george wrote:tell me about your set up the link you mentioned doesnt work. i am interested to see what you are running ...thank you

here is a link to an older site....will give you the jist of my project...

http://www.sdsefi.com/features/oct01240.htm

First of all, atoms and molecules are two completely different things, so in reading some of your posts, I get confussed. Metals' bonds are not formed at poles, they share electrons. If they were polar bonds, like some of those exhibited by minerals and conglomerate rocks, they would be exceptionally weak, and have cleavage planes. No metal has cleavage planes, though, they are across the diagonal line from metaloids on the periodic chart. They fracture concoidally, meading in any given random direction, and without pattern. If heat causes manifolds to crack, how do cast manifolds not crack when poured as a molten liquid nearing as much as 14,000 degrees farenheit; and how is it that a thin metal pipe can be welded with an arc temperature of over 10,000 degrees farenheit without cracking, but when you bolt it onto your car that never even heats it up to within several thousands of degrees of what these things were made at, they all of the sudden start cracking under the heat? Velocity is a technical term that applies to a mass that has both a speed and a direction, two things energy in the form of heat do not have. Here is some other food for thought: "Detonation: This is a supersonic combustion wave. Detonations in gases propagate with velocities that range from 5 to 7 times the speed of sound in the reactants. For hydrocarbon fuels in air, the detonation velocity can be up to 1800 m/s. The ideal detonation speed, known as the Chapman-Jouguet velocity, is a function of the reactant composition, initial temperature and pressure." Considering the compression ratio raises the combustion pressures during the compression stroke of the motor, we may pressume the potential for a lean fuel mixture to detonate in the chamber prematurely would result in this elevated detonation speed of anywhere from 1100m/s to 1800m/s. Any combustion below the speed of 1100m/s would not technically constitute a detonation, and I hope you are not detonating. John

I had to make this two posts, the last was too long. If your A/F ratio is JUST a touch rich (Which would be wise for power and temp. control) the rate of expansion in the gases would be dramatically reduced. Compounded by this is the fact that the gases will travel their FASTEST velocities upon ignition. Actually, to be more correct, it wouldn't be called the "point of ignition", rather, the "point of combustion." Ignition is a term, which in scientific jargon, does not imply the speed of the gaseous expansion is high enough to produce useful amounts of horse power. Combustion is a term applied to a rate of gaseous expansion greater than 3200ft/s, or 1066m/s. A narrow window for proper combustion to occur, without atchieving detonation. At any rate, it is at its fastest in the very moment of combustion, when the expansion drives the piston down, turning over the crank. There is no doubt that this event takes place well beyond the speed of sound. The gases have finished their rapid expansion, however, by the onset of the upstroke to expell the exhaust from the cylinder. Too much of the gases' energy has been transfered into rotational motion to be travelling at the speed of sound beyond this point. The gases are now only travelling at the rate at which they can be expelled from the chamber, through the valve, and into the exhaust port by the piston. Once they have made it into the primary, they are travelling relatively slow (considering their recent past). The constrictions of having to travel through pipes, around bends, and eventually into a turbine housing (in a turbo app.) only slows them down more, whereas in your previous statements, the gases are now SOMEHOW picking up speed. That would be impossible, because there is no force acting upon the gases to accelerate them. The only forces are friction from the pipe (neg. force), the air resistance ahead of the gases (neg. force) and the push of the gases from behind them that are just now trying to escape as well (pos. force). The force behind is not at all enough to speed these gases up, just enough to keep it moving. John

*head explodes*

OOOOOWWWWW.

geeze. thanks for the info...:p

-chet

sharing of electrons...by atoms to form molecules exactly. the force exerted on the gases as they indeed pick up speed in the mani is called heat...this "excites" the molecules and increases thier velocity. the speed at which the gases are expelled from the combustion chamber is not that of the rate of expulsion. the shear temperature of these gases increases that speed, as mention before excitement of the molecules. out the combustion chamber in to the manifold where they pick up more speed due to the diameter of the mani, its length, and heat. since the exhaust gases are trapped in a small diameter tube and "pushed" in a specific direction by exhaust gases that follow this causes them to acclerate. to say that exhaust gases rush out the combustion chamber at "the speed which they are expelled" would imply that they have no molecular aggitated movement and thus would not spool a turbo.

Johon what do you drive man?

Heat is not a force, and it does not act upon the gases; molecules do not have a velocity, because they are not going anywhere. Heat is a form of energy that the gases possess, an energy that they lose at a constant exponential rate. They lose heat initially at the greatest rate, but as they are contained in an environment that can only absorb so much heat energy without getting hot itself, they begin losing heat at a slowwer rate. The molecules of the components that come in contact with these gases are being heated up, and yes, become "excited" as you put it. They do not grow, though, in a literal sense; they vibrate at higher and higher frequency. Think of it as aggitating a bee hive. The more pissed off they get, the louder they're gonna bee (haha). This action in the molecules, though, actually makes the bonds stronger by means of allowing greater flexibility. Subatomic particles become more active with heat, and less with cold; in this case the electrons are moving faster, and therefor holding together stronger. Think of a snorkel, and how if it is too long, no air can be drawn through it. This is because the volume of the pipe is too small, or the length too great to allow the free movement of air to any useful capacity. If your principals were correct, this fact would be nul and void. You claim that the longer the pipe, the faster things will move through it. Every square centimeter of surface area in that pipe actively resists even gases flowing through it, it is called friction. If long pipes sped things up, water treatment plants would not require lift stations every couple hundred meters. Natural gas companies wouldn't need pumps inline every few hundred meters to maintain even pressure throughout the system. The fact is that the gases never speed up, they slow down until they reach the end of the pipe. Put your hand at the end of your tail pipe, about a foot away. It isn't too hot, is it? It isn't a constant stream of gas, either is it? It is a warm series of puffs that come out of the tail pipe, because they have lost so much heat energy and speed that they only move because the engine spits more out constantly and there just isn't room in the pipe for all of it. John

"They do not grow, though, in a literal sense; they vibrate at higher and higher frequency" this is so correct. they vibrate and heat causes them to vibrate even more and over come the attraction and bonds betweent the molecules of the metal. this causes the cracks in the manifolds. as mentioned before, i dare not venture and comment the extraction of natural gas industry. but this constant heating and shuffling of metal molecules over time causes the cracking of heats. and as for friction within a manifold...this only seeks to further excite the molecules of gas.

The part you did not quote is where I said the increased molecular activity strengthens the bonds by making the shared electrons move even faster; making the overall material more resilient and maliable without breakage. The resonant frequency is what you are speak of, when molecules begin vibrating at the natural frequency of any given object. At that point, yes, the bonds break down. The piece at that point is more fragile than thin glass, and would shatter from the very harmonics of the engine running. Metal will never meet its resonant frequency due to heat. On the flip side, metal would generate its own heat at the resonant frequency; but again, as I have said the metal never ever reaches the temperature at wich it was formed, so the heat it encounters is not sufficient to cause its failure. There are far more complex laws of physics at work here. Again, the metal does not crack when it is hot, it cracks when it shrinks too rapidly. The gas molecules are not what are picking up the energy in the frictional coefficient of their interaction with the manifold primaries, so this would not be "exciting" them. Rather, the gas is what already has the energy, and is transfering it to the metal (this is why the metal gets hotter and hotter, not the gases). Friction may be enough of a factor to prevent the gas from cooling down completely, but it would only account for a fraction of a tenth of a degree to a gas. The friction is far more a factor in slowwing the gas down by the added drag than anything. If you have seen how primaries that are too big in diameter can hurt your torque output, you have whitnessed the principal of backpressure being affected by the amount of friction a pipe applies to what flows through it as well as available volumetric displacement. The gas is at its hottest and fastest in the sealed cylinder. It is all down hill from there. Molecular agitation does not spool turbos, either, gas pressure does. John

BTW, I drive a 2001 Nissan Frontier KingCab XE with power windows/door locks/remote keyless entry and side view mirrors, body color fender flares and front bumper cover (Goldrush color), 15" alloy wheels, sliding rear window, privacy glass, A/C, remote intermitten wipers, factory fog lights. I added custom window tint, vinyl graphics, cold air intake and custom heat shroud, Gibson cat-back exhaust, Jacob's ICE Pak ignition system, Nology Hotwires, and over gapped NGK plugs. My current projects on the 2.4L KA24DE include: Unorthodox racing pulley set, FAL electric fans to replace pulley driven fan, and electric water pump. I'm in the proccess of amassing the rest of the parts I will need to install my Turbonetics T3/T04B hybrid in Super-46 compressor mated to a ceramic ball bearing wet app., with stage II exhaust turbine in .63 A/R housing. I plan to run about 15psi, but could go as high as 19psi. I just need to drop my Xmas dough on forged guts, first. Initial math puts me at about 350hp at the wheels, on stock top end parts. John

Typically heat in that of itself is not the reason for cracking. Heat is a necessary evil needed to drive the turbo and an unavoidable by product of burning gas. Manifolds need to be designed with heat in mind. Tubular welded manifolds can be plenty strong as long as it is put together by a decent welder. The problems with cracking(and this goes for any kind of manifold) is in the flanges and the holes for the studs/bolts. Separating each flange helps to allow expansion of each runner without any undue stress. And the holes for the studs/bolts to the head should be progressively larger as you go farther from the center to allow for both expansion and avoiding sheering off the studs/bolts. The same concept can be applied when using different materials between the mani and the turbo flange. Bracing a mani is also not a good idea as the brace will not expand at the same rate as the tubes, which cause more stress as the tubes try to expand. Headers for NA cars are not subjected to as much heat so it doesn't need as much attention to these kind of details.

Here is an example of a well made tubular manifold. It's not equal length, but if you look closely, it is a direct replacement for the revhard manifold. Looks similar, but you'll notice it uses seperate flanges for each port and note the larger holes on the two outer flanges. Keep in mind the revhard mani has been known to crack if not prepped well. In fact, my used revhard mani came with a crack in what would be the collector area. I had it welded, and enlarged the bolt holes all around and have not had a crack since...

I’m currently making a mani that will actually make Atoms smack into each other or bang against each other! Ultimately causing 10,000HP or an nuclear explosion!!!!! :thinker

its becuase of this agitation that there exists pressure you cant have one without the other. rapid cooling causes metals to crack? well they wouldnt need to cool if there wasnt any heat. the effects of dealing with heat and reacting to it causes the manis to crack. the moelcules when excited more easier and that compunded with the vibration you mentioned causes the mani to crack. to say the effects of heat on a mani are not significant is a major oversight.

also i am the technoman...nice car.

A home built linear accelerator... I LIKE that idea!! Smashing atoms is the fun new way to waste a weekend, and a city suburb. Also, george, you are right. It would be a major oversight to release the importance of thermodynamics in designing an exhaust manifold, no matter the application. The properties of any given piece and how it deals with temperature is one of the fundamental issues in fabricating a quality piece. Designs that will not concentrate excessive heat in any one area, and also not cool any given area too quickly, are the primary concerns when addressing exactly how the mani will be constructed. Often times, space has less deciding factor over design than the simple physics of the piece and the material it is constructed of. Those kinds of projects are nightmares. John

yeah i had a few mani crack on me over the past year...i was trying to fabricate a equal lenght mani to spool up a t78 for my KA. it is a work in progress but when i get it up and running i will post some pictures and have you take a look so i could get your opinion, and everybody elses, on the project.

george wrote:also i am the technoman...nice car.

Thanks George!

For the last hour I've been reading through this entire thread. I only know one thing for sure. I need to take chemestry and physics all over again.

John, lets get back to the topic at hand. In your opinion, describe to me the best manifold design in your eyes.

I think HKS did a fine job on my Cast mani...once ported.

WD

Well, for any given application, this may be a bit general. I would start with making a map of all the critical tolerances of the space I had to work with. A beautiful and perfect mani sucks, if it won't go in place. That includes how the turbo bolts up, and the plumbing routes, down pipe, oil lines, water lines, etc., and anthing that will be in close proximity to the additional heat. Next, I would decide what kind of mani would serve these physical constraints best (i.e.: Equal length or log). Once I knew all that, I would pick my material. For a garage project, we'll assume casting is out of the question. Stainless or mild steel is what it would come down to, along with the wall thickness, and diameter is partially decided by the data accumulated previously, plus what the expected length of the primary will be and the actual displacement of the engine. You can engineer the mani from two ends: The collector and the primaries. A bit of both is likely neccissary to get the correct angle into the collector (Between 5-15 degrees) and to come away from the head cleanly. It is also important to have the primaries deliver their gases in a sequential manner, rather than delivering gases from primaries direclty across from one another (Like a distributor cap, in that form of rotational sequence) . Once I knew how I was going to run the primaries, I would construct a jig that would help me align the flanges and tubes. I would likely TIG weld the mani, but MIG is an option as well. Either way, the correct material must be chosen based upon the material being welded, and the surfaces must be cleaned and prepped for a strong weld, and the welds would be peened afterwards. once the mani had been completely welded and peened, I would Metalax it, then perhaps Magnaflux it to find any potential cracks around the welds. The flange could also be cut between primaries to allow for warpage. If I were going to ceramic coat it, I would do it now. Bolt everything up, torque everything down, plumb it, wet it, double check it. Break everything in, while tuning everything to run clean. Like I said, pretty general. I didn't even get into wastegates, there are really so many things to this. There are some good log mani's out there, my Syclone hasn't had a single problem yet, besides regular maintainence. I've had it since '91, and can still run real hard. No cracks either...John

george wrote:demcj,

lenght of the EL manifold effects gas velocities too. if the manifold is too long the gases accelerate to the speed of sound and create a sort of sonic boom within the manifold. this also contributes to the cracking of the mani and poor spool up of the turbo.

well, actually it's not the gasses themselves which accelerate to the speed of sound. due to the construction of the engine, timing of the valves, compression ratio, etc... the engine creates pulses, and depending on the length/volume of the chamber used to channel these pulses, resonant frequencies or standing wave patterns can arrise which can adversely effect the grain structure of the metal/weld.

240ofTerrorr wrote:well, actually it's not the gasses themselves which accelerate to the speed of sound. due to the construction of the engine, timing of the valves, compression ratio, etc... the engine creates pulses, and depending on the length/volume of the chamber used to channel these pulses, resonant frequencies or standing wave patterns can arrise which can adversely effect the grain structure of the metal/weld.

these particles which comprise the medium through which the standing wave patterns travel may possibly reach the speed of sound (which varies depending on temp and pressure) but need not necessarily reach that speed in their ocillation in order to create detrimental stresses on materials, it's the higher order harmonics of the standing wave pattern in relation to grain structure of the material in question.

johnthegreat what the hell do you do for a living lol?

i hope it involves using the knowledge you've demonstrated you have :pface

-Andre

ok i have just read a whole lot of stuff that i dont understand but here is my opinion , i build turbo manis and i would definitly choose an el mani any day than a log style , it dosent matter if your running 5 lbs or 20 lbs el manis flow way better and if you make them out of the right matirials they dont crack, i make mine out of 1-1/2 id tubing with 1/8 in wall thickness and ive yet to have a problem , im currently in the prosses or building a s13 el mani for a friend perhaps i will get some pics of the manis ive made

so thats basicly my point of veiw on the whole subject

good god. i completely forgot about this discussion.

imo, this thread needs to be deleted. half the error filled and pointless tech talk in here is more than enough confuse and mislead anyone who is actually trying to learn something.

the log vs. equal length thread in the forced induction forum is much more accurate and understandable.

-demetrius