mfuess

Not too long ago I purchased a FUJI BT-50 EIS engine just to see what they are all about. It's a nice engine, but I'm not happy with the skewed information they advertise. The engine is 46.5cc, and rounding it up to a 50 is grossly mis-leading. Also, the advertised 5.2 HP is somewhere out there in "dream-land". The engine is rated at 5.2 HP at 10,000 RPM. You'll never see that kind RPM even with their benchmark props! So why bother stating 5.2 HP? This is un-realistic... and certainly not useful data for the avarage modeler.

Please, tell it like it is!
It's a 46.5cc, benchmarked with a 20x10 CF prop turning 7400 RPM. That's approximately 4.631 HP. These are more useful numbers to the modeler. I didn't like the fact that the exhaust & carb were opposite to other 46-50cc engines, so I rotated my cylinder (prior to running it). It runs like a top. SEE:[link=http://tech.flygsw.org/fuji_cylinder_rotation.htm]Rotating the jug on a BT-50 EIS[/link]

The Fuji BT 50 EIS is in fact, a very smooth running engine for a single cylinder. It has EXCELLENT power for a 46cc engine, and it starts very easy. I would like to see Fuji re-think their marketing and just tell it like it is. This is a very, very nice engine for what it really is, but don't compare it to a 50cc... you'll be disappointed. The BT 50 doesn't have the stroke (32mm) to effectively spin up 22" props with any degree of efficiency. But, put a 20" prop on it and you'll see where the engine really shines.

Don't misunderstand me here, I like the Fuji BT-50 EIS. It really performs well as compared to other 46cc engines, and it is the smoothest single cylinder engine I've tested in my 37 years of RC Modeling. Just tell it like it is...

blw

My Feedback: (3)

Some manufacturers round up or down. Most do it, so that is the way it is. Same goes for calculating h.p. At least they give you the RPM where it was calculated. Some don't do that and just post a number. Just about all h.p. numbers are meaningless. I never pay attention to them.

mfuess

I understand the "rounding" part blw.

But rounding from 46.5 to 50 isn't even remotely reasonable by any mathematical standard. Even "fuzzy Logic" won't bring you up to 50. Virtually all engine makers will round to the nearest cc, not to the nearest 10 of cc's. I totally agree with your thinking on horsepower. Unless every engine maker uses an SAE certified dynamometer, HP ratings are totally pointless. However, you do get some degree of "relative" data.

There's no doubt that Fuji makes a nice engine. But I was really expecting my BT-50 EIS to perform like a genuine 50cc engine. It won't do it. The engine just doesn't have the displacement (or stroke) to manage 22" props with any degree of efficiency. But with a 20" prop the BT-50 does fairly well, and it really screams with a 18x12. That's the nature of the engine, it likes to tach up as suggested by the 32mm stroke.

I also like the fact that Fuji does go to the trouble to balance (as well as can be expected) their single cylinder engines. This really makes a difference. This is a very nice engine, but in no way I will use it in place of a true 50cc engine. It just can't generate the torque.

Frankie b

Good information that on the Fuji 50 mfuess. Base on that i should expect not more than a 18x8 or 18x10 prop for the Fuji 43 EIS on a project i'm finishing. Any experience or info on this? I'll apreciate any help on the subject.

Frankie

Tired Old Man

My Feedback: (1)

Nice job on providing all the tawdry details on the Fuji "50".

In your discoveries you have hit on every reason I would not buy or suggest one of these engines, regardless of how well it ran. The advertising is all about stretching the facts and misrepresentation. Had they told it like it was in the beginning they would have had higher sales. Most people know when they are hearing B.S. and choose another product when it gets too deep.

Even better job in rotating the cylinder. Few would have thought of it, while fewer still would have attempted doing it. I'm very pleased you found the effort successful.

mfuess

Frankie,

The 43 EIS is a nice engine! I have run a few with little or no problems. It is exactly what it claims to be, 42.5cc. It weighs the same as the BT-50. It slings an 18x10 prop with good power. I will tell you this, Fuji's EIS isn't anything to write home about. My EIS ignition has given me problems from day one. So I switched it to RCEXL and my ignition problems went away. So far I have replaced the ignition, and rotated the jug. That's a lot of trouble for a brand new engine that won't even swing 22" lumber. I finally got the engine mounted in my RV-4 yesterday. I hope I don't regret it.

Frankie b

Thanks mfuess, one more question, do you run the EI on 4.8 volts or 6 volts can be used?

Frankie

mfuess

It will run on 4.8, but I have been using 6.0.

Tired Old Man

My Feedback: (1)

The RC XL is rated for both 4.8 and 6v. You should be happy with the performance. There's nothing wrong with the engine that isn't correctable with a good ignition system, muffler, and the right prop. Going on a diet would help a bit more but it's not worth the effort or expense.

mfuess

Hey Pat,

Yes the RCEXL will run on 4.8 just fine, I just happen to have a spare 6.0 VDC 4000 Mah battery I'm breaking the engine in with. I have a 1 gallon tank hooked up, that I'm using for break-in. So I figured I needed the big amp battery to hold up to the gas supply. I'm running my BT-50 right now...

I did discover that a Zenoah G62 exhaust pattern is the same (except for bolt size) so I am using a G62 Pitts muffler instead of the steel factory muffler. It's a bit on the loud side but at least I know when it dies.

Frankie b

Excuse me mfuess, i did wrong. I was trying to ask about using 6 volts on the Fuji OEM ignition. Again, sorry about my wrong question.

Frankie

mfuess

Yes, the Fuji ignition will run on 6.0 VDC.

mfuess

Here is the BT-50 sitting in my Great Planes RV-4. It fits good but the stock muffler had to go. I found that a Bennett muffler for a Zenoah G62 is a perfect match.



The RV-4 should move right along having 19 pounds of thrust in a 14 pound aircraft. I ran 3/4 gallon of gas through it on the bench so it should be ready to fly.

mfuess

I maidened the RV-4/Fuji 50 yesterday. One word says it all... DOG. I used the recommended props and it's still a DOG, DOG, DOG. It sounded OK. I flew for a total of 30 minutes and it was nothing less than disappointing. My RV didn't have any more thrust, didn't have any more speed, it didn't have any more anything than the Evolution 26 GT I replaced with this POS.

mfuess

The FUJI BT-50 has been replaced with a DA-50... I know the DA will do the job.

larry@coyotenet

My Feedback: (21)

My fuji 50 flys my TFp-47 well at 22LBS and 5,000 feet. I think part of your problem is that grey thing on the front of the plane. APC props in the larger size are well known to have rpm up the ying yang and not enough pull to fly the plane. Should try another brand first. I have several of the APCs and don't even attempt to use them on a 20LB plane.

Larry

mfuess

Thanks for the info Larry. But the Fuji is off the RV-4 and replaced with a DA-50. The DA simply screams!

On the next Fuji install I will try your advise on props!

Thanks again Larry!

mfuess

OK, here's the scoop on my Fuji BT-50 IES.

Needless to say it was a very disappointing engine for performance. But I wasn't willing to shelf an brand new engine so I thoroughly inspected it. What I found was, the Fuji ignition timing was set to "0" degrees at FULL ADVANCE! This is totally unacceptable! SO, I removed the EIS and installed an RCEXL with an adjustable timing ring. I set the full advance to +28 degrees.

The Fuji fired up on the FIRST Flip (probably luck). The engine sounded great. After it warmed up a bit I slammed the throttle to wide open and the little Fuji instantly spooled up to peak RPM. I GAINED over 2000 RPM over the EIS ignition!

I can't tell you if Fuji "intended" to have their timing set at ZERO or not. But I can tell you that if the timing is set to +28 degrees, it's a whole lot better performing engine. I finally got around to putting a tach on it, and an APC 18x8 Wide blade was hitting 9150 RPM. I switched to an 18x10 and its getting 8100. Today I'll move up to a 20x8 and later a 22x8.

The bottom line is, a Fuji BT-50 (46cc) has good potential if you're willing to mess with it. I also rotated the jug so the exhaust is on the "CORRECT" side, like other 50cc engines.

Bax

My Feedback: (11)

A couple of things:

1) We'd consider installing a 50 cc engine on the Great Planes RV-4 an unsafe move. The airframe is simply not designed to support that size of engine. The airplane is intended to have an all-up, ready-to-fly weight of 9-1/2 to 10-1/2 pounds. The airplane is intended to take engines of .61-.91 size, or 10-15 cc. By the time you shoehorned a 50 cc. engine into that airplane, we'd not be surprised at all that performance had not changed. The greater power would have been offset by the greater weight the airframe had to carry. A bigger engine doesn't always translate into more performance.

2) The zero degrees of timing would be at idle. It would not be at full throttle. If the full-throttle timing was at zero degrees, then that would make the idle timing something like -38 degrees or so. The engine could not possibly start at that timing. We'd look askance at how the timing was measured to get 0 degrees at full throttle.

mfuess

Mr. Bax,

(1) The BT-50 was too much of a dog (at that time) so it was replaced with a DA-50. My RV-4 has 88 flights on it and the last 37 of them with the DA-50. The airframe is rock solid. Yes, I did make many structural upgrades to the RV-4 to accommotate a gas engine. My RV-4 flies absolutely beautiful and it weighs just under 14 pounds.

(2) Regarding spark advance: There really isn't any advance by true definition, as it's actually spark retard. The magnet and sensor are in a fixed position relative to one another, which does not, nor cannot change. The ignition signal fires when the sensor field (Hall Effect IC) collapses. So, the only change that can possibly take place is to delay the collapsed signal as the magnet exits the edge of the Hall Effect IC. The variable (retarded) time delay is dictated by impulse frequency (IE: RPM). When an engine is not running, there is no frequency (IE:RPM), thus there's no timing retard until it "sees" rapid repitition. So in essence when you trigger the sensor by passing the timing magnet past the Hall Effect IC you are seeing full advance until rapid repitition occurs; In other words, the time delay is not activated until it "sees" pratical RPM, approximately 600 RPM or ten pulses per second. The time delay is directly proportional to frequency, or RPM (if you like) up to about 4000 RPM or 66.6 pulses per second.

I use a HELIX 360 Degree Wheel on the prop hub, a Starrett 50 millionths test indicator to locate true TDC, and a Tektronics 100Mhz Dual Trace Ocilloscope to indicate actual field collapse within the sensor (Hall Effect IC) and a KV Inductor Clamp on the plugwire indicating actual spark. You absolutely can not get any more accurate than this...

I appreciate your concerns, I really do. But I've been successfully gas modeling for over 36 years and I'm no stranger to Internal Combustion technology.

mfuess

Hey Larry,

Now that I have the Fuji 50 running "like its supposed to", I'll try some wood props. I wasn't about to give up my DA-50 in the RV-4 so I put the Fuji in my Goldberg Pitts Monster. My Monster has had a lot of engines in it, G38, Brillelli 46, DA-50, and a Venom 45. And now it's Fuji time... I'll try a Pro Zinger 18x10 first, then move on from there. My little Fuji is turning the Zinger at a solid 8300 RPM, that ought to get it airborne.

larry@coyotenet

My Feedback: (21)

Glad to see that you found the problem, I really couldn't see why the Fuji would be that big a dog. I have been flying mine with a TF or Zinger 20x8 prop but will be trying a 20x6x10 next. I have had really good luck flying a TF 47 with a g-62 and a Zinger 20x8x14 prop.
At our Warbirds meet last week several of the pilots would not believe that my plane had a G-62 with that old crappy Zinger. Performance is at least equal to, if not better than a Menz 22x8 and very similar to a Mejelik carbon fiber 20x10 prop. Please remember that this is a warbird, not 3d !. I have found that I like my warbirds better if I fly them with a shorter, higher pitch prop. Takeoff is not as fast and I do have to start with a shallow dive to let the engine unload but from there on Katie bar the door!

Larry

mfuess

Hi Larry,

I'm glad my BT50 is up to par now... it's not a cheap engine! This afternoon I walked out to the shop, turned on the ignition and 2 flips later it was purring. Another thing I like about the Fuji is how smooth it is for a single cylinder engine! Tomorrow it gets a real high-G work-out in the Pitts Monster. I'll quickly find out which props it likes and which ones it doesn't.

We just had our WARBIRD Event at Greater Southwest Areo Modelers about a week ago! Man ho man, were there some beautiful warbirds! I really love warbirds, but I get sort of bored flying them. That's why I go for the grossly over-powered bipes... It keeps the ol' blood flowing...

[link=http://www.flygsw.org/cgi-bin/yabb2/YaBB.pl?num=1188742313]GSW Warbird Flyin[/link]

mfuess

Here's the "flying" scoop on my BT50;

I took it out for 3 fairly long flights today, a total of about 1 hour and 15 minutes actual flight time. The BT-50 ran flawless. Not a single burp or four-cycling during any of the flights. I pushed it very HARD, taching 8500 RPM on the ground and I did several full throttle dives from about 500 ft or so. Then I began doing multiple high G maneuvers using LOTS of throttle management. The Fuji just purred.

I figured the Fuji would land smoking hot after all the high stress maneuvers I did. But it was a mere 235 degrees! I gased her up and took off again. This time I performed multiple vertical torque rolls over and over again and an occational harrier roll. The Fuji held its own not giving up a speck of power and kept cool the whole time. My finally for the day was a FULL THROTTLE blender from about 600 feet or so. The Fuji hung in there all the way down to level-off and didn't sputter a single time.

OK I'm very happy with the Fuji BT-50 now, but consider what it took to make it the engine it should have been all along.

thevirginian

mfuess,
I owned a BT50 as well as a still own a 43, which is installed in my GP Ultimate. I fly this set up for almost two years now and know I am a little underpowered. A strong 46 would do much better, I guess. But the one thing I can honestly say is that the Fuji never let me down. It always fired up by hand and still runs flawlessly. REcently I changed to a Brisson muffler and noticed a slight increase in power. Would I buy that engine again? Probably not, because since I purchased this motor there are a lot more choices in this class, now. I can buy a Brillelli for less and have a stronger motor. The quality of the Fuji is certainly very good. The Bt 50 was a rather disapointment. But even that motor was running O.K. Can't compare it with a DA50, for crying out loud.