Silencer create back pressure? skunk2 70mm

[hothatch]

I recently installed shorty header,test pipe,and 70mm catback.I went with the 70mm because i know one day i will turbo/sc my a3 instead of doing a engine swap.Anyway after i installed the new exhaust components it was REALLY REALLY REALLY loud,i mean holy fuck my ep3 sounds like the loudest jap crotch rocket ever made,really clean and powerful tone but its LOUD!!!!So i installed the silencer it comes with and it helped alittle with the volume.
Now i know that the bigger the pipe the slower velocity the air gets pushed out at low rpms and that equals less torque/power.Does the silencer create anymore back pressure and help out the loss of backpressure from using 70mm piping?

[v1c10us]

no.
You lose both worlds with the silencer.
because back pressure does nothing.
its EGV, exhaust gas velocity.
You have a big pipe with slow moving gas at low RPMS. and when you get up to like 7k, its great.
you clog it with a silencer and then you have a big pipe with slow moving gas that has more resistance on the end at low rpms, and at 7k you also have a bunch of back pressure so all that fast moving gas cant get out of the pipe as easily anymore.
You will get a small amount of scavenging due to the suction of the gas at the end when it exits the silencer, It moves slightly faster than the gas behind it and it creates a vacuum pulling that gas at almost the same speed of the gas that just exited, and then it speeds up when it exits, but its not gonna fix your problem thats for sure.

take the cardboard from a paper towl and tape the end shut, poke a pencil sized hole in it and pour water in it and blow it out and see how far it goes.
Now take a straw and blow water through that just as hard as before and it will go much further.
the silencer is adding resistance, not increasing flow throughout the entire piping.

[T_Virus]

Just get it dynoed with and without your silencer...you'll know...

[Princess]

5 hp this way or that way, don't worry about it

put the silencer in to protect your hearing and to keep ordinary people from hating Hondas with loud exhausts more than they already do...... if you go to the track you can take it out


there used to be a dyno on this site that said the a regualar Skunk2 catback got higher hp WITH a silencer than without

In a nutshell, who knows and who cares. The Skunk2 silencer is really designed intelligently from the looks of it.

[talonXracer]

no.
You lose both worlds with the silencer.
because back pressure does nothing.
its EGV, exhaust gas velocity.
You have a big pipe with slow moving gas at low RPMS. and when you get up to like 7k, its great.
you clog it with a silencer and then you have a big pipe with slow moving gas that has more resistance on the end at low rpms, and at 7k you also have a bunch of back pressure so all that fast moving gas cant get out of the pipe as easily anymore.
You will get a small amount of scavenging due to the suction of the gas at the end when it exits the silencer, It moves slightly faster than the gas behind it and it creates a vacuum pulling that gas at almost the same speed of the gas that just exited, and then it speeds up when it exits, but its not gonna fix your problem thats for sure.

take the cardboard from a paper towl and tape the end shut, poke a pencil sized hole in it and pour water in it and blow it out and see how far it goes.
Now take a straw and blow water through that just as hard as before and it will go much further.
the silencer is adding resistance, not increasing flow throughout the entire piping.


Exhaust flow is not a single continuous stream of air. It is pulsed and the introduction of some restriction is essential to low and mid RPM power. Very little driving is done at WOT unless you spend all your time at the track.

This has been PROVEN many times over with the Kseries!

I added a HF cat and had to ADD alot of fuel in the low and midranges, up to 18% in spots and only had to pull around 3% up top. I would trade the averaged 12% gains down low over the mediocre 3% gains up top without the restriction any day of the week.

70mm is way too large for even a cammed A3 IMHO.

[hothatch]

Exhaust flow is not a single continuous stream of air. It is pulsed and the introduction of some restriction is essential to low and mid RPM power. Very little driving is done at WOT unless you spend all your time at the track.

This has been PROVEN many times over with the Kseries!

I added a HF cat and had to ADD alot of fuel in the low and midranges, up to 18% in spots and only had to pull around 3% up top. I would trade the averaged 12% gains down low over the mediocre 3% gains up top without the restriction any day of the week.

70mm is way too large for even a cammed A3 IMHO.

but once i get my engine turbo charged wont i thank myself for getting that 70mm?

[talonXracer]

Yes you will, then the tone will be drastically reduced, but untill then you will need to endure the silencer.

[v1c10us]

Exhaust flow is not a single continuous stream of air. It is pulsed and the introduction of some restriction is essential to low and mid RPM power. Very little driving is done at WOT unless you spend all your time at the track.

This has been PROVEN many times over with the Kseries!

I added a HF cat and had to ADD alot of fuel in the low and midranges, up to 18% in spots and only had to pull around 3% up top. I would trade the averaged 12% gains down low over the mediocre 3% gains up top without the restriction any day of the week.

70mm is way too large for even a cammed A3 IMHO.

I cant tell if you quoted what I said to disagree with me or what, but there has never been one single ounce of evidence proving that back pressure is what gives you low end power, thats hot rod thinking.
the physics of it are really simple.

if a volume of air is moving through a pipe that is capable of holding more air than is moving through it, the molecules will bounce around inside of and lose their velocity, like air in a very large bag.
if the same air moves through a pipe that is smaller or the perfect size for its volume, all of the airs velocity must move in one direction, out, because the air is pushing against the piping which obviously isnt going to expand, so the exhaust gas moves faster, like air in a baloon that is stretched tight, if you let go, the air must exit the hole because it is pushing in every direction and the only way to go out is through the hole.
the reason you lose power when you've got a big fat exhaust pipe with slow gas in it is that the gas slows down in the pipe and when the piston tries to push the gas out of the cylinder, it must now move the slower air infront of it as well, creating alot more work for the engine, and that can be proven and has been proven.
Back pressure is a myth..

if you dyno the car with the silencer in and out you will see NO change
because the silencer, although speeding up gas at the very end of the pipe and creating a vacuum to suck out exhaust gas slightly faster, it is also making it harder for the piston to push the gas out and it is not making up for it by accelerating the exhaust gas.

edit: this is why HOTTER exhaust gas is faster exhaust gas. The hotter things get the faster their molecules move, excited molecules move faster, thus pushing harder, and expelling them selves from the pipe quicker, at ANY and ALL rpms, making LESS work for the engine. this is the exact same principle and has nothing to do with pipe size.

[talonXracer]

That theory and explaination is full of false assumptions and is based on old V8 analog controled technology. Any throttle position requires some restriction to maintain torque and proper cylinder scavanging.

On the Kseries the cam design, stroke, intake all enter into the equation now in a entirely different way when you dont have the forwards facing exhaust ports and the requesite two 90 degree bends. Hytech runs some of the most competetive K24 engines out there on the road race circuit, and they DO NOT use a 3" exhaust and add some restriction for a reason.

Not everyone lives there life a "1/4 mile at a time".

Here is a recent dyno graph of mine. The only changes between the two runs were the removal of the ultra non-restrictive DC sports single can with a Hytech loop muffler AND adding a platinum cat. Show me where the addition of restriction lost me power??? (except a short spike at 2800)
http://i54.photobucket.com/albums/g96/talonxracer/retunedynograph.jpg

[v1c10us]

i think we're argueing the same point..
you say live life 1/4 mile at a time blah blah
I'm talking about at typical RPM ranges such as 2-4k with occasional 5k rpm ranges.

you said there is a reason they done use 3 inch exhaust with a restriction on the end
and i was saying that 3 inch exhaust with a restriction on the end wont do anything
back pressure is completely pointless and is NEVER EVER needed.
restriction however IS
restriction in the form of an IDEAL sized piping
the molecules are trying to scatter and move very quickly inside the pipe and the pipe has no room for that except for out of the end of the tailpipe. so they speed out of the end.
a big pipe doesnt do any of this, there is no scavenging, there is no exhaust velocity there is nothing.
My point about adding a silencer on the end was that the gas at the VERY end of the pipe will move slightly faster, creating a vacuum or "scavenging"


edit to clarify: read the very bottom of your last post and realized you mis understood me. if you re read everything I wrote you'll notice that the entire time I am proving why smaller exhaust piping is better. I was attempting to tell you that "back-pressure" is a big ass load of shit and doesn't ever help an engine. there is more back pressure in a large exhaust full of slow exhaust than there is in a small exhaust with very fast moving exhaust pulses

[v1c10us]

this is also the same reason people LOSE power when they add a resonator.
the fast exhaust enters a larger area(the resonator) and all of its velocity is now able to push in every direction, instead of just out, and it fills the resonator. The assumption would be that the resonator freed up the air reducing "back pressure" thus causing a loss of power
when in actuallity, the resonator freed up the air causing an area of slow moving gas that had to be pushed out by the next exhaust pulse, the slow moving gas is the "back pressure" and it doesnt help anything.

if it was all about back pressure, hytech COULD just restrict the end of their 3 inch piping, but its not. back pressure has and never will do anything good for an engine, making the gas go FASTER by channeling it through a proper sized(and typically smaller atleast for daily driving)pipe WILL

[talonXracer]

Restriction and backpressure amount to the same thing. The restriction creates the back pressure. But I am not talking about a blockage, resonator etc, but overall dia in relationship to the CFM. It is measured in inches of vacuum. To actually measure it you drill and weld small 1/8"npt bungs along the exhaust to install nipples and take measurements.

Reading your last post indicates that you do not understand what back pressure actually is.


But enough of that...back on topic

You will gain some low rpm drivability back, ie a little torque. Not much but a little, but it will hamper top end a fair amount.

But will be very nice for a turbo setup without the silencer.

[v1c10us]

yeah, vacuum indicated scavenging and suction from the gas before it. back pressure would reduce this vacuum.
The entire word back pressure is a misconception and shouldn't be used.
if you had an overly restrictive exhaust the vacuum reading would be lower, but one would say that this is MORE back pressure, the methods for reading back pressure arent even valid
its physically impossible to create more resistance and get a higher vacuum reading, and pressure gauge would read less vacuum or more pressure the more back pressure you enduce.
its the fact that you have less BACK pressure and more forward pressure that creates vacuum which is ideal in an exhaust.
so unless every time someone said back pressure is good, they meant, back as in, towards the back of the car, then back pressure has never been good.
its velocity, and will only ever be velocity.

the restriction shouldn't be called a restriction because it is not.
by making the exhaust smaller you arent restricting it, you're channeling it faster.
Restricing it would be making it too small, so that the pressure inside is so great that the piston must push it out of the way, much the same as if the gas in the exhaust was not moving. Its all about having it go fast enough that the piston hardly has to push it out of the way on its exhaust stroke.

[T_Virus]

There was a thread on this before the crash...one guy dynoed with a silencer on and off...with the silencer on he gained a little bit of more torque but lower hp than without sliencer. with the silencer off he gained more hp than what he had with the silencer on but lost more low end torque...

[K20A EP3]

I have this exhaust to and the silencer quiets it down alot

[EPSU3]

I installed the exact same set up last year, but I bought the 60mm exhaust because I have only modest bolt ons and new 70mm was going to be too big for me. I use the silencer and it feels like i have more of a bottom end. I plan on replacing he test pipe with a h/f cat since I only use the car for daily driving and occasional auto x, so I dont need the high end at the expence of the environment.(I have a geoscience minor, so i worry)

[hothatch]

Well i took off the baffle today,i wanted to see how it was without and i think i like it better with the silencer out.The car seems to rev alot longer without losing power.Downside everybody (including my neighbors) problably hates me when i am screaming down the road ruining there quiet peaceful day LOL.I cant wait to get this o2 sensor in the mail so i can get this damn cel off and let my engine run properly and really see that this new setup can do.

[!@#$%]

my car was the one that dynoed higher with the silencer.

First run with it in.
2nd run took it out = entire lines went down across the entire range.
3rd run went back consistent with the first run.

Take this for what its worth. Not sure why it was peaking like that but it did.
http://img.photobucket.com/albums/v311/hondata7700/dyno1-1.jpg