Incorrect Silencer size can cause engine problems

**adammet04** · 25-01-2007 02:18 PM

Hi all,

as most of you know (or guessed) i have finally got the skunk2 exhaust installed

without silencers the car is loud and i love it, however the boys in blue probably dont (or the epa) , as such i fitted the silencers (supplied with exhaust)..

I want to discuss what the ramifications are of doing this, i have heard/been told the silencer will cause the following : carbon buildup in the engine and eventually engine failure..

I found this site as well which seems to confirm this.
http://www.eiwilliams.com/steel/inde...ngineSilencers

There are some equations on the above site so i might see if i need to do something about it.

This seems like an important topic and hence why i raised it, so many people with exhaust etc around (not a lot with silencers mind you). just seems like a valid thing to discuss (what with police and EPA crack downs on everyone with a modified car ATM)...

my questions for discussion

a) if the silencers that come with the engine arent the right size and my car engine dies, that might be the fault of the manufacturer of the exhaust for not supplying proper silencer?? ANSWERED

b) I know i can fit an extra resonator to the exhaust for sound reduction too. but maybe a corect size silencer might be better... thoughts??

c) I had a c question but forgot it..

**bungsai** · 25-01-2007 02:31 PM

few good questions there i cant answer any but suggest a few..

a silencer will generally reduce flow whilst a good resonator will not.

A silencer will also alter tone, whilst resonators tend to alter volume and not affect tone as much.

**adammet04** · 25-01-2007 02:36 PM

Thats good information mate

thanks

that maybe a reason to go for resonator as opposed to better silencer

**sivic** · 25-01-2007 03:09 PM

as for the first post:

a) there is no way you'd be able to hold the manufacturer of the exhaust responsible for any damage. I would imagine there are disclaimers etc.. plus you'd have a hard time proving beyond a doubt that it was the silencer which did the damage

as for damage to the engine - unless the silencer created more restriction than the stock exhaust i don't think you'd have anything to worry about

**JasonGilholme** · 25-01-2007 03:15 PM

I doubt it will causeyou any trouble unless the silenver didn't have an exit and just totally block the exhaust up.

**adammet04** · 25-01-2007 03:41 PM

a) fair enough

just wondering about the ramifications there.. updated first post to say answered..

b) ok so as long as the silencer has same or less restriction than the stockie , you think ill be ok..hmm what about the fact that the skunk2 is a larger diameter than the stockie, larger diameter, more air out, silencier = stock, then that more air cant get out as quick?

The silencer is not just a plug

**JasonGilholme** · 25-01-2007 03:46 PM

I know the sliencer is not just a plug.

The silencer will not restrict the flow as much as stock but it will reduce the flow a large degree.

Think about it tho. Other people have been using silencers on there cars for years and they haven't had any engine probs.

You'll be fine.

**adammet04** · 25-01-2007 03:56 PM

Originally Posted by JasonGilholme

I know the sliencer is not just a plug.

The silencer will not restrict the flow as much as stock but it will reduce the flow a large degree.

Think about it tho. Other people have been using silencers on there cars for years and they haven't had any engine probs.

You'll be fine.

I know you know its not a plug..my post wasnt too articulate, i meant that the silencer i have isn't a plug shape, eg no output

my bad !

exactly my thoughts about the silencer, surely this would have appeared along the way and im sure skunk2 wouldnt produce a shitty silencer for their systems ...

but two people have said to me, get a resonator as silencer will cause issues at over 3000rpm with car..

maybe they were referencing in regards to track work, etc,

idrive my car hard, but not track work hard ..

**JasonGilholme** · 25-01-2007 04:05 PM

I think you'll be fine. i know people that use them all the time.

I use one on my other car and have had them on cars previously and its cool.

Think about it though, why would the carbon build up happen in the chamber when theres all this force pushing the gasses towards the end of the exhaust system. you'd have a have a really big blockage (ie. a totally blocked muffler) to make the exhaust gasses go back into the chamber.

**aaronng** · 25-01-2007 04:52 PM

I don't think the problem comes from the carbon build up, rather from the exhaust gas pulses being forcefully stopped by the ring of metal which makes the exit hole of the muffler smaller. If the hole is much smaller than your exhaust piping diameter, it can causes the exhaust pulses to be messed up.

**vti_ek9** · 25-01-2007 05:13 PM

hurmmz....interesting.....does this apply to turbo cars aswell?
i've been driving around for about 2 years with silencer on....i feel it does restrict air flow but not so sure about damaging the engine?

**honest muz** · 25-01-2007 08:56 PM

Guys,
When i was riding a motorcycle on the road I think I went through some of Adammet04's questions, so let's see.

a) Any after-market pipe is probably illegal and probably doesn't meet the Australian Design Rules for your car. Quite separately, it wasn't part of the manufacturer's design or build so if anything breaks, it's certainly not the car manufacturers' fault. It may be the pipe retailer's fault, under the trade practices act, but not the manufacturer of the pipe (unless you bought directly from them.

It's likely illegal because it likely emits more noise & unconverted gases than standard. In motorcycle land everyone wants the same as you, a louder engine sound. You can add another pipe legally (in NSW) but it's got to have a Statutory sticker that shows that an acredited tester has measured the noise (@ 1 metre?) at the right engine speed for your car. The right engine speed is the one that the RTA says produces the most noise for your car. For my old pride and joy, that was 3,500rpm and the test showed it made only 90.9dB(a) of noise. Because the ADRs for bikes says it can't go over 94dB(a) then the combination of the after-market pipe and the Stautory sticker meant that the pipe was legal. Typically any pipe bender will be able to certify your pipe if you sumit it to test. Try Carline or similar.

Sivic is correct. It's not enough to have a burnt valve and claim it's the pipe's fault. YOU HAVE TO PROVE IT. Nearly impossible.

b) Exhaust design, gas flow, scavenging of unburnt gases is, ultimately, trial and error. Yep apply bernouli's equations or any other relevant modelling and you'll get close, but testing gets results. You'll need to check dyno tests (and interpret at the wheel, at the crank). To gain max. power / torque it's not simply a matter of having the most free-flowing pipe. Aarong got it Right, the pulses, standing waves, moving waves all contribute it good extraction. Any Honda from the EFI age is likely to have the best possible performance pipe installed at the factory......for the factory engine tune. But if you wanna make some noise........rock on.