Anti-Reversal Headers and Similar

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Anti-Reversal Headers and Similar

Postby kfxnando » Sun Jan 23, 2011 5:00 am

might take a few posts to get all the info onto here, as there are a few aspects of it!!

will do the Yamaha Ex-up valve as well, as that could very well of been the start of the whole story

will also start with info that I have posted else were and then add and expand!!

Starts Here
he one big difference is that the ex-up valve is controlled from a server motor vial two control cables!!

lets start with this example, cyl heads with very big ports/valves loose efficiency low revs!!
with 16valve/20valve heads, we have a similar effect

remember driving the 16 valve carolas and would find myself stalling the car often, this was due to the big loss of efficiency at the lower revs, some of those motors rev to 8000rpm in stock form!!

with the 20 valve it was even worse!!
and now add that its a much smaller motor and even worse!!

to get the cams to operate efficiently at revs of up to 12000rpm for a 1000cc
there has to be a huge amount of valve/cam overlap, witch is bad for power at low revs
reason,the huge overlap (the time that both valves are open at the same time) allowed the back pulse traveling up the header pipes to come back into the combustion chamber, preventing the combustion chamber from filling up properly with a fresh charge!!
at best it would contaminate the new charge!!

hence the ex-up valve
it normally sits where all the header pipes come together, and is in the shape similar to a ''C'' the opening of the ''C'' facing the back or the Exhaust
at low revs the gases would go past the ''C-shaped valve'' and when the pulse turned around (that is another whole explanation) it would hit the cup in the ''C'' and find a lot of restriction to return up the header pipe and into the combustion chamber!!

with stopping the back pulse from returning up the header pipe and into the combustion chamber, one ends up with a properly filled combustion chamber of a fresh charge

with that in mind, motor ends up making more power at low revs and mid revs range!!
and once the revs climb there is the big added advantage of the 20valve efficiency at high revs!!

as the revs climb the ''C'' shaped valve rotates into a compartment, so as not to restrict the exhaust at higher revs!!

Yamaha FZR1000 at about 190/195km/h and at around 8000rpm, in 5th gear
open the throttle and the motor comes alive and pulls hard all over again to give a huge adrenalin rush!!

hope this explains the ex-up valve :mrgreen: :mrgreen:
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