How's my port work?
- Thread starter 2StrokeThompson
- Start date
Not sure if its the photo but the port on left looks wider. Also did you chamfer the edges on the ports. You don't want shape edges that will catch the piston
I am no expert, but I have opinions and they are worth double what you pay for them!
I am going to suggest "not so great". Too big.
When you pour gas into a funnel, what does it do?
Sloshes around in circles waiting to go down the tube, right?
What happens when you let your thumb off a siphon tube?
Fluid shoots out and sucks out even the last bit.
You need a more or less constant cross sectional area from the carb to port window, only ever funneling very gently. Whenever the cross sectional area opens up, the flow slows down and the fuel drops out of suspension.
So what should you do? RUN IT!
Try it. See if I'm full of bull or what.
Test it out and see how it works compared to how it was before.
What if it does work worse? You can fix it. You can build up the intake with epoxy.
Try it out first, see what you think?
Steve
I am going to suggest "not so great". Too big.
When you pour gas into a funnel, what does it do?
Sloshes around in circles waiting to go down the tube, right?
What happens when you let your thumb off a siphon tube?
Fluid shoots out and sucks out even the last bit.
You need a more or less constant cross sectional area from the carb to port window, only ever funneling very gently. Whenever the cross sectional area opens up, the flow slows down and the fuel drops out of suspension.
So what should you do? RUN IT!
Try it. See if I'm full of bull or what.
Test it out and see how it works compared to how it was before.
What if it does work worse? You can fix it. You can build up the intake with epoxy.
Try it out first, see what you think?
Steve
I did chamfer all port windows And made sure NOT to adjust them to much but i did widen and open the inside of the top port to get rid of the air pockets in the corners and increase the air velocity. It was actually a very narrow port due to the casting.
Well in the case of the funnel , they work off gravity so instead of vacuum so i cant see the connection between the two. If the cylinder/piston creates a vacuum that pulls air and fuel in how does it relate to me pouring fuel down a funnel?? But you may have a point with the siphon. Correct me if wrong but are you saying that by Opening the channel it may require more vacuum to increase speed of traveling fuel mixture?
The top port's purpose is as a guide to keep the transfers' flow symmetrical.
It needs to shoot a straight high speed jet of air across the cylinder to act as a divider and guide for the transfers' flow. So again, instead of a funnel, it should be shaped like a tube, to aim the squirt.
Here is my reedbox porting, which is only slightly widened, mostly epoxy filled:
Note the straight shot of the top port?
Also the bridge actually is fatter than at the cylinder face so it guides the flow to the center of the piston. The outer walls flare out to have a smooth fill of the interior of the piston. The whole port is a smooth guide of the flow to the window and near constant cross sectional area when the reed is in place. I run without reed stops as well, the box is filled to act as a reed stop.
Here is what the fill in looks like in red in cross section (thanks to JoeAK47 for the orig pict)
So the goals are
1) tubes instead of funnels
2) tubes aimed in the right directions
3) Near constant cross sectional area for maximum and constant velocity.
But then, I don't do this for a living, just a hobbyist.
Steve
It needs to shoot a straight high speed jet of air across the cylinder to act as a divider and guide for the transfers' flow. So again, instead of a funnel, it should be shaped like a tube, to aim the squirt.
Here is my reedbox porting, which is only slightly widened, mostly epoxy filled:
Note the straight shot of the top port?
Also the bridge actually is fatter than at the cylinder face so it guides the flow to the center of the piston. The outer walls flare out to have a smooth fill of the interior of the piston. The whole port is a smooth guide of the flow to the window and near constant cross sectional area when the reed is in place. I run without reed stops as well, the box is filled to act as a reed stop.
Here is what the fill in looks like in red in cross section (thanks to JoeAK47 for the orig pict)
So the goals are
1) tubes instead of funnels
2) tubes aimed in the right directions
3) Near constant cross sectional area for maximum and constant velocity.
But then, I don't do this for a living, just a hobbyist.
Steve
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The big volume of the ported out reedbox acts as a damper/muffler/attenuator losing the momentum of the intake mixture flow. Piston window opens, you have milliseconds for (no more than) 14.69psi of vacuum to draw the charge of air in. If you let that air slow down in a big box, the fuel will drop out of suspension and there is no way 14.69psi is going to draw it off the floor of the readbox. The gulp of air is going to be lean with a dribble of fuel running down the port and cylinder walls. Later of course it will go rich burning up that dribbled fuel. Makes jetting a biatch.
So by keeping everything as a tube, maximum momentum is maintained. When the piston window closes it sends a strong signal up the port, working with the resonance tuning that Yamaha cleverly built into the system. A big reedbox destroys (dampens) that.
The funnel analogy? All that water spins around not knowing where to go, blocking the flow of water that could have run down the pipe. Same with your intake. Vacuum doesn't "PULL" the mixture in. Vacuum is nothing. Vacuum is atmospheric pressure PUSHING the mixture thru the port window. Make it funnel shaped and it will be a bottleneck too.
Steve
I saw this in another post and found it very helpful. It was actually the pictures i went off of during the process of porting my cyl. I figured i didnt want to take to much away but gain more control of the flow of air entering the intake. So as u can see this is what i came up with.The top port's purpose is as a guide to keep the transfers' flow symmetrical.
It needs to shoot a straight high speed jet of air across the cylinder to act as a divider and guide for the transfers' flow. So again, instead of a funnel, it should be shaped like a tube, to aim the squirt.
Here is my reedbox porting, which is only slightly widened, mostly epoxy filled:
Note the straight shot of the top port?
Also the bridge actually is fatter than at the cylinder face so it guides the flow to the center of the piston. The outer walls flare out to have a smooth fill of the interior of the piston. The whole port is a smooth guide of the flow to the window and near constant cross sectional area when the reed is in place. I run without reed stops as well, the box is filled to act as a reed stop.
Here is what the fill in looks like in red in cross section (thanks to JoeAK47 for the orig pict)
So the goals are
1) tubes instead of funnels
2) tubes aimed in the right directions
3) Near constant cross sectional area for maximum and constant velocity.
But then, I don't do this for a living, just a hobbyist.
Steve
There are big differences.
Look at the sketches on the sidebar. Red/orange is yours, grey/black is mine.
Very rough sketch, but does it make sense?
Again, I am a bit of a heretic and am not a pro porter, nor do I race.
Just a few decades of doing this with an experimental bent.
I look for other's advice on here too.
I know there are those of you who produce amazing results.
Steve
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The small center port up top is the boost port. Dont realy mess with that (meaning the roof specificaly and angles) other than cleaning the casting flaws around it. It is to help with scavenging to clear the spent gasses from the head and around the spark plug.
You will notice the biggest differnce when/if you port the exhaust port. Remember all changes need to work hand in hand with eachother. Meaning dont port for low end torque with a high rpm pipe etc..
Best advice i can give is read up as much as you can and understnd why. There is tons of info out there. Quite a bit on this site also if you look.
If you need help finding stuff to read let me know and i will send you some links.
Best advice i can give is read up as much as you can and understnd why. There is tons of info out there. Quite a bit on this site also if you look.
If you need help finding stuff to read let me know and i will send you some links.
You will want to port that exhaust without question. All or nothing. When you improve one area, the others become a restriction. Everything works as a team.
Hey Steve!
Hey Steve!
Thanks for you thoughts fellas Steve: the rough sketch is pretty clear to me it took me a minute to see to picture it in my mind but i noticed how you widened your port windows compared to me widening my reedcage. Being that i have already ported this cyl im going to try it for experimental purposes. I have another jug so im going to be trying a different port sstyle similar to urs to compare differences.
Jus_me: I have ported the exhaust along with the transfer ports according to Kor's video series. I very much would like a few links to do more research. Knowing is growing!
Ak47: thanks for getting that cyl cut to give a different view of things.that was also helpful to see exactly what to remove when porting the inside the intake.
If there's anymore info please do share i love the way these little 2Strokes work.
Jus_me: I have ported the exhaust along with the transfer ports according to Kor's video series. I very much would like a few links to do more research. Knowing is growing!
Ak47: thanks for getting that cyl cut to give a different view of things.that was also helpful to see exactly what to remove when porting the inside the intake.
If there's anymore info please do share i love the way these little 2Strokes work.
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Hey Joe!
Search and Rescue is doing well up here now Joe, I can put my attention back into the bikes, quads and sleds, although I am getting way too busy with a contracting company I work with. The cylinder you did for us is still pulling strong, great mid-range for a power porting.
Folks, this Joe guy does a great job of porting. Besides doing beautiful work, it hauls!
Read his stuff.
Steve
Yeah, try it. That is how you learn.
The cylinder will slip on and off in about 15 mins, so don't try to do everything at once or go to the limit on the first try. For the exhaust I widen it at the top only, and only go 1-2mm higher on the roof to gain some rpm. Try only 1mm first. Here is what I aim for:
Don't touch much else except to polish it.
Only the window needs to be larger, not the port.
Here is a copy of Joe's original pict:
There may be a larger copy and more picts elsewhere on this site.
Steve
The cylinder will slip on and off in about 15 mins, so don't try to do everything at once or go to the limit on the first try. For the exhaust I widen it at the top only, and only go 1-2mm higher on the roof to gain some rpm. Try only 1mm first. Here is what I aim for:
Don't touch much else except to polish it.
Only the window needs to be larger, not the port.
Here is a copy of Joe's original pict:
There may be a larger copy and more picts elsewhere on this site.
Steve
Good to hear Steve! I now work at the Tesla Gigafactory here in Nevada. Awesome place and FAST all electric cars! Tons of robotics! Lots to learn. Soon I'm going to be building the model 3 drive train for the new affordable Tesla model 3 car. Pretty exciting! Right now I'm building the "power wall 2.0" home energy products. Wild stuff!
Not enough hours in the day sometimes.
Now back to the thread...
I'll see if I can re-post some photos of that cylinder again. I still have it in a box.
Also...
folks...Don't forget to take a look at the "porting templates" that Ken Oconnor racing sells. These are absolutely fantastic! Worth every penny and make power!!!
Go here and check them out... \/ \/ \/
http://www.kenoconnorracing.com/
Not enough hours in the day sometimes.
Now back to the thread...
I'll see if I can re-post some photos of that cylinder again. I still have it in a box.
Also...
folks...Don't forget to take a look at the "porting templates" that Ken Oconnor racing sells. These are absolutely fantastic! Worth every penny and make power!!!
Go here and check them out... \/ \/ \/
http://www.kenoconnorracing.com/
