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| shav |
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I have been discussing a possibility regarding my exhaust with someone.
I currently have a 2.5" mandrel bent system (hotdog, straight thru offset muffler, resi), hi flow cat, 4480 headers and was contemplating going to a 3" system as I now have a supercharger fitted. Given that I made the mistake of going a 2.5" prior to fitting the s/c, what mods can I do to the existing exhaust system for better flow as I know the current system is restricting maximum power output.? Would just removing the hotdog and resi be enough for extra flow? OR would a 3" mandrel cat back still fit onto my 2.5" cat and headers and provide the flow that I need?
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| PIMP_LTD |
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What boost do you run? You will end up better off with a 3 inch cat and catback system, and becasue you have the 4480's, you can cut and fit the flange a bit more forward on the collector which will get the flange size to 3 inch.
In the end, a 3 inch with good muffler will out flow 2.5 inch with removed hotdog, and it will also be louder this way (depending on 3 inch's muffler choice of course) so be wary of that aswell. 
_________________ Commodore australia's favorite car??? What a load of s**t |
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| shav |
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PIMP_LTD wrote: What boost do you run? You will end up better off with a 3 inch cat and catback system, and becasue you have the 4480's, you can cut and fit the flange a bit more forward on the collector which will get the flange size to 3 inch. In the end, a 3 inch with good muffler will out flow 2.5 inch with removed hotdog, and it will also be louder this way (depending on 3 inch's muffler choice of course) so be wary of that aswell. Thanks for your input mate. Yeah thats what I was thinking would be the outcome. Im currently running about 8lb now. Theoretically I should be pulling close to 200rwkw but am only pulling 175rwkw. And I beleive the exhaust is the issue. Im also running a CAPA flash tune with a custom tune on it. No doubt I would need to get another custom tune AFTER the exhaust was done to make the changes take affect?
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| PIMP_LTD |
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shav wrote: Im also running a CAPA flash tune with a custom tune on it. No doubt I would need to get another custom tune AFTER the exhaust was done to make the changes take affect? yeah that'll need to be redone. In my last turbo car, i had a similar situation, and once i built a new exhaust and retuned, it made another 30rwhp on the same dyno it got tuned on the first time, and driving it was a big difference.
_________________ Commodore australia's favorite car??? What a load of s**t |
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| shav |
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PIMP_LTD wrote: shav wrote: Im also running a CAPA flash tune with a custom tune on it. No doubt I would need to get another custom tune AFTER the exhaust was done to make the changes take affect? yeah that'll need to be redone. In my last turbo car, i had a similar situation, and once i built a new exhaust and retuned, it made another 30rwhp on the same dyno it got tuned on the first time, and driving it was a big difference. thats a good comparison. Thats pretty much confirmed my suspicions. cheers for ya help
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| KWIKXR |
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Hahaha wouldnt it be awesome if you could just dump the exhaust right after the extractors
 . No need to worry about no cat or no new fancy 3" system lol just the loud grunty roarHows it running with the blower and the 2.5 exhaust at the moment? I reckon it would be better to just go for a 3" system like Pimp said. If you start pulling mufflers/resi's out of the 2.5 system you'll probably still end up having restrictions because of the smallish pipe size now that you have the s.c. Save up for a 3" system, then when you get that fitted sell the 2.5" one and get some of your money back
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| shav |
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KWIKXR wrote: Hahaha wouldnt it be awesome if you could just dump the exhaust right after the extractors . No need to worry about no cat or no new fancy 3" system lol just the loud grunty roarHows it running with the blower and the 2.5 exhaust at the moment? I reckon it would be better to just go for a 3" system like Pimp said. If you start pulling mufflers/resi's out of the 2.5 system you'll probably still end up having restrictions because of the smallish pipe size now that you have the s.c. Save up for a 3" system, then when you get that fitted sell the 2.5" one and get some of your money back Hey mate, thanks for ya comments. What you've suggested is what I plan to do. Currently it works well as is with the 2.5" but it does feel restrictive to some degree over 3000rpm. I know and can feel the s/c has more in it. But I reckon the breathing is letting it down. It would be great to just cruise around with just the extractors and nothing else, but we all know that aint gonna happen. lol So I'm gonna have to save for it regardless. Then get a custom tune afterwards. Also looking at a smaller pulley for more boost too.
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| rushed |
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KWIKXR wrote: Hahaha wouldnt it be awesome if you could just dump the exhaust right after the extractors . No need to worry about no cat or no new fancy 3" system lol just the loud grunty roarhave you heard a falcon i6 open exhaust, they sound very tractorish, not an impressive sound. SHAV, talk to your exhaust shop about getting an off the shelf V8 3" system around $470 (ebay), and cutting it at the y peice and welding in a 3" pipe to your cat, might help you keep the coin down. |
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| shav |
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rushed wrote: KWIKXR wrote: Hahaha wouldnt it be awesome if you could just dump the exhaust right after the extractors . No need to worry about no cat or no new fancy 3" system lol just the loud grunty roarhave you heard a falcon i6 open exhaust, they sound very tractorish, not an impressive sound. SHAV, talk to your exhaust shop about getting an off the shelf V8 3" system around $470 (ebay), and cutting it at the y peice and welding in a 3" pipe to your cat, might help you keep the coin down. Cheers bloke. Might look into that.
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| KWIKXR |
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rushed wrote: KWIKXR wrote: Hahaha wouldnt it be awesome if you could just dump the exhaust right after the extractors . No need to worry about no cat or no new fancy 3" system lol just the loud grunty roarhave you heard a falcon i6 open exhaust, they sound very tractorish, not an impressive sound. Yep, my one .But my extractors have very long secondaries (much like the JMM race series headers) that take the place of the cat so it isnt a short cut off like the 4480's and 4499's etc. Sounds like one of those 6 cylinder saloon cars, drones a bit, but its nice and loud
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