Fuji-Imvac 86cc Twin Review

by Roger Smith

For twenty plus years, giant scale modelers have been facing the challenge of finding reliable large powerplants for their models. In years past we have seen everything from converted weed whackers to homemade nitro burning monsters, that were unreliable at best, bolted on the front of expensive model airplanes. Large scale modelers continued through the years looking for a trustworthy company that they could depend on being there when they needed repairs or warranty work.

Fuji says their engine line is "Dedicated to the modeler - Designed without compromise." We first saw the Fuji BT-32A single (32cc) , BT-50SA single (50cc) and BT-86 (86cc) twin at the Chicago, R.C.H.T.A. trade show in September, 2001. They are really nice looking with blue cylinders and precision machined aluminum cases.

Every Fuji engine also comes with an electronic "ATM" (Automatic Timing Module) that allows easy starting and optimum top end performance. This ignition module was invented by Seiji Tanabe, company founder and an avid giant scale modeler and long time user of gasoline powerplants in aircraft. This ignition system, working along with the compression relief valves that are already installed in both cylinders, simplifies starting. The inclusion of the ATM system also eliminates the need to search out your own electronic ignition system that may or may not work correctly. Unlike some add on ignitions systems, the ATM system is designed specifically for Fuji engines.

Kevin Morris, the Product Manager for Fuji at Great Planes gave us these details.

"Fuji IMVAC is a company which is based in Japan. This company deals in very high tech applications, precision valves and laser beam technology, among others. High zoot rocket scientist type stuff. They have been in business since 1979. Mr Seiji Tanabe, who started the company, also happens to be an avid airplane modeler. Mr. Tanabe, after experiencing some frustrations with the available gasoline engines in Japan, decided to produce his own engine for use in his airplanes. Thus the Fuji Engine line was born.

Those modelers who are familiar with the Mustang 50 are already aware of the high quality and craftsmanship which has gone into the design of the Fuji engine lineup, though they may be surprised to hear so. The Mustang 50 was designed and produced for Byron by Fuji Engines. The Mustang 50 engines are still flown today by many modelers, and through several design refinements, the Mustang 50 has been reincarnated as the BT-50SA. The BT-50SA is a powerful performer with a strong heritage. Along with the BT-50SA, the BT32A and BT86 Twin have a solid following in Japan. We anticipate that the line will garner as much attention in the US.

According to Mr. Tanabe, the major source of his heartache in the past was the lack of reliability, and subsequent lack of support and parts, of the available gasoline engines prior to Fuji. As a result, the primary goal of Fuji Engines is to produce an engine which gives reliable starting characteristics, is long lasting, and requires little maintenance. The quality engines also must be backed by a quality support package.

All Fuji Engines sold in the US come with a 3 year warranty, and are serviced here in the States. Mr. Tanabe has made several trips to the service center in the US in order to ensure that the tradition of quality service will continue in the US. Overall, we are very excited to be working with Mr. Tanabe and Fuji, and modelers can expect a high quality engine, with service to match."

The fact that Fuji has been in business over 20 years is a good sign but we really like the fact that all their engines are protected by a 3 year warranty. It's also a plus that Fuji will be around if and when we may need to use that protection. Too many other large scale engine companies have come and gone, leaving modelers holding products with no support.

Other features of the now available Fuji engine line we found interesting include -

* ABC construction
* CNC machined parts
* Ball bearing supported crankshafts
* Linkages designed for R/C only applications and mufflers designed especially for Fuji engines
* Firewall mounting systems designed for easy installation
* Heat resistant paint on the cylinder heads
* A Champion resistor plug included with the engine
* Optional propeller hubs that extend or reduce prop shaft length to improve cowl clearances
* Available spring starters and available smoke muffler

We were able to test run the Fuji BT-86 twin. The twin came with a Walbro 186 carb that featured a spring loaded control arm plus a heat shield that seemed to improve the starting reliability. It also had an overflow /relief valve that is designed to remove any excess fuel that is built up with the engine idles for long periods of time.

Before we mounted the engine we sent it to Tru Turn Spinners so we could use one of their spinners and adaptor unit. The Fuji was so new that Bob Obenberger asked if we could send it to their South Houston facility. Once there it was gone over, measured and sent back with the appropriate pre-drilled spinner bolt* and one of their beautiful 4" P-51 shaped bar stock spinners.

* An interesting fact that we discovered once we received all the Fuji engine literature is that they too offer an accessory spinner bolt designed especially for Tru Turn spinners. This is a great sign. It shows that Fuji really designed their engines for our use. They even thought of offering a part that allows us to use a specific spinner.

After mounting the BT-86 we filled our 24 oz. tank with a mixture of 40:1 Yamalube and gas. Three flips and the engine was running and the compression relief valves automatically closed when the engine started.

The twin was broken in per the manufacturer's suggestion. Fuji recommends that you run a new engine using break-in fuel at a mixture ratio of 25:1 with gasoline. Once the mix is blended, they suggest you run for one full hour with this break in formula. We are happy to report that during our test running and break-in period, the Fuji is a very friendly powerplant with no bad habits. Because it was late November in Michigan, our test was limited to the easy break-in of this twin powerhouse. And when we say powerhouse, we mean it!

At only 6.2 lbs, with the mufflers and CDI ignition attached, it is one of the lightest most powerful motors we have ever run. Transition from idle to open throttle was seamless due in a great part to the ATM CDI ignition system.

Turning a 24 x 12 prop we easily got the twin up to 6,400 rpms after 6 tanks of break in fuel. The engine was brought to that rpm range briefly but also easily. The combination of the 24 x 10 prop, Tru Turn spinner, Yamalube oil and Fuji engine seemed to be just about perfect for our needs. We can't wait to install this twin into an aerobatic model when spring arrives in this area.

In the future we hope to travel to the Fuji production facility in Japan to do a more in depth review of their company, history and plans.

Specifications Fuji BT-86 twin
Displacement: 86 cc
Bore: 30mm Stroke: 42.7mm
Horse Power: 7.5 HP / 9,000 rpm
RPM: 1,100 to 9,000 rpm
Ignition Style: CDI Ignition
Weight: 6.2 lbs
Spark Plug: Champion RCJ-6Y or 7Y, gap of 0.6mm (.025")
Propeller Bolt: M10x1.75
Magneto Gap: .5mm(.02")
Overall Length: From back of prop to start shaft end: 7.75"
Width: 8.6"
Overall height: 8"
Length: From back of mount to prop nut: 6.3"
Ht: from crank to top of engine: 3"
Break-In Fuel: 25:1 mixed gasoline (run for one hour with this mix)
Fuel: 40:1 mixed gasoline (40 parts gasoline/1 part 2-cycle oil)
RPM Range: 1,100 - 9,000
Weight: 6.2 lbs.
Ignition: CDI w/ATM

Jan/Feb 2002 R/C Excellence