Sonex-A purchase - What to look for

[WesRagle]

Kai,

Yeah, you're probably right. But I am expecting several advantages. One advantage that I'm really hoping for is much better balanced cylinder to cylinder fueling. If I can get that I should be able to make better power without over leaning, and burning the exhaust valve of, that one (or two) lean cylinders.

Wes

[Kai]

Wes,

Well, yes- should you decide to go for an efi system with en ecu having sequential control og each injector, balancing the egt´s should be well within reach. However, each cylinder producing the same power is another matter altogether. First you need an induction system that allows each cylinder to suck in the exact quantity of air. Then you need an exhaust system that gives exactly the same amount of back pressure to each cylinder. This to warrant even filling. If you manage this over the entire rpm range you are close to an even power loading of all cylinders.

Good luck with that, as it has not been done yet, at least not as far as I know. You will need an induction plenum at least 1.3 times the volume of each cylinder- perhaps something close to what Edge Performance does with their EP conversion of the R912 + + range. And probably also an exhaust extractor system of considerable size: where to tuck that one away under the cowling will be an exercise in dexterity.

Please keep us informed about your progress!

[Jester504]

NACA did at least two studies in the 40s investigating the relationship between CHT, EGT, valve temperature, and valve condition. They had to create custom valves with thermocouples in them. The results proved that valve temperature correlates nicely with EGT (but 150-200 F lower) and not CHT as many think.

Here's a link to the first: https://www.abbottaerospace.com/downloa ... rmocouple/

[WesRagle]

Hi Jester,

That's interesting.

Where is the link to the second :-)

Wes

[BRS]

Wes,

Well, yes- should you decide to go for an efi system with en ecu having sequential control og each injector, balancing the egt´s should be well within reach. However, each cylinder producing the same power is another matter altogether. ...

With EFI balancing EGT's is not quite the right idea. The thought of having exact equal temps and or power on four separate (essentially) engines (cylinders) is a dream. With EFI what you can do, and do very well, is to have each cylinder run the same fuel ratio at at-least a small range of power band. So the better test is what some call the Gami Test. That is, tune the cylinders so that they all reach peak EGT at the exact same fuel flow. So though they may all indicate different temps at say 150 deg ROP, they will still all be on the same page and running in unison.

This is what I've learned from running the SDSEFI on three different engines (Subaru EJ22, Rotax 9XX franken motur, Lyc IO-360).

[Kai]

A dream indeed: how true!

However, I did not want to be a naysayer and squash all his ambitions. If he wants to go efi, which I personally believe is the right way to go- I have flown behind these things since 2011- by all means: have a shot at it. But don´t get too disappointed with the level of success you have achieved after having forked out considerable quantities of good money.

Another thing altogether is that this thread started more or less an information to all concerned partiets about the challenges one could meet when working to get temperatures on the loose under control in differential air cooled small aero engines. On a general basis I would say that we´re still not there.

Anybody with excess of say at least 500 issue free hours in the air please tell us about your findings and solutions!

[Bryan Cotton]

Anybody with excess of say at least 500 issue free hours in the air please tell us about your findings and solutions!

I'll suggest this thread as a good place to do it:
viewtopic.php?f=7&t=7279

My 270 hours were not trouble free. Mostly I chased oil temperature issues. I do still plan to add the B model exits. I'm chasing the ability to do pattern work when it is hot out.

[WesRagle]

Hey Bryan,

I'll suggest this thread as a good place to do it:
http://www.sonexbuilders.net/viewtopic.php?f=7&t=7279

Let's start a new thread. Based on recent banter I think a good title might be:

"The perfect VW (Chasing the Dream)"

What da'ya think.

Anybody with excess of say at least 500 issue free hours in the air please tell us about your findings and solutions!

If you listen to Jeff's pod cast on SDS EFI, "Episode 58 - "SDS EFI for your AeroVee" (ref. http://www.sonexflight.com/58/sonexflight_e58_jun2019.mp3), Peter claims (if I'm remembering correctly) 600 hour of trouble free flying. However, as a maintenance item, he refreshed his heads every 200 hrs.

However, I did not want to be a naysayer and squash all his ambitions.

Impossible :-)

There is a lot to learn here.

Here's a link to the first: https://www.abbottaerospace.com/downloa%20...%20rmocouple/

I had never read a study about valve temperature. That pretty much proves that VW flyers don't need to look at CHTs when they find burnt valves. The problem is more likely high valve temperature and the best proxy we have for that is EGT. Maybe VWs just have to be "fuel cooled" under heavy load. That can be best done with balanced fuel distribution and that can be best done with EFI.

Pressure differential between the upper and lower plenum should be about 9 inches of water at full power, which a well designed and implemented "firewall" forward should be able to easily achieve at about 100 MPH.

I'd like to know how to do that!

Like I said, a lot to learn.

Anyway, the perfect VW? Take a RevMaster, replace the ignition with AeroVee ignition, replace the charging system with a Great Plains 35 Amp (Harley) alternator, add EFI, and find some gold paint that will stick :-)

Wes

[Jester504]

Where is the link to the second :-)

https://www.abbottaerospace.com/downloa ... -cylinder/

That pretty much proves that VW flyers don't need to look at CHTs when they find burnt valves. The problem is more likely high valve temperature and the best proxy we have for that is EGT.

Generally, I agree, but it's important to point out that while the valve temperature correlates with EGT, the absolute EGT measurement itself isn't really precise, so it still doesn't tell us directly or indirectly what temperature the valve actually is. You just know that peak EGT is roughly peak valve temp, not peak CHT. Theoretically, you will cool the valves by being either richer or leaner than peak EGT. Also, to my understanding, it may not be the temperature of the exhaust gas by itself burning the valves. The valves could have other problems, like not rotating properly, that cause the heat to build-up uncontrollably without shedding it in the normal way.

[WesRagle]

Generally, I agree, but it's important to point out that while the valve temperature correlates with EGT, the absolute EGT measurement itself isn't really precise, so it still doesn't tell us directly or indirectly what temperature the valve actually is.

Agreed. But... at that one point, stoichiometric/peak, EGT has special value. If you can use EGT to tune an EFI unit such that EGTs all peak at the same mixture setting, that's pretty cool. EGT then get's demoted to a cross check parameter and from that point forward you can operate your engine by mixture according to flight regime. I think that, along with an EGT limit set below spec, will help me manage/keep me from abusing the engine.

Wes