Have been thinking about this some time but not sure if it would work!! Say that you use a smbl chev and fabricate a new timing gear that will let the cam and distributor run at the same speed as the crank, that will mean that the intake will open on every downstroke and the exhaust on every upstroke. Then put a supercharger on top and it will force the gasmixture forward as a flushpump. The overlaps on the cam probably has to be altered and maybe the valve sizes has to be bigger. the sparks will come on every compressionstroke (twice its normal rate) Probably the valve springs will have some busy times so maybe harder springs! Any engine wizards out there please tell me its not possible or maybe possible!! Should sound nice anyway as a twostroke! Please dont laugh, i know its a crazy idea and that any normal v8 with a charger will put out more power (maybe)
There wouldn't be too many internal parts that could turn at a 2 cycle speed and hang together. Inertia of the rotating mass has got to be your enemy big time there.
A two stroke has the intake port higher than the exhuast port. this is how it gets compression. If these were even the mixture would not enter the combustion chamber. If the intake was open on the down stroke and exhaust on every up stroke there would be no compression.
Actually, Doc, you have it a little backwards... 2 strokes can attain rediculously high RPM's because they have no monkey business valve-train to worry about. Also, 2 strokes produce more power because there is a combustion cycle occouring every crankshaft rotation as compared to once every 2 rotations in a 4 stroke, but they produce less power per "combustion" because they are less efficent. They pass a tremendous ammount of un-burnt fuel out the tailpipe, and they consume oil due to the [required] ring design. Here's a web site that will give you animated gif's of all the known engine types in action. http://www.keveney.com/Engines.html As to the original question, no, it's not possible. 2 strokes work off principals of revurb and enertia to fill and empty the cylinders... Actually, it would be possible with the addition of a supercharger [old detroit diesels], but it would completely lack power and would run like crap.
Well thank you, learn something every day. I understood the head and valvetrain differences but thought someone who actualy knew what they were talking about. I just thought that if you could overcome that the rotating mass would be too heavy for the rpm it would run at? Or am I still missing something here.
Hmmmm... kind of. Reverb can be achieved with an expansion exhaust system of some kind. Tuning a stock two stroke is a bit of a black art though - trying to convert a V8 to even run as one would realistically be next to impossible.
Well Detroit Deisels are two stroke engines as ar most Electromotive (GE train engines) and the giant container ship engines. Some of which run at around 120 rpm wide open. You would need a cam ground for the application. Detroits blow the air in through piston ports in the lower part of the cylinder. All the valves are exhaust. Timed direct injection or you would be blowing a lot of fuel out the exhaust. Thats what I think.
this is just my opinion.. wouldnt there be just too much shit to change to even make it worth it? it was designed as a 4 stoke engine..all the way to the core..how would you reverse engineer all that back out of the platform the engine was based upon? and than re-engineer the 2 stoke set up back into it..and really what would you gain? if anything? Or would this be like the GM engines that were made into diesels? were they 2 stoke diesels? mmm? alot of questions rolling around in my head..very interesting question.. disclamer..Not responsible for any incorrect spelling.. this is a hot rod forum not a spelling bee.
Detroit Diesels are two strokes. They have valves and also made V8s. I have never looked at one apart though to see how they work. Could probably find a cut a way here on the net.
Since a 2 stroke produces less power per combustion, it puts less stress on the rods. Also, since 99% of the 2 strokes that have ever been produced are under 200 cc's, they generally have short strokes and looooong connecting rods. I'm sure you have heard of the long rod -vs- short rod arguement in a gas [sbc] engine. Well, in a 2 stroke, the long rod scenario makes a world of difference. The piston "dwells" @ TDC and BDC longer to extract more power, and to allow more gasses to move thru the ports while it's at BDC. What's more, a long rod produces less tortional stress and "sheer" at the big end, allowing it to live at RPM's that would kill a short rod 4 stroke. There are limitations to everything. The bigger the engine, the more rotating mass, the less RPM it will take before something breaks. So in a sense, your right... If a small block chevy were converted to a 2 stroke, it could probably take an extra 1000 rpm's before it came apart over the 4 stroke version. It remains popular in chain saws and weed-wackers because of it's simplicity and lack of valve-train. In many ways, it is superior to a 4 stroke, but they are pollution devils! That's why there are no more 2 stroke diesels, and why boat motors are beginning to come out in 4 stroke models.
Detroits were "compound 2 strokes". They had exhaust valves in the heads and the intakes were conventional "ports" in the bottom of the cylinders.
Keep in mind guys, Diesels are entirely different animals. They may look the same with pistons, valves, and connecting rods,,, but they work on entirely different principals of combustion and thermodynamics.
Yes, but if you want to do a two stroke, why slow it down with a draggy valvetrain? Reed valves on the inlet side and an expansion exhaust would be the way - if not the most efficient, then at least acheivable. Direct timed injection would be perfect.
The only way to do it retaining an intake and exhaust valve in the head would be to have them both open at the same time, when the piston is about halfway down the bore, then close when the piston is halfway back up for a compression stroke. Supercharger would push fresh mix into the intake, through the chamber, and out the exhaust. I think you could probably make one run like this, but I'm also fairly certain that it would run like crap. For one thing, you would definitely need to use direct fuel injection, because if you had a combustible mixture blowing in through the intake valve while there was still combustion occurring in the cylinder, well, you'd have some issues......
Reed valve intake is fine on singles or mulit cylinder motors where each clyinder has a sealed crankcase so that when the piston comes down it forces the fuel air and lube mixture into the combustion chamber. That won't work if you want a common crankcase with oil in it for luberacating the rods-mains-cam and such. Thats why the two stroke deisels need blowers. They can't ust the down stroke to force the mixture in. Go to a tractor pull and you will see many deisel engines that have been converted to spark ignition. It could be done. Would it turn out to be a good thing? I doubt it.
Actually, that could be done. You would need two very large turbo chargers that would run compounded, and install the sbc engine in place of the combustion chamber. The combustion would take place in the intake manifold of the sbc engine, and would feed into the cylinders to expand and produce power at the crank. In that scenario, you could convert the timing gear to run at 1:1 ratio, whereby the sbc engine becomes an expansion pump. I know it was a wise-ass question.... But it actually is possible Not very practical, and it would melt the aluminum pistons in about 30 seconds..... But it is possible.
I see what you mean. So, would a blower and reed valves work together? Or dry sump the motor and go that way?
Of course both valves has to be closed during compressionstroke!!!! Sorry So it may run with separate expansionchambers on every cylinder??
Your idea of turning the stock camshaft twice as fast won't work, the valves would be open only half a stroke each. If the piston was at TDC when the intake opened, it would be halfway down when the valve closed. Then the exhaust valve would open halfway back up!. Where would the compression and power part come in? This is a simplified view, so don't anybody bother reminding me about long duration, overlap, and like that!
Thats why they gave up on internal combustion engines for aircraft. The last big blown V12s that Rolls Royce worked on were making 30% of their thrust from the exhaust. The entire motor had in effect become a heavy and inefficient combustion chamber.
Now that would make it a jet turbine rather than just a jet. We all know a pulse jet is about the easiest thing to make, we powered R/C airplanes with them once. Funny....... but not many of them lasted long?? Doc.
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