Two stroke conversions and pipes

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akwrencher

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So, after several years of traveling for work way too much, I'm back home full time, remaried, and working hard to catch up on the many projects around the house and yard. I've started reading HBA again, and thinking about some of the fun projects I want to do. A couple years back, I mentioned on here about wanting to try a conversion of a v4 outboard powerhead, just to see if it would work. I have a 1.6 liter one to play with. It's old but runs good and would be fine for use on a test stand. Toying with the idea of direct drive so I did some googling and found an interesting site about pipes. Here is the link for those who also are into making a pipe. I haven't used this guy's program, just passing along what I found so far.

http://www.dragonfly75.com/motorbike/portsMS.html
 

BBerson

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I don't know if a tuned pipe is much use at direct drive rpm. Don't see em on the giant R/C models.
 

akwrencher

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I don't know either, to be honest. Still, a well designed exhaust never hurts. My understanding thus far with exhaust tuning leads me to suspect that it could still help. The goal would be to get power down low. It could be that a complete rework of porting would be needed, in which case a redrive would be in order. Still, it could work. Outboards have to have a bit of grunt to get up on step. I'm not holding my breath on creating a practical new conversion. Just something I have wanted to try for a while. I'll learn some things in the process, and that will be worthwhile.
 

BBerson

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Does the outboard have a tuned pipe?

I know a guy flew a Mercury outboard (article Sport Aviation). I think his name was Lyle Forsgren.
 

pictsidhe

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Has your power head got individual exhaust ports? Ideally, you'd resize and retime the ports to your new rpm, but a pipe will still help without doing that.
 

akwrencher

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From what I gather, the higher rated version of the same block had more of a tuned exhaust and higher compression. Mine is 90hp, not sure of the exact rpm, I think it maxes out around 6000, give or take a few hundred. It's a lot of displacement for the power compared with say a rotax. Thats the reason i wanted to see what it could do around 3000 rpm.It's the older crossflow evinrude. The exhaust systems are somewhat different than land based engines, so it's hard to compare. Will be interesting to see what happens. If it's possible to bring the power band down low enough, It could work....in theory. What it does in practice though I have no idea.

On a side note, most of the time I spent away for work was in your neck of the woods, at Boat Haven, and Liberty Bay Marina in Poulsbo. Kept thinking I would pm you and see if I could check out your projects, but never had the time. Did make it to the little museum at the airport there once though.
 

Armilite

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So, after several years of traveling for work way too much, I'm back home full time, remaried, and working hard to catch up on the many projects around the house and yard. I've started reading HBA again, and thinking about some of the fun projects I want to do. A couple years back, I mentioned on here about wanting to try a conversion of a v4 outboard powerhead, just to see if it would work. I have a 1.6 liter one to play with. It's old but runs good and would be fine for use on a test stand. Toying with the idea of direct drive so I did some googling and found an interesting site about pipes. Here is the link for those who also are into making a pipe. I haven't used this guy's program, just passing along what I found so far.

http://www.dragonfly75.com/motorbike/portsMS.html
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Generally 2 Strokes aren't good in Direct Drive mode for Plane use, they idle at 2000rpms, and they normally don't make much HP on the low end.

What is the Stock HP at rpm's?

http://www.mk5cortinaestate.co.uk/calculator3.php

To make your max HP potential you need to use an 11.2 to 11.8cr with a Good Tuned Pipe Designed for your rpm's!

To Design a Tuned Pipe you need:

Engine CC:
Engine Duration: ??? (Based off Rod Lenght ???mm, Stroke ??mm, Exhaust Port Height in ????mm)
Exhaust Port Width(mm): ???mm
Exhaust Port Height(mm): ???mm
Exhaust Port Length(mm): ???mm
Target HP: ?? (??hp Stock)
Target Rpm: ???? (????rpms Stock)
Coefficient: 2.0 (1.0 - 2.0) 2.0 gives a Wider Power Band!
Metal Thickness: 1mm = 0.03936996" is the default Thickness. Material Thickness Used, does not affect Tuned Pipe Numbers, just Weight and Service Life and ease of Welding. No thicker than 3.175(.125").

A good Exhaust Port Duration Calc.
http://www.csgnetwork.com/timingportdurationcalc.html
 

BBerson

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I picked up an old O-100 McCulloch 4cylinder drone engine. Same as 1.6 liter.
It is rated 72hp at 4100rpm. Weighs 66 lb basic engine, 83 lb with accessories.
I don't think it's worth messing with something this old and not readily available, other than to look at for ideas.
 

akwrencher

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I'll post some pics of the configuration of the ports soon. Going to be a couple months before I can start, just doing some research in the mean time. Mostly I was curious what the more experienced in two strokes thought/knew about the info on the site I linked.

Even if it needs a psru to be useful, it could still be an interesting project. Keep in mind, this really is primarily a project to learn things. I hope to learn some first hand info about two strokes, aircraft conversion in general, and whatnot. I have many years experience fixing engines of all kinds, planes, boats, cars, bikes, atvs, small engines, outboards, etc., but very little actual experience with engine mods. It's time to remedy that sad situation:)

I've already read through all the 2 stroke threads here a couple times, so broadening my searches. Any good suplementary links would be apreciated.

These particular engines are a bit thirsty at around 9 or 10 gals. Per hour at wot. My experience with outboards though tells me that at a modest cruise it could be a reasonable 5 to 6. These engines are rated for ling life at the power they produce. Can run wot all day long without damage, and are already set up to run in the lower rpm ranges, similer to Rotax UL versions. As I said though, this is a test stand engine, I have no plane to put it in yet. If it worked out good on the stand I might be able to get my hands on an airboat to play with it some more. Or learn some things to apply to future projects.
 

cheapracer

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Generally 2 Strokes aren't good in Direct Drive mode for Plane use, they idle at 2000rpms, and they normally don't make much HP on the low end.
This is just nonsense, not one claim is even close to being true, in fact they are ludicrous, yet you keep posting similar every time the subject comes up. Your information source is wrong, it's as simple as that.

http://motocrossactionmag.com/bike-tests/you-asked-for-it-motocross-actions-two-stroke-versus-four-stroke-shootout-yamaha-yz250-versus-yamaha-yz250f

Q: WHICH BIKE MAKES THE MOST HORSEPOWER?

A: No comparison. A Yamaha YZ250F four stroke produces approximately 36 horsepower at 11,300 rpm, while a YZ250 two-stroke makes on average 46 horsepower at 8500 rpm. That is a ten horsepower advantage at peak for the two-stroke (at much lower rpms).

Q: WHICH BIKE MAKES THE MOST TORQUE?

A: Pit pundits will always tell you that horsepower doesn’t matter as much as torque. They wax on about the torque advantage that a four-stroke engine has over a two-stroke. Guess what? A Yamaha YZ250F four-stroke makes 20.1 foot-pounds of torque. Are you ready? A YZ250 two-stroke pumps out 30.6 ft-pounds. For comparison purposes a 450 four-strokes produces approximately 34 foot-pounds.

Here's some 500cc class comparisons where the 2 strokes kill the 4 strokes, and at much lower rpms ..
 

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cheapracer

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I picked up an old O-100 McCulloch 4cylinder drone engine. Same as 1.6 liter.
It is rated 72hp at 4100rpm. Weighs 66 lb basic engine, 83 lb with accessories.
I don't think it's worth messing with something this old and not readily available, other than to look at for ideas.
Have you seen those things run? Scary, there is something inherently wrong with their design, I guess for short life drone use it matters not.

akwrencher, without a proper pipe your fuel usage will suffer as the fuel is simply shot down the exhaust. The basic principle of a chamber is to return that charge that has escaped down the exhaust and to stuff it back into the cylinder, it is in fact a supercharger using wave pressure.

So you increase power and improve fuel consumption, albeit within a narrow rpm range (not to be mistaken for powerband), but that's one of the advantages in aircraft use, you are using the engine in a relatively narrow rpm range.

Watch this carefully

http://motorcycleintelligence.com/MotorcyclePhotos/2-stroke-animation.gif
 

TFF

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The giant RC planes bury either can mufflers which are not peaky or tuned pipes in the fuselage. The small engines have them exposed. They can add 25% power. Elelctric has made the small ones not popular so you will not see many pictures of them anymore. The big ones, you will have to find construction pictures to find them.
 

akwrencher

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One thing I've picked up on is that the lower the rpm the longer the pipe, but most of these are for single or two cylinder engines. When I have a minute to carve out some shop time for myself, I want to figure out if, with four into one, it could be tuned to a lower range without a long pipe, using the pulse from a different cylinder. Will take some more info to get specific, I know. Have a welding project to finish and a couple cars to get running and then I can play a little, strip it down and measure port timing and area.
 

akwrencher

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20170416_105224.jpg20170416_105232.jpg20170416_105235.jpg20170416_105308.jpg20170416_105317.jpg

Here are some pics. No, this is not the motor I have, just one in the scrap yard that is partly torn down and is the same. Mine is still complete. You can see, maybe, that the exhaust tube coming down the shaft is tapered, like the beginning of a tuned pipe. It then goes down into the lower unit and exits out the prop hub. Also, for those not familiar with marine engines, these are wet exhausts, water is injected just below the block. A dry exhaust will be much different, due to different temps, no prop suction, etc. The middle of the V, (pic 2) the cover plate is removed and you can see the area where the exhaust ports collect. It looks like each bank stays seperate, then comes together at the bottom, which is on the right hand side.
 

Armilite

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This is just nonsense, not one claim is even close to being true, in fact they are ludicrous, yet you keep posting similar every time the subject comes up. Your information source is wrong, it's as simple as that.

http://motocrossactionmag.com/bike-tests/you-asked-for-it-motocross-actions-two-stroke-versus-four-stroke-shootout-yamaha-yz250-versus-yamaha-yz250f

Q: WHICH BIKE MAKES THE MOST HORSEPOWER?

A: No comparison. A Yamaha YZ250F four stroke produces approximately 36 horsepower at 11,300 rpm, while a YZ250 two-stroke makes on average 46 horsepower at 8500 rpm. That is a ten horsepower advantage at peak for the two-stroke (at much lower rpms).

Q: WHICH BIKE MAKES THE MOST TORQUE?

A: Pit pundits will always tell you that horsepower doesn’t matter as much as torque. They wax on about the torque advantage that a four-stroke engine has over a two-stroke. Guess what? A Yamaha YZ250F four-stroke makes 20.1 foot-pounds of torque. Are you ready? A YZ250 two-stroke pumps out 30.6 ft-pounds. For comparison purposes a 450 four-strokes produces approximately 34 foot-pounds.

Here's some 500cc class comparisons where the 2 strokes kill the 4 strokes, and at much lower rpm's ..
============================================================

Well Einstein, the Subject Here is Home Built Aircraft, and this thread is on 2 Strokes used for Airplanes and there's about 8 Billion People in this World now with over 750+ Manufactures of Airframes at one time and Not (1) Airframe Manufacturer has ever Adopted a large 1600CC 2 Stroke in Direct Drive turning low Rpm's like he was referring too! The only Plane that I even can think of that ever used a 2 Stroke in Direct Drive, but turning High Rpms and with a Small 2 Stroke was the Lazair Ultralight first with a pair of Small Chainsaw 5.5hp at I think 8000rpms, and those Engines were very marginal hp wise for that Aircraft, which were later upgraded to a pair of Rotax 185UL engines which again was only 9.4hp at 5000rpms, once again not at Low Rpms like he referred to, and they were breaking Cranks in Direct Drive also. Just like you haven't really seen any Auto/Truck/Boat or Motor Cycle Engine yet that has been really successful on Planes as much as they have tried for over 46+ years. Is there a few out recently today that look promising for some Types of Flying AirCraft, Yes, but they haven't been proven and used enough with many hours on them to tell yet. An AirPlane with Fixed Wings and with a Fixed motor is harder on a engine than one mounted on one of them Slow Parachute Type Planes, their lighter, and they Flex, and the Chute supports the Weigth better. That's WHY you don't see any of them Polini and other small Engines used on real Airplanes with Fixed Wings! Many People and Companies a lot smarter than you and me have spent Millions of dollars and thousands of man hours trying, and haven't been successful. So a private indivual doesn't stand much of a chance.

This 1600cc Engine would be to Heavy for Ultralight Airplanes, and probably for most small Light Sport Aircraft. Once you get into Airplanes that need 100+HP, 99.9999% of the People choose to go with a Certified Airplane Engine. Could a large 2 Stroke be Designed to compete against the 80Hp to 150hp engines, Yes, but the Best Design to be used in Continious Use on Airplanes for hours, is still going to be based off a Sled Engine. Ideally, you would want to design it for 100LL, use a low 9.5cr, a 1000cc engine could make 115hp at 6500rpms, a 1500cc could make 172hp at 6500rpms. Fuel Injection would be desirable for best GPH and Help Eliminate Carb Icing, and a Turbo option could make over 200+hp at 6500rpms.

Trying to compare a 2 stroke used on a lightweight Dirt Bike with a Gear Box and Gearing that can shift Gears to a 2 Stroke used in Direct Drive at low Rpms on an Airplane is just rediculious!
 
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