Hi.
I am about to buy one BF-34EI 34cc 4-Stroke engine but i can't find any information about the thrust
and pitch speed of the engine with the recommended props (22x10).
I plan to use it on a 25 lbs Cessna, i know it does not look adequate but long flight times is what i am after
and not aerobatics. All i need is 20 degree climbouts and gentle stable flight but without those thrust figures i can't decide to finally
buy it.
Any info is welcomed.
Thanks
Chris

Dear Chris,

I own a BT43cc EIS engine purchased from Tower Hobbies earlier this year. I did so without sufficient research into the engine. When I did accomplish the research, I found that the consensus of many owners of Fuji-Imvac engines agreed that the engines, regardless of size, considered the engines to be heavy, and the electronic ignition systems to be weak and prone to generating interference with the R/C systems.

I intend to power an Ultimate Bipe with my 43cc engine, and, of course, I expect it to provide a thrust in excess of of the gross weight of the airplane, which is around 16 pounds. I have, I hope, solved the ignition interference problem by replacing the stock ignition with a fullyshielded system sold as "RCExcel", which utilizes full shielding of the HT wire to the spark plug with flexible metal "armor".

I have also, since purchasing the Fuji, also purchased three of the DLE Chinese engines: the 55cc, 30cc, and lastly the 20cc. These engines get good reviews - all except for engine life - which is yet to be determined.

Since you are powering a Cessna weighing 25 lbs., I would expect that your Fuji-Imvac would give you very "scale-like" performance. Sorry I cannot provide you with thrust numbers. Have you tried to email the guy in charge of American Distribution? The people at Hobbico (read that Tower Hobbies) keep one man continuously emplyed just to answer your type of questions.

Some good news! I found the manual for the engine on the Tower "Reference the Manufacturer" site. It's not hard to find in the Tower on-line catalog. Here's a quote that should cheer you up:
<font face="Helvetica" size="2"><font face="Helvetica" size="2"><p align="left">"During our tests, our Fuji-Imvac BT-34EIS turned a Bolly 18" x 12" carbon prop at 7100 rpm</p><p align="left">which translates to roughly 30 lb of static thrust.The engine was new with 60 minutes of</p><p align="left">breaking in. The test conditions were: Temperature 59°F [15°C], humidity 20%, elevation</p>

at sea level. Performance may vary depending on atmospheric conditions."
</p></font></font>
Best and Good Luck,

Brian Gray  -  jetmanr18

Hi.
I did found the manual with the exact wording but it is for the 2 stroke engine (3.2 HP)[]
If the engine can provide close to 18-20lb then it is enough.
I made some calculations in my mind like if the 3.2 HP engine can provide 30lbs then the 2 HP
should come close to 17 - 18 lbs
I also found in the BF-34EI's manual:
"20 x 6 Mejzlik Carbon Prop:
BF-25F: 1,400 – 6,600 RPM
BF-34F: 1,300 – 7,200 RPM
18 x 8 Bolly Carbon Prop:
BF-25F: 1,400 – 7,300 RPM
BF-34F: 1,300 – 7,800 RPM
Temperature for the above was 15°C, humidity was 20%. Engines were new, with
100 minutes of break-in running. "
Now 20x6 @ 7200 = 17.28 lbs static thrust and 19.64 lbs in flight which sounds realistic.
Thank you as your information about the manual at least provided me with a starting point
of what to expect.
Chris