically see it either. Sily motor takes forever to restart too, no matter if its hot, cold, or whatever. Seems strange since the ZDZ80 seems to have a good reputatiion for easy starting once it's warmed up.

BTW, I had the 28-12 Mejzlik on the plane today (Getting back to 110's), turning right at 7000 Hot and making all sorts of silly noise in the air. Had a crowd on hand so I had to do a little showing off. Ever try to TR in 20-25 mph winds? I'll just say the 3D stuff stayed at least 15-20 feet off the deck and that one low slow roll was a real nerve wracker because the tail was anywhere but behind the nose. Great plane.

rmh

Yeh - I always assumed that power was a direct function of efficient fuel use
If the fuel is simply thrown out the exhaust - then that is not efficient .
And one example is not a very good sampling --
In the medioum sized planes, the 80 ZDZ single is probably the most popular IMAC engine in the region- with the DA100 next.
I never heard a mention of fuel swilling - on either engine for that matter . Kind of tells you something --
Just a guess - I never made a direct count - just eyeball count from doing CD duty - entering contest etc..
BTW- We just ran a test today in 25 degree weather -- on a new sample of a Bambula design 26x8.
We first ran up the engine on the 26x10 Mejzlic then switched props then Brian flew it - (I was already frozen)
The prop revs - pull and speed all were about the same as the 26x10 Mejzlic!
Hoverpower and vertical recovery were maybe a little better and once the vertical recovery started moving- it improved --
All this on the 29 lb +model powered by a 100 -
So when you hear comments that a bigger prop will work better on a big plane ---
Don't bet the farm on it .
Them ol props can fool ya .

Kris^

My Feedback: (1)

Ian, are those numbers for the DA a consistent rpm or flying?

Seems like a LOT of gas going through that DA. . that's like 2.5 ounces/minute, or more than most 150's use.

I am off the gas a lot, though, since the silly motor will pull the plane around at 1/4-1/3 throttle and will take it vertical at about 1/2-5/8 throttle. Don't need full throttle power unless I'm trying to get somewhere vertical in a big hurry.

IanB

My Feedback: (1)

Kris that is pattern flying carrying a lot of speed in wind.....no 3d at all

I know it is a very loose comparison but I was marvelling at you energy efficiency!!

Actually, 2.5oz/min is what the DA instructions say at around 6000 rpm.

It would be interesting to compare timed runs at full throttle for a certain amount of fuel turning the same rpm's

In europe we mostly run intake trumpets and there is an improvement in fuel efficiency because of a reduction in spray back from the carb.

Kris^

My Feedback: (1)

Even sequence flying, doing the Advanced Sequence for this year, I easily get 3 sequences in 15 minutes, and have a good reserve of gas left over, probably 1/3 tank. We need to get a side-by-side on this one to make any accurate determinations.

Paul Cataldo

My Feedback: (10)

Diablo is right,
I get well over 25 minutes of 3D flying with a 32oz tank and ZDZ80. I always land with plenty of fuel too.

rmh

Ian - I have trumpets for the intakes of my ZDZ engines - but so far have not run them - - Just lazy -
from a theoretical standpoint - they make excellent sense -as flow straighteners. Some day soon I will install them!
I don't get any spray back from my carbs - I watch them on the bench -when doing test setups and in my models - no wetness from spray - I have goofed and done an over choke and dribbled gas from the carb tho -
We had a friend run a 3W 50 rear intake in a model which ran extremely well but it would spray back at low throttle settings .
This is not unusual on reed setups - and no big deal either - but it was obvious as the other identical models with the rear rotary engines did not spray back.
The DA carbs are in a location which can cause siphoning -but typically not -- all of the ones here, run like a champ.
Brian runs 3 Unlimited practice sequences on the 100NG powered WH 330 but he is always throttled back except for upline snaps -
Frankly, I have never had a concern about "mileage" -
We setup two almost identical models , H9 1/3 scale -one with a DA100 and the other with a ZDZ80 and a tuned can
power is very similar - milage also very similar . weight almost the same
The owner commented that the DA may a bit stronger - but other than that - and the ZDZ being quieter - no comments - both start instantly etc.. same props etc..
He is a good flyer , also flys full scale twin, maintains it etc- so he is a good judge of what is going on technically.

Kris^

My Feedback: (1)

What Dick fails to point out, though, is that "spray back" from the carburetor is strictly a reversion/timing issue inherent to certain engines designs. It's mostly associated with overly aggressive intake timing on the cylinder ports because you will get a reversion pressure pulse at low rpm. As well, the incoming air, as it passes through the carburetor, has mass, and energy, and when the intake valve shuts, be it a reed valve or rotary valve, all that air has to go somewhere. You wind up with a positive pressure area under the carburetor for a short time, which reverts back past the throttle blade, causing the mentioned "spitting back" of fuel or mixture. Below a certain rpm this WILL happen with any 2-stroke engine, though it may not be plainly visible, and leaning out the bottom end mixture makes it less apparent. Then, as the rpm increases past the point where the airs bouncing off the closed intake valve does not have enough time to actually you will get a steadier flow into the engine and more efficient operation.

Now, imagine a disk valve or rotary valve that is out of time, a weak or damaged reed valve, or an overly rich mixture that makes the engine soggy on the bottom end. . . it can happen to them all. An inlet trumpet will tend to elongate the column of air trying to enter the engine while the intake valve is closed, helping to keep the airs momentum focused into, rather than reverting from the engine, but the process of reversion is still trying to take place every time that intake valve closes.

IanB

My Feedback: (1)

Hey Dick

I wasnt really concerned about the mileage as such.

Just really an interesting way of looking at an engines performance and efficiency......the efficiency that Kris is getting is really impressive and I was wondering how he was getting all that performance and burning very little fuel doing it.

I would be neat to do some testing side by side for sure

Just thinking out loud here I would say that increasing performance is all about cramming as much fuel and air as you can into the cylinder and igniting it. More performance.....more gas.


Im here to learn ..........

Kris^

My Feedback: (1)

Maybe its those teensy cooling fins that can't possibly cool the engine, so it turns into a thermal dynamo, reheating and processing the mixture 3-4 times instead of only once, sort of like a Stirling engine. . . .Hmmm. . .BME. .a Stirling example of model engine efficiency and design? (nyuck nyuck nyuck)

How bout. . powerful motor + lightweight and low-drag plane = lower throttle settings and better efficiency?

IanB

My Feedback: (1)

....seriously now

rmh

seriously?
awe - why - I have not yet heard from the Cheshire Cat---

Kris^

My Feedback: (1)

Ian, I've been going over this in my head a bit. When I was down at BME's shop in November, I let Todd Blose fly my plane (really I begged and pleaded and he deigned to grace it with his presence. ) One thing both Keith and I noticed was that when I flew the plane I was not into the throttle as much as Todd was. Perhaps it was that I had more experience with the setup or that Todd prefers more speed when he flies but there was a distinct difference in throttle usage. This could easily be the difference in a half ounce or more of fuel consumption per minute, as these engines don't really start sucking the fuel till over 1/2 throttle and 4000+ rpm. (fuel demand could be a square of rpm increase . .double the rpm, quadruple the fuel demand???)

So, there you are, putzing along at 1/3 throttle and 3500 rpm cruise with more than enough speed for simple maneuvers like rolls and points and rollers, 45's take about 2/3 throttle and 5800-6000, as do most verticals, and you only need to get into the real hose-pipe fuel consumption area when you go to full throttle for those snapping uplines. Average out a 20% higher throttle position for a 10 minute flight and I'm sure you see my point. Add in a bit more available power, swinging a slightly larger prop, and you can throttle back even more, sort of like cruising along at 2000 rpm with a 350 uncer the hood, rather than 2600 with an anemic V-6. . same speed, much different throttle opening percentage. (Yeah, but 350's suck gas bad even at idle. . .)

Guess we should get an olde long-distance recip pilot into this one to talk about throttle settings vs cruise speed.

IanB

My Feedback: (1)

We need to take the throttle settings out of it....................and do some testing.
Maybe we could do this one day.

All the energy available to the engine is in our teensy weensy 32oz tank.........

That energy is either turned into work done at the prop.....Or heat......Or noise....Or vibration.
Which is why I was wondering what your head temps were............if your running cooler your wasting less energy.
Right now we cant take our differing throttle position out of it other than say we are both flying pattern........(not right I know but hey its all we have!!!)

At present you are getting 500 or so rpm more and burning almost half the fuel doing it.

Makes me curious enough to want to do some testing!! Or at least do some timed full throttle runs.

Kris^

My Feedback: (1)

Well. . having the potential for more power from an engine is one thing. . USING that potential on a constant basis is quite another. I can idle my 110 for over an hour on a 32 ounce tank, but at FULL throttle I bet it is just one big gas sucker, and I'd have a short flight duration. The DA100 has a larger reed bank, approximately the same sized carburetor, and less aggressive porting of a different design from the BME110 as well as a shorter exhaust event, not to mention 10% less cylinder area. To turn the same prop at the same rpm you would have to open the throttle on the DA. . it's just a matter of fact statement, because of the different power output of the two engines. I don't know your flying style, or how heavy or draggy your plane is, but if you are flying a less efficient airframe design, and having to open the throttle to compensate, it stands as logical that your fuel consumption, even with the same sized carburetor, would dramatically increase.

rmh

Ian -- do you remember how much torque increase it takes to increase rpm 500 more - say from 6500 to 7000?
on for example a 27x10 Mejzlic?
Or in Hp for that matter .
more than a 30% increase in HP?
More than 20% ?
More than 10%.?

Then - what is the ratio of fuel consumed to increase power that much?
on this one lets stick with the same engine - your choice.
So far I am a bit mystified by the increased power levels and the decreased fuel consumption being discussed
But I am willing to learn how it works --

Kris^

My Feedback: (1)

Part throttle is the key, Dick, less throttle= less fuel consumed and longer duration. If you can coast around at a lower throttle setting for the same performance, you are using less fuel, and getting better efficiency during the flight. The REAL test of fuel consumption is not part-throttle flying, because that is mostly controlled by the pilots finesse and flying style. Full throttle and max rpm is the only way to accurately gauge comparative fuel consumption. The rest of the time it's up to how wide open that throttle blade is.

rmh

OK Kris - you ferreted out the obvious -
but which question did it relate to?

IanB

My Feedback: (1)

Take the throttle out of it.......as I have been saying for the last three posts!!

Slap two engines on a test stand with the same prop and run them full throttle til the tank is dry.

Your bme runs almost TWICE as long and produces 500rpm more top end as my DA on THE SAME AVAILABLE ENERGY.That is what I thought interesting?

Look at drag racing............more performance...........more gas..........Dick your a race guy........am I way off the mark here?

Kris you mention you flew 3 advanced patterns getting around 18mins with a good amount left in the tank and you turn 6900 on a mej28x10. We were comparing flight info because we have no test info..............FYI It says in the instructions DA100 2.5oz /min 6000 rpm

rmh

If there is a reason who the power is high and the fuel consumption is still very low - -I want to hear it .
I can accept very high power OR very low fuel consumption - It is just that short of fuel injected turbo four strokers - I just have not seen it --and then the fuel consumption still is not all that low.
When I ran a GMC blower on a 303 cu in Olds -I got 22 mpg- at cruise of about 60 mph - normal driving .
when I opened it up - I got four (4 ) mpg.
The power was fierce but I got the power by using lots of fuel.
so far I have not seen anyway around it -- short of Cold Fusion.
(I would be glad to sell you some stock in a new Cold Fusion project )-----

Kris^

My Feedback: (1)

The way thse cooling fins work, Dick, I may just have a cold fusion reactor here.

Tell you what Ian. . I'll do a run with a full tank, on the ground, and just let 'er rip for as long as I can stand it. Then I'll suck what's left in the tank into a measuring bottle and get a measurement for you. I figure 5 minutes straight, on the ground will prove several things. . First we'll be able to get a semi-decent fuel consumption reading. Second we'll be able to determine that I really AM hear-impaired, and third we'll get to see if the BME overheats under such rigorous test conditions, inside a closed cowl and only the prop for ventilation. Oh yeah, forgot the 4th thing, whether my tether system works

rmh

Cheeeeee