American Race Headers down pipe LFX engine

[TravisLBoston]

I'm having a problem with the pypes mid muffler cat back system and down pipes, I have been too a couple exhaust shops and have figured out the problem! The said problem is called kick back?!? The shop says it is because my exhaust flow is to open allowing too much free flow and vibrating the mufflers from the inside. They said I need to put the cats back on to create more back pressure to eliminate the unwanted sound. I have also read that there is a possibility of tuning this out any input? I don't want to put the cats back on and was wondering if anyone knows of a way to create more back pressure without using the cats maybe special mufflers or resonators, or if anyone knows how to tune this out if that is actually possible.

[DSX_Camaro]

... What problem are you having the with exhaust system in the first place? Start there. That wasn't clearly stated other than what the exhaust shop told you.

[45thCamaro]

Not that I'm saying this to compare the two, but I put on an aftermarket exhaust on my bike years ago. The new pipes are just pipes, no baffles and when I wrote it for the first time I felt a power loss in the acceleration. When I researched it, I found something about how the bike doesn't have backpressure giving it more power this the loss of said power

[TravisLBoston]

Problem is as follows; loud metallic rattle noise from inside mufflers.
Exhaust is as previously stated; Pypes mid muffle cat back exhaust with ARH down pipes cat delete

[BigRedViking]

Remove the muffler! MagnaFlow makes some decent mufflers that usually have a deeper tone.

[TravisLBoston]

Is there anything I can put on before the x pipe that would increase back pressure? Or am I better off with putting the cats back on and calling it a day?

[PolynesianPowerhouse]

If the exhaust is done right...you can never have too much "free flow"..

The whole point of exhaust in the aftermarket is to speed up exhaust velocity, which increases the scavenging effect.

If youre having issues its because something you have added has slowed down exhaust velocity allowing it to cool quicker and slow the flow

To produce the most amount of power, an exhaust should have the least amount of restriction to the exhaust flow. Restriction hampers the burnt exhaust gasses from exiting your engine, causing some charge dilution with the incoming fresh fuel air mixture. If all the exhaust gas cannot escape from you cylinders, it dilutes the flammable power producing intake mixture that is trying to come in. The diluted mixture does not burn as well as a pure mixture. This causes a loss of power. You don’t feel so energetic at a packed club with lots of cigarette smoke, sweaty bodies and hot stuffy air right? Neither does your motor. With greater restriction, backpressure is generated making the engine work harder to pump the exhaust out of the engine's cylinders. The harder it is to get the exhaust out; the power wasted to pump the stale exhaust gas out of a restrictive exhaust system could be used to turn the wheels instead. Turbocharged, suspercharged, Nitrous Equipped and engines with really big cams are all especially sensitive to backpressure.

An old hotrodders tall tale is that engines need some backpressure to work properly and make torque. Well that is not true. What engines need is the lowest low backpressure possible but with a high exhaust stream velocity. A fast moving but free flowing gas column in the exhaust helps create a rarefaction or a negative pressure wave behind the exhaust valve right as it opens. This vacuum helps scavenge the cylinder of exhaust gas faster and more thoroughly with less pumping loss-inducing work. A too big in diameter exhaust pipe has low backpressure but lower velocity. The low velocity reduces the effectiveness of this scavenging effect, which has the greatest impact on low-end torque. So remember fast = low backpressure + high velocity. Slow=low backpressure=too big of an exhaust pipe=low velocity. Low backpressure also helps a turbocharger work more effectively.

http://www.motoiq.com/MagazineArticl...st-System.aspx

If you have an issue with a metallic sound, which is the same thing ford had on the new mustang v8 with the overhead cams and the reason RTR developed the new mufflers for their package...use quality mufflers to absorb the sound.

All cars with the direct injection and overhead cams, while more efficient and powerful, tend to have a more metallic outcome when less sound absorbing is around.

exhaust works the same way in a 4 cycle engine. Suck squish bang blow. This is pretty much universal whether its a 4 cylinder or a 12 cylinder if not more. Maganflow put this article out years ago...great read amd youll see all the myths people still have about engines needing backpressure and more.

Also theres an article that has been around about cats and hi flow cats vs stock. Its a good read. http://store.uucmotorwerks.com/articles/catless.htm

In your case my advice is to simply look for some straight thru quality mufflers. Maganflow Borla or Corsa are def of quality. They cost more but you get what you pay for.

[aja342]

Add back pressure in a 4-stroke? Sounds counter intuitive.

Guess I should add 2-strokes do need a small amount of beack pressure, the split second the intake and exhaust ports are exposed.