Hello Folks. 

My 13-year-old and I are looking forward to eventually choosing a Zenith kit but I believe we are close to picking a powerplant.  I'm considering purchasing an AM15 for most likely a Cruzer, either going with the 117 hp or the 131 hp low profile option. I'm still trying to decide if 14 horsepower is worth $4k.

My son will be using this aircraft to obtain his PPL so simplicity and reliability are a must!

Comparing to the competition, here are my initial thoughts: 

I can appreciate the lack of plastic parts and tubing with the Suzuki/AeroM.  Engine plastics are fine for an economy car, mostly cruising at low engine loads of 1100-2250 RPMs, but probably not a good fit for high-RPM, high-engine load applications. 

I don't doubt the engineering of one of the most reliable automakers in the world, but I'm not 100% sold that same engineering can be directly applied to an aircraft engine. 

I have personally stripped down engines to access and clean intake valves due to carbon buildup that happens from direct injection, I would like to avoid D.I. if possible.  D.I. is also complicated to run properly and can be unforgiving if sensors or tuning are bad.  I've also run into issues with catch cans and pcv/emission systems creating tuning issues as well.  Fuel systems must be spot-on for the high pressure systems also associated with D.I.  It would be nice to not have to mess with the complexity associated with a header tank and additional fuel lines. 

The new AeroM carbon fiber cowling looks pretty cool and lightweight as well, it seems like it can be made to look pretty sharp.


Most importantly, Mark Ketteing has also been very responsive with excellent communication and follow up.  His replies are honest even when they don't fit his invested solutions. 

Views: 2610

Replies are closed for this discussion.

Replies to This Discussion

I would like to add this just because it is stated incorrectly, the carbon build up in direct injection can happen in the cars, we run ours overboard just like a typical aircraft engine, avoiding any of those issues. We have over 650 engines in Zenith aircraft, I don't believe anybody other than maybe Rotax has that number, the tuning has been perfected as it is part of the flying and testing we did many years ago, which is why many are flying with hundreds and hundreds of hours successfully, at this point in time I believe AM has 2 flying? (correct me if I'm wrong) I would recommend talking to flying customers. I'll also mention no one has flown with an AM cowling at all to my knowledge, so no cooling has really been tested to this point, which is all great if you want to do the testing, but my understanding is that you want to use this as a trainer and you are discussing reliability when there isn't much information to truly go by. 

I really recommend reading up on a header tank and its usefulness, we have also replaced over 15 UL Fuel Systems. 

I'll also add that if reliability is an issue, a 2 spark plug one coil setup - the Honda has one spark plug per cylinder. 

If a coil fails you lose less than half of your power, that is not the case with the Honda, there are many safety factors to think about in this regard over the basics. 

The rational on the plastic parts, it is lighter, it provides cooler air to the engine, under hood temperature of a car is far greater than in an airplane where there is air flow all the time. Is there any other reason of concern? Also, as far as RPM, we typically cruise as do our customers anywhere from 3300-4000 RPM - much lower than other auto conversions. 


Thanks for the reply, Alissa.  

Good point about a single coil per two cylinders, although losing one cylinder or two seems like a bad scenario all around with a four-cylinder engine. 

Those were my initial thoughts and who knows where I'll be two years down the road when it's time to buy a motor.  Maybe I'll be in a better position to simply purchase a 175lb UL350is at that time.

Thanks again for the quote!

Not an ideal situation either way, but having the ability to have the power to get you to an airport or home is important, we have never had a coil go bad, but that safety margin is there. Just talk to people who are flying this setup!

A UL has its own set of questions and totally changes to air cooled. Making a list of what you want is important. I do believe UL has about 300 engines in the US, I'm not sure the amount in Zenith - but they also have a system that is flying with people you can talk to. 

My only recommendation is that you do that and lay out your list of pros/cons and what you want and address them or ask why or why not. No matter which direction you go I wish you the best during your build, and are still here if you have questions. 

As for the plastic parts comment, again we're talking about an engine not specifically engineered for the environment that it is being utilized in.  An overheated car engine doesn't melt its plastic/nylon intake manifold, but I worry more about the degradation of the plastic wiring looms, plastic hoses & fittings, sensors, etc... 

Your Honda engine was designed with a coolant system that has a series of electric fans to keep air moving through the radiator, this is vastly different than the Viking cooling system.  The Honda integrated exhaust manifold is very "cool" but again, that's more heat being retained in the engine.

Taxing with a heat-soaked engine can be a problem, even with an aircraft engine.   The 912's in the Sport Cruiser at my local airport don't fly on terribly hot days at our altitude because their radiators can't transfer enough heat to prevent high engine temps. 

Plastic parts don't radiate heat as aluminum parts do which is good and bad.  Theoretically, an engine head insulated in plastics and sound deadening material like the Honda valve cover and intake manifold is going to run hotter than an engine with an aluminum intake manifold and valve cover.  The aluminum parts will act as a heat sink to the surrounding air while the plastics will act to insulate the engine.  

My point is not to debate or prevent Viking engine sales, but to suggest that non-scientific product claims are redundant and detrimental to purchasing considerations. 

The Viking engine is a very attractive solution, there's no need to "over promise and under deliver". 

At a 10,000' density altitude, atmospheric pressure is only 10 PSI, that's a 30% decrease in the number of molecules bouncing off a radiator.

This will apply with any engine, air cooled, liquid etc. We have tested all of our engines at every altitude, with the supplied cooling system - it has NEVER been an issue. That is the point in testing to ensure just that - we just got done doing this testing (in video) flying at 10,000 feet pulling 52 inches of manifold pressure and running perfect temperatures across the board. That is not a normal aspirated engine, but an engine that can produce sea level rated horsepower to more than 10,000 feet and still not having any issue with cooling. It all goes back to your original statement talking about safety and reliability, that all comes with hours and testing - which is there. 

I don't think you would be in the market for any automotive injected engine with the rationale above. The fuel injectors are all "plastic" on the UL, the Viking, the Aeromomentum and the Rotax. As far as plastic wire loom, etc., the Rotax 915 is the king of rubber and plastic parts under the cowl.  

It is very hard for anyone to actually win an argument that Honda did not think stuff through when they designed their engines. Car engines sit under the hood in Arizona rush traffic and last a long time, with no maintenance whatsoever.  

If the 1,000 Viking engines are not proof enough that it works, with over 600 in Zenith (with every bit and piece tested - on our OWN aircraft, flown all over the USA - at every altitude and temperature) every Viking engine uses a Tefcel wire loom and high temperature nylon loom. Also, we are way past the "theoretically it is this way or that way". Our engines fly every day all over the world with tested products, not just theory and customers have stated that we overdelivered from what they were expecting, we never over promise and I have lists and lists of people that can discuss that with you. 


My only point is to explain the misnomers, not debate either - but to state a theory as though it is fact is not valid. 

The Sport Cruiser is air, oil and coolant cooled.  Different animal altogether.  

All engines have their inherent differences, but there are a select 5 or so that have a proven record in a Zenith, or at all and most all of them show up to the Zenith Homecoming every year where they all fly their aircraft in. 

My biggest point is you referenced reliability and safety while discussing other engines that don't have a track record as of yet, and maybe that will happen in two years. The comparison between two items that are vastly different. The great part of the Zenith community is the ability to choose as you see fit, but I just wanted to ensure you understood the different things you were looking at from any and all outside sources or right from the manufacturer. 

In fact, I think it is a fun conversation to see all sides and points of view. The goal is never to be right and only to answer questions that maybe isn't fully understood, in which case more questions can always arise. 


"It is very hard for anyone to actually win an argument that Honda did not think stuff through when they designed their engines. Car engines sit under the hood in Arizona rush traffic and last a long time, with no maintenance whatsoever.  " 

This is your claim that continues to bother me!  Honda 100% did not plan for people installing their auto engines in experimental aircraft.  Honda's auto engines are designed for the service life of the car, not for an aircraft.  "No maintenance whatsoever" is a deceptive statement.  Honda has part failures requiring the occasional new fuel injectors, coil packs, alternator, ECU, etc.. They also have issues regarding oil leaks, misfires, oil dilution, and a hundred other Honda Technical Service Bulletins for various failures and issues.  Just like any other vehicle maker, Honda runs the numbers against failures/repairs, and liability, and then comes to acceptable conclusions regarding part failures.  These conclusions do not consider the risk associated with an aircraft engine failure!  Honda engines absolutely do require scheduled maintenance and sometimes unscheduled maintenance.      

Honda has absolutely no part in the re-use of a salvaged engine in a homebuilt aircraft!  To suggest or guarantee that a homebuilt aircraft with a salvaged engine will be just as reliable as a car is dangerous, especially one installed by a novice outside of a Honda factory rather than a certified Honda mechanic.

Thankfully you've stayed off Honda's litigation radar, I would work to keep it that way. 

Mark Kettering at Aeromomentum doesn't even come close to claiming that his engines are reliable because of the cars they were engineered to power.  He makes a strong point that his engines are new parts, re-engineered, and modified for aircraft. 

If I buy a Viking engine, I'll be happy knowing that I've bought a salvaged Honda motor and nothing



All of these things you mention, apply for ANYONE of the engines you purchase. Our engines do require very little basic maintenance.We know this through experience 1,000's and 1,000's of fleet hours and testing. All we can speak to is our experience and what we know, and I didn't want you to have a misconception from the get-go, like you stated carbon build-up. Which isn't an issue and I explained why. Experience, something that isn't being discussed, if you would like to test other engine, of course go-ahead - was simply explaining the truth. I really suggest you attend Zenith Homecoming one year.

There are many statements mentioned here that are inaccurate. I don't think there was any real intention to get answers but instead attack and spread inaccuracies. 

This is getting repetitive, I apologize for the time wasted.  Please understand that my attack isn't on the product with its acceptable pros/cons but rather the messaging in your responses. Between the two of us (we're the only ones communicating here), I would strongly suggest that you know your audience a bit better and/or adjust your online messaging regarding your product.  Maybe it's my decades of IT sales experience combined with my past experience growing an aftermarket turbo kit company.  I have experience with IT services litigation combined with the fun experiences of customer's blowing up their engines with poor tuning or too much power.  For me personally, you've raised a few red flags as a business operator in how you communicate about your product.  

For example, you mention my misconception about carbon buildup.  There's a bit of half-truth to how you've stated: "we run ours overboard just like a typical aircraft engine, avoiding any of those issues".  Avoiding "any of those issues" is a very broad statement.  You can vent crankcase gases to atmosphere or use catch cans to avoid deposits on the intake valves, but you actually can still end up with significant dry carbon build-up (not sludge) on D.I. intake valves.  Depending on the valve overlap, lift duration, and some aggressive timing (which D.I. allows for), you MAY end up with carbon around the cylinder intake port and the top of the valve.  D.I. engines create a lot of particulates, especially at high engine loads at part throttle.  I hope I'm totally wrong but there's a chance that your Viking 130 engines may see 10-20% power loss after a few years of consistent use due to disrupted and uneven airflow around the intake valves.  Even though you have "hundreds" of engines flying at this time without issue, there's a chance it could be an issue later on.  I would be interested to scope a number of intake ports at 500, 1000, 2000 hours to truly confirm that it is not an issue as claimed.  You have not "solved the D.I. issue", but rather you have minimized the issue for the time being.  

Take it or leave it but my advice is this, people can sense a half-baked product based on over-stated marketing claims.  I would push for conservative statements followed up by excellent customer service.  There are plenty of good things to say about Viking engines and I would stick with your data-backed claims.  

Brady, the only data we can provide is what we have at this time, again this goes for all the engines on the market in experimental. The highest engine we have at this time is 1200 hours (this was of about a 1.5 years ago) I imagine it is higher, with no sign of power loss or anything you have mentioned above. Have we seen an engine to 2000 yet, no. Nor do I believe anyone other then the typical certified have. At this time, we have had none of the issues you speak of, if we did - it would be addressed.

We can all have theories on what might, or might not happen - all we can report on is the facts we have at this time, as can anybody. We well expect the engines to go over 2000 hours, based on the experience we have and it would be vastly more affordable to  overhaul compared to the certified alternatives. 

The reality is you can throw all kinds of theories out, and dislike the way I say things or don't say them - EVERY engine maker out there has things they will talk about, praise and gloat on (respectively so)

There is plenty of data-backed information that I have like the number of sales, hours on our engines etc,. I can directly speak too, and you said that was wrong, so I am not sure there is a winning angle? 

I only wanted to explain what you are stating is just as misleading about a product that you personally have never flown behind, or opened up after these hours have passed, and we have. In fact when we spoke you didn't even ask any of these questions or concerns that you have? Why not? Why can't we just talk about it, here or on the phone. It is a helpful conversation to understand both sides, you are taking my words and saying they are "defensive" when in fact I am only trying to have a discussion. 

If you knew me in real life you would understand that, I can't explain the engineering of the engine to the tenth degree like Jan can, but I can and do fly across this country over and over again with them.



New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Zenith Homecoming Tee:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Lavion Aero

K&S Aviation Services

Aircraft Spruce & Specialty for all your building and pilot supplies!

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

© 2024   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service