2 Stroke Cylinder & Case Porting for more HP!

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Armilite

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Torsional vibration, whirl and misc flex can do all sorts of weird and unpleasant things. Not all two strokes used in aircraft were designed to have a prop hung on the end of the crank. Some are fine, others are not. A lot of direct drive car engine conversions need an extra bearing to be reliable.
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You state what a PSRU can do, but not How it Solves these 2 Stroke Engine Problems! Could we use some New PSRU's today, Yes. There are very few made today. Rotax has already dropped the A Drive, and for the 582UL the Drive of choice is the C or E Drive, it's only a matter of time for they drop the B Drive. Nobody that I know of makes a New Belt Drive for the 185UL or 277UL. ACE Aviation $560 says they make one for 377-447-503, but have a 6 month wait period. There is a guy advirtizing on ebay $950 some Belt Drives for 377UL - 582UL both Pro4 and Pro8, Challenger $1250 has a Belt Drive for a Pro8 Case.

I just never seen a PSRU that Solved any 2 Stroke Engines problems is all. I have seen Belt Drives cause some 2 Stroke problems though. Over tightening the Belt has melted the PTO Seal and the Crank Bearing Plastic Retainer. That's Why, you should only use Crank Bearings with Steel or Nylon(Best) Retainers.
 

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pictsidhe

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Armilite,

Put aside PSRU / Porting and Polishing etc for the moment. Maybe this requires a separate thread and this is not a desire to commander this one. State of the Art 2 strokes in the Sled arena ( possibly Outboard as well ) have 3 major features that seem to be the template of their high-performance and a level of reliability at those power levels. The 3 ingredients are Reed Valve, EFI / Transfer Port Injection and or DI, and a Power Valve on the exhaust side. Of the manufacturers in the Av-Space, their are those with Reed and EFI systems, but up to this point no one in that space has a Power Valve ( except on converter/vendor who is using Sled Engines as a base ) . The question is why? weight? complication? cost? all of the above? Even in flight applications the RPM's 2 stroke flight engines are operating in are not that different then sleds.

Look forward to your and all 2 stroke enthusiast responses on these questions.

My Best,
Anthony
Reed valves mainly help low rpm power and starting, peak power is much the same. Same with exhaust valves. The power absorbed by a prop varies with the cube of rpm, so low end power isn't really needed on an aircraft.
Injection does great things for emissions and economy. No power benefit over correct carburation.
 

Armilite

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Armilite,

Put aside PSRU / Porting and Polishing etc for the moment. Maybe this requires a separate thread and this is not a desire to commander this one. State of the Art 2 strokes in the Sled arena ( possibly Outboard as well ) have 3 major features that seem to be the template of their high-performance and a level of reliability at those power levels. The 3 ingredients are Reed Valve, EFI / Transfer Port Injection and or DI, and a Power Valve on the exhaust side. Of the manufacturers in the Av-Space, their are those with Reed and EFI systems, but up to this point no one in that space has a Power Valve ( except on converter/vendor who is using Sled Engines as a base ) . The question is why? weight? complication? cost? all of the above? Even in flight applications the RPM's 2 stroke flight engines are operating in are not that different then sleds.

Look forward to your and all 2 stroke enthusiast responses on these questions.

My Best,
Anthony
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I'm open to talk about anything. First let's talk about your Reed Valve. In 2 Strokes, the Piston Port is at the bottom for making Power, then comes the Reed Port, then comes the Rotary Valve per the Racers I have talked too. Has there ever been a fair test done to prove it, Not that I have ever seen. In Old Sled Racing the 292 Class was the most popular, all were Piston Port Engines about 25 different brands, except the Yamaha 292 was Reed Fed. The Skidoo 292's were making around 55hp and the Yamaha 292's were making around 70hp. Were they using the same CR, same Max Rpms, same Size Carbs, same Tuned Pipe, I doubt it. Once they brought out the Rotary Valve Engines they blew the Yamaha 292's out of the water. But, like I said was it a Fair Test.

For 2 Strokes used on Airplane's, the only Engine Company to offer EFI is Hirth. A guy named John ??? adapted Hirths EFI to his Rotax 503. I know it took him a year to get it perfected, but I think he said it made about 1.0gph difference. There is some aftermarket places offering it today, Ecotrons, is probably the best Package for now, and there is an Open Source EFI, called Mega Squirt, and few other startups. There is a guy on here from Russia I think starting to make some EFI packages also. I have been working on and off on my own idea's. I got too many projects going on, so only devote a little time here and a little time there.

The New eTec stuff is more for better Emissions, than making more HP. Each Year, they come out with a little more CC. Skidoo last I knew was up to a 1000cc. Now, I have one of the Heaviest Sleds ever made a 1994 and 1995 Yamaha Vmax 600's, a Twin, rated 95hp and they do a little over 105+mph, last time I looked down at the Speedo! They say 115mph. Nobody, in their right mind needs to be going 100+mph on any Trail Sled. These Newer Sleds are much lighter and 160+hp.

Nobody, that I know of has used any of these newer Skidoo/Rotax Designed 2000+ Sled Motors on a Plane. None of them has the Provisio 8 needed for a Gear Drive. The 550F(2003-2018) does have it on the Bottom Case Half, but not on the Top Case half. There are some guys using some Yamaha Sled Motors on Para Planes around 125hp. They have to use an Exspensive PSRU CNC Billet Cover to Adapt a Gear Drive. The New eTec's, use a Greased Crank Bearing with Plastic Shields and still Fail in Sleds at around 4000 miles seems to be the consensus I get. IF, you use 40mph as an Avg. Trail Speed, that's 100hrs. At Airplane constant Rpms for Hours I would bet that would be the first Failure Point to show up. I like their EFI but wouldn't work on Planes, it has a limp mode built in, Power Valves with New Oils aren't a problem today, Bigger CC/HP is nice, but they haven't been Tried and Proven in Airplane use, which is at Continious Rpms use for Hours. You do have a Standard say 600 and a 600HO, 800/800HO, 1000/1000HO. But, You still have to reduce their Rpms to around 6500rpms for Endurance. Like a Stock 800HO is [email protected] At 6500rpms it probably still makes 120-130hp. With a better Tuned Pipe you could probably make 10-12hp more. If they were upgraded to them "Hybrid Crank Bearings", Ceramic Balls with Steel Races that could Help, but exspensive.

Power Valves were only used on the 618UL, but were a Failure Point back then. Some were made of Aluminium, some Stainless Steel. They used mainly Standard 2 Stroke Oil at the Time so got carboned up real fast. With the new Synthetics out today, that wouldn't be a problem. Power Valves are Adjustable to some Small Degree, but were mainly Designed for Higher Rpm Sled Engines. They don't even come in till around 6000rpms I believe, so not really Helpful for Plane use. Just a Failure Point to worry about. If you was going to run the Engine in say a Stunt Plane turning it say 8000rpms for Max HP, then RAVE Valves would be good to use. But for our Max 6500rpms used on Standard Planes, I wouldn't use them, one less Point to Fail. IF, you flew a Rotax 670(RAVE) agianst a 582UL at the same HP setting, the 670 gets about (1.0) gph better per Rotax Rick who builds them.

People tend to forget, just because you can make more HP at a given Rpm doesn't mean you have to use it all to go Faster. Like the Stock Rotax 582UL with Rotaxs Muffler Dynoed [email protected] and with R&D's Tuned Pipe, it Dynoed [email protected] With the R&D Tuned Pipe it still made [email protected] Rotax Rates it's 582UL at 6500rpms, so that's 750rpms lower making about the same 64HP. At 6250rpms where the Stock 582UL really makes it's Max 64.7hp, it made 75.9hp with the Tuned Pipe!

Gee, what did that 618UL make for HP that Cost even more $$$$ than the 582UL, [email protected]

The 618UL with an R&D Tuned Pipe was [email protected], made [email protected]! Rotax wouldn't have Sold many 912(80hp) that cost about $4500+ more than a 618UL cost at the time.
 

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Armilite

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yes.....only thought about it.
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It's always good to, Think, that's how we come up with New and Hopefully better Ideas. A Billet Case or just a better Single Case isn't that hard of a project once you, Think, about what different ways you could do it. CNC isn't really needed, but it's nice to have now that it's reasonabilly Priced! People were making things with Manual machines for many years before CNC came along. Some, are still using basic Hand Tools. Today, with Cheap 10" Table Saws($150) and Special Cheap Saw Blades($28) you can cut Aluminum on them. Welder for Welding Aluminium($800). CNC comes into play if you want to do Contouring, some things you can't do manually, but you can get by.

Hmmm.
#1 Could you make a better Single Case by just Cutting up a 1993+ 503 Case, take the Front & Rear halfs and Weld back together. Gives you the same Head/Cylinder Bolt Pattern as the 277, gives you a Pro8 Case Front for the B & C & E Gear Drives. Gives you the Back Half that a Free Air Case can be used, or use a GPL Electric Start can be added? Tripples and Quads have been made that way.

#2 Could you maybe do the same to a 550F Case, and maybe cut the Top Front off a 503 Pro8 case and Weld onto the 550F Case Top Front and have a Pro8 550F Case with a Reed Cylinder or make a Single out of it?

#3 Could you just take some Precision Cut Billet Blank Plate Stock (2) Pieces, lets say roughly 8" x 8" x 3" and Clamp together layout your Head/Cylinder Bolt Pattern on Top & Deck, Then Layout your Case Bolt Pattern on the Bottom, then Layout you Front Pro8 Bolt Pattern and Front Seal Area, then turn around and Layout the Rear Seal Area and bolt pattern. Then after that's done, then Bolt together and Bore the Centerline. Then Machine for Crank Wheel Clearance and Bearings. After your done with the important stuff, work on Milling/Cutting off any excess you don't need.
Use the Free Simple 2D CAD from www.emachineshop.com to layout your Templates and just glue them on. A Manual Mill with a DRO could also locate your Holes and Drill and Tap all at the same time.

#4 Could you make a Case that just Bolts together like this VW Racing Case?
 

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Armilite

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A preliminary Billet Single Case with Pro8 added. You can see it needs more height, so each Block needs to be at least 3.25". Think of something like this 80cc Billet RC Engine Block, only Scaled up. You probably need more height than Width. I can't get my 503 Front view CAD file to open up, to do an overlay.
 

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proppastie

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#4 Could you make a Case that just Bolts together like this VW Racing Case?
Though about that too...bolt up plates and have a ball bearing pinned crank, not plain bearings.....good Drill press and crank press would all be needed. Or good drawings and any local machine shop with a mill.

Would take some analysis to size the plates and bolts based on the HP.
 

Armilite

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Yamaha, an early adopter of reed valves, didn't put them on the TZ250 racer till the 80s.
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They had a Reed Fed Cylinder on a 292 Single in the 70's. "VINTAGE 292 RACE PIPES
We have two pipes available for the popular 292 Yamaha single engine. The full race pipe is developed for modified Oval racing and delivers 70 HP at 9000 RPM with Full Race Porting, Reed Valve intake and a larger Carb. We also have a milder pipe that is turned for 7500 RPM and delivers 50-55 HP depending on Cylinder Porting. This pipe is very popular in One Lunger Sno Cross Enduro Races or for Vintage Trail Riding and Restorations."

Some good views of the 70's Yamaha 292 Reed Fed Cylinder Single apart. You can see it has better Porting than Skidoo's Singles.
https://www.youtube.com/watch?v=q2EOFzEZi0k

Skidoo made a Prototype Rotary Valve Single (78mm x 70mm) 334.6cc, 39hp in 1969 with just a Muffler that never got put into Production. Basically, Half a 670 that came out in 1992, 23 years later and made Stock [email protected] There were Small 354 & 454 Rotary Twins released that put them in the winners circle. The 1971 Blizzard 340 Single was the Highest Production HP released Factory Single at 36hp for Skidoo. That 1969 Rotary Valve Single with a Good Tuned Pipe would have been around 58hp at Sled 7750rpms! At Ultralight 6500rpms around 45-47hp with a Tuned Pipe.

I had a chance 3 years ago to buy one of these 292 Yamaha Sleds that was For Sale close by me, whole Sled for $400. Wish now, I had went and looked at it. There is two different Yamaha 292's, a Reed Fed Cylinder, and a Piston Port Cylinder.
 

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pictsidhe

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Yamaha were putting reed valves in road and dirt bikes for over a decade before they put them in their hp-is-king 250 road race bikes. The RD250 had them 12 years sooner than the TZ. It's a reasonable bet that Yamaha knows far more about two strokes than everyone on HBA?
 

jbiplane

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A bit offtopic, but sometimes dreams and expensive technologies not so expensive.

We make simple tuning for serial parts. First 3d scanning, make 3d model and finally mill it in 5-axis.
This way 172cc cylinder with integrated head - see on video will weight below 1000 grammes, originally 3400.

One cannot believe, but this milled cylinder become better cooled and have more TBO hours compare stock.
More radical approach mill of cylinder of top tange bullet. Exist some good alu alloys with vanadium and
silver which are superior any used for mass production.

We do experimental production of crancases of foam aluminum (at moment very expensive here and subject
export regulation). The part of foamed aluminum have ~1mm solid surface layer and foamed inside.
Today exist a bit worse, but cheaper approach 3d metal printing. May be already affordable for amateurs.

BTW if someone is interested in expert engine tuning exist cheap, but very good software
http://vannik.co.za/EngMod2T.htm
We got 2 licenses and it worth each cent :)
 
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pictsidhe

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I knew about open cell Al foam, using NaCl. I googled closed cell foam and found this article.
Supposedly patented by Canadians so we could find out the details.
Is the Russian foam similar?
 

jbiplane

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Is the Russian foam similar?
A bit offtopic, in this thread. So will short.
I saw it first here in ~1980+- Alu Mg and Ti and know a few, just use for some light parts to reduce milling

Ptoduced at least in 4 variants
20x1200x600 mm flat and bended sheets with closed surfaces
closed surfaces castings with porocity up to 85%
powder metalurgy - premixing by layers different and thermo explosion in molds like pop corn

and structures with big bubbles - the last picture was taken by google search, dont know origin, but close to last variant
Foam 1.jpg
 
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pictsidhe

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Interesting. A blowing agent. The canadian process mixes air in with a rotating paddle. Do you cast in hard points for fasteners etc?
 

jbiplane

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The canadian process mixes air in with a rotating paddle. Do you cast in hard points for fasteners etc?
We use here magnetic mixers. It can mix any metals better than paddles :)
Yes, sure. I use steel or hard aluminum inserts for bearings and threads in magnesium, foams and composites.
 

AJLiberatore

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Yamaha were putting reed valves in road and dirt bikes for over a decade before they put them in their hp-is-king 250 road race bikes. The RD250 had them 12 years sooner than the TZ. It's a reasonable bet that Yamaha knows far more about two strokes than everyone on HBA?
Pictsidhe,

You made me dust off cobwebs here :). Yes The RD350LC ( unobtainium {sort of} here in the U.S. ) and the RZ350 from the Mid 80's with the Cats had Reeds, and the YPVS ( Power Valve ). Yes their history of being on their game is real. A bit small and the prices are pricey now that everyone is restoring them, however I often wondered why someone didn't try a 3 cyl. variant of the RD350/LC/RZ architecture for Av-Use. The only thing missing an EFI type system.

Tangent DNA: The "Ryger Engine", Torq-X by Husqvarna, KTM's new Port Injection ( branch of Husky if my memory is correct ). If it wasn't for the patent cost and Gen Av liability, their is a lot going on in the 2 stroke arena, and by using some or all of what I mentioned in the right combination might make a better mouse trap for us. Sadly are market is so small, if they were used in various applications to get the run rates up, (minus the EPA in the equation ) such an effort might have a running start....
 

pictsidhe

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The RDs etc probably wouldn't last too well in aviation use. A little highly tuned. Maybe the YPVS with the powervalve locked down. Yamaha France entered TZ750s into the bol d'or a few times. Despite being detuned, they never managed a finish. They did humiliate everything else before going bang, though.

I'm a bit out of touch with bikes, but there is likely some cylinders out there that might be useful to us. Something like a scooter that is going to spend a lot of time at high throttle.
 

BensenB8M N521LW

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I'm still a fan of the McCulloch 0-100. 4 cyl. opposed fires 2cyl at a time for 72HP at around 4GPH on my Bensen B8M N521LW. Some ported and added a dual carb to get 90HP but this weakened the centercase and caused big problems later on...
 

pictsidhe

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Outboards are likely the best hunting ground for engines to repurpose. High duty, weight sensitive. The main thing that I dislike about them is that they tend to have a long watercooled exhaust port: more cooling load.
 

jbiplane

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Outboards are likely the best hunting ground for engines to repurpose. High duty, weight sensitive. The main thing that I dislike about them is that they tend to have a long watercooled exhaust port: more cooling load.
Vous avez raison! Exactly. I know few sucsessfull local experiences based on local spares:
Inline 2-cylinder 210cc engine based on outboard crancase "and crankshaft + 2 cylinders of chainsaw
Inline 2-cylinder 350cc engine + 2 motorcycle cylinders.
The only part to make was adapters crancase to cylinder.

My idea is to use Yamaha crankshaft (3 cylinder inline and 4-cylinder V90) + Rotax 503 cylinders.
This way you will need only mill crancase... Resulting engine will be better balanced and easier to start than opposites.
Yamaha 3 cylinder.jpg
 
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