Heat Kills? not?

[woodsracer144]

ok look at this, it will tell you how a 2 stroke works

http://www.atvriders.com/articles/twostroke.html

at the bottom theres a little thing that goes in motion that will show you...

one on the intake stroke, why does it alow the hot gas from the exhaust come back in, i would want all that to go out not? heat kills... why isnt it all fresh air on the intake that fills it up?

[jcs003]

its called scavenging. it helps create a more dense, more efficient burn. the hotter the exhaust gas the faster it exits the combustion chamber. in a 4-cycle its called valve overlap.

[woodsracer144]

huh? i knew it had the head pipe design like that so the exhaust moved back and fourth but i didnt know it sucked hot air that it just shot out back in there... i would have thought that would kill the span of your motor....

[C-LEIGH RACING]

What you guys are thinking about, the hot exhaust gases comming back in to the cylinder, dont normaly happen in real life if the pipe is built right.
The build of a pipe, the angles, the lenght, the OD shape of the pipe is like it is for a reason.
The reason a pipe is shaped like it is made, is because it is a timming device built in a shape to match up with the opening & closing times of the ports.

When you watch the video part & see the V shape >>>> going out & then turning around, <<<<< comming back, that is indicating the travel of the pulse wave going out into the pipe & then returning back to the cylinder.
When you see the motions happening in that video, the green color is fresh intake charge being blown up into the cylinder & then as the suction wave from the pipe gets stronger it draws some of that fresh charge out into the pipe. Then, when the pulse wave turns around at the end of the pipe, that wave pushes the fresh charge back into the cylinder.
All this pulse wave motion works just like I describe it unless the pipe is not built right to match up with the open & closing times of the ports.
If the pipe build over all is to short & not matched up with the times that the ports open & close, then it could push hot exhaust back into the cylinder.

That video diagram, is showing you what all takes place during one rotation cycle of the crank, & the importance of the build of the pipe matching up with the times that the ports open & close. Its all about timmings of when the ports open & close & making the wave travel through the pipe in a certian amount of time, go out, turn around & then come back.
The pulse wave travels a 1700 FPS & would maintain that same speed if the pipe was just a straight piece of round pipe, but because the 2 stroke pipe has different sizes & shapes, it can make the wave speed up or slow down.

Neil

[woodsracer144]

holy man Neil! every think i think i got a good grip on these motors you tell me something i never knew! holy ball sack!
(Neil check out my polanda build, im gonna need you to chime in on some pics im puttin up tonight.)

[machwon]

Reminds me of the old 86 trx cylinders that get the burnt exhaust gas build up in the transfer ports. Its a good example of porting not matching the pipe.

[woodsracer144]

http://www.exriders.com/vbb/showthread.php?s=&threadid=424490

[palot]

Originally posted by machwon
Reminds me of the old 86 trx cylinders that get the burnt exhaust gas build up in the transfer ports. Its a good example of porting not matching the pipe.


You got that one peged Bob.
Ok, now throw a stick in the spokes.
Say you have a big bore Pro-x & your seeing the exhaust burn down in the transfers.

Everythings measured out like it should be, ports set, pipe build just right matching up with the porting, but you still got the back flow exhaust down the transfers.

What is going on here is, the aux exhaust ports are cut to far around at the sides in the sleeve & because of the machining on the piston around the wrist pin area, as the piston travels that open area on the piston is causing aux exhaust port & main transfer port linking.
Causes just a cluster of ill effects like, loss of fresh charge way to early out into the exhaust port & header & then a weak presure flow up through the ports. Now because of that low presure up through the ports, your not cramming as much on top of the piston to get popped once the plug fires off, so, you end up with way less power output than you had planed in your build.

Been a ongoing problem, for a few years now, with the Pro-X cylinders & Wiseco pistons machining, but when you get those aux ports filled in so the linking is stopped, power is back up.

Sometimes even on a new replacement sleeve, the aux exhaust ports are already machined around to far, so then you got to deal with that before the sleeve is ever installed.
Would almost make one think, it is fixxed like that so the highest HP could not be pulled out of those cylinders.
Neil

[C-LEIGH RACING]

The above post is from me, Neil, C-Leigh Racing.

My soninlaw is so busy when he is on the computer he cant remember to log out when hes ready to change to another site.
Neil

[woodsracer144]

haha neil... could you help me with the port questions on my other cylinder im working? thanks

[machwon]

Originally posted by C-LEIGH RACING
The above post is from me, Neil, C-Leigh Racing.

My soninlaw is so busy when he is on the computer he cant remember to log out when hes ready to change to another site.
Neil

Neil, I wondered who was posting with that info on the big bores. I didn't get back to this one last night as I wanted to look into it more. I see what you are talking about in those cylinders. I've always tried to buy the old econo port or no porting when I had to purchase cylinders as well. I usually never like how high the transfers come a lot of times. I like to think I still get good HP even with the flaws you mentioned (low 70's, 363cc) on race gas, no pv. I usually do try and avoid the cross contamination by working the port directions and such.

Have you noticed gains by closing off the aux ports? I also was looking at a new ESR 350 cylinder I have a build I'm doing. On the new piston for this kit they have eyebrowed material over top of the wrist pin, but you still have the wrist pin hole area. I could post a pic if I didn't explain this very well.

[woodsracer144]

i need some pics! i'm workin on a Polanda right now but when he said that about the pipes matching the cyl i thought that my 250r pipe not might match... also the crank case ratio.. I'll post up some stuff after i get my cyl done so i can mount it on cases and make it almost run...

[Motofool250r]

woods racer what pipe are you running i have a shearer OOF pipe converted to an inframe pipe, no 250r pipe is gonna bolt up you know that right?

[woodsracer144]

i got a LRD 350 BB... i was gonna make a Exhuast Flange for it... didn you have a motor forsale on here a little bit ago?

[Motofool250r]

me no, havent sold any R parts or anything on here bought some stuff though

[woodsracer144]

what do oyu mean that it wont fit? cause of the exhaust angle or cause the cyl is so big or both?

[C-LEIGH RACING]

Originally posted by machwon
Neil, I wondered who was posting with that info on the big bores. I didn't get back to this one last night as I wanted to look into it more. I see what you are talking about in those cylinders. I've always tried to buy the old econo port or no porting when I had to purchase cylinders as well. I usually never like how high the transfers come a lot of times. I like to think I still get good HP even with the flaws you mentioned (low 70's, 363cc) on race gas, no pv. I usually do try and avoid the cross contamination by working the port directions and such.

Have you noticed gains by closing off the aux ports? I also was looking at a new ESR 350 cylinder I have a build I'm doing. On the new piston for this kit they have eyebrowed material over top of the wrist pin, but you still have the wrist pin hole area. I could post a pic if I didn't explain this very well.


Far as closing off the aux exhaust ports, no, not closed them off completely, but we welded the sleeve up so that only about half of the port opening was left & then I worked it back in shape so that was close to 4mm vertical distance from the port opening to the machining on the side of the piston.
Was on a 310 jug we did this & I got no idea how much more in hp it was, but it was running in third in the Pro class main holding its own till the little o ring in the head dome around the spark plug gave out & locked her up.

He was giving Shane Hitt & Tim Farr a fit till half way through the main.
Later on I got to thinking back what all was going on at our pit, that 250R ran the heat race & lost some coolant & then it sat there & nobody offered a hand to check the radiator level & it went back out for the main & ran hot.
Ol 4 poker was more important along that time & that 250R just sat there like a poor ol whooped pup & nobody though to check.
If it had been my bike, you could rest assured that radiator cap would have come off, I would have known it was full.
Neil

[woodsracer144]

whata high jack a thread! haha... jk...

neil, i could use some help on my polanda... like really really bad...