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Discussion Starter #1
sooo i had a thought. just not real in the know about exhausts. i have some idea of how they affect performance but by no means an expert anyway i had an idea of chopping the mid pipe in a slash cut kinda way.....



and the throwing some of these ebay baffles.....



in the mid pipe after the htev system




was wondering if you all that know about such things think it would work to create enough back pressure with those baffles in the mid pipe like that to keep the low n mid range torque curve somewhat close to where its at and would those things quieten it up enough to be bearable? i like a loud pipe but ive heard it with out the oem muffler on there and it was too loud. and i drove it with the pipe off around the block and it killed the low end torque enough to be noticeable.

so wasnt sure of a few things...

would the baffles be ok to put up there or do they hafta go in the very end of the pipe to work?

would the baffles create enough back pressure to not completely ruin the engine performance and or cause any damage to the valves like running just a straight pipe would? i should mention that i was thinking one 8" baffle for each of the 4 pipes behind the htev valve.

and would it quieten it with baffles like that enough to be ok? i know those things are typically for v twin engines but they are similar to aftermarket bolt on decibel killers. like i said i like a loud pipe but just the straight pipe withput the oem muffler was too much. with the oem muffler its just about the quietest bike around n thats no good for me.

im looking for a pipe after rashing mine up from my recent get-off but money is tight n this modification would run about 40$. lol the thing is if it didnt work id hafta buy a new mid pipe which is around 60-70$ on ebay and still hafta buy a new pipe.

honestly i havent really considered doing this mostly because i have no idea if it would even be worth the time which is why im asking. i think with a nice slash cut tho n some flat black paint on it it wouldnt look all that bad. im very much a form follows function kinda guy tho so i care more about how it works than how it looks. so id love to hear some feedback mostly on if it would function and what i could expect in those terms more than its aesthetics.

thanks for the info everyone and the opinions on the concept!
 

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It is a cool concept. When I was designing mine, I thought of doing something similar by using two of the longer flexible baffles in each of the two splits before it enters into the last collector before the muffler and have a cut similar to where yours is. I was advised against it by several here and by an ancient MMI teacher saying it would be too loud to deal with.

I also learned from a racing guru here that needing backpressure was a myth and that all you need is a scavenging effect. He stated that backpressure only robbed horsepower and helped to hold the engine back.

This is what he explained...

Originally Posted by saf
"Chukky, You dont want backpressure in a natrually aspirated engine, nor any engine actually, however turbo motors need backpressure between the piston top and the ex turbine so it functions, but in your bike for eg, you need what is known as scavenging, and often confused with backpressure, but one is a apple and one is a orange.

Scavenging is a tuned length of tube (exhaust tube runner) that meets in a common collector (4 into 1) or a opposed firing cylinder (2 into 1).

Backpressure in a engine is a pressure built up between the piston top and tip of exhaust. If you put your hand over the end of the muffler, thats backpressure. Backpressure is also a resistance to the upward motion of the 4th stroke (exhaust) therefore something that robs the the crank of power. If the crank made for eg 5hp, and if you have enough backpressure of say 1hp, natrually you get 4hp out the end of the crank. Not good.

This is why any car that is unrestricted, does not run mufflers, or minimal ones for noise. F1, Moto GP, Top Fuel etc etc, all run straight pipes, less backpressure.

As far as scavenging, imagine in the most basic term, you have a 2 cyl engine, and one fires a pulse of exhaust gas and sonic wave of noise, it reaches whats known as the common collector, at what point it creates a draft past the runner next to it, but at the is exhaust moment, the exhaust valve on the other cyl opens, and the draft now aids the exhaust flow from the second cyl past the ex valve, and down the runner. When IT gets to the collector, the first cyl is on a exhaust stroke again ..... and tahts scavenging. One aiding another.

Now times that by 2 more cyl, as in your bike.
"

Still difficult to understand for me until I see the formulas that are used (my buddy has them from MMI) to help me comprehend general lengths needed etc..


That being said... I personally think it would be too loud. :twocents: Mine has a small muffler and I think it is at the upper end of the noise level I would want on the street..

If you look at other similar systems I think they give db ratings (like the "tips" and whatnot that do little such as voodoo). You can compare that to aftermarket mufflers online they should give db ratings on their site. Several db can be a fairly large difference in volume...

Just food for thought! :thumb:
 

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Discussion Starter #5
well i know they make these short ones that have a baffle built into them for lots of sport bikes. i cant imagine that doing what i mentioned would be any louder than these. specially considering i was thinking 4 8" baffles n that would hafta do more than whatever baffle length they build into these pipes you can buy. these pipes say they are about 105 decibels

 

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The voodoo style exhaust makes the bike sound terrible in my opinion. The point I was trying to make with my exhaust was that I only have another 11" of gutted muffler after the flange and my exhaust sounds perfect to me.

I could not see why it would hurt to make your slash cut without the baffles. I really do not see it being that much louder than mine. I was originally going to just cut my flange off, but decided against it. I would make sure to have a pc3 or pcv installed to help the low end and a/f ratio.

Go to youtube and search CBR 954RR with out exhaust. They are really not that loud.
 

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You better buy online and use a credit card instead. You can't count on anything these days until you are face to face, and then, you still got a 50/50 chance until you use it, to confirm you're not getting screwed.
7 posts and living near the Amish wasn't enough credibility, not to mention all the help he got from this forum. Just another one way street.
 

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Discussion Starter #11
i wasnt holding my breath. i found a guy online thats selling a devil dual pipe exhaust. he wants 250 for it. ive never really been into the look of the devil dual set-up but they do sound awesome.



 
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