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is it bad on the motor to run it with a strait exhaust. i was thinking about making a side exit gp style system like the boz bros setup. i no the hotbodies is a strait setup so i take it that it will be fine.
 

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i am running a strait exhaust, but not enough back pressure can be bad for the motor. i made a baffle that fits into the pipe to reduce noise and to add back pressure. the bike has less poping and backfiring with this setup that with my chopped down yoshi slip on. just make a baffle that fits into your gp pipe and you will be ok.
 

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Originally posted by nick041881
i am running a strait exhaust, but not enough back pressure can be bad for the motor. i made a baffle that fits into the pipe to reduce noise and to add back pressure. the bike has less poping and backfiring with this setup that with my chopped down yoshi slip on. just make a baffle that fits into your gp pipe and you will be ok.
Got any pics?
 

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Originally posted by nick041881
i am running a strait exhaust, but not enough back pressure can be bad for the motor. i made a baffle that fits into the pipe to reduce noise and to add back pressure. the bike has less poping and backfiring with this setup that with my chopped down yoshi slip on. just make a baffle that fits into your gp pipe and you will be ok.
backpressure is bad for ANY motor. needing backpressure is a myth.
 

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no backpressure can cause the motor to run lean. without backpressure you will notice that you have almost no torque. 05rrpilot-i will try to get a pic for you.
 

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Not if you feed it more fuel...
Originally posted by nick041881
no backpressure can cause the motor to run lean. without backpressure you will notice that you have almost no torque. 05rrpilot-i will try to get a pic for you.
 

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Originally posted by nick041881
no backpressure can cause the motor to run lean. without backpressure you will notice that you have almost no torque. 05rrpilot-i will try to get a pic for you.
jerzefigga is right. Backpressure is bad. No backpressure will cause the motor to run lean because unfortunately all motors these days are designed to be street legal first, make power second. Exhaust systems kill power, period. Everything from the header collector to the tip of the muffler costs you horsepower. No torque, lean condition - all a matter of tuning the a/f ratio.
 

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Just curious...

If backpressure was bad and straight through is better like you say, why would exhaust companies like Akrapovic, Arrow, Arata, etc, put so much money into technology for high dollar systems to perform the best when if what you were saying is true, you could just run straight pipe and get all the performance out of the bike possible???

I think yall are wrong, sorry to say. Some backpressure is good but there are many more characteristics that make an exhaust system perform that are taken into consideration when a company makes their exhaust system.

That would be why the pros run high dollar exhausts that are proven to outperform the others!

Not to mention, IT WOULD SOUND LIKE SHIT!!!
 

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Hrm, straight pipe. I think mine is close. Granted, I still have the cat in place in the header.

And the whole backpressure argument is as bad and opinionated as the oil and tire arguments. Everyone has a different opinion with no solid proof either way as to what is better or right.


 

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Originally posted by Neversatisfied02
Just curious...

If backpressure was bad and straight through is better like you say, why would exhaust companies like Akrapovic, Arrow, Arata, etc, put so much money into technology for high dollar systems to perform the best when if what you were saying is true, you could just run straight pipe and get all the performance out of the bike possible???

I think yall are wrong, sorry to say. Some backpressure is good but there are many more characteristics that make an exhaust system perform that are taken into consideration when a company makes their exhaust system. Not to mention, IT WOULD SOUND LIKE SHIT!!!
http://www.KawiForums.com/forum/topic.asp?TOPIC_ID=63828

read that. most of the links are outdated but I did a lot of research on this. backpressure is bad, no matter what.

also running lean is all in the tuning.

That would be why the pros run high dollar exhausts that are proven to outperform the others!
 

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when my exhaust fell off i rode home wth no pipe sound is way to loud and the bike is like a slug, no torque whatsoever...
 

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Originally posted by Leanlow
when my exhaust fell off i rode home wth no pipe sound is way to loud and the bike is like a slug, no torque whatsoever...
Thank you! This is exactly my point! If no backpressure and straight through was better, just running the slip-on off should show some kind of gain but it does nothing but hurt performance!

xtremewlr: All exhausts look like that with the straight through design but you would be surprised to know how much the packing in that muffler effects the performance. Its also the size of the opening and all the other factors in the exhaust system that play a roll in how the exhaust gases flow out of the bike and affect the performance.
 

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Originally posted by Neversatisfied02



Thank you! This is exactly my point! If no backpressure and straight through was better, just running the slip-on off should show some kind of gain but it does nothing but hurt performance!

xtremewlr: All exhausts look like that with the straight through design but you would be surprised to know how much the packing in that muffler effects the performance. Its also the size of the opening and all the other factors in the exhaust system that play a roll in how the exhaust gases flow out of the bike and affect the performance.
np bro, some of these ppl really don't know how the exhuast works you on the other hand know your stuff...if straigth headers gave more power it would come like that from the factory but it doesn't...and any slip-on you can see straight through but the mexh has the baffle and packing in it which makes a huge difference in sound and performance...even the hotbodies has a baffle in it...
 

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its EXHAUST VELOCITY and SCAVENGING that are affected, NOT backpressure. ask any engineer about those two. removing the muffler will affect both, especially since its a naturally aspirated engine.

did any of you two read the link I posted? using the correct ID pipe to optimize exhaust velocity is what matters.
 

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Originally posted by moloko



jerzefigga is right. Backpressure is bad. No backpressure will cause the motor to run lean because unfortunately all motors these days are designed to be street legal first, make power second. Exhaust systems kill power, period. Everything from the header collector to the tip of the muffler costs you horsepower. No torque, lean condition - all a matter of tuning the a/f ratio.
Dude your killing me:D This has been covered a thousand times..........But if your just tuning in.
Motors need backpressure! Period !!!! You want proof??? If they didn't our bikes would have 3 inch pipes coming off every cylinder instead of the "tuned pipes" they come with. If your motor ran ONLY at 14,000 rpm then a strait pipe might be best, but a tuned exhaust will make more power across the entire rpm band.
 

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I run a straight pipe on mine at the moment and it doenst seem to bother my bike one bit on the power band. I figured with the cat still intact it should have all the back pressure it needs. am I right or does it need more? I was thinkin of making some sort of new undertail exhaust for my bike. Right now all I have is a turn down comin off where the muffler disconnects from the midpipe.If I get a pcIII where could I get a tune for this custom pipe?I love the tone of the bike and the looks I get when rolling through town.
 

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god, there are some serious mis-educated people on this board. here is my final attempt along with my link - AGAIN

http://www.KawiForums.com/forum/topic.asp?TOPIC_ID=63828[:M86]

"It all started back in the day when the government started regulating vehicle emissions. The first catalytic converters were incredibly restrictive, and most cars were still runing carbs.

The cats were so restrictive that at low engine rpm, air would sometimes pass through the carb twice! Carbs were then re-jetted to compensate for this - to keep the air from getting a double-dose of fuel.

When you take one of these cars and remove the restrictive cat/exhaust to replace it with a free-flowing system, the stock carb will not work right anymore - you will not be getting enough fuel at lower rpms and will get a loss in torque. The solution - change the carb!

Modern catalytic converters are free-flowing compared to early pellet-filled versions. Modern fuel injection systems are not designed to compensate for super restrictive catlysts. Modern fuel injected cars do not need backpressure.

The truth - exhaust gas velocity

Here's the real deal about choosing an exhaust that is too big -

Exhaust gases moving out of your exhaust can be used to pull other exhaust gases out of your cylinders. This is why headers are sized and the tubes matched the way they are. This effect is called scavenging. The faster the gases move, the more you benefit from scavenging.

The larger the tubing, the slower the gases move, the less scavenging occurs. (but, more ultimate flow with less restriction is possible)

The smaller the tubing, the faster the flow. (but obviously, the resistance can quickly overcome the benefit of scavenging if you start reducing your tubing size... a drinking straw simply can't flow enough for a motor)

Notice I didn't say anything about backpressure. Backpressure is just a measure of the restriction in the system. It can be caused by bends, narrow tubing, badly flowing mufflers, etc. Backpressure will be present in any system - but the less that is there the better. A large diameter system with a restrictive muffler (and therefore a high backpressure) will not gain any velocity. So now you will have to worst of both worlds - reduced scavenging and a restriction to free flow at higher rpms.

Some people claim to lose low end power when strapping on a big bore exhaust. This may be true, but it's because of a decrease in the scavenging effect, not because you don't have enough backpressure!"

I am done. reading the replies in this thread is making me dumber. and for those that actually want to know facts, read up on 'fluid dynamics'.
 
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