Manufacturer C.M.B. Country Italy Type 21 EVO 2 BUGGY SSi DD

* factory supplied numbers

An Italian buggy engine from one of the famous world champion manufacturers of 3.5 cc boat engines.
With the knowledge of these boat engines C.M.B has manufactured a nice looking and good performing buggy engine.

I received the ordered engine from the German C.M.B distributor HS Micro Motor Service and the box with the engine was factory sealed with a label. When you buy an engine be sure that label is intact. If not, ask the shop owner to check the contents before buying it.

I broke the seal and looked into the box. The engine is again nicely packed in two plastic airtight bags so no debris can enter. One is with air bubbles. Further the user guide with instructions to maintain and break-inn of the engine this time in the English language! (Thanks Dieter)
*Also an explanation with drawings are there for the proper pipe length.
*A normal type 6 glowplug
*A boost bottle with tube and ty-wraps.
*A 7 m/m Picco style (OEM) carburator.
*And some stickers.

I first took all the papers out and read them carefully. (who isn't?!)
One paper is dedicated to:
*the engine break-inn and maintenance and engine setting.
*how many head shims are required.
*which glowplug to use in which condition.
*which fuel to use and most important the amount of oil required! In this case even the maximum and mixture between synthetic and risinus oil is provided.
*the correct length of the pipe.
*the warranty regulations.
Paper two is the parts/price list of the engine.

CMB claims that no debris will be left after manufacturing the engine and advises not to open the engine before you use it to prevent dirt to get into the engine.

A full normal ABC piston-liner is naturally used in this race engine. The sleeve is nicely chromed.
And here comes the difference between the older version "2000 DD" and this one "SSi DD" with the "Intelligent piston sleeve".
CMB has a patented system to manufacture the piston sleeve in such a manner that the thermal specifications make it less critical for break-inn and expands the lifetime of the piston sleeve.
Break-inn is reduced to a period of one tank of fuel running the car in rich setting on the track.
After this one tank of fuel the engine is ready for use the manual claims!!! The second tank of fuel you can set the engine for the correct setting without abusing the engine and its lifetime.
When the engine is just started it might sound a little crunchy. But when it is warm (take the time a few laps will do fine) it will sound OK. Also when finished running, let the engine idle stationary for 30 seconds and then cut the engine. Place the piston in its lowest position. This will make starting an other time easier. Beside the new piston sleeve nothing has changed inside and outside the engine.

More features are the  C.M.B Multi Exhaust System "MES". The system speeds up the gasses leaving the exhaust and fills it with fresh fuel mixture. Beside the 5+1 ports in the liner there are two extra ports in the piston. They are working together with the "MES" ports to provide more power and better fuel economy.

The engine is a short stroke one and the cranckshaft measures 13 m/m. It has two carved TURBO cutouts at the end near the cranck pin (bigend). This is to better the fuel flow to the combustion chamber.

The crankcase of this engine is nicely finished. Two extra ribs at the bottom are making it stronger.

A purple tapered cooling head makes it looks nice and also efficient for the right amount of cooling without making it too heavy. The cooling head is constructed with a head insert that accepts normal glow plugs only.

A 90 degree boost nipple is located at the right side of the engine.

The carburator is one manufactured by Picco for CMB. It is a 7 m/m version.
Take care with the high speed needle housing when you want to change the angle of the fuel nipple.
Do not use excessive force and turn left to loosen the needle housing!!!!

A rubber shielded NMB bearing is sealing the front. A large main bearing does its job inside.

The purple boost bottle that comes with this engine is not build inside the rear cover plate but is an external one. This is to prevent the bottle to become the same temperature as the engine. The bottle needs to be placed somewhere on the rear stiffener bar. If boost bottles are useful in all cases is to be discussed. But it is standard so try and error will prove if it works on different tracks.

The claim of the working of boost bottles is to enhance the idling and pick up from low speed.
Also better fuel economy is an advantage that is described to the use of boost bottles.
Boost bottles do not boost the maximum power of the engine itself!

The first impression of this engine out of the box is OK. 
Parts and engine are nicely machined and assembled!
The manual is completely in English version.
The specs tell us it is a medium power engine. click here for the power/torque graphics
The real engine performance and fuel economy can not be judged by looking at it. So we will track test this engine and compare it with others and if possible dyno test it.

TWF8 rating **** stars

Paco Raap

The pictures below are those of the older 2000 DD the version with normal piston and sleeve. Also the carburator is the optional aluminum flat slide one for more info look here

	The box with the engine with a sealed label!
	The right side of the engine with the boost nipple
	The left side of the engine
	All mechanical parts of the engine
	The two slots "TURBO" cranckshaft and bigend
	The exhaust port with the two MES booster channels
	One of the booster ports and channel clearly visible
	The other side with the second extra booster port and channel
	The other of the 5 normal ports. Watch how low the center port is.
	The nice chromed layer inside the bronze sleeve
	The piston and the connecting rod with a bronze bushing.
	Watch the small cut out for easy removal of the piston pin retainer spring (good job)
	The crankcase inlet for the carburator and the old straight nipple for the boost bottle connection
	Those two screws need a little silicone sealing
	The high performance 8 m/m flat barrel slide carburator as option!
	The complete engine equipped here with the angled nipple and boost bottle

When no original C.M.B muffler is used the best options are Picco mufflers. Nova Rossi based mufflers do not give good performance in combination with C.M.B engines!

Comment by Paco Raap 30-12-2000:

The manual was already warning for this and take care of it! If you mount the engine on the engine mounting blocks be sure that the bottom surface of the engine mounting blocks is flat. The engine mountings blocks of the Mugen (MBX serie) and Kyosho will have no problem. However the engine mountings blocks from Thunder Tiger are not straight at the inside and they conflict with the two extra ribs that are on the bottom of the crankcase, so flat mounting is not possible. Therefor remove some material (the marked triangle) at the marked spot of the engine mounting blocks. If the engine is mounted check if the ribs are not touching the inside of the mounting blocks anymore.

Performance:

Comment by paco Raap 04-08-2001:

First test day.

I ordered an engine at CMB Germany without carburator! I placed an 8 m/m R&B carburator on the engine. This one fits not without a simple modification. At the lower part of the throat of the R&B carburator there is a small groove with an o-ring. I removed the o-ring and toke a knife to cut away the part beyond that groove. This way the throat is shorter and will fit nicely in the engine. Make sure to seal the carburator with silicone sealant where the carburator body touches the crankcase. I fitted the engine on the engine mounts and made sure they were flat (check this on a piece of glass). I bolted the engine in the car an went to the track.
Filled the fuel tank and started it and it came to life directly. Checked the setting of the carburator if it was rich enough and rolled the car on the track. Running the car with low and high revs but the high revs not longer then one second.
After the first tank of fuel I filled the second one and set the carburator for an 80% optimum setting.
Still in my mind this was much to quick for engine break-inn. But I did what the manual stated and the third load of fuel was a 95% setting.
The engine did not got warmer as 75 degrees Celsius on the head and 107 degrees  Celsius on the glow plug. So this new "intelligent piston sleeve and thermal specifications seems to do their job perfectly!
The engine now runs at idle very stable. Settings with this R&B carburator can be found easily. The engine when cold sounds a little crunchy like predicted in the manual but after a few laps when the engine reaches its working temperature it starts to sound healthy. I did not checked the fuel economy. That will be done in later test and certainly when the TWF8 dyno is ready.

You can talk a lot about power where and when. Bottom or top and compare it to other engines but without real dyno testing and graphs nothing can be said and is purely personal feeling. I can only say that the engine has enough power for real racing. A smooth power band and compared to the CMB 2000 LSi has a better drive ability on our small low resistance test track in Purmerend.

Paco

The new style CMB carburator is an OEM product and is made by Picco. There are two things to take care of! * first is when you want to rotate the fuel nipple on the high speed needle housing for better alignment. Take a 7 m/m wrench and turn it anti clockwise gently!! * when the high speed needle housing is removed check for thread blur on the aluminum body part. If it is there (see red arrow) take a 8 m/m drill bit and slowly rotate it one turn to remove the blur.  Do this with the carb upside down so no metal debris will fall into the carb housing!! This blur can cause a fuel leak as the washer that will be on top of it is not sealing perfectly between the aluminum body and the high speed needle housing.

Second and Third test day.

On Saturday 25-08-2001 it was hot and humid 95% and the engine still ran cool <100 Degrees Celsius.
Sunday 26-08-2001 with lower outside temps and humidity the engine also ran cooler @ 80-90 degrees Celsius.

Both days the engine ran smooth and reacted OK on the changes made with the needles. It now has done more then 3 liters and the compression is OK. We will go further with durability testing this engine.
Paco

We write 13-06-2002
We ran the engine for more then 10 liters of fuel now and it never missed a beat! Compression still good! We will go further with testing.
Just remember to let the engine come to working temperature  for final tuning. These engines sound rich when they are cool! So take care not to lean it when it is still cold as this may result in a failure due to a to lean mixture.
Paco

We write 25-06-2003.
Sofar the engine has done over 25 liters of fuel. Even an ONE HOUR NON STOP race it did with out any problem.
Compression still OK. Ill keep you informed. Paco

We write 09-09-2003.
After 30 liters of fuel the engine began to make a terrible sound on the straight. After two blown plugs I opened the engine and found the main bearing broken. The piston and sleeve are still in good shape and provide through the intelligent piston system still enough compression. We are going to renew the main and front bearing. The big end has a little play but not enough to say that a rebuild is not worth it anymore. Paco

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