Rotax 582 Alternative Possibility

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n3puppy

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Looks like we need THREE definitions of exhausts systems so everybody is talking the same language.

1) Muffler- Sound deadening only
2) Tuned Exhaust - Wide range "Single" cone (diffuser) design to helps pull exhaust gasses out increasing power. Usually has a sound reducing chamber at the end.
3) Expansion Chamber - Narrow range "Multiple cone" design Stage 1 (diffuser) pulls exhaust gasses out, Stage 2 cone (baffle) reflects a wave back to return any excess fresh mixture to the cylinder.

Koyama is describing a wide range Tuned exhaust
Armilite is describing a narrow band Expansion chamber

Both increase the output over a simple muffler.


The standard Rotax tuned exhaust is easy to identify because of the tapered expansion cone leading up to the sound deadening can. The simple muffler only has a straight pipe.

The trouble shooting guide for the 277 specifically calls out that if you change the tuned length of the ROTAX Tuned Exhaust - you can reduce the thrust by as much as 35%


419D5F30-FA23-40D8-98B4-6F29F61BE3FF.jpeg672C73EE-974D-4B91-8D19-1E32F238B03A.jpeg
 
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Yellowhammer

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I built an ICP Savanna (CH701 clone) and powered it with a Rotax 618, I flew it for more than ten years, with one engine seizure (my own fault - long decent with 1/2 throttle), It had slightly better performance than similar 80HP 912 powered Savannahs. It did not suffer from the rev hunting climb/decent problem.
I concur with koyama about this phenomenon, the 618 had sufficient cruise rev torque and reserve power that the revs were stable but early Australian Lightwings were powered by Rotax532s they were very uncomfortable to fly, the revs rose and fell alarmingly with any slight thermal or down draught, the later 583 Lightwings were better, but the throttle hunting was noticible.

What is the best power setting to descend with while flying behind a Rotax 2 stroke?
 

Yellowhammer

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======================

The Sleds went to cageless Bearings also, but too many people complained about them Skidoo switched back. The Cage is what Fails, either from Rust or Heat. You can Coat them to make them last longer, but the Cageless are better account you have almost double the Rollers to handle the Forces! Cageless are Double the Cost. The Rod Shims can Fail also. I think a Ceramic Coating would make them last longer, or use a pure Ceramic Shim.

Now I have never had a Caged Bearing Fail and I'm 63 years old! I have never had a 2 Stroke I'm using Sieze either, except my first 50cc Bike Motor when I was about 10 years old! I have had 2 Strokes on Bikes, Sleds, Lawn Mower, Weed Wackers, Go Carts! The Oil you use, and Ratio you use makes a difference!


View attachment 94922View attachment 94923View attachment 94924
What ratio and oil you use?
 

Yellowhammer

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============================

It's a Twin 4 Stroke. Some Info on it I found. 123.1 lbs Installed! 582UL is about 115lbs. A 618UL (73.4 hp) is about 4-5 lbs heavier than a 582UL, the Rotax Rick 670 (93hp) is about 9 lbs heavier than the 582UL. You don't have any Weight Restrictions other than your MTOW! The Pulsar was introduced in 2001, powered by an 80 hp (60 kW) Rotax 912UL four-stroke or 120 hp (89 kW) Jabiru 3300 powerplant, Continental or Lycoming engines, produced by Pulsar Aircraft. All of them Engines are way heavier than the 582UL, 618UL, 670! Fan and Free Air 2 Stroke Engines are lighter and cheaper than Liquid Cooled Engines!


I didn't see at what rpm that Phaser makes it's 80hp?
The Pulsar I was introduced in 1989 also called the 582 Pulsar. Around 1992, demand for a four stroke engine in a Pulsar caused the designer, Mark Brown, to configure the 582 Pulsar to safely handle the weight of the heavier 911/12 engine, the fiberglass was beefed up and a few other modifications. This model became known as the Pulsar XP.

The company was sold and eventually sold to another company that had to stop making them because the owner died in an airplane crash in South America. He was not flying a Pulsar when this fatality occurred.

There is one more model that was created by the second owners of the company called the Pulsar 100. The 100 has it all the improvements from the previous two designs.

In fact, a person couldn't tell the difference between a Pulsar I and an XP as they are essentially the same aircraft just the XP having heavier glass in the fuselage molds.
 

Yellowhammer

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The Pulsar I was introduced in 1989 also called the 582 Pulsar. Around 1992, demand for a four stroke engine in a Pulsar caused the designer, Mark Brown, to configure the 582 Pulsar to safely handle the weight of the heavier 911/12 engine, the fiberglass was beefed up and a few other modifications. This model became known as the Pulsar XP.

The company was sold and eventually sold to another company that had to stop making them because the owner died in an airplane crash in South America. He was not flying a Pulsar when this fatality occurred.

There is one more model that was created by the second owners of the company called the Pulsar 100. The 100 has it all the improvements from the previous two designs.

In fact, a person couldn't tell the difference between a Pulsar I and an XP as they are essentially the same aircraft just the XP having heavier glass in the fuselage molds.

Also, the 582 is water cooled engine as well.
 

koyama

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I can assure you, with over 15 years experience flying behind and in front of 618 rotaxs that if you don’t connect the cables and you don’t exercise the valves before and after every flight they will carbon up and stick either open or closed on one cylinder, the result that one piston will pick up and seize, naturally you will immediately see it on the EGTs but that only gives you seconds before the inevitable happens. The 618 is a great engine but like all two strokes you have to play by the rules or the result is misery.
I currently own 4 planes that are setup with the 618, and I have owned a total of 11 618s. About half of them have ever had control cables installed. I have never been flying a plane that experienced a 618 failure of any kind, (my logs show I have 3122 hours with a 618) so I do not have direct experience to speak from here. I have never had a RAVE stick in any of my own planes, ever, so I literally have no personal experience to pull from. I have had many people complain about it, and upon inspecting their setups, I have consistently found the same causes, I will list them in order of frequency:

1) Flying with gas that has been mixed more than 7 days. (For premix only.)
2) Incorrect oil. (618 engines are by far the most sensitive to using the correct oil.)
3) Over pitched or incorrect propeller and/or incorrect gear ratio for the speed range of the plane.
4) Incorrect carburetor jetting/setup.
5) Incorrect setup of the oil injection pump.
6) Stuck or incorrectly setup RAVE control cable (if equipped).
7) "Porting" or "polishing" the intake.

1-6 above are straightforward and obvious, number 7 from above is harder to understand, and needs an explanation:
As well as sticking RAVE, it also causes rod bearing failures. The intake has what many people mistakenly call "casting marks" around the edges. These bumps and ridges are there for a reason. They deflect the flow of fuel away from the rod bearing. Without them, the fuel washes the oil out of the bearing and causes failure. This also (indirectly) deflects more of the oil to the transfer ports that are closer to the exhaust side. This provides better lubrication to the hot side of the piston, and keeps the RAVE from getting glued stuck. When I run into a stuck RAVE, it is usually a thick film of oil that is sticky and holding onto carbon and other contaminants, not caked up carbon. (Sure the main thing that brings things to a halt is the carbon, but it is not stuck there on its own, the oil hangs onto it and gets it built up. I have yet to see dry carbon deposits. What I see is oily and sticky.)
If I have a customer with a stuck RAVE, the checklist above will find and correct the cause 100% of the time.

When I see people saying things like, "if you don’t connect the cables and you don’t exercise the valves before and after every flight they will carbon up and stick", I am forced to remind them that the vast majority of RAVEs do not even have any provision to even connect a cable in the first place, and they work just fine.
 

koyama

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... Moderator Edit ...
[/QUOTE]
[EDIT Member Name] ... let's start with respect. Your reply is not setting the right tone for this. This is not a place for disrespect, we all friends here, and we are all after the same goal, to fly cheaply and safely. We are examining differences between aviation and non-aviation setups to understand what is involved in making the conversion of non-aviation engines successful.
Different viewpoints are helpful for understanding a given problem, all input is welcome.

What I am writing im my posts is the information I was given from Rotax when I went to the Rotax certification school. They were very specific about the exhaust, its tuning and design. It was a very large portion of the class, and it is where the cup with holes analogy that I used in an earlier post came from. This information is mostly the internal insight and conclusions that some very smart people at Rotax arrived at over a long time of research and trial and error. However, I must point out that there is more than one viewpoint and side to the coin, and as new things come out, it changes the overall picture.

Also, I will point out that the stock rotax exhaust has the same things as in the "expansion chamber" diagram (image) that you posted. The difference is that it is "folded". There is nothing that says that an expansion chamber can not be folded. It is also of a wideband design, which also makes it look less recognizable.

If you compare to the rotax stock exhaust, you can see that:
1) It has a header, which is part of the Y and sometimes a close in 90 degree elbow.
2) It has a diffuser, the taper from the engine end to the can end.
3) It has a belly, which is the middle section of the can.
4) It has a baffle, which is the front section of the can.
5) It has a stinger, which is the small tapered tube in the can opposite of the inlet (in the lower portion of the picture that was provided by PIK-21).
6) Additionally, it has a silencer which is the rear section of the can.

The stock Rotax exhaust does provide tuning, as others have pointed out, it is true that if you remove it, the engine output will drop by a large percentage. This alone shows that it is not a "muffler". A muffler should have little effect on the output of the engine, and generally in the negative direction. For example adding an "after muffler" to the stock Rotax exhaust has no measurable effect on the output, but only makes the exhaust quieter.
Also, another way to know that you have a tuned exhaust is that when you have something explode in one cylinder, that it gets blown back into the other cylinder via the Y portion of the exhaust as what happens in Rotax engines with the stock exhaust.

Also, another point is that the images you posted are of single cylinder pipes (or multiple cylinders with one exhaust each). To this point, I am describing 2 cylinder engines with a Y pipe. This means that the resonant frequency is doubled. This means that the can is setup to resonate with the intention that it will be blowing back into the OPPOSITE cylinder from which the pulse originated from. (It is also the reason that it is nearly impossible to get a twin cylinder Rotax engine to start and run on one cylinder if one cylinder is not running for whatever reason. And why a misfire in one cylinder is such a problem because it messes up the subsequent charge of the other cylinder.) This means that the chambers are roughly HALF the size of a single cylinder tuned engine. Also, the stock Rotax exhaust has the holes in the large end of the diffuser that tend to virtually reshape the diffuser and belly based on the frequency to hole number and size ratio.

There is a lot going on in the stock Rotax exhaust that people that are used to other designs do not see because it is so different. That is my key point of all of my input here, is that the Rotax exhaust is the brass ring for 2-stroke flight that is blatantly obvious, that everyone misses!
 
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daveklingler

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Hi Armilite. Here's a nice article on the origin of the E-TEC (OMC):


Longevity on any Engine depends on WHO is Maintaining it, Flying or Riding behind it, and the Oil & Octane Gas they are using!
While I agree in principal with that statement, the 600R is marketed at least as having much-enhanced longevity. On the 850 (which the 600R draws from), I've seen several reports of 10,000 miles in a season without any need for a rebuild.

Do similar CC e-Tec's make more HP, Yes, account they use 594cc vs 580cc and a Higher 8000 vs 7750rpm and much Bigger Carbs/EFI than the Older Engines. That 582UL is using Bing 54 36mm Carbs, that 600 e-Tec is using a 54mm Throttle Bodies.
All of the E-TEC engines are primarily direct injection, although the 850 (and, I believe, the 600R) has a throttle body that begins injecting extra fuel at high RPMs.

Unless Skidoo just started using Ceramics on their new Engines, they haven't in the Past. I have been preaching using Ceramics for many Years!
The 850 and 600R ETEC engines use ceramic-coated cylinders. I'm not sure about the 600.

E-Tec's with EFI should get better fuel use, it doesn't really make you more hp. The Engine will Start better and run Smoother! You can add EFI to any older Engine, Ecotrons, Mega Squirt, has EFI Kit's. I have also promoted SFS EFI for Old Singles and Twins. Weber makes a nice DCOE EFI that can be adapted.
Yes, the E-TEC will start in 1/3 RPM.

Skidoo/Rotax has had a Crank Bearing issue for Years.
Yes, the 850 and 600R both have a positive-pressure direct lubrication system to get oil to the crank bearings.

600 eTec 68.2hp@6500rpm. I believe the 600HO is 125hp.
In view of Koyama's observations above, it will be important to find out whether the 600R will run for extended durations at 6500 RPM. For now it sounds like it really needs to be run well into the 7000's or 8000's unless he finds a way to keep the temps down.
 
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daveklingler

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The 600R that I experimented with started running exhaust temps over 1150 when the RPM was dropped into the 6000s at full throttle. That is well into the danger zone. At 7200 RPM, temps were acceptable, around 1000, but after less than 30 hours, a rod bearing failed. I have set this project aside for now, I will get a new crank and come back to it later after I finish reverse engineering the computer. It is clear that the stock software is not going to fly (literally).
This is pretty fascinating. I'm really glad to find someone experimenting with the 600R, especially someone who knows what he's doing.

What about the stock firmware makes it unsuitable for aviation?

Reverse-engineering the computer seems like a daunting job. Are you just trying to figure out how to re-flash it?

You suggested that the 600R is more accurately balanced? I don't see this, there are no trim marks on the crank, rods, or pistons. What information is this statement based on?
That's the claim I've seen in several publicity pieces.


A good point is that adding a computer and GDI to a 2 stroke is a complete game changer, and it would be fantastic to see this applied to a widely available aviation engine. I have experimented with GDI on a Rotax 447. I was seeing about 5-6 horsepower increase with about half of the fuel burn. Just the fuel efficiency alone is a great reason to go with GDI, not to mention that you have very clean emissions.
Very cool. Twice the range is nothing to sneeze at.
 

koyama

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Reverse-engineering the computer seems like a daunting job. Are you just trying to figure out how to re-flash it?
The problem with the stock firmware is that it has several safe and limp modes that have a hair trigger. Also, the fuel tables seem to have a narrow range. If you change the exhaust much, it is extremely easy to cause the computer to flip to safe/limp mode. The safe/limp mode is not desirable for flight at all.
Also, there is no clean path for adding redundancy for critical sensors or outputs. For flight, there needs to be redundancy.
I am not looking to re-flash the stock computer, I am looking to flat out replace it. I am using the oepn-source megasquirt code as a starting point. I modified this code for the GDI 447 project. I modified the code to run on the ATSAMC21J17A instead of the MC9S12. It is configured with 2 processors, power supplies, and drivers on a single PCB. (Fully redundant, it can work 100% with any one dead processor, power supply, or driver.) I also added a CAN bus that sends the same data as the Rotax 912, so it is instrumentation compatible.
 
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koyama

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All of the E-TEC engines are primarily direct injection, although the 850 (and, I believe, the 600R) has a throttle body that begins injecting extra fuel at high RPMs.
Putting fuel into the throttle body/intake is a way to cool the lower half of the engine, in particular the bottom of the piston. A large portion of the cooling that a 2-stroke engine gets is from the fuel. The reason I used the 447 for my GDI experiment is because I calculated that it was not possible to keep the bottom of a 503 or 582 from melting when no fuel is going through the bottom end. (This is the reason for the hole in the side of the 582 (and others) piston and the extra transfer port. It reroutes a portion of the fuel/oil around the wrist pin bearing and provides cooling to the bottom of the piston.) There is no (easy) way to add the equivalent of an oil cooler (like on a 4-stroke) to the bottom of a 2-stroke. With initial testing on my 447, the case temps were well into the 400F area. I added an air scoop to draw more air over the cases, and this eased the issue, but I have no way of measuring how hot the crank and bearings are (yet), but I am sure it is nearing the point at which lubrication failure is a real thing.
 

koyama

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that's called a MUFFLER, which is also a SOUND MODERATOR which a Muffler SLOWS DOWN the HOT EXHAUST GAS to let it COOL before it hits the ATMOSPHERE which is what Makes the Sound SIGNATURE
While I agree with you that the stock exhaust provides some muffling, it is not anywhere as good at muffling as it is at its intended purpose, tuning.
This document as well as my direct experience seem to disagree with your statement that it is just a muffler. All indications show that it is a tuned pipe, just not the kind that we are used to seeing in a non-aviation use due to the situation that tuning for a propeller is unique and different than tuning for nearly any other task:

BTW, I am a big fan of R&D SeaDoo parts. My SeaDoos are loaded with them, and they are fantastic. I have tried some of their 582 specific pipes on my Phantom X1, it was extremely uncomfortable to fly with, but after swapping propellers at least 8 times, I found one combination that was absolutely crazy powerful at full throttle, and I was seeing climb rates well over 1.4 times with the stock exhaust. I gave up and removed them the same day.

Also, if you look at the dyno graph that you posted, it clearly says 77.3HP @ 6300RPM and 78.8 @ 6400. That is 1.5 HP in 100 RPM. It goes on to show 68.2 @ 6500, that is a drop of > -10 HP in 100 RPM! Then it is 68.5 at 6600 or 100 RPM for 0.3 HP change. You have to go all the way to 6900 RPM before you see HP numbers that are larger than at 6400 RPM, and all the way to 7300 RPM before you see bigger torque numbers! This tells you that it is literally impossible to select an RPM between ~6450 and ~7350 with a propeller, it will either under or overshoot, and quite badly with numbers like that. And given that engine's bore to stroke ratio, that is the speed that you will want at cruise, or maybe cruise-climb! That is the kind of instability I am talking about that when coupled to a propeller makes a really terrible power system. It is the very reason you can not use any numbers from such a system when it comes to re-tuning for aviation.
 
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Topaz

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Moderator Note: I've just deleted a triplet of posts that were getting into personal attack territory and name-calling. Disagreement is fine, debate is fine. Please keep it civil and, if you can't find agreement, state your piece as succinctly as possible, and then let it go. You're not going to save the world from error. Don't be this guy:

 

Yellowhammer

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Gentleman,

I am so grateful for the feedback to my question. I really and truly would prefer to fly behind a four stroke with the same weight as the 582. The builders group of the Pulsar are ADAMANT about using only the 582 in the Pulsar I series. The all keep saying more weight up front would be dangerous.
I figured I could gt away with a system that is around ten pounds heavier.

Also, I like to discus and hear opinions about alternative power plants. Hell, I even looked at some rotary engines. They are light and powerful. The only company I cold find with a two rotor was called Vernier I believe and they NEVER emailed me back. They make drone engines for the military.
 

koyama

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The only 4-stroke engine I have found that matches the weight and power of a Rotax 582 is the Weber MPE 750.
If you look at this engine in detail it is obvious why. They did every trick in the book to get the weight down and the power up. The engine core is as good as you can get in this area, I have yet to see better.
They are difficult but possible to keep within 10 pounds of the 582.
They make ~63 HP when they are setup in the lightest possible configuration. You can get more, but you will go over weight. There is also a turbo available, so you can get well into the ~90 HP range even at altitude!
As far as the reliability of the engine goes, it is hard to say. There are too many things that enter the picture.
The top problem I found right off, is that in the chain of gears that drive the water pump, there is a plastic gear. (Part 11 here https://weberpower.com/mpe-cooling-system-water-pump.html) Within the first week, the one I had failed. I made aluminum gears to replace them, this problem is cured.
When I buy used engines to convert, it is common to find bad rod bearings. Rod bearing failure is quite the thing with these. As it turns out, the failure is caused due to running too rich or misfire. The pistons are extremely short, there is no piston skirt to speak of on the sides. (Refer to the diagram here https://weberpower.com/mpe-crankcase-crankdrive.html) This means that the rod is unusually short as well. This combination allows raw fuel to get into the rod bearing and cause failure. Also, the oil gets thinned down as fuel mixes with it. This means that you have to be EXTREMELY careful with the software to never allow too much fuel into the cylinder under any conditions, especially on starting, or you will have a rod bearing failure for sure. One thing I did to help with this, is I installed a small electric oil pump to pressurize the oil system before starting. I also added a sensor to measure now much fuel is in the oil, as well as careful layout of the oil system to avoid bubbles or foam. (The engine is dry sump.) Since I made the software changes and added the pump, I have not had a rod bearing fail, or any other failure.
Also, the electronics are quite the problem. I would never use the stock computer, nor have I found any off the shelf solutions that work. You will either need to make your own computer or you will need to adapt a MegaSquirt.
MegaSquirt | Premier DIY EFI Controller
The earlier conversions I did were using their board design, but I quickly ran into limitations and started making my own board designs. The software can not be made to work without modification, due to the rod bearing fuel contamination issue, you will need to make changes to address this! (The pre-start code that over fuels the engine to start easier needs to be changed for sure!) There are also a few tweaks that can be made, especially to deal with RPM hunting and overshoot. This is easy because the actual throttle butterfly is controlled by the computer. (However, again, the off the shelf MegaSquirt software and hardware is not setup for controlling the throttle butterfly.) I also added some changes to deal with misfire to prevent extra fuel from building up in the cylinder.
If you are good with assembly language and making computers, this is a good way to go. If not, the 582 is likely better.
The MPE 750 project has proven to be a reliable engine, but only after 8 years of trial and error, 6 killed engines and nearly $5000 in fuel for running on a dyno in the process. If you are willing to go through something like this, this engine is the best option I have found to date to replace a 582.
 
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TFF

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Reality is any government contractor is not going to spoil their tasty contract on penny pinching homebuilder. They sell to the government three times what they would have to sell you. If they sold to you, they would have to justify their pricing.

I think it would be best to be own the best maintained 582 than try to rework everything. If that is a flat no, I would do everything to modify the fuselage for a heavier engine. You are going to have to make up the weight with more power, I would shove a Corvair under the nose. Nice ballast shelf in the tail.
 

quick582

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Anytime I see a thread about power adders to the 582 I want to bring up the Revolution Mini-500. I built one of these deadly helicopters and was subjected to 4 engine failures, 2 on the ground and to in air. I am a rated heli pilot and very experienced in 2 strokes so my skills cannot be brought into question. Luckily I was not injured, but I lost my faith in the design and sold it as a parts. The 582 was simply not up the task of max rpm, partial to full throttle operation for extended periods, even with low power settings. Rotax said from the outset it was not a suitable engine, but Fetters used it anyways. Worse still, the stock engine was underpowered, so a tuned pipe was manufactured and sold. It added about 20 HP to the output, but there was no provision for the extra heat generated. The engines would usually seize in less than 5 minutes at full throttle, even if the jetting, oil and fuel were all correct! I spent a lot of dyno time on this engine and pipe, trying to make it work and there was no answer to this problem. After 70 crashes and 9 deaths, most helicopters were parked.
I bring this up because anytime you put a tuned pipe on a 582, there are going to be consequences to its durability. The stock 582 tries to strikes a balance between performance and durability. It tries to takes into account poor fuel and limited carb tuning skills of some operators.
If you are have a more than average understanding of 2 strokes and are careful, perhaps 10% more torque can be brought out with timing, carb, port configuration and clean up and compression. But max RPM must be stock and a factory pipe MUST be used. DO NOT PUT A PIPE ON A 582! Period. Anything else and you should look at a 617 or other engine or you will become an expert in engine out procedures. Just my 2 cents. Oh, if you are thinking about buying a mini-500 deathtrap, it is not a matter of if you will have an engine failure , but when. Dont fly any higher than you are willing to crash.
 

koyama

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I think it would be best to be own the best maintained 582 than try to rework everything.
You have to be careful with this, the problem is the risk of having an incorrect view of the situation. A 582 is actually very reliable and well proven. As I mentioned before, they have no real weak points, they fail because of user error. (It is the operator that is unreliable and unproven.) A plain old 582 will likely exceed the reliability of any non-aviation conversion, 2 or 4 stroke, and even many 4 strokes that are sold for the purpose. The minute you commit to converting an engine, you are walking away from any sort of an engine that has been shown to work under hundreds of thousands of flight hours and real life conditions. You must have the attitude that you are now a test pilot flying an unproven engine. You have no idea how long it will last, or what will explode first when it does go. The only way to build any confidence at all is to run multiple engines on a dyno until they fail and then you know what and when. This can take years of testing to complete.
The correct attitude here is that if you are converting an engine, you have to fully expect that you are walking straight off into the unknown, and reliability is not even part of the picture. Reliability must be proven, so unless you have actual testing results, from well controlled testing, you are blatantly giving up even the concept of reliability.
For the purpose of this discussion, reliability comparisons are relative between conversions, not between conversions and proven engines like the 582.
 

koyama

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If you are have a more than average understanding of 2 strokes and are careful, perhaps 10% more torque can be brought out with timing, carb, port configuration and clean up and compression.
I have seen this, however, I must point out that when driving a porpeller (not a rotor), there is no way to turn up a 582 10% and not give up flyability as I mentioned in some of my previous posts. (However, it is possible to turn one up ~10% and not give up reliability.) You are literally in a trade between power or the correct torque curve you need for flight (flyability), take one or the other, you can't have both. My point is that people often say that the 582 is factory detuned, This is not the case at all. The 582 is factory tuned as good as you can get for a balance between flyability and power to weight with a propeller. As of yet, I have not seen anyone that has demonstrated that they can do any better than the factory did.

What I am seeing is it seems to be all about who can show the best dyno numbers. What I am not seeing is what is most important, I should be seeing is comparison between the dyno numbers and the torque curve of driving a propeller! This critical step seems to be completely ignored! Having good power numbers is pointless unless they are matched to the load! Anyone that understands AC electronics gets the concept of impedance matching, this is the same concept! (This does not make sense when you are in a land based vehicle due to transmissions, clutches, variable belt drives and such, but until I see a variable belt drive or a gear shift on the propeller, I am sticking with impedance matching. An adjustable prop falls just short of qualification.)
Look at the earlier post here, there is a dyno report that demonstrates this problem exactly. (Also my previous comments about this.) High peak dyno numbers tell you that you can only match at a point, not across a range, it is the range that is all important for flyability.
Huge dyno numbers sell engines and sound important, they are great tools for a snake oil salesman. When you build engines that are flyable, you give up the big looking numbers, and you make your product extremely hard to sell because you are forced to compare real propeller driving numbers to some peak number that someone got from a dyno that they can adjust the load as required to find a peak. It is not a fair comparison, and unless you play dirty, you will not make sales unless you have a good reputation to stand on like Rotax (and others) have. There is some argument that using an adjustable propeller can help here, but I have yet to see this demonstrated either.
 
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