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Yamaha Aircraft Engines: A History & Buyer's Guide

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GTX_Engines

Active Member
Joined
May 17, 2013
Messages
34
Location
Columbia, SC
It is wonderful to see Yamaha Genesis engines have now been provided their own category here on HBA. Thank you.

HISTORY

Pretty sure this is your first thread on the subject.

First mention of Yamaha on Homebuiltairplanes

The thread above was posted 10/9/2010. I found the HBA forum and that thread 5/17/2013, 7 months after I finished building and started flying the first successful Yamaha Genesis 4-cylinder engine, after running a Google web search.

By the time this thread was posted late 2010 Rotaryforum.com (RF) already had several gyrocopter build threads with over 250,000 views each. The pioneer was Todd Reick, "Racer" on the RF, who built the first successful YG3 in 2007. (In all posts related to Yamaha aircraft engines I simplify everything so that Yamaha Genesis = YG, plus the number of cylinders. Thus YG2, YG3 & YG4.)

That was a 120 HP carbbed engine out of a 2005 Vector, the first model year for the YG3, which he installed on a single-place Air Command gyrocopter which I witnessed fly for the first time at the PRA annual convention at Mentone, IN, that year.

He built a second kit and shipped it to Ron Awad, who posted up the largest Yamaha build thread on RF the following year. That engine went on a tandem Dominator gyrocopter, which I had the pleasure to fly with Ron at Bensen Days in Wauchula, FL 2009.

Ernie Boyette followed that in early 2010 with the first YG4 build. He did get it flying, but ran into several problems, many which stemmed from buying just the basic engine and not the whole sled. He failed to grasp the importance of exhaust length and pipe diameter, and intake plenum wave balance. In starting off with just the engine, he found himself at a loss to understand where everything went and what it was supposed to do so far as the wiring was concerned.

His conversion was never reliable, and the engine would shut down or go to idle unexpectedly in flight. When it did fly, it was down on midrange power badly, thus throttle lag was horrible.

I took a swing at building a YG4 gyrocopter in 2011, choosing to buy a complete 2003 RX1 140HP sled to dismantle myself. I used everything stock - intake box, exhaust pipes and muffler, wire harness, oil reservoir, cooling lines, and multi-function display/tach. The result was a perfect conversion that experienced no hiccups in the least right out of the hanger, and had all the power available as it did on the sled with crisp, full throttle response and no throttle lag whatsoever. First flights were in November 2012, and demonstrated at several fly-ins around the country in 2013.

People started asking me for help with YG4 conversions immediately.

One person I responded to, Teal Jenkins, went into business in 2014 with a competing conversion kit.

In 2017 I announced a 150 HP Apex YG4 conversion kit for sale. Steve Henry bought the first one, installed it on a modified Highlander, flew it to Oshkosh from Idaho and won every STOL drag competition and the Lindy Grand Champion Award 2018.

No one ever done this before, nor since - and the record still stands.

As to the wiring looms, the RX1 loom is pretty basic as this is a carbbed engine. I was making and selling those going back to 2013. The Apex loom on the other hand is an EFI system that is rather complicated and has a number of limp-mode safety loop-backs which are extremely dangerous on an aircraft. Steve knew of a fellow who had successfully configured an Apex loom for a FW he had put together (with a one-off belt drive), and that guy gave Steve a worksheet to defeat the unnecessary electrical garbage and limp mode loops.

Steve shared that info with me, and I started making and selling Apex wire looms in 2018. Steve also shared that info with Ian Bange and Ian started making and selling Apex looms in 2019.

Through 2018 and 2019 I sold dozens of Apex conversion kits and wire looms, all of them successful and the customers completely satisfied.

In 2019, along with the arrival of Ian Bange selling wire looms, Teal Jenkins started selling a purpose-built gearbox for the Apex YG4.

The YG2 Phazer was a totally different animal to contend with. Todd Reick tried to convert one on a customer's gyrocopter and it was a miserable failure. He declared it to be useless as an aircraft engine. However, Another fellow up in Canada came to me with news of a successful YG2 install he had completed on a single place Dominator gyrocopter, and I was encouraged to take a swing at it.

A second guy announced had one running with a prop on a test stand and was seeing no problems with getting the engine to spin up to cruise and climb power. I built a MAC conversion kit, figured out the wiring, and sold my first setup to Gil Audibert in 2019. Gil tried a few different things with exhaust and intake box and quickly realized that what I was preaching about exhaust length and intake wave tuning were not just tips, they were requirements. He got his Quicksilver float plane flying before years' end, and enjoys flying it often.

His best friend of 44 years who owns Quiksilver (Air-techinc.com) is eager to work with Gil and me to fabricate and start selling YG2 Quicksilver engine mounts to be sold through his website.

Last month I completed flight testing on the first 165 HP YG EXUP, the latest "first", and latest of many, varied, successful Yamaha kits available for sale through my website MohawkAero.com and by direct email to Info@MohawkAeroCraft.com.

The Apex EXUP has a titanium exhaust with a variable ECU-controlled valve that adjusts back pressure so that it constantly tunes the exhaust for optimum power throughout the entire power band. The result is 15 more HP on the top-end, and 10-15% more power throughout the mid range. Having flown the only one in existence on any aircraft at this time I can attest to its fantastic response and performance. I installed the engine on Geoff Resney's Air Command tandem gyrocopter, which he plans to fly at the PRA convention at Mentone, IN, July 29-Aug 1. The aircraft has been lovingly nicknamed "Godzilla", and is now the most powerful gyrocopter flying today in terms of thrust-to-TOW (TTW).

When I get my own, original YG4 Air Command (The Wicked) back in the air in time for Mentone next week (it rolled over while taking off from a beach near Savannah) that will mean that all three of the top most powerful gyrocopters flying today will be Air Command YG4's built by Greg Mills of Mohawk Aero. Godzilla is at the top with 82% TTW, Kurt Carleson's single place 140HP YG4 is second with 75% TTW, and The Wicked is third at 73%, and the popular Tango Gyro YG3 135HP is a fourth at 71%.

Yamaha is king in the gyrocopter world. The best Rotax 915 comes in at 71%, mounted on either an MTO or Magni gyrocopter. Lycoming IO-320 is so far down the list it isn't even worth mentioning, a veritable flying brick at 52% TTW. That guy reports a climb rate of 1100 FPM, but is that sustained? Kurt's reported sustained climb is in excess of 2000 FPM.


BUYER'S GUIDE

(Listed by historical year of manufacture)

YG4 140 HP 2003-2005, 998cc, 4 carbs, 125 lbs with starter motor & carbs, sans exhaust. 600 lbs thrust. Listed as RX1 & RX1 Mountain models. Exhaust is 4-into-2 at 21" to the collector. This engine has an internal counter shaft with gear reduction 1.19:1 and rubber harmonic damper, aming it a superior choice for propeller driven craft of all types. In the event of catastrophic electrical failure the engine will continue to run, since it has dual pulse pumps and needs only the two-wire connection to the crank counter on the mag to time the individual coils atop the sparks plugs, and battery power well below 12v to keep running. The internal engine parts are straight off the R1 motorcycle engine assembly line. The R1 revs past 15,000 RPMs. Since the sled clutch works at a shaft speed of up to 8700 SRPM, with the internal gear reduction the YG4 is limited to making power up to "only" 10,500-10,700 ERPM (engine), and max power 140 HP comes on around 9800 ERPM and stays flat to 10,500 ERPM. Built to perform up to 10,000' MSL. Carb rejetting has been shown to improve hot weather, and high altitude performance. Engines operating in high cowl pressures with proper jetting show an increase of up to 15 HP. First aircraft conversion builder: Greg Mills, c2012. Existing conversion parts dealers: Greg Mills (b2013); Teal Jenkins (b2014).

YG3 120 HP 2006 - present (?), 1040cc, 3 carbs, 122 lbs, with starter motor, carbs, sans exhaust. 515 lbs thrust. Listed as Vector, et. al. Exhasut is 3-into-1 and 21" to the collector. This engine has no countershaft, no harmonic damper, and will not start with a prop attached to the gearbox without a clutch. The water pump has a plastic impeller which we advise you replace with a metal one, as the plastic ones have been breaking and causing the engines to overheat. First aircraft conversion builder: Todd Reick c2007. Existing conversion parts dealers: Greg Mills (b2013); Tango Gyro (b2015)

YG4(i) 150HP 2006-2010, EFI, 998cc, 118 lbs with starter, throttle bodies, sans exhaust. 640 lbs thrust. Listed as Apex, Attak, RX-10, Apex Mountain. Same engine as above with EFI, minor modifications to reduce weight; and cam profile adjustments for better fuel efficiency and more top end power. The countershaft is geared slightly taller at 1.23:1. Increasing intake plenum pressure by 2 PSI, with no other modifications made to the engine, has been proven to result in a 22HP increase, to 172 HP. You can do this anyway you like, since the egnine has outside air pressure sensors, as well as intake plenum sensors for both AP and temps. A "Yamahacharger" bolt-on kit is available for only $1500.00. First aircraft conversion builder: Ernie Boyette, c2010. Existing conversion parts dealers: Greg Mills (b2017 complete kits & wire looms); Teal Jenkins (b2019 PSRU only); Ian Bange (b2019 wire looms only), Steve Henry (b2020, complete kits reselling Jenkins & Bange).

YG3(i) 135 HP 2006-present (?), EFI, 1040cc 122 lbs with starter, throttle bodies, sans exhaust. 580 lbs thrust. Listed as many models under two different makes, both Arctic Cat and Yamaha. Let's just say it is a Nytro, so I don't have to go through all the mess to list everything here. Same as the carbbed engine, same conversion problems mentioned above. First aircraft conversion builder: Tango Gyro, c2017. Existing conversion parts dealers: Greg Mills (b2017); Tango Gyro (b2017).

YG2 80 HP, 2007 - Present (?), EFI, 500cc, 88 lbs with starter and throttle bodies, sans exhaust. 340 lbs thrust. Listed as Phazer. 2-into-1 with 21" to the collector. This engine is basically a YG4 cut in half, and also has the countershaft with a very tall 1.47:1 reduction. I see no reason why we can't slap a Yamahacharger on this little bird and really make her tweet. First aircraft conversion builder: Greg Mills, c2019. Existing conversion parts dealers: Greg Mills (b2019)

YG4 165 HP EXUP 2011-2018, EFI, 998cc, 118 lbs with starter & throttle bodies, sans exhaust. 700 lbs thrust. Listed as Apex, sometimes seen as Apex EXUP. This engine has a titanium exhaust header straight pipe set converging 4-into-1 at 21" with a butterfly valve controlled by the ECU. This allows for a slightly larger 1-1/2" ID pipe at the head flange by closing down the flow at the collector. At WOT the valve is fully open and the added ID flows an extra 15 HP. Throughout the midrange, the valve adjusts back pressure to not only maintain power, but actually increase it over the earlier non-EXUP YG4. The pre-production model shipped to the USA for evaluation dyno'ed out at 165 HP, whereas the production stock sleds only gave up 150HP at top end, even though they showed 10-14% midrange increased performance. Yamaha did this to meet EPA standards, and it didn't take long to figure out how to get around that and realize the engine's full potential. It has been found that simply adding a Yamahacharger to this engine does little to nothing due to the ECU map. First aircraft conversion builder: Greg Mills, c2020. Existing conversion parts dealers: Greg Mills (b2019)IMG_8500 (640x480).jpg
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
849
Location
Jackson
Hi Greg,

What's the YG2 (Phazer) output shaft rpm at rated power? I saw your mention of the 1.47-1 internal reduction, but haven't seen a spec on its crank rpm at rated HP.

Thanks,

Charlie
 

GTX_Engines

Active Member
Joined
May 17, 2013
Messages
34
Location
Columbia, SC
Hi Greg,

What's the YG2 (Phazer) output shaft rpm at rated power? I saw your mention of the 1.47-1 internal reduction, but haven't seen a spec on its crank rpm at rated HP.

Thanks,

Charlie
Take a look at this dyno chart provided by an aftermarket group. I don't believe their reported numbers showing the huge increase in power when their product is installed, but at least this gives us a pretty good idea of what's going on with the power at any given SPRM. For CRPM multiply the SRPM by the internal reduction 1.47.

Peak power comes on at 7800 SRPM, 11,500 CRPM (tach reading).

Gil has his prop pitched to run the crank in the 10,000's
phazer_power_graph.gif
 
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