Question about high flow cats

[dsp26]

wouldn't getting rid of a resonator would result in the same gains? as you are freeing up restriction + you get a louder sound and if defected it is easy to put back on?

resonator is not a restriction as it is a straight through.. it's pretty much a cannon mid pipe.

aka HotDog resonator... think of the middle section as a hotdog and the actual barrel a soft bun that muffles sound

[fadz]

^^it's not a benefit to anyone period!!

a high flow metallic cat is more beneficial.. why?
- They get red hot and burn rich unburnt combustion
- While burning, it will not shatter during exhaust pop like ceramic cats
- ignition of the unburnt fuel in the cat will keep the exhaust flow hot
- hotter exhaust flow = higher combustion gas velocity
- higher velocity = better scavenging effect of the exhaust system over the cylinders that have just completed the 4th stroke (exhaust cam open and gases being expelled into extractors) while the higher velocity gas in the rest of the system 'pulls' these out.

and yes it is very easy to detect a cat-less car... why?? it smells VERY eggy.... and cops do know this... people should just stop talking the shit and follow the rules. simple!!!

the only place your allowed to be catless is at a race event like drags or track... and msot high performance cars that actually benefit from not having a cat are not road legal and have to be towed to the event anyway.

if you read the first part of the thread, you would of known what i was talking about...i didnt at any point talk about not having a cat
i asked about the inside of the cat...the spider web looking stuff.

[DLO01]

wouldn't getting rid of a resonator would result in the same gains? as you are freeing up restriction + you get a louder sound and if defected it is easy to put back on?

resonator is not a restriction as it is a straight through.. it's pretty much a cannon mid pipe.

aka HotDog resonator... think of the middle section as a hotdog and the actual barrel a soft bun that muffles sound

A resonator is a restriction. Once the exhaust fumes open up to a the wider resonator (yes it has a straight through mid pipe with holes) turbulance is created causing resistance therefore restriction.

Anything thing to do with flow physics other than the same continuous diameter pipe is a restriction.

[dsp26]

A resonator is a restriction. Once the exhaust fumes open up to a the wider resonator (yes it has a straight through mid pipe with holes) turbulance is created causing resistance therefore restriction.

Anything thing to do with flow physics other than the same continuous diameter pipe is a restriction.

the physics u speak of is the truth no questions asked!!

however, in a straight through hotdog resonator... the loss is negligible to none. directly behind those holes in the straight pipe inside the resonator body is very thick muffling material which provide a very big restriction. but also being softer in those spots, absorbs vibration/noise from exhaust velocity.

but then thats where its flow characteristics are debatable. a cheaply made resonator will not have sufficient packed muffling material therefore will create turbulance and poor muffling...

law of physics also dictates that air will follow the path of least resistance.... and that is the "straight through pipe"...

[dsp26]

^^^hhmmm.. doesn't explain what i need it to explain.. i'll wait for someone to fix/correct it.

sorry DLO01 i'm not arguing for the sake of it coz what you said above well and truelly applies to spiral core resonators

[DLO01]

Thats ok man. All right info is good info.

[muhhan]

Physics aside, I wonder what the dyno (real dyno, not butt dyno!) says about having a resonator vs no resonator and cat vs no cat? Anyone have experience/printout?

[DLO01]

On the dyno, no resonator is better. Thats what I was basing my thoughts on.

[dsp26]

Physics aside, I wonder what the dyno (real dyno, not butt dyno!) says about having a resonator vs no resonator and cat vs no cat? Anyone have experience/printout?

on VERY high performance cars its different hence why they gain from not having on... especially hi performance big boost cars.

it's a matter of trying to match inlet/outlet pressure... in the case of a big boost car, you want as little restriction in the exhaust otherwise you backpressure as a result of too much air going into the combustion chamber and it can't expel it, which is obviously bad on big boost.

if my exhaust was say 3inch mandrel header back on a pissy 1.6l and can outflow the intake of air despite combustion chamber vacuum then it is not matched, then it's a case of massive bottom end loss for marginal top end gain.

However, the above 2 paragraphs can be slightly offset/tuned with camshaft specs, set timing, and overlap adjustment to time when both inlet/exhaust valves should be opening/closing.

the power loss on a straight through is negligible as most of you know already, it doesn't actually do much to reduce dB, but rather do it's job as a 'resonator' and change the tone to something deeper which is a result of design.

a spiral core resonator on the other hand will increase backpressure and provide massive turbulance as part of its design to actually muffle exhaust flow. this is why:

^^taken from http://www.dieselmanor.com/exhaust/i...-resonator.htm

and...

^^^taken from http://www.team-integra.net/forum/di...g+Common+Topic

Much like loudspeakers, anytime you have a rounded shape with sound coming out, the sound will be encouraged to wrap around the radiuses, coming right back into the car's interior. Just like airflow, sound doesn't like to negotiate sharp edges.

I put a Moroso spiral flow (3") on the Civic and the ITR about a month ago. They're placed in the system just like a resonator about mid-car. These things have made the Civic embarrassingly quiet and the ITR's so quite I can't hear the exhaust well enough to shift it by sound. We haven't tested these things on the dyno yet, but they do introduce out-of-phase noise to the main flow (in the center) and they're amazingly effective. They're 4" in diameter (for a 3" system) and they're cheap as hell.

[dsp26]

^^^If anyone actually bothered making a cannon muffler design like the above spiral core resonator it would sound awesome on it's own... however i'm pretty sure there are in oval muffler designs, just not cannons for some reason.. or i've never seen one...