So I received a message from a builder advising me of his engine choices for the 701.  I asked about the Raven 1.3 conversion and I haven't gotten feedback to the choice.  The wieght, next to the Jabiru, is the closest to the Rotax 912S.  The Rotax 912S is the preferred egine choice but is also the most spendy. I wanted to open up a discussion on powerplants for the 701.  I want to know why not the Raven 1.3 or tell me what would be a good replacement and light on weight replacement for the Rotax 912S.  

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701 has powerplant weight limitations read the plans first choose the engine second

Last time I looked the Raven is too heavy to meet this requirement. Yes there are "701" flying with them but these are "homebuilt" class aircraft, you can fit a V8 if you want to operate it in that category.

Most suitable lighter engines than the 912s are 2 strokes: Siminonini for example, or 3 cylinder Hirth.

There have been some promises of rotary engines, none have made it beyond prototype testing (unfortunately)

Ralph
Casey - I was the first to answer your question and I know I dodged your Raven question. The airframe to the 701 is very picky when it comes to powerplants. Then there are the questions of what will it take to get the engine (Raven) to operate and perform reliably over an extended period of time. We can go on with this discussion forever. If you are a tinkerer and love that kind of challenge, by all means do it. Just be prepared for a CHALLENGE and lack luster performance from the airframe. But if you're looking for most efficient and reliable Raven is not it (my opinion). At the moment Rotax and Jabiru are the most promising. UL Power 260i through "Fly With Gus" may hold some promise. I believe you can find a reliable used Rotax on the market; it is a buyers market right now and will be for a while. Whatever way you go you'll find a bunch of guys with alot of experience on this sight. We all learned a great deal from each other. Good Luck - Chris
First, I agree with Chris.

My choice for the 701 would be the Rotax 912 or 912S, 80 or 100hp. 100hp if you want to be a helicopter. The Jabiru is good option, but I feel that the Rotax with liquid cooling is a better choice for the 701.

That being said, I've heard from those that say the Rotax has problems, but they don't have a Rotax. I know a couple of Rotax owners and they only have good things to say about the engine.

But we live in an Experimental world, anything goes. Do you want to spend more time flying or working on the airplane?

jake
So Jabiru and Rotax are the preferred choices. Tell me more about the VW line of engines. Are they any good and how is their weight?
Many builders have managed to mount them on 701s. I would recommend if you do, mount a reduction unit. It will increase the weight but you will be able to turn an appropiate size prop. As far as weight goes after all is said and done you will be within a few pounds of max engine weight, which is approximately 180 lbs. The VW has far more RD then other autos and does not require a radiator. Wayne Clagg has done extensive work on his and from what I understand may still be tinkering. You might want to give him a buzz. I still hold fast to the Rotax. You can't judge cost of an engine project just by initial engine cost. Wayne should be able to shed alot of light on this subject.
great, I am sold on a Rotax or Jabiru. Now the big question. I will take me some time to save for a engine. Is there a place I could start looking for a used Rotax/jabiru or a place that you can buy them that need rebuilt?

Casey
Your best bet is to follow Barnstormers, there have been a few 80 hp rotax's for around $8000, with low hours. I do not want to knock Jabiru but it you want performance you will want to use a rotax.

Pat
I appreciate the input pat. I will keep my eyes open for a Rotax. Now, which one? (912S or 912)
You missed the discussion we had a couple of weeks ago concerning vibrations, start-up shaking, and abrupt stops associated with the high compression 912ULS 100 hp..... Any airframe is limited to the speed at which it can cut through the air or forces it can withstand REMEMBER THAT. There is such thing as overpowering an airframe. The performance the 701 can provide can easily be accomplished with the Rotax 912 80 hp. I can expand greatly on this reasoning but I'm not. The factory demo went for its first 1200 hours on a Rotax 912 80 hp. However, it seems, the new ring mount makes a difference (concerning vibrations) with either engine; especially the ULS...... Pat is right about Barnstormers; check them out.
Thanks for the input. Did you plans build? What is the best method to transfer the image from paper to a wood former?
I did plans build. I took the long way around and drew out the geometries (according to the measurements) on poster board then cut them out. Traced it on the wood and cut that out. You have to be very careful about tracing the image. CAD draftsman tend to zoom in and out when drawing this changes the size the image will print out. Therefore, its better to go by the measurements instead of the image.
I just looked at the flyer from Oshkosh '10 says "max engine weight 185lbs". The Raven 1300SVS meets this in real world terms. The Rotax also does, but only by 8-12 lbs less then the Raven. The Raven will perform close to the 912, but the 912s will leave it way behind. Speed for all is due mostly to weight and drag, so clean it up. I have been struggling with this since I started building and have spoken to a number of different people with first hand experience with the Raven. A 912 it is, a 912s its not. But you can add the Turbo if you must. That will put you over the 185lbs by a bit though. The one thing that the 912 does have in spades over any conversion, is that YOU are involved in it manufacture, so you can use low quality parts, heavy parts or poor performing parts. The factory does not allow this for the 912.
As for tinkering, none of the guys I've spoken with do much at all... I asked.

As for mid time 912s cheap.. saw one in 3 years, it has already sold.But it was a low SN model so low tbo and the parts are not insignificantly priced. If they are so readily available then someone should start connecting people with them.

If you have not purchased anything yet, and if money is an issue, build the 750, engine choices are more varied.

Kevin

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