Two Stroke Max Performance Question

[TRIS]

Ok Guys. I Don't Know Why And Can;t Understand Why Two Strokes Performance Has Not Been Improved Via The Size Of The Expansion Pipe.

By This I Mean....when You Look At Dynos Of 125's With A Dented Pipe And One Of A Normal Pipe, The Dented Pipe Has Advantages For Top End And The Undented Pipe Gives More Bottom End But Less Top End.

So....why Has No One Tried To Make A 2 Stroke With 2 Expansion Pipes, Both Different Sizes, And 2 Controleed Exhaust Ports. This Way Both Pipes Can Be Opened To Begin With, Then As The Revs Go Up, The Smaller Pipe Will Cut Off First, Giving More Power At That Rev Range. Then At Higher Revs The Pipes Swap And The Smaller One Is Used.

Surely This Way A 125's Power Can Be Increased Even More, It Will Have More Power All The Way Up The Rev Range And Could Be Perfected If People Advanced It.

I Am 16 And This Is A Wild Guess But It Makes Sense To Me. Any Thoughts???

 

[adam728]

Weight, complexity, cost, size. Also does nothing for a 2 stroke where it needs help the most to be saved, emissions.

What you described is the job a power valve does.

If you want to learn about how pipes effect power I suggest doing some searhcing. I can't think of their names, but there are a few books that cover the theories behind it. Head pipe length/diameter, the angle of taper of the conical areas, length/diameter of the center section, and length/diameter of the stinger all effect how a 2 stroke engine will perform.

 

[trial_07]

Rich Rohrich here on this forum is better than a book :cool: How would you connect the two pipes to the cylinder? Pipes affect performance, but not to the point of re-inventing a whole new exhaust system.

 

[TRIS]

ohhh....ok. thanks guys. i remember about the power valve now, it adjusts the opening of teh exahaust port doesn't it?? also does the powervalve adjust the fuel and air ratios???

 

[Jaybird]

The combustion has taken place once the gasses reach the power valves and exhaust.
Prior to combustion taking place, the carburator meters the amount and flow rate of the fuel and air by means of various devices. These devices give us the best means to get close to optimum power.

After the carb sees the fuel and air, the reeds manipulate the air/fuel mixture even further, which also effects the performance. If you have the proper air volume, and have that volume of air metered and mixed with the fuel properly, the combustion process gets closer to being as effecient as it possibly can be...providing you have the proper fuel for the intake tract length (distance/volume from the entrance of the carburator to the top of the piston when BDC) and burn rate you are wanting to achieve.
And as you have discovered, the metering of the exhaust gasses also greatly effects performance.
But there is no magic pill, and the secret to making an engine run to it's fullest potential, is to find synergism using all these areas combined.