Exhaust Cone.

[e.thirteen]

I was looking in the manual of my Firestorm when I saw the assembely of the exhaust (see below). I noticed inside there was a cone and ive read eleswere that the cone slightly lowers performance and noise.

Is this true, if so is it worth takeing out.

Thanks Guys!

[martin]

It will make it slightly louder im not to sure about the performance it should be less, from my understanding on tuned pipes you need a tappered cone to quickly funnel the exhaust gases out plus it also makes the exhaust pulse bounce back making any excess oil in the exaust to go back into the cylinder and re -burn/cool/lubricate the engine.

marty

[e.thirteen]

Wow speed reply there, Anyway, I thought the same. Why eles would they put it in there. Well someone will come along and clearify things up.

Thanks

[unknown666]

old thread, I know, but I thought I would answer this question.

Considering the engine is a 2 stroke, and all 2 strokes have the same basic principal, of exhaust pulses, as Martin mentioned.

The "cone", is usually refered to as the "bottle" or reverse cone/diffuser is used to reflect the exhaust pulse back into the engine, so removing it will lose you considerable performance and efficiency.

Key to diagram:

1 - Header pipe

2 - Diffuser

3 - Bottle/Cone

4 - Stinger

when the 2 stroke engine was created they originally didnt have expansion chamber exhausts.

This meant they were extremely unefficient, unreliable, and not very powerful.

The 2 stroke exhaust pulses were discovered and the exhausts were developed (by the german firm MZ if I am correct) to make use of these pulses and ensure they didnt lose strength.

The first exhausts originally consisted of just the diffuser, and then through more research and development they found that if the "bottle" was fitted, efficiency and power were increased considerably. This was the first expansion chamber exhaust. To ensure a good, strong reflected exhaust pulse, it was calculated that the "bottle" should have an angle around twice as large as the diffuser.

For example, if the diffuser at the header pipe is 35mm diameter and the other end is 125mm diameter, it has a 6.8 degree taper, so the "bottle" would have a taper of around 13 degrees.

Further research discovered that the engine characteristics could be altered by altering the "tuned length" giving the engine better low end or top end power for example.

Sounds complicated I know (it is!) but I hope that clears things up.

EDIT:

Firstly, If you didnt already find it, click the image for a bigger diagram.

Secondly, I know most of the 2 stroke development is based around petrol based race bikes, but its still the same technology in these cars, only smaller

Edited April 8, 2008 by unknown666

[Mr Terminator]

Removing it all depends on the engine whether or not it aids or hinders performance.The cone in the Genesis exhaust for instance,when removed gives a slight increase in power and smooths out the power band but the noise it makes is unreal,its an already noisy system and I put it back in after trying it.An expansion chamber works by increasing volumetric efficiency,the bottle or cone is also called the convergant section of the chamber and is placed just after the dwell section of the pipe.Removing it should'nt alter the wave dynamics that much to cause a power drop and just makes the dwell section volume bigger so more gas will be expelled on the second cycle,with only the same amount needed as from before the cone was removed.Personally,i'd leave it in,if it aint broke dont fix it....

[Gloplug]

My Savage came with it (the cone) out already (it was in a bag), and manual says fit if IF you find the noise too much...........thats all?????

Anyway, I want MORE noise, not less.......LOL

[Matt B]

Well Savages are noisy things. A mate had one with the ribbed pipe, and man that thing was noisy! I ended up getting shouted at by a disgruntled resident because I was running my car after, and he thought it was mine So i'm guessing they include it for people who run in more residential areas.