Lynn, does the timing given, calculated by the
rotor uncovering and covering the port, or the side seal uncovering/covering
the port opening?
I was thinking the RX8 rotor will be slightly
different (bigger) with the harased edges.
George ( down
under)
I only have 12A stuff, but here you are:
Intake port at the manifold. 1.695" Round
Exhaust port at the manifold 1.645" Round
IO 86 Degrees BTDC
IC 75 Degrees ABDC
EO 73 Degrees BBDC
EC 65 Degrees ATDC
A Racing Beat Street Port:
IO 25 Degrees ATDC
IC 60 Degrees ABDC
EO 84 Degrees BBDC
EC 48 Degrees ATDC
In side port engines, it is the rotor closing the port.
In the peripheral port engines it is the apex seal closing the port.
Actually the port is timed by the apex seal.
The port never closes in the way the side port engine has the rotor blank
off the port in operation.
So, the Pport can flow way more than the side port, even with smaller
runners and ports.
Lynn E. Hanover
Lynn, and Jerry
Thanks and that confirms my testing, I set-up my degree wheel and mapped
out the degrees and measured the distance and sure enough 44mm= 1.73.
43mm = 1.695.
I've also confirmed the street ports (side ports) can't flow the
necessary amount for the HP required, running out of puff @ 164 KW/ 264HP at
8,500 or about 116/117 hp at 7,500 - we can do better.
So now that I have convinced myself - it's back to the P-port. As
Lynn said the P-port flows more than the street port for a number of reasons,
but one thing surprised me to hear was that the rotary can't overcome a choked
inlet to the extent a piston engine can - therefore any
restrictive inlet will result in less HP. Apparently the velocity increase
argument doesn't exist because of this reason, so a smaller p-port inlet is
out. Not only this but with a restrictive port the engine is likely to
pull exhaust( because of the overlap), causing rough running, with a sudden
decrease in RPM - so I'm led to believe.
Therefore I need a carby with a inlet of 44mm or two smaller ones. I know
Bill Jepson is aiming for 1.8" P-ports ( 45.72mm) in his 20B - this is all
getting close to PL claims of 2" OD.
This isn't a wasted exercise on my part, so I hope someone else got
something out of it as well.
George ( down under)
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