amjflyer

Ive had a series of problems with a DA-100 in a ZN CAP232 (33%). The plane weighs about 24lbs dry (so its light for the size) and im turning a 27x10 Mejzlik prop but get only 5600-5700rpm out of it and can do 3 vertical rolls before it falls off the top. I expected out of sight performance out of this engine in this light a model. I had a dodgey ignition which has now been replaced and gave me an extra 300rpm (i was only getting 4650rpm out of a 28x10, hence going to a 27x10 carbon). The engine has had about 3-4 gallons through it now so is run in enough to be giving good performance (ive noticed an extra 200-300 rpm since new). This rpm is consistent, ie it doesnt fall off to this as the engine heats up (indicating cooling probs) and just hunt around the rpm (indicating obvious exhaust or continuing ignition probs). At the moment this is the only fly in the ointment of an otherwise gorgeous plane and engine combination, not having over ample power on tap is stopping me trying the more adventerous 3d stuff with it.

The only variable left I think is the exhaust. Mine is a custom in cowl cannister style muffler. Can anyone tell me their experience of performance obtained from the DA-100 on different exhausts? If im going to change it id like to make an informed choice which someone has experience of working well rather than shoot in the dark. Any replacement i buy though will have to fit in cowl the design is such that pipes just wont work in the airframe. Thanks

jmiracle

My Feedback: (9)

I have 2 DA-100's.....one is on canister mufflers (KS)....the other is running stock DA mufflers. The DA on can's is spinning a 27x10 Mej. at over 6600rpm and I'm confident I have another couple hundred RPM I can squeeze out of it. The DA on stock muffs is spnning an NX 27x10 at 6500 rpm and can yank a 30lb Yak out of a hover with no problems at all. Your 24lb Cap should be ballistic with the DA in it. Both motors turned 6000-6100 right out of the box on their very first run without ever touching the needles.

IMO, I think the exhaust is the right place to start from what you've described. I would purchase a set of stock mufflers to try. They should fit (mostly) inside the cowl....though you may need to open up the bottom of the cowl some for clearance.

amjflyer

Well if stock mufflers would give me 500 more rpm that would be a great start, id like to get 1k more then i think id be happy. Ill see if i can loan a set from somewhere...

sillyness

My Feedback: (25)

Call DA. I don't know much about cans, but I can't imagine them robbing you of that much RPM... see if DA thinks they can... they built the motor. My experience with them is that if anything seems the slightest out of the normal they want to see the engine... good folks.

Mine turns 6400-6500 RPM in 90 degree weather at sea-level... tached right after a flight (hot). I am using a Bolly Wood 27x10 and stock exhaust. It did get a little more power as is broke in... BUT it was turning 6,200 RPM out of the box. May be a little tuning in there that helped.

FWIW... rumor has it that the Mej 27x10 and 28x10 turn about the same RPM on the ground... different blade designs.

Diablo-RCU

My Feedback: (1)

Remove the muffler, fire up the engine and tach it. Bet you find +1000 rpm. On stock(DA) in-cowl mufflers, expect 6400-6600 rpm out of a Mejzlik 27x10. Your muffler must be unusually restrictive.

amjflyer

Will it run with no mufflers on? Alot of engines dont like an open exhaust port. I know when ive had exhaust failure sin flight on smaller models and the exhaust has opened up the engine has often cut, especially when at low rpm. Especially a two-stroke which gains alot fo its running and power properties from exhaust back pressure.

rmh

The 27x10 prop is often looked at as the "correct" prop for the engine .
It is OK for most use - but it is NOT the best prop for making power -especially on some in cowl mufflers
letting the engine rev up to close to 6900 -will make more power .
On tuned pipes and a 26x10 they really start to steam and make great power.
If you took an hour and test ran the engine in quick tests -- with NO mufflers (And had the carb adjusted right) your mufflers and latest factory mufflers --you would find three different readings
Best power here on is on 26x10 Mejzlic and factory cans --as opposed to other in cowl stuff
Best power --is on pipes of course .
The back pressure in it's self does NOT make more power -- it does greatly improve low end performance and if --the backpressure is timed to "pump" in sync with rpm -- you have a tuned system --
how about that --

bodywerks

My Feedback: (4)

It is definitely your muffler, especially if you say it is "custom". Who makes it? Does it have any baffling in it whatsoever? Baffling will rob power noticeably.
Also, you will not get an extra 1k RPM with that mejzlik 27X10 - maybe 6600 max.
I feel your pain. I have a BME that I have been battling power issues with. I sent it in and a cylinder was replaced and they told me the engine was performing on par with all other proper-running BME's. Come to find out, he did his tests with his mufflers, not mine. My mufflers are the J&A "peacekeeper" mufflers and have tons of baffling in them - the BME stock mufflers have no baffling. I ordered a set and really hope to get some power increase out of them, or it's bye-bye BME - I am only getting 6000 on a mejzlik 27X10 and only 6400 on a Menz 26X10[&o]

amjflyer

Yes quite!

It sux when you spent well over $1000 on an engine and another $4000 on the aiurplane to get the best possible performance in its class and it sux because of a $200 exhaust. However, i will try somehow somewhere to get at least stock mufflers on it to get another 500rpm would almost be good enough.

bodywerks

My Feedback: (4)

What is your elevation? Even though I was only at 6100 RPM on a Mejz 27X10 (before sending it in), my plane would still go vertical darn near out of sight, and would torqueroll no problem, and my plane is 25.5 pounds and I fly at over 6,000 feet ASL.

rmh

I have run various mufflers -in cowl/ canisters and pipes for several manufacturers--on ZDZ/ DA/ Evolution engines
Which setup is best
well there just ain't no best setup for any of em
It is all a trade off of power --noise - size -weight and price.
Now if you were to ask which engine I got the most power from on any system I wanted to try - the game tightens up -but still changes with rpm band and noise qualifications.
My favorite ?
easy -- the big open inexpensive cans on very short headers
not the most power - not the quietest
not the easiest to mount
The reason thay are my favorite is that they have NO tuning issues with any props I use - they are pretty darn quiet and they fit ahead of the wing tube--in almost all cases.
I still have a bin full of other stuf -which all works - just differently.

amjflyer

Yes, I agree, with two strokes its a trade off between power and noise, and of course tuning. Pipes only work (generally) in a given rev band, some of course are made wider than others but wider rev bands mean less peak power. In fact on another thread I made the comment that I had forgotten all about this two stroke tuning type issues as in my smaller 2m models I have all four stroke YS engines which just do not present this problem. I hope one day someone will build a good 'supercharged' aero four stroke engine that will perform in the giant class like the YS do in the 2m class! Id buy it tomorrow no matter what it cost...

rmh

as it stands -- for your setup - ditch the big props - get 26x10 types that is cheapest easiest fix
swap to large volume in cowl mufflers (if you can stand the noise of them) the quieter in cowl stuff will easily cost you 25% and more of power available -not rpm - power.

amjflyer

Yes, unfortunately i loath two stroke motor sounds so id rather have it quiet and a bit down on power. Ill try a 26x10 though. Will also look into canister options Zimmerman etc.

rmh

You can't have your Kate and Edith too---

RTK

My Feedback: (1)

Darn, I like them both

amjflyer

haha how true! But with four strokes you can ))

ICE_MAN

Theres always full length tuned pipes.. There's Kate and Edith, but they are pricey!


$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $

amjflyer

Nope, the Edith in this scenario is the fact the pipe is tuned to rpm/prop size. So you still dont get Kate AND Edith. An engine with 15hp between 6k and 6k5 and only 5hp between 1k and 6k (and no throttling) is no use to me, i need torque across the range. Suppose i prop hang/torque roll at 5k rpm, im not on the pipe, i have no throttling....ouch!

as722

My Feedback: (1)

If your ignition sensor has moved it can make the engine loose a lot of power. Call DA before making any changes.

Albert

rmh

A thoroughly tractable tuned pipe setup is both possible and available --the power bump is NOT drastic -
here is the classic error:
The pipes INCREASE torque -but typically at a higher rpm
Comes the error -- adding a bigger prop.
To get seamless power - add the pipes but use a prop which works well at high rpm
This allows the engine to transition from off pipe to on pipe with minimum struggle ( the struggle is caused by pipe changing temperature and tuning from low to high rpm .
a constant temperature pipe helps greatly in resolving the problem - aluminun is a problem as it changes temp easily
Carbon fibre pipes hold temperature better as will stainless steel pipes .
The DA100 piped with CF pipes done right---and on a 26x10 spins in the low 7000 rpm band easily and is very quiet and best of all NO herky jerky throttle problems .
One of the local guys has that exact setup on his CF YAK 55.
the pipes are new designs by Ed Skorepa (ES Composites) I run them on some of my planes too
The are not cheap but they do work.
It is all a trade off -in this case cost goes up with performance and the size of th exhaust system is also larger.
If you have not seen how this temp thing works -it is hard to appreciate.

RCPilot100

My Feedback: (4)

My flying buddy and I have identical scratch built Edges - same 24 # weight - same DA-100 engines. Outside of mine looking better than his, I run a 27x10 prop, he runs a 26x10. Both engines run flawless, but I will admit to you guys that I like the way his DA performs better than mine. I won't admit it to him, but next time out, I am changing to a 26x10 Mejzlik.

Dan

pizza

My Feedback: (24)

you can have your cake and eat it too! this weekend I went to a fun fly in jackson wyoming 6000' flying my 27lb comp arf yak w da100 on escomposites gas tuned mufflers with mezlic 26x10. 7480rpm - I was excellerating on the way up at just above 1/2 throttle. the big test was a standing verticle 8 from the bottom - I push the stick all the way forward - was afraid my da100 would blow the wings off pulling hard over the top. there were two other da100 airplanes both with standard deflectors - one had 27x10 the other 28x10. at full throttle they were stalling out on verticle climbs. when you go up in elevation I generally lean the engine about a 1/4 but with only 30 flights still on break in I just left it rich - It was pouring out smoke like a ys140. a lean setting would have given another 300rpm or so. everyone commented how quiet - there is no noise comming from pipes. throttle response is smooth and linear - engine is running cool and there is no heat buildup inside fuse.

amjflyer

Nice flying site! and a great view to go with it...

rmh

Dang - Ray's DA100 pulls harder than my ZDZ80 - I wa only getting 7300 on the 26x10- (ferget the 300+ Ray-- NFW))
Rats
well anyway
The work in getting the performance he described was not by chance -
Ed ran a number of test setups and different pipe designs
Our ZDZ50 NG's BOTH ran ---7750 on 22x8 Mejxlic -and there is no midrange flat spotting
Likewise my 26 Evolution runs close to 9000 on the ground on 18x6 and over 10000 in level flight
But remember - you have to make space - prop it right aand use correct header
It is not the same as slapping on an in cowl can -or hooking a muffler.pipe onto a YS140 etc-- we all have been there meeeeeeny times.
PS you can't appreciate how quiet these screemin two strokes are