Too Many Exhaust Options...
Joined: 12-30-07
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From: NEPA
The production SS/SC downpipe is 2.785" O.D. for the most part. It dimples at the rear 02 sensor as your mentioned, and the neck down portion (mating flange of the downpipe) is 2.387" O.D. I measured mine when it was off the car, because I was sick of people on the site saying the downpipe is 2.5".
Last edited by Staged07SS; May 28, 2010 at 01:28 PM.
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Joined: 10-14-07
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From: Austin, TX
Then you are reading them wrong. What I'm trying to explain to people is that a 3" on a stock/mildly modded SS/SC is over kill, and that a 2.5" will be more suitable. A stock/mildly modded SS/SC will not flow enough air to take advantage of the 3" exhaust, and in turn create eddies/backpressure thus decreasing potential power output. I really don't care anymore what people think is best on this site. Everyone always has in their heads that bigger is better without looking at the engineering aspects of flow & velocity. I can guarentee if you took your 3" exhaust off and replaced it with a 2.5" system you wouldn't feel a loss in power even though you are below a "2.9" pulley.
That being said, I may be testing your theory in upcoming months. My 3" keeps hitting my rear strut bar on bumpy roads so I'm thinking about getting a 2.5" catback purely for the sake of clearance. We shall see.
Joined: 12-30-07
Posts: 14,079
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From: NEPA
On a mildly modified LSJ with a stock or stage 1 ring, I agree, however with a 2.7 ring I'm running about 17 lbs of boost. I don't know exactly what the airflow throughput ends up being, but I'm sure it's enough to justify the increased pipe size based on my experience tuning cars and their trap speeds. I talked to plenty of people before I made my decision - I didn't just buy it without doing any research beforehand.
That being said, I may be testing your theory in upcoming months. My 3" keeps hitting my rear strut bar on bumpy roads so I'm thinking about getting a 2.5" catback purely for the sake of clearance. We shall see.
That being said, I may be testing your theory in upcoming months. My 3" keeps hitting my rear strut bar on bumpy roads so I'm thinking about getting a 2.5" catback purely for the sake of clearance. We shall see.
That chart isn't right for all applications, else it is suggesting that the ideal exhaust for our car is 2" (or 2 1/4" if you're looking at 300). I'm pretty sure a blower shifts that graph to the left, if the chart is even correct in the first place - 2 1/2" single pipe supporting 500 WHP? 3" single pipe for 700? Seriously?
But say what you will. Few people are trapping as high as I am without meth/nitrous, TVS/Turbo or cold ambient temps. I did it when it was 90* outside with high humidity. Obviously there's no way to tell if it's due to the exhaust or another factor unless I dyno my car, swap exhausts and dyno it again, but I'm pretty sure you're overestimating the amount of airflow necessary before a 3" shows gains over a 2.5" setup.
But say what you will. Few people are trapping as high as I am without meth/nitrous, TVS/Turbo or cold ambient temps. I did it when it was 90* outside with high humidity. Obviously there's no way to tell if it's due to the exhaust or another factor unless I dyno my car, swap exhausts and dyno it again, but I'm pretty sure you're overestimating the amount of airflow necessary before a 3" shows gains over a 2.5" setup.
A 3" exhaust will take your low end torque and move it out of the power band. Unless your making big power and turning high rpms all the time.
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From: nova scotia
You could also get the "2.5 inch over the axel kit" for 95 bucks and then buy a cheap muffler on ebay. As for header I would suggest going with clearimage. I've been very pleased with my header and the fit and quality.
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From: New Port Richey, Florida
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