Help me understand: UL94 fuel approval vs. compression ratio vs other aspects?

[A64Pilot]

Cars do indeed do things we can’t, the Prius for example will often run at low speeds at full throttle, it does this by pulling the RPM low enough so that even at full throttle the power output matches power required, they do this to minimize friction and pumping losses.

‘We minimize pumping losses by cruising WOT.

Cars back in the day tried “lean burn” first Chrysler the Honda, but couldn’t meet NOX pollution requirements so is lean burn back from its over 20 year hiatus? How did they meet emissions?

Imagine if you will an engine that ran so well leaned out, so smooth that you could always leave the throttle wide open and vary power just with fuel. Been around for over 100 years, guy named Rudolph built it.

Mazda will reportedly build a gasoline fueled Diesel engine called Skyactive-X, original Skyactive is when they copied Toyota in emulating the Atkinson cycle. For those interested Mazda will go electric kicking and screaming, they remain convinced there is more life in a combustion engine, if your anti electric, they are your brand

https://insidemazda.mazdausa.com/the-mazda-way/technology/five-things-need-know-worlds-first-compression-ignition-engine/

So yes lots of things may be possible, but in truth not much has been done in aircraft, and I maintain without a serious re-design there just isn’t much left to be had, all the automotive advances are serious re-designs, not just a new black box

Edited May 16, 2022 by A64Pilot

[Pinecone]

Yeah, lean burn causes NOx emissions to rise.

The problem I have with electric (and hydrogen) they are not energy SOURCES.  You have to make the energy.  They are energy transfer systems.  Taking energy generated one place and using it in another.

Petroleum is an energy source.  You can make engines to burn it straight out of the ground.

TANSTAAFL

Edited May 16, 2022 by Pinecone

[EricJ]

13 hours ago, N201MKTurbo said:

Running super lean mixtures works great in engines that typically run at 20% power or so (auto engines). If that technology was applied to our engines, we could get excellent fuel economy while doing slow flight. But, nobody cares how good our fuel efficiency is while doing slow flight. They want to fly faster! That requires extracting the most amount of power out of our fuel. They pretty much figured that out in the 30s and nothing has changed since.

You should go hang out at a modern race tuning shop and see how much they utilize the sensors and technology to improve power output and efficiency at 100% power.   The old, dumb stuff just isn't anything remotely close to optimal compared to what they're doing these days.

Around here it'd be UMSTuning. 

[N201MKTurbo]

1 minute ago, EricJ said:

You should go hang out at a modern race tuning shop and see how much they utilize the sensors and technology to improve power output and efficiency at 100% power.   The old, dumb stuff just isn't anything remotely close to optimal compared to what they're doing these days.

Around here it'd be UMSTuning. 

What would they do to get more power out of an IO-360 in cruise? or Takeoff?

Car engines are very dynamic. Racing or not. Our engines run in a very static power state. 

 

I had them expand an exhaust pipe for me once when I was repairing my turbo exhaust. They were one of the few places with a hydraulic pipe expander that could form a slip joint out of 304 tubing.

[Shadrach]

2 hours ago, N201MKTurbo said:

But to your point, SureFly already advances the timing at reduced manifold pressures. Yet all we hear are things like "Well it might go a little faster". I just don't think a lot of electronic magic will do that much. From someone who designs electronic magic for a living.

Indeed it does but I don’t know how much.  I’ve not seen a lot of compelling data on the real world benefit.  I can’t speak to exactly why that is but I don’t think that it’s because 20° is already optimal for high altitude cruise.

[EricJ]

7 minutes ago, N201MKTurbo said:

What would they do to get more power out of an IO-360 in cruise? or Takeoff?

Car engines are very dynamic. Racing or not. Our engines run in a very static power state. 

Many race engines run at full power for long periods, e.g., land speed record cars, boats, etc.   Regardless, even the static cases benefit from optimizations that are possible with appropriate sensors and control.   Lycoming made a step in that direction already.  I suspec the market just isn't big enough for a larger step in the gasoline piston engines:

https://www.lycoming.com/engines/ie2

Just about anything designed specifically for aviation in the last twenty or thirty years has FADEC, even the turbines, and Lycoming's diesel:

https://www.lycoming.com/engines/del-120

 

7 minutes ago, N201MKTurbo said:

I had them expand an exhaust pipe for me once when I was repairing my turbo exhaust. They were one of the few places with a hydraulic pipe expander that could form a slip joint out of 304 tubing.

I've known Tony for forever.   He's a top-notch tuner and runs a good shop.   Good driver, too.

[PT20J]

Here's the best set of data I've seen. Note that this was taken in an RV-8 with a Lycoming IO-360 modified for a 10:1 compression ratio. 

Nigel Speedy - Ignition Advance .pdf

[N201MKTurbo]

I like the conclusion of the article. Risk catastrophic engine destruction for low single digit improvements in speed and efficiency.

[Shadrach]

1 hour ago, PT20J said:

Here's the best set of data I've seen. Note that this was taken in an RV-8 with a Lycoming IO-360 modified for a 10:1 compression ratio. 

Nigel Speedy - Ignition Advance .pdf 441.94 kB · 5 downloads

Thank you Skip. This is solid data. I suspect that the main reason SureFly is not demonstrating more a dramatic performance increase is likely due to it being relegated to a single mag. With all of the advance being on half the ignition system, there’s a lot of benefit being left on the table.

[Shadrach]

2 hours ago, N201MKTurbo said:

I like the conclusion of the article. Risk catastrophic engine destruction for low single digit improvements in speed and efficiency.

I think that’s a reasonable conclusion. However, this discussion has been about what is optimal. If you read my earlier posts, I was trying to articulate exactly what was said in the article (quoted below). I would also say that a 6% gain in cruise speed for nothing more than advanced timing is significant.  People on this very form have spent tens of thousands of dollars in mods to achieve less.

“If the optimum timing at each alti- tude is compared, a few things become clear. First, the optimum ignition tim- ing was quite different ROP and LOP.”

“It is not possible to have optimum ignition timing based on rpm and MAP alone; the mixture must be considered. LOP mixtures require a greater variation in timing due to changes in MAP than ROP mixtures.”

Edited May 16, 2022 by Shadrach

[PT20J]

I briefly installed a Surefly on my IO-360-A3B6. I didn't really get to test it because of the cutout problem with some 28v airplanes that affected mine. I didn't want to install the power conditioning hardware as it seemed like a kludge to me, so I returned it. The one thing I did notice is that at 8000' WOT/2500 rpm between peak and 100 ROP EGT it increased the CHTs about 10 -15 degrees. So I concluded that it might force me to run LOP in the summer at altitudes where that was not optimum.

Skip

[PT20J]

The theoretical basis for adjusting the timing is that there is a specific timing for each condition of mixture, rpm and manifold pressure that produces Maximum Brake Torque. According to the people that spent their careers studying these things (Taylor, Heywood) MBT generally occurs when about half of the peak cylinder pressure occurs at TDC and the peak occurs around 14 degrees ATDC.  

What often gets ignored in the discussion is that the optimum is broad -- in other words, you can be +/- 5 degrees from MBT before noticing much effect in efficiency or power and even then the drop off is usually not rapid. I also agree with Nigel's observation in the article posted earlier that it is not possible for a magneto to set the optimum timing if the mixture is variable without knowledge of the mixture.

Here is a graph from Heywood, John B., Internal Combustion Engine Fundamentals,

[N201MKTurbo]

There is one advantage to unleaded AVGAS that has been overlooked. It would permit the use of an oxygen sensor. The combination of Oxygen sensor, RPM and MP would allow much better spark optimization. 

You would need to be careful not to buy any 100LL, it will kill the O2 sensor.

I still think the regulatory hurdles will far outweigh the technical hurdles.

Edited May 16, 2022 by N201MKTurbo

[A64Pilot]

58 minutes ago, Shadrach said:

Thank you Skip. This is solid data. I suspect that the main reason SureFly is not demonstrating more a dramatic performance increase is likely due to it being relegated to a single mag. With all of the advance being on half the ignition system, there’s a lot of benefit being left on the table.

You really should buy an experimental airplane so you can implement your theories and suppositions.

As was stated above TANSTAAFL, by increasing timing, cyl head temp increased, hotter cylinder head temps we know decrease engine life.’I know you bumped your timing from 20 to 25 degrees, we’ve been through that, but do you know why Lycoming depressed timing from 25 to 20 in the first place?

I can tell you, it was for engine longevity, it will still make Certified power with the decrease timing, but will run cooler and therefore last longer. TANSTAAFL

I though the posted article was a very good read and I didn’t see any thing that stood out as incorrect. Funny how two different people will read the same thing and come to two different conclusions. Below is s screen shot of where he summed up his testing pretty well I thought.

 

Edited May 16, 2022 by A64Pilot

[A64Pilot]

I know people with wide band O2 sensors, yes the lead does eventually kill them , but not before you can get a lot of data, it takes hours to kill one, not minutes, and they aren’t super expensive anymore.

I know of one that is installed on a Certified aircraft via a 337

[A64Pilot]

4 hours ago, PT20J said:

Here's the best set of data I've seen. Note that this was taken in an RV-8 with a Lycoming IO-360 modified for a 10:1 compression ratio. 

Nigel Speedy - Ignition Advance .pdf 441.94 kB · 13 downloads

I just noticed, The guy who authored this is a Pax River grad, which means he knows how to write and fly a test program.

I’d hang my hat on this report

[Hank]

For the uninitiated, "TANSTAAFL" is "There Ain't No Such Thing As A Free Lunch." But it's so much faster to write! And it is appropriate is SO many situations!

[A64Pilot]

5 hours ago, Pinecone said:

Yeah, lean burn causes NOx emissions to rise.

The problem I have with electric (and hydrogen) they are not energy SOURCES.  You have to make the energy.  They are energy transfer systems.  Taking energy generated one place and using it in another.

Petroleum is an energy source.  You can make engines to burn it straight out of the ground.

TANSTAAFL

Although arguably electric isn’t a source it can be created by harnessing existing power that isn’t used like wind and Solar, but wind isn’t a source either, it a product of Solar. Electric is however the most efficient practice storage anyone has come up with yet, at our scale anyway.

We used to have a lot of dreamers in the cruising world that were sure that Solar powered cruising was viable. I’d answer| we have had it for thousands of years, sailboats are Solar powered, they didn’t like that answer.

But you just couldn’t make these people understand, they refused to look at the math, like running airconditioning on a boat off of Solar, they were certain it’s possible and would argue all day about it, and some manufacturers were cashing in on their beliefs too, Lagoon I believe built a hybrid electric Catamaran, it worked, just burned more fuel than their regular Cat is all.

But some just want to believe I guess and refuse to be convinced, which is good I think, because for instance I doubt many if any credentialed rocket Engineer's would have believe you could land the first stage of an orbital booster solely on its thrust.

[Andy95W]

3 hours ago, Shadrach said:

 However, this discussion has been about what is optimal. 

And to me, this discussion has shown that our existing magneto timing is optimal.  It gives us good power, from a light weight engine, with good redundancy, at an rpm that provides good thrust from our existing propeller technology.  And it will do so at 75% power for 2000 hours.

If it could be improved significantly at a reasonable price, it already would have been.

[Pinecone]

On 5/16/2022 at 2:12 AM, Shadrach said:

I don’t mean volumetric efficiency ratio.  I mean combustion efficiency ratio (air/fuel). Complete combustion in a gasoline engine occurs at 14.7:1 

Not exactly.  That is the chemical balance point where you have just enough air to burn all the fuel.  But in real life, you still get unburned fuel and free oxygen due to incomplete mixing and combustion.  And, in some cases not enough time before the exhaust valve opens for that combustion to take place.

Ina  perfect engine, you are correct, but in real engines, you need to be leaner than that to burn ALL the fuel.

[PT20J]

1 hour ago, Pinecone said:

Not exactly.  That is the chemical balance point where you have just enough air to burn all the fuel.  But in real life, you still get unburned fuel and free oxygen due to incomplete mixing and combustion.  And, in some cases not enough time before the exhaust valve opens for that combustion to take place.

Ina  perfect engine, you are correct, but in real engines, you need to be leaner than that to burn ALL the fuel.

Ture, but it is even more complicated still. Stoichiometric mixtures have the highest combustion temperature which is above the temperature where chemical dissociation of the combustion products occurs. Dissociation of CO₂ and H₂O molecules frees up oxygen molecules so that it is possible to burn additional fuel. This is why the highest CHT and best power mixtures are rich of peak EGT.

Skip

[Shadrach]

 

 

1 hour ago, Pinecone said:

Not exactly.  That is the chemical balance point where you have just enough air to burn all the fuel.  But in real life, you still get unburned fuel and free oxygen due to incomplete mixing and combustion.  And, in some cases not enough time before the exhaust valve opens for that combustion to take place.

Ina  perfect engine, you are correct, but in real engines, you need to be leaner than that to burn ALL the fuel.

I understand that stoich is theoretical ratio, nevertheless it serves as a reference point on the mixture spectrum.  I could have said "Theoretical" point of complete combustion or "most" complete combustion but it would not have contributed to the point I was attempting to make. 

[Shadrach]

On 5/16/2022 at 6:14 PM, Andy95W said:

And to me, this discussion has shown that our existing magneto timing is optimal.  It gives us good power, from a light weight engine, with good redundancy, at an rpm that provides good thrust from our existing propeller technology.  And it will do so at 75% power for 2000 hours.

If it could be improved significantly at a reasonable price, it already would have been.

That's a reasonable opinion. Especially for carbureted engine operators. Nevertheless, as illustrated in the linked article, there are mixture/MP/RPM scenarios where engine operation would be smoother and more efficient with significant timing advance. The question is not whether that is true, the question is whether there will ever be a safe, practical and certifiable way to incorporate it into our ignition systems.

Edited May 18, 2022 by Shadrach

[Shadrach]

22 hours ago, A64Pilot said:

You really should buy an experimental airplane so you can implement your theories and suppositions.

As was stated above TANSTAAFL, by increasing timing, cyl head temp increased, hotter cylinder head temps we know decrease engine life.’I know you bumped your timing from 20 to 25 degrees, we’ve been through that, but do you know why Lycoming depressed timing from 25 to 20 in the first place?

I can tell you, it was for engine longevity, it will still make Certified power with the decrease timing, but will run cooler and therefore last longer. TANSTAAFL

I though the posted article was a very good read and I didn’t see any thing that stood out as incorrect. Funny how two different people will read the same thing and come to two different conclusions. Below is s screen shot of where he summed up his testing pretty well I thought.

 

Which theories and suppositions are mine???  I theorized about why the new emags seem to be more sizzle than steak as they are currently installed, other than that, most everything I have said was well understood long before I was born. 

I don't think you know exactly why Lycoming added the optional timing spec and neither do I.  Do you have some inside info to share?  The "story" that I have heard/read several times suggests that a particular design of aircraft (I don't recall which) to be produced with a Lycoming 360 variant was exceeding CHT targets in flight testing.  The easy fix was for Lycoming to add an optional timing spec.  It achieved the goal of lowering CHTs.  Apparently TANSTAAFL does not apply in this case. You can retard timing 5° and see reduction in CHTs with no effect on power. Funny how that works.

The TCDS for both the IO and O360 still specify 25° for most variants with 20° being optional on all but two (see attachment).  Per the TCDS (Rev 29 May 4, 2020) the only Lycoming IO360 with a mandated 20° setting is the HIO360D1A (which has 10:1 pistons).  We never "went through that/this" as you state above unless by "through that" you mean suggesting that I was a scofflaw and a "test pilot" who was violating the regs for setting 25° of advance.  You could have checked before saying such things but what's the fun in that.

Just so you understand, in most applications IO360s run quite cool with the original timing spec.  I have a hard enough time keeping #1 and #4 CHTs >300° and Oil temps  >160° in cruise during the cooler months.  I don't want nor need it to run any cooler. I enjoy wide selection of options on the mixture spectrum that I fear might narrow or become less usable if the timing was retarded.

I appreciate your knowledge and experience...your delivery and dismissiveness, somewhat less.

I too think the linked article and the tests therein are well put together.  I disagree that a 6% increase in speed (and nearly 19% increase in power) with no change in fuel burn as a trivial gain. I'm not sure what the author would have considered significant.  Most Aerodynamicists would drool over an easy 6% speed gain on the same fuel burn. How much do you think Mooney invested in the Acclaim Type S to gain a fraction of that on the same fuel burn?

 

Edit:  Apparently I have used a 1000% of my allotted attachment space, so I cannot attach relevant TCDS page.

Edited May 17, 2022 by Shadrach