Myths and Choice of IO-360 Lycomings

Whilst extracting Cruise Performance data from Kevin Horton's excellent O-360 Engine Power Spreadsheets, I noticed that the Angle Valve IO-360 (Inclined Valves and Hemispherical Combustion Chamber, for better gas flow at high RPM) only has higher power output than the IO-360 Straight Valve engine when run higher than 2400 RPM.

It would appear that the Angle valve is more highly tuned and does not have as flat a Power Curve as it's Straight Valve brother and so the power output drops off more rapidly than the Straight Valve when RPM is reduced from 2700.

So on the cruise it would appear that there is very little advantage in the Angle Valve engine, particularly as it is around 30lb heavier. See picture of Spreadsheets below.

It begs the question as to why Lycoming made the Angle Valve engine.
Was it to provide obese Spam Cans with another 20BHP for Take-off.
If so, it has no applicability to RVs.

Look forward to some input on the matter from the Engineers amongst us.

Pete.

The angle valve engine is also more prone to cylinder cracking. Ask any Mooney owner.
Mel...DAR

You don't want an angle valve IO-360, because everybody you fly with will be jealous of your superb climb, cruise, and economy. Better steer clear of those things!

I flew behind angle valve IO-360-A series engines in two Mooneys and now my RV-7. I have nearly 2000 hours behind the angle valve engine and I love it. Cracking? Mooney drivers? Dunno about that. Don't know how those particular Mooney drivers OPERATED their engines.

The angle valve does have more cracking (both case and cylinder[) problems than the parallel. But the angle valve is really worth it if you use the IO-390 since they don't make a parallel version of that .

I'll be shopping for an angle valve if I can find one when I'm looking for an engine. Even with the 'problems'.

Dem Dare Fighting words

dan said:

You don't want an angle valve IO-360, because everybody you fly with will be jealous of your superb climb, cruise, and economy. Better steer clear of those things!

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Don't forget about the extra cost of purchase and overhaul, plus the +30 lbs of extra weight!, ha ha ha I AM KIDDING.

http://www.lycoming.textron.com/main.jsp?bodyPage=productSales/engineSelectionGuide/360.html

The IO360 is an awesome engine. Cylinder cracks, never heard of them specifically on this engine either, but if its a Mooney thing, its from high flying and trying to get down, shock cooling. I taught at flight club/school which had 30-40 planes, including a few Mooney's. The key in checking members out was to get them to understand they needed to think about letting down as much as 60-80 miles out to allow a (warm) powered let down. Flying well above 10,000 feet in a fast retract requires more descent planning than flying slower C172 at 8,000 feet. Of course the bone heads would go , Doha! I am too high, chop, drop and causing thermal stress, aka shock cooling.


Yes Dan I am jellious.

G

gmcjetpilot said:

Of course the bone heads would go , Doha! I am too high, chop, drop and causing thermal stress, aka shock cooling.

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OWT. I say that very carefully and with much respect because I know you're a rather helpful and prolific poster hereabouts, but this is a topic I've studied. The greatest thermal stress your engine will endure is when you pull the mixture to idle cutoff before you back it into the hangar. Yes, aluminum accumulates fatigue cycles with heating and cooling, but pulling the power before heading downhill is not a significant source of thermal shock. You'll drop 10-20 degrees in CHT in the first several seconds, but that's not really significant. It will continue to cool, but the combustion happening on the other side of the cooling fins will keep them jugs toasty anyway, so the cooling profile is still gradual enough to not matter. In other words, the thermal cycle the cylinders experience- even in a crowbar descent, is shallow compared to that experienced when the engine is shut down.

First run cylinders aren't at much risk for cracking, no matter what you do to them. After about 3000 hours or so, the thermal cycles of startup and shutdown have accumulated to the point that the aluminum is weakened and more prone to cracking. For a real-world example, jump planes are the kings of the chop and drop descent, but their jugs usually make TBO.

Respectfully,
Dave

I may be in the minority here, but I also think that the "advent of modern engine monitoring solutions" can only help to mitigate temperature-related issues of the past. That is, assuming the monkey with the stick in his hand knows how to interpret it!

fodrv7 said:

Whilst extracting Cruise Performance data from Kevin Horton's excellent O-360 Engine Power Spreadsheets, I noticed that the Angle Valve IO-360 (Inclined Valves and Hemispherical Combustion Chamber, for better gas flow at high RPM) only has higher power output than the IO-360 Straight Valve engine when run higher than 2400 RPM.

It would appear that the Angle valve is more highly tuned and does not have as flat a Power Curve as it's Straight Valve brother and so the power output drops off more rapidly than the Straight Valve when RPM is reduced from 2700.

So on the cruise it would appear that there is very little advantage in the Angle Valve engine, particularly as it is around 30lb heavier. See picture of Spreadsheets below.

It begs the question as to why Lycoming made the Angle Valve engine.
Was it to provide obese Spam Cans with another 20BHP for Take-off.
If so, it has no applicability to RVs.

Look forward to some input on the matter from the Engineers amongst us.

Pete.

Click to expand...

This is entirely sensible behavior. If you think about the physics involved here, better cylinder filling depends on flow inertia and flow inertia is greater at higher velocities, which occurs at higer rpm.
If the engines operated at much lower speeds, smaller intake passages would probably have better filling characteristics than the larger passages and would probably have better power.

OWT. I say

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Like Dave I am not a big believer in shock cooling being a major cause of cracking of cases or cylinders based upon my experience and watching CHTs during drastic power reductions, descents and when flying through heavy precip.
Shock Cooling Myth or Reality

or

Note the Graph and narrative



Of course there are no long term double crossover blinded prospective large sample studies to prove or disprove the case on either side I believe common sense and available data suggest that John is right. Keep it under 380degF to start with and you are unlikely to have a problem

dan said:

I may be in the minority here, but I also think that the "advent of modern engine monitoring solutions" can only help to mitigate temperature-related issues of the past.

Click to expand...

I agree completely. The factory CHT gauges in most spam cans are horribly imprecise. In my 182, 400 deg. CHTs put the needle in the middle of the normal range. With a multi-probe electronic engine monitor, I can either enrichen the mixture if I want to burn a bunch of gas, or lean it past peak EGT and watch the CHTs drop to 350 deg. and below. Either way, I pay a lot more attention to keeping the engine in a happy place than used to be possible.

Makes me wonder how often people were flying around in the old days pushing red line on their CHTs, completely oblivious. It's a well documented fact that the fatigue properties of aluminum start to change at a faster rate in the low 400 deg. temperature range. IMHO, this is a much more likely root cause for cylinder cracking than the shock cooling myth. Instrumentation and the ability to know what it's telling you is gooooood. Yup yup yup.

Dave

Wrong again

David Johnson said:

OWT. I say that very carefully and with much respect because I know you're a rather helpful and prolific poster hereabouts, but this is a topic I've studied. Respectfully,
Dave

Click to expand...

N395V said:

Like Dave I am not a big believer in shock cooling being a major cause of cracking of cases or cylinders based upon my experience and watching CHTs during drastic power reductions, descents and when flying through heavy precip.

Click to expand...

I guess I stand corrected. This prolific poster is wrong AGAIN! Doha!

Dave, I appreciate your cordiality and you make some good points. Milt good points also. I think overheat is way worse. However "quick cooling" is not without damage. I also agree extensive engine instruments (8 and 12 channels of cylinder temps) helps a lot.

OK, slam the throttle shut and push it over, no problem, right? I concede. It does not sound correct but I'll go with it for the time being. The reason I concede is I never tried it. I was taught don't do it. So I don't. I never questioned it.

I do know when I was flying a C182 jump plane we did this; they replaced cylinders like people change oil? I was under the mistaken idea there was a correlation to pulling the throttle back, quickly descending and shock cooling? I agree slamming the mixture full rich is an even better way to shock cool an engine.

OK, Now this is what the manufacture says, but what do they know?
http://www.lycoming.textron.com/mai...keyReprints/operation/avoidSuddenCooling.html

--------------------------------------------------------------------------

QUOTE Lyc:

"Sudden cooling is detrimental to the good health of the piston aircraft
engine. Textron Lycoming Service Instruction 1094D recommends a
maximum temperature change of 50oF per minute to avoid shock
cooling of the cylinders.


Operations that tend to induce rapid engine cool down are often associated
with a fast let down and return to the field after dropping parachutists or a
glider tow. There are occasions when Air Traffic Control also calls for fast
descents that may lead to sudden cooling.

The engine problems that may be expected when pilots consistently make fast letdowns with little or no power include:

1. Excessively worn ring grooves accompanied by broken rings.

2. Cracked cylinder heads.

3. Warped exhaust valves.

4. Bent pushrods.

5. Spark plug fouling.

Generally speaking, pilots hold the key to dodging these problems. They must
avoid fast letdowns with very low power (high cruise RPM and low manifold
pressure), along with rich mixtures that contribute to sudden cooling. It is
recommended that pilots maintain at least 15" MP or higher (I like 19"-20" min)
and set the RPM at the lowest cruise position. This should prevent ring flutter
and the problems associated with it.

Letdown speed should not exceed high cruise speed or approximately 1000
feet per minute of descent. Keeping descent and airspeed within these limits
will help to prevent the sudden cooling that may result in cracked cylinder
heads, warped exhaust valves, and bent pushrods.

The mixture setting also has an effect on engine cooling. To reduce spark
plug fouling and keep the cylinder cooling within the recommended 50o per
minute limit, the mixture should be left at the lean setting used for cruise and
then richened gradually during descent from altitude. The lean mixture,
maintaining some power, and using a sensible airspeed should achieve the
most efficient engine temperatures possible.

The operating techniques recommended in this article are worth consideration
as they will be a positive step toward saving dollars that might be spent on
maintenance. Whatever the circumstances, pilots must plan their flight
operations so that the potential damage caused by sudden engine cooling
can be avoided."

--------------------------------------------------------------------------

I think there is more to it besides temperature, such as ring flutter.

Here is Service Instruction SI-1094D
http://www.lycoming.textron.com/sup...ePublications/serviceInstructions/SI1094D.pdf

The bottom line is NOT cooling more than 50F per minute. How its done is up to the pilot. My recommendation is start down early, leave the mixture lean, reduce the throttle only slightly (no more than 1"-2" at time and no less than 19" for me, Lyc says 15" min), trim for a descent airspeed producing say 500 fpm so it does not exceed Vne or Vno (max structural) or less as needed for conditions. When I flew part 135 in turbo piston twins the "airline" gave pilots training in "shock cooling" because they where sensitive to it and affected the bottom line (according to them). I am paying for my cylinders, so am not too cavalier about it, but than each to their own. I will continue to baby my engine.

The point you make Dave about thermal cycle fatigue is a good one. That is why its important to cool the engine down before shut down; however if you do it right this should not be a big shock. The same applies at altitude. Even a little "shock" it adds up. I agree over 400F is worse than an occasional chop and drop.


As far as Avweb article, I think they like to make a splash with their Myth Busted articles. I try to read them but sometimes its not really based on science as much as based on prove me wrong. I already said I concede, I am wrong. However I tend to blindly follow Lycomings recommendations and what I have been taught over the years. May be conservative but that is they way I am.

The article in question does not really address anything and it's main argument there's no info counter to his "hypothesis". With a turbo engine flying hot at altitude, followed with a slam dunk, you can expect increased exhaust, turbo, valve and cylinder maintenance. How do I know, I flew freight in Aerostars, Navajos and Seneca II's. He says "no parts are raining down". Well that is silly. Of course not, the damage is cumulative and small but costly. Also most freight dogs know better or get fired. The writer of the article even says common sense says it's good not to slam the throttle shut, but you can. OK, HE CAN DO IT. I am not.

Any rapid movements of throttle and mixture is bad. Again bottom line is if rate of cooling is less than 50F than you are good to go. Of course as someone pointed out we did not always have 4 and 6 channel engine monitors and computers. So if you are well instrumented, than by all means fly your engine monitor. 50F/min is a max BTW.

Also common wisdom is don't back drive and engine. Always keep it driving the prop, even if it's just a little. I am sure AvWeb has an article that says that's wrong also, but there is "back lash" and my gut feel is keep the chain tight and don't yank on it. Keep letting it go loose and than yank on it, over and over. The chain may not break, but it will make a heck of a noise.

BTW way no chain yanking. Appreciate Dave's and Milts input. Something to think about.

Cheers, respectfully George (prolific poster, ATP/CFI)

Rate of cooling

gmcjetpilot said:

...Any rapid movements of throttle and mixture is bad. Again bottom line is if rate of cooling is less than 50F than you are good to go. ... 50F/min is a max BTW.

Click to expand...

I think Dave addressed this here:

David Johnson said:

The greatest thermal stress your engine will endure is when you pull the mixture to idle cutoff before you back it into the hangar.

Click to expand...

Not much avoiding that, and it happens on every flight. It's kind of hard to argue that this will be less brutal than any chop and drop. Shock cooling does seem to be an OWT. I'd like to hear about how the big, old radials were managed.

gmcjetpilot said:

I guess I stand corrected. This prolific poster is wrong AGAIN! Doha!

OK, slam the throttle shut and push it over, no problem, right. You guys know more than I do, so I concede. It does not sound correct but I'll go with it.

OK, Now this is what the manufacture says, but what do they know?

Click to expand...

Well, I had hoped you might respond in a less sarcastic way so we might get at the issues and leave the rhetoric aside. I offered same as a courtesy. I'll do my best to continue to do so. Again, no disrepect is intended.

There have been several instances in the last couple of decades where Lycoming and/or Continental's published recommendations have been in direct conflict with the known physical laws of combustion and thermodynamics. Literature warning against running an engine LOP is another example, but that's a discussion for another day. In the case of the article you posted, Lycoming is offering no hard data to support their recommendation. It would be reasonable to suggest that they don't have any.

Take a look at the analyzer data provided by Milt in a previous post and note the gradual and shallow CHT drop after the engine loses its fuel supply. When we pull the throttle to descend, we still have fuel and combustion continues, so the curve you would see in a crowbar descent would be shallower still. If I can find a data file from one of my recent flights, I'll post it, but suffice it to say that when I pull the mixture to idle cutoff on the ground, the cooling curve is similar, but more importantly, much deeper. That's where the fatigue happens.

gmcjetpilot said:

My recommendation is start down early, leave the mixture lean, reduce the throttle only slightly (no more than 1"-2" at time and no less than 19" for me, Lyc says 15" min), trim for a descent airspeed producing say 500 fpm so it does not exceed Vne or Vno (max structural) or less as needed for conditions.

Click to expand...

I think that's a good practice also, but probably not for the same reasons you do. All I'm saying here is that pulling the power quickly to descend is not going to hurt the engine. At the same time, unless there is a good reason to do so, proper descent planning is wise, as much for passenger comfort and keeping the pilot on the ball as anything.

gmcjetpilot said:

I do know when I was flying a C182 jump plane we did this; they replaced cylinders like people change oil? I was under the mistaken idea there was a correlation to pulling the throttle back, quickly descending and shock cooling? I agree slamming the mixture full rich is an even better way to shock cool an engine.

Click to expand...

Did you have an engine monitor in that C182? Were you relying on the factory CHT probe (mounted on a single cylinder)? Is it possible that in the climb at least some of the cylinders were running well into the 400s and you never knew it? I know several people whose experience with maintaining jump aircraft is very different.

As for slamming the mixture full rich, there were cases where turbocharged twin Cessnas coming down from high altitude were experiencing cracks in the intake ports. For a long time it was chalked up to shock cooling at the top of the descent. Turns out the culprit was the cold fuel (chilled at altitude) being injected into the ports when the pilot went full rich in the pattern. They stopped going full rich, and the problem ceased.

As for the 50 deg./min. as the maximum acceptable rate of change, can you explain why it's OK to double that rate when heating the cylinders from idle to takeoff power on the takeoff roll, as we all do? While you're at it, can you explain why flight training aircraft frequently make TBO, even with instructors and students chopping the power from full to zero several times per flight? there's an O-320-H2AD sitting in the hangar at Erie with 4000 hours SMOH, straight from a flight line trainer with nary a jug pulled.

Shock Cooling

Cheers,
Dave

Family Jewel

Cylinder cracking! Interesting?
Anyway, for those of you who have yet to decide on an engine to drag your RV around the sky, I?ll attempt to drag this post back to where I intended it.
There is only one engine you should use to power your RV.
The one that suits YOUR needs.
But like all decisions along the rewarding journey towards the ?First Flight? it will be based on collected wisdom; and that is the real value of Doug?s forum.
It is a shame that so many of these posts turn into pissing competitions on Tail Wheel v. Nose wheel, Aero engine v. Auto engine or the length of our respective family jewel. You end up having to spend so much time filtering the post replies.
Cylinder head cracking. Interesting subject, but is not going to determine which engine you purchase.
If you need to out climb, out run and do it with less fuel, then maybe Dan is right. Buy an Angle Valve. Although, even with the finest pencil I cannot discern any difference in economy from the Part Throttle Fuel Consumption Charts page 3-22 for the IO-360A and page 3-23 for the IO-360B of my Lycoming Operators Manual.
So, the facts I originally post remain just that and not opinion or anecdotal.
The Straight Valve and Angle Valve IO-360 engines at around 7000? at cruise power are within a BHP of each other for a weight difference of 30lb and a purchase difference $4000. Facts.

So the cleaner breathing Angle Valve produces more power at high revs than the Straight Valve, but ONLY the same at cruise RPM.

You simply need to decide if the higher power available above cruise RPM is worth the expense.
Pete.

You are right, what did I say wrong?

David Johnson said:

Well, I had hoped you might respond in a less sarcastic way so we might get at the issues and leave the rhetoric aside. I offered same as a courtesy. I'll do my best to continue to do so. Again, no disrespect is intended. Cheers,
Dave

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Dave you are confusing me, I am just agreeing with you. I think my sense of humor was miss interpreted. Doha!

Your data is irrefutable. Milt's comment, data and referenced article have some great points. I am freely admitting you know more about it than I do, because I never tried it. I was taught not to do it, and that is the way I fly. However I reserve the right to change my mind. To be clear "IT" being big power changes, especially long low power descents.

No sarcasm, in fact I thanked you for being so polite and commented you made good points, several times. What else can I say. I never offended anyone before by saying they where right, well may be except for my ex-wife, but I am sure I was never married to you. (NOW THAT IS sarcasm, bada BOOM bada BANG. ). Lets laugh, OK.

I did point out Lycoming has put a quantitative number to shock cooling and their technical opinion to the subject. However I don't see this countering your conclusion if indeed you do not cooling more than 50F/min. The "ring flutter" is interesting. I take that as don't go below their recommended 15" MAP. I call that don't let the prop push the engine. Another controversy no doubt.

Hey its hard to change years of training, but I respectfully submit you have changed my mind, albeit with some prejudice. I will not change my way of operation but I will look into it further. When I get my plane flying I'll do some experiments myself. However I see no need to stay high and drop in from upon high at "MIN POWER".



The AvWeb article said many things in the start that makes a lot of sense. The math sounds OK and backs Milts data, that CHT does not change much, but the other stuff I don't think makes much impact on the subject.

"To my way of thinking, there is no scientific proof that shock cooling plays a
significant role in cylinder damage in aviation."

It's true and there is no evidence one way or the other. Than it gets into other peripheral or anecdotal evidence that "shock cooling" is a myth and not critical, such as flying in rain (verga). This is kind of weak. Very little water gets to your engine, unless its a typhoon, and wet air is LESS dense and provides less cooling. However if you're in a "verga" the evaporation has occurred and cooled the air. Sure that will help but a very small amount. The author pointed out that its not wise flying into a verga. He is right. (Extreme down drafts occur in verga's and are one sign of possible micro burst.) The RIAN evidence is a non-sequitur.

The cooling at shut down is also weak anecdotal evidence that shock cooling does not exist, in my opinion. The logic is if is OK here it is OK in flight? First the total temp at shut down is much less. Yes there is rapid cooling but from a much lower temp. Cooling from 260F fast is not like going from 400F to 300F fast. Also the engine has to keep running in flight, while going thru this temp transition. The shut down evidence is also non-sequitur, true but logic does not follow conclusion.


So I follow Lycomings recommendations, while still agreeing with you. If you have the full meal deal engine monitor than by all means drop a chop if you maintain Lycs limitations, like:

Minimum in-flight CHT 150F (I like high 200's or 300F. BELOW 300F lead fouling!)
Max CHT rate of change 50F
Min Oil Temp 165-190F
Min Oil Press 55 psi
Min MAP 15" (my personal rule 19" MAP min until final)

No offense. Besides temp there are reasons as you and I agree to keep it hot. Lead fouling, piston ring flutter and carb heat to name a few.

Cheers George

PS as far as jump planes, the name of the game was to get on the ground. There was no CHT gauge. To get down, put it in a 60-70 degree bank spiral right after the climb and passengers "stepped out". The name of the game was to get on the ground. You tried to keep some power and use the drag from the high "g" steep descending spiral. Some just chopped and dropped. There was no worry of cylinders. It was part of the business.

PSS In fact as a CFI and CFI (ME) I chopped power. Students needed to get simulated power loss demos, multi engine pilots single engine work. However I did things to minimize the danger (of really loosing power) and abuse of the engine. I made sure the engine was in low power cruise or descent before the demo. Therefore it was already cool. The NTSB has so many accident from simulated engine failures they, AOPA, FAA have reports on it. That is why your CFI added power on occasion during a simulated engine failure. GOING TO REAL LOW POWER in descents can be bad. The engine may NOT come back when you need it to. Carb ICE is a good reason to "keep it hot". Go to idle and you don't have carb heat. When you are ready for power, push the throttle forward and nothing.

Wow what do you expect for FREE

fodrv7 said:

Cylinder cracking! Interesting? It is a shame that so many of these posts turn into pissing competitions. So, the facts I originally post remain just that and not opinion or anecdotal.

It is a shame that so many of these posts turn into pissing competitions on Tail Wheel v. Nose wheel, Aero engine v. Auto engine or the length of our respective family jewel. You end up having to spend so much time filtering the post replies.

Pete.

Click to expand...

Sorry Pete I guess I hi-jacked your threat. Sorry there are no pearls of wisdom's, but you answered your own question, get what ever you want.

It really does not matter that much, does it? You have the facts, the rest is opinion. If your hardest decision is to pick a new 180HP or 200HP engine you got it made. Many can only afford a used H2AD or conical O320 150HP, if they can build a RV at all. Its not that serious of a questionis is it? What engine should I get. Who knows.

I would go with 180HP myself (and did) because its enough HP (heck 150HP is enough), cheaper and lighter. I don't think these are in dispute. I rebuilt a used O360 and it awesome, but that does no help you. However the 200HP Lyc is a very nice machine. It has a damper weighted crank and no prop restrictions. It does cost a bunch more. Are you without a budget? On a related note to rapid throttle movements you can "De-Tune" the counter weights of a IO360 (200HP), but this is simple to avoid, don't slap the throttle around. I know a lot of formation guys love to slam the throttle shut, doing 180 or 360 over heads. I would be less comfortable with that on a 200HP IO360 than a 180HP (no damper weight crank) .

I am convinced the better breathing 200HP counter weight engine is able to fly LOP better than the smaller engines. The counter weight keeps it smooth even when running on the ragged edge of roughness. The heads are just better, obviously by the 20HP extra on the same displacement (and 0.20 compression bump).

As far as the shock cooling Pete, that was one comment made about the IO360, someone made, taking the time to answer your question. I am sure they gave their opinion in good faith. I made the comment as Dan C. did we had not heard of this. Than Dave and Milt added good info on this topic which is related. I found it interesting and useful to me at least and sure other's did as well. Like all things on the web its something to look into and add to the mix. It may be true. I just never heard of a spacific problem with the IO360 (200HP). It's the nature of a forum and free discussion. Comparing this to primer debates is not fair. Don't you want to know if 200HP IO360's are more subject to cylinder cracks? (at least get opinions on the matter) Your thread is about "Myths of the IO360". Don't you think this shock cooling is relevant? You did not say, Facts of the IO360, ONLY, no opinions, lol.

However two things: You get what you pay for. Speaking for myself I can say my advice is worth what you pay for it.

Second and last are you really complaining about the advice and opinions you are getting? You sound disgruntled because no one said anything that makes one engine a clear winner? You do know there is no definitive answer, right. You will have to decide. Get what you want and makes you happy. It will still be a RV and fly great, 150HP or 200HP. If you want speed, reduce airframe drag. I think you already know the answer, so good luck on your engine decision to drag you RV and "respective family jewels" around the sky. I am sure it will be the right one.

You are expecting too much from the forum. It is just a bunch of guys shooting the breeze. Sometimes good stuff comes out. I know I learned something. Its all in fun.

Again I am sorry this was of no use to you and you have to filter. I promise I'll never hi-jack your thread ever again. I would suggest that the info Dave, Milt and myself gave is interesting and useful to others, if not to you, so its not a total waste as you imply. It's like any discussion, it may digress. Again you get what you PAY for. I think you got you money's worth. It's all in good fun, no one is serious. I am sure you are decisive and don't need anyone's opinion anyway. No worries mate.

Cheers George

Diverted but not hijacked

Thanks George,
I wouldn?t say the thread was hijacked. Just a little diverted.
But I must say I was surprised when I found from Kevin Horton?s Spreadsheets just how grunty the Straight Valve was and thought it worth passing on. After all, if Flight Test Engineer Kevin Horton hadn?t noticed it, I assume it wasn?t common knowledge and I know that blokes like you a genuinely interested in such matters.

Diverting the thread myself now, before I bought my IO-360 (Straight Valve) I had the good fortune to discuss engines with Brett Turner, Jon Johanson?s brilliant young engineer who clearly knows his stuff; enabling Jon to stay up for 36hrs straight requires some good engineering.
Anyway, he put me on to Bart at Aero Sport Power and said; quote, ? Bart will get you the same power out of a Straight Valve as Factory Angle Valve and save you 30lb out the front.? ( I think Dan has an Angle Valve from Bart, so who knows what it puts out and that probably contributes to Dan?s Machine?s excellent speeds.)

Well, I won?t quote speed and rates of climbs of my RV-7 as I am not a test pilot and they are probably suspect, but last week I took off in my IO-360 Straight Valve and stayed with my mates Angle Valve RV-8 all the way to 7500?. Level at 7500? he was gradually drifting ahead of me until we both reduce to 2500rpm, after which we just stayed wing tip to wing tip. Made for a great photo shoot.

Both aircraft have Lightspeed Ignition and mine has high comp pistons.

Cheers, Pete.

Testing Image insertion

Just trying to sort out this image inserting.
"Testing, wun, two, tree!"
http://img148.imageshack.us/img148/6117/inflightfodrivex14ut.jpg

fodrv7 said:

It is a shame that so many of these posts turn into pissing competitions on Tail Wheel v. Nose wheel, Aero engine v. Auto engine or the length of our respective family jewel. You end up having to spend so much time filtering the post replies.
Cylinder head cracking. Interesting subject, but is not going to determine which engine you purchase.

Click to expand...

I'm sorry you feel that way, Pete. I'll take the rap for hijacking the thread if you feel a reprimand is in order. George was offering a valid opinion, I just chose to correct what I saw as an error with one small part of it, that's all. As is often the case in open discussion, one person's comments lead another to expand and the hope is that we all get a little more knowledge and hopefully a little richer experience. I've spent a great deal of time on other forums and have learned far more than I ever paid for. Certainly, I had no intention of getting into a pissing contest with George. I have learned a great deal about RVs from many of his other posts, and saw this subject as one opportunity for me to be able to return the favor, as it touches on an area I've looked into quite a bit.

And so it goes- we come to ask questions and learn, and maybe share what we know when we can. Sometimes it gets off the topic originally intended, but that's the price of free advice when you ask for it. Welcome to the www.

Respectfully,
Dave

Another note onShock cooling (oh No)

George and all,

It just came to mind that our company recommended that the power reduction procedure at the top of descent on the 747/767 was to reduce power slightly for a couple of minutes before making the big pull and starting down. This was on a General Electric CF-6 I believe. So, there might be something to this shock cooling stuff, even on the big iron of today. Something about turbine blades.......
Cheers, Pete

Apologies not required.

Dave,
I did not see the Cracked Cylinder discussion as the pissing competition. That was a reference to earlier post about Angled Valve Jealousy.
No, on the contrary and in hindsight, the ?Look after your CHTs? is good educational information.
Besides, I have been guilty of hijacking threads and, I will quietly admit, inadvertently winding up George too. He is a good sport, but sometimes his enthusiasm for aviation gets the better of him. Do love his inputs.

No! The thread went well.
I was just a little surprised however, considering how many kits are out there under construction and how many builders must still be deliberating over an engine choice, that the discussion did not develop into, ?Who can tell me more.?

Thanks All,
Pete.

fodrv7 said:

It begs the question as to why Lycoming made the Angle Valve engine. Was it to provide obese Spam Cans with another 20BHP for Take-off. If so, it has no applicability to RVs.

Look forward to some input on the matter from the Engineers amongst us.

Pete.

Click to expand...

Thanks for your additional comments, Pete. I appreciate them. To address your original question, I don't know what engineering information you're looking for as you appear to have the data you need on the performance curves of the engine. Perhaps perspective is what you're after. My guess is that Lycoming had a market need for precisely what you've suggested. An additional 20 HP at takeoff with 4 burrito-eating adults, or 2 adults plus lots of luggage improves high D/A performance, a distinct plus in some areas.

As for its applicability to RVs, here in the Rocky Mountains, I've departed Leadville (9927' MSL) in the summer with density altitudes of 13,500' MSL (84 deg. F OAT) and headed west toward Hagerman Pass, at 11,925'. Even with only 2250 lb. total weight with the 182, and 230 HP, it was a long, slow climb. RVs are far better performers obviously, but if the winds are blowing, that extra 20 HP could come in real handy if you need it to escape a downdraft. For some of us who live near the tall rocks, the extra take-off and climb power will be used frequently, so I wouldn't go quite as far as saying that it has no applicability to RVs. I guess it just depends on where you live and your mission profile.

Cheers,
Dave

It begs the question as to why Lycoming made the Angle Valve engine.

Click to expand...

Back to the original post.

I originally wanted an RV8 but being one of those wide body burrito munchers mentioned above I was worried about performance off the deck as well as climb performance.

Flew 8s with 180hp and 200hp and the difference in takeoff and climb with full fuel, me and a passenger was noticably better in the 200 hp.

On the website noted below a Cherokee 140 owner (over the span of 2 web pages) does an elegant job of comparing climb performance in his Cherokee with an old muffler having a displaced baffle and a newer more efficient muffler.

He calculates for a 7hp gain he derived a 114fpm climb improvement. If things are proportional that means the extra 20 hp would give an improvement of 300 fpm off the deck.

7 HP increase gives >100fpm climb improvement

Flat Earth

Now here are some good reasons for every HP you can get. Hard to find any dirt with an airport over 3000' in Australia.
Leadville (9927' MSL)?
You have to go to New Guinea for that sort of challenge. Home of the 800' TORA. 20% slope, 7000' Elev. Grass Airstrip. In a Gully. MORA FL145. Afternoon CB.

And I am sure if you are a burrito muncher, you will need all the Burros you can get.

Pete.

I would love the additional horsepower and performance that it brings but I?m a big guy at 6?-5? 250 Pounds so my decision is easy. I?m going with a IO-360. I?m building an 8 so unfortunately I can?t afford the additional 30 or 40 pounds up front.

I?m going to try to compensate by keeping my plane as light as possible. I?ll use a lightweight starter, alternator, avionics, etc.

I did find Milt?s calculations about HP versus climb very informative. Is there any information in regards to weight versus climb? I know there would be many factors that would make it difficult, if not impossible, to provide dead on performance results. (engine performance from one run to the next, density altitude changes, ets.) but it would be very interesting to know what types of increase/decrease in vertical climb speed are seen with weight variations.

I read an article in one of the aviation magazines where a guy went through his plane to reduce as much weight as possible. Even to the point of shortening all of his wiring and eliminating unnecessary wiring loops to reduce the weight. He mentioned that overall he saved several pounds but I don?t think he mentioned what performance gains was achieved.

I think I?ll start a thread specifically to address this issue.

Regards,

Donald
RV-8 Empennage
N-2845 DP Reserved.

One lb of Aluminium = 2fpm

Donald,
This will not be absolutely accurate as the change in ROC with change in AUW will not be linear.
But it will give you an idea of what to expect.

From Vans Website Performance, an RV-8 with 200hp has a Rate of Climb of:
2700fpm @ 1800lb
1900fpm @ 1400lb
So, for a difference of 400lb the ROC differs by 800fpm
Therefore for each 100lb increase in AUW, the ROC will decrease by 200fpm.(800/400=).

Or for every 1lb weight you save in the airframe the ROC will increase by 2fpm.

Pete.

Best O-360

I personally think the O-360-A1F6D (from out of a Cessna 177 Cardinal) that I have in my RV6 is the best overall O-360 to use in an RV. It is a parallel valve 180 hp version with the counterweighted crank (same as the 200 hp angle valve has) but is obviously 30 lbs lighter. With 9:1 pistons (O320-H pistons) in it and ported heads along with electronic ignition & an Ellison TBI injector it makes between 200-205 hp or so. It is also a dual mag version that I have installed a more powerful single Bendix 1200 series mag with impulse coupling in place of the original dual mag unit, and also installed the Lightspeed ring gear trip electronic ignition system on. This engine allows an oil filter & prop governor to be installed without ANY holes being cut in the firewall of the RV6, so it is an excellent combination in the RV6!!!!!!

Just my 2 cents!!

tloof said:

I personally think the O-360-A1F6D (from out of a Cessna 177 Cardinal) that I have in my RV6 is the best overall O-360 to use in an RV. It is a parallel valve 180 hp version with the counterweighted crank (same as the 200 hp angle valve has) but is obviously 30 lbs lighter.

Click to expand...

I think the weight reduction from an angle valve motor is not obvious - the counterweighted crank is responsible for a fair amount of the additional weight. But, it may be a reasonable trade for smoothness if you are really producing 200+hp.

BTW why use an Ellison rather than FI?

Pete

Another point of interest about the two engines is that, at the same power output, the angle valve will burn less gas (according to the pilot get aways, installed in a Husky up to .8GPH). That might be worth it...

osxuser said:

Another point of interest about the two engines is that, at the same power output, the angle valve will burn less gas (according to the pilot get aways, installed in a Husky up to .8GPH). That might be worth it...

Click to expand...

That claim from PG raises a few questions in my mind. I'd be very surprised if there is a 10% improvement in BSFC between the two engines. The angle valve may have better fuel distribution and run smoother, leaner in cruise, but the power output would be slightly less in that case.

Dave

Show me the figures

10% better. BSFC. Show me the figures.

From my earlier post.
"Although, even with the finest pencil I cannot discern any difference in economy from the Part Throttle Fuel Consumption Charts page 3-22 for the IO-360A and page 3-23 for the IO-360B of my Lycoming Operators Manual."

You can get a lot of economy from Electronic ignition and also from High Compression pistons; both with no weight penalty.
Aero Sport Powers balanced components engines is hardly rough.
Pete.

Counterweighted Parallel Valve

Actually the counterweighted parallel valve version is only about 5-6 lbs heavier than the non-counterweighted version. The extra 30 lbs or so that an angle valve adds over most parallel valve versions amounts to 7 lbs per cylinder each + a few lbs for the oil pan + the counterweights, so admittedly the angle valve version is really only 25 lbs heavier than the counterweighted parallel valve version. Still, the counterweighted parallel valve version is much smoother and ideal for use with a CS prop.

I chose the Ellison over the Bendix FI since it was half the cost, is lighter by a few pounds, fits on the bottom of the sump in an updraft configuration just like the original carb did (remember, the engine I had was originally a O-360-A1F6D variant with a carb), and doesn't require a high pressure fuel system. Also, I needed a system that allowed inverted flight operations since I have a full inverted oil system installed. The Ellison has proven to be a great way to go, and in my opinion is slightly better than the Bendix FI system compared to it in both cost and complexity. It also gives about 1" more manifold pressure at 8000' at wide open throttle than the Bendix FI, and about 2" better than a carb!! The mixture distribution is way better than a carb, but not as good as the Bendix FI (surprisingly though it actually comes close to the Bendix FI since my exhaust gas temps are no more than 50 deg in variance between any of the cylinders!

Pete,

Thanks for that information! Every 2fpm adds up. I'm going to try to keep mine as light as possible without sacrificing some of the avionics that I want.

Regards,

Donald
RV-8 Empennage
N-284DP Reserved