what exactly does a muffler do??

[ESPER]

is it for looks? sound?? i see some modified cars that have NO muffler and instead just have a pipe. since i have an intake would taking off the muffler add more HP, would it still be ok??

thanksto those who reply!!!

[themadscientist]

well it muffles the sound, more recently it can shape the sound. It is not any better to have a muffler from a performance standpoint, only noise suppression and legality.

[lessthanjakejohn]

Its to make it quieter. But sometimes it can put the sound in a frequency that is intolerable to your ears (physically)

Companies will usually adjust their mufflers to a sound that they want.

If its legal, then no muffer would be the best, A (insert dia here) that shoots off the header and under the door would provide the least restriction possible while still keepng the fumes and some heat out of the car.

[ESPER]

so if i remove my muffler than, it will be louder, but i should get increased top end power shouldnt i?? cuz now i got less restrive flow?

[lessthanjakejohn]

You should have higher power throughout the power band

[lessthanjakejohn]

keep your muffler, Get a borla one.

everyone willhate you and think you are stupid, annoying, and well...

[nissanrcer240]

Quote »so if i remove my muffler than, it will be louder, but i should get increased top end power shouldnt i?? cuz now i got less restrive flow?[/quote]

yeah it will be real louder, i had to drive home w/o a muffler b/c the piping was too long when i put my exhasut system on a couple weeks ago,i couldnt put my foot on the gas if a cop was around b/c i was scared i was gona get pulled over, thats how loud it is

[karttoon]

I was wondering this also, so having a bigger muffler isn't any different then a stock muffler? I think those mufflers look retarded :/ and are to deep sounding, I like mine the way it is. BUT, if it does increase performance having a bigger one I suppose I'd live with it :P

[lessthanjakejohn]

hmm, not necesarily and the gain would be vary little for the price. The only way i can justify buying a muffler with out replacing the entire system would be for sound, and i dont care about that

[Red Lightning]

On a CA18ET, if I run high flow cat and no muffler, would it be really loud? Cus the turbo should muffle the sould somewhat right?

[lessthanjakejohn]

try it without and then put on on if you need it. You can always cut off pipe but its hard to put the pipe back on.

[Nathan]

You could put a glasspack on...they are cheap and it'd muffle it a bit.

[themadscientist]

aftermarket mufflers increase flow by larger pipe ID and by using as few tight bends as possible. On NA cars you can't just grab a huge pipe though, if it is too big you will lose a whole bunch of low end grunt without enough backpressure. Turbo cars can go huge without detriment.

[NiSilS14]

on turbo cars, if going too big of a pipe Diameter. wouldnt you lose a bit of spool up on the turbo?

[lessthanjakejohn]

aftermarket mufflers increase flow by larger pipe ID and by using as few tight bends as possible. On NA cars you can't just grab a huge pipe though, if it is too big you will lose a whole bunch of low end grunt without enough backpressure. Turbo cars can go huge without detriment.

back pressure is never good

[themadscientist]

wrong, backpressure is beneficial to a certain point on NA cars to enhance torque. Selecting the right exhuast for NA is important. Things like header pipe size, lenth of the runners, collector arrangement, main pipe size on the exhaust pipe and muffler design all impact where you are making power and how much you make. Running an 80mm exhuast on on a KA24 for instance will give you a big HP number at wide open throttle in top gear but it will take the car forever to get to that point because with no backpressure to keep the fresh charge in the cylinders during overlap on the cams you car will actually be slower from a stop than a stock mufflered KA.

[themadscientist]

on turbo cars, if going too big of a pipe Diameter. wouldnt you lose a bit of spool up on the turbo?

It would help if anything. Being after the turbo, removing any restriction will keep the turbo flowing as freely as possible. A restrictive exhuast will cause the turbo to spool slower because it can't flow to it's maximum potential as the exhuast is jammed up in the pipes after the turbo.

[lessthanjakejohn]

wrong, backpressure is beneficial to a certain point on NA cars to enhance torque. Selecting the right exhuast for NA is important. Things like header pipe size, lenth of the runners, collector arrangement, main pipe size on the exhaust pipe and muffler design all impact where you are making power and how much you make. Running an 80mm exhuast on on a KA24 for instance will give you a big HP number at wide open throttle in top gear but it will take the car forever to get to that point because with no backpressure to keep the fresh charge in the cylinders during overlap on the cams you car will actually be slower from a stop than a stock mufflered KA.

Runners, headers, collectors all serve a purpose and determine the charateristics of the HP curve. (what you said) but that wasn't what I was talking about. Also, I understand that the correct size for an exhaust depends on a number of factors. I didn't mention anything about a bigger exhaust meaning less backpressure. I would dare to say that larger than 65mm or 2.5 inches on a KA or just about any 4banger would lose power, Especially at the low end where the engine is not cycling enough air and fuel through to provide adequate airspeed, therefore it increases backpressure. Running no exhaust while at first seems like a great idea is not so on the inside, because the exhaust can't provide the scavenging effect that the exhaust provides. You say that the back pressure will hold the fresh air in? well if there is back pressure how is the exhaust gas supposed to excape in the first place? What you said sounds contradictory.

What I have just said is what I understand to be true. If you think elsewhere please prove the points that I have made wrong and explain why "backpressure to keep the fresh " is right.

[themadscientist]

That's why I emphasis "to a certain point" You need just enough to keep the fresh intake charge from being sucked clean through the combustion chamber but not so much that you choke off the engine in the higher RPM range. It's a careful balancing act. There is no doubt that the stock exhuast is too restrictive but aftermarket replacements should be selected carefully for the reasons I illustrated. The turbo provides more than enough backpressure on the bottom end before they spool up so we can stick the biggest exhuast that will physically fit the car.To illustrate futher I can relate the story of how I learned this.

My first Skyline had a rusty exhuast system so i tore the whole system out and welded a 19" Cherrybomb glasspack where the cat went. It sounded mean but the car was way sluggish of the line, kinda of like a really dirty air filter and it would pop really bad. My intake charge was going right out the muffler and i was losing low end power because of it. Now after the twenty minute wait to hit the penthouse powerband I had given it it felt like about 10hp extra because the RPMs were high enough that I could use the insane flow but the car was totally anemic until about 4000 rpm.

[AZhitman]

John, TMS is right - Typically the "illusion" of increased power comes from all the racket and the fact that you just spent $300-600 on the latest "fartcan".

My 68 GS required VERY careful tuning of the exhaust - I switched pipe diameters from 2.25 to 2.75" and LOST .3 in the 1/4. Switching BACK to 2.25's with a crossover pipe and a quieter muffler put me .3 better than stock, or a gain of .6 better than the big pipes.

Backpressure to a certain degree is good -Especially in a car that is lacking in torque to begin with.

[lessthanjakejohn]

we can stick the biggest exhuast that will physically fit the car.

hmm, I don't think so. Believe me, if a 20 inch exhaust was best, wouln't you think Ferrari(Porsche actually:D, ferrari doesn't have many turbos, any?) would accomodate?

19" Cherrybomb glasspack where the cat went

about 4 inches wide? NA skyline? Agian your car was not going slow because there was no backpressure. It was a lot of backpressure causing the problem.

[corn322]

as I understand it, backpressure is not your friend. yes, as themadscientist put it, you need some backpressure to keep your fresh intake charge in the cylinder. but on a n/a vehicle, the important thing is exhuast velocity. too big an exhaust pipe and your exhaust will loose temperature and slow down, causing lots of unhealthy backpressure. just eh, correct me if I'm wrong, I guess.

[lessthanjakejohn]

John, TMS is right - Typically the "illusion" of increased power comes from all the racket and the fact that you just spent $300-600 on the latest "fartcan".

I think i would kill myself if i realized that I had just bought the latest fartcan.

[lessthanjakejohn]

your fresh intake charge in the cylinder.

I still find this contradictory. If your moving extra air through the cylinder all the better. If you have some backpressure that is supposed to keep the air in there, then how is the air going to get in there in the first place?

[Cyberkreig]

It is my understanding that smaller pipes are required for N/A motors.. But the explanation of fresh air in the cylinder doesnt make sense to me.. If you have "zero" backpressure.. and (for example) 3 Cubic Inches of air rushes past the exhaust valve, wouldnt those 3 CI be replaced by air moving at the same speed on the intake side?

[lessthanjakejohn]

yes that is part of what i am trying to say, but there is hardly time for much air

Also during over lap time the exhaust valve is not fully open.

"0" back pressure isn't ideal. You want the gas rapidly escaping through the tail, therefore bringing more air through the intake.

[themadscientist]

with adequate backpressure to prevent the air from just flying through the combustion chamber and out the exhuast the column of air will actually force more air into the cylinder than if it just trapped whatever was left in there when the exhuast valve fully closed. than denser charge of air in the cylinder will then create more power.

[SilviaLuvr]

IT MAKES HONDAS SOUND LIKE REAL RACE CARS!!!!!!!!!j.k j.k :pface

[MrFox]

if increasing backpressure increases torque and power (in your powerband, where it matters), than your cams overlap too much.

you are increasing the overall flow resistance of the system to compensate for charge spilling over during excessive overlap.

adding backpressure for tuning is a "poor" way to tame a too wild cam grind.

then in the real world, you can't go and try 50 different grinds till you find that perfect one. so i should say that backpressure is a "poor-mans" way to tame too much overlap. (i.e. me and most everyone!)

[Eklectrick]

I'm trying to see if I understand this. with zero backpressure, air will flow more freely, but it won't be as dense and won't give you as much of a detonation because the denser the air the better right?