Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

six stroke motor.

Discussion in 'The Pub' started by idontlikemondays, Dec 16, 2007.

  1. http://www.bajulazsa.com/Site/sixstroke.html

    there are some pretty serious claims to improvement over a conventional 4 stroke motor. including a 40% improvement in effeciency.

    despite the doomsday sayers, we are not about to run out of crude oil, and this could be a viable realistic solution??

    i know there are some knowlegable mechanical engineers here, could we see this in the future??
  2. Unsubstantiated clap trap!

    The power efficiency of the int comb engine results from expanding gases directly acting on the piston not in some chamber off to the side....

    This engine may well run but it wont be powerful.

    My 2c worth.
  3. The advantage of 6 stroke engines isn't outright power efficiency it's emmisions efficiency.

    The isolation of clean air from fuel from burnt combustion products is easier.
  4. more emission efficiency less power. what you make up for in increased emission efficiency you lose as you need more fuel in order to create a similiar amount of power that other, slightly less emission efficient cars can put out with less.
  5. Exactly the argument that was used against the catalytic converter, but I don't see that going away any time soon.
  6. Well seeing as the benzines that the catalytic converter removes are pretty nasty I can't see them going away either. That's still not a reason for the six stroke engine.
  7. My point, you....whoosh
  8. I don't think there has ever been a creditable case made that any emission reduction has been cancelled out by a loss of engine efficiency

    And a lot of emission decreases have been made increasing engine efficiency.

    The only thing I remember hearing is that some turbos although delivering less emissions, delivered more toxic one's, but don't quote me on that.
  9. there was another form of the 6 stroke motor, it injected water into the cylinder, which was so hot it immediatly vapourised and expanded to 1600 times its original liquid volume

    the obvious problem is carrying water around, and corrosion. people come up with some wierd shit.
  10. Ultimately all this engine is doing is introducing more exhaust gas (more or less inert, but still quite hot) as a combustion stabiliser much like EGR (funnily enough - Exhaust Gas Recirculation) valves have done (especially during light throttle cruise power settings) on most cars for the past 25+ years.

    I guess it just takes that concept one step further buy using two power and two exhaust cycles thrown into the normal 4 cycles. I don't know how much power you would lose (if any). When you think about it, a secondary ignition stroke would take place at the same time as another cylinders' primary ignition stroke.

    Good chance it would make more power in all honesty.

    Stigger, combustion temperature will govern how much of what gas is produced/exhausted. Usually the amount of O2 and NOX leftover/produced, and to a lesser extent the CO.
  11. There isn't 2 detonation cycles though, there are multiple intake/compression cycles but only one detonation. and its taken 3 revolutions of the engine to do it. Whilst possibly more efficient, it seems to definitely be less powerful.

    If the detonation were to take place in the cylinder, it may improve, but the current system of detonating in that pre-cylinder, and then pushing all the racing hot gases through the bottleneck of that tiny valve in order to exert force on the piston, what a waste. Maybe the pre-cylinder can be relocated with a much larger valve for that part of the cycle, to allow better flow?
  12. People need to get away from the obsession with peak power... torque is more important :)

    Even if there is a reduction in peak power, as long as torque & power are maintained at normal operating revolutions, then it will make no difference to the 95% of the population who just use cars to get from point A to point B.
  13. Correct to the point of there being (I think they called them) "work strokes" - I called them "power cycles", whereas the correct terminology is "ignition" stroke for a 4 stroke engine. My bad too... :?

    I agree that from the outside it would appear (for a spark ignition engine) that it would be less powerfull. The concept they are using (and it would appear to me to be a diesel engine with that injector/glowplug set-up) has it's foundation in a process found in high bypass turbofan aircraft engines that use a small (but intense) flame front to engergise a much larger mass of air. It is the way they do it that varies.

    Where they are coming from with the pre-chamber combustion (and believe me, possibly like you I am looking at this concept here for the first time as I was unaware of it until I saw the link at the top of the page) is getting two shots at using a parcel of superheated air before losing it out the exhaust valve. Most engines (both compression and spark ignition) will still have burning (and still expanding) gas/mixture exiting past the exhaust valve when it is open on the exhaust stroke, therefore taking thermal energy (and some thermal efficiency) with it, with the added heat stress on the valve and seat faces etc. I guess the idea for this engine is to start the expansion off earlier in the pre-chamber (of which there are a number of diesels that use this concept) and get two shots at using it, therefore going away from the normal accepted method of having the "controlled flamefront" (and hopefully not a detonation) right over the piston crown.

    This would have a couple of advantages....

    A slower mass expansion..... lessens the chance of pinging (the piston rattling around in the cylinder like a bell), and the elimination of hotspots in the cylinder creating detonation causing a thermal runaway on a diesel engine. And,

    A longer mass expansion..... which means that the heated air can be made to do more useful work inside the engine before getting rid of the byproducts of combustion. The cycles wouldn't be limited to the length of the piston stroke before the exhaust valve opened and let all that warm gas out into the atmosphere either.

    While I probably sound like I'm sold on their idea, I can see benefits for large plant and trucks, but I cannot see this engine making many inroads into petrol car engines as they would be lazy revving and not gain wide acceptance.

    Exactly - Power is how fast you hit something, torque is how far you'll drill through it..... :grin:
  14. I agree with what you are saying, but in the animation they provide, whilst they are using each ignition cycle again, it seems all that is going on is a pre-heating phase in the secondary chamber. The literature provided seems to point to that as one of the intended goals, so yes, they are losing less of the usable energy to heat escaping out the exhaust. But my point is it seems that there is only one power stroke to the top of each piston, per 3 revolutions of the crank, unlike a 4 stroke that has a power stroke per piston for every 2 revolutions of the crank. So whilst they may have a better thermal efficiency, they are actually having to do more work for the same or lesser output at the flywheel.

    So what this then leads to is while it is probably "lazy" revving as you put it, it may actually have more torque. Because like you said, it seems it would have a longer and slower detonation, allowing for similar amounts of explosive energy from the same amount, or less fuel. So then the fact that each of these cycles spends its energy over 3 revolutions instead of two, forgive my terminology cos I'm no engineer, but would that be the same as using a low gear on a push bike? your legs are going a million miles an hour, but the back wheel is going ever so slowly, but you can power it up a hill no problems. That's torque yeah?

    I'm in two minds, it will be interesting to see where this all leads. To me it appears like you said I think, slow revving, possibly more torque, and if that is the case, it would have wide range usage industrially, but for the general purpose driver, maybe not so much. Actually I read your post again before hitting submit, and it appears we agree...

    I can do science me? :LOL:
  15. Nothing new. The six-stroke engine was first invented back in 1883 by Samuel Griffin mainly as a way of getting around Otto's patents.

    The big problem has always been that the thermal efficiency simply isn't increased enough to compensate for the power required for the extra cycles.
  16. I thought it sounded familiar :grin: . If I remember right, the extra strokes were used to scavenge the cylinder with fresh air, ready for the next charge.

    Lot of mucking about foir limited gain, although I believe many were used on things like agricultural bore pumps.
  17. If you'll pardon the really bad pun.... I think we're in heated agreement....

    OK, I know..... :wink:
  18. Makes sense, there was a gain in fuel consumption which would be a plus there and the extra weight wouldn't be an issue.

    And just to show there were even crazier designs to avoid patent infringements:
    The 8-stroke engine (Basically a normal 4-stroke in which the pistons did absolutely nothing for one complete cycle).
  19. I've never seen or heard of one of these beasties before. Using superheated compressed air to lengthen out the cycle sounds like a stroke of genius. The bottle neck issue sounds right though, so it's probably not a peak power beast, but put one on a small car with a CVT and you could have a brilliantly efficient city run about.

    I can see some serious thermal and cyclic fatigue issues with that double walled chamber though... and the manufacturing complexities... they'd be a study and a half.

    There's very little info on the web regarding the workings of Griffin's 6 stroke engine, so it's hard to know whether the OP engine is the same or different... so I'm not ready for a pfffft, it's been done kind of response.

    Another 6 stroke engine (uses water):

    And another one (add on to 4 stroke bottom end):

    And good old wiki has the trifecta:
    http://en.wikipedia.org/wiki/Six_stroke_engine (still nothing about Griffin)
  20. I'm sure I've got some info somewhere on the Griffin engine. Pretty sure it was as PatB described it, ie simply using the extra cycles to flush the combustion chamber (much like with the 8-stroke).
    Some of the new designs are different, especially the one with water injection, but as the difference between 2 and 4-stroke shows adding complexity to the process doesn't really help when it comes to power or weight. Not to mention the fact high temperature steam is corrosive to pretty much everything.
    Where this 6-stroke technology may become relevant though is in reducing emissions - though ironically this may come at the cost of increased fuel consumption (since the engine is heavier and puts out less power).