Until someone puts both on an actual dyno it's all hypothetical anyway. There's only a few places that have true dynomometers for small engines and most of them don't share the developed info with the general public. I do know that some 80cc singles are mighty close to some 100cc twins in the area of torque. Specifics withheld out of neccessity.

Im one of those liter bike twin riders...

As for these two engines, da100 feels better to me hands down over the 85 in flight, granted the 85 needs a pipe to have similar power to the 100, but for smoothness, and less peaky throttle, 100 all the way.

The analogy to a bike is what is misleading you.

On a motorcycle when you open the throttle you feel the torque at whatever rpm you are at. But with a plane the rpm immediately goes up to maximum.

It would be like driving a motorcycle on soft dirt, any time you open the throttle the wheel spins and the engine goes to max rpm. There is absolutely no way to feel or know the torque output at anything other than max rpm.

Did any of you out there ever drive an old Buick with a Dynaflow transmission? On that one if you floored it the engine would go to max rpm and stay there.

I guess you had to be there.

TF

I just bought an 85 and I hope it is a great motor. Its going on one of those 33% Lanier EDGE540's. The plane was $350.00. Can't beat that. From what I've been reading the 85 doesn't shake that bad. I hope its ok?

swap exhaust systems around and you can make either one the "most powerful"
Dynos?
unless you have a specific power band in mind (RPM) -these mean diddly squat.
Any guy who understands two stroke tuning will tell you that.
The subject engines should do the "same jobs"-that is pull a plane of the same weight /drag etc., about the same - If I had to tune one for all out power I would take the 85 - Ithink I could "push"it harder . If I wanted the no brainer of the two - the 100

I have the exact setup ( Lanier edge 33% and new DA85)and fired it up today and the 85 is a shaker, I used my prop 26x10 off a DA100 that is smooth as silk. The prop is balanced fine.
BEEF UP THE FIREWALL!!!! throttle servo back at wing tube, shakes like a rattle at the front.
Power house no doubt!
I will fly when I get the servo back some.

Yes its kind of obvious when you think about the mechanics of it, bigger singles have a bigger piston head that weighs more and gets thumped harder by the combustion cycle. So in the twin they are in opposition firing together that imbalance almost cancels itself out and makes it smooth and vibration tends to be of a high frequency low level nature. No matter how smart you are with the single desigbn you cannot get around this fact, unless, you build it with a counterbalance and if you do that you defeat the object of the design (ie weight saving!).

One of the reasons (as i understand it) a single no bigger than 50cc was made for a while was that vibration would be too much of an issue. I mean if you wanted to mabufacturer vibration somehow can you think of a better way than hurling a lump of metal from side to side... I know something about this from personal experience over the years with YS engines that have gone from .90 in size up to now 1.80. While they have got more and more powerfully, incredibly so, the vibration from them has gone from considerable to phenominal, made worse of course by the fact they are four strokes. A YS over 1.40 now can quickly find weaknesses in a wooden airframe, im expecting the DA84 will do the same!

Not exactly - a good 80 single can be very smooth - they are all counterbalanced , tho there is a midrange node due to them being a single - The YS 4 strokes shake mainly due to the "every other " power stroke has to do with lower number of prop power pulses per revolution.
My broken in well tuned ZDZ80's are extremely smooth - I expect the DA 85 will be very much the same .
Th spark ignition can be tailored to reduce much low speed vibration. seen quite an improvement in this in modern ignitions.
The other "vibration" is simply torque reaction- single - twin - all have it . I put spark ignition on a 1.4 ST and the low speed vibes smoothed waaay down
why no one offers a good spark setup for "glow engines , for competition use, is a mystery to me - For some users tho- they would likely just f it up
The so called injection engines are a case in point.

Dick Y.S. are just in the process of introducing a spark ignition system on their 4 stroke methanol munchers and making claims of much improved fuel economy

DUDES!!!......


You guys are looking at ONE BRAND name and comparing the two ( DA-100 -DA-85)

If you want facts on which produce more power , all you have to do is just look at some other brands with the same cc and compare them.

Example#1 the new 3W-85cc vs the 3W-85cc twin. The twin is smooth as silk , but the single will pull that motor backwards all day long.

Example #2 Saito 180 single VS Saito 182 twin.....the single will out pull that 182 twin all day long as well......IN FACT , the saito 150 single puts out the same HP ratings as the saito 182 twin!

Another exaple , back to 3W......what about the 3W-48cc VS just a 3W-50cc single? The single will YARD that little 48cc twin , but that little 48 runs so smooth , you can barely tell it's running if you couldn't hear it.............it runs that smooth!!


As far as the DA-85 is concerned , and if you compare it to the 100 twin....theoretically the 85cc should be about the same in the torque and HP department maybe a little more than the 100. I KNOW the 100cc run a little smoother , and dang it , if i could own both of these motor's i wouldn't b!tch at all.


Honestly......i think it's all up to the end user here. I think they are both great motor's , you just need to decided for yourself. You can't go wrong with either one i believe.

I too, have a LAnier 94" Yak and DA-85.

Got it used from a friend that had to sell it quickly. After I set it up on my radio, we started the motor.....WOW!!!!!

He had never changed the carb settings in the few flights that he had. It rattled and shook SOOOOO bad that the three buddies that were holding and helping looked like deer in the headlights scared.

They screamed "shut it of!!!!".

It was so rich on the low end it rattled like a Herman Munster baby rattle.

I have been steadily leaning it out trying to get rid of the burble.....so far every landing is a deadstick after final turn and throttle down on final glide. Runs reliably at idle after start on the ground but it is getting closer.

It makes insane power , pulling this 19lb 12oz plane vertical well before the carb is half way open. It belongs in a much heavier aircraft, for sure. Menz 26 x 10.

DUDE!! Thats a good one!