Mazda 13B Conversions


FlyRotary Web page -- this seems about the centre of the Web with respect to flying with a rotary powerplant. It has links to many other Web pages. There's also a FlyRotary mailing list... subscription is via the Web page above.

If you are considering the Rotary, I strongly encourage getting Tracy Crook's book on the conversion process and also signing up to the web discussion groups.

Not mentioned at FlyRotary:

Ed Anderson's Mazda 13B installation in an RV-6A

Ed wrote to the RV-list:
Was running the engine at 5000 RPM getting 2300 RPM static thrust which the prop manufacturer stated indicated a strong 165HP. No dry sump, using a made up oil pan from Ross Aero which simply rotates the oil pick up so it picks up oil from the new orientation - works fine.

I clobbered up a fuel injection system using auto parts including an EFI computer that you tune from a laptop computer while engine is running. The EFI computer is made by HALTECH who have been around in the auto hot-rodding arena for a while.

The engine is mounted on a reworked RV-6A Lycoming mount. Basically kept all the attachment points, nose gear and reworked the engine attachment area to match the Mazda engine attachment points. (Dave Leonard) wrote to the RV-List:
I'll make comparisons to installing a rebuilt Lyc. To put in a Mazda in an RV, you could expect to do the following:

1) find and buy a used engine Time - availability is comparable but Mazda=$400-$800 You fill in $$$ for the Lyc.

2) Have the engine torn down and inspected and rebuilt.  Mazda $3000 for mostly new parts. Lyc = $$$$$ Like with the Lyc, some will feel comfortable doing this themselves. There is a great video available for the Rotary showing this process (as I'm sure there is for the Lyc too).

We are the same so far except for cost. Has it been easy?  Now here are the extra things you must do for the Mazda conversion, all detailed in Tracy Crooks conversion manual...

1) Disable the stock oil injection - a simple process that takes about an hour as part of the rebuild (either by you or someone else).

2) Older engines will require an easy mod to one of the coolant gaskets.

3) Now, to give yourself 10-20 extra HP, you could have the intake ported for several hundred $, but we are still way under what you have spent for the overhauled Lyc and it hasn't been any more difficult at all.  How does this affect reliability? Well, ported cars putting out 350 hp with no oil injection mod are known to blow apex seals. However, at less than 230 hp in the aircraft with the oil mod it is a non factor IMHO, but no one can say for sure.

4) You will have to modify or rebuild your engine mount (yup, this is a big pain). However, one builder just installed an engine using an adapter that fit directly on the stock dynafocal. I am hoping that the machinist who made it will make some more of these sub-mounts.

[When I emailed him about this, Dave replied:]
That installation was done by a builder in Florida. It is not flying yet, but W&B turned out perfect. I talked to the machinist who said he would do the same mount for me for about $200. However, it requires a custom (extra short) PSRU (which he can also supply) if you want to use the stock cowl.

I have decided to use one of the more tested PSRU's (which are a little longer) and have the mount re-built. An RV-4 builder here (also doing a Rotary conversion) has his mount rebuilt and it looks really nice and wasn't that hard.

5) You will have to supply fuel, spark and air. Tracy Crook makes an engine controller which supplies electronic ignition based on the stock crank angle sensor. It also provides cockpit adjustable electronic fuel injection. There are two completely independent computers which can each run the two injectors and two spark plugs in each combustion chamber. There is also a third limp home mode. The whole system costs under a $1000. There will soon also be a monitor showing Fuel flow (solving the EFI fuel flow problem) Total fuel, MPG, RPM, and MAP.   Try finding that for a Lyc!!! Supplying air is a little tougher.  Tracy supplies instructions on making an intake from stock parts, and a couple of vendors are supplying bolt on manifolds.

6) Exhaust needs to be made custom (so far), a couple of suppliers do this for RV's as well.

7) Cooling is a hassle. This is where time and weight will be gained or lost. I haven't heard of anyone who never got it to work. But at least you wont have to do any baffling. You also get the advantages of liquid cooling (no shock cooling, less cooling drag possible) and disadvantage (another system to fail) and still stay at the weight/CG of the designed engine.

So, what's the bottom line? IMHO An easily modified uncareful installation will produce about 160 hp. Now be careful with the installation, tune the intake and exhaust, add a pressure phlem, and maybe some street porting and get up to 210 hp. The installation will weigh a little more or less than the Lycs (remember, the 320 and 360 are only about 10# apart). There should be plenty of space in the cowl of an RV6 or 8 to add turbocharging and get around 250 hp. (The stock turbo in the car is rated at 285hp.)

Yup, it takes a little extra effort and time, but in the end you will spend less for a considerably better product. Some guys have gone to a lot more effort than this to install a 200 hp IO-360 in their RV-6(A).  Is it worth it? Is it worth it to build an RV instead of buying that Katanya, or Cirrus, or Cessna? I think so. Just like building the RV, it doesn't take an engineering degree or engine expertise (I have never done more than change my oil), just a little extra love.. :-)

Someone asked about justification for 2000+ TBO. Theoretical? Yes. But not like someone calculated it out on a CAD machine.  One engine in a gyro is at 1700 SMOH and going strong. Tracy Crook ran his first engine for almost 900 hrs and had essentially no measurable wear, let alone reduction in hp, compression or increase in EGT's. He also burned no measurable oil between oil changes (every 50 hrs). Ever heard of a Lyc that did that? A few other engines are in the 500 hr range (and counting) with similar results. The oil injection mod is critical. If anyone owns an RX-7 that you want to keep around for 3-4 hundred thousand miles, consider making this mod in your car.

Someone else mentioned resale value. Good point. Personally, I would much rather have a proven rotary installation over a Lyc any day.  But I am the minority and will be for quite some time. My RV is a life long project/investment. I don't plan to sell for several reasons (liability, loss of my baby, never want to be this consumed with a hobby again etc..) But if you think there is a good possibility you will someday sell, looks like you are stuck with a Lycosaur.

Now, the ramblings you have just heard are those of a bookworm who is really just beginning his project (gads). Please don't take my word for any of this. I have found my engine research and tinkering to be as rewarding as working on my RV. (talk to me again in a couple years ;-). The research really isn't that hard. The only reason that I did it was because I was off in Japan for six months with nothing else to do. But now I have seen the light and it goes hmmmmmmmmm instead of boing boing boing.

RV-List message posted by: "Ed Anderson" <>

I got Van's Concial mount and had the aircraft engine mounting pads cut off and a motor mount welded to the nose gear and firewall pads.  I had the face of the prop flange off set 5/8" to the left to counter the opposite rotation of the prop. Others have not put any offset into the mount and apparently it has no major effect. At least one individual use the regular aircraft mount and had a submount for the engine which mounted to the Lord mounts. So, it takes a little thought and some welding, but clearly not a major hurdle.

The back of my engine sets 8" from the firewall and my empty C.G is at the foward C.G limit. When I am on board and fully loaded with fuel the C.G. is almost right over the center of lift or approx 25% back from the leading edge of the wing. I used the stock cowl (I think it was the old none constant speed cowl - the longer of the two that Van then offered) and the engine fit under it just fine.

Kitplanes August 87  "Gearing for Autopower"   p46-49 Shows internals of Ross PSRU and their 13B installation in a Mooney. (Also the first time I heard of Geschwender's work)

Kitplanes July 90  "Fly by Ross"  p76-78 Shows Ross'  PSRU, shop, 13B Exhaust baffles (really neat)

Kitplanes October 95  "Zen and the art of Alternative Engines" Part 1 p26-35 Tracy Crook's Conversion

Kitplanes November 95  "The Rotary Alternative" Part 2 p35-42 Tracy Crook's Conversion Part 2

Kitplanes October 96  "Living With A Rotary" 1 p75-85 Tracy Crook's Conversion- 250 hour follow up.


Subject: Mazda articles in Contact! Magazine.
Date: 6 May 96 11:56:21 -0500

A search through our chapter library's set of Contact! magazines reveals the following articles of interest to those looking into Mazda Rotary engines for aircraft use.

Issue 1:  "Alternative Power for Experimental Aircraft" Chris Ross.  Includes an exploded view of a Ross planetary gear PSRU as well as info on a Mazda BD-4, a Mazda Lancair, a Mazda T-18, and reference (in a table of Ross installations) to 3 Lancairs, 1 Long EZ, 1 RV-4, 1 Cozy, and 2 Velocitys.  It also includes 1/5th scale drawings of a 13B with a ross redrive on it.

Issue 1:  "Flying a Mazda Rotary"  Neil A. Kruiswyk.  Mazda Lancair 325.

Issue 5:  "Mazda Rotary Powered Super Cuby" Medford A. Bony.  Mazda 12A with a belt PSRU in a Super Cuby

Issue 23:  "Converting the Mazda RX-7 Rotary Powerplant"  Jim Mayfield.  13B with Ross PSRU on a 2 place gyrocopter.

Issue 25:  "Mazda 13B Powerplant Installation in a Long EZ"  Ron Gowan.

Issue 25:  "More on Mazda Rotarys"  Ed.  Lists several other known Mazda conversions.

Date: Wed, 23 Oct 1996 10:29:06 +1300

The way you get 200 HP is move the intake ports from the sidewalls to the center housing. It then becomes what is known as a peripheral port. It is a little more complicated then a simple two cycle port job. You also need to do a little grinding in the water passeges around the spark plug area and use long intake runners.

Mazda did not do this on the street engines because it ruined the low RPM torque which you don't need in an aircraft engine.

There was a one rotor running at Copperstate on a test stand with a muffler that was very quiet. Prop noise is so high that a muffler on an airplane makes less of a difference than one would at first think.

The definitive book on the rotary is simply called "ROTARY ENGINE" by Kenichi Yamamoto published by Toyo Kogyo Co. Ltd. (Mazda) in 1969. This is a highly technical book chronicling the development of the wankel by Mazda. Kenichi is an engineer and has risen to be CEO of Mazda.

Another technical book on the Wankle rotary engine is; "The Wankel RC Engine Design and Performance" by R.F.Ansdale Published by A.S. Barnes & Company Lib of Cong 69-18692

Paul Lamar


Finn Lassen wrote: All I have are some old numbers, subject to the inaccuracies of my bathroom scales.

RV 3 Weight & Balance data

Engine mount           10
Engine mount plate      5.5
Engine mount&plate     15.5?

Engine: w/counterweight, w/o flywheel, w/o waterpump housing, w/o manifolds, w/o any accessories, w/o oil pan.
                        170 (c.g. at intermediate housing)
Waterpump w/housing       7

Water radiators (ea)    5 (7? with water)

Engine mount/plate       16        6"?         96
Engine w/redrive        229       16"        3664
Alternator                9        7"          63
Starter                   9       26"         234
Crankangle sensor         2 ?      6"          12
Oil filter                1        6"           6
Oil cooler                7       15"         105
Oil pan                   6       14"          84
Carbs                     5       15"          45
Intake manifold           6       15"          90
Exhaust                   6 ?     14" ?        84
Ig Coils                  5        6" ?        30
Radiators                10       25"         250
Coolant                  14       20" ?       280

George Lendich wrote to The AirCraft Rotary Engine NewsLetter: From previous posts, my understanding the 13b can come in from 315 lbs to approx 350 lbs depending upon the variables.

John Slade wrote to The AirCraft Rotary Engine NewsLetter: I weighed my '93 13B REW and accessories on a UPS scale as follows:

Engine less oil pan        178
Smog pump                    7
Starter                      8
water pump                  10
Alternator                  11.5
total                      214.5

Add in the redrive at 35 lb, the mount plate at 5 and about 5 lb of water and we come to about 260 lb for the 13B.
[Plus oil filter, cooler, pan, radiators, intake & exhaust manifolds, ignition... for another 46lbs: FvdH]

For comparison, here are weights of Lycoming engines I found : I have no idea what accessories are included in these weight, and the web sites they come from are now no longer available.

horsepower weight from Dry Weight from Lycoming's page
O-360-A1D, A3A 180 285 265
IO-360-A1A 200 320 293
IO-360-B1B 180 295 270
TO-360-C, F 343
TIO-360-C 348

Tom Mayer wrote to The AirCraft Rotary Engine NewsLetter:
Parallel valve 0-360s weigh 270 to 275, without starter and alternator.  The parallel valve engines are 180 hp engines. IO-360 angle heads weigh 293 to 299 w/o starter and alternator. The heavier weight usually is due to an aerobatic crankshaft. An updraft TIO-360 weighs 343 to 348. Those figures from a 1998 Lyc spec sheet.

A Lyc engineer I talked to about turbo normalizing matters giggled when I quoted these weights to him. He thought the angle head weighed at least 325 "in usable form".

Typical installed weight of an IO-360 angle head of 200 hp, with electrical goodies, will top 350 pounds easily.

Given all of this, for a comparison let's take Lycoming's dry weight, add an alternator and starter to it (say 20 lbs). In both cases, we'll add 5 lbs oil.

horsepower Total weight
O-360-A1D, A3A 180 290
IO-360-A1A 200 318
IO-360-B1B 180 295
TO-360-C, F 368
TIO-360-C 373
Finn Lassen's 13B ???? 330
John Slade's 13B ???? 311

From the above, it looks like a 13B is 20-30lbs heavier than a standard O-360, a little heavier than an IO-360, and quite a bit lighter than a TIO-360.