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Discussion Starter #1
Ive seen abuncha ppl at the beach take there pipe off there bike...Im guessin just to make abuncha noise down there...but i was wondering if it'd hurt my bike to take my pipe off just to see what she sounds like???An would it cause any damage if i rode it like that for like a day or two???I dont have a power commmader either
 

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it won't hurt anything. All it will do is annoy people and make you look stupid. Some people will tell you that you can warp the valves. Not true. The headers are too long, and the cool air rushing in, would be warmed up by the time it got to the valves, if it even made it that far. You'll look dumb, but the bke will be ok.
 

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it won't hurt anything. All it will do is annoy people and make you look stupid. Some people will tell you that you can warp the valves. Not true. The headers are too long, and the cool air rushing in, would be warmed up by the time it got to the valves, if it even made it that far. You'll look dumb, but the bke will be ok.
:werd:
 

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I wouldnt do it, There is a certain point where it is just too much noise and becomes annoying.
 

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The Bestest Racer
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I ran a 99 600 like that for Summer Nationals when I did a few drag races and burnouts. The bike wasn't harmed at all.
 

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Discussion Starter #6 (Edited)
damn yall were right that shit is loud as hell,im keeping my pipe on.....I also couldn figure out how to get that valve off either??
 

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damn yall were right that shit is loud as hell,im keeping my pipe on.....I also couldn figure out how to get that valve off either??
If you're reffering to the set valve, the bolts that hold the butterfly on are welded so you can either leave it flattened out or do what I did and drill the bastards until the butterfly comes off. I went back later and cut the shaft out and welded the hole on the outside.

Open pipes suck unless you are doing some serious high RPM racing. You loose so much bottom end torque, it's a PITA to drive on the street.
 

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yea its loud, and yea it will hurt the bike if ur not carefull, ive been told by lots of mechanics that it will burn up valves, but maybe they just dont like the noise, a few days wont hurt, but dont make it permenant, i wouldnt take the chance
 

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You loose so much bottom end torque
:laughingr

Can you explain to me how you can loose torque if you don't even change the diameter of the pipe?

the only exception is unless ur running a turbo, then run open headers

And where do you hang the turbo from? The part you are talking about is called the downpipe.
 

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:laughingr

Can you explain to me how you can loose torque if you don't even change the diameter of the pipe?



And where do you hang the turbo from? The part you are talking about is called the downpipe.
not changing the diameter, but thength will be changed and that DOES affect torque. How much on a street bike? dunno.
 

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well also at the same time by removing the muffler to take away the back pressure in the exhaust so you lose some torque... but like scott said how much who knows???
Thanks.

You do loose low end torque by removing the stock exhaust due to lack of back pressure. Tube size and length affect how the power curve is laid out.

As for cracking on the guy about running open pipes with the header......you know what he meant. Turbo's make the exhaust quiter, besides the whine, so you could get away with open pipes. Plus, they spool faster with no back pressure.
 

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You all are in carb world. You can make more power with less restrictions period. The only problem is you have to tune for it something you can't do with a carb. Stop listening to the good old boys, their time has past.
 

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You all are in carb world. You can make more power with less restrictions period. The only problem is you have to tune for it something you can't do with a carb. Stop listening to the good old boys, their time has past.
Sorry but you are wrong. You still have to tune a header on a car or bike just like you used to. The only diff is how you adjust your fuel and ignition.

Take your bike to the strip and run it tuned with the exhaust and then go run it with a tuned engine on open headers. Unless you've got the gearing to keep it reved in it's power range the whole time, you are going to run slower.
 

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Our bikes have tuned exhausts - the length and diameter of the headers, coupled with the back pressure, causes a scavenging effect which occurs at a specific spot in the RPM band, which on a street bike is down around 4,000 - 5,000 or so RPM to give it improved torque at those RPM's. Note I said improved torque - not peak torque or horsepower. This still occurs at somewhere around 11,000 - 12,000 or so depending on your bike.

Removing a restriction has the effect of moving the optimal speed for exhaust scavenging to a higher RPM, so by doing so you will both increase top end horsepower and torque by some amount, at the expense of losing low RPM torque and RPM by some amount.
 

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Our bikes have tuned exhausts - the length and diameter of the headers, coupled with the back pressure, causes a scavenging effect which occurs at a specific spot in the RPM band, which on a street bike is down around 4,000 - 5,000 or so RPM to give it improved torque at those RPM's. Note I said improved torque - not peak torque or horsepower. This still occurs at somewhere around 11,000 - 12,000 or so depending on your bike.

Removing a restriction has the effect of moving the optimal speed for exhaust scavenging to a higher RPM, so by doing so you will both increase top end horsepower and torque by some amount, at the expense of losing low RPM torque and RPM by some amount.
+1000

How can you argue with that.
 

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tee, you're under the mistaken impression that scavenging relies on backpressure, it does not. the more backpressure you have the more burned fuel stays in the cylinder. the more burned fuel that stays in the cylinder the less new fuel/air goes in. Enlighten me as to how this is a good thing.
 

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Holy crap so many newbies. Backpressure IS BAD PERIOD!!!!

Before passing on false info, get your facts right.


Backpressure: The myth and why it's wrong.

I. Introduction

One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Hondas need backpressure" when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion.

II. Some basic exhaust theory

Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream.

III. Backpressure and velocity

Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.

The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitable exhaust gas velocity. Backpressure in it's most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM.

Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari's which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM.

IV. So how did this myth come to be?

I often wonder how the myth "Hondas need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.

V. So why is exhaust velocity so important?

The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous "wash me please" messages written in the thickly collected dust on the rear door(s).

VI. Conclusion.

SO it turns out that Hondas don't need backpressure, they need as high a flow velocity as possible with as little backpressure as possible."
 

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Holy crap so many newbies. Backpressure IS BAD PERIOD!!!!

Before passing on false info, get your facts right.


Backpressure: The myth and why it's wrong.

I. Introduction

One of the most misunderstood concepts in exhaust theory is backpressure. People love to talk about backpressure on message boards with no real understanding of what it is and what it's consequences are. I'm sure many of you have heard or read the phrase "Hondas need backpressure" when discussing exhaust upgrades. That phrase is in fact completely inaccurate and a wholly misguided notion.

II. Some basic exhaust theory

Your exhaust system is designed to evacuate gases from the combustion chamber quickly and efficently. Exhaust gases are not produced in a smooth stream; exhaust gases originate in pulses. A 4 cylinder motor will have 4 distinct pulses per complete engine cycle, a 6 cylinder has 6 pules and so on. The more pulses that are produced, the more continuous the exhaust flow. Backpressure can be loosely defined as the resistance to positive flow - in this case, the resistance to positive flow of the exhaust stream.

III. Backpressure and velocity

Some people operate under the misguided notion that wider pipes are more effective at clearing the combustion chamber than narrower pipes. It's not hard to see how this misconception is appealing - wider pipes have the capability to flow more than narrower pipes. So if they have the ability to flow more, why isn't "wider is better" a good rule of thumb for exhaust upgrading? In a word - VELOCITY. I'm sure that all of you have at one time used a garden hose w/o a spray nozzle on it. If you let the water just run unrestricted out of the house it flows at a rather slow rate. However, if you take your finger and cover part of the opening, the water will flow out at a much much faster rate.

The astute exhaust designer knows that you must balance flow capacity with velocity. You want the exhaust gases to exit the chamber and speed along at the highest velocity possible - you want a FAST exhaust stream. If you have two exhaust pulses of equal volume, one in a 2" pipe and one in a 3" pipe, the pulse in the 2" pipe will be traveling considerably FASTER than the pulse in the 3" pipe. While it is true that the narrower the pipe, the higher the velocity of the exiting gases, you want make sure the pipe is wide enough so that there is as little backpressure as possible while maintaining suitable exhaust gas velocity. Backpressure in it's most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust flows backwards, which is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero backpressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range. A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of backpressure at high rpm. Thus if your powerband is located 2-3000 RPM you'd want a narrower pipe than if your powerband is located at 8-9000RPM.

Many engineers try to work around the RPM specific nature of pipe diameters by using setups that are capable of creating a similar effect as a change in pipe diameter on the fly. The most advanced is Ferrari's which consists of two exhaust paths after the header - at low RPM only one path is open to maintain exhaust velocity, but as RPM climbs and exhaust volume increases, the second path is opened to curb backpressure - since there is greater exhaust volume there is no loss in flow velocity. BMW and Nissan use a simpler and less effective method - there is a single exhaust path to the muffler; the muffler has two paths; one path is closed at low RPM but both are open at high RPM.

IV. So how did this myth come to be?

I often wonder how the myth "Hondas need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.

V. So why is exhaust velocity so important?

The faster an exhaust pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The guiding principles of exhaust pulse scavenging are a bit beyond the scope of this doc but the general idea is a fast moving pulse creates a low pressure area behind it. This low pressure area acts as a vacuum and draws along the air behind it. A similar example would be a vehicle traveling at a high rate of speed on a dusty road. There is a low pressure area immediately behind the moving vehicle - dust particles get sucked into this low pressure area causing it to collect on the back of the vehicle. This effect is most noticeable on vans and hatchbacks which tend to create large trailing low pressure areas - giving rise to the numerous "wash me please" messages written in the thickly collected dust on the rear door(s).

VI. Conclusion.

SO it turns out that Hondas don't need backpressure, they need as high a flow velocity as possible with as little backpressure as possible."
This makes perfect sense. If you have back pressure your going to have spent exhaust gases in your combustion chamber that will not be helpful. You want fresh air which is why you higher moving exhaust to suck in that fresh air. Here is another tech article I gound to explain burnt valves.

A "burned valve" is a valve that has overheated and lost its ability to hold a leak-free seal. Valve burning is usually limited to exhaust valves because they run much hotter than intake valves.

The diagnosis of a burned valve is usually the result of a compression test. If a cylinder shows little or no compression, it frequently means the exhaust valve is not sealing. The valve may or may not be actually burnt (melted), but have other physical damage such as cracks or areas where pieces of metal are missing or eroded away from the valve face.

The cure for this condition is to remove the cylinder head, replace the bad valve and reface (or replace) the valve seat. As a rule, the head is usually given a complete valve job at the same time because the rest of the valves and guides probably need attention, too. If one exhaust valve has failed, the rest are probably on the verge of failure if they haven’t already started to leak.

Why Valves Burn
There are several reasons why valves burn. One is normal wear. As an engine accumulates miles, the constant pounding and thermal erosion wears away the metal on the face of the valve and seat. The exhaust valve sheds most of its heat through the seat, so when the face and seat become worn and the area of contact is reduced, the valve starts to run hot. Eventually the buildup of heat weakens the metal and pieces of it start to break or flake away. Once this happens, it forms a hot spot that accelerates the process all the more. The valve begins to leak and compression drops. The result is a weak or dead cylinder and a noticeable drop in engine power, smoothness and performance.

A bad exhaust valve will also increase exhaust emissions significantly because it allows unburned fuel to leak into the exhaust. High hydrocarbon (HC) emissions, therefore, may also be an indicator of a burned valve.

An exhaust valve can also burn if the valve lash closes up for some reason (improper lash adjustment, cam or lifter wear, a bent push rod, worn rocker arm or cam follower, etc.). The lack of lash (clearance) in the valvetrain prevents the valve from closing fully, which causes it to leak compression and overheat.

Valve burning can also be caused by any condition that makes the engine run hot or elevates combustion temperatures. This includes cooling problems, abnormal combustion like detonation or preignition, loss of exhaust gas recirculation (EGR), retarded ignition timing or lean fuel mixtures.

Valve Recession
A condition known as "valve recession" can allow the valves to recede or sink into the head because of excessive seat wear. This causes the valve lash to be lost which allows the valves to leak and burn. It occurs primarily in older engines (mostly those built prior to 1975) that were not designed to run on unleaded gasoline. When leaded gasoline was still around, lead acted like a lubricant to reduce valve seat wear. But when lead was eliminated, it meant engines had to be made with harder seats. These older engines didn’t have hard seats, so many began to experience valve wear problems when switched to unleaded fuel. If you’re driving an antique or classic car, therefore, you should either use some type of lead substitute fuel additive to protect the valves or have the seats replaced with hard seats when the engine is overhauled.
 
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