Down pipe only?
- Thread starter OldManSTI
- Start date
Alin
Diehard Car Enthusiast!
You can have an aftermarket downpipe with the stock catback. The stock catback will dtill restrict a good amount. However i may be wrong. Downpipes are generally 3" in diameter and the stock exhaust is 2.5". I would imagine its fine but wait for someone else to chime in as well.
I would definitely get a tune with a downpipe swap. The stock catback is fine with a new downpipe. It is a little more restrictive than an aftermarker catback, but ultimately, the downpipe is the main limiting factor in the exhaust system.
Alin
Diehard Car Enthusiast!
The stock cbe has the massive muffler and a resonator right? The downpipe should alter the loudness. Are you looking to get a catted or catless?
When i bought my car i had an invidia n1 race with a stock downpipe. The cbe changed the pitch and sound. After i put a catless downpipe on it amplified the loudness.
[MENTION=662]Batmobile_Engage[/MENTION] what do you think?
When i bought my car i had an invidia n1 race with a stock downpipe. The cbe changed the pitch and sound. After i put a catless downpipe on it amplified the loudness.
[MENTION=662]Batmobile_Engage[/MENTION] what do you think?
I'm not positive, but I don't seem to remember a resonator in my stock catback when I replaced it about 5 years ago. The muffler is fairly large, but honestly it's very comparable to the muffler on my Cobb catback. Obviously the internals are more imporant than the overall size. The cat in the factory downpipe is quite restrictive and keeps the exhaust note very subdued. Some people feel that a catless downpipe causes an exhaust drone not present in catted (stock or aftermarket) downpipes. While that may be true for some people, I think the muffler is the deciding factor there. You've been in the Batmobile, @Alin. Did you think that was loud, or had any drone? [For reference: Mad Dad UEL header and up pipe, Invidia catless downpipe, Cobb 3" catback]
Originally, when I replaced the stock exhaust, I went with a full Cobb 3" SS (catted) turboback. When I changed out the catted downpipe for the Invidia catless, the volume increased and it became more throaty with a lot more pops and bangs, especially when downshifting/engine braking and coming to a stop.
Originally, when I replaced the stock exhaust, I went with a full Cobb 3" SS (catted) turboback. When I changed out the catted downpipe for the Invidia catless, the volume increased and it became more throaty with a lot more pops and bangs, especially when downshifting/engine braking and coming to a stop.
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I hope I don't ever come off as condescending at times like these. I just can't remember what experience level everyone is at and I'd
hate to have them damage their engine because I wasn't detailed enough in my explanation.
I'm eyeballing a Cobb catted DP. My county doesn't current require emissions testing, but we're so close to the influence of the People's Republic of California I'd probably better keep the cat. I wouldn't mind a change in the tone and volume of the exhaust, just so long as I don't sound anything like a Honda!
I've got a pretty bad 3k stumble. Should I change the fuel regulator and fix the stumble before doing the DP, or could the tune the DP needs also fix the stumble?
@HolyCrapItsFast
@Spamby
@TK-421
I've got a pretty bad 3k stumble. Should I change the fuel regulator and fix the stumble before doing the DP, or could the tune the DP needs also fix the stumble?
@HolyCrapItsFast
@Spamby
@TK-421
Alter3go
New member
Here's the cobb compared to stock!
Also the bellmouth is open on the cobb and the stock has the appearance of a bellmouth but it's more restrictive and its a plate with a smaller opening (that's what she said) then also it tapers to 2.5 before going back to a 3in assuming you have a CBE. So be careful depnding on the exhaust u have may have to get an adapter. Also a tune is a must!!
HolyCrapItsFast
Drinks beer!
The DP probably won't do anything for the stumble and I recommend you get fuel pump if you haven't done that already no matter what. If you don't wish to spend money on hardware, then I suggest trying to tune out the stumble before you attempt replacing the FPR. If we can't smooth it out with tuning then I suggest an after market FPR as well as fuel rails and lines.
I just replaced the FPR and fuel rails on a 2005 legacy that had the stumble issue and it made a night and day difference. Also seeing how other members have gotten along with FPRs and rails and line, I would say it is a good idea either way. It is just a bit expensive but worth the piece of mind.:tup: Also you will have to tune for a new FPR even if it is set to the same pressure as the stock unit. The characteristics and reaction times are different, and that needs to be compensated for.
I just replaced the FPR and fuel rails on a 2005 legacy that had the stumble issue and it made a night and day difference. Also seeing how other members have gotten along with FPRs and rails and line, I would say it is a good idea either way. It is just a bit expensive but worth the piece of mind.:tup: Also you will have to tune for a new FPR even if it is set to the same pressure as the stock unit. The characteristics and reaction times are different, and that needs to be compensated for.
Ok, now I know we're getting a little off topic, but why is it a good idea to get a new fuel pump?
Grinder34
Track Monkey
The stock fuel pump is fairly maxed from the factory. If you start increasing power in any way, it requires more fuel, and the stock pump can't really keep up. IIRC there are some threads about how the IDC has to be pushed above 100% with some mods because the injectors can't flow enough fuel with the stock pump, but adding in the new pump brings the IDC back down to the ~95% range where its more comfortable.
So he should log the injectors duty cycle if it is maxed out he should change the pump? Or get bigger injectors?
Personally, I think that anything beyond an off-the-shelf Stage II tune should be paired with an aftermarket fuel pump; Walbro 255lph or better. Factory injectors are probably okay for a Stage II-ish protune with a fuel pump (unless you plan to run E85 for example).
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