Author Topic: Step in the exhaust port  (Read 555 times)

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Offline farmboy

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Re: Step in the exhaust port
« Reply #30 on: May 31, 2014, 09:27:37 pm »
357 XP has stuffers.
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Re: Step in the exhaust port
« Reply #31 on: June 01, 2014, 12:27:49 am »
I have never messed with stuffers before, but I have seen them before when working on a Husky cut off saw.
   I am curious as to what the advantage is.   I realize that your reducing the volume in the crankcase and in theory this gives more pressure in the crankcase when the piston is traveling down.   
But does it not also reduce how much air fuel mixture that will enter the crankcase when the piston is traveling up. 
If so it sounds like a trade off to me.
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Offline aclarke

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Re: Step in the exhaust port
« Reply #32 on: June 02, 2014, 07:00:24 pm »
I don't think a muffler motor is gonna have the ability to fill the crankcase and take advantage of the extra volume like a motor with tuned pipe, so smaller may pump more efficiently granted the ports are designed to keep the added flow from going out the exhaust . Lots of conflicting info about case volume and pumping efficiency online, hard to make sense of what's optimum

Offline SquareFile

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Re: Step in the exhaust port
« Reply #33 on: November 20, 2018, 09:10:25 am »
Older thread but the topic interested me studying cylinders. I feel the step down is more of a "shelf" for ring support on a downward angled port. Remove it and I'm sure bad things are going to happen. JMO, it's not for performance, tho it could aid. I have no proof it does or does not.
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Offline Cut4fun .

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Re: Step in the exhaust port
« Reply #34 on: November 20, 2018, 09:57:32 am »
Blast from the past.

Funny thing is I noticed a Partner I got in has that T port deal that Adam had talked about on the P100 a page or so back.  On the P55 they said it was for this reason.   Features built in decompression system located at exhaust port. Named "T Port" system.
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Offline mdavlee .

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Re: Step in the exhaust port
« Reply #35 on: November 20, 2018, 07:18:13 pm »
Older thread but the topic interested me studying cylinders. I feel the step down is more of a "shelf" for ring support on a downward angled port. Remove it and I'm sure bad things are going to happen. JMO, it's not for performance, tho it could aid. I have no proof it does or does not.
It sure canít hurt to leave it there when you raise the exhaust a lot. Some guys have blended it on the 7910 cylinders and they free port with as little as .030Ē off the base.

Offline Al Smith

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Re: Step in the exhaust port
« Reply #36 on: November 28, 2018, 04:34:07 am »
This case volume reduction thing could get rather complex .Full circle cranks,more stuffer would raise the crankcase pressure which would increase the velocity  of transfer .Theoretically with decreased volume by lowering the cylinder to raise compression it might not require as much actual crankcase volume .As to  how much remains a good question .With a tuned pipe it's going to back charge part of it back in .With a pressure can it's going to stop the transfer when the pressure rise equals the exhaust out pressure .With a megaphone or open exhaust it would all leak out ---makes my head hurt thinking about it -----

 

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