Quick question for those that have built similar combinations. I am in the process of installing SE204 cams, 1.72 rockers and Vance & Hines dresser duals on my 103" RKC. It already has a set of V&H fishtails on it with the regular baffles. The dresser duals weren't my first choice but I wanted them for sound. Their pipe diameter is only 1 3/4", from the head to the slipon.

The exhaust is louder than I want (live in a densely populated area, don't want to **** off my neighbors going to work at 6:30 am), so I'm thinking about putting the quiet baffles in it. I know the V&H dresser duals aren't exactly the best flowing pieces to begin with, will the combination of those + quiet baffles kill the gains I'm picking up from the cam swap? Or is it going to be negligible between normal and quiet baffles?

Thanks!

 

In most cases the QB improve back pressure and improve Tq.

On both of my bikes running V & H (05 fatboy with BSS & 11 RGC with Pwr Duals) the power s better with the QB

 

the quiet baffles aren't all that quiet,and u may lose 1 or 2 hp at wot,but foul gain a couple tourqes,in the lower rpm.if you want really quiet with good scavenging,super traps with the tunable discs rock.

 

That doesn't sound too significant. Thanks guys, I'll throw them in and see if it at least tames the idle volume down a tiny bit, that's really all I'm after. If it's only going to hurt a little on the top end I can live with it.

 

again, supertrapps may help.

you already seem to know that the header pipes may be working against you in terms of making power.

Mike

 

I have FullSac true duals and V&H Fishtails with the quiet baffles. I have not been able to ride it yet (winter here in central Illinois) since putting on the true duals but the sound is much better at idle and revving than with the stock head pipes. When I put the quiet baffles in several years ago it toned down the noise but still has a good sound. With the true duals on I can't imagine how loud it would be with those stock louvered "baffles" the fishtails came with originally. Also, the quiet baffles did help low end performance somewhat, at least it seemed to feel like it did.

 

I had the same fishtails with stock headpipes-96". I had a feeling they might get just a little too loud when I added the Dresser Duals so I ordered them with the M Rounds. I like them enough (mellower) that I never did put the fishtails back on. If I get bored I may try em perhaps even with the Quiet Baffles.
The 103 build is in process. I'm curious how the sound/performance will be now. SC

 

Your Harley exhaust system is an important part of the components that control airflow through your engine. Other important components include the induction system, cams, and heads. To get the best performance, these components must be tuned together, through a given rpm range. If one of these is changed or modified, the group of components must be retuned to get the maximum performance.

It's important to remember that a louder exhaust system does not always mean better performance. Dyno tests have proven that there is no direct, proportional relationship between sound levels and power. Some quieter aftermarket mufflers actually make more power than some louder ones.

An optimized exhaust is designed to achieve balanced pressure between the engine's intake and exhaust within a given rpm range. The range of 2,000 to 4,000 rpm is usually best for street use. The range of 4,500 to 5,000 rpm and higher is more important for racing applications. No Harley exhaust system performs efficiently through the full rpm range. Knowing this, priorities have to be determined and some compromises have to be made.

HERE'S HOW IT WORKS

The exhaust valve opens, gases go past the valve and create a positive pressure wave that travels out the header pipe. As this positive wave exits, it is converted into a negative wave which moves back up the pipe toward the valve. These positive and negative pressure waves pulsate between the open end of the pipe and the exhaust valve. With the right pipe length, the negative wave will arrive at the exhaust valve during the valve overlap. The negative wave reduces pressure at the valve and helps scavenge combustion gases from the chamber.

Pressure waves can only be timed over a narrow rpm range. The rpm range should be determined so pipe length can be matched to the rpm band. Shorter pipe length improves higher rpm performance. Longer pipe length improves lower rpm performance.

When considering a Harley exhaust, remember there are sometimes tradeoffs between looks and performance. Exhaust system design has a big impact on engine performance. Header pipe diameter, bend radius, pipe length, muffler volume and design of the baffle effect performance.

If the pipe is too long or too short or if the diameter is too big or too small, performance will suffer. Performance also suffers when airflow is restricted by the mufflers. Bigger engines generate more exhaust and need bigger higher-flowing mufflers, but looks can often suffer with increased muffler size.

Harley-Davidson engineers know which header pipes work best in terms of deminsions, so most of the time a set of slip-on mufflers will give you a good performance boost, without the added expense of changing the header pipes.



Here's a look at different types of Harley-Davidson exhaust.


TRUE DUALS

True dual exhaust systems use a separate pipe for each cylinder. This design provides a balanced flow for both cylinders.

TWO-INTO-ONE

The two-into-one design merges both header pipes into a tapered collector. Two-into-one exhaust systems tend to increase low and midrange power.

STRAIGHT PIPES

Two-into-two straight pipes can improve top-end performance but low and midrange power suffers. Throttle response below 3,800 rpm is usually poor. These pipes are also very loud for street use.

STEPPED HEADERS

Stepped headers are divided into two or more sections. Each section is a minimum of 1/8 inch larger in diameter than the previous section. Stepped headers perform better on large-displacement and or higher rpm engines.

SLIP-ON MUFFLERS

Slip-on mufflers are an excellent choice since your keep your stock Harley exhaust pipes while adding improved performance and better sound. Since the original pipes are kept, velocity and lower end torque is retained. Slip-on mufflers increase flow compared to factory mufflers which are restrictive because of EPA regulations. Screamin Eagle slip-ons are a popular choice for Harley riders, especially for touring models.


Regardless of which way you decide to go be certain to take your completed configuration to a trusted HD dealer and have the system tuned and dyno'd to optimize your investment. In my opinion you should choose something that provides at least some back pressure, going with a quiter exhaust is the only way you will get the "perfcect" combo......but if you do go louder having it propperly tuned can seriously reduce the loss in power which yes you could be shooting yourself in the foot by doing....loud pipes save lives.....partially because you will be heard and partially because you won't be going quite as fast when the person who still cant hear you hits you anyway.