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 exhuast 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.