Chapter 23 - Engine - Research, discussion and assembly


I researched the Mazda 13B rotary engine for almost a year. I followed the discussions in Paul Lamar's newsletter and followed many of the links in his web site to study George Graham's rotary powered Cozy, Perry Mick's Long-EZ and others. I saw Todd Silver's 13B ready to run on his Cozy IV firewall. I looked hard at Tracy Crook's Mazda powered RV4 at an EAA meeting and listened to what he had to say. Next I bought Tracy's book on Rotary Aviation and read all his newsletters and reports. The main thing that attracted me was the reliability issue. There are very few moving parts in the Mazda and, compared with a reciprocating engine, the possibility of mechanical failure resulting in a stopped prop is very low. In the rotary the rotor, as its name implys, simply rotates while many of the parts in the reciprocal accelerate to high speed, stop, then go back the other way many times a second. I know this is obvious, but we tend to accept the reciprocal just because it's the standard. Think about the impact of all these opposing forces for a moment. If the rotary had been invented first, the reciprocal engine would, in my opinion, have been laughed right out of Detroit.

One experienced A&P said it best in the rotary engine newsletter. He said that he'd worked on Lycomings all his life. That was precisely why he was pursuing a rotary solution for his own plane. Think of all the things inside a Lycoming which can spoil your day.. a burned or stuck valve, piston rings, bearings, head gasket, cracked cylinder etc. etc. Not to mention the possibility of faulty parts or workmanship, even on a zero time engine. [as the recent problem with factory new Continental and Lycoming cranks will testify]. Too many Lycomings fail soon after maintenance. By contrast, Tracy Crook flew 850 hrs on a junk yard 13B engine which had 70,000 miles on it when he got it. After dissassembly the engine proved to be without significant wear. Sure, I've heard stories of rotary engines which ran out of oil or coolant or blew a seal. The neat thing about the stories is that they all made it home. One story impressed me particularly, because I saw the disassembled engine afterwards. Apparantly the engine "blew" in an auto race. After the race, the guy drove it home hundreds of miles.

The issue of resale value deserves some discussion. My thoughts there are fairly simple. I have no intention of selling my plane. If, for some unforseen reason, I should wish to sell it in the future, the new owner can swap out the Mazda and install a Lycoming 360A with very little effort - unless, of course, the Madza gains the reputation for durability which I think it will over the next few years - in which case the resale value may be higher with the Mazda installed. Either way, right now I want the reliability of a practically unbreakable, unstoppable engine.

Mazda sold the RX7 sports car with the 13B engine in the USA beginning in about 1986, but those made after about 1990 have engines which were a little improved in design. The intake and exhaust ports are bigger, the oil channels are wider and some of the parts are more robust. The older 13B's work fine, but my understanding is that the later model is better if you can get one. Mazda have recently announced the RX8 with a further improved rotary engine, so its nice to know that the Wankel technology is alive and growing. Of all the contenders, I believe that the 13B Mazda rotary has the best credentials to replace the Lycoming and, eventually, even become the GA standard.


A discussion in the Cozy mail list brought up the issue of risk. I said:
> My main motivation here is not cost - it's safety.
and Al Wick replied:
I too am constructing auto conversion. But it's time for reality check.
There is no way you can expect lower risk by going with an auto
conversion. You have to be motivated by something other than safety to
make that decision. Maybe in a few years it will be safer with successes
and failures shared on net. But it's the fine details of your conversion
that are the risk.

The reality of auto engines is that they are inherently reliable, but you
will end up modifying the systems. Each mod greatly improves your risk.
90% of all the failures are related to a change made to the stock system.
This results in a greater safety risk than the ol' lycoming install.
Of course, he's right, up to a point. This comment caused me to rethink, or at least restate, my motivation.

> My main motivation here is not cost - it's long term safety....
Twelve months from now, I can picture myself cruising along in my Mazda powered Cozy, comfortable in the knowledge that there are no valves to burn out, no cylinder heads to crack, no piston rings to wear, no conrods to come through the cylinder walls, no bearings taking the shock of direction reversal 30 times a second, less vibration to break things etc. etc. I'm well aware that what Al says is true in the short term, but I'm convinced that the Mazda rotary is a much safer engine than the Lycoming in the long-term. Once the peripheral issues are debugged and working, then the risk factor goes way down. Between here and there, I have a minefield of risk to pick my way through.

So, how do I pick my way through the minefield? Follow people who have been through it already and tippy toe very carefully wherever there isn't a precut path. Five years ago, anyone wishing to get to the other side of the minefield had to hop and jump with their hands over their ears. This is not the case today, thanks mainly to Tracy Crook who has debugged, tested and put into production three of the major systems - electronic redundant ignition, electronic redundant fuel injection and drive reduction.

I suspect that low cost motivation often leads to skimping on important, even life critical issues and generates the poor accident statistics. I've seen auto conversions where the engine peripherals are straight from the car. Hoses, clamps, alternator, wiring, etc. etc. I plan to spend what it takes to make this installation safe, even if that costs me more time and money.

This new electronic internet age permits sharing of knowledge. No longer are people working in a vacuum. (Pun intended since vacuum provision is one of the issues I've learned about.) For example, in one way or another, fuel or the lack of it, is the cause of a majority of auto conversion accidents. I asked questions about fuel system design in the rotary and Cozy maillists and learned a lot. Steve Hagan sent me the URL of a paper which discusses many of the issues. This paper makes good reading for anyone, whether they're building the plans fuel system or not.

In summary, I intend to minimize the short term risk by moving very carefully through the minefield. This will take time, but I'm learning a great deal as I go. OK, I admit it. Another angle to my motivation is that I'm enjoying the learning process and I don't like being held over a barrel. We NEED a safer, cheaper, power solution. Certified aircraft manufacturers and contingency fee lawyers have held the airplane engine industry back 30 years. As a result, there is a trend away from certified aircraft and towards homebuilts. I know four other Cozy builders who are actively working on Mazda installations. I know of a dozen others who are waiting in the wings. (oops. another pun).

Hopefully, my small contribution will help us all move us past the minefield and into the realm of inexpensive, bullet proof engines with 3000 hr TBOs, more power, more reliability and better power to weight ratios. Time, and this web page, will tell.


Fellow builder, Bulent Aliev, bought a 1993 Mazda 13B Cosmos engine from a local guy in Ft. Lauderdale who imports engines from Japan. Apparantly the emission rules there are such that these engines only do 30,000 miles or so before the owners have to replace them and buy new ones. The opportunity to get a second '93 "third generation" 13B came up and Bulent couldn't turn it down. His plan was to keep it for a spare, but Bulent offered the engine to me, so I snapped it up. I got the engine disassembled, so I was able see that it's in excellent condition and would probably be just fine as is. However, I took the engine to Chris Harris of Rotec Motorsports for a full overhaul and various modifications which make it better suited for aviation use. The modifications will include 3mm apex seals, "street porting" or polishing and slight widening of the ports, high compression rotors, refacing the end housings, blocking off of emissions holes in the exhaust ports, and sealing off of the oil metering pump (I'll be adding 2 stroke oil to the gas). Chris earns his living working on Mazda rotarys and races a modified RX7 in his spare time. He'd just come back from a national race in Savanna where he "blew away" the Toyota's, Subaru's and Chevy's to come in with first place. It seemed to me that this is a good recommendation for someone to put a lot of care and attention into my engine. Chris is a nice, easy going guy who is prepared to take the time to explain what he does and why. On top of all this, he likes to fly. I asked him to do the work, on the understanding that he will ride with me in my Cozy - thus making his own life depend on the quality of his work. He agreed without hesitation. The 13B engine is practically bullet-proof mechanically, so mechanical failure is not the major concern. Failure of any one of a number of peripherals systems will stop you're prop just as quickly as a thrown rod. The Lycoming has redundant ignition systems. So does the 13B. I will be using Tracy Crook's EFI system which has a manual backup. I will have dual fuel pumps. All hoses, pipes, fittings and wires will be aircraft quality. I plan to spend much time and effort in making the oil, water, fuel and ignition systems as bullet proof as the engine itself.

Once the rebuild is done Bulent and I will be working together on all the peripheral issues, such as the reduction unit (also known as PSRU or redrive) and Electronic Fuel Injection (EFI) system - both supplied by Tracy Crook, the exhaust, intake, oil and cooling systems. The cowling, which I will be making, will have much reduced "side cheeks" and a "boat tail". We expect weight and balance to be very close to that with the Lycoming 360 and available power a little better. Based on Tracy's research and comparison with Lycoming powered RVs, ecomony should be on a par with Lycoming.

While it has done well in one RV4 and a few EZ aircraft, the Mazda 13B is unproven in the Cozy IV. Someone has to be first, just as someone had to be first with the Cozy IV itself. My only problem with all this is that I'm further along than any of the other Mazda inclined Cozy IV builders and will probably end up being the test pilot for the group. Maybe I should slow down a bit on construction and let someone else assume that honor!


Chris Harris of Rotec Motorsports took these pictures for me while assembling the engine: (click to enlarge)

I went down to Chris's shop to watch the final steps of assembly. Chris added a low profile oil filter mount and put the oil pump and counter weight in place. Next came the peripherals items. It seemed to make sense to at least start with the stock items that are used in the car, then decide what has to be modified or replaced. Chris agreed to supply oil coolers (the small twin ones from a '93 Turbo II - I think these will go nicely on either side of the radiator), a radiator, alternator, starter, fuel pump, smog pump, inlet manifold and exhaust manifold. I'll need to get the stock plugs and oil filter.


the stock '93 water pump, alternator and in-tank fuel pump Finally, on 9/21/00, Chris Harris delivered the engine, complete with all sorts of accessories. I hadn't been able to get down th Ft. Lauderdale to collect the engine, so he went to the trouble to load it in the truck of his car and bring it to me. He'd brought me a smog pump from a 2nd gen engine, but I had the original that came with the '93 engine. It was interesting to note that mine was MUCH lighter and smaller. My bench is now full of engine bits. And the stock '93 oil coolers I thought building the plane was a challenge! Screwing this lot together is going to be the really tough part. Chris has also promised to get me a transmission bell housing and a couple of exhaust manifold studs that seem to be missing. While we were chatting, Chris mentioned that he and his racing buddies get an exhaust kit that they fabricate the exhaust system from. Apparantly it comes with a flange and various bends so you can make up the exhaust system you need. I'll research this and report.


The EC2 computer from Tracy Crook arrived on the same day as the engine. It comes with copious instructions and a fancy control board. "Oh look", says I, "It has volume and balance controls." Hmmmm. I think I have a lot to learn. Later I read that the EC2 needs different programming to handle the timing of 3rd generation 13B REW models. Tracy confirmed this and promised to "get busy on that version of the code".
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