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RV-6 Project
Mazda 13B
 

 

 

 

 

 

 

                       

Airventure Racers from my airpark! VIDEO

Airventure Cup Race 2005

Best Auto Engine Conversion SWRFI 2004

Outstanding Homebuilt  Sun n Fun 2003

                                                            

I began this project in November of 1992, with the arrival of the tail kit.  Much has ensued since then, including moving, building a house and hangar, marrying off two daughters, and an airline down-sizing.  It first flew on June 15, 2002.
 
What you see here is an updated overview of N268BL, with emphasis on the unique power plant, the Mazda 13B rotary.  Many thanks to Tracy Crook for his reduction drive and engine controller, and to the guys on the Rotary List for info, feedback and sanity checks.  I have spared you some of the earlier versions of things.  This is how it looks and works as of January, 2009.  Soon to clock 600 hours on the engine.
 
Photo coverage of some of our travels in N268BL may be seen in the Photo Album section at left. Also see:
 
 

 

 

 

 

 

 

 

 

 

 

 

       

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It seemed such a shame to take a brand new engine mount and plan to cut it to pieces, but the rotary just wouldn't fit thru that ring.  I used the conical mount to destroy.  PVC pipe is used to rough out the new part.  Mount is bolted to a plywood firewall mockup
After much measuring and re-measuring and re-re-re measuring, I whacked out all the pieces except the landing gear sockets with a hacksaw.  Next project was to weld in a bed mount for the rotary.
I tried to buy a mount from Dave Atkins in Tacoma, but his supplier was fading and he couldn't get me one in a timely fashion.  I did my best to copy what I saw on his photos.
Here is the painted mount on the real firewall.  The original Mazda coils are mounted but were replaced with 4 Corvette coils soon after this was taken.  They are lighter and simpler (and CHEAPER, if one fails).
This is the ugly part - pulling the rotary out of the car.
With all the unnecessary crap removed, it is much prettier.
The alternator is too high in the stock position, so it was moved to the side.  Disregard the intake manifold, as it was too short and restrictive.
Teardown was straightforward using a Haynes manual.  All those seals must be kept organized for re-assembly.  I found the rotor housings had worn through the surfacing along the edge (very common), so I bought another 100,000 mile engine, and guess what.  It was worn the same way! (Duh!)  Bought two new rotor housings from Mazdatrix and had them resurface some of the side housings and replaced one.   I re-used all the metal side seals and springs but replaced the rotor tip seals.  When I run the engine hard, it uses some oil, and it may be from the side seals floating over the oil film rather than wiping it.  This could be from weak (old) springs under the seals. Just a theory.
Mods included JB Weld in the secondary intake tubes to smooth the airflow, as they would be fixed in position anyway.  Also modified the valve in the center of the eccentric shaft (crank shaft) so that oil flows all the time, not just when warm.
Grooves were added inside the water jacket in the vicinity of the plugs.
This supposedly helps heat transfer in this area, which is the hottest.
A 1/4" aluminum plate sits between the block and pan and forms part of the engine mount.  The four large holes near the corners are the seats for the rubber mounts and 3/8" bolts.  The mounts are simply shock absorber ends from NAPA.  Each one is sliced in two, they are reversed so the shoulders face each other, and they lay into the large holes, one under and one over the mounting plate.  A spacer can also be placed under the oil pickup tube to lower it by the same amount.
An early photo that shows the first engine mount.  Not much is needed since the engine runs and starts smoooooth like the car. Eventually installed modified Barry mounts.
ORIGINAL MUFFLER  (Now Replaced)

This shot shows how the muffler fit inside the cowl.  It had 265 hours when it was replaced due to internal failure.

Here is the interior of the muffler.  It was made of 16 gauge stainless steel.  Sorry; I don't remember the specific type of steel.  Ugly welds, but strong.  My theory seems to be "if you can't make it pretty, make it thick".  The angle plate took the heat from the short run out of the rotor exhausts.  It did prevent melting a hole in the side of the muffler.

A simple aluminum heat shield with air space around the muffler prevented damage to the cowl or injector rail.

This was removed at 265 hours.  The inner perforated pipe had come completely loose, and the angle plate shield had been burned completely through.

Plan B is now in effect.

MUFFLER #2  (Now Replaced)

When maximum speed is required, the straight pipes go on!  This will add almost 20 mph to the top speed, but the noise will peel the paint off cars on the highway!

I tried a glass pak bullet style muffler, but it produced no better power than the original muffler, and was almost as loud as the straight pipe.

A stainless steel Spintech 6111 muffler is now installed and quiets it very well.  The power is actually increased over the straight-through muffler, even though back pressure is higher.  This matches Tracy Crook's experience.  It appears that it will cause significant drag, but it will take time to get good numbers on that.

There is a stainless sheet on the belly with Fiberfax under it to reflect heat.  The mounts bolt into 3/4" angle riveted between the floor stiffeners.

 

MUFFLER #3

Tired of being derided for my "non-aerodynamic" muffler, succumbed to pressure to be "like Tracy"!  Flowmaster muffler hanging from BMW rubber loops looks faster, but did not measurably reduce drag.  Oh well.  Here is a view at Airventure 05 after the race.

First intake manifold upgrade.  I you need more photos of a specific area, just e-mail me.

Radiators are evaporator coils from a 1986 Chevy Caprice.  The oil cooler is stock 1988 RX-7, as is the engine.

Manifold #2 details

(Now Replaced)

 

This manifold has a 5.0L Mustang throttle body on it.  The outer (secondary) tubes meet face-to-face for (hopefully) some dynamic effect.  The primary tubes are straight in.  The welds are ugly, but they don't leak and they are all mine - except for some small good-looking ones made by my neighbor.

Manifold #3 details

I assumed that the aerodynamic atrocities committed by bunching all the tubes in a convenient wad were limiting my top end power, so I designed and built another.

A lot of time and effort went into finding and making aerodynamic inlets for the separate induction tubes.  The airbox was fabricated from welded aluminum, and the throttle body was used from the previous manifold.  The geometry of my installation required the use of an idler arm for the throttle linkage.

Careful analysis of the resulting performance yielded NO net measurable increase in power!  Rats.  Well, it looks better, anyway.

This shot shows the flap-actuator motor which controls the cowl flap position.
Top-down view of the firewall.  Shows the Corvette coils with air blast tube for cooling, the belt guard to keep a wayward belt from pulling all the coil wires, and the heater valve for cockpit heating coolant.
Plumbing atop the water pump.  The brass valve is to bleed air from the high point if necessary.  It only needs that if the system is drained and re-filled.  A removable plug would do as well.  The Schrader valve is to pre-load the coolant tank.  I pre-load the bottle to about 10 psi, and it will hold for weeks.  Any leaks will be quickly evident. This arrangement seems to keep the air purged from the system.
The cowl flap opens WAY up.  It is 23 inches wide, and opens at the trailing edge from 2" gap to 6" gap.  When open wide, it is also a speed brake!

For more cooling information, go to the Cooling Page!

I got a little too close with the camera, but here is a new plug along side a plug with around 25 hours on it.  The center electrode is worn down.  I use stock RX-7 plugs from O'Reilly's Auto Parts.
Evolution of the panel over 6 years.  Steam guages to Dynon, then addition of 2-axis autopilot (Tru-Trak) and Ed Anderson's EFISM.