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I was just wondering how this header's design helps increase the hp and torque over the whole rpm band, this is quite a crazy looking header, and I can only assume the bends and curves somehow help increase the exhaust flow velocity and negate any type of reversion or backpressure, compared to the typical straight designs we see on most tuner cars which usually only help on one side of the curve or one specific range like mid range or highrange... Below is a pic of the header and dyno... Be nice to hear input from MD on this one :)



 

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Website info on this header:
http://www.prototyperacing.com/k20kit.htm

the design you see in the above image is from a CAD/CAM turbo exhaust manifold design in an attempt to obtain equal lengths through these tortuous loops. they are quite common in the turbo exhaust manifolds for spooling but John doesn't use this approach in his turbo manifold for Papadakis. The loop approach from turbo manifolds appears to be similar here in this N/A K20A header. The primaries pairing is a conventional non-sequential 1-4, 2-3 (midrange bias). That thing looks like a serpent's nest or a spaghetti factory. I wonder how it fits in an RSX instead of a Lotus Exige (clearance wise with the radiator and PS?)

Originally posted by Prototype Racing said:
As you can see in the photos of my new Prototype Racing stainless steel equal length 4-2-1 exhaust header for the Honda K20A in the Elise, it certainly isn't easy to build. An easier route would've been to design a shorter header that would make more top-end power, but a nice broad torque curve is more important, and that's what I designed this one to produce. I had to wait many months to finally get the proper radius bends with which to bring the image in my mind into reality. Previously I used the first section of the Japanese Type R exhaust header, and built onto it to get the proper overall length, but the tube size and rather short primaries were hurting torque production. Look at the new Dyno curves, and you'll see what I mean. I'm quite pleased with the way this "hot snake orgy" works, and even though it's extremely expensive to produce, it will be the standard exhaust header included in the K20A kit, and will bolt right up to your existing CAT or replacement pipe. We made substantial changes in ECU mapping for fuel and cam angle phasing to compliment the header design, and that mapping is available as part of the Hondata ECU upgrade, and immobiliser deletion.

Considering that we started with an engine rated by Honda at 220 HP @ 8,000 RPM (measured at the crankshaft), I think we've done quite well in broadening the torque curve substantially, and producing approximately 55 more HP at a lower RPM with no internal modification to the engine. This was accomplished using the standard Exige silencer, and running the engine on 91 Octane fuel. At this point I think we've come to the end of the first phase in the tuning of the K20A. The next phase will include new cams and reshaping the intake and exhaust ports to provide us with superior airflow. I'll concentrate my efforts on letting the engine breathe better before I start changing pistons, etc.


Other people try to obtain equal lengths with these extra loops in the primaries:

Bisimoto and ANR in other Hondas plus NRG's, Prospeed's and Erick's Racing B series header:






Prospeed's if you can't see it



NRG header

It seems to be the latest "craze" or fashion in header design. But does it do anything?

The thinking here is that equal length maintains flow speed for improved scavenging and the timing of the pulse arrival to the merge collector is simpler but when you throw in radius bends like that, you tend to generate more opportunity for turbulence since there is one part of the flow that has a shorter distance to travel than another portion (long radius vs. short radius). You have to wonder if the flow speed suffers in this attempt to equalize the lengths. I've always been told that flow doesn't like bends (especially sharp bends). Gentle bends are nicer on the energy or momentum of flow. Although radiuses look nice and even in cross section and smooth, it's those loops that can be a bit of a fly in the ointment.


The midrange gains may be more of a function of the primaries pairing and tri-Y layout than the snake's nest impersonation.

Certainly when you look at SMSP's or Hytech's race side exit headers, they don't achieve equal length using loops. They try to keep the primaries equal without adding extra sharp detour bends if they can. Even John's turbo manifold on Papadakis' Civic uses sequential pairing and no loops.
They let the diameter steps, secondaries length, and tri-Y maintain the midrange rather than doing this approach.

2 different schools of thought and approach.
 

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MD, add orig.jpg to that prospeed link, it says you are not authorized to view it. So would all those bends negate the gains that a header like John's would produce. I'm not quite sure how the bends would affect the powerband up top. Could you shed some more light on the subject?
 

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Looking at the bends, I too also assume why it wasn't just a simply short header. Then I recall discussions on why John and Dave's header are better. Their headers are longer than stock headers, meaning longer primaries and secondaries.

Take for example Hytech's Hybrid header. What happens if that header, even with the specs it has, was as short as a stock JDM 4-1 header? It probably wouldn't be so awesome.

My take at this particular header is that they are using all these extra bends for the extra length that the Hytech and SMSP has on their more popular headers.

Why all the bends though you still ask? Well because the K20 header in this Lotus is in the back. Therefore the exhaust exit is right where the header comes out of the car. It doesn't have the space that the Hytech and SMSP has to underneath the car and straight to go the back of the car.

Well, thats my take on it. If it works why argue with it!
 

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sak: Yes, the extra loop section adds more primary length to even them out (hence the term "equal length primaries"). But this is only at the primaries not the secondaries. The added length on the secondaries contribute to the torque curve rocking effect further, above the primary length's rocking effect. Having the same length for all 4 primaries has different separate effect than adding length to them (see the link I gave above in the "thinking behind equal length primaries" explanation sentence below the other header pics).

Hakamoto:

it's how you combine the diameters with the length assuming that we don't talk about primary pairing here.

Diameter is what determines top end. Length is what determines midrange (if we ignore pairing and collector design). Remember adding length does not move the peak torque like diameter changes. The peak torque remains at the same place. However, the torque curve is "tilted" in such a way that at the rpms below the peak, the torque is tilted upwards like the high end of a see saw with the peak being the fulcrum.

We can then turn to the steps in diameter and where they are located along the length of the header, as well as the merge collector design. These 2 other design factors also determine the flow energy that you get up top. We also know that sequential pairing gives you more kick up top over the traditional 1-4, 2-3 nonsequantial pairing.

The exhaust pulse leaves the head exhaust port at over the speed of sound (mach 1). Maintaining the momentum of the flow speed is the key for the top end stuff.

Obviously when the import world finally decides to catch up with the motorcycle world, we'll begin to see electronically controlled exhaust valves and not these primitive "want some backpressure all the time" manually controlled exhaust valves. This also will give you the same effect as the hybrid headers...2 powerbands (or more).

I think I said all of these things in the header tech article using Jim McFarland's lectures. At the highest levels of custom header design these "undergraduate" principles are modified and the rules/conventions are challenged. Dave was telling me that when he was developing that B20VTEC extra long hybrid header, they unexpectedly got more top end using an even longer secondary section (i.e. expecting to see more kick at the upshift rpm landing point which they got also). It may've been related to the bigger collector and diameter at the secondary though.

But if you want to read more about this sort of thing:

BTB Racing Exhausts in the UK used to have a nice write up on header theory summarized as well on their website by Joe Ellis.:

Original Author Joe Ellis said:
BTB Technical article on header design - Jan/01/02


The design of exhaust manifolds is governed by two basic principles. The first calls for the efficient extraction of exhaust gases from the cylinder after combustion. The second is the controlled development of a standing pressure wave in the manifold pipe to encourage over filling of the combustion chamber with inlet charge.


The first is the easiest to understand if we merely think of the engine as a pump. After the combustion stroke has taken place the piston has to return to top dead centre. As it returns, the hot exhaust gas has to be expelled past the open exhaust valve into the exhaust pipe. At this point the objective is the efficient expulsion of exhaust gas to allow the piston to return as quickly as possible. The pressure against the piston as it rises determines the speed of its movement, this is known as the pumping loss and is simply the work done by the piston against the exhaust gas. In order to minimise pumping losses, the flow of exhaust gas has to be maximised. This does not necessarily mean the largest diameter pipe. Because the gas travels as a fluid, too large a duct will lose gas velocity and the gas flow will stall, (imagine a small stream reaching a large lake, the energy of the flow is lost as the stream decides where to go, and silts up the lake).

Conversely, too small a duct will restrict the flow and increase the pressure (damming up our analogous stream). Determining the optimum size of the exhaust duct largely depends on the capacity of the engine, and the amount of revolutions per minute at which it is operating. Supercharged engines will need bigger exhaust pipes as they effectively have a greater capacity. We can determine the theoretical perfect size for the exhaust through a series of calculations. Ironically, in the most widely used formula, these calculations rely on us already knowing the theoretical perfect length. Also very important is the need for a smooth parallel-sided duct with the minimum number of bends on the largest possible bend radius, because hot exhaust gases do not like to change direction too abruptly. We must also avoid sudden changes in diameter or mismatched ports, and encourage smooth transitions where one pipe meets another. So, in summary, this aspect of exhaust design is essentially a fluid dynamics exercise and is usually heavily compromised by packaging restraints once an engine is mounted in the chassis.



The rather more scientific wave tuning aspect of exhaust manifold design requires us to understand standing waves. For an acoustical analogy consider the case of a pipe organ, where different notes are formed from blowing air across the open ended mouth of different diameters and lengths of tubes. If we consider the case of a single cylinder engine with a straight exhaust pipe exiting to atmosphere, the pulsing flow of gas causes a standing wave to be formed in the pipe. A standing wave is best illustrated by stretching a "Slinky" spring between two people, if one end is oscillated at a consistent frequency a clear pattern can be seen in the coils where bunching indicates a high pressure zone and stretching shows low pressure. We have already seen how important it is for an engine to be expelling gases into a low-pressure pipe, but for a high performance engine a standing wave can be especially beneficial. This is because at high rpm in a tuned engine both the inlet and exhaust valves are open at the same time as the piston approaches TDC to begin its inlet stroke. At this point if we can ensure that a low pressure zone exits just behind the exhaust valve, inlet charge can start to be drawn into the cylinder even before the piston starts to travel downwards on its "sucking cycle". This ram effect is crucial to the "over filling" of the cylinder prior to combustion that leads to increased engine power. Of course these days most engines have more than one cylinder and therefore the interaction of the ram effect between the cylinders is paramount. A typical formula for calculating lengths and therefore diameters is as written in A.Graham Bell's excellent book 4 stroke Performance Tuning in Theory and Practice, published by Haynes.

850 x ED
P= ---------------- - 3
rpm


Where P is primary pipe length in inches
ED is 180 + the number of degrees that the exhaust valve opens before bottom dead centre Rpm is the tuned engine speed in revolutions per minute.

This gives an excellent starting point to exhaust manifold design by suggesting a primary length for a theoretical 4-1 design. Using this we can then calculate the Inside Diameter of the primary using the formula:

cc

ID = S ----------------------- x 2.1


(P+3) x 25



Mr Bell goes on to suggest a way of calculating lengths for a 4-2-1 design. This relies on a theory that the length of the primary pipes for a 4-2-1 should always be 15 inches. Whilst again this may be a good starting point it is generalising too much to suggest that all 4-2-1 exhausts should have the same primary length. Over the years we have tried many alternatives to this with sometimes surprising results. The most popular capacity range for race engines in the UK is from 1300-2000cc and in this range almost always a 4-2-1 design has proved to be better than 4-1. It should however be emphasised that, long primaries of the length calculated for a 4-1 but subsequently merging into two short secondaries appear to give the top end performance of a 4-1, without the flat spot at low revs that a 4-1 usually has.


The best way to establish the exact optimum layout and dimension for a specific engine is by trial and error on an engine dyno. This gives the tuner ample opportunity to try many different iterations of length, diameter, collector design and tailpipe size. Not to be forgotten of course is the inlet tract, which also will generate a standing wave and its length including plenums, trumpets and butterflies has to be tuned in conjunction with the exhaust. It is clear that exhaust pipe length and diameter dimension will be a function of the quantity of exhaust gas that is being expelled and the length of time that it is being expelled (period of stroke). Hence a short stroke, big bore engine will require a shorter and larger diameter pipe than a longer stroke narrow bore one. Altering the design of the inlet and exhaust can have a dramatic effect on the characteristics of the engine and often just looking for one peak power figure at a specific rpm doesn't produce as competitive an engine as considering the performance across the whole usable power band of the engine. The successful engine designer's holy grail is to get the maximum area under the torque curve, as this will provide the most opportunity for accelerating the car for the longest period. This partly explains the emergence of quirky manifold designs where theoretically the wrong cylinders are linked together in the layout of the manifold. This seems particularly to be the case in highly tuned motorcycle engines where instead of linking cylinders 1 & 4, and 2 & 3 into a 4-2-1 design, pipes are paired 1 & 2, 3 & 4.

Although initially this would appear to be so that the pipes can sweep under or around the engine frame more easily, it also gives a more even spread of torque with less peakiness. This unusual design layout has also been favoured in Touring Cars, where (in common with motor bikes) traction is at a premium and therefore a nice progressive power delivery is more desirable than a peaky wheel spin inducing one.

If it is not possible to optimise the exhaust manifold design on the dyno, then it is a good idea to make the pipes with slip joints between the pipes and collectors, so that different lengths can be experimented with during testing. It may be found that on a track with a high proportion of long straights a shorter primary that will give more power at higher revs provides a quicker lap time. Equally, on a tight track or a hillclimb with a standing start, a longer primary will boost acceleration from low revs.



The reason that a 4-2-1 works better over a wide range of rpm's than a 4-1 is that each combination of pipes will work best at a specific rpm and therefore the more combinations that are available the more possible solutions arise. A current trend in Formula 1 is to have steps in diameter at certain lengths along the primary.

Again, each step will create a standing wave at its own rpm, and these steps can be made to magnify existing waveforms at certain revs. Whatever the design, the object is the same. Sudden steps in the primary will contradict my earlier smooth gas flow theory, but it has obviously proved itself to be a compromise that the designer is willing to make. High revving short stroke racing engines have a very short time available to fill the cylinder with air fuel mixture and as such rely on ram tuning from the combined effects of the inlet and exhaust tracts to achieve their high specific outputs.
 

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man...those are some sick header....and im assuming those header r for only race driven....cause it wouldn't fit on a daily driven teg...well..without some modifications to the front...but dang....
 

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thank you for that insight.

yes, the way Prototype chose to achieve equal lengths using loops is more to do with their available engine bay space in that mid-engined Lotus Exige. With our engines located in the front, we have more of a luxury to choose between the loop method or the longer gentler sloping method of equal length primaries.

Radiator, clutch, cold air intake, and power steering clearances may become an issue in the RSX.
 

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Thanks for that article MD. That actually broke it down into a language I could understand, or maybe I have learned something.
I see that the last header is paired 1-2 and 3-4, whereas the prototype racing k20a header is paired 1-4 and 2-3, how could that affect the powerband? I'm also interested in what SMSP has to say on the subject, does John from Hytech post on this board?
 

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Hakamoto on Feb/03/04 said:
I'm not quite sure how the bends would affect the powerband up top. Could you shed some more light on the subject?
draw 2 lines of a half circle in parallel.

if you look at these like the walls of a side view of that header's loop and that the exhaust flow is going from left to right, we can go from there.

let's make it simple...let's only consider 2 layers of flow travelling through this half moon tube.: an upper layer and a lower layer split by an imaginary line running down the middle.

the flow below this midline hugs the lower wall (lower line).

the flow above this midline hugs the top wall (upper line of your half moon).


if these flow layers are travelling at the same speed upon entering the tube on the left end, which one gets to the right end of the tube faster?

the lower line has a shorter overall distance to travel (short turn radius).

this difference in flow layer arriving at the end of the tube causes the layers to separate and therefore causes turbulence and will, in general, slow the flow speed down.

if top end power relies on maintaining flow speed and you've created separation in the 2 flow layers and turbulence with that bend, you just undid the advantages you got from using equal length primaries.

the sharper the bend or turn for the flow to make, the worse this problem becomes.

a tube with less of a bend or no bend would not have this issue.
 

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MichaelDelaney on Feb/03/04 said:
yes, the way Prototype chose to achieve equal lengths using loops is more to do with their available engine bay space in that mid-engined Lotus Exige. With our engines located in the front, we have more of a luxury to choose between the loop method or the longer gentler sloping method of equal length primaries.
How so? on the K20 engines, the exhause manifold is on the back side of the engine, not the front as in the B series. So it only has the space between the back of the engine and the firewall, and is further constricted by the subframe, steering rack, etc.
 

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one thing that always comes to mind for me when thinking about header design now is this thread (titled "Header tube direction?") where Dave (SMSP) makes some interesting contributions.

A quick cliff notes: Bends in a header can slow down velocity of the exhaust gasses b/c the gasses cool as they maneuver the bends. cooler gasses move slower than hotter gasses.

Header wraps don't just keep your engine bay cooler, but keep the exhaust gasses hotter.
 
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