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Old 04-01-2004, 03:19 PM   #1
chrhon
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Default Cobb headers - stock catback vs aftermarket

There are a bunch of people (myself included) that are using the new cobb headers and the stock catback for various reasons (quiet, "sleeperness" and money). Though so far all the reviews of this setup are positive I think many of us are wondering how much we are losing out on by using the stock catback.

Has anyone done runs with stock catback and runs with cobb or other aftermarket catback? Basically want to know how much I am missing out by staying stock catback.

Thanks

Chris
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Old 04-01-2004, 05:44 PM   #2
tre36
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I am interested in a setup like this but never really got around to it. Didn't realize there are those out there running aftermarket headers with stock cat-backs.

This is a little off topic but how is the performance difference as compared with completely stock? I got the COBB cat-back but the noise is starting to really get to me because I make a lot of long road trips.
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Old 04-01-2004, 08:04 PM   #3
chrhon
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I noticed a lot more throttle response in the lower rpms with the cobb header addition. I already had the cobb CAI so it wasn't a complete stock to stock+header setup.

The headers do not add much as far as volume of the exhaust which was great for me.

Part of my reason for asking the question is becuase I feel the most gain in the low RPMs... if the stock catback is really restrictive I could be missing out once the exhaust really gets flowing in the high rpms - or else it could just be that since the cobb headers add pretty much the same torque and hp across the whole RPM range that I feel it more in the low RPM becuase the % is greater at that point.

Theoretically equal length headers would make better use of the stock catback than stock headers (exhaust pulses come out of the header spaced evenly with the equal headers while with stock there maybe colisions betweent the pulses)... but then all that is just theory and that is why I hope someone has some real experience.

Since I spent the 700 plus dollars on the headers I want to make sure that the stock catback is not really holding the new headers back any large amount (other than the 5-7hp that I've heard you normally gain by aftermarket catback... tons of extra noise is not worth 5-7 hp to me) .. Now if anyone know of a high quality aftermarket catback that is no noisier than stock but less restrictive than stock ... I am listening - but that is really another topic
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Old 04-02-2004, 01:39 AM   #4
MaxPostal
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How did the new headers affect your gas mileage?
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Old 04-02-2004, 01:42 AM   #5
chrhon
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If you look about 3 or 4 threads down to the gas mileage thread you will see (I would just post it again here but I don't want to get off topic).
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Old 04-02-2004, 08:41 PM   #6
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Your cat is another major bottleneck with your exhaust.

I ran my friend once. He had a lightweight flywheel, Cobb intake, borla header, stock cat, and STI catback. I have a Cobb intake, MRT header-cat-midpipe, and a Stromung muffler. We were neck and neck but I easily passed him in 4th gear, highway runs.
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Old 04-03-2004, 09:59 AM   #7
Section 8
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You either get a new cat with the Cobb or you ask for a catless pipe. THe Cobb header does not terminate in a stock location to allow aftermarket cat, or the stock cat for that matter.

You are missiong out on the high end that the header can give you. Torque and horse power are the same thing. You have Torque and HP curves that streatch the entire rev range of your engine (because HP is a function of torque). The boost in torque off idel and before 4,000 RPM is not as important to acceleration times as from 4,000 to 6,250. Unless you shift your car at 4,000 RPM while accelerating, you are only in that range once, when accelerating from a stop in first gear. So torque gained in the high RPM range is most benificial to acceleration of a vehicle.

THis is where drivability comes in. You do, on occasion, need a good squirt to get out of a prediciment you find your self in with out making an ass out of yourself (like juming one lane to the next from behind a stopped bus). To get up to speed quickly you flat foot the accelerator at 2,000 RPM, and you merge into traffic with out making anyone slow down. This might be important to you not to have to downshift to make the manuver.

WIth a resonably larger exhaust, like a 2.25 inch exhaust, you are not going to loose the low end, and you will gain in the high end. Buy someones WRX, or STi take off mufflers for your car. THey will be quiet, but are capable of a bit more flow. THere are also mufflers that are not loud that flow very well. Concider a mid pipe with a very large resonator put in it.

If you have an automatic, drivability is even more important due to the fact that you have 1 less gear, so you use more of the rev range when accelerating hard, than in a manual.

If you are satisfied with your car the way it is, don't bother with a larger exhaust, the gains with the Cobb header are bleak near redline anyway, compared to the low end gains. You might see a little boost in the midrange, but if you don't see the point in reving the car, then there is no real pressing need for it in the midrange either. THe stock cams have the biggest impact near redline, with out changing them, there is never really going to be much to be gained near redline anyway to add the most to your acceleration.

If 5-7 HP is not worth it, then spend your money somewhere else.

cheeRS,

Greg
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Old 04-03-2004, 10:02 AM   #8
Section 8
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Quote:
Originally posted by MaxPostal
How did the new headers affect your gas mileage?
Your MPG will go up, but it has alot to do with how you drive. If you rip around constantly, its not going to get better.

If you use cruise control on the highway, your highway milage will improve. If you drive on the highway, on and off the gas, I dont' know what it will do for your milage.

cheeRS,

Greg
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