ае чаткам малко инглиш ама технологичните термини не ги знам...някои ако ми преведе това много ще го обичам или пък поне най важните неща които трябва да знам,със сигурност и на други колеги ще е от полза

"The ex valve throat on the std TC with typically a 36mm valve - is about 33mm, ie; about 1.3 in. The throat is the control diameter for the flow to the port. The throat should not underflow the port and vice-versa, and conversely there is no point in having a port that outflows the flow thru the throat - either the bare throat itself or with the exhaust valve on full lift.For the size of exhaust primary pipes on 4-1 or 4-2-1 I tend to use the next-up available metric size pipe, 35-40mm, ie: larger than the valve throat. The ex port flow on the TC is huge, easily 75% ex/in flow ratio, actually way bigger than needed, and its section varies along the length from valve throat to port exit, the most restrictive region being around the guides. I have never run bigger than equivalent diameter of 35mm in any section Â¢â^šÂ¬Ã...â^œ and that was probably overkill.I take the view that the primary pipe should be of the same size as the valve throat or larger, the theory being that if is the same diameter the velocity will be constant thru the valve throat and primaries, and if the primaries are larger dia the step betw the port and the primary pipe will help to prevent reverse flow of exhaust at lower engine speeds and gas velocities.I have dyno results confirming my assumptions of primaries sized to match the valve throat (which of course depends on the work done on the valve seat, mine come out at about 33mm on a 36mm valve), but not the latter, which is GC experience supported by tests and theories carried out/proposed by others. In support of the latter, I have however had success with primary pipes up to 10mm bigger on diameter than the valve throat, (ie 43mm dia) GC NHRA engines being a principal example, though whether the larger pipes were contributory to the success of the test results or not I cannot quantify, but certainly they were not detrimental. Conversely I have not seen any diminution of power output from the smaller primaries either, though I would no go so far as to say that reducing them below valve throat diameter would be a good thing.If the exhaust manifold (header) is a 4-1 (for a 4 cyl engine) then I would run equal length primary pipes to a secondary pipe downstream of the collector and use a secondary pipe of 35-43 x 25% dia ie 44mm - 54mm, generally preferring 50mm ID as a conveniently available pipe size. I have dynoed exhaust systems with these sizes and found no detrimental effects. If the manifold is a 4-2-1 I would go for secondaries of 25% larger than the primary and keep the same diameter for the exit pipe downstream of the secondaries. In my exp there is no such thing as a perfect diameter for the pipework described above, only a tolerance zone with limits roughly in accord with those I have described. If the pipework is extended in diameter beyond those limits it is my view that the gas speed will drop and the total pipe pressure will rise, with resulting performance loss, conversely if the diameters are reduced too much the gasflow velocity will rise and may choke, ie stall. Most engine tuners err on the side of caution and rely on larger pipework, though extremes of diameter are risky.As to whether 4-1 or 4-2-1 is preferable on a 4 cylinder engine, the simple answer is that the sum of the lengths of the primary and secondary pipes on 4-2-1 Â¢â^šÂ¬Ã...â^œ fully optimised for a given engine Â¢â^šÂ¬Ã...â^œ would usually be the same as the length of the primary pipe on an equivalent 4-1, though recent testing on GC units indicates that 4-2-1 tends to give better area under the rpm/torque curve than 4-1. Matching of the lengths of the pipes with either is really quite critical, you should aim for accurate matching of pipe chord (centreline) length to within 1cm.The performance (area under the torque curve) of an engine, ignoring mechanical losses, depends entirely how well the whole engine spec is integrated. The camshaft is just an opening device. Here are some of the main parameters that determine power:- Exhaust port and manifold length, diameter and manifold configuration (4-1 or 4-2-1)- Inlet port and manifold length, diameter and rampipe length, rampipe design.- Head flows - inlet and exhaust Â¢â^šÂ¬Ã...â^œ encompassing valve size and discharge coefficient, port shape and size, combustion chamber shrouding- Cam profile (lift by degrees) and camshaft timing (ie: FL posn)- Bore and stroke- Compression ratio- Ex silencer back pressureAs far as back pressure is concerned (static pressure in the pipe) the less the better. Production systems, if pressured measured betw last pipe junction and silencers (mufflers) at each point will exhibit variously 3.5-7 static pressure at idle measured on an ordinary gauge. (This is a beneficial test and should a necessary part of the optimisation of any performance engine). Back pressure goes up with rom and load and has nothing to do with exhaust pressure waves that travel thru the gas at subsonic velocities. It is the pressure waves travelling back and forth at negative and positive pressure that determine how much torque the engine will have, every engine has its own signature, dips and peaks in the torque-rpm curve that show if things are happening at the right time Â¢â^šÂ¬Ã...â^œ no engine has a perfect torque curve, there are always loss regions at certain engine speeds Â¢â^šÂ¬Ã...â^œ and no amount of tweaking of the ignition and fuel system will eliminate them.The static pressure at the port exit is the same as the cylinder pressure is when the exhaust valve opens, depending on the valve timing 15psi or more, and it drops progressively along the exhaust pipework to vent to atmospheric at, well - atmospheric pressure. Manufacturers put restrictions (decreases of diameter or tortuous circuits) into the layout of commercial silencers to deaden unpleasant frequencies and amplitudes of pressure waves from combustion and also the highly intrusive ’white noise (from non-combustion associated sources of noise (valve clatter, piston slap, bearing noise etc), which have the effect of increasing pipe pressure betw restrictions, ie silencers.Every increase in this so-called ’back pressure’ tends to prevent the cylinders from evacuating freely and from the performance point of view this is a definitely a bad thing. Race systems usually run 0-2.5 psi idle back pressure, whereas an F1 exhaust will run zero - and a UK circuit race-legal system might run about 3 max and just slip thru noise regs under say, a 103dBA limit. Even the latter though, might be too loud for road use in certain regions. Normally aspirated engines need about twice the silencing of turbo units Â¢â^šÂ¬Ã...â^œ in the latter the turbine damps out most of the noise.The only circumstance where back pressure is a good thing is in turbo applications where high back pressure betw ex valve and turbocharger leads to better turbine response."

**ici** · 06.05.2009, 13:26

Re: 4-2-1 аспухова система ???

NIKI_TIPO написа:

4-2-1 аспухова система ???кой каквото знае да каже че много се интересувам,искам за типто ми 1.8 8V да си направя но ми трябва инфо отностно цялата работа

то не е ли 4-2-1 заводски с чугунена отливка на 4 в 2-то и оттам с тръби ?

**vasilaki87** · 18.03.2011, 09:40

Пичове, искам само да попитам - при преминаване в тази система 4-2-1 - треа да се смени и оригоналния колектор, който е за преход към 1 тръба или става да се преправя, или си трябва нов, че нещо не мога да схвана замисъла как точно би трябвало да стане. Мерси предварително

**pecata** · 18.03.2011, 17:47

Колега изровил си много стара тема.Колкото до въпроса ти-трябва нов да се прави.

**Valiosport** · 19.03.2011, 02:34

Тамън се чудех дали Ники не е взел пак някое типо, защото той отдавна е с BMW :D

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