critch

I have a Doghouse Extreme and don't have the luxury of having a Saito 91 or 100 to put in it but have a few strong 2 cycle engines. I know that many have had success with the previously mentioned engines. I would like to hear from those of you who have tried 2 cycle engines and see how it performed. Just checking!

Spaceman Spiff

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If you want an engine that is responsive, highly reliable, and can kick some serious butt for cheap, try a mouse can pipe on that old two stroke. Takes about a day to set up, but it is pretty easy, and the results are fantastic.


What engines do you have? How heavy is the doghouse?

doghousesmith

Critch,
A 2 stroke .51 to .60 engine will fly the Doghouse eXtreme fine but you won't get the all out 3D performance that the 4 stroke can give you. The larger 4 strokes are able to swing a larger low pitch prop and that is what is needed for the 3d maneuvers. That is also why I recommend a .91 or .100 for stroke engine, especially the Saito because of their light weight, for the Doghouse eXtreme. You have to have that extra power that a 4 stroke provides and you also have to keep the weight down as much as possible for the best performance. With the 4 strokes the Doghouse eXtreme will weigh about 5 3/4lbs to 6 lbs.
Dick Smith, designer of the Doghouse eXtreme

TailTwister

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I don't have one, but a 91FX seems about right to me...

It's about 22 or 23 ounces, and turns a 15 inch prop. I'd go with a TF PP to help it transition. I'd use the stock muffler minus the baffle.

Look at what you have, and pick the one with the best power to weight ratio, and give it a try. If it's not enough power to really fly hard, maybe it can fly just good enough to enjoy until you have a few bucks saved for a more powerful engine.

Spaceman Spiff

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I don't mean any disrespect, but i bought a couple saitos based on claims that they are the best for 3D, but i just don't see the advantages. I just exchanged an Irvine 53 for a saito 72 on my Top cap. I can't tell the diference, except for the Irvine being able to idle below 3000 RPM, not flaming out constantly, and not shaking my plane to peices.

TailTwister

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I've used 2 strokes forever, and recently bought a Saito 72 and YS 91 to try 4 strokes, and I'm not impressed either. The Saito is very light for it's power. I'll give you that, but I've never had as much trouble getting an engine to start. The kick backs are horrible, and they even happen at full power. I was running my 72 at full power trying to get the needle set when it happened. I heard a backfire, and looked up to see my Goldberg spinner racing across my front yard. The prop had sheered all four pins from the spinner and sent it flying. My YS broke a Zinger across my hand (that hurt for a long time) and broke a Sullivan chicken stick. I've never been actually scared to hand start a motor until now, but I'll never stick my hand near that YS again. My Rossi 53 on a 12.25 prop was a real powerhouse. My YS has yet to run since the broken chicken stick. If I bought a Doghouse eXtreme, I'd probably run an OS 91 FX after removing the baffle. A 15x6 PP will pull a 6 pound plane without a problem. If I felt the need for more power, I'd buy an Ultrathrust or Jett muffler.

I'm still not sold on the 4 bangers.

Spaceman Spiff

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I second the OS 91 FX, ive only run mine on the bench (waiting for my UCD to arrive), but i'm impressed so far, swings a 16x6 Zinger. Easy to start, well behaved.... One of the guys i fly with uses a Supertiger 91, works very well for him.

TailTwister

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Any transition issues with a 16 inch prop?

wgeffon

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Sounds too lean...

TailTwister

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I'm sure it was. It happened when I was trying to get the rpm that others had reported, but before I reset my valves. It may never cause trouble again, but to date, both have been a real pain. After that period of time it got real cold here. I have not run any engines since. Thank goodness for Zagi.

I have not given up yet, but 4 strokes have some work to do before I'm convinced that they are for me.

Spaceman Spiff

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Doesn't seem to have any transition problems, but i am running pretty rich for break in, so if there is a lean mid range it won't show up yet.

wingspan99

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I couldn't believe it until I did it but you can start a Saito by flipping the prop backwards against compression. Not using a stick to push the prop into the compression, but just "throwing" one blade into compression. I don't dare flip my Saito .91 through compression, it kicks like a mule. It puts out great power though, and doesn't give me a headache like hovering with a 2-stroke does. The tone is much lower and the prop noise is far less than a 2-stroke.

TailTwister

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I hope mine learns to behave.

Spaceman Spiff

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The back flip is a great way to start the OS 91 fx too. Looked feaky the first time i saw anyone do it, but once i tried it i decided i would never need my electric starter for that engine. Tried it last weekend with the saito 72, works OK but i didn't have the prop set in the right position for it.

TailTwister

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My 2 strokes do it just fine. I've just had problems with my 4 strokes. By the time I had a good understanding, the temperature was headed for the cellar and I figured I'd wait till spring to giver' again.

matlok

I started out with a 2-stroke ASP .61 on mine, and while it pulled the plane around well enough for normal aerobatics, it wouldn't sustain rolls on an upline and wouldn't even think about hovering. I've got a Saito 91 now that'll pull it out from a hover vertically, although it'd be much better w/a 100. So if you go 2-stroke I'd definately go w/something like the OS 91; anthing smaller probably won't give you the performance you want. Just find the lightest engine in that power range.

As far as the "negative" 4-stroke stuff , I'll just add that my Saito 91 has to be the easiest starting glow engine I've ever had. It *may* take 6-8 flips the first start of the day (pulled through compression), and every start after that is usually accomplished on the first flip! Yea, every once and a while it may kick back, but I'm using a chicken stick so whoopty do it kicked. It's never thrown a prop either - if you use the 2nd nut and tighten everything properly, the prop should never come off. Just MHO.

doghousesmith

Thank you Matlok

Dick Smith

Spaceman Spiff

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Saito 91: 1.6 HP, 520 grams

OS 91 FX: 2.8 HP, 550 grams

Sorry, couldn't resist.

WADE

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I think it's useless to look at horsepower figures when you compare a 2-stroke to a 4-stroke. Two different types of engines, those horsepower figures just aren't a fair comparison. The 4-stroke shines in the torque department, which is why it has the ability to swing a larger prop than the same displacement 2-stroke. The ability to swing a larger prop is beneficial for 3D. I like both engine types, both have their advantages and disadvantages. I personally would go with a 4-stroke if I built the Doghouse Extreme. My first choice would be the Saito 100, the power/weight ratio of this engine would be hard to beat. I'm sure any .91 engine would work well though.

WADE

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Critch, I realized I didn't even answer your question after I went back and re-read your post. I think a good running .61 2-stroke would power this plane fine. It's not a Saito 100 but since you don't have that luxury then you use what's available. Spaceman made a good point about the mousse can muffler, good power boost. You didn't mention what engines you have.

doghousesmith

I'm back...Needless to say I have been reading this thread with great interest. I have to agree with Matlok and Wade completely. Having built 21 Doghouses or Doghouse eXtremes I have pretty well come to know how the airplanes perform. My Doghouse has a Super Tigre .51 in it and it flys great, but it will hover and torque roll for just a matter of seconds.
My first Doghouse eXtreme had a Saito .91 in it and that is the combination that Chip Hyde, Jason Shulman and Billly Hemple flew and of course with them flying it it was truly out of sight. There is no way in the world that the airplane would have flown the same way with a 2 stoke in it because they could do all the wild stuff at a reduced throttle setting. Now a good 2 stroke may have been able to come close but never at reduced throttle.
I have a Saito .100 in the one I am flying now and there is a noticable difference in the performance between it and the Saito .91. The main thing is the .100 will swing a 15 x 6 prop with authority and at a lower throttle setting while the .91 will not perform as well with the same prop.
I really believe that the 4 strokes have almost unlimited vertical pulling power whereas the 2 strokes will normally quit pulling in vertical maneuvers and they have to keep climbing at a much higher throttle setting.
I have to confess that even though I designed the airplane, I have very limited experience in seeing what a large 2 stroke will do in the airplane. I have only fly another persons eXtreme that only had a O.S. .91 2 stroke in it and it flew fine but it definately was no 3D performer.
Almost all of the Doghouse eXtremes I have seen fly have had .91 or .100's in them so I really cannot make a valid comparison. IF anyone out there can give me fly results with a .91 2 stroke in the airplane I am very interested in hearing what they have to say as I really can't answer anyone honestly about using the .91 2 strokes because I have never seen one with that combination. I do know though that the Saito .91 or .100 is a perfect combination for the airplane.
I am now leaping off my soap box!!!

Dick Smith

doghousesmith

Just read my last reply and should have proof read it first. Besides the typos I stated one thing wrong. The friend of mines eXtreme that I flew had an O.S. .61 in it.... not a .91 O.S. as I stated. Sorry about the error. It didn't make much sense the way I first wrote it.

TailTwister

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I'm not bashing 4 strokes at all. Just to clarify, I've just had those "newbie" kind of problems. I had the 72 and it would not turn the rpm that others had posted. So, I cranked the needle in until I heard this awful sound and "BOING" there goes the spinner. Obviously it was way too lean. I still did not have the power others posted. I got some good advice and instructions about setting valves, and all could be fixed at this point. The YS just whacked me a good one on it's early runs. I'm still shocked I didn't have a broken bone or two from that. (Thank goodness for real heavy leather gloves!) It may just need an hour or so of run time to settle. I gotta buy a new chicken stick too. It's only got a couple of tanks through it now. I've never had quite this much of a time getting a 2 stroke ready to fly. I think that, with all of the good comments about the Saito and YS line, I'm the problem with my 4 strokes. It's just frustraiting. Oh well, I'll figure it out in April.

For my taste, I'd put an OS 91 FX in the Doghouse. To really bring out it's best, maybe a Saito 100 would be better. I do not think the horsepower has anything to do with it. I think those two engines are a real close match up in many ways. The selling point for me, as for 4 strokes, is the linear throttle control and noise. My Rossi on a 12.25x3.75 (14,500 rpm @ 10 or 11 pounds of pull) would probably hang tough with this Saito 72 on a 13x6 or 14x4, but it is easily twice as loud and takes quite a lot of throttle work to hover it in a stable fashion. Lord help you when you try to creep a plane down in a slide. UP...DOWN...UP...DOWN...UP...DOWN. It's a bit of a pendulum effect. I hope the 4 strokes can help eliminate that, with the way they respond to throttle changes.

Spaceman Spiff

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Again, No disrespect, but i disagree.

If two engines are spining a 16x6 prop @ 10,000 RPM they are applying the same torque to that prop. RPM and how quickly the RPM changes tells the whole story.

The OS 91fx and the Saito 91 is an excelent comparison. same weight, same displacement... maybe your experience is different, but my FX is spinning a 16x6 @ 10,000 RPM (and i haven't added the pipe yet!) while my saito 91 which weighs only 30 grams less (less than an ounce less) spins a 13x6. @ 10,000 where did this notion that 4 strokes spin bigger props come from?

You can dispute the Horsepower data if you want, but the voume of air moved by these two engines confirms it. the 16x6 prop on the FX is moving 200 square inces of air columb, while the 13x6 prop on the saito is moving 132 square inches of air

I will agree that most 4 strokers transition more relaible than SOME 2 strokes, but thats where the the Mousse Can comes in. the benefit is not just top end power. the can changes the dynamics of how much and how fast the tank pressure develops. i haven't had a lot of experience with tuned cans yet, but in both cases ive used them i noticed the throttle responce and linearity improved greatly. The reponce from idle to 13700 RPM is like flipping a light switch, boom! i don't know how your engine behaves, but my expensive saito 72, can't keep up with an old GMS 47 with a 4$ hair product can stuffed on it, and i am even more certain my saito 91 will not keep up with the OS 91 fx.

TailTwister

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How old is the Saito that only turns a 13x6? I'd have to think at minimum a 14x6 and maybe a 15x6 on that motor?

Also (I think) the sustained rpm of a prop comparison is actually comparing the horsepower. The engines ability to change rpm and how well it handles additional load (like a sustained climb) is a measure of torque. X size prop at X rpm is a statement of horsepower, I think. Put a 15x6 on each with the same fuel and see which gets more total rpm (91FX I'd say) and see which transitions better (91 Saito I'd say). Then put on your 16x6 and do it again. The 91 Saito should have a lower number of rpm lost. I'd guess not much, but it should be there. If it is not, then I'd agree that the FX is giving more horsepower and more torque.

Also, I envy you your 10,000 rpm FX on a 16x6. Mine would not do that on a 15x6. I sold it and bought a Webra 120. For the record it only does 10,000 on a 16x6. What fuel was that? I burn 10% Cool Power, and fly APC props.