MVVS 1.6 Gas Engine and Bisson Muffler

 

I purchased this engine as my entry into the world of gasoline engines. I had read a favorable review of the MVVS 2.15 in R/C Excellence and tracked a few positive threads on the R/C Billboards and News Groups. The engine was not available for purchase in the US, so I looked abroad for it. I found the engine in stock at French distributor Topmodel. The total price including shipping was 303 Euro, which billed out to $275.00 on my credit card. I placed the order on 12/15/01 and received the package on 12/29/01.

Upon receipt of the package, I noticed that it had not been packaged well for it's long journey. The problem is with the MVVS box and not that of the distributor's exterior packaging. There is very little packaging inside the yellow MVVS box. This resulted in a dented ignition module and the spark plug being driven completely through the inner box. It must have taken a very hard knock. While not happy with this abuse, I did confirm that everything was working correctly and kept it. I wrote Topmodel and suggested improved packaging.

The quality of the engine was excellent. All castings and machining was clean and free of burrs or flashing. It is quite light and included a small steel muffler. Topmodel included instructions in French and English. I personally found the English instructions to be sparse. If you have run other gasoline engines you will have no problem. This, however, was my first gasser so I had questions about needle settings, break-in, fuel mix, etc. Topmodel has about a 2-day turn around in answering technical questions. For more detailed support, I contacted Pe' Reivers of MVVS in the Netherlands. I had read many of Pe's posts on the news group and considered him to be quite the engine guru. He quickly and patiently answered all of my questions in detail.

Per Pe's recommendation, I added a ground strap to the ignition system before running. Pe' includes a custom switch harness with his engines that includes the ground strap. Topmodel does not include the switch harness so I made my own from a regular Futaba "J" switch harness and charging jack.

Once securely mounted on a test stand, I affixed an APC 16x8 propeller. The manual does not recommend this small of a prop for use in flying. They recommend a minimum of 16x10, but I would be running it static and was advised to prop-down. The first start took place on a chilly afternoon at a temperature of 30 degrees F. I used a 32:1 mix of Lawnboy Ashless oil. This is a petroleum-based lubricant that was selected to hasten the seating of the ring. I got this advice from the BME engines website. Note that the manual recommends a 40:1 mix of "2-stroke racing oil."

The engine started on the first flip after priming. Well, honestly, it was about the tenth flip because yours truly, "Mr. Glow", forgot to turn on the ignition! With the ignition on it fired right up. It would not idle, but would run well at 1/3 throttle and higher. I ran it a total of three minutes before shutting it down. It was hot despite the cool weather. I was convinced that my needles were not set correctly so I contacted Pe' before I ran it again. Pe' recommended a starting needle position of 1.5 turns out on both needles and also supplied techniques for correctly setting the needles (see below). My next running session was excellent with a stable idle, good transition, and clean top-end being achieved. The engine was initially run in short periods and allowed to cool between runs. Eventually I was running it for ten minutes at a time. The engine exhibited no signs of overheating.

 

Engine Weights

All measurements were taken with a digital fish scale. The resolution is one ounce. Accuracy is unknown.

 

Bare Engine: 32-oz.

Engine + Ignition: 35-oz.

Engine + Ignition + Stock Muffler: 38-oz.

Engine + Ignition + Bisson #5516 Muffler: 38-oz.

Engine + Ignition + Bisson Muffler + Ignition Battery: 42-oz.

 

Performance Metrics

(5/19/02) To date I have run approximately 2/3 of a gallon of fuel through the engine. I have recorded the following data:

Propeller: APC 16x8
Muffler: Stock
Fuel Mix: 32:1 Lawnboy Ashless
Idle: 1800 rpm reliably sustained.
Max RPM: 8200 rpm

 

Propeller: APC 17x8
Muffler: Stock
Fuel Mix: 32:1 Lawnboy Ashless
Idle: 1600 rpm reliably sustained.
Max RPM: 7500 rpm

 

Propeller: APC 17x8
Muffler: Bisson #5516
Fuel Mix: 32:1 Lawnboy Ashless
Idle: 1600 rpm reliably sustained.
Max RPM: 7900 rpm (Note: 400 rpm increase over stock muffler!)

 

Propeller: 3W 18x8 (Menz S clone)
Muffler: Bisson #5516
Fuel Mix: 32:1 Lawnboy Ashless
Idle: 1600 rpm
Max RPM: 7300 rpm

 

Comments:

  1. The stock muffler leaks around the seams. It is easily removed and disassembled. I sealed the seams with a high-temp RTV.
  2. During the course of running the engine, I noticed a drop of oil around the spark plug. After further examination, I discovered a minute compression leak around the plug. This is a result of the cylinder head/ignition shield bottom/sparkplug sandwich. The plug centers and compresses the ignition shield bottom against the head. I cleaned up the parts and it seemed to minimize the leak. It is primarily a static phenomenon noticeable by putting a drop of oil at the plug base and slowly turning the prop to reveal bubbles. I can't say that this leak is significant or that it is hurting performance. Topmodel sent me an email fragment from MVVS stating that the compression will stabilize with further running. In the mean time Pe' Reivers states:

    3. "before re-inserting the plug in a new engine, take care that the lower ignition shielding half, which is clamped between the plug and the head, is absolutely clean, and free of all plating! That is what caused your compression leak in the first place. We will clean up the part on all engines we ship. MVVS should not have plated it at all, and keep it in bare brass."

    I have done the clean up of the parts and as of my last test session did not notice any oil around the plug. The situation may be resolving itself.

  3. A number of sites/threads have indicated that the stock muffler is restrictive and limits top-end power. I believe this to be correct. I was originally going to braze a custom header for the engine and use a Krumshied (KS) baffled muffler. Unfortunately, I was left "baffled" by how to mount the system! I could not devise anything elegant, so I ordered a horizontal "Pitts" style muffler from Bisson Custom Mufflers. The part number is #5516. The combination of the MVVS and Bisson muffler results in a very clean installation in my Hanger 9 CAP 232. Note that Bisson also manufactures a muffler for the inverted mounting of this engine. Bisson now has a great website with online ordering!
  4. If you have an application where you might need a custom header, the KS header flange for the Moki 1.8 will work fine with a little modification. (5/20/02) Update: I have heard that the header for the ZDZ 40 is a perfect fit. You will need to widen the spacing of the mounting holes to fit the MVVS. A call to KS may also be in order. Their website does not mention a flange for the MVVS, but few manufacturers keep their sites up to date. Note that KS will not answer emails. This is why I recommend calling them. They do speak English quite well. I will be using my KS components on my Moki-powered Giant Su-Do-Khoi.
  5. (5/20/02) TopModel sent me a new cylinder head after I complained about the seepage around the spark plug. It took two months, but they sent me a new cylinder head for free! I finally tried installing it, but could not get a good head seal. There is no head gasket to compress, it just gets jammed against the top of the sleeve. If there is a trick to mounting a new head, I did not find it. I re-installed the original. The new head does have a visibly different machined seat for the plug and shield that supposedly alleviates the seepage. Unfortunately, I was unable to test this new part.

Summary:

So far the engine has been a fun mil to play with on the test stand. I really get a kick out of giving it a flip and have it settle into a nice low idle. I am looking forward to flying it. The top end power isn't staggering, but this can probably be attributed to the stock muffler. I look forward to further testing with the Bisson muffler and a variety of props. There is ample performance data on various MVVS distributor sites. I have no reason to discount their claims. However, I will only report the data that I get from my motor. This will provide you with additional data points.

Purchasing the engine from Topmodel was a calculated risk on my part. It was my first International order. The price was excellent, and the order was processed and shipped with great dispatch. Topmodel will confirm final pricing as well as ship date via email. I was pleased with this. Unfortunately, the packaging was flawed and led to damage. The English instructions are sparse for a gas engine novice.

As you can probably guess from my web pages, I believe in sharing information. One of my supervisors once told me that pioneers are "people with arrows in their butts." It is my hope that by sharing information we can avoid this painful condition. If you have some experiences, tips, or tricks that you would like to share please drop me a line at this link.

 

Links for MVVS distributors:


Pe' Reivers Website: http://www.reivers.myweb.nl/ (Recommended for custom switch harness, ignition manual, detailed email support)

Just Engines Website: http://www.justengines.unseen.org/ (I have no experience with this UK firm, but they are sure to speak English!)

Topmodel website: http://www.topmodel.fr/ (Great pricing, good stock, fast shipping. Poor packaging, sparse English instructions)

 

Carburetor Tuning Instructions:

These instructions are courtesy of Pe' Reivers:

"Both needles should be about one and a half turn open to start with. You will then be about right for standard running. Then, using the arm stop screw, set the idle to fairly fast. Using the low needle (closest to the throttle valve), find the highest idle running setting, then open the needle 1/4 turn more. The top end is next, and should be set slightly richer than the highest rpm setting by 1/8th of a turn. Repeat the procedure until satisfied. Beware: both needles influence the whole range on many Walbro carbs, and idle speed has to be adjusted in between to avoid too high an idle. For a bit more power, drill out the carby to 8mm choke diameter. Latest test data: Keep the fuel mixture after the run-in at about 1:40. You will have more power available."

Installing the MVVS 1.6 and Bisson muffler on a Hanger 9 CAP 232

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