To port or not to port??

[Deleted member 12676]

I'm done talking to you. A rock has better comprehension.

 

[Street Ryderz]

I'm done talking to you. A rock has better comprehension.

Why dont you answer the questions then since you claim to know it all?

 

[Carl Walichnowski]

Being a noobie I have no clue what you guys are talking about so that being said, with my set up as it is would it be beneficial to buy a Reed Valve?

 

[Street Ryderz]

Being a noobie I have no clue what you guys are talking about so that being said, with my set up as it is would it be beneficial to buy a Reed Valve?

Probably not to your wife LOL!The reed valve unless it is a case reed set up doesn't really IMO make that big a difference and for a noob would be more difficult to tune properly most guys running reeds right now are running them really rich and rely on the pipe to see any gain!

 

[gary55]

It's the most ridiculous thing thing I've ever heard. The duration of the port is what is being measured. How on earth is this duration going to remain the same when is is no longer as tall, or is altered to be lower. How is this duration going to not be affected if you alter the the skirt allowing it to open earlier and stay open longer.
It's a measurement of linear distance transfered to a wheel to more easily read and adjust. So unless you live in a place where the dimension height has no rule the duration of the open state is going to change. It's also a measurement of time so lowering the bottom inlet, the longer it is open, or trimming the skirt, the sooner the the skirt passes the bottom the longer it will be open. So if you still think you can lower the inlet to half it's original height and maintain the same intake duration I'm done.

 

[Street Ryderz]

It's the most ridiculous thing thing I've ever heard. The duration of the port is what is being measured. How on earth is this duration going to remain the same when is is no longer as tall, or is altered to be lower. How is this duration going to not be affected if you alter the the skirt allowing it to open earlier and stay open longer. It's a time measurement transfered to a wheel to more easily read and adjust. So unless you live in a place where where time has no rule the duration of the open state is going to change

The part that he is saying about measured from the top to piston skirt on the inlet side not the port is right but I was trying to say is that in the gt5a the piston is a mm shorter than the generic's next the window is lower and slightly taller all of witch equate to more duration no question!If you alter the skirt to open sooner again duration changes as you said it's also open longer for the vac half of the duration to see more volume pulled in!

 

[Frankenstein]

Because duration is the length of time it remains uncovered... As the piston comes down its skirt starts covering the top of the port and shuts down across it. Untill that skirt actually closes off the port the intake is still feeding the crankcase, the point in the rotation when that skirt closes the port is what is considered the end of that duration.

If you remove some skirt then as the transfers are sending the compressed air up to the combustion chamber that you could manage to squeeze a bit more air in there for whatever reason, in jags case the expansion chamber should have this pulling effect as the exhausts are being whooshed by an echo of a past bang they should pull more fuel and air all the way down from the crankcase.

Makes sense I guess, and on non expansion chamber bikes I guess there's some special math involved for figuring out how to make use of it.

 

[Street Ryderz]

Because duration is the length of time it remains uncovered... As the piston comes down its skirt starts covering the top of the port and shuts down across it. Untill that skirt actually closes off the port the intake is still feeding the crankcase, the point in the rotation when that skirt closes the port is what is considered the end of that duration.

If you remove some skirt then as the transfers are sending the compressed air up to the combustion chamber that you could manage to squeeze a bit more air in there for whatever reason, in jags case the expansion chamber should have this pulling effect as the exhausts are being whooshed by an echo of a past bang they should pull more fuel and air all the way down from the crankcase.

Makes sense I guess, and on non expansion chamber bikes I guess there's some special math involved for figuring out how to make use of it.

I dont think jag has it figured out quite right for that if you look at the animation and notice that when the exhaust pressure wave exits the cylinder yes there may be a vacume behind it but the next charge comming up the transfers is also pressurized and the vac from exhaust is pulling it out of the cylinder not more up the transfers because there is only so much there to draw from,He says that if using a reed valve that that vac behind the exhaust will pull on the reeds for more intake volume but it dosen't there isnt time for that to happen before the pressure change for the return wave to hit the cylinder at the right time!http://kcsbikes.com/pics/expansion_chamber.gif

 

[gary55]

I dont think jag has it figured out quite right for that if you look at the animation and notice that when the exhaust pressure wave exits the cylinder yes there may be a vacume behind it but the next charge comming up the transfers is also pressurized and the vac from exhaust is pulling it out of the cylinder not more up the transfers because there is only so much there to draw from,He says that if using a reed valve that that vac behind the exhaust will pull on the reeds for more intake volume but it dosen't there isnt time for that to happen before the pressure change for the return wave to hit the cylinder at the right time!http://kcsbikes.com/pics/expansion_chamber.gif

This is how I see this one. Right or wrong, pff you tell me. That combusted gas is wanting to get out of that explosion really bad by the time it's freed, and is haulin some serious ass down that pipe. The speed of the new charge can't be going anywhere near that speed. It's getting pushed around a little bit, but it ain't been exploded.
So how ever much - pressure is created in the cyl. is going to speed up the new charge coming in. It's kinda clearing the path. The better the pipe scavenges the clearer the path, and the greater the velocity of the new charge up the transfers. I can imagine on some bad assed high rpm monster piped engine it could suck open the reed on a boost port engine, but that's me imagining things.

 

[Street Ryderz]

This is how I see this one. Right or wrong, pff you tell me. That combusted gas is wanting to get out of that explosion really bad by the time it's freed, and is haulin some serious ass down that pipe. The speed of the new charge can't be going anywhere near that speed. It's getting pushed around a little bit, but it ain't been exploded.
So how ever much - pressure is created in the cyl. is going to speed up the new charge coming in. It's kinda clearing the path. The better the pipe scavenges the clearer the path, and the greater the velocity of the new charge up the transfers. I can imagine on some bad assed high rpm monster piped engine it could suck open the reed on a boost port engine, but that's me imagining things.

The problem with that is as soon as the piston starts it's decent to push the fresh charge up the transfer it's now creating pressure to do so and that pressure will close the reeds and now at the exact same time the vac from exiting exhaust is sopossed to overcome that exsisting pressure and pull again on the reeds in a fraction of a second!Humm I dont think so! Scavaging refers to the pipe timming pushing some of the lost charge back into the cylinder and get more bang that would be lost on a reg pipe!