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efmarek |
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ebs_4l wrote: ebs_4l wrote: ebs_4l wrote: you got the required numbers correct, but you dont quite understand why we use rich mixtures under accel.... why will fuel not burn well at 14.7:1 under heavy accel?? ill give you a hint, it does infact burn well, SUPER WELL actually, that good that it becomes an explosive mixture when you have a dense (high cylinder pressure) mixture at that ratio... as for who said that lean mixtures will melt pistons/valves because lean mixtures burn hotter, the reason parts get hotter with a lean mixture isnt to do with the gas temp, its because the mixture burns so much slower that it exposes all of the parts to the heat for longer Good one! We got another guy who doesnt know what he's talking 'bout. ok smart a**, what specifically dont you agree with in my post.... and before you reply, ill state that by LEAN mixture, i am talking about a mixture leaner than stoich... efmarek wrote: U dont know what your talking bout! U dont need a flame front. The plasma fills the whole combustion chamber instantaniously.......which means it ignites the whole volume of fuel AT THE SAME TIME. Which obviously means there is no chance for PRE-IGNITION.The beauty of it is that u can use s**t fuel for a hi-po engine. and this?? from a man who seems to be above all in the knowledge stakes... it makes me laugh to think that you would like to ignite ALL of the volume of fuel AT THE SAME TIME... imagine how a cylinder pressure graph would look if you were to infact achieve that?? conrods wouldnt be particularly happy also, do you know what pre-ignition is?? if so, would you be willing to enlighten me on how igniting all of the fuel at the same time would mean there is no chance for pre-ignition... im struggling to find the relationship between the two.. looking forward to an indepth, informative reply from you.. What i dont agree with is the errorneous crap about LEAN mixtures burning SLOWER. The whole point of richening up the mixture is to control DETONATION when under load.
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joshannon.7 |
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Age: 42 Posts: 296 Joined: 16th Oct 2006 Ride: 94 EF (OPT20), TF Cortina Ghia Location: Bendigo |
at 21 yrs old and 30 posts. what exactly are you backing urself up with.
engineering degree? Mechanic with exp? Science degree? Or cos you asked the bloke who invented them and he said so?
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efmarek |
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HAHA....science degree.
By the looks of it a science degree doesn't mean s**t. Given by what these science scholars "know".
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joshannon.7 |
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Age: 42 Posts: 296 Joined: 16th Oct 2006 Ride: 94 EF (OPT20), TF Cortina Ghia Location: Bendigo |
well what you got???
i dont got any of the above. i got a roofing licence tho. and b4 you have a go. im not saying that means i know about cars. but i have a qualification do you?
_________________ "Look I found tape, I'm a mechanic now!!!" Mike Teutul |
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efmarek |
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Why are u telling me u are Qualified to do Roofs....???
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joshannon.7 |
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Age: 42 Posts: 296 Joined: 16th Oct 2006 Ride: 94 EF (OPT20), TF Cortina Ghia Location: Bendigo |
efmarek wrote: Why are u telling me u are Qualified to do Roofs....???
Im asking what your qulified to do apart from argue with ppl who obviously know more than you. You dont even answer anyones questions you just tell everyone they are wrong and you are right with no real explination as to why they are wrong and you are right. As far as i can tell you are just a smart a'd little upstart who is going the very wrong way about making friends on here. i hope you dont need help in the future mate cos after all yr abuse and insults to everyone here tellin them they know nothing you'r gona look pretty stupid ever comin on here lookin for advice.
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efmarek |
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Im a Hair Dresser......so what?!
No im actually a mechanic.
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joshannon.7 |
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Age: 42 Posts: 296 Joined: 16th Oct 2006 Ride: 94 EF (OPT20), TF Cortina Ghia Location: Bendigo |
where do you work dude. Cos im NEVER taking my car to you.
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efmarek |
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Haha...im sure u wont.
Im a motorbike mechanic. (light engines......boats,power equipment...etc)
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fastleno |
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geez keyboard warriors
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efmarek |
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"I MOLESTED MYSELF LAST NIGHT. I SAID NO, BUT I KNEW I WANTED IT"
HAHAHA!!!
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Delta |
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efmarek wrote: "I MOLESTED MYSELF LAST NIGHT. I SAID NO, BUT I KNEW I WANTED IT"
HAHAHA!!! you seriously sound like a moron, but anyway onto some chem. The stoic afr for unleaded petrol is around 14.7:1, which is the boundary ratio required for complete combustion, ie if every oxygen molecule can find a fuel molecule during combustion then both will be completely used up. This DOES NOT mean that the reaction has been most efficient!!! There are plenty of reactions in chem which are performed under a condition of excess of one or the other reagent. There are a very large number of factors to consider for this kind of reaction, piston speed (hence the time you can actually combust for), pressure, temperature limits of materials, instantaneous strengths of components etc, all come into play. In general the leaner a mixture is, the faster it burns, due to the fact that the fuel molecule is much slower moving than an air molecule and with a leaner mixture the probablility of a fuel molecule pairing with an oxygen molecule is much higher. This however introduces the posibility of random flame fronts which interfere (insipent detonation) AT SOME AFRS AND AT HIGH CYLINDER PRESSURES, but mostly at those afrs close to or slightly leaner than stoic (14.7-20:1). To combat this we can do many things, but reducing cylinder pressure by "buffering" is one way, you add fuel which makes the mixture rich, this means that a molecule CAN'T find an oxygen molecule to burn with in the usual way. but if you cram them close enough another reaction takes place, where carbon monoxide is produced instead of carbon dioxide, to cram them closer together and to move the molecules fast enough so that they actually find this rarer case requires more heat energy absorbed by the fuel molecules, which slows the reaction and makes the reaction cooler, at the expense in this case of energy production. The COMPLETE opposite of this is to perform the reaction in a MASSIVE excess of air, in this case a fuel molecule can very very easily find an oxygen molecule and the resultant reaction is much cleaner and produces more energy than a rich mixture, however now the reaction does not form a flame front, more it forms a pressure front. In this case you are actually trying to spontaneously detonate the mixture! Spontaneous detonation is were a chain reaction causes massive cylinder pressure due to the reaction happening spontaneously in many or all pats of the chamber at the same time rather than in a front. This is generally VERY dangerous at mixtures around stoic or slighty leaner, however the amount of nitrogen in air tends to help buffer this IF enough air is present. Hence you need afrs around 25-35:1 (IIRC) which allows complete combustion, and still allows a reasonable amount of air to form a buffer, and transfer the energy by compressing the buffering air, which then releases that energy by expansion much more slowly than the pressure front which is generated in the explosion. This very lean system of combustion is the way in which continuous fire engines work, otherwise they would melt all their internal parts. IE a jet turbine engine uses a dense energy fuel which takes a long time to burn, thus it burns cooler, however since it is burning the fuel CONTINUOUSLY it would still impart enough energy to destroy parts, so the reaction takes place in a massive excess of air and runs a lambda of 1.9-2.1 or so. The unburnt air is used as a heat buffer - it transfers heat energy into potential energy and kinetic energy by moving the molecules closer together, and making them vibrate/move faster this energy is transfered later in the cycle (at the turbine) where a pressure differential and heat differential turns the tubine of the jet engine. bah, seriosuly long post and I still have lots more to say and I've only scratched the surface.... lets sumarize for those who can't be bothered reading stoic AFR has nothing to do with peak efficiency. and engine CAN run at an AFR of 30:1 (or so, under certain circumstances) these plugs (if they do what they claim) actually INDUCE detonation (sort of - detonation as defined as a spontaneous explosion at many points in the chamber) but in a way that means you can get lots of power from a very lean afr. efmarek: it is obvious since you did not offer an explanation like this that you know nothing of the chemistry or physics involved, and that you are highly likely to be just another moron sprouting someone elses crap. Please prove me wrong by entering into a realistic and insightful debate about what I have just said, and what you know of the product rather than mouthing off, as if you do just mouth off, you prove that your a moron....and I have no time for morons. |
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Delta |
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joshannon.7 wrote: at 21 yrs old and 30 posts. what exactly are you backing urself up with.
engineering degree? Mechanic with exp? Science degree? Or cos you asked the bloke who invented them and he said so? To add to my previous post (as I only have 37 posts and I'm only 25) I have an engineering degree and am currently undertaking a PhD, I also teach university students in the areas of engineering, physics, and motorsports. Hopefully that is enough to recommend me, haha, If not then I guess I retract my earlier physics and chemistry lecture |
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blackjack_original |
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Posts: 3516 Joined: 8th Nov 2004 |
[self-deleted]
Last edited by blackjack_original on Fri Jun 06, 2014 10:45 pm, edited 1 time in total. |
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Delta |
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blackjack_original wrote: A very interesting and informative read. So let me see If I understand this.
In a nutshell, when you lean out and start detonating, you'll blow your engine apart; unless you lean out so much that the excess molecules of oxygen and nitrogen and other air molecules? start acting like shock absorbers and slow down the detonation pressure front, thus not blowing your engine apart. So, if running 15:1 you will blow your engine to smitherines but at 40:1 you are safe? And so, if these plugs induce detonation, you'd have to tune your car to run at 40:1 so it doesn't fall apart. Did I understand this correctly? If so, what is the point of running at 40:1? Running at your normal AFR, versus running so lean that you need to slow down the pressure front. Is the advantage of this, burning all of the fuel, therefore better efficiency? If this is true, I still don't see a 44-50% increase in fuel economy. Do you? I still think the spark plugs ar s**t, but you've now got me thinking. Tell me more. You got it I think these plugs would work ok with normal afrs, probably a bit better fuel economy etc. Its more along the lines of, with these plugs (if they even work) you CAN run 30:1 as they allow you to instantly ignite the mixture everywhere (sort of). The advantage of doing this is actually two fold, firstly you actaully burn every molecule of fuel, hence you release all the energy you can. THe other benefit is that the excess reaction means that it will highly favour the normal reaction of combustion where carbon dioxide is formed, and this reaction releases much more energy per unit of oxygen and fuel. You will find, in the rich case that the amount of fuel not burned plus the percentage of the reaction that yields other gasses such as carbon monoxide means that for the amount of petrol you put in, you perhaps got 60-70% of the maximum energy possible involved in the reaction. The lean reaction you get all the possible energy as pressure and heat. Because the lean reaction occurs much more rapidly the pressure also has a longer time (or should I say takes less time) to exert a (the same) force on the piston, and hence turn it into rotation rather than pressure and heat leaving the exhaust. So yes I believe with faster and more efficient combustion that its possible to have a marked increase in fuel efficiency, 40-50% tho I doubt. without real life tests I wouldn't hazard a guess tho as it could be anything. The big kicker here tho is how do you get enough air in the cylinder to make it all worthwhile? up until around 15:1 you can actually make the same sort of hp as at 12:1, any lower than that and you make less power, as you need to massively reduce timing, as you approach the 25:1 mark you _need_ detonation to make reasonable power as this seriously increases cylinder pressure. You will however NOT make the same hp as the same engine at 12:1 and the same revs, you will make less, unless of course your engine is designed with the detonation principle in mind (as with anything tho). You will also find that the way combustion takes place means that lots of energy is imparted in a very short space of time, hence you want detonation to occur at or after TDC and that you need high revs to make it really efficient, ie this method of combustion is more efficient at high revs than the normal otto cycle, hence it needs more revs to make the same power. It is most suited to short stroke engines that rev very high as the time spent expending energy is closer to the time that the piston travels in the downward direction on the power stroke. SO basically this "cycle" makes less low down torque and more top end power, like having a bigger cam, but with reduced fuel consumption. To make the same torque you would need to ingest a little more air (cam change/forced induction/larger displacement) to equal the hp you could raise the rev limiter, as this process will essentially extend your current cam range. By putting a smaller cam in, you would achieve some of this guys claims, ie, similar torque/hp, but better low speed idle and lower fuel consumption. |
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