Turbocharging carbureted petrol 2 stroke engines

In summary, the conversation discusses the possibility of turbocharging a carbureted 2 stroke petrol engine to increase its horsepower. The challenges of oil and fuel management, as well as the potential for back pressure and efficiency loss, are mentioned. The idea of starting with a 4 stroke engine and converting it to 2 stroke is also suggested. The conversation ends with the suggestion that extensive testing and research will be necessary to successfully implement this modification.
  • #71
Luth said:
50cc 2 stroke do a complete cycle anytime so could be correct match a turbo used in a 100cc 4 stroke?
Noboby know this? 😭
 
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  • #72
Luth said:
50cc 2 stroke do a complete cycle anytime so could be correct match a turbo used in a 100cc 4 stroke?
Yes, but "could be" are the appropriate keywords.
 
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  • #73
Luth said:
50cc 2 stroke do a complete cycle anytime so could be correct match a turbo used in a 100cc 4 stroke?
There are too many words missing. I could not understand the question.
 
  • #74
bluechipx said:
FWIW, I bought a Haltech electronic fuel injection system for my Mercury outboard. I had the dealer come over and he had me bring it up to various rpm's under full load on my dyno while he monitored his instruments and set up the fuel curve. $1000 system (still have it, anybody interested?) With equal boost as carbs you could give it any fuel mixture you wanted but it never worked as well as Mikuni draw through carbs did for some reason. Go figure. Maybe I just got lucky on my first attempt with the draw through system because nothing I changed afterwards did anything but decrease performance, sometimes by a lot.
bluechipx, what Haltech system did you try? After 40 plus years of having a hobby of trying to prove that 2cycle engines love boost, and can reach unreal HP numbers, I have arrived at the fact, that to reach the highest horsepower number, whether Turbo, Supercharged, or Nitrous, EFI is a must!

My choice of poison has been Kawasaki Triple engines 750cc. I started with draw-thru carb turbo in 1973 and followed into nitrous in 75. Still have everything I've tried and still build nitrous engines for a friends drag bike.

We are spraying , folks that make our nitrous system claim, is the equivalent to adding 285 HP to the engine! With the only issue being we have reached the mechanical limit of the transmission.

Sorry, back the the question, what did the Haltech run? I have been in contact with them and didn't find them too reassuring that my investment would be supported. I have already built mechanical fuel injection for these engines, but realizing that the most important aspect of fuel delivery to a 2cycle, is the understanding of its cyclic fuel curve, EFI would be the ultimate.

This site is an answered prayer for a very old, retired, 37yr Fireman, 35yr machine shop welder and guy who always hated to be told something couldn't be done.

Thanks
Cope
 
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  • #75
I'll find the Haltech in a day or so and give you the model, I bought it from Tom Earhart out of Gun Lake MI. He would be the guy for questions about it. What were you running the 750cc triple in? The 700cc snowmobile I have with a turbo was in a multi-state grass drag and was running the unlimited cc open fuel class. He made it to the final race with one other competitor. Up until this last race he used a hob switch to turn the nitrous off at 15 lbs of boost, just for a little help at the starting line. Then he would run 35 lbs of boost and at that boost level the crankshaft was only good for 2-3 passes. For a important final race for 1st place, a decision was made to disconnect the hob switch and run the nitrous for the full pass. Unfortunetly it was a bad decision, he burned it down at half track. I have never run it past 25 lbs of boost which the original owner said would good for the long run, never hurting it at that level.
 
  • #76
bluechipx said:
I'll find the Haltech in a day or so and give you the model, I bought it from Tom Earhart out of Gun Lake MI. He would be the guy for questions about it. What were you running the 750cc triple in? The 700cc snowmobile I have with a turbo was in a multi-state grass drag and was running the unlimited cc open fuel class. He made it to the final race with one other competitor. Up until this last race he used a hob switch to turn the nitrous off at 15 lbs of boost, just for a little help at the starting line. Then he would run 35 lbs of boost and at that boost level the crankshaft was only good for 2-3 passes. For a important final race for 1st place, a decision was made to disconnect the hob switch and run the nitrous for the full pass. Unfortunetly it was a bad decision, he burned it down at half track. I have never run it past 25 lbs of boost which the original owner said would good for the long run, never hurting it at that level.
The mechanical injected engines were run in 3/4 midgets, until they cut us back to 600cc, at which time I learned the 42mm throttle bodies I built still worked on the reduced sized engine. It only took one more season and the UMRA completely outlawed even the560cc engine.

The 750 made 168HP at 9,000 and the 560 made 144HP. As for the nitrous engines, they have been for drag race motorcycle 8.40s@ 162mph with a robust 225lb rider LOL For your sled, not knowing what kind of nitrous system he was running, I wouldn't think he would have used that large of jets for take off, and if that's true, 99% of the time a nitrous meltdown is caused by fuel shortage, pressure too low, lines too small (usually black plastic lines fail).

We use Speedtech Nitrous, car size nozzles and lines. they are the best, and more than helpful in anyway you need! I like to use wet style system (fuel supply dedicated for nitrous sys.) Dry systems have too much complication and avenues for problems. AS far as issues, we run more nitrous on a 2 stroke than anyone iv'e heard of. Full kit from starting line to finish, a quarter mile at a time. 2 1/2 lb. bottle per pass. No crank (welded pins and cryo-treated), piston or cyl. head problems. Average 5 runs a day, tear down just for a look, once every couple of months. The turbo bike, was always street tested and I have a 4gen. build almost ready, need to finish intake.

For those who care, figured out from the start in the 70s, no Physics, formulas or( the one I like) HE said it won't work! Chambers are a waste of time with a turbo. Keep the exhaust as short as posable, the closer to the exhaust port the better, and don't make the head pipes too big. Heat, velocity and pressure in the turbine housing of the turbo, will do the same job! For some other time, I'll tell you about a 750 with a supercharger on it. Have ridden the bike and even with a much too small carb, it was impressive. Another reason I want to get an EFI system found.

I started this life long love of 2 strokes in 1969 when I started out working on Mercury Marine engines and attended their schools at the factory in Fondulac.

Thanks for the time
Cope
 
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  • #77
bluechipx said:
I'll find the Haltech in a day or so and give you the model, I bought it from Tom Earhart out of Gun Lake MI. He would be the guy for questions about it. What were you running the 750cc triple in? The 700cc snowmobile I have with a turbo was in a multi-state grass drag and was running the unlimited cc open fuel class. He made it to the final race with one other competitor. Up until this last race he used a hob switch to turn the nitrous off at 15 lbs of boost, just for a little help at the starting line. Then he would run 35 lbs of boost and at that boost level the crankshaft was only good for 2-3 passes. For a important final race for 1st place, a decision was made to disconnect the hob switch and run the nitrous for the full pass. Unfortunetly it was a bad decision, he burned it down at half track. I have never run it past 25 lbs of boost which the original owner said would good for the long run, never hurting it at that level.
Hi Bluechipx, Came across you in two turbo posts and enjoyed your laid back and down to Earth explanations relating to how it was possible to turbo a 2 stroke. I wonder if you read this if you could contact me on the forum or via email ([personal e-mail address redacted by the Mentors]) It is in relation to turbocharging. Nothing ominous just a simple question on if one is using expansion chambers how are they placed into/at the impeller side of the Turbo?
 
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  • #78
Is there any way to add pictures? I currently have a turbo drag atv and several others have made successful turbo 2 stroke quads,

There is also one supercharged one that was never quite finished. If I can figure out how to post pics I’ll show y’all. There was quite a few questions but the basics of it is, adding pressure to the intake adds power, it’s simple don’t over think it about the exhaust being open, you still get the same rate of gain as you do with a 4 stroke.

A standard engine pulls vacuum on the intake side, by keeping the boost at 0 psi you get a gain because the engine isn’t working to suck the air in. At 15psi of boost you double your hp, at 30 you double it again, these same ideas work on a 2stroke
 
  • #79
When I told a motorcyle dealer that had a turbo on his bike, that I made OVER double hp at 14.7 psi boost he sneered and said I broke the laws of physics. I told him to visulize a 500 ci engine with a small lawn motor carb on it that would be running in a very high vacuum and making very little hp, now ad a turbo and crank the boost up to a whopping zero psi (but no vacuum) and watch the hp quadruple or more! I still don't think he got it for some reason due to the look on his face.
 
  • #80
Just signed up here after googling a little regarding my next project. And lots of guys here with practical experience, but a few logic flaws that made me sign up here. As an petrolhead, engineer and flawed two stroke motorbike racer(I was a coward in the corners) I do have the practical experience with tuning high performance two strokes and I understand the physics behind it.
Some here talk about back pressure and how an engine needs it to work. That is simply not true and are conclusion based on observations you do not understand.

An engine thrives when it has a low back pressure that helps extract the exhaust. An high back pressure will restrict engine power.

What your experiencing when you remove the exhaust off an 4stroke is a loss of bottom end power because of increased back pressure. An exhaust system Transports pressure and sound pullses that translates into a low pressure on the exhaustvalve. What this exhaust system is removed the atmospheric pressure will act on the exhaust valve creating a backpresure. When you move on to 2strokes understanding how sound and pressure works with the dynamics become even more essential. How do you guys think honda got 200hp from its NSR500 20+ years ago? The design is to my knowledge still an secret to this day.

An blower on a two stroke would work just as well as an turbo since there is no extra backpressure needed, but efficiency could become lower but with and wider powerband. Maybe a blower setup would produce more power at an better efficiency because you could throw the reedcage away and get rid of that resistance.

For the exhaust I would just throw the original expansion chambers and fit larger ones. The exhaust volume would be larger so I would think a that you should design the chambers according to cylindervolume*atmospheres. So if running 3 atmospheres of boost on a 50cc you should use chambers from a 150cc to obtain max results.
How much boost you could run would simply be limited by the pressure spike from the reflecting wave.
 
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  • #81
Some bloke trying to get a two-stroke to run on renosance alone without valves.

This guy prove parts of my claims. He has understood how a two stroke works.

Sadly he later looses it because of lack of theoretical understanding of engines.


The first thing he do make perfect sense. He gets the engine to run without an valve removing the losses there is in the valves.
For he's brute force concept it will work, but he is now fighting against the pressures instead of making them work with him ending up using a lot of power to run a blower who's fighting pressure waves.

https://www.snowmobile.com/blog/wp-...ris-two-stroke-turbo-patent-US20200182139.pdf

Looking at this patent from Polaris indicate that they use some different dimensioning of pipes that what is normal on naturally aspirated engines like myself have thought, but this could be purposely misleading to prevent copies.
 
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  • #82
With a two stroke engine the pressure in the pipe determines how fast the pressure wave travels up and down the length of the tuned chamber forcing the blow by back into the chamber n/a it effectively super charges itself. This can be tuned with the length of pipe. Longer pipe returns later, power at higher rpm, shorter pipe the opposite. The added psi of turbo charging will make this pressure wave travel faster. possibly so fast that the power band is moved out of the engines operating rpm. So I think a much longer chamber in the pipe would be needed to make the engine still have the two stroke power band we all know and love.
 
  • #83
Also the power band would change rpms as boost psi ramps up. Possibly if you could slowly raise the boost psi you could create a very wide progressive power band.
 
  • #84
Luth said:
Yes it's what I mean. The mistery is that thing seems work! But if we look the 2 stroke working process seems impossible. The return wave in the exhaust can put back the fresh charge expelled from the cylinder but if this fresh charge is boosted also how can it work? The gif picture is exactly the same engine principle of what I said. You can see carb Reeds and the ports open at the same time. Imagine to put a turbo at the outlet of the pipe.

Anyone can explain how a turbo can work on this?
View attachment 269184
Because the turbine side also increases back pressure equally. You guys seem to forget that part of the equation. If you use a turbo setup where the exhaust pressure can be regulated to not exceed boost pressure by too much you should be able to contain a bigger and denser mixture. Another thing is that an intercooler in this case will likely massively increase the performance too. Since a cooler charge is a denser charge. Means more mass at the same pressure. Which also means more power.
 
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  • #85
bluechipx said:
Here's a shot of the assembled Merc with the Aerodyne turbo.View attachment 269366

Man, I NEED to do this with an inline 6. If you still look at these forums please get back with me.
 
  • #86
Cope said:
The mechanical injected engines were run in 3/4 midgets, until they cut us back to 600cc, at which time I learned the 42mm throttle bodies I built still worked on the reduced sized engine. It only took one more season and the UMRA completely outlawed even the560cc engine.

The 750 made 168HP at 9,000 and the 560 made 144HP. As for the nitrous engines, they have been for drag race motorcycle 8.40s@ 162mph with a robust 225lb rider LOL For your sled, not knowing what kind of nitrous system he was running, I wouldn't think he would have used that large of jets for take off, and if that's true, 99% of the time a nitrous meltdown is caused by fuel shortage, pressure too low, lines too small (usually black plastic lines fail).

We use Speedtech Nitrous, car size nozzles and lines. they are the best, and more than helpful in anyway you need! I like to use wet style system (fuel supply dedicated for nitrous sys.) Dry systems have too much complication and avenues for problems. AS far as issues, we run more nitrous on a 2 stroke than anyone iv'e heard of. Full kit from starting line to finish, a quarter mile at a time. 2 1/2 lb. bottle per pass. No crank (welded pins and cryo-treated), piston or cyl. head problems. Average 5 runs a day, tear down just for a look, once every couple of months. The turbo bike, was always street tested and I have a 4gen. build almost ready, need to finish intake.

For those who care, figured out from the start in the 70s, no Physics, formulas or( the one I like) HE said it won't work! Chambers are a waste of time with a turbo. Keep the exhaust as short as posable, the closer to the exhaust port the better, and don't make the head pipes too big. Heat, velocity and pressure in the turbine housing of the turbo, will do the same job! For some other time, I'll tell you about a 750 with a supercharger on it. Have ridden the bike and even with a much too small carb, it was impressive. Another reason I want to get an EFI system found.

I started this life long love of 2 strokes in 1969 when I started out working on Mercury Marine engines and attended their schools at the factory in Fondulac.

Thanks for the time
Cope

Oh man, another great person to talk to about forced induction 2 smokes. This is an amazing thread, hope you guys can get back to me about the inline 6's.
 
  • #87
CLatch said:
Oh man, another great person to talk to about forced induction 2 smokes. This is an amazing thread, hope you guys can get back to me about the inline 6's.
What was the advertised HP of your inline six cyl?
 
  • #88
bluechipx said:
What was the advertised HP of your inline six cyl?
I've got the 115hp mid 70s mercs
 
  • #89
Not the perfect engine for adding HP. The long somewhat frail crankshaft I feel was at the edge in stock form. Either a V-4 or V-6 is a much stronger unit. The small inline four cylinder Merc thast I used had the front half of the motor (crankcase) that supported the crank and took a lot of thrust from the firing cylinders and barely weighed a pound! I happened to have a solid billet block of 7075 aluminum that was just the size to make a real strong crankcase out of. Also the turbo was hard on reeds and and in stock form you had to almost completely tear the engine apart to get at thev reeds. My new crankcase had a much smaller internal volume and used pyramid style reeds that are almost external and easily changed.
 

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  • #90
bluechipx said:
Not the perfect engine for adding HP. The long somewhat frail crankshaft I feel was at the edge in stock form. Either a V-4 or V-6 is a much stronger unit. The small inline four cylinder Merc thast I used had the front half of the motor (crankcase) that supported the crank and took a lot of thrust from the firing cylinders and barely weighed a pound! I happened to have a solid billet block of 7075 aluminum that was just the size to make a real strong crankcase out of. Also the turbo was hard on reeds and and in stock form you had to almost completely tear the engine apart to get at thev reeds. My new crankcase had a much smaller internal volume and used pyramid style reeds that are almost external and easily changed.
Was that done with a cnc? If so I have access to materials and the machines, and I can get one cranked out probably pretty easy. Would you happen to still have the files on it if it was cnc?
 
  • #91
I'm an old school machinist, sine plates, rotary tables and such. When I was buying my first Hurco machining center when the owner of the shop I was dealing with stepped away, I asked the twenty some year old operator how difficult it was to learn how to operate it. He said he could teach a monkey to do it in a half hour which gave me confidence. Six months later I was still struggling nand could only do the basics that could be done from the machines console. When it gets into 3-D I'm lost. My younger brother uses one of the mastercams from a computor and sends it to the machine. I did take an old crankcase and cut it across the area where the connecting rod travels and duplicated the shape on a piece of graphite and EDM'ed the pockets (which aren't half rounds , but a somewhat unique shape). One day last fall I wanted to try out a EGT gauge when it was in the thirties and snowed the next day. I took it kinda easy, probably around 80 mph and had the strange feeling the hydro was getting a little high in the front so I didn't look at my gauge and kept my eyes on the river. The trim adjustment jammed into a position that caused way to much bow lift. A professional racer friend saw the picture and said 1/4" more bow lift and it surely would have blown over. It's fixed now and it should be perfect in the spring when I run it again.
 

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  • #92
bluechipx said:
I'm an old school machinist, sine plates, rotary tables and such. When I was buying my first Hurco machining center when the owner of the shop I was dealing with stepped away, I asked the twenty some year old operator how difficult it was to learn how to operate it. He said he could teach a monkey to do it in a half hour which gave me confidence. Six months later I was still struggling nand could only do the basics that could be done from the machines console. When it gets into 3-D I'm lost. My younger brother uses one of the mastercams from a computor and sends it to the machine. I did take an old crankcase and cut it across the area where the connecting rod travels and duplicated the shape on a piece of graphite and EDM'ed the pockets (which aren't half rounds , but a somewhat unique shape). One day last fall I wanted to try out a EGT gauge when it was in the thirties and snowed the next day. I took it kinda easy, probably around 80 mph and had the strange feeling the hydro was getting a little high in the front so I didn't look at my gauge and kept my eyes on the river. The trim adjustment jammed into a position that caused way to much bow lift. A professional racer friend saw the picture and said 1/4" more bow lift and it surely would have blown over. It's fixed now and it should be perfect in the spring when I run it again.
Well I'm a welder/fabricator by trade, not anywhere close to a machinist, only thing I can operate like that is a drill press lol. I was asking so I could possibly have the engineering guys at work do their magic and recreate that idea in 6 cyl form, because I know for a fact that reeds won't survive boost, and they're INSIDE the crack case so it makes it that much harder. I really do like the idea of easier access to Reeds and a different type being that there's only 1 oem style aftermarket Reed option for the towers, and it's Boyosen. And yes, looking at that picture looks like it wasnt far off from tipping! I bet it sounds amazing tho! I do however have a question about cooling.
Did you have to modify the factory cooling on the block at all? And how about the lower unit?
 
  • #93
No cooling mods at all. In fact the one to one gear case off a 45SS johnson race engine (stronger than the "D" Merc) had such a big water pump in it the engine wouldn't warm up so I had to re-route some of the water back to the river to get sensible engine temp. I really hope you aren't planning on using the stock gear ratio fishing lower unit gear box. Instead use one of the speedmaster series units. When a new guy would get a hydro, on a budget, and try high pitch props on the fishing unit, a fifty hp Merc (44 cu in) would barely hit fifty. A simple change to a "quicky" or one to one racing style lower unit would jump the speed easily to 76-78 on the first try.
 
  • #94
BTW, in order to match the block to the new crankcase and wind up with the crank bore being round and sized right I did the bore on a DeVlieg jig mill. Yours being 50% longer will be a little tougher. I could be wrong but I think when the engineering guys see what you are asking they won't be quick to agree, it's quite a job from huge block of aluminum into finish product. Let me know how it goes when you run it past them.
 
  • #95
bluechipx said:
BTW, in order to match the block to the new crankcase and wind up with the crank bore being round and sized right I did the bore on a DeVlieg jig mill. Yours being 50% longer will be a little tougher. I could be wrong but I think when the engineering guys see what you are asking they won't be quick to agree, it's quite a job from huge block of aluminum into finish product. Let me know how it goes when you run it past them.
I'm aware about the lower, was just curious of what kind you had in your pictures. I might use it for initial testing purposes but not permanently. Im not really familiar with outboard racing or racing products for outboards in general, this project will just be a hobby deal for me.
And Hopefully the engineers and machinists won't turn it down, I mean I do work for one of the top automotive blower companies in the US, and we have experimented with outboard stuff a while back but ended up sticking to inboard blowers due to market not being there. I doubt it was anything this old, but I also doubt the guys will be scared to do it.
Also, what size carburetors did you use? Going to try to get an idea of the amount venturi I need along with the jet sizes you used. I imagine a good starting point would be slightly bigger carb than you used at 3 total?
 
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