YAMAHA Genesis (RX-1) install in Kitfox 5

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Posted (edited)

I'm not sure what it'll weigh in at....  As I remember, some installs come in around 170-180 with everything.  Mine will be more than that though with a heavier mount and accessories.  I hope it weighs in  25 to 35 lbs less than the subaru did (NSI paperwork puts the fwf subaru at 225lb).  Will report numbers down the road when all my stuff is in there.

Edited by MN Kitfox 2

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Posted

I'll be following this thread as I'm sincerely interested in this conversion. I have Subaru now and so far so good. But would really like to shed some weight. Very informative thread thank you. 

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Posted (edited)

I'll be following this thread as I'm sincerely interested in this conversion. I have Subaru now and so far so good. But would really like to shed some weight. Very informative thread thank you. 

My biggest worry about this engine is the 10,000 rpms, compared to 5000 rpms for the Subaru which has run 300-400,000 miles in a car without rebuilding.  How many miles does it last in a SnoGo?  EDMO

Edited by EDMO

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Posted

I'll be following this thread as I'm sincerely interested in this conversion. I have Subaru now and so far so good. But would really like to shed some weight. Very informative thread thank you. 

My biggest worry about this engine is the 10,000 rpms, compared to 5000 rpms for the Subaru which has run 300-400,000 miles in a car without rebuilding.  How many miles does it last in a SnoGo?  EDMO

I agree, that's my concern but really, my only concern is the high Rpms to achieve the hp. I'm just really trying to find a way to achieve more useful load without going back to 2 stroke. 

My plane is totalling 722lbs and with two of us flying there's limited space left for fuel. 

I have completely rebuilt a BMW 1150 engine but am just at a wiring harness and computer snag. Until this Yamaha engine caught my eye

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Posted (edited)

I had the same thoughts guys, and have had 16 subaru cars in the family with millions of low maintenance miles on them.  But here's what I came to:  

Subaru car runs avg 2800 rpm and what maybe 60ish hp avg cruising along at highway speeds.  The Subaru in airplane works much harder for sure, and is typically modded up for more hp, which I find troubling.

The yamaha on the other hand runs 10,300 rpm in a snowmobile and the R1 motorcycle that the engine was born from raps out 15,000!  Stock HP is 140, but sled guys run turbos in the 200+ HP range with very reliable results.  It therefore, conversely to the subaru, is running detuned in the airplane (which I find comforting) at about 9200 rpm and is internally geared at 1.19 to an output shaft rpm of 7700 and 125-130 hp.

The snowmobile guys have reported it very reliable with many machines over 30,000 miles (approx 1000 hrs at an avg speed about 30-35 mph) and one example with over 100,000 miles.  That can be contrasted to the generally accepted rebuild time for a 2 stroke snowmobile in the 6,000-9,000 mile timeframe.

Is the RX-1 perfect in the snowmobile? NO.  Do they break down or fail in the snowmobile?  Rarely, but yes.  But so would some Subarus that were modded up for more hp by shaving heads and changing cams (as I understand my 118hp NSI e-81 was).  Especially if that modded subaru car was pushed for near max hp for 10 min straight like it often is during takeoff and climb in an airplane.  Yes, sooby lovers, they do do well in airplanes, but they are not perfect either! 

So along those lines of thought I found more comfort in the Yamaha over a Subaru (detune vs. "uptune").  The big question then was how about yamaha over rotax (912/914).

To that I entirely concede that a 80 or 100 hp rotax has an outstanding reliability factor, with decades of data to back it up.  Problem for me is that I want to run a continuous 100 hp, with 130 available to get off the water and over the hill on the other side of the lake.  Rotax wouldn't do that unless I did a zipper kit.  But a zipper kit strips the top half off that ultra reliable rotax and replaces it with aftermarket parts... and again we are trying to get MORE out of an engine than it was designed for, instead of detuning from it's design.  That (zipper) was going in the wrong direction for my taste, and also way out of budget.

So then along comes Steve Henry.  The first big name to run the RX-1 in a fixed wing plane, tune it correctly, push it hard, and prove it out.  Teal's kit had been out for a few years (run mostly in gyros) and the motor and c gearbox proved to hold up well, then Steve proved it for us airplane guys and worked out some important details along the way.  

With steve now at about 250 hours, and 20 or 30 other skytrax conversions out there we assumably have around 2000-4000 hours on Teals kits, with only one reported malfunction (a bearing failure in one c gearbox which held up for an extended flight and the pilot did not suffer power loss).  

That bearing failure I am told was likely due to a defective bearing.  Unless another same location bearing fails on another unit, then (the way I see it) it is reasonable to accept that analysis.

Anyhoo,  with that background on Teal's Skytrax kit, along with my experience with my RX-1 snowmobile, I decided to move ahead with this project.  And as with any single example of a particular plane and engine, only time (and some luck) will tell if I made a good choice ;)

 

.

Edited by MN Kitfox 2
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Posted

I cant argue with your logic on the SnoGo engine.  It has been too many years for me to keep up with the original article I had about the testing Subaru did on their engines, but in a nutshell:   Aircraft engines are "certified" when they are run on a test bed, some of the time at idle and or part-throttle for 150 hours - maybe not continuous.  Subaru put 6 or 7 of its cars on a track and ran them day and night continuously at WOT for about a week, stopping only long enough for fuel and changing drivers - I think they ran about either 60K or 100K during that time.  I believe someone calculated that they had to be turning over 6000 rpm to do that mileage.  All of the cars finished the test run without one repair or failure.  That's endurance!  EDMO

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Posted

Yep, those subarus are something!  The only one of the 16 I blew the motor on was an old undermaintained 1978 1600cc.  It was my fault and not the cars ;)

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Posted (edited)

RX-1 IGNITION :

Been waiting for the mount to come back from the welder, so I've been digging into other things on the plane.

One is wiring ignition power to the ECU.  There is a single wire for that and I believe it is the only power source to the ecu, making it critical to keeping the engine running.

I decided to power it from two sources, each switched and CB protected.  One source will come directly off of the engine magneto (alternator coil), prior to the main fuse for the charging system.  The other power source will come from hot battery direct. I will put a surge protector on the magneto side in case the engine's voltage regulator were to fail.

I will also will diode protect each power source to prevent backfeed if I get down to one source (example that if the magneto were to fail I would want to switch the master off to conserve the battery, but would not want my panel being fed backwards through my ignition hot battery wire).

So that is my plan.   Any electrical engineers out there (or just people smarter than me!) please speak up if you see me going wrong!

Edited by MN Kitfox 2

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Posted

How is the project coming? Do you have a list of thing you took off the sled ? A motor and computer purchase , or should I buy a complete sled?

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Posted (edited)

LOW VOLTAGE ALARM:

Since the RX-1 ECU needs a power source to keep the engine running, I put in a low voltage alarm in to warn me of any battery / charging problems.

The low voltage alarm has two leds, green when above threshold, red with loud alarm when below.  Threshold can be set to any value with a smal pot adjuster.

I put it and a voltmeter into a 2" round instrument hole and set the alarm to 11.5v

All for only $5

 

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As far as buying a motor, I have always thought that getting the whole sled is best.  That opinion is strongly biased since I live in snow country with sleds for sale all around me.  Here are my 3 thoughts for buying an entire sled:

1.  You can give the motor a little run time, pre-tune it, and make sure it isn't about to throw a rod or something.

2.  You'll have the following extra components:

Airbox, oil tank, oil lines, thermostat housing, coolant overflow, coolant hoses, exhaust flanges (flex type), wire harness, ECU, voltage regulator, fuel pumps, starter solenoid, and a few others that I'm forgetting here and will edit in later.

Some of that stuff you will use, some you will not.  But it is really nice to have a pile of options to work off of and modify to work.

And 3,  you will have a reference on how all the little things are set up and routed (like carb heat lines, oil lines, ect)  Hopefully this build thread will detail all of that as I go, but there have been times where it has been nice for me to run out to my RX-1 snowmo and peek under the hood as the "cheat sheet"!

But there is a ton of work parting out a sled!  So if the right deal came up on a motor, you'd just want to make sure you plan some $ to ebay up any missing components that you might need.  And that is a great thing about the Yamaha:  parts are plentiful and cheap!

Edited by MN Kitfox 2

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Posted

Wish you live closer. Understand all the little parts, I have done a couple repowers.

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