Bit despondent today. Took the Alfa into an exhaust workshop and found both my centre muffler and rear are stuffed. $300 to sort it out (pretty reasonable I thought but not an expense I had budgeted for). Up on the hoist I noticed the car has a small front 'muffler' close to where the single exhaust starts. My car is an 85 2.0 GTV is this a catalytic converter? Regardless of what it is can this be removed without too many issues/etc. Any opinions greatly appreciated.
i replaced my centre muffler with a "hotdog" which will give a bit better flow (had to tell when the original baffle had broken) & made it sound much sexier!
not sure what the general concensus is, so i'd be interested to see what other options/opinions are.
Pretty sure that front one is indeed a muffler, not a cat. Could be wrong though.
For a similar price i had a system made up a couple of years ago. One large muffler where the center muffler sits and one at the rear of the car, after it goes over the driveshaft. Sounds good and is pretty quiet, 2 inch pipe the whole way. (It actually sounds a whole let better after i smashed the crap out of the center muffler rallying it a few weeks ago, not sure why but not complaining :))
Younger brother's Alfetta runs what i think is the standard exhaust, except it has a hotdog in place of the rear muffler. Sounds bloody good but far too loud for me to live with everyday.
For a standard car i wouldn't go any bigger than 2 1/4". I think it starts to sound too droney, and there is nothing to be gained in terms of performance.
Thanks for the speedy replies guys. My pipe work is sound so I will be keeping that stock just the two main mufflers are stuffed. My thoughts at the moment are - ditch the front small muffler (about 20cm long and fat) and two new mufflers - could they both be 'straight thru' designs or would this be to loud? Maybe just the rear straight thru as you suggested Mat or as Scuzzy suggested maybe the centre is a better option?
Has anyone fitted two 'straight thru/hotdog' style mufflers before - if so I would love to hear your advice - thanks again guys!
G'day,
To answer your q's, its not a cat, it can be removed without problems if you dont have an originality fetish.. ;D
Thats good news - off she comes then!
The small front "muffler" is not a muffler. It's a resonator and is intended to end the tuned length of the factory fitted system. It should remain.
Sounds important then! She stays! Unless someone else sways me with an alternative view - I am easily swayed!
Don't sway away from MDs advice.
MD; any chance of further explanation? I gather by removing it the flow of gasses will be upset, having some form of adverse effect right the way back through the engine?
I'm also guessing that fitment of extractors would have another effect, (hopefully not a negative one), and consequently the resonator would become redundant, given that the airflow has been modified before it would reach the resonator?
mat,prova.
Even a factory exhaust system,especially Alfa ones are part of a compromise for road tuning. This is to achieve as early torque as possible and mid rev torque at worst. To do this, there are basically three stages of a street car exhaust system. The primaries (headers) the secondaries(engine pipe) and the balance of the exhaust to satisfy
legal constraints for noise.
The combination of the first and second stages together with their respective bore and lengths form a "tuned " length that delivers this target torque as previously stated. For the tuned length to have a specific length, the resonance needs to end somewhere. It does so at the resonator. So this little black duct helps you get the factory intended torque band. If you remove it you are upsetting the resonance length of the second stage.
For other torque bands at different RPM ranges, different bores and lengths of pipes are called for but the principle remains when it comes to the end of the tuned length.It can be a muffler or a resonator but it needs to be located at the end of the tuned length. Fitting a "hot dog" where the resonator is or in place of it is quite ok. However do not simply by pass it with a piece of exhaust pipe as the gases are not expanding when they need to.
I hope that clarifies the reason why these seemingly useless things are installed. :)
Great info and insight MD. Could a possible solution be to replace the front reasonator with a hotdog style muffler, omit the centre muffler and obviously keep the rear?
Maybe I am just complicating things - go simple and fool proof - keep the reasonator and just replace the knackered mufflers maybe one of them with a straight through design. I will probably get the work done tomorrow afternoon so thanks for all the input!
Point taken, Mike. Although practically I cant say i've noticed any difference after deleting the resonator on a stock Alfetta, other than a slight increase in exhaust note..
Good point Martin. I wondered in real terms if the removal of the reasonator would actually make a noticeable difference. I think tomorrow its going to be a gut feeling decision on these matters I will let you know how it turns out.
fwiw- a hotdog with only one muffler would be too loud for me... for a road car..
Excellent as always MD.
just to round off..modern cars put cats where the resonator used to live. this does both jobs. not strictly correct but I'll slip it through and see who trips me up.. :) :)
Quoteyes that front muffler is a resonator and it has nothing to do with the tuned length of the exhaust or how that affect the torque curve
QuoteM.D. is right the length of the pipe does have an affect on torque but on an 85kw alfa your not going to notice it
Glen, you got bob going each way here. Wanna clarify your position ?
BTW1 Everything in this world has a resonance.
2 A tuned exhaust system is a SYSTEM and the so called headers are but the first stage of this system.
The only time the resonator has no impact on the system (however small) is when some bird brain installs it outside of its tuned location. Try playing middle "C" in "F" sharp. Somehow it sounds wrong that's because middle"C" has a specific length with respect to the piano wire intended for this note. The correct resonance produces the correct note. The correct resonance between the induction side and the exhaust side produces middle C for want of a better decription. Altering either the induction or the exhaust lengths can produce either less power than possible (de-tuning)or move this power to a different rpm range (peak tuning) but less usable for general road use.
This is a huge topic and so I will end here.
Thanks for everyones input on the exhaust query. I kept the front resonator, fitted a straight through muffler in the centre and a hotdog in the rear - great job and only cost me $250 with a two year warranty. Sounds good - no nasty vibrations - really happy.
So is the resonance the same as harmonics on a (guitar etc) string?
Only if you use the G string.. ;D
Hey Sheldon, your avatar has fallen off. Too many burn outs in the 90 ? :)
Who's Bob?
its not a cat cut it ou its just in the way get two 15' hotdogs mounted in there they need to be spaced off centre and uneven to prevent a yucky resonance i think thats how its spelt. those muflers cost about $80 each so not to expesive for you. good luck with the pong system!
Quote from: sportiva on May 18, 2010, 06:11:51 PM
frequencies are sound waves, short waves have a high pitch long waves low pitch
the sounds out of a trumpet are caused by the breath to push air through and by the player buzzing their lips as they blow, the trumpet also amplifies the sound
harmonics are when two frequencies or more align with each other as in two singers two guitar strings or two alfas together at the same revs, the combined sounds oscillate around each other giving that distinctive sound that you can hear and in the case of the cars you can also feel
Well I'm no musician, but I would have thought that "when two frequencies or more align" would more accurately be described as 'harmonies'. As far as I'm aware, harmonics are quite different. But I'm no musician.
I was talking about when you place your finger on (but don't press on it, just lightly on it) a guitar string exactly halfway between it's mounting points, or the 12 fret I believe it is (its been a while) and pluck the string you get a wonderful 'resonant' sound. From memory you get similar sounds, but at a different frequency, at the 5th and 7th fret. (Some of that may be inaccurate, It's been a while since I picked up a guitar, and I only did it to pick up chicks when I was a teenager. And yes.)
What I'm referring to may be better explained in the pic I've attached. Seemed similar to what people were referring to as resonance, that's all. Not that I know fuck all, I'm no musician.