Sil Motor Headers

[Saint aka ML]

Sil Motor Spaghetti Header Pipes are they worth it on a m900. Is there a cheaper alternative as 600GBP for fancy headers seems a bit much.

Any alternatives with similar results and less dosh.

[Pedro]

Got em on the 1000

[Saint aka ML]

Ok so only bling factor?

what do they do?

[Saint aka ML]

Originally Posted by rac3r

what do they do?

Apparently due to better, even gas flow can give more bhp and better torque/throttle response. However do not know anyone who had that tested?

For now it is only bling factor.

[Kato]

On a very well sorted 900 they are worth around 6hp on a standard or mild tuned 900 they actually loose some bottom end torque and hp it comes back right at the top end as long as your cam timing is spot on, so deffo bling factor only unless you are spending a considerable sum on the rest of the motor.

[Saint aka ML]

Kato knows.

So for me mainly a bling factor, AKA I will wait for it to show up on ebay one day as bargain

Get the autosol out on your standard pipes and they'll come out just like that! although they won't have the spaghettiness

[Saint aka ML]

Originally Posted by rac3r

Get the autosol out on your standard pipes and they'll come out just like that! although they won't have the spaghettiness

If anything then black ceramic coating but I was mainly asking the spaghettiness.

not as spagetified as the termi alternative ~:?

[Kato]

While we are on the subject how about a bit of theory,

As the piston approaches top dead center, the spark plug fires igniting a fireball just as the piston rocks over into the power stroke. The piston transfers the energy of the expanding gases to the crankshaft as the exhaust valve starts to open in the last part of the power stroke. The gas pressure is still high (70 to 90 p.s.i.) causing a rapid escape of the gases (blowdown). A pressure wave is generated as the valve continues to open. Gases can flow at an average speed of over 350 ft/sec, but the pressure wave travels at the speed of sound (and is dependent on gas temperature).

Expanding exhaust gases rush into the port and down the primary header pipe. At the end of the pipe, the gases and waves converge at the collector. In the collector, the gases expand quickly as the waves propagate into all of the available orifices including the other primary tubes. The gases and some of the wave energy flow into the collector outlet and out the tail pipe.

Based on the above visualization, two basic phenomenon are at work in the exhaust system: gas particle movement and pressure wave activity.

The absolute pressure differential between the cylinder and the atmosphere determines gas particle speed. As the gases travel down the pipe and expand, the speed decreases. The pressure waves, on the other hand, base their speed on the speed of sound. While the wave speed also decreases as they travel down the pipe due to gas cooling, the speed will increase again as the wave is reflected back up the pipe towards the cylinder. At all times, the speed of the wave action is much greater than the speed of the gas particles.

Waves behave much differently than gas particles when a junction is encountered in the pipe. When two or more pipes come together, as in a collector or spagetti junction for example, the waves travel into all of the available pipes - backwards as well as forwards. Waves are also reflected back up the original pipe, but with a negative pressure. The strength of the wave reflection is based on the area change compared to the area of the originating pipe.

This reflecting, negative pulse energy is the basis of wave action tuning. The basic idea is to time the negative wave pulse reflection to coincide with the period of overlap - this low pressure helps to pull in a fresh intake charge as the intake valve is opening and helps to remove the residual exhaust gases before the exhaust valve closes (scavenging). Typically this phenomenon is controlled by the length of the primary header pipe.

Due to the 'critical timing' aspect of this tuning technique, there may be parts of the power curve where more harm than good is done.

Gas speed is a double edged sword as well, too much gas speed indicates that that the system may be too restrictive hurting top end power, while too little gas speed tends to make the power curve excessively 'peaky' hurting low end torque. Larger diameter tubes allow the gases to expand; this cools the gases, slowing down both the gases and the waves.

Exhaust system design is a balancing act between all of these complex events and their timing. Even with the best compromise of exhaust pipe diameter and length, the collector outlet sizing can make or break the best design. The bottom line on any exhaust system design is to create the best, most useful power curve.

All theory aside, the final judgement is how the engine likes the exhaust tuning on the dyno and or the track.

Still want some flash pipes Luca

Right back to work !!!!

[Pedro]

Originally Posted by Saint aka ML

Ok so only bling factor?

Wouldn't say that quite, my 1000 makes 100 brake at the wheel

Kato - I am in awe of your posts, A mine of information or a fountain of knowledge, whatever it is - you've got it - respect is due etc - Mark.

is that 2 stroke theory ?

[Saint aka ML]

Kato i just read it now like 20 to 1am. Did not get most of it except that you did not reply to my question just suggested get one and get it on dyno