Hello Mr. Lamar  and rotary people :)

I´m preparing my RX 7 for drift, and I think about engine.
I´m going to use RX 7 engine with RX 8 eccentric shaft and rotors, with
p-port and turbo. Cause I need about 500 HP.
Might it be working properly? What kind of turbo and waste gate should I
use?
Respectfully,
 Dibala, Slovakia

I am not sure an RX8 shaft will work with RX7 end housings. I would
check with
Mazdatrix on that. Perhaps Cary knows. I think there is enough
difference
in the shaft length. RX8 rotors will work. I think you are looking
for a p-port exhaust. It is possible to use a P-port exhaust rotor
housing in an RX8 and have three exhaust ports. That seems to work
very well. Way back in the early eighties Mazda made a 13B engine for
first gen RX7 that had the water O-rings in the rotor housing.
1984 and '85 GSL-SE: 13B engine. That P-port exhaust rotor housing
will work in the RX8 engine. That will give you 3 exhaust ports
per rotor.

It also solves a problem with highly boosted RX8 engines (over 350 HP)
that melt an iron bridge near the exhaust port. See the attached
picture. You might try modifying  the RX8 rotor housing with
an extra cooling water port and use an electric water pump to
feed cold water into this area.

It is also possible to put late 3rd gen RX7 rotor housings in an
NC mill and machine the O-rings groves for use in RX8 end housings.
That will also give you 3 exhaust ports per rotor. It also solves
the melting RX8 exhaust port problem.

Jeff Doddridge <4starr@cox.net <mailto:4starr@cox.net>> can do that
for you if he has time.

"What kind of turbo and waste gate should I use?"

I don't know what works for high power engines. Generally the largest
one you can find :) Mazdatrix might help with that as they build drift
engines.


Paul Lamar


Dibala,

I think the problem with useing the RX8 E-shaft in an RX7
block is the fact that there is a very slight taper on the mainshaft
bearing journals  and in the bearings in the stationary gears. The
bearings can be updated or the stationary gear with the new bearing can
be used. Both shafts are the same material.

The real advantage is that
the in production  RX8 e-shaft is less than half the price of a new RX7
e-shaft.  The RX8 rotors are lighter by a few grams for higher RPM so
the RX8 counterweights need to be used with the RX8 rotors.

For highly
boosted engines the likelihood of detonation increases with higher
compression so  your engine builder will probably recommend the lowest
compression RX7 rotors and matching counterweights. Also the engine
temperature particularly in the rotor increases with boosted engines
promoting heat soak into the flat springs behind the apex seals causing
the springs to be annealed  and loose their spring property.

Ianetti
ceramic apex seals once up to operating temp are better at resisting
detonation and  slow the heat transfer to the springs. Steel aftermarket
apex seals are known to damage rotor housings, if you cannot afford
Ianetti then Mazda are the best.


I don't know what size turbocharger
you need but it will need to make 60 inches of manifold pressure for 500
HP at 6500 RPM and maintain flow capacity to 9500RPM.


One modification
often used is to CNC grooves in  the cooling passages around the spark
plug area to increase heat transfer by way of more surface area.


This forum is more interested in the reliability, robust
construction,  cost and power to weight ratio of rotary engines,
particularly Mazda based, for use in aircraft. While some are
turbocharged the majority are normally aspirated and producing 125HP per
rotor at 7500 RPM.

When more than 250 HP is needed  the base engine
would be the 3 rotor cosmos Mazda block which would still be normally
aspirated.  Much information is available on the newsletter and Paul
Lamar's web site as well as the PaulLamar2  youtube videos. You might
want to download the Kengi Yamaguchi (sp) technical papers dealing with
the development and mathematical formulas used for Mazda rotary engines.
For information on highly boosted 13B engines you might search for web
forums containing terms such as "extreme rotarys"  or drag racing rotary
engines.

The core engines we use and what they use are pretty much
identical for a P-port engine. For a side port they do more extensive
porting but still use the same base parts.  The highly boosted engines
use entirely different intake and exhaust systems and fuel systems.
Ignition systems are more complex since we often use a fixed advance and
operate  continuously in a narrow range of RPM.

george grimes