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Objective Engine Discussion


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I wish to begin gathering UNEMOTIONAL, tangible pros and cons on engine choices for my Cozy Mk IV. I won't be ready to begin working on my firewall for about 12 more months.


As I see it today I have the following engine choices:


Lycoming 360 or XP-360

Mazda 13B or Renesis

Jabiru 5100

Subaru ???


My background:


- I don't know squat about engines - all I know is that they are big, heavy, expensive, you add gas and oil, and it makes the big fan go :)


Issues I DO NOT want to discuss at this time:


- Resale value

- Religious discussions of using "standard" aircraft engine vs. auto conversion.


Here are some questions I have at this time:


1) Can I anticipate any mods to the airframe (probably the strakes?) due to engine choice? I'm guessing the only effect might be the plans fuel system if anything.


2) Fuel - Can the XP-360 use autogas? Can the listed auto engines use 100LL? For those of you using an auto engine - how do you get autogas to your plane?


3) While I hope to learn a lot more about my engine, whichever I choose, I don't expect to learn enough to do all work myself when it comes to maintenance. Obviously, the XP-360 can be repaired at most airports. For those with auto engines, what options do you have for repair?


4) Living in Denver, I expect to fly above 10,000' quite a bit. Am I going to want a turbo auto engine? What is equivilent for the XP-360?


5) I'm most likley going to want dual electronic ignition (no magnetos). If I went with the XP-360, how different from the Cozy plans will the engine install be?


Here is my current list of Pros/Cons for XP-360 vs. auto engine:




Pros: Fairly standard, mostly plans install. Improvement over true Lycoming. Get repairs at most airports. Get 100LL any airport.

Cons: Expensive repairs.


Auto Engine


Pros: Newer technology. Much cheaper repair. Cheaper parts at local auto parts store.

Cons: Smaller knowledge base. Huge deviation from plans install. Might need custom cowling. Where to get repairs? Where to get gas?


Comparisons that I see as a wash:


- Initial installation costs will end up being about the same.

- Installed weight/CG will be about the same.

- I know nothing about either so I have the same amount to learn.


I'm sure I'm missing some things here (and that is why I'm asking for help).


Again, please keep answers and suggestions as objective as possible. I don't want to start religious battles with this thread.


Thank you all for the help.

Rick Maddy

Denver, CO

Cozy Mk IV #824 - Chapter 18


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Continental TSIO360 a b c or d


pro good for altitude

pro cheep (i paid 7000)


will change turbo 1500 or ??

lightspeed electronic ignition 2000

Sell mags 12 to 14 hundred

exhaust ???


con 30lbs heavy

diferent installation

maker wood dust and shavings - foam and fiberglass dust and one day a cozy will pop out, enjoying the build


i can be reached at



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Here is what I found with my install:


Lycoming IO306A3B6D


As is, there is plenty of room to remove the filter in the stock location. No adapters required.


Removed the dual 'T-Pack' mags and replaced with Lightspeed dual electronic ignition, crank sensor. This also serves as an oil seal retainer.


Went all electric, installed an SD-8 backup generator on the Vacuum pad location.


Had to make a decision to either use a Nippondenso alternator (I would use one from a tractor, but others are buying them from salvage yards) or to spend more money for the B&C. I made the decision to spend the money for the B&C.


Bought the lightweight B&C starter, and have dual Hawker 17AH batteries. Wired per Aeroelectric Z-13 w/ second battery.


Bought engine mount from Jeff Russell, it bolted right up. Bought IO360 cowl from Jeff also, but this cowl was made to fit a 'C' sump. Mounted cowl rearwards 3-4 inches to allow clearance for intake pipes, would have been better to mount cowl in stock location and add blisters.


Exhaust system from wherever it lists in the newsletter.


IO360 requires high pressure boost pump package, I bought mine from Airflow performance. This is expensive compared to facet pump. Also bought new injector lines from Airflow. They are only about $10 more than the component parts, and everything is SS and silver soldered.


Baffling was different from plans, but Angle valve engine has big square jug fins on it, and I thought the baffling was quite straight forward to make.


8 inch prop extension from Judy Saber, Sensinich prop (bought used from Nat). 13 row Positech Oil Cooler. Throttle quadrant and cables from wicks.


Plusses: Everything except Cowl off the shelf and bolts right up. 200 hp plus whatever gains from electronic ignition. Cost from Modworks was $10K for basic engine.


Negatives: Starter and boost pump pricer than standard Lycoming or automotive installation, I think there is a kit to use an automotive starter, but I wanted a bolt-on solution.


I think that there will be more successful automotive installations where the information and learning is shared, and people will have better resources for components such as intake, exhaust, ignition, fuel, and redrive systems. I abandoned the rotary when I could not identify an exhaust system or intake system that was developed, and when there was no agreement on how to mount a rotary. I still have three base plates sitting in the garage, along with three core 13b's! I have an associate who is taking delivery of a subaru 3.3l this next week, and will be following that engine closely. In the meantime, the Lycoming is a bolt-in solution that is ready to fly.


To go through your questions by number:


1) If you are considering automotive fuel injection, install a return line in each tank. This can be plugged if you don't use it.


2) I know people who are flying with 93 Octane Amoco Ultimate in their high compression Lycoming engines. I have seen recommendations to mix some 100LL with 93 occasionally. Also many arguments against mogas. This begins to smell like a religious argument. Mogas users typically haul fuel to airport in 5 gallon containers. Some airports get excited about this practice, some airports have mogas available. I plan to fly with 100LL, and may consider a blend inthe future. But not until after plane and engine are well proven.


5) EI Installation was very clean. I chose to install both boxes on engine side of firewall, with a big hole for connectors they could be installed on passenger side also. Approx 12 pound weight savings over T-pack mags.




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<... UNEMOTIONAL, tangible pros and cons on engine choices ...>

That's a TAAAAAALL order, my friend :)


<... I don't know squat about engines ...>

You didn't know squat about building plastic airplanes when you bought your plans. You learn as you go. Same with engines. A minor issue IMO


I have been following the engine discussions (both religious and rational) for several years.

As to your specific questions:


1) No airframe mods of any consequence. Fuel plumbing is relatively trivial (ask John S). Firewall (mount pads) don't seem to be a biggie.


2) Pretty much any engine can use autogas. I mix half autogas in my IO-360 (autogas in injected certified engines is regarded as major heresy - but for reasons that seem much more religious than rational). It's your engine. Burn moonshine if you want. Most Lycs (like mine) will cease to be certified if you burn autogas, but why do you care? If you do get a Lyc (or XP), you're going to run it out. If you sell it, it will re-certify when it's rebuilt. Virtually all auto engines can burn 100LL, but it's bad for them (lead deposits, etc).


3) You will learn a LOT about whatever engine you choose. Even if you don't learn enough to do ALL the work yourself, you'll still know a LOT. You will find that auto engines are DRAMATICALLY more economical to maintain (I recently posted a quick and dirty comparison on the Cozy list). They are also better built on account of they're water cooled (read uniform cooling) - an order of magnitude closer tolerances, etc that make for far superior reliability and engine life. From the 70s until the 90s, auto engine life expectancy has increased from under 100k mi to something on the order of half a million. Thank CNC mills and EFI.


4) It's MUCH easier and MUCH cheaper to hang a turbo on an auto engine than a Lyc. Turbo'd auto engines are probably a LOT more reliable than turbo'd Lycs.


5. Trivial. If you're very cautious, you might want to spring a bundle for a backup alternator on the vacuum pump pad. I can't see that passing a cost-benefit examination, but it's a value judgement. All electric is GOOD. Vacuum pumps SUCK (pun intended) - they fail like Chicagoans vote - early and often.


6. XP-O-360: To "expensive repairs" add "excessive"


Auto engine: Smaller knowlege base will be much larger by the time you need to make a decision; Huge deviation from plans will turn out to be relatively trivial - custom cowl is certainly trivial - ask John S; You won't need nearly as many repairs as O-360, and for a fraction of the differential in cost for a particular incident, you can get the local ??? mechanic to make a service call. For the most part, you'll be doing repairs yourself - trust me on that - you'll be competent and confident; Gas is a relatively trivial issue - I have (4) 5-gal cans that fit nicely in the trunk of the car. I grin like my face will break every time I fill up for about 2/3 what avgas would cost (> $40 per fill-up savings). Fueling and grounding procedures are an issue (at least in the winter when it's particularly dry). Read up on that in the archives (be warned - there's a lot of folks will tell you a lot more than they know on this issue). I aim to get a small trailer with a 50-gal tank, electric pump, actual nozzle, quantity pumped and all the trimmings. Expect to pay for it in maybe 10 tank fulls (less than one summer). Auto gas is not as common at airports as it was 15-20 yrs ago, but it's there if you look.


Things that wash: You've got that pretty much nailed.


Things missing: We ALL are missing stuff. Good news is that you have quite a while to study up and make an informed decision. Don't commit to ANYTHING until you absolutely HAVE to. Keep on listening and learning and make YOUR decision for YOUR reasons.


Just a theory ... Jim S.

...Destiny's Plaything...

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>Fuel plumbing is relatively trivial (ask John S).

Agreed, once you figure out which way you're gonna do it.


>custom cowl is certainly trivial - ask John S

Trivial isnt a word I'd choose. Fun, yes. Messy, definately. It took me about a month to build both cowls, and I had lots of fun doing it. Not a big issue, but not trivial.


>For the most part, you'll be doing repairs yourself

With respect to the periferals, perhaps. If the engine croaks internally I'd probably just get another one (a Renesis?), get the first one rebuilt by Bruce and then keep it as a spare.


I pretty much agree with everything else Jim said. (a first).

I can be reached on the "other" forum http://canardaviationforum.dmt.net

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<... respect to the periferals, perhaps. If the engine croaks internally I'd probably just ...>

Actually, that was what I was talking about. There's no reason for anyone to do the internals, although folks talk as if a Mazda is really REALLY simple and easy to do - once you've done one :)

I'll be able to speak to that later on ... Jim S.

...Destiny's Plaything...

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I can answer some of you're questions as they relate to the rotary:


> 1) Can I anticipate any mods to the airframe (probably the strakes?) If you go with a Mazda you'll need either returns to the tanks or a central sump. The returns are no big deal. As someone else said, just plumb them in and plug them if not used.


> 2) Can the listed auto engines use 100LL?

The 13B will run fine on 100LL, but I understand that the plugs will

accumulate lead and need changing or cleaning every 25 hours or so.


>For those of you using an auto engine - how do you get autogas to your plane? I plan to pump it from my car fuel tank.


> 3) For those with auto engines, what options do you have for repair? I have a Mazda racing shop nearby. They are helping me with the engine configuration and I'm learning from them as we go along. Most repairs will involve periferals which I will be able to change out myself. If the engine needs internal repairs I'll get another (an RX8?) then send the old one to Bruce Turrentine. This way I'll have a spare.


> 4) Am I going to want a turbo auto engine?

I would think so. A turbo is a good way to quiet the 13B exhaust anyway.


> Pros: Fairly standard, mostly plans install.

I don't think enough emphasis has been given to this point in other

responses. I'm acutely concious of the fact that my engine is an original installation. Greg Richter did "something similar" and there are quite a few RVs with "something similar" (if backwards). There are quite a few similar installations being built, but there are no IDENTICAL installations to mine flying. There will be quirks and bugs in my setup and I'll have to do a lot of testing before I'm comfortable enough to fly it. If you install a Lycoming or XP-360 you're pretty much copying EXACTLY what hundreds of others have proven. Big difference.


Eventually there will probably be 'standard' subaru and mazda firewall forward solutions. At this stage you (or someone you pay) have to invent stuff like intake manifold, exhaust and cooling systems. It's challenging, interesting and I suppose it's what "experimental" is all about, but it is also full of potential pitfalls simply because there is no standard.


Of course, we'll never get to a standard alternative if no-one innovates.


As they say - you pays you're money and you takes you're choice.


I hope this helps,


John Slade

I can be reached on the "other" forum http://canardaviationforum.dmt.net

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