Full Exhaust, what is It?????

[BuStEdAsS996]

What is the deal with a full exhaust. As in why do people replace there stocl headers for different ones. I understand yamaha has the exup valve bull shit in its pipe and a new pipe wouldnt have that. But if your bikes pipe has nothing restrictive in it then why chnage it? Would a new pipe be the same thing. The only thin i can think of that would be different would be th enew pipe is lighter.

[Zyankaly]

don't know for 4-stroke, but for 2-stroke its a science of its own. You can change the bikes riding by only adding 1cm or taking away one. for the 4strokes... don't know, different sound mainly... and maybe they do get the exausts out faster if u play around with intakes and air filters.
can we have any mech giving some knowledge in here ?

[ZXLNT]

Most factory exhausts are restrictive. Power and torque gains can be had by replacing the exhaust with a free flowing aftermarket exhaust. Just like cars, people like to hot rod things...

[robbieace]

It is also one of the more defineing ways to customize your bike

[Süsser Tod]

It may not be as dramatic as it is with 2 strokes, but for fluid dinamics every little bit can make a difference.


Full exhaust systems have variations of diameter of various parts of the system to accelerate/synchronize the exhaust pulses and provide enough backpressure without too much restriction for specific rpms and riding conditions.

All of that can get you some aditional horses, that by themselves may be insignificant, but coupled with several modifications can make a real difference. Another very important part of a full exhaust is weight, they arent built following the cost restrictions that most bike manufacturers have to face while building the whole bike, so they can use different, better and lighter materials.

[Zyankaly]

Didn't know that stocks would be very restrictive if u leave the rest of the bike stock (on 4 strokes) ???

And backpressure on 4 strokes ?? I thogh 4-strokes don't need backpressure and that you could actualy take the complete exaust pipe off and only having a damn loud bike but not a damn slow bike.
(I don't have mutch knowledge on 4-strokes so I'm not giving garantee on this )

[Darkstar]

i dont know the full science behind it, but some back pressure is needed for 4 strokes, but not a lot.

stock exhaust are pretty restrictive and i personally hate the sound of them. with a full exhaust and pc3(r) you can usually get 10+hp with them. aftermarket exhaust's also usually shave off 10-15 lbs. (full arata exhaust on a 600RR is 10+ hp and -15lbs!!!)

[MoTrFinger]

Originally Posted by RSRCR

i dont know the full science behind it, but some back pressure is needed for 4 strokes, but not a lot.

stock exhaust are pretty restrictive and i personally hate the sound of them. with a full exhaust and pc3(r) you can usually get 10+hp with them. aftermarket exhaust's also usually shave off 10-15 lbs. (full arata exhaust on a 600RR is 10+ hp and -15lbs!!!)

I have a full titanium exhaust from Arata for my 04 Busa. It gives a few extra hp especially with the PCIIIr but when I put the new exhaust the handling of the bike improved dramatically. I shaved off closer to 40lbs with with mine (went from 2 canisters to 1) and took off some of the weight where it made a big difference (up front) especially under braking.

[Redstar11]

There is very much to 4 stroke exhaust performance. I'm going to make this lengthy, but accurate. The obvious primary functions of the exhaust system is to direct hot, diry gases away from the combustion chamber and to baffle noise made during the combustion process. In addition, and one of the most important aspects of the exhausts functions is to encourage a fresh, cool, fuel and air mixture into the cylinder area using a process call scavenging. Scavenging, is quite difficult to explain unless one somewhat understands thermodynamics, however, I will try to put it into laymans terms. For every gas pulse resulting from combustion, there is a wave created (for lack of a better term) This wave is the exhaust gases. After the combustion process the exhaust valve opens, creating a pressure difference, allowing the exhaust gases to exit the combustion chamber. As this wave rushes out through the exhaust manifold, there is a negative pressure behind it, which pulls in the fresh AIR FUEL MIXTURE from the intake manifold. This happens when Intake and Exhaust valves are open simultaneously during the OVERLAP CAM EVENT. This where the exhaust system comes into play. The exhaust systems are designed with 2 things in mind. 1) Where the bike is designed to performed the best, and 2) Governmental Regulation. Keep in mind, that a sportbike is designed to live it's life at high RPMS, and it's with that in mind that the exhaust systems are designed. To keep this simple I will keep the physics brief. However, it must be stated that exhaust systems and Intake manifold systems are designed using a simple physical law called the venturi effect. Basically it states that as (air) velocity increases, the (barometric) pressure decreases. For example, air traveling through a tube shaped like an hour glass will speed up as it reaches the middle, and slow down as it travels away from it.

Basically, if the exhaust pipes are too big in diameter, the exhaust gases do not travel fast enough and the pulses will overcome each other travel back into the combustion chamber. Obviously, exhaust gases will force some of the air/fuel mixture to stay in the intake manifold resulting in a lower volumetric effieciency for the combustion. Basicially, less air/fuel, less power.

Like wise, pipes too small in diameter do not flow ENOUGH to remove the gases away from the exhaust manifold and gases end up staying in the combustion chamber producing the same effect as stated before.

For reference this is simply put. Larger pipes in diameter, will flow more gas and will improve TOP END PERFORMANCE. With more RPMS, the combustion event happens quicker and exhaust gas velocity is sped up enough to overcome the large pipes and even take advantage of their larger flow characteristics. This is why Nascars have virtually no exhaust system. They spend their lives at the TOP END of their RPM range.

Pipes smaller in diameter will have much better LOW END PERFORMANCE. The pipes are smaller in diameter which increases the speed of the exhaust gases via the VENTURI EFFECT, which in turn increases the SCAVENGING effect I explained earlier.

So basically it boils down to building an exhaust system which fits your bike's purpose. You can't have the best of both worlds. Build pipes with more top end performance characteristics, and you sacrafice low end performance. Likewise when opposite.

So when it comes down our pipes on our sportbikes, you must keep in mind that these bikes are designed to be on the track where HIGH RPMS are sustained. However, because these are street bikes, they must give them so amount of street ability. So stock pipes are designed to give a tolerable mix of low end and top end performance. They also must conform to Governmental Regulations, which is where many aftermarket pipe companies take advantage because they do not have to conform to these laws. This is why aftermarket pipes MAY see gains in performance. But peak numbers mena nothing. One must check the dyno graphs and find out exactly where these HP gains are being made. Yes, they might make +6 HP, but you might only see it at 12500 RPMS, and how many of you actually ride that high in the RPM range? Think about it.

This is really an overview, there are many concepts I have left out (blowdown, reversion, sonic and thermal scavenging) for the sake of simplictiy. However, this should give you a basic idea that 4 stroke exhaust is essential and just as complex and important as two stroke exhaust.

Let me know if you have any other questions.

[BuStEdAsS996]

okedokey then. This is all pretty much what i knew already. but i just forgot about all the little things add up to big power.

thanks guys

[monkeywrench]

if you're just looking for power, it's a bloody big waste of money. red is a base line bog stock run. dark blue is with a US$1,300 full akropovic system. no other mods. went from 101 to 102.

"with a full exhaust and pc3(r) you can usually get 10+hp with them." ROFLMAFAO!!!!!!!!!!!!!! i have a pc3 on order, we'll see if that'll gain me 9hp. even if it does, could have been done w/o the pipes.

having said all that, the whole system weighs less than the stock endcan, and i can feel a HUGE difference in handling. the bottom of the bike swings back and forth much easier, if that makes sense. and it looks the business

[/IMG]

[Unsane125]

I have always felt that an exhaust increased throttle response on my race bikes, but they have all been carbed, with the shorty titanium system on the z1000 I definetly shaved off around 35 pounds, those stockers were massive.

to me its unbelievable how expensive an exhaust is, even for my 250F they are upwards of 1k. it gives a nice look and sound though, that motor work alone wont really give.

[TheTon]

This thread is only like 5 years old..

[RLinNH]

I like them due to the loss of wieght, and also a minimal increase in HP. Now, saying that, this past weekend I installed a Jardine GP1 on my bike. All I can say is, HOLY SHIT THAT THING IS LOUD!!! I really wanted to save money on my exhaust on this bike, but I won't be riding with this exhaust for the entire season. Once I get the scratch together, it's a Full Yoshimura exhaust along with a Power Commander for this Bike. I have done full Titanium systems in the past, and I was thoroughly pleased with the results. As far as this new slip on that I have on my Bike now, I can not wait to sell it on E-Bay.

[jk750]

This thread is almost FIVE YEARS OLD.