Stock Muffler V.S. Customize Muffler

**finchy18** · February 4th, 2006 10:57 PM

what could be the possible result or damages if we change our stock exaust mufflers to customize mufflers just like now a days spoon type etc ..

**niky** · February 4th, 2006 11:17 PM

None, really. Malayo naman ang muffler sa catalytic converter. Basta maganda ang installation at walang leaks.

**finchy18** · February 4th, 2006 11:35 PM

Originally Posted by niky

None, really. Malayo naman ang muffler sa catalytic converter. Basta maganda ang installation at walang leaks.

kasi po what in my mind is stock mufflers merong box tapos iikot pa yung air at maliit lng yung exaust nya tapos yung big mufflers free flow na po.. di kaya magka engine problem or makakasira ng engine?

just curious lng po..

**niky** · February 4th, 2006 11:51 PM

Nope. The only exhaust mod that can negatively affect engine life are aftermarket headers... and then only if they're not wrapped in insulation, as the heat from headers can harm the rubber around electrical sensors in the engine bay.

The stock muffler lowers the sound of the engine by making the air slow down as it goes from chamber to chamber, before it exits the muffler. This creates backpressure, which robs the engine of some horsepower. An aftermarket muffler is usually straight through, and eases backpressure, thus giving you slightly more power, but it makes your car louder.

The only exhaust problems that can damage your engine are exhaust leaks at the exhaust manifold (outside air can get in and contaminate your oxygen sensors) or a cracked catalytic converter (catalytic particles can travel back up the exhaust into the engine and damage it... but this only happens on cars with the catalytic converter very close to the engine).

**pitbullz** · February 4th, 2006 11:55 PM

sabi nila kapag masyadong malaki yun buga eh mababawasan ng compression engine mo. ewan ko lang kung totoo

**niky** · February 5th, 2006 11:58 AM

Nope. Compression is not affected by intake or exhaust mods. Ang mawawala lang kung sobrang laki yung exhaust system ay ang backpressure, which help keep torque up.

A simple way of putting it: (HINDI ITO ACCURATE, GUESSTIMATE LANG!)

hypothetical 1.6 liter engine, 116hp, redline at 6500rpm

stock exhaust: 116 hp * 6000rpm / 110 ft-lbs torque 4000rpm
stock+muffler: 118 hp * 6000rpm / 108 ft-lbs 4000rpm
muffler+(1.75" inch)midpipe: 122 hp * 6200rpm / 107 ft-lbs 4200rpm
muffler+1.75"mid+headers: 125 hp * 6500rpm / 106 ft-lbs 4500rpm
muffler+2"mid+headers: 128 hp * 6800rpm / 100 ft-lbs 4800rpm
muffler+2.5"mid+headers: 130 hp * 7200rpm / 100 ft-lbs 5000rpm

Basically, the more horsepower you get out of the exhaust, the less torque. If you change your pipes to extremely large ones, the horsepower you gain will be beyond the usual rev range of your engine and will be mostly useless. Plus you shift your torque curve higher, meaning your engine actually feels weaker at low revs.

The generally accepted rule is 1.6 = 1.75 - 2" pipes, 1.6 SiR = 2 - 2.25" pipes, 2.0 = 2 - 2.25" pipes for best usable power. Not exactly sure on header measurements, but 4-2-1 headers give you less hp gain but less torque loss, while 4-1 headers are more preferred for dragsters. Original headers (DCX, Spoon, etc) will give you either more hp or the same hp as 4-1s and less torque loss, because they're usually dyno tuned.