I thunk about it some more and discovered a few things on
the dyno. I am having trouble getting the runners short
enough so I made some changes. The 180 degree bend is
9.42 inches long by itself. Add four inches for the tube
stubs going into the engine and you have 13.42 inches. That
only leaves three or four inches for optimization.
We also needed to seal the
slide throttle in case somebody floods the engine during
starting. In normal operation and starting it is no problem
as is but if you flood the engine you could leak a bit
of fuel. I decided to weld the runners to the outer plate
thereby eliminating a couple of flanges and a whole bunch
of nuts and bolts. The inner plate must be still bolted
on or one would never be able to take the engine apart.
I also changed how the flanges and plates are welded to the
runners. They go into a 2 inch holes in the plates improving
the alignment and make the transitions smoother.
the plates are now 3/16 instead of 1/8 thick so welding
the runners to the plates do not warp the plate. Same thickness
as the old flanges. The inner flanges are larger so the same
bolts that bolt the plates together also bolt on the flanges.
This saves a few nuts and bolts and a whole bunch of counter
sunk holes.
The first two pictures are the current design with the long
runners. Way too long.
The third illustration is the new design. I will use ordinary
gasket material to seal the slide throttle. Not all parts
are shown.
BTW Dave did not want to run the dyno today so it will probably
be the middle of next week before we can try out the new intake
manifold vacuum referenced fuel pressure regulator and the EFI.
I hope to improve upon the 230 HP we are getting at 6250 RPM
with the long pipes and the 245 HP we are getting at 7000 RPM
with the short pipes using the Webber 58 mm carb.
Paul Lamar
Hi Paul,
Welcome back. Say if you give me the dimensions on your slide throttle
perhaps I can have a modified version made up over here and bring it with me
when I head that way next month or August at the latest.
Perhaps you answered this one already but which engine do you suppose would
have the better BSFC at 75% cruise....... Turbo P port 13B or turbo Renesis?
With a P port Renesis, I believe their is still some valve overlap, (for the
newcomers) ie; both intake and exhaust open for awhile.
Doug in Japan
Can't say about the turbo but the slide throttle NA P-port
2nd gen engine is showing excellent BSFC from time to time.
As low as .43 at 188 HP, .44 at 221 HP and .46 at 209 HP.
Makes some sense as the intake pumping losses are lower with P-ports.
I am not sure how accurate that data is as our fuel pressure
was varying quite a bit. We need to nail that problem down on
the dyno. Hopefully our new high buck fuel pressure regulator will help.
If not I am going to suggest changing the high pressure fuel pump
to an MSD unit Mark sent.
We are also getting excellent torque readings for a rotary which
jibes with the good BSFC. As high as 202 ft pounds at 5750 RPM while most
side port engines are lucky to see 160 ft pounds including the
RX8 engine. This with the long runners. 196 ft pounds at at 6250
with the shorter runners. Ironically we are seeing this kind
of data with what amounts to a street exhaust system less the
catalyst of course.
I'll work on a slide throttle dimensioned drawing for you.
Paul Lamar
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