forward flow - Toyota Corolla, 1.8 L, 2003

Fans of fast driving always lack the power of a
standard motor. You have heard of the so-called sports exhaust
systems. Let's figure out what's what, in this matter. And anyway, why do
it.
What for?
The entire exhaust system is a kind of
additional resistance to the engine (along with air, road,
attraction, etc.). I think that there is no need to explain the unwritten truths:
THE MORE THE OUTPUT RESISTANCE, THE MORE THE MOTOR POWER IS MORE. And, accordingly, the
thrust.
What is the exhaust system?
Accordingly, the muffler of a standard, modern
car is a whole set of parts:

-Exhaust manifold
-Catalyst
-Resonator
-Muffler
When upgrading the exhaust system, it must be thrown away
and done all over again.
Let's figure out what new needs to be installed and why.
Spiders. Most of the
exhaust losses are in the exhaust manifold. In sports and tuning, the regular one is replaced by the so-called
"spider" - it differs in the shape and order of connection of the intake pipes with the exhaust
windows. "Spiders" are "short" and "long" (two Y). If we take a 4-cylinder
engine, then the "long" pipe diagram is built according to the formula 4-> 2-> 1, and the
"short" 4-> 1. The "long" spider has a coupling 2-> 1,
"short" is more complex geometry. Manifold 4-> 1 gives extra power
only in a very narrow rpm range, beyond 6000 rpm, and is usually used
for high-performance engines with wide-phase camshafts, that is, in
sports cars. Manifolds 4-> 2-> 1 are suitable for amateur
tuning, as they provide a certain increase in power and torque over a
fairly wide rpm range. Adding power gives about 5-7% for
VAZ engines. In the direct-flow system, intermediate straight
pipes of an increased diameter and resonators of reduced resistance are also used . Instead of
rigid joints, "corrugations" (bellows) or ball joints are often used.
The latter do not create parasitic resonance frequencies, but are short-lived. But the
"corrugations" soften the shock at startup and a sharp increase in power.
All these parts are easy to install on your own, there would be a
lift or a pit, a tool, dexterous hands and a bright head. But it is better to entrust the
work to the service: against the background of the price of parts, the installation is cheap, moreover, it requires a
"grinder", welding and a pipe bender. And the guarantee is not worth losing. The movement of
exhaust gases in the exhaust pipe is an oscillatory process
that can be matched experimentally with the oscillatory process of the
movement of the combustible mixture in the intake tract in such a way as to improve the
cleaning of the cylinder from exhaust gases and its filling with fresh mixture. Pressure
in the exhaust pipe is subject to sharp fluctuations during the entire discharge period.
At the first moment after the opening of the exhaust valve, the combustion products rush
into the exhaust pipe at a very high speed, exceeding the speed of
sound propagation. Rapid removal of 50% of combustion products entails the
formation of a vacuum in the cylinder, which can reach up to 0.5 kgf / cm2. Likewise
, periods of reduced pressure are formed in the exhaust pipe. Experiments
with exhaust pipes have proven that the length of the pipe does not affect the efficiency of
cleaning the cylinder in the first stage of the exhaust process, but on the other hand, with an increase in the length of the
pipe, within certain limits, the duration of the period increases.
which is maintained under vacuum. With a change in the rotational speed, the period of
reduced pressure in the exhaust system not only changes in the duration and
amount of vacuum, but also shifts in the angle of rotation of the crankshaft. Therefore,
each operating mode of the engine corresponds to a certain optimum length of the
exhaust pipe. There are two processes in the ICE exhaust system. The first is
a more or less damped gas outflow through the pipes. The second is the
propagation of shock waves (sound) in a gas medium. Both processes have an
impact on the cylinder filling ratio. In the first case: a large
resistance to the flow of gases (plug the exhaust pipe!) Will cause a decrease in quality
blowdown and power loss. It is quite clear that the shorter and larger the
pipe diameter, the lower its resistance to flow. In real life, for a
1.5-liter engine operating at speeds of no higher than 8000, a
diameter of 45 - 50 mm with a length of 3 - 3.5 meters is sufficient . A further increase in the diameter does not
cause a significant decrease in dynamic resistance. Further, it is clear
that if a
reflector, which is called a resonator, is built at a certain distance from the valve in the exhaust system , then the
blowing of the cylinders will improve at certain speeds , which will increase the engine torque. This phenomenon
is called "tuned exhaust" and is used to correct torque
crooked. If the task is to increase the power, as for a sports motor, then the
resonator is tuned to the area falling after the maximum. Thus, the
torque is extended at high revs. If we want to get a more "high-torque"
motor at the bottom, then tune it to the growing area to the maximum.
Banks. The task of the muffler is only to extinguish the sound by
multiple reflections in the labyrinth or direct it to sound
- absorbing material (glass wool, for example), providing as little resistance as possible to the flow of
gases. Most tuning mufflers are universal. They can be fitted to
all vehicles of a certain type without exception (food, displacement, class).
Problems arise only when the selected part is large for the machine, but such
misunderstandings are extremely rare. The buyer needs to decide on his preferences -
whether he wants blued steel, nickel plating or dull white metal, one or two
outlets, straight pipes, bent up or down, with or without an overhang ... And, of course,
sound. Please note: after the muffler is worn in, the timbre and tone will
change slightly. Some sites have audio tracks on which the
"voices" of the mufflers are recorded. This will help you in choosing the most suitable
"by ear" muffler. The price depends on the quality of materials,
manufacturing technology , promotion of the company. In general, you have to walk around, look at the
windows and try consultants. Domestic mufflers made of
stainless steel, often surpass imports in quality and durability. Occasionally you
come across insanely expensive titanium products. There are
many types of mufflers .
The larger the volume of the muffler, the more efficiently the noise is damped.
Bass notes can be obtained not only by a straight pipe, but also by a sharp
increase in its diameter at the exit from the muffler. The synthetic fiber in the "can"
does not add power, but only suppresses high noises.
By the way, any serious interference with the exhaust system
requires adjusting the power supply system. Based on this, it makes sense to tune the
engine through the exhaust system, not least.
In the budget option, you can limit yourself to the terminal bank,
resonator and more advanced "pants". Replacing pipes with pipes of a larger
diameter will also give an increase.