looking at all these head pipe........

[andiboy123]

Looking at all aftermarket head pipes I notice that the curve getting out of the engine is like the stock one, others growing in sections but getting almost the same diameter of the stock one. Also many companies they promote only the slip on for the DS. Is there is any different between the stock head pipe and the aftermarket one? Why the only promote the head pipe as a mod instead of the complete set up like others atv’s?

[SilverBomb]

I know of one Dyno test done by Mr. Horsepower where he tested a full FMF pipe against the slip on FMF on a DS450. He said that with the full pipe it lost 1.5hp. LOL! So yeah, the stock head pipe is a good design and doesn't really need to be replaced until someone can prove that their aftermarket one performs better.

[TNT]

Exhaust pipe design is a complex balancing act between pressure waves and gasses making it next to impossible to look at a pipe and tell how effective it will perform on your quad. Dyno results and track testing are your best source.

There are many ideas about header pipe sizing. Usually the primary pipe sizing is related to exhaust valve and port size. Header pipe length is dependent on wave tuning (or lack of it). Typically, longer pipes tune for lower r.p.m. power and the shorter pipes favor high r.p.m. power.

Gas speed is a double edged sword as well, too much gas speed indicates 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 hurting low end torque.

The collector can is dependent on the cylinder, the engine configuration, firing order and the basic design objectives. The collector outlet size is determined by primary pipe size and exhaust cam timing, thats why full systems usually work best.

[X400EX]

Originally posted by TNT
Exhaust pipe design is a complex balancing act between pressure waves and gasses making it next to impossible to look at a pipe and tell how effective it will perform on your quad. Dyno results and track testing are your best source.

There are many ideas about header pipe sizing. Usually the primary pipe sizing is related to exhaust valve and port size. Header pipe length is dependent on wave tuning (or lack of it). Typically, longer pipes tune for lower r.p.m. power and the shorter pipes favor high r.p.m. power.

Gas speed is a double edged sword as well, too much gas speed indicates 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 hurting low end torque.

The collector can is dependent on the cylinder, the engine configuration, firing order and the basic design objectives. The collector outlet size is determined by primary pipe size and exhaust cam timing, thats why full systems usually work best.

I've learned a lot from reading this Terry... Thanks!