Hvp

[chad502ex]

High Velocity porting thread


any input or experience is greatly appreciated.

also, be sure to congradulate Bad Habit while your there too!

http://www.exriders.com/vbb/showthread.php?s=&threadid=198809

[tfuchs]

Idk If it works but I will be trying it on my old 250x this winter sometime.

[dork]

i found this picture of the 2005 crf250x head and the 2006 crf250. the 05 head is on the left.

intake
http://www.rickramsey.net/CRF250Xlg/XR06intakes.jpg
exhaust
http://www.rickramsey.net/CRF250Xlg/XR06exhausts.jpg

[chad502ex]

Originally posted by dork
i found this picture of the 2005 crf250x head and the 2006 crf250. the 05 head is on the left.



now, that's awesome to see that HONDA is thinking velocity. thanks for posting. The 450R has similiar reduced porting compared to the 05 head. Many engine builders concern themselves with huge ports for top end performance. I consider not only the cross-sectional area at the choke point, but also in the time domain meaning how much fuel i can put into the cylinder in a 260 degree time slice. The more i can squeeze into the cylinder in that small opportunity the better

[TRXDresh]

So you are looking for volume, or "Volumetric Efficiency" to be high. Having high velocity does indeed go hand in hand with more volume, but ther are still two different things. You have to balance out your velocity and volumetric efficiency to make the most torque, which in turn yields more HP. You could choke the ports down and have very high velocity, but you will not get the volume of charge that you need to put your engine at the top.

[chad502ex]

Originally posted by TRXDresh
You could choke the ports down and have very high velocity, but you will not get the volume of charge that you need to put your engine at the top.

the amount of epoxy I put into the port (in cc's), I take out with shaping the other area of the port; thus, my overall volume in cc's hasn't changed much- only the shape and the velocity of the port has changed. vector analysis, upper ridge and floor length, and port shape is main cornern for my gains.

I will be measuring the before and after velocity and cfm's this weekend.

you sound so sexy when you're talking all technical...

;)

[chad502ex]

you sound a little funny saying that to him....

LOL!!