Anything new on Yamaha conversions?

NoWingsAttached

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Here is my take on it!
I had an rx 1 snowmobile it turned 11000 rpm and had a gear reduction to make the clutch turn 8000 built into the engine.
It would scream and go like hell on a road or river but was next to helpless in deep snow.
At part throttle like around 8000 rpm it felt more like 40 horse.
You had to get it up to the crazy high rpm before it would work.
If you seen deep snow ahead and pinned it it could not get the rpm up quick enough

The internal reduction is 1.19:1, and at 11,000 RPM the countershaft turns the primary clutch sheave 9,244 RPM - not 8,000.

At 8000 engine RPM (ERPM) the YG4 makes 125 HP in ideal atmospheric conditions. I can personally vouch for the accuracy of the chart, below. I ran a 110 HP Arrow engine and never got the (very) draggy Air Command over 75mph at full throttle, while the YG4 at 8000 has seen 80 MPH sustained IAS, straight/level, on numerous occasions. The reliable power of the YG3 and YG4 engines is inarguable.

It is no secret that the RX1 is/was a heavy sled and that other sleds (read 2-cycle) perform better in deep powder. If you are running deep powder in an RX1 often, you probably would do well to change the clutch settings and/or springs to engage at a more advantageous ERPM, and perhaps change the chain drive gears as well.

As for me, "we" typically try to take off and land on previously cleared runways, and avoid deep powder. Come to think of it, there is no deep powder in Savannah - and I am the only guy in Georgia with a snowmobile!
 

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NoWingsAttached

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Hello, I am going to be testing one of my RX1 engines with different cam timing positions on the engine stand. It appears on the surface that the cam timing (primarily the intake cam) can be advanced to lower the hp/torque curve in the RPM. Obviously there is no free lunch here as it will be also dropping top end HP. I would like to cruise around at a lower RPM and have the power lower in the range. 140 Hp is more than what I need., Even though Its been fun to play with it since I can almost climb vertical at high rpms. I would rather de-tune the motor to get somewhere are 115 [email protected] rather than 140HP at 10,000 RPM. Now these are thereical numbers based on boreXstroke and compression ratio I wont know what it will be until I can get some measured bench runs. My question is has anyone on here played with the cam timing to detune the RX1 and what was the outcome? Thanks

Changing cam timing has the possibility to smooth out the engine roughness when you first start it up. I have thought about a cam regrind to change the low-end overlap of the intake/exhaust, but decided it isn't worth the expense and trouble. I'm glad to hear you are going to play with simple timing, that may turn out to be a cheap fix to the start-up roughness issues of the YG3 and YG4. (But I'm not convinced I would always want to sacrifice power just to avoid installing a cheap $500-$600 clutch on the drive or prop flange. When you're talking about a power plant that is going to run $6000 - $10,000 all-up, what difference does $550 make?)

Please provide an update when you can, Teal! This is a very exciting development.

I really love my Arrow redrives for the YG4, but had hoped the chain drive would be a solution to the rough start problem in place of using clutches, whether they be one-way or centrifugal.

My new Silent Drive does allow the engine to start every time w/o a clutch, but it is still too rough on the equipment. Yesterday one of my header welds inside the flange broke during a particularly hard cold start. It usually starts on the first turn of the key, but I tried cold-starting it without the choke and it took several tries. Dangit. And just as I was going to leave for Mentone, too. Glad it happened here, and not there, though.
 
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Vance

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Dyno Chart?

Dyno Chart?

The internal reduction is 1.19:1, and at 11,000 RPM the countershaft turns the primary clutch sheave 9,244 RPM - not 8,000.

At 8000 engine RPM (ERPM) the YG4 makes 125 HP in ideal atmospheric conditions. I can personally vouch for the accuracy of the chart, below. I ran a 110 HP Arrow engine and never got the (very) draggy Air Command over 75mph at full throttle, while the YG4 at 8000 has seen 80 MPH sustained IAS, straight/level, on numerous occasions. The reliable power of the YG3 and YG4 engines is inarguable.

It is no secret that the RX1 is/was a heavy sled and that other sleds (read 2-cycle) perform better in deep powder. If you are running deep powder in an RX1 often, you probably would do well to change the clutch settings and/or springs to engage at a more advantageous ERPM, and perhaps change the chain drive gears as well.

As for me, "we" typically try to take off and land on previously cleared runways, and avoid deep powder. Come to think of it, there is no deep powder in Savannah - and I am the only guy in Georgia with a snowmobile!

Horsepower and torque have a well defined relationship Greg.

Horsepower = Torque X RPM divided by 5252.

This relationship appears to me to be missing on your posted dyno chart.

8,000 RPM X 74 foot pounds of torque divided by 5252 = 113 horsepower even though your chart shows 126 horsepower.

10.200 RPM X 68 foot pounds of torque divided by 5252 is 133 horsepower even though your chart shows 150 horsepower.

It appears to me that your chart is journalistic fantasy that often arises when the published numbers can’t be achieved.
 

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teal

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I am not having any rough starting issues. Maybe because I live in a warmer climate? I had that Issue a few times on my first YG4 but after I cleaned and readjusted the carbs it went away. My goal is not to cure any rough starting but to get the torque curve lower in the RPM. I'm not sure if my testing will help you decide wether this will help your rough starting issue since I don't have this issue to start with however if it exibits rough starting after I make cam timing changes we can infer that a cam timing change will make your problem worse.
 

teal

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That's a very good point Vance thanks for bringing that to light. Manufactures and dyno operators have tricky ways to get to some of the numbers. If you have a torque and a RPM at that torque you have the HP. Its MATH!
 

NoWingsAttached

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Horsepower and torque have a well defined relationship Greg....

It appears to me that your chart is journalistic fantasy that often arises when the published numbers can’t be achieved.

Vance

Only a putz would ignore the obvious. First, the graph uses HP as the scale. MS Excel is limited and won't allow adding a second Torque scale so I used ~1/2 HP as a general indicator to illustrate the torque curve as a relationship to HP - certainly NOT to provide absolutes in terms of torque numbers.

Second, a professional will recognize at once that there are acceptable limits to accuracy in any measurement, as well as limits in interpreting the graphing of that data. The accuracy of any data given is nonsense unless it comes with a suitable range of error. If none is provided specifically, then it is to be interpreted as +/- the increments shown. HP numbers according to the graph are therefore only accurate to within +/- the increment between the numbers indicated: +/- 5 HP. If I wrote the graph in 1 HP increments, you could then interpret the data to within +/- 1 HP.

Torque can be approximated to within 1/2 that, or+/- 2.5 pounds per foot.

Class, may I have your attention please? You there, in the back, stop passing notes to Suzie. You two can canoodle after the bell if you like.

Let's look at the data given for 8000 ERPM. The HP indicated is closest to the 125 line, and within the margin of error is therefore to be interpreted as anywhere between 120-130 HP.

Torque looks to be closest to 145 on the HP scale, and is therefore

1/2 x (140 > 150), or T = 70 > 75

ERPM is +/- 500 ERPM, therefore 7500 > 8500

So what does this all mean? Well, the HP you can accurately extrapolate from the data provided is anywhere from 70 to 75 PF @ 7500 to 8500 ERPM, which is therefore in the range of 100 HP > 121.4 HP.

Vance, from his front-row seat: "AHA!"

Not so fast, Mr. Breeze.

You see, (third, and finally) the data was taken at well over 1500MSL, in Vermont. Forgetting about humidity and temperature (It was done indoors, so if you really want to do this at home, you can assume 72F and 35% humidity), we adjust for altitude: about 3% per thousand feet if memory serves...

That means you have to add back 4.5% to the data, and now the adjusted HP under ideal atmospheric conditions (the only scale anyone can ever use universally) we now see that the accepted, adjusted, range is 104.5 HP > 126.8 HP.

The numbers are certainly, inarguably, well within the stated claims.

How many times do we have to go through this, Vance, before you accept the fact that this motor makes 140-150 HP? I gave you one of these sheets in hard copy, printed on card stock for durability, at Mentone 2012. I have discussed the graph and the YG4 power many times previously, here and elsewhere. This graph is absolutely bona fide and accurate as published - whether you want to acknowledge the fact or not. However, understand I do not require your endorsement.

I had the YG4 climbing at 8700 RPMs using 2.58:1 gears at Bensen Days 2013, and you, yourself, said here on RF candidly, afterward, that it appeared to you that I was running at about 130-135 HP at the time. Now you're trying somehow re-interpret the data you had in your hands at that time, and your own personal observations, to try to cut me down yet again for the umpteenth time for your own amusement? What, exactly is your agenda, and what are you trying so hard to shoot down and prove? You can't have it both ways. Apparently you didn't like it when it came out after Bensen Days that I was only running 8700 RPMS when you witnessed my gyrocopter in flight. I guess you thought I was running WOT at 10,700 RPMs? ROTFLU, boy. It NEVER ran more than 9000 on ANY day, for 130 hours, until just this year when I re-geared the PSRU to 2.72:1 and now run up to 9400 ERPM at 10 - 3000' MSL summer days.

Whatever. I'm out.

See you folks at Mentone. Look me up there, and check out the new Mohawk Silent Drive GTP.
 
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Vance

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Vance

Only a putz would ignore the obvious. First, the graph uses HP as the scale. MS Excel is limited and won't allow adding a second Torque scale so I used ~1/2 HP as a general indicator to illustrate the torque curve as a relationship to HP - certainly NOT to provide absolutes in terms of torque numbers.

Second, a professional will recognize at once that there are acceptable limits to accuracy in any measurement, as well as limits in interpreting the graphing of that data. The accuracy of any data given is nonsense unless it comes with a suitable range of error. If none is provided specifically, then it is to be interpreted as +/- the increments shown. HP numbers according to the graph are therefore only accurate to within +/- the increment between the numbers indicated: +/- 5 HP. If I wrote the graph in 1 HP increments, you could then interpret the data to within +/- 1 HP.

Torque can be approximated to within 1/2 that, or+/- 2.5 pounds per foot.

Class, may I have your attention please? You there, in the back, stop passing notes to Suzie. You two can canoodle after the bell if you like.

Let's look at the data given for 8000 ERPM. The HP indicated is closest to the 125 line, and within the margin of error is therefore to be interpreted as anywhere between 120-130 HP.

Torque looks to be closest to 145 on the HP scale, and is therefore

1/2 x (140 > 150), or T = 70 > 75

ERPM is +/- 500 ERPM, therefore 7500 > 8500

So what does this all mean? Well, the HP you can accurately extrapolate from the data provided is anywhere from 70 to 75 PF @ 7500 to 8500 ERPM, which is therefore in the range of 100 HP > 121.4 HP.

Vance, from his front-row seat: "AHA!"

Not so fast, Mr. Breeze.

You see, (third, and finally) the data was taken at well over 1500MSL, in Vermont. Forgetting about humidity and temperature (It was done indoors, so if you really want to do this at home, you can assume 72F and 35% humidity), we adjust for altitude: about 3% per thousand feet if memory serves...

That means you have to add back 4.5% to the data, and now the adjusted HP under ideal atmospheric conditions (the only scale anyone can ever use universally) we now see that the accepted, adjusted, range is 104.5 HP > 126.8 HP.

The numbers are certainly, inarguably, well within the stated claims.

How many times do we have to go through this, Vance, before you accept the fact that this motor makes 140-150 HP? I gave you one of these sheets in hard copy, printed on card stock for durability, at Mentone 2012. I have discussed the graph and the YG4 power many times previously, here and elsewhere. This graph is absolutely bona fide and accurate as published - whether you want to acknowledge the fact or not. However, understand I do not require your endorsement.

I had the YG4 climbing at 8700 RPMs using 2.58:1 gears at Bensen Days 2013, and you, yourself, said here on RF candidly, afterward, that it appeared to you that I was running at about 130-135 HP at the time. Now you're trying somehow re-interpret the data you had in your hands at that time, and your own personal observations, to try to cut me down yet again for the umpteenth time for your own amusement? What, exactly is your agenda, and what are you trying so hard to shoot down and prove? You can't have it both ways. Apparently you didn't like it when it came out after Bensen Days that I was only running 8700 RPMS when you witnessed my gyrocopter in flight. I guess you thought I was running WOT at 10,700 RPMs? ROTFLU, boy. It NEVER ran more than 9000 on ANY day, for 130 hours, until just this year when I re-geared the PSRU to 2.72:1 and now run up to 9400 ERPM at 10 - 3000' MSL summer days.

Whatever. I'm out.

See you folks at Mentone. Look me up there, and check out the new Mohawk Silent Drive GTP.

Words and speculation won’t make your chart correct Greg and neither will calling me names.

My post articulated my opinion that the chart is not correct and using it as a basis for speculation is without purpose.

The horsepower numbers are not nearly as important as the actual performance in a gyroplane over a lot of hours.

A proof of concept with very little testing is a long way from a firs article.

In my opinion you still have a lot to learn Greg.
 

teal

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Greg and Vance, I thought we were sharing info here to help everyone out as a group. I was unaware of the negative comradery or what has gone on in the past. Greg , I in no way nor did I think Vance was trying to insult your intelligence by bring up the fact HP to torque relationship. Thank you going into depth in clarifying the reason this dyno looks like it has less than the rated power.
Mine personally feels like it could have 140hp. I hope we all can share info in a polite manner for the betterment of us all in the future
 

Vance

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I will help any way I can Teal.

I think what you have done is remarkable and impressed to see you continue to push forward.

If I had a Yamaha powered project yours is the setup I would use for the PSRU.

I have been involved in engine development on a fairly high level for many years and I continue to be amazed at how excited people get over dyno numbers.

I had a 78 cubic inch Harley Davidson Sportster that I road raced and the magazines insisted that it was making over a hundred horsepower when we had run it on a California certified water brake and made 89 horsepower. It was faster than the bikes they claimed made 140 to 160 horsepower.

I had another 78 Cubic inch Harley Davidson Sportster than ran 200 miles per hour at Bonneville without a fairing and the magazines all insisted that I must be making 200 horsepower to do that. I had run the engine on the same certified dyno and it made 141 horsepower.


I can’t count the number of people that have arrived at some absurd horsepower number in what we call the JC Whitney way. 10% more for the extra compression, 15% more for the loud exhaust, 20% more for the magic carburetor, 18% more for the cam of the month and 30% more for “blueprinting” the engine.

In my experience it doesn’t work that way.

Actual performance is always more important than claimed horsepower.

A dyno is a wonderful tool and horsepower is a lovely way to quantify things as long as it doesn’t louse something between the readings and the presentation.
 
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StanFoster

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Vance and I share a few things in common. One is neither of us is educated above HS. Both of us refuse to call other people names as we both agree the name caller is usually losing the argument.

Vance however is much smarter than I and thank you Vance for your services you provide. You have shown my ways in error a few times, and I didn't call you names.
 

DASBUR

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yamaha genisis 120 hp

yamaha genisis 120 hp

Hi All

playing with the cam timing is not worth the effort for the little gains if any you will get. We advanced and retarded the cam timing on A genesis 120 engine to try and get more HP at a lower RPM 6200 to 6500 The HP never changed much more than a couple HP 6200 to 6500 it always made right around 95 HP. 7500 to 8000 made 105 hp. We Dyno and record real HP numbers. factory ratings are all ways about 15 to 20% more than what the actual HP is. They add in a percentage for a correction factor. A big inch motor does benefit from cam timing more than a small motor does. we also did advance the ignition made no HP gains we actually lost HP from that.

Doug

Just my uneducated findings
 

GyroRon

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To date Mohawk Aero has two machinists, a welder, a fabricator, a webmaster, an engine mechanic, two partners and four shareholders. (Mohawk Aero Corp. issued 100,000 shares of stock in 2013. The stock has more than tripled in value since my friend, and our webmaster, Jon Carleton, bought his first 183 shares after he set up the MohawkAeroCraft.com website.)

But none of this matters. I am a Gemini. I can say "we" any time I please.

Just remember, you are NEVER alone with a Gemini! :lol::lol:

--------------------------------------------------------------------------------

Dear Ron:

Last year at Barry Days 2014, well before you publicly turned on me like a dog, I stood before you for 20 minutes waiting to say hello while you totally ignored me until I got fed up and left.

What is your problem?

I don't ignore people who come up and strike a conversation with me. Sorry you felt ignored.
 

Lee Scatt

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Facts can be stated as such Vance. It is a fact that his chart is wrong. It is my opinion though, that he study up a little himself, before attempting to enlighten us students.
 

Trackwelder

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Basically wouldn't a comparison between a known aircraft engine and the Yamaha be more informative, at half the weight he is gaining performance if nothing else, does somebody care to take a similar machine with a 0-320 handy to do comparison flights, I personally would be happy if it performed as well as a 0-200 but I am flying a fixed wing.
 

Joe Pires

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Greg none of my business, but this contentious thread does nothing to promote a business. I would suggest if it is your goal to promote your business, use another thread with a fresh start, that perhaps will not deteriorate to what this one has become.
 
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Vance

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Some numbers for comparison.

Some numbers for comparison.

Basically wouldn't a comparison between a known aircraft engine and the Yamaha be more informative, at half the weight he is gaining performance if nothing else, does somebody care to take a similar machine with a 0-320 handy to do comparison flights, I personally would be happy if it performed as well as a 0-200 but I am flying a fixed wing.

The challenge with that Eric is there are very few gyroplanes that are similar, a prop can make quite a difference and how it is set up makes a difference.

I fly larger tandem (The Predator) than Greg’s that probably has a significantly higher CdA (coefficient of drag times frontal area).

My 160 horsepower at 2,700 rpm (checked with a dyno at my airport on a typical day) IO-320 weighs around 260 pounds so it would be reasonable to expect the aircraft to be heavier (800 pounds dry).

I am a heavier pilot at 240 pounds.

I don’t fly with less than seven gallons of gas on board and typically have around 15 gallons (90 pounds) for a typical weight of 1,130 pounds.

I climb out at 2,400 to 2,450 rpm making around 145 horsepower.

I can sustain a climb of 1,100 feet per minute but have seen over 2,100 feet per minute at airshows so some might claim she climbs out at 2,100 feet.

On a typical day at close to sea level I can fly level at about 94kts on 160 horsepower or climb to 7,500 and fly at 95kts on about 120 horsepower.

To help put it in perspective I have a lot of hours in a two place side by side gyroplane (Cavalon) powered by a Rotax 914 with a claimed 115 horsepower that has very similar performance.

We are not building racing gyroplanes so it doesn’t matter exactly what the performance is.

In my opinion if an engine has enough power for reasonable performance (my personal minimum is 500 feet per minute climb) and is reliable than it is enough and all the speculating, bragging and denigrating is without purpose.

The Yamaha sled engines appear to be well suited to aircraft use and only time will tell if it and the PSRU are reliable in that application.

It is a big project making an engine not designed for aircraft use work in an aircraft; probably bigger still in a power hungry gyroplane.

I have around $6,500 in my Lycoming and it burns around six to seven gallons an hour in The Predator. It goes through a quart of oil every four hours. It would be easy to spend $12,000 rebuilding her.

I can understand the desire for something more modern and less expensive like the Yamaha sled engine.

Most experimental aircraft fly less than 50 hours a year and my observation is most gyroplanes fly less than that so longevity is not as much of an issue as it would be for people flying more hours.

An engine out in a gyroplane is often a nonevent so reliability may not be as important as in a fixed wing.
 

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teal

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Thanks for all the great info. Everyone. This is helpful information. Doug do you remember how many degrees you moved the cam or cams. I'm not doubting your information but I like to see what the effects are on the YG4. It doesn't look like it will be that much effort to use so eccentric spacers to move the cam. Just doing the math on the # of gear teeth and the number of holes in the cam sprocket I can move the timing in 1 degree 33 second intervals or roughly 1.5 degrees.
 

Trackwelder

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Vance, ideally somebody would switch one machine back and forth between the engines, but that would take longer than you could expect the weather to remain the same. By taking as close as possible, without worrying about the difference in engine weights if they flew similar that would tell us that power or at least overall performance was equal enough. Like you said we are not racing so minor differences really are minor. In fixed wing experimentals, the engines may vary but other than the engine and overall weight they tend to be much closer. Since as you say the machines are too different to test side by side, we really just need to know if the Yamaha is capable of doing a good enough job for the majority of people at the price.
 
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The internal reduction is 1.19:1, and at 11,000 RPM the countershaft turns the primary clutch sheave 9,244 RPM - not 8,000.

At 8000 engine RPM (ERPM) the YG4 makes 125 HP in ideal atmospheric conditions. I can personally vouch for the accuracy of the chart, below. I ran a 110 HP Arrow engine and never got the (very) draggy Air Command over 75mph at full throttle, while the YG4 at 8000 has seen 80 MPH sustained IAS, straight/level, on numerous occasions. The reliable power of the YG3 and YG4 engines is inarguable.

It is no secret that the RX1 is/was a heavy sled and that other sleds (read 2-cycle) perform better in deep powder. If you are running deep powder in an RX1 often, you probably would do well to change the clutch settings and/or springs to engage at a more advantageous ERPM, and perhaps change the chain drive gears as well.

As for me, "we" typically try to take off and land on previously cleared runways, and avoid deep powder. Come to think of it, there is no deep powder in Savannah - and I am the only guy in Georgia with a snowmobile!

Apparently my observation was not well received!
That sled no way had that kind of horse at lower rpms.
I was only talking about a foot of snow not deep powder.
The load of the sled would not let the engine get up to its power band.
To this day I run a Polaris 750 turbo 4 stroke that will make a RX 1 ton look very bad
Horse power rating is the same!
And it does it 3000 rpm lower!
And it will climb up on 4 feet of snow and go
I personally like the Yamaha engine just not in a sled.
I just cant believe the chart Graff you showed as being correct according to my butt dyno
The torque curve on the seat was more like a 2 stroke not like the straight line on the chart
My numbers were from a machine that I got real sick of real quick and sold it more than 10 years ago so rpm numbers etc were just out of and old memory!
 

Trackwelder

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I had seriously thought that the weber engine would become the one of choice, but it was available in only one snowmobile and now the Yamaha engine is available in 2 brands of snowmobiles and the weber is no longer available, the Yamaha seems to be winning by default.
 
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