The saab variable compression engine doesn't have a head-block setup. It is just one piece. It uses a mild supercharger and under cases of heavy load (standing start )uses mild (10:1) compression, but if you at light load (highway cruizing) it rotates the head and decreases the combussion chamber size to increase the compression(over 16:1!) Variable displacement is a long way away still, and probably not economically feasable. Rod's and cranks need to be very strong to take the harmonics of engines. At 9,000 rpm things inside really start to dance, and sliding hydro pins, and other sorts of goodies would not be nice. As for the wankel thing, mazda has a 'patent' of sorts on it, prohibiting other manufacturer's from persuing it too much!

 

I thought that the Saab variable-displacement motor had some kind of bellows between the head and block which moved them together or apart, changing the combustion chamber volume. I remember reading an article about something to that effect.

And a bunch of companies besides Mazda have developed rotaries in the past, even GM. Generally you can't patent something that you're not the only producer of. Everybody else just got out of the market.

 

ok everyone should be a mechanical engineer, you all like cars and how they work... there also is variable intake runner length and size, ex. the gsr manifold , toyota a manifold alone the same lines in the 80s also the runner length is used on the new bmw 7 series and ford is working on it too

 

Exactly! We have ienstien on the line! Get tipsy more and spew some more good ones dude! Your on you way to being a great engineer! :thumbup:

 

I also thought of this idea to use a specialy shaped compressor to run boost for engins at the strip ONLY! I meen it would probably only be feesable to build one that ran the car for 20-30 seconds.... Its not the PSI thats the problem... I meen you could bust out with 100 or 1000 PSI IF the motor could take it, its the velocity of airflow that bites you in the butt... Thats why you would have to use a specialy shaped compresion tank to do it.

My pops (a verry smart man) said "WHY USE AIR? WHY NOT USE COMPRESSED OXYGEN AND LOW GRADE GAS?" I have been welding for a few years now (for fun and around the house/car stuff) and I have taken a few courses in colledge... Im lincoln electric certified up to 1 1/2 inch <---- i could work on skyscrapers. BUT thats not the point. I was just telling you so that you know I know what Im talkin bout, when you mix oxy with oil or petrolium gasses it explodes! BIG TIME... So why not elliminate the entire need for spark plugs an a batterie? All you would need is a BUTT LOAD of money for motors <---- It would be damn near impossable for any engine to withstand this more that 1 or MAYBE 2 times. However if you could pull this off and make it work, we are deffinitly talkin bout 3-3.5 second timeslips!

 

Ok, a couple problems with this. As you said, oxygen mixed with gas explodes. We don't want an explosion because explosions are near impossible to time correctly at high piston speed, what we want is a controlled burn. Using pure oxygen, or even an oxygen/co2 mix is a recipe for disaster, reason: METAL even burns in the presence of pure oxygen. NASA had some astronauts on an apollo mission burn up because the capsule was pressurized with an oxygen rich environment, and a static electric discharge set it off [the tiny spark you feel getting shocked by your car sometimes after rubbing around in the seat in your winter clothes]. After that NASA did some testing and discovered you can get steel wool to harbor a flame in an oxygen rich environment.

Because of this, not only would you "need a lot of money for engines", you'd need a moron to volunteer to drive the car. An oxidizer fuel and pure oxygen, ever heard of rocket fuel? No way in hell you'll get me to drive a car trying to burn rocket fuel in a closed cylinder...

 

Hehehe.... It could be done! But not with metal.... A high density polly ceramics might do it... <---- I think my pops was just being feciecous, I bug him about engine things all the time.
First idea I had would work thoe!

 

Actually, even that first idea you had would be pretty hard to pull off. Consider industrial air compressors. A 40 gallon compressor at 135 psi will bleed down to zero guage pressure in about 8 minutes of continuous use without the compressor working to counteract, and that's through a 1/2" ID hose. You're talking about feeding a 5x mm throttle body, with enough volume to produce positive manifold pressure while the engine is trying to pump air through itself anyways. I think I'll stick with turbos, they weigh less

 

I think it'd be easier to variate the displacement by changing the bore other than the stroke. People forget that the stroke is in the crank, and since the crank is always moving, it'd be super hard to have any kinda changes happening. The bore is in the block, and doesn't move anywhere. You could have some sort of setup where the cylinder sleeves get bigger or something, but the pistons would have to change size too, so maybe they could be bigger but only have the combustion chamber as a smaller size so it would only have a smaller surface area acting on it. I can sort of see it in my head, can't see how it'd work though....

 

The more that I think about varying any of the parts in the block, the more that I think they would just simply break. Changing the size of the piston while in stroke seems extremely hard and "fragile".

I think the technology that BMW is coming out with will be a big step up (no where near changing displacement). They are replacing the cams with actuators that lift the valves. Basically its infinately variable vtec. Prett smart stuff.