The intake period is 270 degrees of e-shaft rotation as are all other
 strokes. In a p-port there is a depression in the rotor face that
 connects the intake port with the exhaust port. Surprisingly the
 pressure in the intake is higher than the pressure in the exhaust.
 Therefor air flow, if any, goes from intake to exhaust in theory.
 However air has mass, friction, adhesion and inertia. So what
 goes where and how much is arguable.

 Here is a Racing Beat 3 rotor P-port turbo making 900 HP as I recall.
 Some of the end housing are aluminum.
 Note the size of the turbo charger :) One would think the injectors,
 being on the plenum side of the long intake runners, would lose
 fuel to the exhaust. Jim Medere told me that was not the case.
 In fact the BSFC was slightly better with the injectors at the start
 of the runners. I can't wait to see what happens when Dave Lemon
 builds a welded p-port with a slide throttle RX8 engine. Should be
 around 600 HP or more instead of only 420 HP :)

 As I recall the 3rd gen RX7 stock body land speed record at 268 MPH was
 set with a 3 rotor, 3 turbo side port engine making only about 750 HP.
 It had an ice water inter-cooler as I recall.

 BTW a picture taken from my C182 made the centerfold of Pop Sci
 mag the year of the flood at Bonneville. That was the first year the
 recording holding R.B. 3rd gen 3 rotor RX7 showed up.

 http://www.youtube.com/user/PaulLamar2#p/u/11/JUf_aWVVl7o

 With our man on here Csaba  Csere narrating no less.
 I got my 2 cents in at the end.

 Paul Lamar


 I have to wonder about the concern everyone has been showing about
 overlap.
 There is considerable overlap in any piston engine. The exhaust and
 intake
 valves are both open on even a low output piston engine. There is even
 more
 overlap in a high output engine. I haven't timed any cams lately but iirc
 the cams have about 30 degrees of overlap. Due to the velocity and
 mass of
 the intake charge some will often flow out the exhaust. Since the rotary
 doesn't have valves in the way timing is very important, but a lot of the
 overlap events are similar.
 Bill Jepson


My concern was in the volume of air that passed from the intake through
the chamber and out the exhaust, and the amount of fuel in that flow. It
appeared to me that if the injector timing could be manipulated so that
at cruise power the air passing through to the exhaust carried the least
possible amount of fuel, better efficiency would result.
It may be that the volume lost is inconsequential, or that the timing
cannot improve the loss - but since lean cruise fuel flow is less than
half max power flow and therefore injectors are on less than half the
time, it seems reasonable that some injection timings will be better
than others.
One reason direct injection engines can get better fuel mileage is that
they lose no fuel out the exhaust during valve overlap.  It is also one
reason that port injection engines can get better mileage than those
with throttle -body injection.
I ask the group's forgiveness for my intrusions - I know I have a gift
for causing unintentional irritation.

Victor Roberts


You have a valid point there Victor. When the fuel is injected relative to
top dead center could be important.

So far we have no control over that as Tracy does not publish the source
code of his system. We think he injects fuel once a rev. I'll find out
as soon as I get my engine instrumented with a data aq system.

Paul Lamar


Paul it is probably a good idea to inject into the chamber after the port
closes to prevent charge dilution. I talked to Orbital about direct
injection, and their system was banned by some racing organizations as
being a mild form of supercharging. It wouldn't matter to us of course. You
have used the oil injection hole for a good vacuum source, and it seems a
good one. Someone in the group suggested it as an injection port and it
would probably be good for that as well.
Bill Jepson