How restrictive are factory mufflers???
08-09-2006, 04:52 AM
#1
Racer
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How restrictive are factory mufflers???
OK, my car failed the dB test by 17dB 
I have no option but to fit a factory 930 muffler.
How restrictive are these, really?
I mean, if I have a good set of aftermarket headers and a quick spooling turbo, would the muffler really make much difference to drivability & power delivery?
I have no option but to fit a factory 930 muffler.
How restrictive are these, really?
I mean, if I have a good set of aftermarket headers and a quick spooling turbo, would the muffler really make much difference to drivability & power delivery?
Last edited by ProtoCab; 08-09-2006 at 05:20 AM.
08-09-2006, 11:32 AM
#4
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Like this:
Yasin
Yasin
08-09-2006, 02:24 PM
#5
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I run a factory 930 Euro muffler on my car with a dump pipe on the waste gate. The stock muffler is retained strictly for the stealth apeal. The engine is only loud when I want it to be (on boost). The car will consistantly run the 1/8th mile in 8.5 seconds @ 90 mph. I can live with that.
You can change a muffler out in less than 30 minutes. Keep the stocker for the noise police and use a free flowing unit for when you just have to have that little extra power.
Where do you live that they have such a restriction?
You can change a muffler out in less than 30 minutes. Keep the stocker for the noise police and use a free flowing unit for when you just have to have that little extra power.
Where do you live that they have such a restriction?
08-09-2006, 03:38 PM
#7
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ProtoCab-
I first had a stock vehicle. quiet, but didn't know any better. then I went with a cat bypass the day after the e-testing (good for 2 years in MA). still quiet yet throatier, a bit quicker spool, insignificant power gain. I since have had my top-end rebuilt, wy/K27-7200, 964 cams, BA&B headers, etc. etc. and FabSpeed single. I find the FabSPeed to be very loud, so I went back to the cat bypass and stock muffler.
sure it's quiet, but there is a significant decrease in the power I just paid dearly for... I haven't Dyno'd after this change (before it was 357 RWHP- 342 TQ), but it's got to be at least a 15hp-tq reduction; it's very noticeable. And, the spooling is noticeably longer. the 'after rebuild' spooling started about 2500 and was full boost by 3000, now it's like 2750 and 3300.
so, I'm looking for the middle ground. in about 2 weeks I'll be installing 3" SS straight pipe onto my turbo flange (like the cat bypass unit but 3" not 2.5") into a "U" bend with a Magnaflow 3" I/O 6" round x 18" (about the same size as the stock muffler) with 3" outlet pipe bent 45o out the stock valance hole. you can run a tennis ball through the entire exhaust system.
I'm expecting with the 3" diameter system and free-flow muffler, the spooling and HP will return, but the 'noise level' will be lower and acceptable. in case the noise is not acceptable, I have a 3" Borla Sportsman bullet I can place in-line where the straight pipe is... that may drop the DBs without sacrifice (still 3" and free-flow).
let you know if this is the trick, or not.
I first had a stock vehicle. quiet, but didn't know any better. then I went with a cat bypass the day after the e-testing (good for 2 years in MA). still quiet yet throatier, a bit quicker spool, insignificant power gain. I since have had my top-end rebuilt, wy/K27-7200, 964 cams, BA&B headers, etc. etc. and FabSpeed single. I find the FabSPeed to be very loud, so I went back to the cat bypass and stock muffler.
sure it's quiet, but there is a significant decrease in the power I just paid dearly for... I haven't Dyno'd after this change (before it was 357 RWHP- 342 TQ), but it's got to be at least a 15hp-tq reduction; it's very noticeable. And, the spooling is noticeably longer. the 'after rebuild' spooling started about 2500 and was full boost by 3000, now it's like 2750 and 3300.
so, I'm looking for the middle ground. in about 2 weeks I'll be installing 3" SS straight pipe onto my turbo flange (like the cat bypass unit but 3" not 2.5") into a "U" bend with a Magnaflow 3" I/O 6" round x 18" (about the same size as the stock muffler) with 3" outlet pipe bent 45o out the stock valance hole. you can run a tennis ball through the entire exhaust system.
I'm expecting with the 3" diameter system and free-flow muffler, the spooling and HP will return, but the 'noise level' will be lower and acceptable. in case the noise is not acceptable, I have a 3" Borla Sportsman bullet I can place in-line where the straight pipe is... that may drop the DBs without sacrifice (still 3" and free-flow).
let you know if this is the trick, or not.
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08-09-2006, 04:15 PM
#8
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When I first put my car together, I had a custom dual exhaust system/ muffler on my car. It was all SS and had a single 3" outlet of each side. Then on a whim, I bought and put on a dump pipe straight off the turbo. Exits in the center of the car, right below the license plate. WOW, what a difference.... build full boost by 2700 RPM, and the flames every once and awhile are cool. It was not loud at all IMHO. Sounds wonderful at speed. Of course, down here in GA...atleast when you are outside of Atlanta....we don't have any of that crazy EPA crap. As long as you are not running open headers...you will be left alone.
08-10-2006, 01:53 AM
#9
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Just got back from having my shiney twin-tip S.S unit replaced with a late model twin-pipe OEM 930 muffler
The car is MUCH quieter than before, even though I can notice a slight decrease in performance
Ah well... I'm still running a crappy J-pipe & Heat Exchanger OEM style setup, but when I fit the Schnell headers with the GT35R, it should revive some performance kick whilst remaining compliant.
I drive my cabrio daily and never track it, so I guess I can live with a 10-15HP hit in perfornance.
RarlyL8, I live in Australia. I think our EPA regulations are much stricter for some reason, OR I just got snitched on by a jealous old F*CKING OFFICER!!!
I've had the aftermarket muffler on there for ~4 years and no-one has said anything about it! Just my luck
The car is MUCH quieter than before, even though I can notice a slight decrease in performance
Ah well... I'm still running a crappy J-pipe & Heat Exchanger OEM style setup, but when I fit the Schnell headers with the GT35R, it should revive some performance kick whilst remaining compliant.
I drive my cabrio daily and never track it, so I guess I can live with a 10-15HP hit in perfornance.
RarlyL8, I live in Australia. I think our EPA regulations are much stricter for some reason, OR I just got snitched on by a jealous old F*CKING OFFICER!!!
I've had the aftermarket muffler on there for ~4 years and no-one has said anything about it! Just my luck
Last edited by ProtoCab; 08-10-2006 at 02:48 AM.
08-10-2006, 01:24 PM
#10
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Gino,
I will be curious to hear your results on your new muffler setup. I also run a Fabspeed and find it a little loud for cruising around town. I haven't decided what to replace it with yet but I know I want a muffler that actually muffles!
I will be curious to hear your results on your new muffler setup. I also run a Fabspeed and find it a little loud for cruising around town. I haven't decided what to replace it with yet but I know I want a muffler that actually muffles!
08-10-2006, 01:45 PM
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I use a standard muffler on my car with a wastegate dump pipe (same as RarelyL8), nice and civil around town and what a sound on boost 
, ProtoCab your going to love the GT35R, mine is fitted with a hybrid version, once you have the headers changed and that turbo on there you wont even think about the 10bhp loss of power, and if you fit a dump pipe you'll have plenty to listen to when you open her up. Are you going to use the standard cam? I don't think I’ve heard of anyone using that turbo as a direct replacement without doing other mods, porting etc
, ProtoCab your going to love the GT35R, mine is fitted with a hybrid version, once you have the headers changed and that turbo on there you wont even think about the 10bhp loss of power, and if you fit a dump pipe you'll have plenty to listen to when you open her up. Are you going to use the standard cam? I don't think I’ve heard of anyone using that turbo as a direct replacement without doing other mods, porting etc
08-10-2006, 08:30 PM
#13
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JBL930, my engine isn't exactly stock standard. It's based on a 3.2 Carrera motor, but runs Motronic EFI, GT2 EVO CAMs, racing turbo valve springs, titanium retainers, ARP fasteners, 930 P&C's, 964 piston squirters, C2T head gaskets, full bay intercooler etc. Basically, all the goodies, except for the exhaust system
Cturbo28, I'm expecting to swap the OEM Carrera heat exchangers, J-pipe & K27HF with the Schnell's and a GT35R within the next month. I CAN'T FREAKIN WAIT!!!
I'm sure the difference in spool-up & power will be amazing, so I'm not fussed if I'm losing a few HP from the OEM muffler. I'm actually enjoying driving a quieter car now. It's pretty stealth
In all honesty, aftermarket free-flowing mufflers for Cabriolets are a bit of an ear sore! Especially after a late night out! You coupe guys don't have that problem due to better sound insulation of the hard top.
Cturbo28, I'm expecting to swap the OEM Carrera heat exchangers, J-pipe & K27HF with the Schnell's and a GT35R within the next month. I CAN'T FREAKIN WAIT!!!
I'm sure the difference in spool-up & power will be amazing, so I'm not fussed if I'm losing a few HP from the OEM muffler. I'm actually enjoying driving a quieter car now. It's pretty stealth
In all honesty, aftermarket free-flowing mufflers for Cabriolets are a bit of an ear sore! Especially after a late night out! You coupe guys don't have that problem due to better sound insulation of the hard top.
08-10-2006, 09:57 PM
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[QUOTE=ProtoCab]JBL930, my engine isn't exactly stock standard. It's based on a 3.2 Carrera motor, but runs Motronic EFI, GT2 EVO CAMs, racing turbo valve springs, titanium retainers, ARP fasteners, 930 P&C's, 964 piston squirters, C2T head gaskets, full bay intercooler etc. Basically, all the goodies, except for the exhaust system
That's the spirit
Changing the factory headers will make more difference than you probably think, add that to the GT35R and your in for some fun, buy shares in your local tire store 
Here is a graph showing my 930 against a standard 930 with a 1bar spring and i'm still on CIS
That's the spirit
Changing the factory headers will make more difference than you probably think, add that to the GT35R and your in for some fun, buy shares in your local tire store Here is a graph showing my 930 against a standard 930 with a 1bar spring and i'm still on CIS
