EJ 22 in Zenith 750 STOL

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cheapracer

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You can quote all the technical jargon you want, but its a simple matter of the laws of physics that an engine operating at a higher rotational speed will deliver exponentially greater forces to those components.

FACEPALM.jpg .....


I am referring to the laws of physics, I even gave you the references of which physics to research for goodness sakes.


Sod it, I just don't have the energy anymore, you win Cletus.






Recently I saw a posting by Dan Thomas describing the failure of the exhaust valves in a Sube conversion he built.

You mean you saw a post about someone (I don't think it was Dan himself) who removed the millions of dollars and hours researched engine control module, i.e. the computer that controls the internal cylinder temps that stops valves being burnt, and replaced it with a good ol' carby ... oh for goodness sakes .. FACEPALM.jpg








You can quote all the technical jargon you want,

Yes, yes I can, but some days I pine for your bliss.



Ross quote: Perhaps we should all switch back to 1960s technology?


Eki reply: Works pretty well for Lycoming and Continental...why not Corvair ?
It works, but not well (re; efficiently). You can put forward all the reasoning you want for not wanting water cooling, redrives, weight etc, but there is no excuses for those veritably bad, and not used by anybody else today, 1940's combustion chambers.

In their defence I believe they don't want to make changes for liability reasoning, but that doesn't change they still have them.
 

cheapracer

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3) If you disagree with someone, you would do well to deal in facts instead of labels such as "brainwashed masses."
Why isn't that a fact? Some guys just continuously bleat out myth and lore, and that comes from years of being "brainwashed".


A pissing match between Subarus and Corvairs is really entirely unnecessary.
Why aren't you addressing that directly to member "Eagle"?

There's a thread currently about Lycoming 0145 going, mentions of the high maintenance and "modern" engine improvements to be made, etc - do you see any of the pro-auto conversion guys in that (or similar threads) taking those leads and bagging out and starting crap there? No.

But every single auto-conversion thread is jumped all over and bought down by (veritably) technically ignorant big mouths who know better - but can't technically back anything up with facts of course.

Quite different engines suited to different needs and different mindsets.
Exactly, so everyone simply keep to your own and mind your own business otherwise.
 

TFF

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Apples and bananas every time this discussion hits. A direct drive Corvair and a drive Sub is not the same thing as is the Lyconasor. Carb vs injection not the same. Ignitions. You have an airplane, so you need an engine that supplies XYZ. XYZ is what comes off the prop drive to drive the propellor. The formula behind the prop flange is just numbers. Every engine will break. They all have different weaknesses. But when I see a Lycoming four banger in good order, if the plane and pilot can do it, a takeoff with a snap roll is just business, even if not an aerobatic crank. Not going to happen with 99% auto conversions.
 

Eagle

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FACEPALM.jpg .....

I am referring to the laws of physics, I even gave you the references of which physics to research for goodness sakes.

Sod it, I just don't have the energy anymore, you win Cletus.
Can we just get past the theatrics and have a credible exchange. Here is an excerpt from an article by Jack Kane of EPI fame.
Look up his credentials if you have any doubt that he knows what he is talking about. Summa Cum Laude, Deans List,
Masters in Science and Engineering writes tech articles for Race Engine Technology magazine

Contact 2 001.jpg

Now regardless of the stroke of the engine, the rpms will exponentially affect the valves of an engine as rpms increase. Even if I agree with you
that the pistons may be safe at that rpm because of modern alloys, the valves take a pounding. There is twice as much heat generated because
the engine completes twice as many combustion cycles. The time that the exhaust valves have to dissipate heat to the seats is cut in half because
there mechanically has to be twice as many exhaust cycles. In effect, you have quadrupled the effect of heat on the valve. You have also increased
wear on the valve guide and valve stem and the valve seat which further lessens the exhaust valves ability to work properly. Now throw in the law of
probability and its very likely that some valves may get burnt as engine time increases. An exhaust valve is the single most recipient of the severest
abuse of any engine part, and operating it continuously at 4500 rpms quadruples that severity.



Yes, yes I can, but some days I pine for your bliss.
What can I say ???

It works, but not well (re; efficiently). You can put forward all the reasoning you want for not wanting water cooling, redrives, weight etc, but there is no excuses for those veritably bad, and not used by anybody else today, 1940's combustion chambers.
They work well enough for the purposed intent. The problem with Lycomings is cost not function. Corvair performs the same function for less cost.

In their defence I believe they don't want to make changes for liability reasoning, but that doesn't change they still have them.
If used Lycomings could be purchased in usable condition for $5k or less, or be bought and overhauled for $5k or less we would not be having this discussion no matter what the shape of the combustion chamber.
Since they virtually can't be found for reasonable prices we look at alternatives. Again, it isn't combustion chamber shape that drives this market, its cost, reliability, and simplicity.


Why aren't you addressing that directly to member "Eagle"?

There's a thread currently about Lycoming 0145 going, mentions of the high maintenance and "modern" engine improvements to be made, etc - do you see any of the pro-auto conversion guys in that (or similar threads) taking those leads and bagging out and starting crap there? No.

But every single auto-conversion thread is jumped all over and bought down by (veritably) technically ignorant big mouths who know better - but can't technically back anything up with facts of course

I just gave you the facts up above. Not really sure why you are jumping on me like this, because after all the Corvair is an auto conversion, just like air cooled VWs . The problem is that some people like to bash the Corvairs but find it difficult to bash Lycomings.

Last point. Honest discussion is not "starting crap". Personal insults would be consider as "starting crap", IMHO.
 
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rv6ejguy

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The OP was just asking some legit questions about using an EJ22 in his aircraft and the Corvair contingent felt they had to jump in here and start bad mouthing the Subaru. Why?

If you like Corvairs, use 'em. Same for Lycomings. Don't bash other people's engine choices especially where you know nothing about the topic.

McCrae, RAF 600+ Sube powered gyros sold (still being made in South Africa BTW), Dominator, VPM, Hawk, Twin Eagle and Sparrowhawk gyros use Subes, add to that the 600 engines going into rotary and fixed wing aircraft over the years we've supplied ECUs for plus lots more individuals use the EA81 and EJ20/22 and 25s in all kinds of airframes from Trikes to 2 seat flying boat designs. The Sube is probably the most popular engine choice for Gyros simply because air cooling doesn't work so well in that application and they are cheap, available, reliable and reasonably light. Subes are very popular down under- Neil Hintz has been supporting the Dominator and Sparrowhawk designs with Subes for a very long time. Anyway, my conservative guess is there are a least 2000-3000 Subaru powered aircraft flying worldwide, no way to tell for sure. How many Corvairs are? The Corvair is essentially only used in North America in any numbers.

The Subes are the only liquid cooled automotive engines used in any quantity on production kit aircraft. That probably says something about their integrity.

If the OP wants info on how to successfully convert an EJ for aircraft, he can PM or email me- I'd be happy to help. Continued debate here on the Corvair vs. EJ22
is not likely to lead to anything very useful- like debating if Italian food is better than Chinese food... It's a preference.
 
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Eagle

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For some reason any time someone has a different mindset than Ross, he seems to feel the need to talk down
to them and try to discredit them. He makes statements that no one has any right to talk about anything concerning
aviation engines unless they have first hand aviation experience, not automotive experience. He readily cites his
experience with Corvair engines in Corvair cars, but when asked about his experience with them in airplanes by
mcrae0104, he ignores the question. Sounds like a double standard here to me.

There should be an ability on HBA to compare the technical merits of both Subes and Corvairs, but Ross continues to get
personal with his comments rather than simply address the technological pluses and minuses of both engines.
Rather than use it as a positive venue to make the Subaru conversion really shine when he has a free audience
at hand he chooses throw out negatives.



Originally Posted by rv6ejguy
Just don't talk about engines you have no first hand experience with- especially in aircraft.




My personal experience is that I have never met William Wynne or Ross Farnham and neither of them would recognize me or vice versa. I certainly don't feel someone has to be brainwashed
in order to see and analyze the pros and cons of either conversion type. I have read that William Wynne can be very difficult to deal with whenever anyone doesn't agree with his point of view.
Apparently not being "brainwashed" to the Subaru philosophy causes a similar reaction for Ross Farnham. Maybe Ross and and William are more alike than they are different. From my perspective
it sure seems that way, because I have seen him in action on other HBA threads. If someone disagrees with him they are always quoted chapter and verse about his knowledge and experience and
then he follows that up with personal comments about how no one could possibly be right but him. He is right when he says this thread is now going nowhere, but its not from a lack of trying.
 

rv6ejguy

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For some reason any time someone has a different mindset than Ross, he seems to feel the need to talk down
to them and try to discredit them. He makes statements that no one has any right to talk about anything concerning
aviation engines unless they have first hand aviation experience, not automotive experience. He readily cites his
experience with Corvair engines in Corvair cars, but when asked about his experience with them in airplanes by
mcrae0104, he ignores the question. Sounds like a double standard here to me.

There should be an ability on HBA to compare the technical merits of both Subes and Corvairs, but Ross continues to get
personal with his comments rather than simply address the technological pluses and minuses of both engines.
Rather than use it as a positive venue to make the Subaru conversion really shine when he has a free audience
at hand he chooses throw out negatives.

My personal experience is that I have never met William Wynne or Ross Farnham and neither of them would recognize me or vice versa. I certainly don't feel someone has to be brainwashed
in order to see and analyze the pros and cons of either conversion type. I have read that William Wynne can be very difficult to deal with whenever anyone doesn't agree with his point of view.
Apparently not being "brainwashed" to the Subaru philosophy causes a similar reaction for Ross Farnham. Maybe Ross and and William are more alike than they are different. From my perspective
it sure seems that way, because I have seen him in action on other HBA threads. If someone disagrees with him they are always quoted chapter and verse about his knowledge and experience and
then he follows that up with personal comments about how no one could possibly be right but him. He is right when he says this thread is now going nowhere, but its not from a lack of trying.
Well, I asked you a couple times to tell me what your background with Corvairs and Subarus was and you didn't respond. I can only assume that's because you don't have any so I wonder why you think you're qualified to debate the issue at all.

HBA lately has become a place for people with no experience in the fields of question to start arguing with those who do have years of experience in the field and make fools of themselves.

I'm sorry if you and others somehow feel inferior because you don't have experience in a field. That's not my problem. Would I start debating with Auto or Boku on composite airframe construction? Nope because I have a tiny fraction of the experience and knowledge that they do and I'd look like a fool here too. I sit back and learn from their posts.

I didn't start the debate on Corvair vs. Subaru and I sure as heck don't push Subarus on people saying they are the greatest engine on the planet. They exist, they work, they're proven. If they fit your mission you can use one. I offered my input to the OP based on over 15 years direct experience with Subaru EJ engines in aircraft.

I didn't say I have experience with Corvairs in aircraft- I don't, but I'm probably the only one here who's built many examples of both engines. You feel qualified to talk about EJs but assume you have zero experience either building them or flying them? Your own double standard to a greater degree. Does reading an article in Contact make you an expert on Subarus? Nope. I could write an article on Russell Sherwoods SARL winning EG33 powered Glasair as an example of how well the engine can work as a direct counterpoint to Keith's EG33 experience. I know both cases well from helping both men over the years and you can see earlier references here on HBA and places like VAF as well. People have had good and bad experiences with all types of engines when they were converted for aviation use and I've said this many times all over the internet for 20 years now.

WW made his personality clear here on HBA a while back and was thrashed by the members. Not for his knowledge in the field, which is obviously extensive, but for the way he treats people.

I don't hold an exclusive on making Subaru conversions work well as many others have done it as well, and in different ways sometimes. In the Subaru community, we share our successes and failures on the groups and forums to progress the knowledge base so others don't make the same mistakes- much the same as others in the Corvair community have. That simply makes sense in my view. Of course you wouldn't know that many Sube users come to my company for help with problems because they know I know or know someone who can help them with that problem. That's only logical as well, since we've been flying the stuff for years and have seen most of the issues before. So I just don't see where you're coming from. Am I a knowledgeable resource for Subarus? Certainly compared to you, I am. I really don't care what you think of me. Most people in the Experimental engine world know me and value my advice since it's based on many years of direct motorsport and aviation experience. Your opinion won't alter that reality. If I don't know the answer, I can often direct their questions to someone I know in the community who does.

I am not "getting personal" with my comments towards you, rather asking the simple question - do you have any experience with EJ22 engines. How can you have useful debate on a subject with no knowledge of it?
 
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Eagle

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I'll just let Ross's own words do the talking and everyone can decide for themselves if there are any similarities to William Wynne,

and if Ross believes he is "The Authority" on everything from Subarus to Wankels and even Corvairs. Ross likes to imply that experience

gained by anyone other than himself back in the 70s,80s,or 90s is virtually useless when it comes to airplanes. So here is a compilation

of just a "few" of his comments. You be the judge.

Originally Posted by rv6ejguy
Just don't talk about engines you have no first hand experience with- especially in aircraft

Then admitting " I didn't say I have experience with Corvairs in aircraft- I don't,"

Well, I asked you a couple times to tell me what your background with Corvairs and Subarus was and you didn't respond. I can only assume that's because you don't have any so I wonder why you think you're qualified to debate the issue at all.

When commenting on Corvairs suitability for aircraft use


The Corvair has plenty of Gotchas which is why they need to come apart to check and address them. Nothing wrong with that if you take care of them all before you use it in an airplane or car for that matter. I'll list the ones that I've actually seen with my own eyes on the ones I've owned and overhauled- Head cracks between the seats, dropped seats, leaking pushrod tubes and top covers, cracked crankshafts, cracked pistons (one separated completely), loose exhaust guides, broken rocker arms, loose cam thrust washers and ovaled crank pins (110 cranks)-quite a shopping list.

But on another thread Ross praised them

I used to build turbocharged road racing piston engines professionally and raced them too for many years. My cars won 7 championships and engines would go the entire season with no teardowns. Rebuilds would cost literally a few hundred dollars each year- rings, grind valves, magnaflux and new gaskets. One long block went 5 seasons with the same bearings, crank, rods, pistons valves etc. and was still good when the car was sold. We had no problems with reliability.

All engine conversions: Can auto engines do the job well? Undoubtedly, but every system needs to be addressed/ designed for reliability to achieve that end. Miss one detail and you can have a bad day for sure as many have found out the hard way.



Ross on a NEW German version of a Wankel engine which he has no experience with but feels entitled to comment on
I'm saying that Wankels in production cars don't last anywhere near as long as piston engines today.

[B
Ross on William Wynne
WW made his personality clear here on HBA a while back and was thrashed by the members. Not for his knowledge in the field, which is obviously extensive, but for the way he treats people.

Then there is the way Ross treats people:

I'm sorry if you and others somehow feel inferior

you generally don't know what you're talking about here


You'd know that if you had any practical experience

I'm pretty sure I know a LOT more than you do about engines

I wonder why you think you're qualified to debate the issue at all.


Do you think engine designers maybe understand something that you don't?
Eagle: I have said virtually nothing on this post, these are all Ross's own words, and only a small sample of them.
While William Wynne claims to be "The Authority" on ONLY Corvairs, Ross implies that he is the absolute authority
on virtually every engine and engine type. Anything you or I have to say is not worth the posting it is written on.

On a Wankel thread Ross made this comment "I'm saying that Wankels in production cars don't last anywhere near as long as piston engines today."
But then he gets rankled when anyone talks about Subaru problems on a Subaru thread.

Notice that he throws out the comment about an alternative to the Wankel but takes umbrage when anyone mentions an alternative to the Subaru.
 
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mcrae0104

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Eagle--Ross has distinguished himself here as a generally knowledgable and courteous contributor to the forum. I don't agree with everything he says, but let's not make this about Ross.
 

Eagle

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Eagle--Ross has distinguished himself here as a generally knowledgable and courteous contributor to the forum. I don't agree with everything he says, but let's not make this about Ross.
Actually, it really is about Ross, about Ross's lack of respect for other people who post on this site and a continual need to discount their knowledge and experience. While I agree that Ross is pretty knowledgeable he fails to give others the same respect that he feels is owed to him. I have seen it on numerous occasions on various threads. He really doesn't need to do that sort of thing.

Let me explain it this way. Personally I think Ross's experience with Corvair engines from the sixties and seventies does provide him with the right to speak with relative authority about Corvairs in airplanes. I don't feel that all that experience is non-transferrable. What I take exception to is when he tells me that my experiences and my knowledge is not transferable or of any use when talking about airplane conversions. He doesn't need to speculate on my qualifications, or imply that I don't have a right to speak about what ever I please with whatever knowledge and experience I possess. He assumes that there is nothing worthwile, and implies as much in his posting. Thats pretty much WW type treatment, and I don't choose to accept it. We have all heard from people who choose not to take part in posting because they don't want to get embarrassed, and that kind of behavior is why. Having a good knowledge of many pertinent things does not give anyone the right to be disrespectful to others on HBA.

As I said earlier, I believe that Ross's knowledge and experience does make him able to provide some good insights on Corvair engines and I believe that his overall experience makes him helpful even in areas where he does not have direct experience. We all try to apply what we know in order to make it applicable to building an airplane and selecting and installing an engine in it. When someone discusses the pros and CONS of any engine, including Subarus, it should be in a friendly and respectful tone. If Ross disagrees with something I or any other poster says, he merely has to say something like, "In my experience this is what has proven to work, and I base that on; inputs from, testing,building one, racing one,flying one, or whatever basis he choses". What he doesn't need to do is to try to call other posters out and insinuate that whatever knowledge or experience they have pales in comparison to his, and is worthless. He needs to get over the premise that he ultimately decides who has a right to say what and when. Give the other fellow his due. Let him say what he wants and then say what you know about the subject matter. Then let the readers decide what they want to believe or go with. The whole idea of HBA is to share information and help one another. Ross also gets a generous boost to his business from people who read these posts. If everyone believed that there is only one correct way to do things, then there would be very few posts on HBA. One person would ask a question and any one person would answer it and the thread would be done. Having different opinions on what works best is what creates the conversations and often new solutions. Being intolerant and making derogatory responses is unnecessary and tends to impede participation. Ross should not care who the other poster is, he should just address the subject at hand and provide his knowledge and experience about it, and quit trying to discredit whoever wrote it. Its their opinion based on their experience.
Ross just needs to give his opinion based on his experience and let it go at that.

As I said, Ross has much knowledge he can provide to the site, but he needs to quit putting himself in a position that makes him comparable to Mr Wynne. Then I won't be writing all of this instead of talking about airplanes.
 

autoreply

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Moderator note:
Actually, it really is about Ross, about Ross's lack of respect for other people who post on this site and a continual need to discount their knowledge and experience. While I agree that Ross is pretty knowledgeable he fails to give others the same respect that he feels is owed to him. I have seen it on numerous occasions on various threads. He really doesn't need to do that sort of thing.
If you feel that way, you are welcome to hell him yourself. Doing it in public however is not the best idea and is probably going to yield the opposite result of what you wish for, which benefits nobody. It is also approaching a personal attack which our rules and regulations very clearly forbid.

So shall we all take a step back, take a deep breath and go back to the discussion this was about, the EJ22 in a Zenith 750 and leave out any reference to posters personality?

There's a deeper note to that, that's not always understood by those who might not have been "in the scene" for a long time. The great thing about HBA is that we have a wide range of qualified people over here. I like long, slender carbon, engine-less airframes and know a thing or two about them. Yet a discussion about a car-engined, aluminium stubby-wing airframe is most welcome as well. The only way to keep HBA that way is to respect other opinions and focus on substance.

While personal qualifications are "personal", they do give a lot more weight to arguments and as such can be relevant.
 

Himat

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Did I get the quoting right?
This was your statement Eagle?

Now regardless of the stroke of the engine, the rpms will exponentially affect the valves of an engine as rpms increase. Even if I agree with you that the pistons may be safe at that rpm because of modern alloys, the valves take a pounding. There is twice as much heat generated because
the engine completes twice as many combustion cycles. The time that the exhaust valves have to dissipate heat to the seats is cut in half because
there mechanically has to be twice as many exhaust cycles. In effect, you have quadrupled the effect of heat on the valve. You have also increased
wear on the valve guide and valve stem and the valve seat which further lessens the exhaust valves ability to work properly. Now throw in the law of
probability and its very likely that some valves may get burnt as engine time increases. An exhaust valve is the single most recipient of the severest
abuse of any engine part, and operating it continuously at 4500 rpms quadruples that severity.
There are some partial faults in the line of argumentation here.
The engine does not necessarily generate twice as much heat because it has twice the number of combustion cycles for each time unit. The engine produces heat proportional to the output power generated, only modified by the efficiency of the power generation. That is, at large , two 120hp engines generates the same amount of heat. If that happen at “high” or “low” revs do not matter. Efficiency on the other hand matter.

Next, heat transfer time from the valves are the same at all engine rotational speeds as long as the cam timing is the same. The crux is that the time for heat transfer is a certain number of rotational degrees for each cycle and that do not change with engine rpm.

Wear is as you say a function of number of cycles, but then that is usually taken care of by those that designed the engine. The same goes for valve gear strain, that is a design point and an engine designed for high rpm will work just fine at the design point.
 
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Eagle

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Did I get the quoting right?
This was your statement Eagle?



There are some partial faults in the line of argumentation here.
The engine does not necessarily generate twice as much heat because it has twice the number of combustion cycles for each time unit. The engine produces heat proportional to the output power generated, only modified by the efficiency of the power generation. That is, at large , two 120hp engines generates the same amount of heat. If that happen at “high” or “low” revs do not matter. Efficiency on the other hand matter.

Next, heat transfer time from the valves are the same at all engine rotational speeds as long as the cam timing is the same. The crux is that the time for heat transfer is a certain number of rotational degrees for each cycle and that do not change with engine rpm.

Wear is as you say a function of number of cycles, but then that is usually taken care of by those that designed the engine. The same goes for valve gear strain, that is a design point and an engine designed for high rpm will work just fine at the design point.
Now THIS is the type of reply that HBA should have, technical comments directed at the subject matter.
What you are saying is correct, but I believe what you are not allowing for is the time it takes for heat to actually transfer between components.
It's like touching your hand to a hot part. You can lay your hand on it for one second and a lot of heat will transfer, perhaps even burn you. You
can also rapidly touch the hot part 10 times for 1/10 of a second and very little heat will transfer to your hand. It will not be exactly the same amount of heat even though the contact time was equal because the flow has to begin to warm each time. The result will be less heat transfer.

I disagree with you that heat transfer time is the same at all rotational speeds. It would be the same amount in rotational degrees of the camshaft, but in actual time the valve touches the seat in milliseconds would be different. It's mechanically impossible for an engines valves to set on the seats the same amount of time when all events in the engine have become more rapid.

Are you familiar the the expression "double whammy" ? That's what happens to the exhaust valve, both heat applied more often and less time to dissipate it.
I agree that two engines producing the same HP at different rpms generate the same heat, but the Corvair produces 120 HP @ 3000 rpms and the Sube is 150 HP @4500 rpms. The Corvair will have more time for the heat to saturate into the seat.We are talking milliseconds here, so a little time means a lot.

As for the design point for operating speeds of the valves. The valves are designed to operate at higher rpms, even higher than 4500 rpms. The question then becomes how high and for how long ? If you remember, one of the original failure points with Subes was that the factory ECU would shut the engine down when certain loads were exceeded. This means that the factory electronically set limits to what the engine was subjected to. I don't think the Sube factory really expected their design to be run continuously at 4500 rpms, but that doesn't mean that they won't. The 4500 rpms only happens when aftermarket ECUs are used.

I guess the point here is that from the valves point of view it will be receiving more heat because the Sube is generating more power but it will also have less time to get the heat to transfer because heat transfer is not instantaneous, it requires time to saturate. A slower rotational speed allows heat to transfer more effectively.
 
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Himat

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The trouble is that even if I am an engineer, in something very different from internal combustion engines, my knowledge of engines is then mostly theoretical. ;)
Still I work with system where distances and time frequently, no pun intended, are measured in wavelengths.

Now THIS is the type of reply that HBA should have, technical comments directed at the subject matter.
What you are saying is correct, but I believe what you are not allowing for is the time it takes for heat to actually transfer between components.
It's like touching your hand to a hot part. You can lay your hand on it for one second and a lot of heat will transfer, perhaps even burn you. You
can also rapidly touch the hot part 10 times for 1/10 of a second and very little heat will transfer to your hand. It will not be exactly the same amount of heat even though the contact time was equal because the flow has to begin to warm each time. The result will be less heat transfer.
No not less heat transfer, but the time your hand is not touching the hot part the heat is transferred away from your hand. In principle, the moment you are not holding the hot part the duty cycle is lowered and there is more time for your hand to cool. Not so with engine valves where the duty cycle for cooling/heating is a fixed number.

I disagree with you that heat transfer time is the same at all rotational speeds. It would be the same amount in rotational degrees of the camshaft, but in actual time the valve touches the seat in milliseconds would be different. It's mechanically impossible for an engines valves to set on the seats the same amount of time when all events in the engine have become more rapid.
There is a little time spent “settling” the valves on the seat, but apart from that the time on the seat is constant at all rotational speeds. In the case of rotational systems, one rotation is one “time unit”. It is an abstraction, but the camshaft is the “clock” you measure time in.

Are you familiar the the expression "double whammy" ? That's what happens to the exhaust valve, both heat applied more often and less time to dissipate it.
I agree that two engines producing the same HP at different rpms generate the same heat, but the Corvair produces 120 HP @ 3000 rpms and the Sube is 150 HP @4500 rpms. The Corvair will have more time for the heat to saturate into the seat.We are talking milliseconds here, so a little time means a lot.
From this follow that the heat is applied for a shorter time to the valve too, which lead to less heat being transferred from the combustion gasses? So no “double whammy”. The first approximation is still that the camshaft gives the timing, duty cycle and heat transfer rate.

As for the design point for operating speeds of the valves. The valves are designed to operate at higher rpms, even higher than 4500 rpms. The question then becomes how high and for how long ? If you remember, one of the original failure points with Subes was that the factory ECU would shut the engine down when certain loads were exceeded. This means that the factory electronically set limits to what the engine was subjected to. I don't think the Sube factory really expected their design to be run continuously at 4500 rpms, but that doesn't mean that they won't. The 4500 rpms only happens when aftermarket ECUs are used.
You don’t think Subaru expect their engines to be run continuous at 4500rpm and high load? I do. In January 1989 Subaru set a FIA World Land Endurance Record driving three Legacy RS sedans at 138mhh for 18 days. That is almost 450 hours, or one fourth of the TBO time on many light aircraft engines.

I guess the point here is that from the valves point of view it will be receiving more heat because the Sube is generating more power but it will also have less time to get the heat to transfer because heat transfer is not instantaneous, it requires time to saturate. A slower rotational speed allows heat to transfer more effectively.
More power more heat. Heat transfer rate depend on the materials used, design and duty cycle. Time is substituted with fractions of a revolution and as such is not very relevant. The heat will redistribute in the parts when the valves are not in contact with the valve seat, changing the temperature gradient when closed somewhat, but I would need to actually do the calculations for the two scenarios to tell if it make a difference.
 

Eagle

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The trouble is that even if I am an engineer, in something very different from internal combustion engines, my knowledge of engines is then mostly theoretical. ;)
Still I work with system where distances and time frequently, no pun intended, are measured in wavelengths.
Well, not everyone can be a race engineer, but you certainly seem to be doing well in your explanations. This is the kind of back and forth thats enjoyable and interesting, certainly much better than just saying someone doesn't know what they are talking about but not discussing what is wrong with a train of thought. You have made me think a little differently and I have to admit that what you are saying seems logical and correct to me.

From what you have said, I now believe that the contact time of the valve on the seat will remain the same at higher rpms because over a period of time there will be more contacts that occur. I believe that will be from a geometric standpoint just because of the mechanical relationships of the components. The actual time in milliseconds that the valve is seated though will change as rpms increase.

There are some further considerations that will affect things too. The actual camshaft specs will affect a comparison. An engine expected to operate at somewhat higher rpms (Sube 4500) than an engine expected to operate at lower rpms (Corvair 3000 ) will probably have more overlap of the exhaust event. Also, the use of smaller and dual intake valves usually signifies higher somewhat higher rpms.




No not less heat transfer, but the time your hand is not touching the hot part the heat is transferred away from your hand. In principle, the moment you are not holding the hot part the duty cycle is lowered and there is more time for your hand to cool. Not so with engine valves where the duty cycle for cooling/heating is a fixed number.
I'm still not convinced on the heat transfer. I say this not because of any air cooling (which I admit would happen in my example) but because it takes actual time for heat to transfer. It is not instantaneous. While someones hand would receive the benefit of being surrounded by cool air, in the case of an engine valve the surrounding exploding and compressing that happens keeps the area hot, and the length of time both mechanically or timewise is important. The longer the valve is on the seat either descriptive way, the more heat it can transfer.

The Corvair has a single larger valve and it can dissipate more heat to the seat because its area is greater and it has less heat being generate to heat it because its less horsepower. While the Sube has two valves to dissipate heat, they operate independently, so it is somewhat wrong to consider both of them. I agree that both valves will draw some of the heat and lessen the heat effects on each other, but I believe there is plenty of heat and it doesn't help that much. We all realize that a smaller object is easier to heat up than a larger object. Thats one of the selling points on Lycomings large exhaust valves. They still sometimes burn exhaust valves. Having multiple small spindly valves will give more area for performance, but each valve will independently be heated, and will heat more quickly as power is increased. The question then becomes whether the valve can and will gradually deteriorate from long usage at high power settings. My comment about the Subaru engineers not expecting the engines to be operated at a continuous 4500 rpm merely meant that the expectation was they would be in daily driven vehicles that routinely operate at 2000 or so rpms, with ocassional acceleration to higher speeds. If you build the engine for that ocassional burst, it will hold up for longer use, but the question becomes how long.



There is a little time spent “settling” the valves on the seat, but apart from that the time on the seat is constant at all rotational speeds. In the case of rotational systems, one rotation is one “time unit”. It is an abstraction, but the camshaft is the “clock” you measure time in.
Remember that the seat is also being heated by the hot exhaust gasses when the valve is open, but the seat is for the most part protected initially from direct assault from the burning mixture by the valve face.


From this follow that the heat is applied for a shorter time to the valve too, which lead to less heat being transferred from the combustion gasses? So no “double whammy”. The first approximation is still that the camshaft gives the timing, duty cycle and heat transfer rate.
Yes, I have to agree with you on the first statement. My comments above are why I don't believe you can just make it a calculation based on the mechanical relationships. I believe that more seat time in a fewer events is more effective than equivalent seat time in shorter events because there is more continuation of heat exchange and less starting and stopping. It would be more constant, in my opinion that seems logical to me.



You don’t think Subaru expect their engines to be run continuous at 4500rpm and high load? I do. In January 1989 Subaru set a FIA World Land Endurance Record driving three Legacy RS sedans at 138mhh for 18 days. That is almost 450 hours, or one fourth of the TBO time on many light aircraft engines.
What I meant by that is that they don't expect cars sold at dealerships to ever undergo that type of use. I feel quite sure that the engine Subaru set the record with was hand assembled by professional race engine builders as opposed to one that is built by an amatuer airplane builder. Not knocking their accomplishment, but there have certainly been a lot of Subarus that developed blown head gaskets, and engine seizures AFTER they set the record in 1989.



More power more heat. Heat transfer rate depend on the materials used, design and duty cycle. Time is substituted with fractions of a revolution and as such is not very relevant. The heat will redistribute in the parts when the valves are not in contact with the valve seat, changing the temperature gradient when closed somewhat, but I would need to actually do the calculations for the two scenarios to tell if it make a difference.
My original thought was that the lower rotational speed (3000 rpm) of a Corvair coupled with far less complexity and weight (at least 100 lbs) was a better choice for someone who wanted to build a STOL airplane, as the original OP was planning. I produced an example from Contact magazine which aptly demonstrated the amount of extra work involved in repairing and troubleshooting a downed Subaru. Luckily the builder was able to bring the airplane down at an airport. He again, luckily found a FBO that would rent him space to store his plane and provide some assistance. He had to borrow tools that were not the kinds of tools normally available in order to troubleshoot his problem. Then he still had to make multiple trips and rent a room so he could spend the days that it took to fix his problem. Had he been in a STOL airplane and doing backwoods flying, this would have been a really major situation to deal with. I simply believe in a STOL type of airplane that will be used for off field flying that a simpler and lighter though less powerful is a better option. I still haven't changed that opinion, but I have learned a few things from you. So, thanks !:)
 

littlejon

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Some very valid points. As far as valve cooling, I would think that a liquid cooled engine would be better at cooling, thus even if it produced more heat it would have the coolant to help dissipate the extra heat. I like the idea of a more modern engine, fuel injection and electronic ignition. I am not against a Corvair engine, the direct drive is very appealing. I am building a stol, but, and maybe I will kick myself later, I am not as concerned with a little extra weight. I will probably be solo over 90% of the time, and even when flying with someone, I have done road trips on a bike so understand how to pack light. I am using a modified wing, instead of the slats I am using a longer nose that has a droop to it, so it may not be as stol as other 750's, but it will still be better then most GA aircraft. I also am looking at a little extra HP, this is so that I do not have to cruise at 4500 rpm to be at 75% power, if I build a 180 HP engine, I can have lower rpm settings to have the 130 HP takeoff HP which will add to the longevity of the engine.
I will have to look at the Corvair some more. As for the Subaru not being a good choice for an aircraft engine, I think that with as many examples are flying that it is a good choice, but is it a good choice for my application is what I will need to decide. The weight will be the biggest factor, I might be able to lighten it up a little, if I could get it around 250 lbs I thing that would be a good thing. A few things I have looked at is having the radiator under the cabin, which would remove some of the weight on the nose, along with using a dry sump, which would put the oil sump on the fire wall. I am just glad that I have some time to do some research before I have to make a decision. It has also been mentioned to use the EA81, which will not be as much HP but would be much less weight. It would be nice to have the money to just buy a $20,000 engine, but then I would not have this great learning experience.
 

Eagle

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Some very valid points. As far as valve cooling, I would think that a liquid cooled engine would be better at cooling, thus even if it produced more heat it would have the coolant to help dissipate the extra heat. I like the idea of a more modern engine, fuel injection and electronic ignition. I am not against a Corvair engine, the direct drive is very appealing. I am building a stol, but, and maybe I will kick myself later, I am not as concerned with a little extra weight. I will probably be solo over 90% of the time, and even when flying with someone, I have done road trips on a bike so understand how to pack light. I am using a modified wing, instead of the slats I am using a longer nose that has a droop to it, so it may not be as stol as other 750's, but it will still be better then most GA aircraft. I also am looking at a little extra HP, this is so that I do not have to cruise at 4500 rpm to be at 75% power, if I build a 180 HP engine, I can have lower rpm settings to have the 130 HP takeoff HP which will add to the longevity of the engine.
I will have to look at the Corvair some more. As for the Subaru not being a good choice for an aircraft engine, I think that with as many examples are flying that it is a good choice, but is it a good choice for my application is what I will need to decide. The weight will be the biggest factor, I might be able to lighten it up a little, if I could get it around 250 lbs I thing that would be a good thing. A few things I have looked at is having the radiator under the cabin, which would remove some of the weight on the nose, along with using a dry sump, which would put the oil sump on the fire wall. I am just glad that I have some time to do some research before I have to make a decision. It has also been mentioned to use the EA81, which will not be as much HP but would be much less weight. It would be nice to have the money to just buy a $20,000 engine, but then I would not have this great learning experience.
I think you are making a wise choice to proceed slowly. The thread actually went into too much depth about valves. It's really more of a general equation. Do you want simple and good or do you want higher tech and a more complicated and complex and good? Only you know what will make you happy. If you plan to go to secluded places, simple becomes much better IMHO. If I were you I would try to seek out actual builders and ask their opinion. Also ask them what problems they encountered with their conversion. I know some guys who built a Zenith 750 and put a Jabiru in it. They had a lot of problems with overheating. I think they finally solved the problem but haven't seen them for awhile. Correct engine choice can make a big difference in satisfaction.
 

cheapracer

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There are some partial faults in the line of argumentation here.
All of it.

Just one minor example, this nonsense about valve wear. A pushrod engine has a rocker that pulls and pushes the valve to either side as it pushes the valve down, valve guide wear in the 'good old days' was common and head shops would replace valve guides (or bronze insert on cast iron) and stem seals on a regular basis. Performance engine builders would shorten or lengthen the pushrods to get acceptable rocker angle geometry to minimise friction and help the valve to seat properly every time.

A SOHC or DOHC direct bucket actuation such as the Subaru and most current automotive engines, has zero side load on the valve and valve guide, period. The side load is taken by the bucket which has massive surface area, hence no wear on it either.

Then there's the inertial weight, valve/seat surface area and actual lift/duration comparison which makes the argument all bunk.

This is the difference between actual knowledge and imagination.

Porsche arguably made the best aircooled, 2 valve engines around, just like a Corvair, yet now are water cooled, DOHC, 4 valve screamers just like Subaru. What were they thinking ... :gig:
 

Eagle

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All of it.
Do you ever just try to have an intelligent and productive conversation ?

Just one minor example, this nonsense about valve wear. A pushrod engine has a rocker that pulls and pushes the valve to either side as it pushes the valve down, valve guide wear in the 'good old days' was common and head shops would replace valve guides (or bronze insert on cast iron) and stem seals on a regular basis. Performance engine builders would shorten or lengthen the pushrods to get acceptable rocker angle geometry to minimise friction and help the valve to seat properly every time.
Since you are a supporter and follower of Ross, shouldn't you follow the "rules"
about experience gained in the sixties not being applicable to airplanes ?

A SOHC or DOHC direct bucket actuation such as the Subaru and most current automotive engines, has zero side load on the valve and valve guide, period. The side load is taken by the bucket which has massive surface area, hence no wear on it either.
No one has mentioned "side" loads per se on this thread. Common sense tells everyone that two parts rubbing against each other will create wear even if oil is present. The faster they rub during a given time will mean that there will be greater wear. Surely you aren't suggesting that Subarus have come up with some new technological marvel and their valves never wear ? Seats wear, stems wear, guides wear, rocker arms wear. It really pretty rediculous to suggest that none of these components wear in Subaru engines. Perhaps you missed this attachment on an earlier posting.

https://www.youtube.com/watch?v=Ac_p48YX3mU

https://www.youtube.com/watch?v=xUJw40cE_DM Watch this video and then say that Subaru valve trains don't wear, carbon up, or burn.

https://www.youtube.com/watch?v=t9Tnik7vFQk Resurfacing yet another Sube blown head gasket

https://www.youtube.com/watch?v=8ZbPlHnistA Still trying to get a head gasket that doesn't leak on a mid 90s Sube in 2010. (Just $324 at Autozone)

Just look at all the videos on Utube about Sube heads and gaskets and repairs. A virtual epidemic.

Contact 2 001.jpg

Then there's the inertial weight, valve/seat surface area and actual lift/duration comparison which makes the argument all bunk.
I don't believe I ever mentioned "inertial weight" or "actual lift" in any comment. Do you have trouble quoting people accurately too ? As for valve and seat surface area not playing any part in heat transfer, I really don't see how you could ever believe that the size of an object has nothing to do with its ability to transfer heat.


This is the difference between actual knowledge and imagination.
So far all you have done is make a bunch of nonsensical rhetoric. Blathering about your superiority and yet unable to make a credible comment ? I'm amused by your arrogance.



Porsche arguably made the best aircooled, 2 valve engines around, just like a Corvair, yet now are water cooled, DOHC, 4 valve screamers just like Subaru. What were they thinking ...
:gig:
So, how many Porsche powered airplanes have you seen lately? The Corvairs and VWs seem to be doing just fine though, and then there is Lycoming, still going strong with them big ole valves rubbing sideways and chuggin along without a computer or water cooling. Some of them have been rebuilt so many times the original crankshafts and rods have 10,000 hours on them. Air cooling in airplanes won't be going away in our lifetime.
 
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littlejon

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So what is a realistic weight I can expect with an install. I will use as light of an alternator as possible as I am using LED's on the plane and will not have a glass panel, so power usage will be pretty minimum. The motor I have now comes in at 205 pounds with out the radiator, alternator, flywheel or starter. I understand I will need a PRSU, so that and the propeller, which I am planning on a composite ground adjustable, not sure if it will be a two or three blade? I have heard the fewer blades the better, so it might be a two blade.
I plan of putting the radiator on the fire wall or under the cabin, this will put a little bit of the weight back towards the CG. There is a local machine shop that I am hoping to have fabricate the motor mount and possible shave little extra weight off the motor, so that should help a little bit as well.
I am not interested in a pissing contest as to who thinks what engine is the best, I have looked at SDS's website and as others here have commented, from what I have seen and read Ross is very knowelegable about the Subaru engine. Before someone says that this can break or that can fail, I understand that anything can happen to any engine. A Corvair, a Rotax, a Jabiru or even a certified engine can fail. I guess I am not afraid of what I do not know, but I am not afraid of a Subaru engine breaking, looking at the number of engines that are out there, but also understanding that if I go with a Viking that it also has the possibility of failing. At this moment I am trying to find out if I will be able to come in at a reasonable weight for the airframe, I know that it will have plenty of power and what ever engine I choose WILL have a potential to have an engine failure. If this was not true then we would not practice what to do if the certified plane we learned in had an engine out situation, and that is on a certified aircraft.
Thank you all for your comments, it has given me other things to look at and consider, I am glad I am doing this now while I still have time to make a, HOPEFULLY, good decision, even if it is not the decision that you would make.
 
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