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Old 11-13-2013, 11:18 PM   #113
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Quote:
Originally Posted by BlaqWhole View Post
I know this was addressed towards thahemp, but I feel inclined to comment. I personally can recognize when I don't fully know or understand something. But I also am a creature of passion. Sometimes, I do things solely because I enjoy the thought of it. I understand that I could possibly lose some hp and/or tq by modifying up to a full 3 inch. But for some reason, I just want a full 3 inch system. If I were to definitely lose a significant amount of power, and if that could be undeniably proven, then I would refrain. But the way I see it, there is no significant losses if any losses at all. There are lots of calculations and math to help decide appropriate diameter as we have seen from several members. But sometimes, real world gains vary widely from what you would expect from paper calculations. I feel that a full 3 inch exhaust that eliminates the HF cats will give me a worthwhile boost. And if I'm wrong, then I can always return it to the way it currently sits...no harm done.
Thanks, and appreciate your reply. Its all good, and go for whatcha know and enjoy! BTW, my original post is not based on engine math or engine simulation, it comes from real world results (race only cars using mufflers due to imposed track noise limits). Admittedly not on the Gen5 Camaro platform, but on very similar platforms, meaning V8 engines, headers, mufflers. Biggest gain I ever saw was almost 30 in TQ (28 ft-lb IIRC?). That was a very large cube dragster using a 1/2" neck down at the end of the collectors to create the isolation point or choke point if you will, then into the mufflers. No way a typical Camaro build is going to get anywhere near that much of a gain.

None of this is to be confused with "backpressure". Its mostly about having the proper velocity in the system.
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Old 11-14-2013, 09:59 AM   #114
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Vizard's article shed some cool math. At 630 whp (for rounding sake), I would be fine with a dual 2.8" exhaust by my math. 700whp puts that number to a dual 3". This is given that the collector diameters are proper also...kooks 4-1, pfadt, etc...all fine from what I can see...the 4-1 headers with a merge spike does look beneficial to low end torque band broadening...but that's another topic. Anyway...thanks for the article. I'm sticking with a dual 2.5" for now...it isn't that much of a restriction with no cats and such currently. Once the car gets methanol and 700whp, I'll take it to dual 3".
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Old 11-14-2013, 12:02 PM   #115
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Originally Posted by 14pilot View Post
Unless you have mega-rwhp build, that 2.5" neck down connection point between a 3" header collector and a 3" catback can actually help the engine make more TQ. This works because the collectors are then isolated from the rest of the catback system and it "looks like" an open collector to the engines exhaust gas masses and sonic reflections. So why go to the trouble to cut and weld in a 3" replacement section when you very well would cause TQ to fall off?

No offense meant here, and recognizing that this all may sound counter-intuitive, but if willing to forget what you think you know, and consider that what you don't know, is what you don't know...
None taken. I always value your insights. In a sense you're suggesting that you can have the best of both worlds. A little better velocity near the exhaust ports, but still a very short stretch of narrower piping that isn't much of a restriction at all. For the record, I have a neck down on my 3" and no intention of getting rid of it.

Quote:
Originally Posted by BlaqWhole View Post
I know this was addressed towards thahemp, but I feel inclined to comment. I personally can recognize when I don't fully know or understand something. But I also am a creature of passion. Sometimes, I do things solely because I enjoy the thought of it. I understand that I could possibly lose some hp and/or tq by modifying up to a full 3 inch. But for some reason, I just want a full 3 inch system. If I were to definitely lose a significant amount of power, and if that could be undeniably proven, then I would refrain. But the way I see it, there is no significant losses if any losses at all. There are lots of calculations and math to help decide appropriate diameter as we have seen from several members. But sometimes, real world gains vary widely from what you would expect from paper calculations. I feel that a full 3 inch exhaust that eliminates the HF cats will give me a worthwhile boost. And if I'm wrong, then I can always return it to the way it currently sits...no harm done.
I hear ya buddy. 100% true 3" is definitely not a concern of mine, but we spend most of our lives doing things that make us "feel" better. If people didn't experiment we would never learn anything new. I was just sharing how I would go about it if I were you. $400 is an expensive test if you ask me.
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Old 11-14-2013, 12:36 PM   #116
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Of course it can, but what was left on the table?
Who care's it sounds great and what would you do with more than 1120rwhp on a street car anyway. You can't hook that!
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Old 11-14-2013, 02:52 PM   #117
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Who care's it sounds great and what would you do with more than 1120rwhp on a street car anyway. You can't hook that!
True!
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Old 11-14-2013, 07:09 PM   #118
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Originally Posted by thahemp View Post
None taken. I always value your insights. In a sense you're suggesting that you can have the best of both worlds. A little better velocity near the exhaust ports, but still a very short stretch of narrower piping that isn't much of a restriction at all. For the record, I have a neck down on my 3" and no intention of getting rid of it.



I hear ya buddy. 100% true 3" is definitely not a concern of mine, but we spend most of our lives doing things that make us "feel" better. If people didn't experiment we would never learn anything new. I was just sharing how I would go about it if I were you. $400 is an expensive test if you ask me.
Yea I really don't wanna have to go that route but it will save me the hassle of having to get piping and then find a shop around here that will fab it up (correctly) for me. And then the time it will take while I'm sitting in a shop. And like I said, it will still end costing about the same. This way I can get the exhaust, install the 2 pieces I need in like 5 minutes, and be done with it. And maybe I can sell the rest of it for like $300 along with the 2 pieces (the ones that neck down) I will be removing. That way someone with a stock set-up can buy it and use it. I think getting rid of the cats may be worth something. It made a noticeable difference on my 03 GT. And when I put HF cats back on the GT, it again felt more restricted and sounded muffled. Maybe it was all in my head. Oh well, I'll find out soon enough and report back to you guys... now where is my beer?!
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Old 01-13-2014, 11:56 AM   #119
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I concur the extra weight of a full 3" system cancels out (or loses) power. I know guys with 670" motors on the street and they run 4" systems. BUT...they are pushing over 800HP.

If you're running a serious performance 427" motor, it's appropriate to go with the 3".
If you're running a 376" motor, unless you're using a huffer to get HP numbers of 650+, go with the lighter weight 2.5" system.

I'm not looking for my LS3 Camaro to "sound" bad; I want my Camaro to BE bad AND quiet. t's an old-school street racer thing.
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Old 01-13-2014, 12:37 PM   #120
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I concur the extra weight of a full 3" system cancels out (or loses) power. I know guys with 670" motors on the street and they run 4" systems. BUT...they are pushing over 800HP.

If you're running a serious performance 427" motor, it's appropriate to go with the 3".
If you're running a 376" motor, unless you're using a huffer to get HP numbers of 650+, go with the lighter weight 2.5" system.

I'm not looking for my LS3 Camaro to "sound" bad; I want my Camaro to BE bad AND quiet. t's an old-school street racer thing.
I doubt a 3 inch exhaust will add enough weight over a 2.5 inch exhaust to cancel out the performance gains. And a 6.2 liter engine is a big engine. It isn't a big block, but it is one of the bigger engines available these days. I think that NA or forced induction, a 2.5 inch exhaust will start to struggle in the mid to high 400s hp/tq to the wheels. I'm not saying you can't make 600+ hp/tq with a 2.5 inch exhaust. But I am saying that 3 inch will start making a significant amount more hp/tq to the wheels around the 450 area and only increase from there. Chevy did not put an exhaust on this car that is optimal up to 650 hp. They made it a size that is optimal for its stock output...400-430 hp. Besides, 2.5 inch pipes even look wimpy...
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Old 01-13-2014, 03:23 PM   #121
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Bo you should post up the weather for the two times you dynoed, and how much correction there was. I'd want to see that before making any conclusions.

To Craig's comment about us putting 3" dual exhaust on 500 HP SBC's back in the day, well, sure, but we were trying to help those boat anchor small black Chevy's as much as we could. I ran dual 3" on Chevelles and what not back in the 90's.

I'm guessing the crossover point for 3" exhaust is somewhere in the 600-700 range. I always ran 3" dual exhaust on stuff never 2.5." That said with this 5th gen of mine all the exhaust is 2.5" after the headers.
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Old 01-13-2014, 03:55 PM   #122
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Just updated my ride with a full Kooks 3 inch system. Kind of pissed, there mufflers are to quiet. Will be installing a set of Spintech mufflers this week.
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Old 01-13-2014, 04:19 PM   #123
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Just updated my ride with a full Kooks 3 inch system. Kind of pissed, there mufflers are to quiet. Will be installing a set of Spintech mufflers this week.
Give it time to break in. It will get louder...trust me.
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Old 01-13-2014, 08:14 PM   #124
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Just updated my ride with a full Kooks 3 inch system. Kind of pissed, there mufflers are to quiet. Will be installing a set of Spintech mufflers this week.
If it comes apart at the axle back and u want to sell just that for a good price, I'd be game possibly.
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Old 01-13-2014, 08:52 PM   #125
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If it comes apart at the axle back and u want to sell just that for a good price, I'd be game possibly.
Yes it does come apart right @ the muffler with a clamp. I should have the other mufflers buy the end of the week. So I may sell the kooks.
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Old 01-13-2014, 10:20 PM   #126
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Let me know a price u have in mind and I can say yea or nay.
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