The Prophet

Yet another interesting treatise on Exhausts. A little on the "techy" side, but excellent information. (See Attachment below)

I am yet to be totally convinced of the true "performance" benefits of many an aftermarket exhaust offering that is:

a.) Street legal (<94 dB)
b.) Non overly loud or annoying to everyone but... the offending rider?
c.) Not negatively affecting the stock low end torque/powerband.

Folks maybe do not realise that the stock crossover pipe, amoung other beneficial features, also allows both headers to utilise the opposing silencer. That said, when viewing your exhaust system, realise that the exhaust is exiting through both silencers, not just one. Now how restrictive do you think it is?

This explains why most (99%) of the folks at a formerly informative and popular Website who eagerly posted about their respective shiney new exhausts (341 posts) did not need to re-jet. (actually, only 1 out of 341 posters mentioned it, so it is more than 99%)

Almost ALL on the other hand, noted the great loud sound, and how the new $1000 dollar silencers had "transformed" their rides. Hmmm. Also important to consider is the HP/Torque increase per $$$ spent. 2 HP at the very top end for $1000 is $500 / HP way outside the powerband, and of little use to everyday riding. But a lot of noise maybe?

Sounds like a classic placebo effect perhaps, but yes, there is a definite benefit in weight savings.

Don't overlook the possibilities and benefits of considering a well planned and well crafted "baffle-ectomy" on the stock cans. The $/hp gain is drastically reduced, and the flow improved significantly. On the negative side, no weight savings are achieved.

All that said, I've yet to see anyone test a silencer, or perform a comparative analysis of competing silencers - on a properly set up and unbiased flowbench. Usually you see a paper dyno chart, but the tester has also combined other mod's as well, so there is no "apples to apples".

Does this endless rambling mean that you should not consider buying aftermarket exhausts? Absolutely not. What is does hope to offer is the friendly reminder to tread extremely carefully, and choose very, very wisely. All state a "Massive Performance Increase", but I reckon you need to fully define "massive". Sometimes "louder" is convincing as "faster", especially when the wallet dyno is in full effect.

Ride Safe (with good, quiet, high velocity scavenging)!

Bob

Attached Thumbnails

 

__________________

• A good traveler has no fixed plans, and is not intent on arriving. ~Lao Tzu
• Motorcyles are not my whole life, but they make my life whole. ` me

The Prophet

For what it's worth..

An Exhaust pipe length calculator.

Exhaust Length,exhaust pipe,induction


Could be of interest, please add more of these type calculators if you can, it would be good to cross-check with many others for accuracy, and content.

Ride Safe!

Bob

Forchetto

Back in the late 70's when Japanese four-cylinder bikes all came with a bunch of quick-rotting individual silencers, after-market suppliers marketed 4 into 1 exhaust systems for them. They later became standard OEM issue, starting with the Honda CB400F.

Motorcycle Mechanics magazine tested most available after-market 4 into 1 systems, and none of them could even equal the power of the factory system never mind the driveability and sound output. Their advertising said otherwise.

I fitted a 3 into 1 system to my flatmates Suzuki 750 3-cylinder two-stroke after great difficulty, (most of the after market systems were extremely badly made and ill-fitting piles of crap) and he promptly lost 15 mph off the top end...sounded really fast though.

The Prophet

When it comes to Exhaust systems for motorcycles, there are two Huge hurdles to jump:

1.) Sound - a fantastic Placebo, "sounds" better, so it must be faster! Oddly, aftermarket silencers are shorter than stock offers, have less packing material and/or inner baffling, and the chrome plating is usually thinner... but they cost significantly more. Just becaiuse it's louder means zip. Chances are very big that the actual performance enhancement is... less.

2.) The Wallet lightening effect (WLE). Huge placebo. Not too many of us want to admit to being "had", especially after a measurable cash investment. This I would think is very normal. Folks tend to think: "I paid a lotta' money for this... so it MUST be good!"

Ask yourself truthfully: When is the last time you heard, or read, of someone saying "Whoa, I paid almost a grand for that performance add-on, and it actually did nothing for me!" Probably never, as again,. no one likes to admit to being a rube.

Point is: Be extremely careful, selective and objectively scientific about choosing an aftermarket exhaust. Sound is one thing, and OK to seek as recent stock offers are uncomfortably quiet to some.

Performance - which can be defined in an infinite variety of ways, dependent on the end user - is a totally different subject.

Ride Safe (and smart)!

Bob

The Prophet

Here's a pretty decent commentary on the elusive exhaust "Cross-Over Pipe".

Crossover pipe - Harley Davidson Forums: Harley Davidson Motorcycle Forum

Many folks seem to think manufacturers put these on bikes for fun? Or for other, more sinister reasons. Know what it's actually for before you decide to eliminate it.

Always remember - your's is a "Streetbike", not a road-racer, a drag strip meteorite(!), or a Salt Flats speed demon. There is a HUGE technical difference between those few examples.

If you don't know the differemce... well, then you shouldn't have a tool set!

Ride Safe (and efficiently)!

Bob

The Prophet

Another very well researched and presented write-up on Bike exhaust technology. Pour a fresh cuppa coffee, and spend a few minutes to read very thoroughly.

Yes, it's focused primarily on Harley Davidson, but the technology, and the informative scientific background is universal.

Excellent read, if a little rough around the edges at times. You get the impression that the author has a lot of "anger management" issues. Anyway, gloss over the 'passive aggressive' commentary, and the remainder is excellent advice and certainly worthy of a read.

RB Racing LSR 2-1 Exhaust Technology

Also, hang around the site for a while. Check out the "Secrets" tab at the very bottom of the page.

I give it a 9 out of 10. How about you?

Ride Safe!

Bob

The Prophet

A good Graph to illustrate "Pro's 'n Con's" of different pipe diameters. Length also factors in.

The bigger the diameter, the poorer the low end performance, so think twice about buying those big, wide, shorty pipes. They may look 'cool', but they will negatively effect your performance overall.



Note that this exact same concept holds true for carburetor / throttle body size. Too large, and velocity suffers, hence poor turbulance, poor air/fuel atomisation, poor performance.

Both should be maintained as small as reasonably possible to maximize velocity.

We are still talkin' about STREET BIKES here, so don't confuse with Land Speed Record attempt style bikes... another story.

Ride safe!

Bob