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Electronic solutions to modifying glow engines of all sizes to gasoline

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Electronic solutions to modifying glow engines of all sizes to gasoline

Old 09-24-2022, 12:22 AM
  #876  
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Originally Posted by Glowgeek View Post
Here's another one I've been thinking on. Will the stihl solenoid control airflow? If it will then we could use checked crankcase pressure to the tank and control that pressure with the solenoid used as a programmable bleed off valve . No crap trap, no air pump, no additional battery mah. Hmmmmm
It would... But I have no idea about its longevity or its linearity, Probably with a dry airflow service life is less than optimal (movement and no lubrication) but crankcase pressure always contains some oil mist. That should ensure proper sealing.

I could see that working, but probably you will need an additional sensor to control the actual sensor, because I think the RPM will have influence on the gasflow. Especially with 2-strokes, where the throttle affects crankcase peak pressure.
Old 09-24-2022, 02:37 AM
  #877  
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Originally Posted by 1967brutus View Post
It would... But I have no idea about its longevity or its linearity, Probably with a dry airflow service life is less than optimal (movement and no lubrication) but crankcase pressure always contains some oil mist. That should ensure proper sealing.

I could see that working, but probably you will need an additional sensor to control the actual sensor, because I think the RPM will have influence on the gasflow. Especially with 2-strokes, where the throttle affects crankcase peak pressure.
Concept

Using checked crankcase pressure with the solenoid tee'd into the line between the check valve and fuel tank. Crankcase oil would drain through both the check valve and the solenoid to provide lube. The solenoid would serve as an adjustable pressure relief valve. Our existing fuel channel curve would become a tank pressure curve, tied to throttle position.

I have no idea of validity of the idea but it seems like it would provide varying fuel pressure just as muffler pressure does. The final pressure curve would be tuned in flight, just as with our current configuration.

The headroom for additional fuel during unloading is an unknown to me. It seems there would be additional tank pressure/fuel pressure available as the prop unloads, above ground peak rpm, without further adjustment of the solenoid/relief valve but I'm not sure if it would be enough to meet fuel demands. It may require some compromises.

As usual, I've probably over simplified the whole thing and I really don't think the concept will control engine fueling with the granularity of the current setup. It may however work good enough, getting rid of the severly over rich midrange common to glow/gas conversions and get rid of that pesky crap trap.

Last edited by Glowgeek; 09-24-2022 at 03:02 AM.
Old 09-24-2022, 08:51 AM
  #878  
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Thats basically what OS did with their EFi system, and they used the remote needle valve to set the bias pressure.

Originally Posted by 1967brutus View Post
I could see that working, but probably you will need an additional sensor to control the actual sensor, because I think the RPM will have influence on the gasflow. Especially with 2-strokes, where the throttle affects crankcase peak pressure.
Thats the issue with crankcase blowby, especially with 4 strokes decreasing with rpm... and with OS's EFi system, you had to adjust the tank pressure to optimize the performance... and that was never a constant either... the raise and fall of tank pressure that follows rpm / exhaust pressure has always worked well, and trying to artificially recreate that can be done, but to what level of accuracy, and reliability... the more ancillary equipment you add, the more it affects the serve life, and reliability... but Isolating the contaminates in the exhaust pressure feedback to the tank, would be an improvement though, get rid of the crap trap.
Old 09-24-2022, 09:25 AM
  #879  
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Would blowby come into play using the concept I described? Checked crankcase pressure alone should provide plenty of excess pressure at all rpms. That minus whatever the solenoid is programmed to bleed off is the tank/fuel pressure.

Last edited by Glowgeek; 09-24-2022 at 10:03 AM.
Old 09-24-2022, 11:24 AM
  #880  
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Originally Posted by Glowgeek View Post
Concept

Using checked crankcase pressure with the solenoid tee'd into the line between the check valve and fuel tank. Crankcase oil would drain through both the check valve and the solenoid to provide lube. The solenoid would serve as an adjustable pressure relief valve. Our existing fuel channel curve would become a tank pressure curve, tied to throttle position.

I have no idea of validity of the idea but it seems like it would provide varying fuel pressure just as muffler pressure does. The final pressure curve would be tuned in flight, just as with our current configuration.

The headroom for additional fuel during unloading is an unknown to me. It seems there would be additional tank pressure/fuel pressure available as the prop unloads, above ground peak rpm, without further adjustment of the solenoid/relief valve but I'm not sure if it would be enough to meet fuel demands. It may require some compromises.

As usual, I've probably over simplified the whole thing and I really don't think the concept will control engine fueling with the granularity of the current setup. It may however work good enough, getting rid of the severly over rich midrange common to glow/gas conversions and get rid of that pesky crap trap.
No, it would not... It would provide variable fuel pressure, but NOT like the muffler does. The difference is that the electronically controlled pressure does not follow the RPM (unloading), ONLY the throttle position. It would basically be the same as a fuel curve without muffler pressure.
This is an important difference.
The thing is, there are TWO corrections on fuel: One for the throttle position, which is now our fuel curve, the other correction is "automatic" by means of the muffler pressure, and it corrects for unloading. The issue with that one is, that I have no idea how that "unloading-correction" works WRT numericals. I know it works, but I have no idea if that pressure is linear to RPM, squared to RPM or maybe even cubed. Or maybe it is none of the above. So I would not know how to describe that correction mathematically. And that is a problem, which can only be solved with LOTS of testing, and it might even require a LUA script ecause a Taranis can do a lot, but it does not have mathematical functions.

And let's face it, that craptrap, it really is not such a monstrosity that avoiding it would justify all that testing and programming. One of the principal goals was mainly to keep things SIMPLE...
Old 09-24-2022, 11:29 AM
  #881  
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Originally Posted by John_M_ View Post
Thats basically what OS did with their EFi system, and they used the remote needle valve to set the bias pressure.



Thats the issue with crankcase blowby, especially with 4 strokes decreasing with rpm... and with OS's EFi system, you had to adjust the tank pressure to optimize the performance... and that was never a constant either... the raise and fall of tank pressure that follows rpm / exhaust pressure has always worked well, and trying to artificially recreate that can be done, but to what level of accuracy, and reliability... the more ancillary equipment you add, the more it affects the serve life, and reliability... but Isolating the contaminates in the exhaust pressure feedback to the tank, would be an improvement though, get rid of the crap trap.
Nope... In a good functioning engine with a good liner and ring condition, my tests have shown that blowby is near zero at full load, and remains near zero all the way down to a certain RPM (in my test engine, the 91 ASP fourstroke that RPM was between 3500 and 4000) where it suddenly strongly increases and then also remains more or less constant.
I believe this to be the combustion pressure forcing the ring to seal up against the liner above certain loads/RPMs, and I have no idea if every engine responds the same, but I DO know by logical deduction that ingestion of dirt WILL disturb the parameters of this behaviour..
Old 09-24-2022, 12:03 PM
  #882  
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Originally Posted by 1967brutus View Post
No, it would not... It would provide variable fuel pressure, but NOT like the muffler does. The difference is that the electronically controlled pressure does not follow the RPM (unloading), ONLY the throttle position. It would basically be the same as a fuel curve without muffler pressure.
This is an important difference.
The thing is, there are TWO corrections on fuel: One for the throttle position, which is now our fuel curve, the other correction is "automatic" by means of the muffler pressure, and it corrects for unloading. The issue with that one is, that I have no idea how that "unloading-correction" works WRT numericals. I know it works, but I have no idea if that pressure is linear to RPM, squared to RPM or maybe even cubed. Or maybe it is none of the above. So I would not know how to describe that correction mathematically. And that is a problem, which can only be solved with LOTS of testing, and it might even require a LUA script ecause a Taranis can do a lot, but it does not have mathematical functions.

And let's face it, that craptrap, it really is not such a monstrosity that avoiding it would justify all that testing and programming. One of the principal goals was mainly to keep things SIMPLE...
Well, I don't understand why not. With a variable speed pump (engine) pushing some air into the tank and some air through a needle valve (solenoid), it seems logical that more pressure would develop in the tank as rpm increases. I can't see how it would simply push all that extra air out through the solenoid without some kind of rise in pressure. I thought we had seen Chris prove that theory just a few days ago by varying the speed of his air pump while using a needle valve tee'd into the line. All I'm proposing is to try the solenoid as an air bleed instead of the needle valve.

I'll do some pressure testing tomorrow.

Last edited by Glowgeek; 09-24-2022 at 12:09 PM.
Old 09-24-2022, 03:49 PM
  #883  
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Originally Posted by 1967brutus View Post
Nope... In a good functioning engine with a good liner and ring condition, my tests have shown that blowby is near zero at full load, and remains near zero all the way down to a certain RPM (in my test engine, the 91 ASP fourstroke that RPM was between 3500 and 4000) where it suddenly strongly increases and then also remains more or less constant.
I believe this to be the combustion pressure forcing the ring to seal up against the liner above certain loads/RPMs, and I have no idea if every engine responds the same, but I DO know by logical deduction that ingestion of dirt WILL disturb the parameters of this behaviour..
With a single ringed piston, as rpm rises, combustion pressure does in fact seal the ring against the cylinder wall, and against the ring groove in the piston, that was my statement blowby decreases with rpm, so tank pressure would drop when the throttle was opened, and with sustained rpm... 2 stroke crankcase pressure would respond to rpm changes, rise and fall with rpm.

Shaker pump, or engine driven vane pump??


Old 09-24-2022, 04:11 PM
  #884  
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Originally Posted by Glowgeek View Post
Well, I don't understand why not. With a variable speed pump (engine) pushing some air into the tank and some air through a needle valve (solenoid), it seems logical that more pressure would develop in the tank as rpm increases. I can't see how it would simply push all that extra air out through the solenoid without some kind of rise in pressure. I thought we had seen Chris prove that theory just a few days ago by varying the speed of his air pump while using a needle valve tee'd into the line. All I'm proposing is to try the solenoid as an air bleed instead of the needle valve.

I'll do some pressure testing tomorrow.
That would work with a 2 stroke... 4 stroke you would have to close the solenoid valve to increase tank pressure as the blowby would be greatly reduced with rpm... just enough to operate a diaphragm pump with the reciprocating pulses caused by the piston moving up and down through an unchecked crankcase breather... you could add a second one way check valve in the crankcase to draw air in, and the piston would displace the crankcase volume out the breather. that would work throughout the entire rpm range then.
Old 09-24-2022, 04:29 PM
  #885  
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Originally Posted by John_M_ View Post
That would work with a 2 stroke... 4 stroke you would have to close the solenoid valve to increase tank pressure as the blowby would be greatly reduced with rpm... just enough to operate a diaphragm pump with the reciprocating pulses caused by the piston moving up and down through an unchecked crankcase breather... you could add a second one way check valve in the crankcase to draw air in, and the piston would displace the crankcase volume out the breather. that would work throughout the entire rpm range then.
Yes, I failed to mention the inlet check needed for 4 strokes. I have a set of Saito twin check valves well suited for the purpose.

Edit: Looking back at my posts it appears I failed to mention that I was talking specifically about 4 strokes. Sorry about that.


Last edited by Glowgeek; 09-24-2022 at 05:19 PM.
Old 09-24-2022, 08:13 PM
  #886  
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OK... Lots of theory flying back and for the so here is a little CCD (Crude Canadian Data) for you - Put my e-pressure setup to the first test - Seeing if it could indeed supply pressure as intended .. The setup is a simple brushed speed control with a linear curve (0-100%) on a mixed channel from the throttle stick. at idle - no pump - at full throttle - set bleed needle to about 50mmHG. Started up and Quick tune showed my fuel curve is now is a very flat S curve - much flatter than before - throttle response is very impressive as I think the fuel pressure is now leading the ramp up and its acting a bit like a accelerator pump - looking back at video I think I can decrease my throttle servo slowdown. I know I am static but the engine runs better than It ever has - At 50mm I have leaned the top end solenoid pulse by 30-40% and idle is unchanged -

So.. I know Bert has reservations as this is not going to forward load changes but the next stage is to take the control of the pump off the radio curve and give it to the RPM curve (using a simple MPU) - I have found some good engine load vs prop RPM data and think I have the math figured for a first cut at a "control strategy" based on Static RPM and unloading rise. Control shown by the pump systems very good and I'm hopeful a "simple" system will work with only a few parameters needed...

Not the best video but was busy today and in a hurry . This was the very first run - Last runs with tuning were approaching the "magic" zone.

https://www.youtube.com/watch?v=s6qn...ature=youtu.be

Last edited by Cat 1; 09-24-2022 at 08:55 PM.
Old 09-25-2022, 12:06 AM
  #887  
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Yes, I do have my reservations,,,
I do applaud the research, and learning from research is ALWAYS a good thing, but...

I am not getting it: We started out with a fairly simple, and above all cheap system, intended to run SMALL engines in SMALL planes on gasoline. We're now over-complicating it for the sake of getting rid of a 5 dollar craptrap, and we're losing versatility (I don't see how I would fit an additional airpump and the battery to power it in a 60"wingspan trainer), we're increasing the number of adjustments, and all that to get rid of a craptrap the price of, basically, an old syringe...


This is my trainers craptrap. 10 cent item, and on average I need to drain it once per afternoon, at the end of the day. No biggie. Just pull the cap and leave it to drip, it does its own draining and cleaning.

This is the craptrap of my SpaceWalker. 5 Bucks item. Due to the more aerobatic nature of the plane, there is a bit of fuel reflux. Yet, on average, I empty it only about every 2 months...Engine is in use since about March 2017

This is the craptrap for my ASP FT160. It has not been emptied EVER (Engine is in use since spring 2018...) And in the pic it looks fuller than it is, because I "sloshed" the crap around pulling ut from its fittings. Content maybe 5 ml, still 25 to go before it needs cleaning, which at this rate would be another 16 years)

This is the reason why (I think...) the twin has such a low crud-production: Muffler taps are connected to a T-junction, and most of the dirt shoots back and forth from one muffler to another.

That's just 5 1/2 years of practical experience there, and after those 5 years, I really don't see the issue people have with the craptrap. We have lived for decades with engines that would slime a plane all over, big and heavy fieldboxes, large amounts of expensive fuel, messing about with glowplugs and their power supply, fuel compositions (Castor or synthetic, how much Nitro) and what not, but a craptrap is a problem? Trust me, it is there but properly installed you barely notice it. Depending on plane and flight envelope, I even have one that is TOTALLY maintenance free, because it is self-emptying.

There are points where I would like to think that "better" is the enemy of "well enough"...

That's just my 2 cents...
Old 09-25-2022, 03:52 AM
  #888  
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Question wrong pressure?

Are there any "full size" equivalents where the fuel tank is pressurised?
As far as i know. most use a fuel pump .
So why not focus on finding a small fuel pump instead and avoid all the plumbing and risk of leaks that come with a pressurised tank system?

Old 09-25-2022, 03:59 AM
  #889  
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Default yea but..

Originally Posted by 1967brutus View Post
There are points where I would like to think that "better" is the enemy of "well enough"...
That's just my 2 cents...
Assumtion is the mother of all f-ups
While i share your doubd a pressurised tank is the way to go, trying might teach us things and then once there is a good working "proof of concept" see if it can be done simpler.

Old 09-25-2022, 05:39 AM
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Bert, we won't replace the simplicity of a Craptrap but the pump/control could be a packaged unit smaller than a 2oz crap trap and worth about $20. From what I saw yesterday - maybe no complicated tuning will be necessary and I think it will just plug in like a servo and get a 0-100 signal. The pump draws 100ma and won't need its own battery. It might be as simple as a Servo sized box with 1 air outlet and a built in needle valve to set max pressure.

I think there are other dynamics coming into play that I don't fully understand yet but the engine ran very well and so much different. I think just supplying a constant linear pressure helps by taking away any engine performance related variables effecting fuel supply - For example - if an engine goes lean and sags(even slightly) - muffler pressure drops - worsening the condition. Vice versa is also true and I did see this yesterday that if the engine is set too rich - it can't clear itself as pressure picks up.
I did some more thinking and I really don't think we even need to reference RPM to fuel pressure and here is why.. if we can assure a set pressure at a "power setting" - unaffected by any other running conditions - the Carb venturi will take better care of changes of engine "flow". This was proven out by a couple of things. The engine now responds better to throttle (pressure is now able to lead) -and my curve is now very "flat" . Consider this is a flat curve with a fixed orifice - no mixture compensation in the carb. From what I saw on this very early test - I think that a simple "e-pressure" unit MIGHT be able to eliminate the need for the solenoid in some installs and simply retain the stock carb.

Busy today with a swap meet (trying to raise "research funding" and not come home with more stuff than I'm taking) - but next steps will be a good tune and then some prop swapping to see it my hunch plays out. - then - get one flying..
Old 09-25-2022, 06:04 AM
  #891  
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Originally Posted by cmulder View Post
Are there any "full size" equivalents where the fuel tank is pressurised?
As far as i know. most use a fuel pump .
So why not focus on finding a small fuel pump instead and avoid all the plumbing and risk of leaks that come with a pressurised tank system?
Many fuel setups in aviation are "pressurized" but never for engine supply directly - They usually use forward airspeed to generate some sort of head pressure on the tanks just to make sure fuel "moves" properly and in some cases (with bladder style tanks) it prevents collapse of the tanks. Cant remember the set pressure (1.5 to 2 psi I think) but the popular "king air" aircraft I have worked on, have a intricate little vent system that has a couple of "heated" tank vents that are angled into airflow and on the bottom of the wing .

Most RC tanks get pressurized but its only .5 psi - Some (YS engines) get pressurized much more. A small fuel pump would be doable (RC turbine) but I think control of pressure/flow would be an issue. It works in the turbine as its the "driver" and everthing else happens because of the amount of fuel applied - with an IC engine - it must follow a number of other drivers.
Old 09-25-2022, 10:00 AM
  #892  
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Default Muffler Pressure Tests

The Saito 200Ti has a straight header with a crimped down end. The pressure tap is near the end.

The Saito FA-72 has the cast "trash can" muffler. The pressure tap is in the expansion chamber area.

The OS 35 FP is a stock unit. The pressure tap is in the expansion chamber area.


Old 09-25-2022, 08:06 PM
  #893  
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Originally Posted by Cat 1 View Post
OK... Lots of theory flying back and for the so here is a little CCD (Crude Canadian Data) for you - Put my e-pressure setup to the first test - Seeing if it could indeed supply pressure as intended .. The setup is a simple brushed speed control with a linear curve (0-100%) on a mixed channel from the throttle stick. at idle - no pump - at full throttle - set bleed needle to about 50mmHG. Started up and Quick tune showed my fuel curve is now is a very flat S curve - much flatter than before - throttle response is very impressive as I think the fuel pressure is now leading the ramp up and its acting a bit like a accelerator pump - looking back at video I think I can decrease my throttle servo slowdown. I know I am static but the engine runs better than It ever has - At 50mm I have leaned the top end solenoid pulse by 30-40% and idle is unchanged -

So.. I know Bert has reservations as this is not going to forward load changes but the next stage is to take the control of the pump off the radio curve and give it to the RPM curve (using a simple MPU) - I have found some good engine load vs prop RPM data and think I have the math figured for a first cut at a "control strategy" based on Static RPM and unloading rise. Control shown by the pump systems very good and I'm hopeful a "simple" system will work with only a few parameters needed...

Not the best video but was busy today and in a hurry . This was the very first run - Last runs with tuning were approaching the "magic" zone.

https://www.youtube.com/watch?v=s6qn...ature=youtu.be
That works.... pressure response is better than I expected... only consideration is the added components, and something else that can fail... it does work rather well.... if you can get it all into one small box, to keep things tidy... its a move in the right direction to get rid of that crap trap, so you gain a few components, and you loose the trap bottle.



Originally Posted by Glowgeek View Post
Yes, I failed to mention the inlet check needed for 4 strokes. I have a set of Saito twin check valves well suited for the purpose.

Edit: Looking back at my posts it appears I failed to mention that I was talking specifically about 4 strokes. Sorry about that.
Yes, from the 300T, and it worked rather well... the odd fire 130T had the diaphragm pump with the same check valve.

It certainly would keep things simple
Old 09-26-2022, 08:18 AM
  #894  
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Originally Posted by Cat 1 View Post
Many fuel setups in aviation are "pressurized" but never for engine supply directly - They usually use forward airspeed to generate some sort of head pressure on the tanks just to make sure fuel "moves" properly and in some cases (with bladder style tanks) it prevents collapse of the tanks. Cant remember the set pressure (1.5 to 2 psi I think) but the popular "king air" aircraft I have worked on, have a intricate little vent system that has a couple of "heated" tank vents that are angled into airflow and on the bottom of the wing .

Most RC tanks get pressurized but its only .5 psi - Some (YS engines) get pressurized much more. A small fuel pump would be doable (RC turbine) but I think control of pressure/flow would be an issue. It works in the turbine as its the "driver" and everthing else happens because of the amount of fuel applied - with an IC engine - it must follow a number of other drivers.
Thats exactly how the wing tanks are vented on the J3... with a small header tank in the nose... full scale, the header tank is tiny, just a tube reservoir.

These are the tank covers to the model J3... fully functional vent system... which doubles as the fill and overflow as well.

Please don't re-post these, thank you.
https://ibb.co/6YMdzWL
https://ibb.co/4MrSL27
https://ibb.co/zSf2gXB
Old 09-26-2022, 10:21 AM
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I'm curious what you fellas think about how using crankcase pressure to create tank pressure will affect engine lube. If I was using max tank pressure and regulating I wouldn't worry because of low flow, but I'm not. Whether I use the solenoid as a programmable air bleed or just use an open Tee fitting to bleed off pressure there will be a lot of waste air travelling out of the engine. I fear it will carry away the needed oil mist.

Here's the 220 back plate modded for using check valves. They both leak but that's not critical. Once installed I realized I may not need both checks, just one for checked air inlet. If I don't use an outlet check the crankcase would pull air in through the inlet check and the pressure line, reducing overall tank pressure and perhaps retaining more lube in the crankcase.


In order to set up this system to provide roughly 1 psi at wot I'll start and run the engine off of muffler pressure first while monitoring the checked crankcase output pressure. It should just be a matter of selecting the correct size orifice to bleed off excess pressure. The solenoid will be used for fueling as normal on this go around. If this works as good as muffler pressure the crap trap is history for $10, the cost of an inline check valve and a plastic tee fitting. I may need to add a remote needle to control bleed off pressure, or maybe a piece of brass tubing that can be crimped, not sure yet.

Here's my thinking; When using a fixed air bleed orifice (Tee'd into the pressure line), the more air volume pumped the higher the tank pressure will be. I'm not sure if the pressure rise with rpm will be linear or exponential, but I'm guessing exponential based on my muffler pressure tests.

Last edited by Glowgeek; 09-26-2022 at 11:16 AM.
Old 09-27-2022, 04:44 AM
  #896  
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Meanwhile: How to do more of the same and still keep it somewhat "interesting":


Still a first and rough attempt, the OS/Graupner Wankel (Mk I) running on gas, with the electronic mixture control.

The changes are extremely remarkable:
-Barely any crud from the muffler anymore
-It appears to be quieter, which I think has to do with no more afterburning in the muffler.
-Fuel economy has improved by at least a factor 3 if not 4. I was really amazed that the same fuel tank that normally would be empty within 5~7 minutes even at mainly part load, now allready feeds the engine for 20 minutes at the same throttle regime, and at least 1.3rd still left.
-Idle and partload, no more fuel spray from the carb, and idle now happens at throttle openings as used from a normal reciprocating engine, instead of "half open and slobbering rich".
-Noticably lower running temperatures, at least at idle and part throttle, although I have not yet had the balls to keep it flat-out for prolonged periods of time, because lower than "searing hot" still is pretty hot. Yet, the cooling ring remained cooler, and it had all apearance that after reducing throttle, temperatures dropped quicker as well.
I tried to measure the "core temp" and the highest reading I could get was 148 deg C by IR-gun, at which temperature the engine did not show ANY signs of overheating, but yet... Brrrr,
But what is VERY noticable is the lower exhaust temperature at partload. I held my hand at 3"behind the tailpipe to see how much oil the engine is spewing, and that was no problem up to about 8K RPM.

It has all appearance that a wankel, just like so far all the engines I have done, needs time to "settle" on the changed lubricating conditions, because throughout the test the engine started to run better and wanted an ever so slightly leaner mixture.
The oil in the engine is less diluted by fuel therefore more viscous and less voluminous, and less polluted by soot. It appears this reduces internal friction.

It is an entirely different engine now... Still a bit tricky to get going, still very sensitive to the mixture, but all in all it still is improving as well.

I saw a peak of a touch over 13K (13050) with an APC 9 x 5, which should translate to 0,47 hp, and that is a fraction more than I have seen from this engine so far.
Previous peak was 12960. That was in December last year, so lower temperatures and higher air density.

I'm happy...

Last edited by 1967brutus; 09-27-2022 at 04:50 AM.
Old 09-27-2022, 08:40 AM
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Nice progress Bert.
Old 09-27-2022, 08:53 AM
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Originally Posted by Glowgeek View Post
I'm curious what you fellas think about how using crankcase pressure to create tank pressure will affect engine lube. If I was using max tank pressure and regulating I wouldn't worry because of low flow, but I'm not. Whether I use the solenoid as a programmable air bleed or just use an open Tee fitting to bleed off pressure there will be a lot of waste air travelling out of the engine. I fear it will carry away the needed oil mist.

Here's the 220 back plate modded for using check valves. They both leak but that's not critical. Once installed I realized I may not need both checks, just one for checked air inlet. If I don't use an outlet check the crankcase would pull air in through the inlet check and the pressure line, reducing overall tank pressure and perhaps retaining more lube in the crankcase.


In order to set up this system to provide roughly 1 psi at wot I'll start and run the engine off of muffler pressure first while monitoring the checked crankcase output pressure. It should just be a matter of selecting the correct size orifice to bleed off excess pressure. The solenoid will be used for fueling as normal on this go around. If this works as good as muffler pressure the crap trap is history for $10, the cost of an inline check valve and a plastic tee fitting. I may need to add a remote needle to control bleed off pressure, or maybe a piece of brass tubing that can be crimped, not sure yet.

Here's my thinking; When using a fixed air bleed orifice (Tee'd into the pressure line), the more air volume pumped the higher the tank pressure will be. I'm not sure if the pressure rise with rpm will be linear or exponential, but I'm guessing exponential based on my muffler pressure tests.
It had no adverse effect on the twins... placement of the check valves will help to keep oil in the bottom engine... and since the engine relies on blowby for lubrication you need to vary the rpm... At the beginning of the days flying, I always inject 5cc's or so of oil through the breather just to make sure there's plenty of oil on the start.

Runs some tests on your stand, and then check the oil content in the bottom end... You remember that post on the OS GF40, where they ran the engine full throttle for long periods in a UAV, and the rockers / shafts wore badly... they were running 40:1 fuel oil mix... not enough oil vapor reached the topend, and that was with the PCV system they designed into the engine to improve upper cylinder & valve train lubrication.


Originally Posted by 1967brutus View Post
Meanwhile: How to do more of the same and still keep it somewhat "interesting":

Still a first and rough attempt, the OS/Graupner Wankel (Mk I) running on gas, with the electronic mixture control.

The changes are extremely remarkable:
-Barely any crud from the muffler anymore
-It appears to be quieter, which I think has to do with no more afterburning in the muffler.
-Fuel economy has improved by at least a factor 3 if not 4. I was really amazed that the same fuel tank that normally would be empty within 5~7 minutes even at mainly part load, now allready feeds the engine for 20 minutes at the same throttle regime, and at least 1.3rd still left.
-Idle and partload, no more fuel spray from the carb, and idle now happens at throttle openings as used from a normal reciprocating engine, instead of "half open and slobbering rich".
-Noticably lower running temperatures, at least at idle and part throttle, although I have not yet had the balls to keep it flat-out for prolonged periods of time, because lower than "searing hot" still is pretty hot. Yet, the cooling ring remained cooler, and it had all apearance that after reducing throttle, temperatures dropped quicker as well.
I tried to measure the "core temp" and the highest reading I could get was 148 deg C by IR-gun, at which temperature the engine did not show ANY signs of overheating, but yet... Brrrr,
But what is VERY noticable is the lower exhaust temperature at partload. I held my hand at 3"behind the tailpipe to see how much oil the engine is spewing, and that was no problem up to about 8K RPM.

It has all appearance that a wankel, just like so far all the engines I have done, needs time to "settle" on the changed lubricating conditions, because throughout the test the engine started to run better and wanted an ever so slightly leaner mixture.
The oil in the engine is less diluted by fuel therefore more viscous and less voluminous, and less polluted by soot. It appears this reduces internal friction.

It is an entirely different engine now... Still a bit tricky to get going, still very sensitive to the mixture, but all in all it still is improving as well.

I saw a peak of a touch over 13K (13050) with an APC 9 x 5, which should translate to 0,47 hp, and that is a fraction more than I have seen from this engine so far.
Previous peak was 12960. That was in December last year, so lower temperatures and higher air density.

I'm happy...
Interesting, big improvement... whatever happened with that runtronic ignition?

Last edited by John_M_; 09-27-2022 at 08:56 AM.
Old 09-27-2022, 10:22 AM
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1967brutus
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Originally Posted by John_M_ View Post
whatever happened with that runtronic ignition?
That one is in another project that is halted right now (but not stopped or forgotten).
Old 09-27-2022, 11:15 AM
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Originally Posted by Glowgeek View Post
Tee fitting to bleed off pressure there will be a lot of waste air travelling out of the engine. I fear it will carry away the needed oil mist.
I wouldn't know why... Every fourstroke I know of has a totally open crankcase ventilation, no lube problems there.

What I WOULD do however, is connect the crankcase vent to a Tee (the horizontal bar of the Tee, to be exact) and connect the other end of that horizontal bar via checkvalve to the fuel tank.
The vertical bar of the Tee can be routed out of the plane any way you see fit.
This will leave the normal crankcase ventilation (which we all know does not harm the engine) unimpaired, but the pressure pulses of the crankcase will end up in the tank and remain there due to the checkvalve.
That should result in a fairly stable tankpressure if you ask me, because it is not the blow-by or ring seepage that generates the tank pressure, but just the breathing action of the crankcase, and any air going to the tank should theoretically originate from outside. Not from the crankcase...

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