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#Post#: 1621--------------------------------------------------
Re: Future Plans
DIR By: Kaotikkaos
Date: September 17, 2011, 10:21 pm
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--- Quote from: WRXog23 link ---
>
> Don't know if this is the correct listing to put this but I
need some advice.... I have a 2011 WRX Impreza and was told to
do a muffler delete and do straight piping.... any pros and cons
on this? will this void warranty and ultimately will I feel a
change in anything as in power, your help is greatly
appreciated.
>
--- End Quote ---
You can create your own thread ha. But man dont do that, Do a
Cat delete or hi flow cat to pass emissions and do a good
aftermarket muffler.... Straigtht pipe is just the easy way out,
lose back pressure...etc
#Post#: 1624--------------------------------------------------
Re: Future Plans
DIR By: Blakd
Date: September 19, 2011, 4:42 am
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Kaos is correct, if you go with a straight pipe you will need to
add the back pressure back to the system. With something that
is turbocharged already and has a decent header it will be hard
to get it back. Backpressure helps with torque and hp by
causing a fluctuation in the flow of escaping gasses. Think of
it like this. If a bullet is to small for a gun barrel the
explosion from the powder would travel around it causing it to
loose distance. But if you use a bullet that is to large then
the gun might just blow up in your hands. A cat delete or even
putting a straight pipe with a choke point in it would be the
best situation. To get the choke point you would have to have a
custom setup designed and it would cost more than it it worth.
Since I know people will read this a say I am full of crapola.
I will add a little more information. People state that
backpressure is bad because it causes the exhaust valves to work
harder and restricts the flow of the gasses. People will state
that the changing of air fuel mixture by a computer is better
than backpressure, but what happens to all those escaping gasses
and unburnt fuel without backpressure. Remember the flames
coming from the cars in the fast and furious movies. Straight
pipes make for good flame throughers.
On a side note, my wife and I are going back down to one
foster child due to behavioral issues with one of the two we
have. So I should be able to start work on some of my projects
here very soon.
#Post#: 1625--------------------------------------------------
Re: Future Plans
DIR By: WRXog23
Date: September 19, 2011, 7:17 pm
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Thanks for all the information! Glad I didn't decide to make a
move that soon
#Post#: 1626--------------------------------------------------
Re: Future Plans
DIR By: MBDark
Date: September 20, 2011, 12:12 am
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The turbo is already adding backpressure to the system, after
that you want the exhaust to get out as soon as possible. A
strait pipe is the fastest way to do this, but you won't pass an
inspection to save your life. With that said, WRX's and STI's
sound sick with a dump pipe, used to run one on mine, but a cat
back and a nice exhaust will give you a much more "legal" sound
level, and still let you pass inspection. On an N/A car,
backpressure is important to a degree, on a turbo'd car you just
want to get the exhaust out as quickly as possible, which is a
strait dump pipe with no cats and no exhaust.
#Post#: 1628--------------------------------------------------
Re: Future Plans
DIR By: Blakd
Date: September 20, 2011, 4:54 am
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Wow. Thank you MBDark I totally missed that this was for a WRX.
WRXog, MBDark is right if you want an exhaust it would be best
to do a high flow system so you will still be street legal.
#Post#: 1630--------------------------------------------------
Re: Future Plans
DIR By: Rob1796
Date: September 20, 2011, 10:20 pm
---------------------------------------------------------
--- Quote from: Blakd link ---
>
> Kaos is correct, if you go with a straight pipe you will need
to add the back pressure back to the system. With something
that is turbocharged already and has a decent header it will be
hard to get it back. Backpressure helps with torque and hp by
causing a fluctuation in the flow of escaping gasses. Think of
it like this. If a bullet is to small for a gun barrel the
explosion from the powder would travel around it causing it to
loose distance. But if you use a bullet that is to large then
the gun might just blow up in your hands. A cat delete or even
putting a straight pipe with a choke point in it would be the
best situation. To get the choke point you would have to have a
custom setup designed and it would cost more than it it worth.
>
> Since I know people will read this a say I am full of crapola.
I will add a little more information. People state that
backpressure is bad because it causes the exhaust valves to work
harder and restricts the flow of the gasses. People will state
that the changing of air fuel mixture by a computer is better
than backpressure, but what happens to all those escaping gasses
and unburnt fuel without backpressure. Remember the flames
coming from the cars in the fast and furious movies. Straight
pipes make for good flame throughers.
--- End Quote ---
Your theory is wrong, but you'll get the right results, so I
don't know if I should correct you or not...
Hrm.
#Post#: 1631--------------------------------------------------
Re: Future Plans
DIR By: MBDark
Date: September 21, 2011, 2:10 am
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I already corrected him on the last page, all is good lol.
On a Turbo'd car your exhaust should be as open as possible, on
a NA car your exhaust needs "some" backpressure, but in most
cases you will get enough just using any exhaust at all, and it
can also just be tuned around.
#Post#: 1632--------------------------------------------------
Re: Future Plans
DIR By: Rob1796
Date: September 21, 2011, 3:02 am
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Eh, I already typed it, lulz.
[quote="Sayeth You"]Kaos is correct, if you go with a straight
pipe you will need to add the back pressure back to the system.
With something that is turbocharged already and has a decent
header it will be hard to get it back. Backpressure helps with
torque and hp by causing a fluctuation in the flow of escaping
gasses.[/quote]
In a NA system, you are correct in thinking that go with a wide
open flow, you are loosing lower end torque in sacrafice for
higher end power. In a race car (as in, race built), going with
wide open exhausts isn't a problem at all because race car.
Actually, it isn't a problem at all because they spend the
majority of their time higher in the rev range, turning over
faster, and pumping out more air.
But it is not back pressure that helps with torque. Back
pressure is bad. It was in the past, it is now, and it will be
in the future. Back pressure is like the dark side of the
Force. It helps nothing, hurts everything, and is often used by
those who do not understand it. Any fluctuation in the flow of
gasses escaping on the exhaust side of the motor is bad. You
are confusing back pressure with this awesome thing known as The
Scavenging Effect. No, the scavenging effect is not like the
light side of the Force. The scavenging effect is more like an
old martial arts movie. Its Kung Fu is strong.
Ok, on a more academic note, here is what happens. The engine,
as we all know, is a massive air pump. It sucks the air in,
mixes it up, blows air's **** up, and spits it out like a bad
piece of chicken. Suck, squish, bang, blow, or if you are more
mature than I, Intake Compression Ignition Exhaust. What we are
interested in here is the exhaust (or blow) part. After the
ignition part, you have spent air in the cylinder. This spent
air poses two problems. Problem the first is that the air is
taking up valuable space that is needed for incoming air, like
those hippies that moved into my parents neighborhood. Problem
the second is even if there wasn't a space issue, that air in
the cylinder has been used up, so it is less likely to ignite,
unlike those hippies that moved into my parents neighborhood.
So you need to get that air the **** out. Porkchop sandwiches.
If your exhaust outlet is too small for the amount of air the
engine has the ability to push out, you have back pressure.
Back pressure causes the engine to work twice as hard, because
now it has to push the air already out even...more out...and it
also has to push the air in the cylinders out as well. So this
is where you take your car, toss it in the air, falcon punch it
till the stock exhaust falls off, and put on a bigger exhaust.
However, you went too big, say, 3 inches on a itty bitty four
banger with no head work and stock cam(s). So you get to that
blow cycle, and, well, nothing happens, the air just sits there.
The air is a dirty, lazy bum looking for a hand out. So, in a
situation similar to back pressure but not quite, the engine
pushes the air out, but it still has to push inefficiently
because there is nothing helping the air out at lower RPM. This
is where you get that loss of torque, because as the engine is
under worked to push the air out, it doesn't create a suction
(TEST HINT: SCAVENGING AND SUCTION BOTH START WITH THE LETTER S)
in the cylinders to pull more air in, and pull more air out of
the exhaust side into the exhaust.
So this is where you figure out that you ****ed up with your
nine thousand inch exhaust on your Toyandissan Camcordima, and
go out and get one made up at a custom shop that is more
properly sized for your application. Now, when that exhaust
cycle comes along, your engine is pumping out the exact amount
of air that can fit in that exhaust with just the smallest
amount of open space possible. What happens? A vacuum is
created. This vacuum acts on the exhaust side of the engine
during the blow part of operation, SCAVENGING (see, told ya they
both started with S) the spent exhaust gas in the cylinder. Or,
in other words, it sucks the air out of the cylinder on the
exhaust side, allowing the engine to operate closer to peak
efficiency.
Now, why is this important on an NA car, but not a boostmobile?
Simple, that turbo is a dirty little **** that can blow all god
damned long. The NA motor, on the other hand, is a decent girl
who has a bit too much to drink, and think she has what it takes
but after about six minutes, she's drooling, your embarrassed,
and well it just wasn't a great evening. In other words, the
turbo can theoretically flow an unlimited amount of air. Sure,
you run into the efficiency of the turbo and the compressor map
etc, but really, the turbo can keep spitting out all the air you
shoot into it. The bigger the exhaust, the better because the
turbo will just spool up and keep tossing out air. The NA motor
on the other hand can only flow so much air. Even if you do
gobs of headwork, jack up the compression, add some nasty ass
opening drum solo of Hot for Teacher cams and the like, your
motor can still only flow so much air, so your exhaust tuning is
important.
Now, why don't we see so much more about this? Well, simple. 1
- peak exhaust sizing is hard. An exhaust company can't keep
all sorts of sizes of pipe laying around, 2 and 59/72nds inch
pipe is uncommon as hell, and due to atmospheric and
environmental conditions, most cars are going to have small
variances in their best air flow on the exhaust size. 2 - Most
people don't know that back pressure equals bad, and also don't
know about flow testing and air volume and the like. They just
know that a three inch exhaust on their 1.6L four pot made their
car feel slower down low than the 2.25 inch exhaust.
And that folks is why back pressure is always bad. It will
always cause the engine to work harder to push out the same
amount of air, and reduce the ability of the engine to spin
faster. It is never good, does not "create torque", and in the
end just sucks gigantic AIDs infested Albino Tijuana Aligator
****.
[quote="You still Sayeth"]Think of it like this. If a bullet is
to small for a gun barrel the explosion from the powder would
travel around it causing it to loose distance. But if you use a
bullet that is to large then the gun might just blow up in your
hands.[/quote]
Ok, this is just as bad, because my second hobby after cars is
guns. See, I can see where you are trying to go with the
example here, but it falls short in a number of ways. First, an
engine is only trying to move air. The firing action of a
weapon is trying to move a solid projectile. The only time the
engine needs to move a projectile is if we stuck an orange in
someone's fart can and didn't tell them
Second, while you could compare the movement of air in an engine
to that of a bullet in theory (air goes in, bullet goes in.
throttle is pressed, trigger is pulled. air goes out, bullet
goes out), it falls short as well. The engine mixes the air
with fuel and provides the spark. The round of ammunition, on
the other hand, is a self contained unit. It contains the air
(bullet), fuel (powder), and spark (primer) in one package. The
air coming into an engine does not contain its own fuel and
spark.
Finally, the first half of your comparison is right. If the
barrel is too big for the round, then the expanding gasses from
igniting the charge will go around the bullet. The second half
is right to the point where big bullet itty barrel will **** you
up, but a car will still flow with an itty exhaust.
You also face the problem that an engine is an air pump, a gun
is not. But kudos for trying. F+.
[quote="You last Sayeth"]Since I know people will read this a
say I am full of crapola. I will add a little more information.
People state that backpressure is bad because it causes the
exhaust valves to work harder and restricts the flow of the
gasses. People will state that the changing of air fuel mixture
by a computer is better than backpressure, but what happens to
all those escaping gasses and unburnt fuel without backpressure.
Remember the flames coming from the cars in the fast and
furious movies. Straight pipes make for good flame
throughers.[/quote]
Back pressure is still bad, even this far into the argument.
What happens to all that unburnt fuel without back pressure?
That unburnt fuel still dumps out the exhaust valves, hits the
super hot headers or ever super hotter downpipe, ignites, and
shoots out some nice fire. You don't often see that fire
because most of the time it gets stopped in the catalytic
converters, and let me tell you those cats don't. ****ing.
Like. Fire. You'll blow out your cats super fast that way, no
matter if we are talking the furry purry kind or the ones on
your car that let you pass some draconian form of smog
enforcement. The reason you get that nice little flame shooting
out the back of the car is because we don't get a uniform
standard of gas. The fuel we get has different additives, may
not be 100% at the stated octane level, and may or may not have
ethanol added in. As a result, most tuners tune a little on the
rich side, sacrificing power for safety. This gives you the
pretty fire balls.
The cars in the F&F movies shot flames because they stuck spark
plugs in the exhaust pipes, cranked up the spark, and lit the
exhaust gas. That is why they were only shooting flames when
they were mashing the loud peddle. If your car was tuned so
rich that it just shot flames constantly while you were
accelerating, you are either in a B Sci Fi movie, or a really,
really bad place, and you would measure consumption in gallons
per mile.
TL;DR - Back pressure is bad, scavenging effect is good, and
when they say the chick boulin is bad, they aren't kidding. I
think I just shat a chicken, a lung, or a chicken's lung. But
really, read all the above, it isn't that long, and if you think
it is, your attention span is not safe for driving a 3000+ pound
missile filled with a flammable accelerant at 75 miles per hour
in the public domain.
Oh, and 2 59/72nds= 2.819444444444444444444444444
#Post#: 1639--------------------------------------------------
Re: Future Plans
DIR By: MBDark
Date: September 23, 2011, 1:06 am
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TLDR
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