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CDMA
09-19-2001, 06:09 PM
Ok guys breathe deep and think of this with an open mind. This is just a silly thought I have been kicking around for a few years now and I wanted to toss it out into the open just cause the board seemed quiet. I have no intentions of doing anything like this I am just curious why it would or would not work. So no laughing.

Now I understand the inherent deficiencies in fuel consumption, EPA and so forth but in terms of a power density there is nothing, short of a gas turbine, like a 2 stroke engine.
So I was wondering why no company had come up with a large 2 stroke gas inboard. Even if not mass marketed and kit per say that would go around any regulatory restrictions.

My first thought was to do the following: Take a 350 chevy and flip it upside down. Remove all valvetrain, oil and camshaft hardware. Close all associated holes and related. Basically cover the valley with an intake manifold and seal it off completely. So now you have this rotating assembly of a 350 missing a lot of parts. You would need to figure a way to satisfactorily close the holes left by the intake and exhaust valves. Leaving only the spark plug in the combustion chamber. Now basically take the oil pan and cut a hole in it and putt carb on the now upside down v-8. Where I got stuck was getting the oil, air and fuel mixture through the cylinders. You would not have the luxury of a cast 2 stroke block and due to the constraints of the water jackets you could not cut large enough groves in the walls of the lower parts of the cylinders to allow for enough flow. So this is where this theory stopped and I was stumped.

Then a couple months ago I saw a Detroit 6-71 apart and realized it was possible to make a 2 stroke engine with a contained oiling system. So I went back to work. This one is a lot more simple and even feasible I think. I mean if you took a 350 and just played with the cam ( a la designed your own and had it ground) couldn’t you just make a 2 stroke 350. All that you would really need to mess with would be the cam and the spark if I am correct.

A lot more thought has gone into this but this is all I could muster to type.

So could it be done and could you make wild power from a 350 ci engine in doing so???

Chris

RedDog
09-19-2001, 06:21 PM
Sorry Chris, you are either genius (mad scientist) or the Nye brothers have gone to your head - Garage Built Turbines (http://www.gas-turbines.com/)

Maybe these thoughts will pass :rolleyes:

CDMA
09-19-2001, 06:43 PM
Those guys are the best. What they do is wild...gotta love it

Rootsy
09-19-2001, 07:35 PM
no reason it couldn't be done.. i wouldn't waste my time with carburators though... why not inject it? all you have to do is worry about getting air into it that way and not mixing gas and air! detroit diesels 8V series motors are the a perfect example...

Formula Jr
09-19-2001, 10:52 PM
Can't ya just yank a motor out of an RX-7 Mazda? Seriously with the strokes involved with regular four stroke engines, I don't think there would be much of a benefit. Two strokes have much less travel so you can get the RPMs up. Two strokes also depend so much on savaging from the exhaust system that you would need big diameter tubeing to get it right. But thats the nature of immersion in a subject - ya get to let your mind wander. We're all proud of ya Chris. Keep up the questions.

Moody Blu'
09-20-2001, 12:04 AM
two strokes is something I know alot about.

first you would need a carbureator with a reed assembly to keep the acceleration crisp and not boggy
You could do it, With a completely redesigned block.
you would need a 8 cylinder block with ports at the bottom of the block that would suck gas/oil mixture up to the combustion chamber and then fire it out the exhaust.The pistons would have to be designed in order for the suction to occur properly.
the head could be made out of a slab of metal with holes for the sparkplugs and coolant ports. and to make the power where you want it you would need two BIg ass pipes(coneshaped and about 3-5ft long) for each side.
It would cost WAY to much money.And the EPA would go ape s#@T.

Arent those mercury outboard 300 hp engines 2 stroke v-8s?

MattM
09-20-2001, 09:46 AM
I have often thought about this the other way around. I have a real nice tricked out '69 Datsun 510 somewhere in a back corner of my shop, it handles great, but is no longer fun to drive because it's slow compared to the Corvettes and Porsches I have had since I built it. It weighs 1800 lb. What would I need to do to adapt a Johnson or Evenrude 2 stoke V8 powerhead to it? Could I cool it w/ a radiator, Can I run the crank parallel to the ground?

BigGrizzly
09-20-2001, 10:44 AM
The two stroke has been far surpassed by the 4 stroke tech. Years ago Yamaha had the TZ750 factory water cooled race bike , it was the bench mark. Now the 600cc bikes run away from them with ease. The weed wackers are small and light, Well boys and girls Honda has a 4-stroke that puts them to shame, and it will run in any position- like upside down.
The PWC market also has gone that way, because of noise, power and polution. The out board market also is going that way.
If you want not to use a 4-stroke than Deisel is the only way too go. One one more factor Two strokes wear out faster due to the cylinder design.

Randy

Moody Blu'
09-20-2001, 10:53 AM
Right on grizzly!
I forgot to mention that(about the wearing of the rings)
that would suck changine the rings on a 8 cyl 2 stroke.

PaulO
09-20-2001, 10:59 AM
Firt of all, analyze what is happening in the two strokes of a 2 stroke as opposed to the four strokes of a 4 stroke and you will see why it cannot work without ports cut into the cylinder walls and a pressurized crankcase (except maybe in a low rpm diesel config.). We all know the four seperate strokes of a 4-stroke; intake, compression, combustion, exhuast. Now, on a 2-stroke you need to combine those same 4 functions into 2 strokes. This is how it is done:

Piston moves downward on the combustion stroke both exhaust and intake ports are covered by the piston.

Exhuast port is uncovered as the piston gets lower in the cylinder allow exhaust gas to escape sometimes aided by exhuast scavening. At the same time the movement of the piston into the crankcase creates pressure in the crankcas sealing off the one-way reed valves leading from the intake manifold/carb stopping the gas from escaping backward into the intake and building further pressure in the crankcase.

The piston moves further down in the bore and now unovers the intake port. The pressurized fuel/air/oil mixture in the crankcase flood into the cylinder as it starts it upward travel toward spark and compression.

Now the tough part. properly balancing the incoming pressurized charge so that it fills the cylinder without escaping into the open exhaust port. This is where emissions go bad. Without perfect balance, some of the unburned intake escaped out the exhaust in an effort to pack the cylinder. As you can imagine, these engines are very rpm sensitive. They run efficiently in a small rpm range due to proper intake and exhaust tuning.

Now, if you converted a 4-stroke to a 2-stroke, how would you add the ports in the cylinder? How would you pressurize the intake charge so that it can fill the cylinder without the benefit of an intake stroke? There are other ways than the most common I described above but, they all suffer other complexities.
PaulO

PaulO
09-20-2001, 11:08 AM
Oops, almost forgot, due to the exhaust/intake tuning requirements and the relatively small rpm range where these things are efficient, tuning almost always goes to the HP rather than the torque side. Consequently 2-strokes are usually lacking torque which is where they fall flat on motorcycles and boats. On 2-stroke outboards there is a common practice of using chopper props to allow low rpm slippage which in turn allows the engine to reach the higher rpm range where it begins to make serious HP.
PaulO

CDMA
09-20-2001, 11:11 AM
I love it. This is such a great education...Thanks guys.

I was not advocating or saying this would work in anyway and I know it is a silly idea I just wanted to know why it wouldn't work and I think I got it now. So the next one...what makes a 427 ford a "side oiler" :confused: ...every boady has to learn sometime...

Chris
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