mokompri

this is the one im talking about, a well known exhaust shop in melbourne sells them http://www.junblusa.com/ EDIT: any of you RB boys run fujitsubo ? the SR crowd seems to have praise for them

unsprung mass ?! dont think soo..

after all that, you have only explained how sound travels, not how power is lost. power loss in the exhaust occurs when there is a restriction to flow. so, given a muffler with the same length of perforated internal tubing, one with an outside body diameter of 7" and one with 10", can you explain how backpressure is more in the 10" bodied muffler ? EDIT: on the topic of things, anyone used the JunBL mufflers ? not japan JUN, the US company

the major problem is that this sort of crap influences public opinion and perceptions. imo its bordering propaganda

thats interesting, what the hell is done to this GTR to overtake a F40 & F50 ? unless the ferraris had noobs behind the wheels. i saw that thing, it looks like an F1 car - well closest road car to it... love it ! although if a 4wd crashes into you, theres a good chance of getting mangled for the topic, all you need to do is test drive your options, and that will decide it for you !

yeah i did the same, drove a sil and a r33... but decided on the sil :D

could you elaborate on that? roy, science is for cool people :sorcerer:

straight from wiki: that probably explains why iconel is used. F1 being F1, they would have taken insulation to the extreme if there was any gain to be had imo. btw there is no pic in your post no no you have me all wrong, re read what i said i said its not worthwhile retaining heat from the dump pipe onwards. certainly as i said, you want a high pressure sparse gas with as much heat as possible in the exhaust manifold and in the turbine housing, and a denser cooler gas from the dump pipe onwards. this gives the greatest pressure differential pressure across the turbine, which gives it its power. like i said, energy retention in the exhaust manifold and turbine housing is good, because it still has work to do (spin the turbine), but once it hits the dump pipe its a matter of just expelling energy and matter as quick as possible.

i looked at a few pictures of F1 engines and its obvious that they have no coating at all, nothing better then visual evidence. most notably on the renault and toyota engines are pics that i found. the thing with F1 is, if its a worthwhile modification, ALL the teams will run it, so i dont see any reason some may run it and people like renault and toyota wouldnt (couldnt find any pics of new f1 engines running a coating). nice website and ive noted a few interesting points from it. the company says they are involved in F1, but dont mention any specifics/teams, for all we know it could have been a test run in the 70's. heres a quote on their website (press release/plug section) from someone in le'mans who ran it on a judd engine, this is what they had to say thats it. note it doesnt mention any increase in power at all, simply a reliability mod.heres another quote from someone who used their stuff: again there is no mention of an increase in power, but rather a faster spool which would be indicative that it was used on the exhaust manifold and turbine housing, areas where retaining energy is a good idea - and then again alluding to under bonnet temps. and then another quote from their website: no mention about power increase, or exhaust flow. then the only tech data, or anything closely related to numbers backing some performance increase is this: relating only to under bonnet temps. infact the only thing they mention about there exhausts having some good effect directly for exhaust flow are these 2 quotes: some real technical stuff there ! somehow gas velocity is directly related to engine efficiency ?! and then somehow we have a 'supercharging effect' by retaining energy in spent gasses, then they falsely claim increases in gas velocity - where physics dictates they will mearly be able to maintain velocities. all in all, it looks to me like another company just trying to push their product with vague claims and supposed relations with motorsports, and why wouldnt they ? actually you never alluded to black body radiation at all, and rightly so as its not really applicable here. you alluded to viscosity and incorrectly put it in the context of gasses, where it only exists in fluids. the discussion basicly came down to 2 factors, the loss of heat in the gasses meant we ended up with a denser gas which means a pipe of a certain diameter will flow more mass because its denser. the downside and other side of the coin was, that with the loss of heat the gas loses energy and velocity, which is also true. so then it was a toss up as to which of these effects was more beneficial. and since then i put some numbers together from the common gas laws, and found that a denser gas is more favourable to a faster gas in terms of flow capacity. heres the data that show this; the kelvin temperature is directly proportional to the kinetic energy of a gas. so that means with the temperature halved, the kinetic energy is also halved. now the speed of the gas/molecule is related to its kinetic energy or temperature, but not proportionally. kinetic energy = speed^2 or speed = kinetic energy^0.5. not needing absolute numbers, we will use relative ones and apply 100 as the kinetic energy: speed = kinetic energy^0.5 10 = 100^0.5 now we halve the temp/kinetic energy and we get: ~7 = 50^0.5 so by halving the temp (K) of the gas, we have gone from a speed of 10 to 7, 30% loss in speed/flow. then we consider the density argument, these are the common gas laws: V = kT P = kT V = volume P = pressure T = temperature k = a constant of proportionality what this tells you is, that halving the temperature of the gas halves the volume it takes up. which means you have doubled the pipes flow capability. which also means, it outweighs the loss of speed the gas has incurred. plug any numbers in the equations and the denser gas will always be ahead in terms of flow. what you say about combustion chambers doesnt apply here either, its a part of the engine which benefits from energy retention as it still has use for it, much like retaining energy/heat in the exhaust manifold and turbine housing is beneficial. the exhaust is all about expulsion of energy. EDIT: here are the sources i used for the gas laws etc http://id.mind.net/~zona/mstm/physics/mech...emperature.html http://www.answers.com/topic/gas-laws

manual turbo s15 200sx's, australian and jdm versions both have 480cc injectors (less depending on quoted fuel rail pressure).

that may be true about light load, but at the same time under light load and no boost the temps out of the compressor will be ALOT lower to begin with. so you have to wonder again if there is anything to be gained. ceramic coating of say the turbine housing and exh. manifold will be beneficial because you want to retain energy, not expel it - which is what you want to do once you get to the dump pipe. the reason why manufacturers do it, is either to stop rust or keep engine bay temps down - with the latter being important to stop ancillaries melting in the engine bay, its not a performance thing. rev210 once mentioned i should look at motorsport and note that its used (heat wrapping, ceramic coating), and therefore must be beneficial to performance.. i look at the pinnacle of motorsport - F1, and i dont see it.

i have some disagreements with what you have written in that post. you have noted that narrower pipes have less turbulent airflow then a larger one for low amounts of airflow. while this is true, and it has to do with gas velocities, more turbulent airflow doesnt necessarily mean more backpressure as you have stated. another member in that post also noted that a high velocity exhaust system is desirable. the misconception here is that gas speed is desirable, where it is infact a side affect of other factors. laminar flow occurs when there is enough gas speed in a given pipe. for example 100cfm through a 2" pipe might give turbulent flow, but when we reach say 200cfm flow for the same 2" pipe it may give us laminar flow. this increase in mass of gas (keeping temp variable constant) going through the same pipe increases the gas velocities, and the reason for the increase of velocities is because of pressure buildup within the pipe, and this pressure buildup is back pressure. if we increase the pipe to 3" and pump the same 200cfm through the pipe, gas velocities will decrease, which means less pressure build up, and less backpressure - and at the same time the flow may be turbulent again as its slower moving. this is why the bigger is better applies to turbo cars for less backpressure and if you want minimum backpressure for NA's - gas dynamics dont change, you still go for bigger. but of course if your not getting any backpressure at 2.5", increasing to 3" wont do anything for you. that instance of turbulent flow is not an issue, its mearly a side affect. turbulence becomes a problem when it exists in parts of a laminar flowing system. for example you have a 2" pipe flowing 200cfm in a laminar fashion, the pipe has a flap inside it half way down the pipe. this flap is an obstruction to flow and causes turbulence around that area. the introduction of turbulence in laminar flow is what causes a loss of flow, not when the flow is turbulent simply because of a lack of gas speed.

now this is a more suitable attribute to someone thats a 'serious engine builder'

i agree with scathing on this one. its not about backpressure, backpressure by definition is a restriction and causes a loss of power. pulse tuning is a timing thing, you dont aim for backpressure, but it might be an unfortunate result of having extractors with the best scavenging affect, that will give more power overall. after the extractors the less backpressure the better. 2 strokes do need it, but who cares about 2 stroke edit: with 2 strokes, i think its important to remember that its a secondary effect of backpressure which gives more power, not a primary effect. the secondary effect being that the backpressure stops the air/fuel charge from blowing straight through the chamber. if the charge didnt blow through from a lack of backpressure, and we took away the backpressure, power would increase. (ala 4 stroke)

what pump have you got ? its possible that the pump is running out of flow in the top end, so your getting a fuel pressure drop because of that, and the tuner is trying to compensate with high duty cycle on the injectors

im in the opinion that wrapping the cold side is a fruitless idea, the speed at which air travels through there means it wont aborb enough heat for any measurable temperature change. there was a thread where SK had some experience with this and had some numbers to back it up. im also in the opinion that wrapping anything after the turbine, dump pipe onwards, does nothing for power, unless its to stop heat soak under the bonnet - it doesnt help with exhaust flow, if anything its a step backwards imo

physics i agree, but murphys law is philosophy - i dont think it belongs here. murphys law is something thats used when shit happens and the real problem cant be explained, but i believe theres a reason for everything. friction on the threads should always be around the same, as your supposed to oil the bolts and the holes so that variation doesnt occur, and all those other variables stay the same anyways (size, pitch etc). the temperature variation you get in aus is probably around 20 degrees celcius through the year, hardly something that will have much affect in the process. in my engine i had the snapped bolt removed, and replaced with a new one. the engine ran thousands of km's after that, then i sold the car. but anyways, with all that you have said it practically puts the cause of inconsistency here to murphys law, which doesnt really say much at all does it

lets stop for a second and see what your saying implies. "if you do enough cam changes you are likely to break some", now this begs the question... what about the ones that didnt break ?? why DIDNT they break ? and so what seperated them, from the ones that broke ? if the problem is not with the installation, then it goes back to being the product, and i dont think a company like hks will have random quality control of their camshafts. if nissans torqueing procedure isnt sufficient, then a "serious engine builder" should know better. either from experience (which the workshop in this topic claims to having), or knowledge. and as for replacing new bolts, i dont see how this will affect breaking the cam, if the bolt is too fatigued/stretched to be reused, and is used, then it will snap/shear. it should not have any bearing on the breakage of the cam. i know this, because i snapped a bolt when i did my cam change

this sounds pretty ridiculous, so your saying unless you have broken a cam whilst installing them your not a serious engine builder ?? if the torqueing procedure and order isnt followed correctly sure they will break, but thats because your either being lazy or dont know what your doing, i dont see how this makes you better/smarter somehow ?! with that sort of logic, im finding it hard to understand what exactly went wrong in this case...

what you say is true, but when put it into context theres other things to consider. the difference in temps between a front mount and a standarm IC will vary depending on the amount of airflow. the more airflow, the greater the difference, and for low amounts of airflow the difference is probably marginal at best. for example at 5psi, i dont think you will have any measurable difference in temps between a standard IC and a FMIC, they both have enough capacity to bring temps down to almost ambient. so when we start talking about lag, where talking about going from vacuum, then going through boost build up stage, then peaking and staying at the max predetermined boost. and from the point of vacuum to relatively low amounts of boost, we are pumping low amounts airflow which probably wont show much difference between the 2 ic's, so you dont get that affect of cooler air>more exhaust flow>boost sooner, although it may shoot up from 'low' boost to your max boost a bit quicker, but we dont really consider that area when we talk about response/lag. ive seen a few dyno graphs of cars running stock boost, switching to fmic's and running that same stock boost without showing any real measurable difference. although this doesnt take into account high amounts of heat soak in standard ic's.

not sure about the ones sold for rb's, but the sr20 ones are definately single pintle unless they recently changed (i just did a quick search on the silvia forums)

what BHD said, just another pathetic workshop not taking responsibility whats more common, workshops passing the buck, or HKS cams failing

correct. easy way to check is, 370cc's are purple coloured, 480cc's are red coloured. as for the sards i beleive they are single pintle and dont atomise fuel as well as the nismos which are 4 pintle, so im led to believe edit: not sure about rb's, although they are also side feed.. but sr20's require collars to fit sards into stock rail

this is where a lighter tailshaft has some advantages over a lightened flywheel. on gear change when you pop it into neutral, with a lightened flywheel revs will drop faster relative to a heavier flywheel as there is less inertial mass attached to the engine, but the tailshaft is no longer part of this inertial mass because its after the clutch and its now disconnected from the engine, so between gear changes it will not cause a faster drop in revs. the same effect occurs with lighter wheels, its inertial mass after the clutch. its too bad the lightened flywheel is the cheapest option !

yeap SK's example is a case of diminishing returns. maybe he changed alot of things for CF replacements, which is very costly indeed, who knows. one of the 1 tonne examples i read about was actually on a US 240sx site which had a sr20 swap, and was pretty damn bare, but still street registered, engine bay was bare minimum too. as for being streetable, well thats opinion. for me personally at that weight, no its not, but that just depends on the person and what they want out of their street car. some will argue that as long as it has a drivers seat and is street registered, then its streetable if i had 2 cars then i wouldnt care about taking one to the bare bones for the ultimate driving experience. 290rwkw with the lag of a gt2530 and no increase in fuel consumption sounds pretty damn good but in any case even if you lose 100 kilos, which isnt hard in a silvia, you will still have a much better 'performance' package. EDIT: that n/a silvia isnt dumhed is it ? last i read from him his car was UNDER 1 tonne !