Boost/transfer relative to exhaust

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daveberari

daveberari

Well-Known Member
Joined
Jun 22, 2017
Messages
45
What is the “rule of thumb“ for the boost/transfer to be upped relative to increase of exhaust?
 
exhaust timing(example:190°) .-transfer timing(example:130°)=60°/2=30°, which is the blow down for this particular engine. boost may or may not be the same. goolgle, 2 stroke blow down
 
steve wood said:
exhaust timing(example:190°) .-transfer timing(example:130°)=60°/2=30°, which is the blow down for this particular engine. boost may or may not be the same. goolgle, 2 stroke blow down
Click to expand...
Ok yes let’s talk blowdown numbers. Is there a NUMBER that is you should be working for
Will that number change for say RPM
Torque
Overall hp-performance
Just trying to get the best performance aside from other things
 
daveberari said:
Ok yes let’s talk blowdown numbers. Is there a NUMBER that is you should be working for
Will that number change for say RPM
Torque
Overall hp-performance
Just trying to get the best performance aside from other things
Click to expand...
check your pms
 
Actually, measuring ports in terms of timing only is too simplified. You need to think in terms of time areas. This goes for blow down as well. See Propwash October 2015.pub for an explanation of all this as applied to a Zenoah 260.

Lohring Miller
 
the higher you get with the blowdown, the less "friendly" your motor becomes. less torque coming off the corner,etc. if you squeeze the trigger,and never let go, it can work, but some people don't do that, and it may not work for them.
 
steve wood said:
the higher you get with the blowdown, the less "friendly" your motor becomes. less torque coming off the corner,etc. if you squeeze the trigger,and never let go, it can work, but some people don't do that, and it may not work for them.
Click to expand...
Well squeezing the trigger from start to finish , I do drive like that sometimes
 
Dave just leave your engine as is,,Just set the ideal bowl cc and head clearance and that in itself will improve your engine for starters👍
 
A two stroke is a two stroke, no matter what the fuel. The same concepts apply. I'm in the process of writing a series of articles on nitro engine design. The biggest differences besides the fuel is size. Most gas engines are larger and friction isn't as big a part in power as it is in nitro engines. I believe piston to liner fit , head button volume and shape, and mechanical design is more important than perfect porting. Most modern engines have reasonably good porting. Power will mostly be found in pipes and head buttons.

Lohring Miller
 
LohringMiller said:
A two stroke is a two stroke, no matter what the fuel. The same concepts apply. I'm in the process of writing a series of articles on nitro engine design. The biggest differences besides the fuel is size. Most gas engines are larger and friction isn't as big a part in power as it is in nitro engines. I believe piston to liner fit , head button volume and shape, and mechanical design is more important than perfect porting. Most modern engines have reasonably good porting. Power will mostly be found in pipes and head buttons.

Lohring Miller
Click to expand...
Not trying for perfect porting -just wanting to understand relationship for optimizing performance along with the many other considerations
Have played with volume, shape, pipe, prop and boat ( all of which I have learned from this discussion group and orhers)
 

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