Ive got a bud that is talking to several different companys about pipes. One told him the pipe along would give him 15hp. I said that was crazy and another said 7hp. These were very well know companys. I know there are plenty of dyno guys and pipe builders among the DS comunnity so give me your input. Also one company said a 4stroke pipe wont perform without back pressure. How does a drag pipe have back pressure. Someone explain a pipe with a silencer and drag pipe. How cant a drag pipe be better. Just wondering as i dont understand the whole pipe story. Thanks

 

All I know is I changed my straight megaphone pipe for a pipe with a silencer and spark arrestor and gained 7 HP on the dyno.

Oh yeah, its much quieter also.....

 

15hp from a pipe - that is insanely hillarious! no point in even having a conversation with anybody who makes such a claim, just hang up the phone man.

one thing about company claims on HP - they never say WHERE the extra HP is made. most pipes out there will give you 7 or 8 HP gain - in the low range! most pipes for the DS give only a few ponies peek, some not even that, and I'm talking about on a stock motor mind you, but I'll not state opinions or numbers because that would be setting myself up bigtime for the guys that think 15HP is some kind of insane reality.

and then there are those that talk about how much they gained going from one pipe to another, without knowing if the carb was tuned properly for either one. that always a riot.

but these are just my opinions, what do I know - i'm not in marketing!

 

I agree, that number is way out of proportion even with the biggest and best exhaust companies.
If that were the case no other pipe would be sold and that manufacturer would corner the market with some secret that no one else knows. Sounds like they just wanted your money....

 

when i put my ugly dual drag pipes on i could tell a huge difference it made some killer torque and just keeps on pulling

 

On my pics page is a dyno chart comparing the full Woods pipe to my homemade end cap. This is dyno tuned for both. The mods at the time were an 11.5 old style woods piston, woods cdi and intake, tm45 on gas,web 110 cams, 40-32 valves in a ported head. With snorkle, no air box.

 

Thats an interesting chart.

 

Good stuff

 

MrMeaner the best pipe is and always will be an open pipe. But, and this is a big but, like an intake system, the pipe has to be sized in diameter and length to other systems on your engine. Sizing a pipe is very difficult. Not only that, but if you change one system, carb for example, the whole pipe you just built goes out the window.

Contrary to popular belief, you want NO backpressure. None, nada. In fact you want quite the oppsite, you want a scavenge effect on the exhaust. This is very difficult to do in a lot of RPM ranges. Just like the intake side, it is very hard to make work in a wide RPM range. That is why you want a 4 into 1 on both sides of the engine if you have a V8 or a 2 into one if you have a two cylinder. Merge collectors are very popular in the cars we race. They work great but are very difficult to manufacture and are therefor big $$$'s. If you have a good scavenging pipe you can close up the exhaust side of the cam and open up the length of the open time of the intake on the cam.

The best system would be something that would suck (scavenge) the exhaust out. This is what a merge collector does in a small way. It pulls a venturi effect on the pipe. Samething with a 3 stage pipe. These are all tricks to keep the velosity up with a low restriction.
If you go to a huge pipe you will loose power on the bottom end because you loose the velosity to pull the exhaust out.
You can see why there is no one pipe for all riding conditions. It's hard to make the perfect pipe for even one condition.

 

I amazed how many of the manufacturers talk about back pressure. They told my bud that drag pipes dont work on a 4 stroke. All the fast 4 strokes Ive seen run drag pipes. Its a little confusing to me. I also noticed the manufacturers that state that usually dont make a drag pipe. HMMMMMMMMMMMMM