> >> Do they always bore the port at an angle rather than straight from
> >> the side?
> >> Can one request a port bored from the side?
> >> Joe Berki
> >>
> >>>
> >>>
> >>> Does anyone know what diameter the P Port housings are that RB
> sells?
> >>> ID, OD ?
> >>> Thanks for any help
> >>>
> >>> Joe Berki
> >>> Limo EZ
> >>>
> >>> My guess is BIG :) I'll forward this to Jim.
> >>>
> >>> --
> >>> Paul Lamar ...No rotor no motor.
> >>
> >>
> >> Do they always bore the port at an angle rather than straight from
> >> the side?
> >> Can one request a port bored from the side?
> >> Joe Berki
> >>
> >> I'll send that question too.
> >>
> >> BTW My machinist friend is boring out a junk rotor housing as we
> >> speak. If you want them straight in send them to him and he will
> do it.
> >> His shipping address is:
> >>
> >> Jim Poole Care of:
> >> Light Speed Engineering
> >> 416 E. Santa Maria Street,
> >> Hangar #15, Santa Paula, CA 93060
> >>
> >> So far he has done four and is in the process of doing another one
> >> for me. I just
> >> bought him a high quality 1-7/8 inch hole saw to speed the
> process.
> >> I am building a
> >> test junk rotor housing which I will have the SS tubes trial tig
> >> welded to the steel liner.
> >>
> >> Mark Steitle is also working on this idea in Austin but I thought
> >> two separate efforts won't hurt. Mark is an excellent tig welder.
> >>
> >> If that works we are going to build up an RX8 p-port engine and
> test
> >> it on
> >> the Mazdatrix dyno.
> >>
> >> Probably be a four port low power engine as they are probably
> >> cheaper than the
> >> six port high power version. We don't care if it has only four
> side
> >> ports as we
> >> won't be using them anyway. It should idle great as it is
> >> a second or third gen engine in reverse. P-port intake with side
> >> port exhaust. Also the fuel burn should be 8% lower as the raw
> >> unburnt fuel is still recycled by the side exhaust ports.
> >>
> >> Paul Lamar ...No rotor no motor.
> >>
> >>
> >>
> >> Hi Paul,
> >>
> >> Minimum diameter - 1.713", tapering before and after. If you don't
> >> bore at an angle, it is much harder to seal against the inner
> wall.
> >> Mazda factory race housings were straight in from the side.
> There was
> >> no power difference.
> >>
> >> Jim Mederer
> >>
> >> Thanks Jim.
> >>
> >> Paul Lamar
> >>
> >> Paul,
> >>
> >> I really like the idea of the Renesis (RX8) engine with its side
> >> exhaust ports. I was just reading how the two side exhaust ports
> >> combined have almost double the exhaust port area of the P-port
> >> exhaust on the previous generation engine (13B).
> >>
> >> They claim the change in port timing gives a longer expansion
> cycle,
> >> which improves thermal efficiency. I can believe that.
> >>
> >> Another thing I like is that it lowers the exhaust gas
> temperature.
> >> This is especially significant for a turbo engine, where you could
> >> have big issues with the high exhaust temp.
> >>
> >> Adding P-port intakes to the RX8, idling should be very clean as
> you
> >> say. Not to mention the extra power. Btw, I was very surprised to
> >> learn that the so-called "high power" six port version of the RX8
> >> puts out almost 250 hp at 8500 rpm.
> >>
> >> The P-port also simplifies the intake manifold and carburetion. I
> >> wonder if the Bing carbs that come on Rotaxes would be big enough?
> >> (One for each rotor).
> >>
> >>
> >> Regards,
> >>
> >> Gordon.
> >>
> >> They have backed off on the 250 HP claim. It is now 232 HP.
> >>
> >> Paul Lamar ...No rotor no motor.
> >
> >
> >
> > Paul,
> >
> >
> > Yes and Jim at Racing Beat will tell you it is even less than
> 232HP. I
> > wonder about your hopes for good idling performance. With a
> P-port intake
> > there would once again be an overlap before the side exhaust port
> closes
> > right? Good luck with this test.
> >
> > Doug Fir
> >
> > Why do you think that? It is, in effect, exactly like a second
> gen or third
> > gen engine. Two side ports and one peripheral port except they
> are reversed.
> > Exhaust is side port and intake is peripheral.
> >
> > What causes the bad idle is the direct connection between two
> peripheral
> > ports. One exhaust and one intake.
> >
> >
> > Paul Lamar ...No rotor no motor.
>
> Paul,
>
> You are correct. Sorry I mis worded my question. I meant to say the
> overlap
> like the second and third gen will also introduce some exhaust into
> the
> intake negatively affecting the BSFC.
>
> Doug Fir
>
> I don't think that affects the BSFC at medium to high power. It
mainly
> affects the freq. of misfire rate at low power near idle. See the
> attached charts.
>
> IMHO the main reason the RX8 eng. gets 8% better BSFC at high to
> medium power
> is the unburned HCs are kept in the engine and recycled. That will
> not change
> with a P-port RX8 engine. The side exhaust port RX8 engine is all
> about low power
> torque and idle characteristics. In other words the realm of the car.
>
> --
> Paul Lamar ...No rotor no motor.
>
> Paul,
>
> What about the port timing? Do you accept as valid that the later
> opening of the exhaust port on the side-port engine affords a longer
> expansion cycle and therefore better thermal efficiency?
>
> Also, on the RX8 there is no overlap between the intake and exhaust
> port timing at all, right? So if you p-port the intake, there will
> be some overlap? How will this affect efficiency in the high-rpm
> range that is relevant for us in aircraft use?
>
> Regards,
>
> Gordon.
> That probably helps a little. As I said the lack of over lap has
more to
> do with idle than anything else. Actually on balance I would say
> the side exhaust ports probably add a wee bit of back pressure.
> --
> Paul Lamar ...No rotor no motor.
Gordon ,
I'm not going against anything Paul has said, however if I could add a
little in saying, I asked the same sort of questions of mechanical
engineers
and their answer was that that most engines tolerate some overlap (can't
remember the degrees exactly). So the overlap of the RX7 is in line with
this tolerance. I can't imagine the P-port being any worse in the RX8,
although I haven't sat down and tried to work it out in degrees. We are
speaking here primarily about idle as the higher RPM eliminates
contamination, as the exhaust is self evacuating at the higher exhaust
speed/RPM. In fact it's more likely to suck in some inlet charge at
higher
RPM.
George (down under)
George,
Yes, I believe an overlap between exhaust close and intake open can
indeed promote cylinder filling.
In fact I have heard racing types say that the suction effect of the
exhaust can be several times more powerful than the relatively weak
suction effect of the piston moving down the cylinder.
The key appears to be tuning the length of the exhaust pipes to take
advantage of the negative pressure wave, which is reflected back up
the pipe (toward the cylinder) at the point where there is a
discontinuity in the pipe, such as at the exhaust collector.
This negative pressure wave can be so strong in racing engines with
lots of valvle overalp and tuned headers, that it is said to
actually produces something of a supercharging effect by
accelerating the incoming charge.
I would imagine that the rotary could be tuned in the same manner,
but I don't think this is needed in an aircraft engine. And
obviously the idle quality would suffer.
It's interesting that the Renesis has zero overlap and yet makes
very good power. Anyway, I think it's pure speculation how a
p-ported Renesis engine is going to perform. But I think it would
certainly be a worthwhile project to experiment with.
Regards,
Gordon.
The RX8 engine any given RPM makes no more power than any other
13B engine at the same RPM. The increased power of the RX8 engines
comes from changing the red line from 7000 RPM to 9000 RPM alone.
HP is Torque X RPM /5252. The torque is the same. In some cases less.
The main problem is the intake air must make a 90 degree turn.
Increasing the port area has only a minor effect.
Allowing the air to go straight in with a p-port jumps
the VE up 20% increasing the torque from 160 foot pounds to
about 200 foot pounds.
Intake manifolds are aerodynamic devices. If you forced the air
to make 90 degree turns around your airplane the drag would
dramatically increase.
Mazda could jump the HP of the RX8 engine to 300 as soon as they see fit
by adding this device. See the pdf.
Paul Lamar ...No rotor no motor.
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