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Old 07-02-2018, 02:55 PM   #1
zz430camaro

 
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True 3" header connection

Just wondering if there is a big advantage of doing a true 3" connection up by the converters. Most 3" systems start out at 2.5" at the back of the converter and then go to 3". This is so stupid to me because that 2.5" restriction totally defeats the purpose of a 3" system. Was wondering if there is any good dyno data showing a true 3" system test with NO 2.5" restrictions.
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Old 07-02-2018, 05:44 PM   #2
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Or it creates a scavenging effect with increasing the volosity at that point ��
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Old 07-02-2018, 06:36 PM   #3
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Or it creates a scavenging effect with increasing the volosity at that point ��
It very well could, we need test data.
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Old 07-04-2018, 09:52 PM   #4
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Slp kit is 3 in to header.
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Old 07-08-2018, 08:41 AM   #5
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I made some 3" collector extensions to remove the 2.5" section and the initial datalog after the new pipes were fitted showed a difference in fuel trims. My trims we're about 1-2% rich and went to 1-2% lean, some cells a little higher than 2%.

Now before anyone jumps to conclusions, I think it's from sealing exhaust leaks and not the 2.5" section. I had some decent ones in this spot and now the leaks are nearly non existent. I also sealed the connections after the x pipe as well.

I'll log it again sometime next week to see if it goes back to running a little rich. I think it doesn't really matter too much unless you have a bigger cube motor, forced induction, or internal mods. It feels good knowing it's all 3" though lol
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Old 07-08-2018, 02:52 PM   #6
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Originally Posted by xc_SS/RS View Post
I made some 3" collector extensions to remove the 2.5" section and the initial datalog after the new pipes were fitted showed a difference in fuel trims. My trims we're about 1-2% rich and went to 1-2% lean, some cells a little higher than 2%.

Now before anyone jumps to conclusions, I think it's from sealing exhaust leaks and not the 2.5" section. I had some decent ones in this spot and now the leaks are nearly non existent. I also sealed the connections after the x pipe as well.

I'll log it again sometime next week to see if it goes back to running a little rich. I think it doesn't really matter too much unless you have a bigger cube motor, forced induction, or internal mods. It feels good knowing it's all 3" though lol
Does it feel any stronger?
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Old 07-08-2018, 08:12 PM   #7
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Originally Posted by zz430camaro View Post
Does it feel any stronger?
It feels a bit different: the car seems to be able to get off the line better and it feels a little lighter overall. Not sure if it's from the exhaust now being all 3" or from sealing leaks. The pipes I removed were 3", then they went up to 4" to look like cats, and at the end they narrowed to 2.5" so they may have messed with the exhaust pulses/flow.

This was pretty inexpensive too. Maybe $40 bucks and a few hours
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Old 07-11-2018, 08:11 AM   #8
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Quote:
Originally Posted by zz430camaro View Post
Just wondering if there is a big advantage of doing a true 3" connection up by the converters. Most 3" systems start out at 2.5" at the back of the converter and then go to 3". This is so stupid to me because that 2.5" restriction totally defeats the purpose of a 3" system. Was wondering if there is any good dyno data showing a true 3" system test with NO 2.5" restrictions.
I dont have any data for you, but I find it hard to believe that bottle neck isnt costing power. Maybe not much, but some. And the more air your moving, the more it'll hurt you.

I bought TSP 2 inch headers with the dummy cats. Then I went to my exhaust guy and had him weld on 3 bolt flanges to my headers, and pipe it 3inch all the way to a pair of magnaflows. Never used the dummy cats.

I guess it all depends on your plans with the car. If you just plan on bolt ons, you should be fine with the 2.5.

He made it with 4 3 bolt connectors so the mid section can be easily removed. Glad he did, cause I just had to drop the tranny.
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Old 07-11-2018, 07:06 PM   #9
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Nice work, I am sure the restriction will cause a loss of power.
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