h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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First some background facts for thoes who may not know:
1) the runners are the pipes that connect the individual combustion areas in an engine to the large part of the intake maniforld (the plenum)
2) the air that moves through the plenum is relatively low velocity and high pressure compared to
the air that moves through the individual runners (see bernoulli equation)
3) during the intake stroke of one of the pistons, a valve allows air to flow through that pistons runner. when the intake stroke is ending, the valve must close to stop air flow and isolate the combustion charge within the combustion area.
4) when the valve closes, the quickly moving air that was passing by it is quickly brought to a halt since it can no longer go into the combustion area since there is the head of a valve blocking it.
5) air has inertia, so when the first bits of air hit the head of the valve i nthe runner, the air behind it "three stooges" into the back of it, forming a small area of very high pressure right near the valve head
6) that high pressure area bounces back toward the plenum.
7) when that wave front of high pressure hits the plenum, which is an area of relatively high pressure, it "three stooges" back again toward the valve head.
8) this process repeats itself a few times before damping out naturally.
Now some engine theory:
if you tune your intake runners to a certain length, you can time it so that when the air is about to bounce off of the valve head for the second, third of fourth time, the vavle is opening for the NEXT intake stroke. if the high pressure front meets up with the valve opening correctly, it will help cram a little more air in the combustion chamber, and you get more power with no extra thermal efficiency cost (since the air was going to bounce around in this way anyway.)
the bad part is that engines cycle through a rev range (usually) and one could only tune the runner length to benefit the engine at a narrow rpm band. (well made engines have long runners to get a little boost at low RPM, or short runners for up high power. look at an F1 engines runners!)
after that long winded into i'll get to my idea:
use electro morphouse polymers that change shape when a current is applied to them. this technology is largely being developed in the bio-med field for artificial muscle tissue. there are varous types of polymers that do this, with different charecteristics. usually the traits that are taken into consideration in the bio-med field are:
1) how quickly the shape can change
2) how strong the tissue will be (yield strength)
3) how much force is excerted by the contraction
4) how rugged it is (how many cycles it can go through)
for the application i am about to describe, thermal effects would also have to be taken into account.
so the idea is that you make the runners out of this stuff. instead of a strand for an artificial muscle tissue, use a tube for an intake runner. run voltage through it regulated by the ECU, and you would be able to get peak performance from your runner length all throughout the RPM band (since its length would be a inverse function of crankshaft rotational speed). Buckey gell (from buckminsterfullerene) would probably the best candidate for material that is currently in development. it is essencially layered sheets of 4-bond carbon (ever hear of a buckey ball? this is the planar version). it has good thermal properties, and by adding elecromagnetic imperfections in the matrix of carbons, as crosslinks between the sheets (i think), one could run a voltage through the gell (which would be more like rubber when looked at macroscopically) and change its shape.
i know that at least one major manufacturer (toyota i think) has done work on twin runner length technology. in this case there are 2 settings of runner length. there are essencially 2 runners per cylinder that ark from the plenum to the block. one is the "inside track" of the ark and is therefore shorter. the other on the outside is longer. i think they switched from long to short via a butterfly valve when the engine hits a certain RPM (actualted by the ECU i would imagine). this means that there is a reasonable interest in variable runner length in the market.
engine theory page
http://www.billzill...gineintro.htm#Inlet
[auricom_mech, Aug 02 2006]
runner length calculator
http://www.bgsoflex.com/intakeln.html
[auricom_mech, Aug 02 2006]
how stuff works article
http://auto.howstuf...com/question517.htm
[auricom_mech, Aug 02 2006]
bio-med link
http://www.deviceli...hive/99/08/004.html
[auricom_mech, Aug 04 2006]
Baked by BMW
http://67.153.245.1.../intakemanifold.htm
A Continously Variable intake Runner. [jhomrighaus, Aug 04 2006]
[link]
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There has got to be a simpler way..
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I have been toying with the idea that metal is not a very good material for quite a few engine parts (check out the use of carbon on F1 engines). |
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Why not use rubber coated springs for the runners and stretch them as required? |
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Ok, I got bored in the middle, but I will still bun it for use of "three stooge" as a verb. |
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I think the benefits of such a system do not warrant the complexity. The 2 position thing has been experimented with but we are talking 1 or 2 or 3 % changes in the overall output of the engine. Also I think you are somewhat confused about what is going on in the intake manifold. |
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The benefits behind tuned length headers are not to keep the air from bouncing around in the engine. In general under hard acceleration the area around the Valves is actually at a subambient pressure, while the pressure in the plenum is around ambient. Also you can not look at each runner on its own, Valve closer is a progressive process, not instantaneous, and as such the forces you describe arent really representitve of what is happening. As one valve is closing another is opening so the overall pressure balance within the system is equal. The difference in lentgh from Low to high RPMs are rather Drastic, and generaly affect the cyclinder vacuum that builds up,(shorter Runners at High RPMS , means less air restriction, less vacuum) and longer at low RPMs means Smoother flow less vacuum.) |
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This is a lot of Mumbo Jumbo, It would probably make some measurable difference but not enough to justify the cost. |
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jhomrighaus:
maybe i didnt explain this well enough, but it looks like you are confused with at least PART of what i am describibg here. let me try and clairify:
i am not trying "keep air from bouncing around in the engine" i am COUNTING on the air bouncing back and fourth in the RUNNERS. also, i said in my original post: "high pressure hits the plenum, which is an area of relatively high pressure" RELATIVELY high compared to the runners..... |
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in your post you (corrected me?) by saying: "the area around the Valves is actually at a subambient pressure, while the pressure in the plenum is around ambient"...yeah i know this, its a big reason this idea would theroetically work, and how is this in disagreement with what i originally said?! |
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you also say: "As one valve is closing another is opening so the overall pressure balance within the system is equal" yeah, i am awair that under constant RPM the manifold is at a net *steady state*, but that doesnt mean there arent dynamic pressure forces moving around in its subcomponents. as far as the gains you will get out of this...no it wont ikely give you 20 or even 10% more power, but how much time and money do you think race teams spend on sqeezing avery hp out of engines that are pushed to the limit. plus this is power is "free" which i think is a major advantage. these air pulses would be bouncing around anyway, so why not harness them. if you dont believe me that air behaves this way in an engine maybe you will believe these people: |
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please look at the second link in particular (i am sorry if i posted links in the wrong location) |
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Well those are some truly authoritative links, the second one doesnt work by the way. |
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You are picking out one very small little detail from a basic description of the flow dynamics of an intake plenum and runner and turning it into an incredibly complex idea that really doesnt address the underlying goal. |
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One of the reasons indy cars dont have variable length intakes is that they dont need them, the engine is run at or near its optimal RPMs (the point for which thier intakes are Tuned). Other vehicles dont have them because they dont need them, the benefits are outweighed by the complexity. |
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It is very easy to build a tuned length runner using a convetional Trumpet Runner, the problem is that the thing would need to Shrink from like 1.5 feet to like 2 inches in order to cover the full range of RPMS it encounters and even then the HP gain would be offset by the increased weight and aerodynamic penatlys needed to fit the thing in the car. |
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Shape changing materials are really cool, but this concept is a)pointless and b) outside of the tecnical abilities of the material. This is approaching the level of "wouldnt it be cool if" IMHO. |
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did you take the spaces out of the second link? (again im sorry i had to add them) |
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//from like 1.5 feet to like 2 inches// |
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very true, this is a problem with my design. |
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//the benefits are outweighed by the complexity// |
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this may be expensive, but where is the complexity? the machining may be complex, but the implemented system would be no more complex to the ecu then a fuel injector (with a wider tolerance i might add), no more complex geometrically than a normal intake manifold, and no more complex in mounting, aside from clearing space for it to move (which i agree is the biggest problem) |
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//increased weight and aerodynamic penatlys needed to fit the thing in the car// |
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aerodynamic penalties: maybe, but it could also be designed around. |
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weight: when they strech they dont get more massive.
diamond: 3.52 g/cc
aluminum: 2.70 g/ cc
i cant find the densities of bucky gel, but its theoretical upper limit is that of diamond (which i would guess is actually considerably less dense than diamond. yeah it might be a tiny bit heavyer, so i'll buy you a carbon fiber radiator mount to cover the difference. |
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here is a more credible source:
[link]
you saying this is pointless ls like a person saying that tuneing your intake runners in general is pointless. |
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You do know you can add links right? |
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i'm sorry, i am new here. the links are now in the proper place. |
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I'm not seeing this as a plausible way to make power in the form you suggest. From my experience, longer runners make more power up high, and shorter runners, down low. Why else would companies such as Edelbrock and others make "street" manifolds, made for low RPM use, with short runners, and race manifolds, such as tunnel rams and long runner single plane manifolds that peak power at high RPM's? but as with anything, there is a tradeoff. For the high RPM power (6500-8000 on a small block Chevy), a tunnel ram is generally used, but the sacrifice is the low end grunt and driveability because of low vaccume and bad throttle response. The power is made (as I understand it) by the velocity of the air going through the runners at high RPM's. I could be wrong, but I believe that more power is to be had by adjusting the length with the RPM, not the inverse. |
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Clearly this is a well researched topic and therefore the idea is sound. Having had a look at the inlet runners of some jap performance vehicles I can now understand why they are so long. |
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Pity that the 5, 6 and 7th harmonic are not significant because then shorter runners could be employed. |
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Pity also noone has started to think about an elastic inlet runner (like the rubber ones I suggested)... What if the pressure wave of the inlet valve was absorbed by the runner --- so that the runner material bounces back at just the right time to increase pressure at the valve. |
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Hunter:
i can not say if the specific cases you mentioned are true or false, but i assure you, long runners are for low RPM, short runners for high RMP. i have looked this up from several seperate resources, i suggest you do the same if you do not beleive me. |
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madness:
yes you may be on to something with your rubber runner and spring idea. one of the things that drew me to the electro morphous polimers though, is that they can streetch at different rates in different directions. or, in this case, streach in one direction (length) and not at all in the other (radial diameter). however the main problem i see with rubber is that it's polymer cross links (i suppose they would be sulfer from being vulcanized) would break down after such extensive streching...i could be wrong about this, and there may be some advancements in material science i am unawair of, i'll look into the rubber idea. and the whole idea of part of the shockwave traverling through the runner itsefl is a good one (i think thats what you were saying) |
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also, if this were to be made out of buckey gel, it would be VERY stong, and could be made VERY thin, and so it would be light weight. also, i know carbon itself is a poor conductor of electricity, im not sure about its thermal conductivity, but i think it would be low, just based on its electro-conductivity. if this is true it would minimize heat soak from other parts of the engine as well. i'll look into this too. |
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I'm not going to lie. I didn't read past the subtitle. Quite frankly, given my level of knowledge when it come to car engines, I don't think it would have helped. Thus rather than bone it because I can't be bothered to work out why it's a good idea, or bun it because new users need all the encouragement they can get, I'm going to stay neutral. |
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Welcome to the HalfB, [auricom_mech]. |
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Yeah, what [Mister Phase] said. |
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Hmmm I agree --- I like the idea that this material can stretch in one direction and not the other... |
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I figure this means it becomes less dense...? Not sure how that works though...? |
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//Not sure how that works though...?// |
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Dont worry, noone else does either, The major issue with these materials is that they are highly experimental and dont change size or shape very much at all(human Muscle tissue still is much better at this and it could not deform sufficiently to make this idea work either) Something that has been glossed over is that there is no material today that could do this job as described, the closest possibility is the rubber spring idea, but that has issues as well. |
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thanks for the welcome guys. |
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i found a link for this stuff:
[link] |
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a quote from the linked article: |
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"Adding sodium hydroxide or another base causes the fibers to stretch to as much as twice their original length" |
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For this to work though you would need something like 500 to 1000% increase in length, You would also need it to be rigid, to contain the shockwave, otherwise the material would flex and all the energy in the wave would be absorbed and you would lose your 1% increase in power. |
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Baked(using different Method of Course) see link, BMW has already done this. |
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this BMW manifold looks interesting. does anyone get how it works? maybe i missed something on the page. maybe the creators don't want you to know exactly how it works...any thoughts? |
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jhom:
my idea wasnt as simple as "make the runners change length" so no, it's not baked. (IMO) |
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also, do you still feel the same way about how "pointless" it would be to alter the runner length? |
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Tuning the length of the intake manifold is critical to how the engine breathes and its power characteristics. Wanting to use materials that don't even exist yet, as a complex method of doing something that is already possible, isn't a way forward that I can seriously support. |
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For a start, such an electrically activated material would need to be powered constantly, whereas changing the length of the runner (for a crude example, consider a trombone slide system) should only require a single input of energy to move the slide, after which no power should be consumed (work done = force x distance, and no distance is being travelled). |
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Quite definitely, the benefits are outweighed by the complexity. If you were to use a mechanical system, that would not be so. |
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considering all the otherthings that can be done to improve engine performance I would still say that it is pointless.(putting a wing and high performance tires on a geo metro is also pointless) |
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BMW has made use of it on its flagship car(about 100K plus) to gain a small increase in HP and Torque. for the effort involved the benefit is minimal, IMO. |
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A turbo or SC would generate far greater benefits, use available technology and probably just Work better. |
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these materials do exist, and voltage is only required to alter the shape, not to keep it where it is. and not much 1 to 4 amps apparently. |
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i'm not suggesting we would want this in cars that cost less than $100,000. and what is your definition of "small increase"? this system would not increase the peak HP at all, it would considerably widen the power band though. i could be wrong, but i dont think you know enough about this specific topic to be making the kind of judgments that you are. feel free to prove me wrong on this. |
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maybe i didnt make myself clear: this would only be practical when little else could be done to the car to increase HP. have you ever heard of a 3 angle grind?! why would people spend so much time and something that only yields a few HP?! i can think of several other examples if you are anti-3 angle grind for some reason! |
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As to BMW intake, I believe you have a large ring with a smaller hollow disc inside. The air comes in thru the center of the disc and out through an opening in the perimeter of that disc. As the disc is Rotated the opening will be nearer or further from the inlet Valve thus allowing for a Tuned runner length. |
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10 years of restoring cars and learning about cars is all i bring to the table. There are a thousand things one can do to provide small increases in HP(ive probably wasted money on half of them) Most of them only make a difference if you are racing your car(thats why F1 cars cost millions of dollars) but for general use most of those improvements are pointless. lets take for example the Typical US car nuts normal improvement path, K7N air filter(1% increase in HP but essential for a performance motor) Wide bore low back pressure exhaust(1-2% increase in HP, essential for HP engine)
HEaders(ditto)performace Plugs(0% ditto) performance wires(ditto)Performance Coil(ditto) |
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After all of this then you move to serious stuff, Cam, Crank, Bore, Stroke, Forged Pistons, 3 angle Valves, Port& Polish, new intake, Turbo, Supercharger, Retune ECM, Wider TB, MSD ignition, aluminum Block, Ceramic Coatings, Nitrous, blah blah blah blah blah. |
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All of those together and you have a potent package. any alone and you got not much. |
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Is the Concept of Tuneable intakes a good one? Yes of Course, thats why BMW has taken a stab at building one. IS your Idea a Good Idea?, Sure, but its a Baked Idea. But your idea is different it uses special materials! But those materials are not suited to the job and do not exisit in any useable form in some ways its almost magic, or wouldnt it be cool if we had a special material that could be reformed. These are my issues with your idea. It is mostly Baked, mostly pointless and thats why it got bones. |
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In general I will say you have some interesting ideas, just be careful of trying to reinvent something like the venerable automobile engine. There have been a lot of really really capable and intelligent people who have worked on that problem and there are very few "original" ideas out there to be found in this arena. Try applying some of these concepts to other unrelated things and you will get lots of buns. IE like "constantly variable tuned length spitwad shooting soda straws" I would Bun that in a heartbeat ;-) |
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hmmm...i am mentally picturing 2 possible ways that the spinning disk (plenum equivalent?) would interface with the tubes (runner equivalent right?). in one case, it seems like too much turbulance would be created. in the other case i am picturing the runner smothly curls in to "bacome" the plenum. maybe ive got it mixed up in my head. regardless of the way it works, if it in fact DOES work, then i would say that it beats my idea. i still stand by my view that this doesnt necessarily bake my idea...that would be like the idea for a turbocharger being baked by a supercharger. good work on finding this thing though, i'll look into it more (if i can find anything). |
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alright i can respect all thoes things you said. you just came out a little over agressive about it initially(IMO), so i guess i probably got a little over defensive of it. |
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i just DISagree with ONE thing you said in your last post. regarding the material: its not even close to being "magic" there are several patents in the works regarding application of this material right now. |
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i strongly agree with what you said about other inteligent people trying to re-invent the engine...thats why i was trying to look into revolutionary new materials that noone considered would EVER exist 50 years ago. you see where i am coming from on this one? (and i mean with respect to what i just said in this paragraph, not in terms of this idea) |
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i am no material scientist, but as an M.E. i will certianly do what i can to use new materials in new mechanical ways. |
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I agree, but the materials you are looking to are generaly finding use as actuators. I belive many of them look and behave like waterlogged bungie cords that change length based on an electrical or chemical stymulus. They are just not suuited to this application. Something like a Memory metal might have more promise success. |
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yeah, but heat soak issues.. |
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i just found out that older F1 cars had some sort of variable runner system, but its been damn near impossible for me to find any specifics on it. does anyone know of a GOOD site about F1 engine theory/history? |
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