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#1
Old 02-25-2009, 09:27 PM
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Can you turbocharge a two-stroke gasoline engine?

I sometimes sit and think about things I could turbocharge. Sportbike? Nah, I'd end up getting in trouble. Dirt bike? Nah, the thing is quite the handful already. But really, my dirt bike has a two-stroke engine. Is it possible to put a turbocharger on a two-stroke? Thinking about it, the intake and exhaust ports are exposed at the same time so it seems likely any extra air/fuel blown into the cylinder would just blow out the exhaust pipe decreasing efficiency. And it would likely throw the exhaust tuning off too, though that wouldn't be a problem for a company with sufficient resources. So what's the story on turbocharged two-strokes?
#2
Old 02-25-2009, 09:56 PM
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If you Google a bit you can find some one-off examples of folks fitting turbos to two-strokes. Google video has a Vespa with a turbo. You're correct about the inherent problems of fitting a turbo to a two-stroke, but it appears to be *possible*.
#3
Old 02-25-2009, 10:17 PM
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Two stroke engines are more or less supercharged already. In motorcycle engines, the air/fuel mixture passes through the bottom end where it is pressurized to a few PSI when the piston drops. Smoother flywheels, solid or filled crankpins, tightly fitting crankcases, and/or faster moving reed valves all help increase the bottom end compression.

You might be able to increase power by adding a turbocharger, but I'd be careful not to add too much. The crankshaft seals are usually a press fit from the outside and could blow out. Cooling and detonation are also issues, more so than for four strokes. If heat isn't well managed, the engine may tend to burn holes in pistons.

Last edited by cornflakes; 02-25-2009 at 10:17 PM.
#4
Old 02-25-2009, 10:49 PM
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Large two stroke engines are normally supercharged rather than turbocharged.

A mechanically asperated engine does not normally need to use the piston to act as a air pump. So crank case seals are not a problem. The problem is in starting a turbo charged two cycle.

Adding a turbo or super charger to any two cycle engine is going to increase power at a cost of effency.
#5
Old 02-26-2009, 12:36 AM
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Every two stroke needs an induction pump of some sort. Simple ones use the crankcase, bigger and more efficient ones use roots blowers (blowers from detroit diesel twostrokes were the origional source for supercharging hotrods). And a few really big engines (trains and ship Diesels AFAIK have used turbocharers. The big problem is that you need somewhay to start it up and get the turbo working. Compressed air, and electric pre-spin motors are two ways of doing this.

To make forced induction work well in a two-stroke, you really need more complex exhaust valving than just the typical port uncovered by the piston. Reason being that such a port is still open when the bypass (or whatever the intake uses) port closes, so your intake pressure is only as high as the exhaust backpressure. (this is why lowering exhaust backpressure in normally aspirated two strokes normally reduces power) Two strokes with forced induction either use poppet exhaust valves in the head (which give good scavaging) or a rotary or other valve downstream of a typical exhaust port.

Another problem with turbocharging a simple two stroke is that there is no supply of pressuized oil waiting to be tapped.

The exhaust problem is turned to an advantage by a resonant exhaust system (expansion chamber) This is a form of forced induction and augmented scavaging based on accustic principals....works VERY well over narrowish rpm ranges.

Last edited by Kevbo; 02-26-2009 at 12:38 AM.
#6
Old 02-26-2009, 01:22 PM
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This was very informative. Before making this thread, I searched the web for "turbocharged two-stroke gasoline" and similar strings but only turned up pages for two-stroke diesels. Afterwards, I got the idea to search for "turbocharged banshees" and found companies that offered kits. So what I'm gathering is it's possible, but more difficult than with a four-stroke. If I wanted to do all the work myself, I'd be better off doing it on my sportbike or car.
#7
Old 02-26-2009, 03:02 PM
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Orbital have a system of seperate inlet and outlet valves, meaing that you don't get the problem of having inlet and outlet open at the same time.

The trick on this engine is to have a pre-fuel air mixture/compressors, rather like a supercharger, some designs use a slave piston in its own cyclinder to achieve premix pressures - this is driven by the crank but no combustion takes place in it.

The premix is direct injected, but only once the outlet port is closed.This means that the piston is already on the up stroke so it has to be injected under pressure to overcome this.

These are very much more efficient engines, and produce very much less pollution, the crank does not sit in the fuel/lub oil mix either.

In many ways the orbital 2 stroke removes all the disadvantages of the 2 stroke, but delivers more power by weight than a 4 stroke.

Used on scooters made by Aprilia for the moment, this engine can scale up to over a litre and may find its way on to superbikes, its cleaner than 4 stroke, but it is not a simple as the conventional 2 stroke, this is a sort of halfway house between 2 and 4 stroke in terms of oil and injection systems.

http://en.wikipedia.org/wiki/Orbital...ration_Limited
#8
Old 02-26-2009, 06:18 PM
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Quote:
Originally Posted by Kevbo
And a few really big engines (trains and ship Diesels AFAIK have used turbocharers.
All the big, two stroke diesels I've worked with (all GM products in EMD locomotives) have used some form of forced induction. This is apparently a necessity for 'scavenging' the combustion chamber between the exhaust and intake parts of the combustion cycle. The pressurised intake air helps blow out any remaining exhaust gasses. Earlier models use Rootes blowers, which are mechanically driven (off the camshaft, I think), and so produce pressure in relation to engine speed. Later versions use turbo charging, for increased power output and efficiency. The turbo wouldn't produce enough air pressure for scavenging at lower engine speeds, so it is mechanically driven by some sort of an overriding clutch arrangement, up to the point where the exhaust gasses are sufficient, after which it free wheels. So the engine is mechanically supercharged up to a point, and turbo supercharged thereafter, which I thought was quite clever.

The large, four stoke diesels that seen have all been turbocharged (none of this tricky clutchy assistance business).
#9
Old 02-26-2009, 08:10 PM
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Originally Posted by chicken wire? View Post
All the big, two stroke diesels I've worked with (all GM products in EMD locomotives) have used some form of forced induction. This is apparently a necessity for 'scavenging' the combustion chamber between the exhaust and intake parts of the combustion cycle. The pressurised intake air helps blow out any remaining exhaust gasses. Earlier models use Rootes blowers, which are mechanically driven (off the camshaft, I think), and so produce pressure in relation to engine speed. Later versions use turbo charging, for increased power output and efficiency. The turbo wouldn't produce enough air pressure for scavenging at lower engine speeds, so it is mechanically driven by some sort of an overriding clutch arrangement, up to the point where the exhaust gasses are sufficient, after which it free wheels. So the engine is mechanically supercharged up to a point, and turbo supercharged thereafter, which I thought was quite clever.

The large, four stoke diesels that seen have all been turbocharged (none of this tricky clutchy assistance business).
That is interesting. Thanks. I knew of some ships that were turo charged and their sister ships were supercharged. The turbo charged ships were more problematic.

These were double acting direct drive crosshead engines.
#10
Old 02-27-2009, 04:58 PM
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I'm pretty sure the very largest piston engines are supercharged two stroke engines, such as in marine power. These have nonoscillating piston rods and crossheads, and the spaces above and below each piston are sealed. The crankcase is not part of the fuel cycle and has ordinary oil in it. These things are bigger than houses.
#11
Old 02-27-2009, 11:38 PM
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Originally Posted by Napier View Post
I'm pretty sure the very largest piston engines are supercharged two stroke engines, such as in marine power. These have nonoscillating piston rods and crossheads, and the spaces above and below each piston are sealed. The crankcase is not part of the fuel cycle and has ordinary oil in it. These things are bigger than houses.

They are both 2 and 4 stroke. Supercharged and turbo charged. direct drive two cycles with turbo are problematic. Now Diesel electric would be different.
#12
Old 02-28-2009, 09:48 AM
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I found this on the wed
http://bloggingwv.com/the-most-p...-in-the-world/
It is a 2 stroke and turbo charged direct drive. Although the drawing looks single acting.
#13
Old 01-09-2011, 11:52 PM
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Originally Posted by cornflakes View Post
Two stroke engines are more or less supercharged already. In motorcycle engines, the air/fuel mixture passes through the bottom end where it is pressurized to a few PSI when the piston drops. Smoother flywheels, solid or filled crankpins, tightly fitting crankcases, and/or faster moving reed valves all help increase the bottom end compression.

You might be able to increase power by adding a turbocharger, but I'd be careful not to add too much. The crankshaft seals are usually a press fit from the outside and could blow out. Cooling and detonation are also issues, more so than for four strokes. If heat isn't well managed, the engine may tend to burn holes in pistons.
You hit the nail on the head. The two major issues are the reed valves and loss of pressure thru the exhaust will the piston is at BDC. Reed valves will never be able to keep up with the pressures required for postive aspiration.. I've heard of it being done on snowmobiles and stuff, but I'm willing to bet they were 4 cycles. Diesles have managed to do it, but the use a poppet valve, which to me is not a true two cycle.

I do have a plan that can resolve these complications but I need some help in order to create a working prototype to be tested. My plan involves the same physics of a normal two cycle, but with a way increase compression without MOST of the pressure loss from the exhaust at BDC. If you know of anyone that might like to help, I would be most generous.
#14
Old 01-10-2011, 09:19 PM
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Originally Posted by chkneater View Post
Diesles have managed to do it, but the use a poppet valve, which to me is not a true two cycle.
.
Do not know how you can not call them 2 cycles. On ignition piston goes down Near BDC exhaust port comes open the intake valve comes open, piston reaches BDC. One stroke. Piston starts up exhaust port closes intake valve closes compression begins. Near TDC injection of fuel and as pistion gets to TDC ignition begins. Second stroke.
#15
Old 01-10-2011, 09:29 PM
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Quote:
Diesles have managed to do it, but the use a poppet valve, which to me is not a true two cycle.
the simple fact that they have one power stroke per crankshaft revolution defines them as two-stroke. it doesn't matter if they're blower-scavenged or not.

Quote:
I do have a plan that can resolve these complications but I need some help in order to create a working prototype to be tested. My plan involves the same physics of a normal two cycle, but with a way increase compression without MOST of the pressure loss from the exhaust at BDC. If you know of anyone that might like to help, I would be most generous.
we already do this with resonance-tuned exhaust pipes, like the one on my hydroplane here:

http://home.comcast.net/~jz78817/stuff/stinger.jpg

that little 11cc engine is rated at almost 5 hp with proper exhaust tuning.
#16
Old 01-11-2011, 10:50 PM
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I totally agree

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Originally Posted by Snnipe 70E View Post
Do not know how you can not call them 2 cycles. On ignition piston goes down Near BDC exhaust port comes open the intake valve comes open, piston reaches BDC. One stroke. Piston starts up exhaust port closes intake valve closes compression begins. Near TDC injection of fuel and as pistion gets to TDC ignition begins. Second stroke.
I totally understand that number of strokes per power cycle dictate that they are two cycles, however I guess nostalgically to me a two cycle should use the crankcase as the intake manifold. With port fuel injection, you could conceivably use an oil pump just like normal four cycles.

My point overrall was the efficiency and high rpm's gained from two cycles was due to not using poppet valves and using ports in the chamber.

But yes, you are right, I only meant that they weren't like the "traditional" two-cycles.
#17
Old 01-11-2011, 10:56 PM
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Originally Posted by jz78817 View Post
the simple fact that they have one power stroke per crankshaft revolution defines them as two-stroke. it doesn't matter if they're blower-scavenged or not.



we already do this with resonance-tuned exhaust pipes, like the one on my hydroplane here:

http://home.comcast.net/~jz78817/stuff/stinger.jpg

that little 11cc engine is rated at almost 5 hp with proper exhaust tuning.
I'm not entirely sure about how those work, but I would think that it would have a narrow power band and not as much torque as horsepower (ie. high acceleration instead of pulling power)

Correct me if I'm wrong. I think two cycles are the most efficient engines and really wanna know all about them.
#18
Old 01-11-2011, 10:58 PM
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Originally Posted by chkneater View Post
I totally understand that number of strokes per power cycle dictate that they are two cycles, however I guess nostalgically to me a two cycle should use the crankcase as the intake manifold. s.
I meant intake AND exhaust manifold.
#19
Old 01-11-2011, 11:19 PM
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Originally Posted by chkneater View Post
I'm not entirely sure about how those work, but I would think that it would have a narrow power band and not as much torque as horsepower (ie. high acceleration instead of pulling power)

Correct me if I'm wrong. I think two cycles are the most efficient engines and really wanna know all about them.
If you are talking about fuel efficiency, they aren't. If you are talking energy density (pounds per hp) they are pretty good.
#20
Old 01-12-2011, 12:29 AM
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Quote:
Originally Posted by chkneater View Post
I meant intake AND exhaust manifold.
You sure? I've disassembled several dirt bike and weed eater engines and I've never seen a two-stroke engine that used the crankcase in any way as an exhaust manifold. The crankcase causes secondary compression on the intake, but I see no reason to pass the exhaust through the crankcase, especially in the same chamber where the intake is.
#21
Old 01-12-2011, 09:50 AM
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I think two cycles are the most efficient engines
Nope, not by a long shot. I'm sure some of that is lack of investment in the technology compared to four-strokes, but as far as real efficiency goes, the big diesels in large ships have them beat handily. I'm talking about those gigantic diesels with cylinders you can climb into, and have a peak rated speed of 100 rpm.

small two strokes simply can't breathe well enough to make those kind of efficiency numbers. A four-stroke has ~180 of crankshaft revolution for intake, and another 180 to clear the cylinder of spent gases (exhaust.) A two stroke, depending on design, has maybe 45-90 of crankshaft revolution to do both at the same time. those little radio control nitro engines get around this by burning fuel with a lot of oxygen contained in it (via the nitromethane.)

Some of the newer developments in opposed-piston two-strokes look promising. I can't think of the name of that concept engine design that's being shown off right now, but they're making reasonable claims and have credible people involved. I'm not sure how they're going to deal with all that reciprocating mass, but we'll see.

Last edited by jz78817; 01-12-2011 at 09:51 AM. Reason: changed one "crankcase" to "crankshaft"
#22
Old 01-12-2011, 10:02 AM
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Two-strokers are better supercharged (vs turbo charged), because a two-stroke is free of valvetrain and will generally spin like the dickens, so it has a power curve that it top heavy. Supercharging is most effective at boosting low-end power, which is precisely where you'd want it in a two-stroker.

A four-stroker invariably moves power down in the power curve. Better breathing makes this happen. You get better efficiency and you give up screaming RPM and wicked throttle response that two-strokers enjoy.

In R/C engines, the two strokers light up so fast it is frightening, as they come to bat with few moving parts, and a nitromethane mix of anywhere from 10-40% (or more in some applications). The fuel is over 30 bucks per gallon.

Switching to four stroke engines has been tried, but nothing matches the throttle response of a 2-stroker.
#23
Old 01-12-2011, 12:28 PM
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Kind of off-topic, but could you put nitrous feed on it?
#24
Old 01-12-2011, 12:35 PM
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Sure can.
#25
Old 01-12-2011, 12:55 PM
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Quote:
Originally Posted by jz78817 View Post
Nope, not by a long shot. I'm sure some of that is lack of investment in the technology compared to four-strokes, but as far as real efficiency goes, the big diesels in large ships have them beat handily. I'm talking about those gigantic diesels with cylinders you can climb into, and have a peak rated speed of 100 rpm.
I think what you are referring to are 2 stroke engines, as are many (most?) diesel engines. In the case of low RPM engines, there is plenty of time to eliminate exhaust and compress fresh air and fuel intake within a single stroke. For high speed 2 stroke engines, this portion of the cycle is a compromise. But I repeat, fuel efficiency is only one measure of engine efficiency. Weight, cost, duty cycle, lifetime, and performance under specific conditions alter the specific definition of efficiency.

Last edited by TriPolar; 01-12-2011 at 12:55 PM.
#26
Old 01-12-2011, 12:59 PM
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But I repeat, fuel efficiency is only one measure of engine efficiency.
from a physics standpoint, it's the only one. small two-strokes consume more fuel for a given amount of power with all else held as equal as possible. you can take other characteristics such as power-to-weight ratio, mean time before overhaul, or whatever and try to call them "efficiency" but that's a colloquialism at best.

Last edited by jz78817; 01-12-2011 at 01:00 PM.
#27
Old 01-12-2011, 01:16 PM
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Originally Posted by snailboy View Post
You sure? I've disassembled several dirt bike and weed eater engines and I've never seen a two-stroke engine that used the crankcase in any way as an exhaust manifold. The crankcase causes secondary compression on the intake, but I see no reason to pass the exhaust through the crankcase, especially in the same chamber where the intake is.
No, I shouldve clarifiied better. What I meant is that the cylinder ports were responsible for the intake and exhaust, unlike the diesels that use a poppet for the exhaust. Having the exhaust port at the bottom of the cylinder is both its greatest asset and biggest problem, especially when it comes to positive aspiration.

What I originally meant was that the use of poppet valves makes it not a true two cycle in my opinion, regardless of how many power strokes per cycle.
#28
Old 01-12-2011, 01:21 PM
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Originally Posted by jz78817 View Post
Nope, not by a long shot. I'm sure some of that is lack of investment in the technology compared to four-strokes, but as far as real efficiency goes, the big diesels in large ships have them beat handily. I'm talking about those gigantic diesels with cylinders you can climb into, and have a peak rated speed of 100 rpm.

small two strokes simply can't breathe well enough to make those kind of efficiency numbers. A four-stroke has ~180 of crankshaft revolution for intake, and another 180 to clear the cylinder of spent gases (exhaust.) A two stroke, depending on design, has maybe 45-90 of crankshaft revolution to do both at the same time. those little radio control nitro engines get around this by burning fuel with a lot of oxygen contained in it (via the nitromethane.)

Some of the newer developments in opposed-piston two-strokes look promising. I can't think of the name of that concept engine design that's being shown off right now, but they're making reasonable claims and have credible people involved. I'm not sure how they're going to deal with all that reciprocating mass, but we'll see.
Those super huge diesels in ships, ARE two cycles. The largest engine in the world is a two cycle. I was just watching something about them on Discovery channel a couple days ago. Apparently some use a slave cylinder to charge the chambers.

And aspiration is definitely the problem with two strokes, that's why I want to find a way to charge them. I think I may have found a solution, but it's impossible to test with no funds, so I guess we'll never know.
#29
Old 01-12-2011, 01:25 PM
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Originally Posted by jz78817 View Post
from a physics standpoint, it's the only one. small two-strokes consume more fuel for a given amount of power with all else held as equal as possible. you can take other characteristics such as power-to-weight ratio, mean time before overhaul, or whatever and try to call them "efficiency" but that's a colloquialism at best.
but what causes them to lose efficiency? Is it the speed of the reciprocating parts? It just doesn't make sense that something with like, 5 moving parts would be less efficient than something with over two hundred? The only thing I can think is design of the exhaust ports and the reed valves.
#30
Old 01-12-2011, 03:59 PM
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Originally Posted by jz78817 View Post
from a physics standpoint, it's the only one. small two-strokes consume more fuel for a given amount of power with all else held as equal as possible. you can take other characteristics such as power-to-weight ratio, mean time before overhaul, or whatever and try to call them "efficiency" but that's a colloquialism at best.
Not a colloquialism. Those are engineering terms. And even in physics fuel efficiency is meaningless for a hypothetical engine. Once an engine is used to do actual work (which is what makes it an engine and not a theory) and the definition of efficiency varies. Real engines have produce heat and friction, and also require oxygen and (usually) lubrication, not just fuel.
#31
Old 01-12-2011, 04:01 PM
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Originally Posted by chkneater View Post
but what causes them to lose efficiency? Is it the speed of the reciprocating parts? It just doesn't make sense that something with like, 5 moving parts would be less efficient than something with over two hundred? The only thing I can think is design of the exhaust ports and the reed valves.
Fuel efficiency in engines is governed by the thermodynamic cycle. Very efficient engines often have more moving parts in order to more closely conform to an ideal cycle.

Would love to go in depth on this, but the phone is ringing. Not the good phone either.
#32
Old 01-12-2011, 04:30 PM
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Originally Posted by chkneater View Post
but what causes them to lose efficiency? Is it the speed of the reciprocating parts? It just doesn't make sense that something with like, 5 moving parts would be less efficient than something with over two hundred? The only thing I can think is design of the exhaust ports and the reed valves.
Well, there is no great way to create the proper duration for intake and exhaust, because as the piston is coming up to compress the fuel air mix, it's also exhausting the latest exhaust.

That's kind of sloppy to say the least. Out the exhaust invariably goes some am't of fuel/air mix. On aggressive 2-stroke engines, the exhaust can even be dripping wet.

On a four stroke engine, the fuel/air mix is compressed with the combustion chamber sealed.

On the exhaust stroke of a 4-stroker, the intake is sealed and the exhaust is open, sometimes until just a moment after the piston reaches top dead center. Getting twin-cams takes this farther, because exhaust and intake timing are working on their own cam, so you can get aggressive on the intake stroke, but not have it create too long of a duration on the exhaust stroke (because too long of an exhaust duration can create a sucking action back from the exhaust).

These are just some of many examples that demonstrate how a 4-stroker gains in efficiency over a 2-stroker and how twin cams are better than single cams. You want a good fuel/air mix, you want good compression and timing, and you want to fully expel exhaust gases.

Last edited by Philster; 01-12-2011 at 04:34 PM.
#33
Old 01-12-2011, 10:12 PM
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Originally Posted by chkneater View Post
Those super huge diesels in ships, ARE two cycles. The largest engine in the world is a two cycle. I was just watching something about them on Discovery channel a couple days ago. Apparently some use a slave cylinder to charge the chambers.

And aspiration is definitely the problem with two strokes, that's why I want to find a way to charge them. I think I may have found a solution, but it's impossible to test with no funds, so I guess we'll never know.
Aspiration is a deffinate problem with a crankcase asperated engine. Two problems. The intake and exhaust port are both at the bottom of the cylinder the intake air has to blow the last of the exhaust gases out of the cylinder. With the ports at the bottom of the cylinder it isl harder to clear the whole cylinder. The second problem is the small volume and low pressure of the air coming from the crankcase.

Also another problem is with no oil in the crankcase the bearings have to be made of softer material. That means lower mean effective pressures.

I believe a lot of two cycle marine engines are uniflow design. With the intake valve at the top of the cylinder and the exhaust port at the bottom. The air enters the top of the cylinder and blows out the botttom, less eddy currents and a better purging of the cylinder. With a high boost pressure better cleaning and with a cam operated intake valve the intake valve closes after the exhaust valve.

A 2 cycle engine per stroke is not as efficient. On the power stroke the exhaust valve has to open sooner before the end of the power stroke while pressure is still elevated. On ported engines the exhaust valve closes after the intake port. That means lower initial cylinder pressures. But a 2 cycle engine has twice the power strokes for a give RPM. For the same engine power less weight.

Most diesels I have worked with stationary have been 4 cycle.


Do not know what I was thinking the intake is ported and the exhaust is valved. Sorry brain fart.

Last edited by Snnipe 70E; 01-12-2011 at 10:17 PM. Reason: Brain Fart
#34
Old 01-12-2011, 10:20 PM
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By the way

Use to be that the way the rings were checked on a marine engine was to crawl in the intake maifold. Use the jacking gear to roll the engine over until the rings are at the intake port.
#35
Old 01-12-2011, 11:08 PM
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Well since this thread was revived and has evolved into a general discussion about two-stroke engines, I have another question. Why aren't small diesels two-strokes? Gasoline two-strokes are less efficient because they can blow part of the intake charge straight out of the exhaust port, but with a diesel, it's just air blowing in. I would think a two-stroke diesel with forced induction would be just as efficient as a four-stroke diesel and could be much smaller, but obviously I'm missing something. What is it?
#36
Old 01-13-2011, 12:06 AM
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I have another question. Why aren't small diesels two-strokes?
GM/Detroit Diesel truck engines were two-strokes from the late '30s to about the mid-'90s. The 6-71 was probably the most popular version; the V6 and V8 versions were very common in city buses and fire trucks up until the late '80s or so. As I recall, even with DDEC electronic controls, they ran dirty and were deemed not worth trying to bring forward into compliance; and Detroit eventually discontinued them in favor of four-strokes.

plus, even by diesel standards they were horribly loud; they had the nickname "Screamin' Jimmy" for a reason.
#37
Old 01-13-2011, 12:12 AM
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here's a couple of examples:

Detroit 6V-53 (V6, 53 cu. in. per cylinder): http://youtube.com/watch?v=ZvJxeAqQcY0

6V-71: http://youtube.com/watch?v=Ao2nWOVAcsM#t=51s

6-71 (note the Roots blower on the side for scavenging) http://youtube.com/watch?v=mFEw6GTngyY

Last edited by jz78817; 01-13-2011 at 12:16 AM.
#38
Old 01-13-2011, 09:16 AM
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Quote:
Originally Posted by jz78817 View Post
GM/Detroit Diesel truck engines were two-strokes from the late '30s to about the mid-'90s. The 6-71 was probably the most popular version; the V6 and V8 versions were very common in city buses and fire trucks up until the late '80s or so. As I recall, even with DDEC electronic controls, they ran dirty and were deemed not worth trying to bring forward into compliance; and Detroit eventually discontinued them in favor of four-strokes.

plus, even by diesel standards they were horribly loud; they had the nickname "Screamin' Jimmy" for a reason.
The 71 series engine died because of noise polution. Sweet sounding engines but loud.
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