I wouldn't be suprised. 4 strokes are still in the early stages of production. They are like automobile engines in the 50's and 60's. Things like fuel injection, duel overhead cam, variable valve timing and lighter matterials are some of things they might implement to get more power out of an engine.

Volumetric Efficiency -
- An 300cc engine means the volume of the cylinder(s) displaces 300 cubic centimeters of air. Unfortunatly only 50 to 75 percent of the cylinder gets filled durring the intake stroke. This means a 300cc engine really only displaces 150 or 200cc durring normal operation. Intake aerodynamics and valve timing are mostly the culprit. Scavaging is the desiered effect of the exhaust gasses leaving the cylinder fast enough to pull the intake charge into the cylinder. Since a two stroke has no valves it operates stricly on this principle. The engine must spin fast enough to create some velocity with the intake and exhaust. A Supercharger or Turbocharger can make the motor run at 100% volumetric Efficiency ( I.E. a 300cc engine is actually a 300cc engine ). In some cases you can exceed 100 VE and create a higher compression ratio.

I doubt we will see a twin cylinder 4 stroke or any of the things i mentioned above but it would be awsome.

Chris Picciotto
99 Scrambler 500

 

2 stroke engines in quads have two very important attributes...

1) They produce 1 power stroke per crank shaft revolution ( single cylinder ) as opposed to a 4 stroke that produces 1 power stroke for every 2 crank shaft revolutions.

2)They are light.

Those attributes are offset by faster cylinder wear and gas usage. If there was only some common ground. Maybe....

The Rotory engine in the Mazda RX-7 is a refined version of that middle ground. The Rotory engine was originaly designed as a supercharger for diesel engines years ago. The advantage of the rotory type supercharger was that there was much less wear. Some guy figured out that if you add a couple of spark plugs the supercharger can function as an engine by it self. It is difficult to explain the design but a single 300cc rotor engine would opperate almost like a 300cc triple cylinder 2 stroke that had a 3 plane crank ( A cylinder fires every 120 degrees of the crank shaft rotation ).

On the combustion stroke in a single cylinder 2 stroke, the expanding combustion gasses loose pushing power as the crank shaft reaches 120 degrees. This means that the piston has to travel 240 degrees on momentum while pushing the exhaust gas and unburned fuel out.

On the combustion stroke in a 2 cylinder 2 stroke, the expanding gasses loose pushing power as the crank shaft reaches 120 degrees but then the the other cylinder fires at 180 degrees. This means there is only 60 degrees of just momentum as the other cylinder assists.

On the combustion stroke in a 3 cylinder 2 stroke, the expanding gasses loose pushing power as the crank shaft reaches 120 degrees then the next cylinder fires. There is no engine free wheeling so to speak. This makes a tripple have exellent power potentional if you compared the 1, 2 and 3 cylinder engines of the same displacement ( I.E. 1 300cc cylinder = 300cc, 2 150cc Cylinders = 300cc or 3 100cc Cylinders = 300cc ).

The only problem with this is that doubling or trippling the cylinders mean doubling or trippling the parts. Size and cost will slow you right down.

As i said before a 300cc single rotor engine would act like a tripple cylinder 2 stroke but it gets better. A 300cc Rotory engine would have only one cylinder, one rotor and no connecting rod. This means less parts ( don't forget exhaust pipes and carburetors )and it would take up only 50 to 75 percent of the space needed for a tripple .

Even better is that there is far less cylinder wear than a 2 stroke ( you would have to see a cut-a-way view to understand )

Rotory engines are not popular engine design for most cars is because like a 2 stroke they don't produce a lot of torque that is required to overcome starting and rolling frictions which greaten as the weight of the vehicle increases. This is one of the reasons why you will never see a 4 stroke weed wacker or a 2 stroke Amtrak engine. A quad however is light enough to take advantage of 2 stroke like technology.

For the Most part most people don't have the resources to tackle this type of a project and i don't think Mazda even wan't to bother so forget about it.

I never used to be a fan of the Rotory engine design but i was a believer when i met a guy down at a race track who had an RX-7 that produced about 1000 HP. The car was small and has a small engine bay so i knew there was no Chevy 454 or something in there. He ran a low 9 second quarter mile with this thing. I was studing engine theory in school at the time and i did a little Rotory engine research on side.

Chris Picciotto
99 Scrambler 500

 

Watch out what u say. Honda has some new 4-strokes that could be on "weed wacker" of the future, if they arn't aready.

 

Ryobi makes a 4 stroke weed wacker for use in California

 

The reason Mazda discontinued the RX 7, was because the Rotary Engine could not meet the government emissions standards. It is similar to the two stroke, were tons of unburned fuel is expelled out the end of the pipe. Rotary and 2 Strokes have a lot of plus's, but they are not very efficient engines.

 

no, they are not very efficient engines, but they sure are fun. i feel bad for you people in cali. i love my 2 stroke. of coarse, i never owned a 4 stroke so i don't know if i would like them. i like the snappiness and the arm pulling speed of 2 strokes. i can't wait to modify my scrambler in the spring.

bigdevil/'99 scrambler 400