straight pipes

i am thinking of putting straight pipes on my 650 has anybody done this i am wondering how loud it will be

i want to cut the down pipes about half way down then flare4 up to 1.5 inch and run back about mid wheel all individual pipes

 

I have straight headers...youll have to rejet most likely. Seems back pressure is always an argument...some guys say its not really necassary others sware without it you blow a valve.

And if your worried about back pressure a friend told me a lil trick to get a lil bit with straight pipes by making "lolipop" tunable baffles.

 

straight pipes are obnoxiously loud. stupid loud. if you want to go deaf, go for it. earplugs wont help, this is the "feel it vibrating your sternum" type of loud!

also, this will help. i stole it from a dirt forum i frequent, its 100% accurate.

 

Good stuff! And this is only the "tip of the iceberg." There is another MAJOR factor affecting exhaust flow, and it is the reason that MUFFLERS (or a similar structure) are necessary as well. SOUND WAVES are physical waves in the air. They bounce around, and can bounce BACK and slow down (or at least mess with smooth flow and therefore the velocity) of the exhaust stream. A good exhaust system not only maintains good exhaust velocity, it also controls the sound waves inherent in the exhaust to KEEP THEM from affecting flow. This is one of the engineering reasons behind a two-stroke's expansion chamber.

A few years back one of the motorcycle mags did (started anyway) an extensive program to try to "hop up" Yamaha's SR500. One of the things they TRIED to eliminate was the SR's strange "collector box" between the headpipe and the muffler (why's a single need a collector anyway?) What they found was very interesting:
To get optimum performance out of the motor on the dyno using a STRAIGHT pipe, the straight pipe had to be nearly 12 feet long to properly control the exhaust pulses in relation to the SOUND pulses. Yamaha's mystery "collector" effectively recreated the 12-foot straight pipe without being 12 feet long. Try as they might, they could NOT get more power out of the motor with the "collector box" gone. They ended up changing the headpipe but leaving the muffler and "collector" in place, for the largest performance improvement, which wasn't much at all.
The most interesting thing about their "series" was that it just fizzled... I had an SR at the time and was following it but it just disappeared.

The magazine guys had discovered something that a lot of us have also learned the hard way: It's nearly impossible to "out engineer" the Yamaha engineers when it comes to engine performance.

One more point that Zook touched on: The "finger over the end of the garden hose" analogy is also helpful in explaining why the stock airbox seems to work so much better than pod filters. A bigger "hole" DOES NOT necessarily mean greater flow, it almost certainly means LESS VELOCITY.

Don't do it, Brent.

 

that was a really good read zookie,

 

i am aware of the performance issues associated with straight pipes however i have one bike am keeping stock my 750 seca and one bike i am customizing my 650 maxim since it is already a miss match of parts i figure i will do something different with it and i am giving it that chopper look so i want it to sound like one as well imet a guy with a 69 honda 550 that had straight pipes and i really liked the sound of them

 

you want to make it sound like a chopper....but i think you mean you want it to sound like a v-twin. its not going to happen. its going to sound like a really loud indy car.

the closest to the low frequency, lopey, popping v-twin sound would be a 4 into 2 setup, you could still use straight pipes, but i would recomend keeping them long or even baffled inserts or a glasspack muffler. my ears were BLEEDING when i ran an open header.

 

I have a Yoshimura header on my bike. When it was new, I removed the baffle and took a short ride, very short! It was unbearably loud. Two things I hate are the straight pipe Harley-davidsons (the owners all want people to look and see what a bada** they are) and snowmobiles with aftermarket pipes on them. They just run at a consistant scream..... no shifting. Maybe I'm just too old. I still like the sound of my bike and can easily live with the Harleys that have a nice deep rumble to them. Straight pipes just pi** people off. Don't do it.

 

i hate the sound of a vtwin and i love the sound of my 650 i would just like it louder i dont want my ears to bleed when i ride

the 550 i saw that had straight pipes wasnt that loud
if i run it with the mufflers replaced with straight pipes and keep the collector would it be as loud as straight pipes all the way

 

My '81 550 came with an open-baffled Kerker on it. It was UNGAWDLY loud, I couldn't ride it that way. I took it for a short ride one day and came back. My daughter said "what'd you do, go a couple miles outside town then turn around and come back?" I said yeah, why? She said "because I could hear you the whole way."

An XJ with open pipes sounds like an '80s IndyCar.

probably not as bad. You can try this easily, just pull the mufflers and leave everything else on, see how it sounds. It's still gonna be loud, but maybe you'll like it.

 

My 900 has standard headers and collector but my mufflers are custom made straight through perforated pipes.

It's loud but not over the top loud... I do however wear noise cancelling earphones inside my helmet to help cut out some of the noise on the open road.

XJ900 Video

 

Some folks here have used short stubby after market mufflers.
I don't know the name maybe Harley.
They are about 10 inches long. this may give you the look you want and the loudness with out the deafness.
I have a 4 into 1 on mine and when I where a half helmet it is annoyingly loud for long stretches.
With the full face it sounds fantastic, cuts the whine leaves the throatiness.

 

Edit: created my my own thread so i don't hijack this one.

 

I have home made 4 into 2 straight pipes on my 650. I love it. Yes it is loud, but it isn't that bad. The indy car analogy sounds about right. I put a couple of home made baffles (they don't really do anything) in there just to pass inspection. I am about to add 31" upswept fishtails to it. Not sure what it will sound like then. The pipes from the cylinder head to the tip will be almost 4' long. I didn't rejet, and I am running pods. And it isn't running lean. I probably lost some power on the lower end, but my airbox was shot and missing the boots to it so pods were cheaper (plus removing the airbox made more room for my wiring because I rewired the whole bike, and the wad that would normally be in the headlight, is now under the seat, along with the horn). And my bike didn't come with an exhaust, so I made my own. I really don't think it is lacking any power in the high RPMs. I was impressed with it the first time I rode this bike.

I am probably one of the few on here who would say go for it.

 

My pipes end directly under my seat and its not too loud.

 

I'm having a hard time grasping my feeble little mind around the "finger over the garden hose" analogy. Putting your finger over the end of a water hose may make the water stream stronger, but fill up a bucket. Then fill up a bucket with the end of the hose free of obstruction (finger). Which fills up quicker? What do you do when you want to cut back on the flow of water coming out your hose? You start closing the valve at the faucet, thus making a partial blockage. Only now the blockage has been moved. A partial blockage at the end of the hose has more velocity and pressure, but is moving LESS volume. A blockage is a restriction whether at the front of the hose or the end of the hose. If supply remains the constant, the only way to get more pressure is to reduce flow. Pressure isn't the same as velocity.

 

the key is to have as much VELOCITY, without BACK PRESSURE.

think of the exhaust flow as a rope.....it needs to be pulled out straight and fast, rather than pushed out. ever try to push a rope?

nothing about straight pipes makes them rob low end power. its all about the pipe diameter. you need to match the pipe diameter for the engine size and rpm. large diameter 3" straight pipes will run great at 10,000rpms. they will not be great at 3000. the flip side....1" pipes will run great at 3000, but choke out long before 10k.

a perfectly tuned exhaust system will have high velocity, and will create a negative pressure area in the exhaust port exactly as the exhaust valve is opening. this makes the high exhaust velocity pull (scavenge) the gases out of the cylinder. otherwise the piston needs to PUSH the exhaust out, as well as get the static/slow moving gases in the pipes moving as well (robs power).

 

... but to have a pipe that is tuned to draw out gasses you have to change the cam timing so you don't loose your fuel economy

correct?

 

I got these off eBay.

http://cgi.ebay.com/ebaymotors/ws/eBayI ... &viewitem=

They're glass packed and have a really nice Scorpion FZ6 bass sound to them. When I throw open the throttle it sounds like a jet engine spooling up. I really enjoy them and they're easy to make yourself without spending hundreds of dollars.

 

oh yes.....cams come into play, even the intake cam profile and timing.....because we can go even deeper and start talking about the valve overlap crossflow, wich is where the scavenging effect goes as far as pulling the intake charge into the cylinder! it can get real deep real quick!

even the stock cams are good for a certain rpm window, and on my bike its clearly at the 5-8k rpm range. 6000-8000 gets the holy f'ing crap kind of feel when i ran the open 4-1 header!